74096155 Fundamentals of Reinforced Concrete Design

Solve for .the stress of compression steel Solve for a and c: .·

[Ct="Tt]

0.85fcab=A,,fy a= a= ~1 c c=

. 0.003 ! 's /E . s ---

c-d'

1

c

e's

[s =.600 C ~d' ,

If /s?. fy proceed to step IV If /s < fy, proceed to step V ' . '

'

= f Jf.;

CHAPTER 3 - T-BEAMS AND DOUBLY REINFORCED BEAMS

IV.

fs ~ Jy then use [s =Jy

•

109

(compressibn steel yields)

A's =As2 V. • [s < Jy, then use [s

. A'

=A

.s

(compression .steel will not yield) .

/y

s2 J's

,

.

I

.

j

5fEP5 IN <:OMPUJING Mu OF A ,DOI)BLY REINFORCED BEAM

' WITH GIVEN As, A's, AND OTHER BEAM PROPERTIES

Cz =A's f's ·

d -d'

d- a/2

____L.

1 · Mu I.

II.

=

Mul

Assume compression steel yields if's = fy) · Asz=A's=_._ Asl =As- As2 = __ . Solve fQr a and c: [C1 = T1] 0.85 [ cab= AsJjy

·a= a .= P1 c c= III.

+

Solve for the stres!> in compression steel

r. = 6oo c -a· .. c

If fs

~

Jy, proceed to step IV

Iffs < jy, proceed to st~p V

· REINFORCED CONCRETE DESIGN

110 IV,

Since /s ~ fy, tompressidn _steel yields M,=M,l +M,z _ = $ T1 (d- a/2) + $ h(d- d') . M, = +Ast/r,(d- a/2) + A,2jy(d- d').

+

V.

If fs < fy, assumption is wrong, compression steel does ll;Ot yield .

.c-·a·

fs=900-.- · - ' c

From the stress diagram: [Cl + c2 = T] 0.85 /r ab +A',fs = Adv - . , ' c-d' . . 0~85 /c Jl1 C b +As 600-- = Asfv c . Solvefor cby quadraticformula.

.

c-d'

Solve for f" fs == 600-- = -- - . __ . c . . Solve for a, a = P1 c =- . _ . Solve for M,: M,=M,n+M,.z = $ C1 (d- at2.) + $ C2(d - ,d') M, = 0.85 f, ab (d - -il/2) + A',fs (d- d')

+

+

~-

CHAPTER 3- T-BEAMS AND DOUBLY REINFORCED BI;AMS

111

DEEP BEAMS

According to section 5.10.7.1 of the Code, beams with overall depth to clear span ratios greater than2/5 for continuous spans, or 4/5 for simple spans, shall be. designed as deep flexural m~mbel's taking into account nonlinear distribution of strain and lateral buckling. Beams with web depth that exceed 900 :rruh have a tendency to develop excessive wide cracks in the upper parts of their tension zones: According to Section 5.10~6.7 of NCSP, if the depth of a web exceeds 900 mm,longitudinal skin reinforcement shall be .uniformly distributed along both side faces of the member for a distance d/2 nearest the flexural tension reinforcement. The area of skin reinforcement Ask per meter of height on each side face shall be Ask·~

1.016 (d- 750)

Eq. 3-6

The maximum spacing of the skin reinforcement shall not exceed the lesser of d/ b and 300 mm. . Such reinforcement may be include~ in strength computations if a strain cpmpatibility analysis is made t~ determine stresses in the individual bars or wires. The total area of longitudinal skin reinforcement in both faces need not exceed one-half of the required flexural tensile reinforcement.

REINFORCED CONCRETE DESIGN

112

ILLUSTRATIVE PROBLEMS

Problem 3.8 Design a rectangular beam to carry a factored moment of 272 kN-m. The beam width is b = 250 mm and its .effective depth is d = 400 mm. Usefy = 344.7 MPa andfc = 20.7 MPa. Used'= 60 mm. ' Solution

Solve for [Pmax

Prnax

and M, max

= 0.75 Pb]

=0 75 Pmax .

• .

0.85/'~ ~1(600) /y (600 + /y)

. =0.75 0.85(20.7)(0.85)(600) 344.7(600 + ~44.7) Pmax

·[ro

=0.0207 ,; p

= p /y] 0)

0)

J'c 0.0207(344.7) = __

.....;_~-'-

20.7 = 0.3447

[M, max ,; 41 /'c robd2 (1 - 0.59ro )]

M, m:x =0.90(20.7)(0.3447)(250.){400)2[1 - 0.59{0.3447)] = 204,629,928 N-mm M, max =' 204.63 kN-m < M,

Since M, > M, maXI compression reinforcement is necessary

T1

=

= As1 fv • Mul

+

CHAPTER 3- T-BEAMS AND DOUBLY REINFORCED BEAMS

Solve for As1: Asr= Pmax bd = 0.0207(250)(400) . Asr = 2070 mm2 Solve for Mut and M,z: Mul =Mumax M,r = 204.63 kN-m

M,z=M,.-M,r == 272-204.63 M,.2 = 67.37 kN-m

Check if compression steel yields: Solve for a and c:

[Cr

=Tr]

=

0.85lca b Asr/Y • 1 0.85(20.7)a(250) = 2070(344.7) a= 162.21 mm

[a= ~t c] 162.21 =0.85c c=191mm

c-d' Is= 600-c

See :Eq. 3-4

=600 191-60 191 Is= 412 MPa >fy

Therefore compression steel yields. and use A '• =As2

= 0 Tz (d - d') M,z "As2fy (d- d') 67.37 x 106 =0.90 Asz (344.7)(340)

Mu2

=

Asz= 639mm2 Compression steel area, A's = As2 == 639mm2 Tension steel area, As = Ast + A52 = 2,070 + 639 Tension steel area, As= 2,709 mm2

113

.· . . .

114

REINFORCEO CONCRETE OE§IGN

Problem 3. 9

l)esign a rectangular beam to resist a dead . load ~o~ent of 200 kN-m (including its own weight) and a live load. moment of 300 kN-m. The size of the beam is limited to 375 x 600 riun. Steelccrirering (from bar centroid to outermost fiber) is 100 mm for both tension and compression bars. Use f c = 27.5 MPa arid grade 60 steel with fy = 414 MPa. Solution

[Mu=1.4MoL +1.7MLL] ' M11 ~ 1.4(200) +1.7(300) M"=790kN-m

•

Solve for M,; max: [Pmax =0.7;;pb] Pmax~ 0.75 0.85J'c pl (600) /y(600+ !y) = 0.75 0.85(27.5)(0.85)(600) . . 414(600+ 414) Pm;x= O.Q21

[ro = p /y . f'c (l)

(l)

]

0.021(414) = ,.....----''--..:.. 27.5 = 0.316

[Ru =fc ro (1- 0.59ro)J R11 =27.5(0.316)[1 - 0.59(0.316)] R,, = 7.07 MPa

. b=375mm d = 600 .;..100 d ·;= 500 rruil

'.

Mu ni.x =0.90(7.07){375)(500)2 = 596~531;250 N-mm

Mil max =.596.53. kN-ri\ < M11

· Since Mu > [v1,. max, compression reinforcement is necessary . ..

us

CHAPTER 3- T-BEAIII!S AND DOUBLY REINFORC!=D BEAMS .

Tz = .A.z fy Mul

A.= Ast +As2

A~1= Pma~ bd ,;, 0.021(375)(500) A,, = 3,938 mm2 Solving fot A,2:·. [M,,l = M, max] · M,1 = 596.53 kN-m

[M,2 = M,- M,t] M,.2 = 790 - 596.53 ,Ma = 193.47 kN-m · [M,2 = 0 ;T2 (d - d')] . . · Mu2 = 0 As2fy (d- d') 193.47 x 106 = 0.90 As2 {414}(500 -100} Asl = 1,298 mm2 · · Tension steel area, A, = As1 +As2 A, = 3,938 + 1,298 As = 5,236 mm2 Compression steel: Solving for a and c: [C1 = T1] 0.85 fc a b = Astfy .0.85(27.5)(a)(375,) =3}J38(414) a=186mm ·

[a=

P1 c] 186 .= 0.85c c= 219mm

+

REINFORCED CONCRETE DESIGN

116 Solve for [s:

c-d' c

[.=600-·-

f s= [s

600 219-100 219 326 MPa < .fy

~

I;,

=

, Therefore, compression ~teel will not yield. '

[C2 = T2] 1 A 'sf s= As2.fy A '·s (326} = 1298 (414);

Compression steel area, A\ = 1,648 mm2

Problem 3.10 Deterntine the permissible ul~ate moment capacitY of the ~am shown in Figure 3.8, where[c =20.7 MPa and .fy = 345 MPa.

Figure 3.8

Solution

' A. = t (36)2 X 4, As = 4,072 mm2 A'. =.·t (28)2 X 2 A',= 1,232 mm2

·.~

. CHAPTER 3- T-BEAMS AND DOUBLY REINFORCED BEAMS

117

Assume compression steel yields (f, =fy) As2 = A', = 1,232 mm2 ' Ast = As - Asz = 4,072 - 1,232 ~st = 2,840 mq\~

= Tt]

(Ct

0.85f. ab = Asth 0.85(20.7) a (350) = 2840(345) a= 159mm ·

[a=

Pt cf 159 = 0.85c c= 187mm

Verify if assumption is co,rrect using Eq. 3 "4:

[s = 600 c-d~ c =600 187-60 187 . f;= 107 MPa > fy (Compression ~te~l yields. Assumption correct) ·

IT 0

a

~ L

d-d'

L =

+

Mu2

Mu =.Mut + fyf112 = $ Tt (d- a/2) + $ T2 (d- d') = $A 8 fy (d- aj2) + $Aszfy (d ~ d') =0.90(2,840)(345)(600 -159/2) + 0.90(1,232)(345)(600-: 60)

=665,556,750

N~mm

M,. = 665.56 kN-m

REINFORCED

118

CONCRE~

DESIGN

Problem 3.11

Determine the permissible flexural capacity of the T-beam shown in Figure. 3.9 whose fli;lnge is in tension. Use fy.: 345 MPa andfc ;_ 20.7 MPa.

,..

SOO'·mm 5-32 nim 600 mm

· Figure 3.9

Solution As = { (32)2 X 5 . As = 4,021 mm2 A's f (28)2 x'2

=

A's = 12~2 mm2 Assume compression steel yields, ifs =fy) As2 = A's.=1,232 mm2

A =Asl + As2 = 4,021 - 1,232 As1 = 2,789 mm2 '

.

[C1

. . .

=T1]'

0.85 f, ab = As1jy 0.85(20.7) a (200).= 2,789(345) a= 273 mri1

c =a/~1

=

c 273/0.85 . c= 321 mm

Solve'for the stress of ccm1pression steel, Is: Is = 600 C- d' . .

c

Is

=.600 321-70 321 = 469 MPa > f¥ (yielq,assumption correct)

·

CHAPTER 3- T-BEAMS AND DOUBLY REINFORCED BEAMS

119

Mu=M .. t +M..2 = cP Tt (d- a/2) + cP T2 (d- d') = cP Astfy (d- a/2) + cP As2fy (d- d') = 0.90(2,789)(345)(500- 273/2) + 0.90(1,232)(345)(430) .= 479,275,846 N-m M .. = 479.28 kN-m

Problem 3. 12

Determine the permissible ultimate moment capacity of the beam shown in 3.10. Use fy = 345 MPa and f, = 27.5 MPa.

~igure

A's = 775 mm 2

Figure 3.10

As= 3625 mm 2

Solution Assume compression steel yields: (j' s =fy and As2 =A's) As2=A's = 775 mm2 Ast =As-

As2

3265 - 775 Ast = 2,490 Inm2

A st =

[Ct

= Tt] 0.85 [cab= Astfy 0.85(27.5)a(350) = 2490(345)

a=105mm c = af~t c = 105/0.85 c= 123.5mm

REINFORCED CONCRETE DESIGN

120

Check if compression steel yields:

f, = 600 c -d' c

f = 600 123.5- 63 •

123.5

f, = 294 MPa
r,

63

lc2 =A', f, C, =

j

----.,--

o.asr, ab

g 537

1.0

600- a/2

0

j

-----+-_,_.._.1

~---------------·

f, = 600 c-d' '

[s

=:

c 600 C - 63

c From the stress diagram: [T = C, + C2] A,fy,= 0.85fca b + A',f, a == ~,c

a= 0.85c 3265(345)

= 0.85(27.5)(0.85c)(350) + 775 x 600 c- 63 c

162c = c2 + 66.87c- 4213 c2- 95.13c- 4213 = 0

c=

95.13 ± ~,...-(--9-5.1_3_)2---4-(1-)(--4-2-13-) __ ___.!....:..__

__;__

2(1) c == 128 mm

a = 0.85(128) a= 108.8 mrn

__;___;__

_;__

CHAPTER 3- T-BEAMS AND DOUBLY REINFORCED BEAMS

. Stress of compressiOn steel, f

f5

5

128-63 = 600 --

128 (does not yield)

= 304.7 MPa < 345 MPa d-e

Stress of tension steel, fs = 600-c (5 = 600 600-128 ) 128 fs = 2,213 MPa > fy (yield)

M,. = 0 C1 (d- a/2) + 0 C2 (d- d')

M,= 0 0.85fcab (d- a/2) + 0A'5f5 (d- d') M,. = 0.90(0.85)(27.5)(108.8)(350)(600 -108.8/2) + 0.90(775)(304.7)(600- 63) = 551.2 x 1()6 N-mm M,. =551.2 kN-m Let's try to solve for As max:

As max= 0.75 Pb bd + A's(/'5/.fy) A5

= 0.75 0.85(27.5)(0.85)(600) max

345{600 + 345)

As max= 6443.5 > 3265 {OK)

(350){600) + 775{304.7/345) ·

121

122

REINFORCED CONCRETE DESIGN

SUPPLEMENTARY PROBLEMS Problem 3.13

The T-beam shown is to resist a factored moment of 805 kN-m. Design the tension steel requirements assumingfy = 344.8 MPa and f c = 20.7 MPa. 1100 mm

T

lOOmm

700 mm

_j_

Figure 3.11

Problem 3.14

In Problem 3.13, design the beam with M" = 1500 kN-m.

Problem 3.15 Determine the permissible ultimate moment of the T-beam shown. Use fy = 276 MPa and f c = 28 ~Pa. 900 mm 100 mm 450 mm

~

1

= 3985 mm 2 300 mm

123 Problem 3.16 In Problem 3.15, calculate the permissible ultimate moment with A,= 9400 mm2.

Problem 3.17

Design a 300 mm x 500 mm rectangular beam to carry a dead load moment of 80 kN-m (including its own weight) and a live load moment of 90 kN-m. Assume concrete over (measured from bar centroid) to be 70 mm in compression and 80 mm in tension. Use fy = 345 MPa and [ c = 27.6 MPa.

Problem 3.18 Design a 350 mm x 500 mm rectangular beam to resist a factored moment of 630 kN-m. Assume concrete(pver (measured from bar centroid) to be 70 mm in compression and 80 fi¥11 in tension. Use jy = 345 MPa and [ c = 27.6 MPa.

Problem 3.19 (CE Board November 2001)

A reinforced concrete rectangular beam has a width of 300 mm and an effective depth to bottom bars of 450 mm. The beam is reinforced with six 32-mm bottom bars and two 28-mm top bars located 65 mm from the top of the beam. Concrete strength fr = 34.5 MPa and steel strength Jy = 345 MPa. Calculate the ultimate moment capacity of the beam.

Problem 3.20 Calculate the permissible ultimate moment capacity of the beam shown in the figure. Use jy = 415 MPa and [c = 34.5 MPa. 80 r'nm A's

= 1850 mm 2 E E

As= 4820 mm 2

E

E

o

0 ,.._

124

REINFORCED CONCRETE DES191'i

CHAPTER 4- SHEAR AND DIAGONAL TENSION

125

Chapter 4 She~ar and Diagonal Tension GENERAL

Another type of beam failure other than bending is shear failure. Shear failures are very dangerous especially if it happens before flexure failure because they can occur without warning. To avoid shear failure, the Code provides permissible shear values that have larger safety factors compared to bending failure, thus ensuring ductile type of failure.

(a) Shear failure of beam without stirrup or shear reinforcement

(b) Shear failure of beam stirrup or shear reinforcement Figure 4.1: Shear failure in beams

Without stirrup, there is nothing to stop the concrete from splitting due to diagonal tension as in Figure 4.1 (a). Stirrups prevent this occurrence especially if they are closely spaced as in Figure 4.1 (b).

126

REINFORCED CONCRETE DESIGN

TYP~S

OF SHEAR FAILURE

Sheat failures on location of the load applied relative to the nearest reaction, known as the shear span. Shear failure may be (a) diagonal tension failure, (b) shear-compression failure, and (c) splitting or true shear failure. Diagonal Tension Failure Diagonal tension failure usually occur when the shear span is greater than 3d or 4d. Shear span > 2d

p

Shear-Compression Failure Shear-compression failure occurs when the shear span is from d to 2.5d. Shear span

p

Splitting or True Shear Failure Splitting failure occurs when the shear span is less than the effective depth d. Shear span

p

CHAPTER 4- SHEAR AND DIAGONAL TENSION

127

BASIC CODE REQUIREMENTS

The basic Code requirement (Sec. 5.11.1) on shear strength is that the factored shear force V" shall be equal or less than the design shear 0V,, or

._L ___~_________v" ~ where 121

Eq. 4-1

121V11

= 0.85 and VII= Vc + Vs

Eq. 4-2

For a beam with no web reinforcement, the shearing force that causes the first diagonal cracking can be taken as the shear capacity of the beam. For a beam that does contain web reinforcement, the concrete is assumed to carry a constant amount of shear force Vc, and the web reinforcement need only be designed for the shear force V5 in excess of that carried by the concrete, or Eq. 4-3

Vs =VII- Vc

The amount of shear Vc that can be carried by concrete at ultimate is at least equal to the amount of shear that would cause diagonal cracking. The amount of shear provided by the reinforcement Vs is calculated using the truss analogy with a 45° inclination of the diagonal members.

SHEAR STRENGTH PROVIDED BY CONCRETE, Vc FOR NONPRESTRESSING MEMBERS

5.11.3.1 Shear strength V, shall be computed by provisions of Sec. 5.11.3.1.1 through 5.11 .3.1.4, unless a more detailed calculation is made in accordance with Sec. 5.11.3.2. · 5.l1.3.1.1 For members subject to shear and flexure only,

Eq. 4-4

5.11.3.1.2 For members subject to axial compression.

Vc=

Quantity N"

[1+~] 14Ag

[fj';]b,.,d 6

I A 8 shall be expressed in MPa.

Eq. 4-5

128

REINFORCED CONCRETE DESIGN

5.11.3.1.3 For members subject to significant axial · tension, shear reinforcement shall be designed to carry total shear. 5.11.3.1.4 At sections where factored torsional moment T11 exceeds

~rr _v_ J_ '' Exz y 20

'

Eq. 4-6

5~11.3.2 Shear strength V, may be computed by the more detailed calculation of Sec. 5.11.3.2.1 through 5.11 .32.3. 5.11.3.2.1 For members subject to shear and flexure only,

Eq. 4-7

but not greater than 0.3 [f; b... d. Quantity V11 dj M11 shall not be taken greater than 1.0 in computing V, by Eq. 4 - 7, where M,. is factored moment occurring simultaneously with V,. at section considered. 5.11.3.2.2 For members subject to axial compression, Eq. 4 - 7 may be used to compute Vc with M 111 substituted for M11 and V11 dj M11 not then limited to 1.0, where 4h-d Mm=M 11 -N11 - 8

Eq. 4-8

However, Vc shall not be taken greater than

Vc -- 0.3 Vlf' j c b"' d~0.3Nu 1+- . Ag

Eq. 4-9

Quantity N, / A 8 shall .b e expressed in MPa. When Mm as computed by Eq. 4 - 8 is negative, Vc, shall be computed by Eq. 4- 9. ·

CHAPTER 4 -SHEAR AND DIAGONAL TENSION

129

5.11.3.2.3 For members subject to significant axial tension,

Eq. 4 - 10

where N, is negative for tension. Quantity N,j A 8 shall be expressed in MPa. In the foregoing,

J7':

is in MPa and shall not exceed 0.7 MPa except as

provided by Section 5.11.1.2.1, bw is the width of web in mm, d is the effective depth in nun, and Pw ~ As/ bwd.

SHEAR STRENGTH PROVIDED BY REINFORCEMENT

When factored shear force V, exceeds strength q, Vc, shear reinforcement shall be provided to satisfy Eq. 4 - 1 and Eq. 4 - 2. The shear strength provided by the stirrups is given by the following but shall not be taken greater than

i J7':

b"'

d. (a)

When shear reinforcement perpendicular to axis of member is used,

Eq. 4-11

where Av is the area of shear reinforcement within a distance s. Av = 2 Ab for a U stirrup (see Figure 4.2) (b) When inclined stirrups are used as shear reinforcement, (sin a)d Vs = _A vf ___::.y_ _a+ _cos __ _ s

Eq. 4-12

where a is the angle between inclined stirrups and longitudinal axis of member. (c) When shear reinforcement consist of a single bar or a single group of parallel bars, all bent up at the same distance from the support, Eq. 4-13

130

REINFORCED CONCRETE DESIGN

Derivation of Eq. 4 -11:

The shear force to be carried by reinforcement, V, is equal to the total shear resistance of the bars within a distance d. Vs = (Avfy) X n

Av = cross section area each stirrup has crossing the crack n = number of stirrups within a distanced, .

Vs

=

d Avfy -,,then Vs

Av

= !!:._s

/y d

= -----''----

5

s

TYPES OF SHEAR REINFORCEMENT

According to Section 5.11.5.1 of the Code, shear reinforcement may consist of: a) stirrups perpendicular to axis of member, and b) welded wire fabric with wires located perpendicular to axis of member. For nonprestressed members, shear reinforcement may also consist of: a) stirrups inaking an angle of 45° or more with longitudinal tension reinforcement, b) longitudinal reinforcement with bent portion making an angle of 30° or more with the longitudinal tension reinforcement, c) combinations of stirrups and bentlongitudinal reinforcement, and d) spirals.

DESIGN YIELD STRENGTH OF STIRRUPS

According the Section 5.11.5.2. the design yield strength of shear reinforcement shall n0t'exceed 415 MPa. Stirrups and other bars or wires used as shear reinforcement shall extend to a distance d from extreme compression fiber and shall be anchored at both ends to develop the design yield strength of reinforcement.

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

(a) A.= 2Ab

(b) A, = 2Ab

131

(c) Av = 4Ab

(d) A.= 2Ab Figure 4.2: Types of stirrups

SPACING UMITS OF SHEAR REINFORCEMENT, s According to Section 5.11.5.4 of the Code, the spacings of shear reinforcement placed perpendicular to axis of members shall not exceed d/2 in nonprestressed members and (3/4)h in prestressed members, nor 600 mm. Inclined stirrups and bent longitudinal reinforcement shall be so spaced that every 45° line, extending toward the reaction from middepth of member d/2 to longitudinal tension reinforcement, shall be crossed by at least one line of shear reinforcement When V, exceed

t .[1'; bw d maximum spacing given by the above limits shall

be reduced by one-half.

MINIMUM SHEAR REINFORCEMENT According to Section 5.11.5.5 of the Code, a mmnnum area of shear reinforcement shall be provided in all reinforced concrete flexural members (prestressed and nonprestressed) where factored shear force V;, exceeds one-half the shear strength provided by concrete cp V., , except: (a) Slabs and footings (b) Concrete joist construction defined by Sec. 5.8.11 (c) Beams with total depth not greater than 250 mm, 2-% times thickness of flange, or V2 the width of web, whichever is greatest.

132

REINFORCED CONCRETE DESIGN

This minimum shear reinforcement requirement may not be required if shown by test that required nominal flexural and shear strengths can be developed when shear reinforcement is omitted. Such tests shall simulate effects of different settlement, creep, shrinkage, and temperature change, based on a realistic assessment of such effects occurring in serv1ce. Where shear reinforcement is required, the minimum area of shear reinforcement shall be computed by . Eq. 4-14

where bw and s are in millimeters.

·cRITICAL SECTION FOR _BEAM SHEAR According to section 5.11.1.3 of NSCP, the maximum factored shear force V,. at supports may be computed in accordance with the following conditions provided that:

.

(a) the support reaction, in direction of the applied shear, introduces compression into the end regions of member, and

(b) no concentrated load occurs between the face of the support and the location of the critical section. 1.

For m;m-presp-essed members, sections located less then a distanced from . face of support may be designed for the same shear .v, as that computed at a distance d. · ·

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

2.

133

For prestressed member, sections located less than a distance h/2 from face of support may be designed for the same shear V, as that computed at a distance h/2.

STEPS IN VERTICAL STIRRUP DESIGN I.

Calculate the factored shear force V, at critical sections defined in Page 132, or at any section you want the spacing to be determined.

II. Calculate the shear strength provided by concrete, Vc. Vc = ..[1': bw d (or using Eq. 4 -7)

t

+

If Vu > Vc, stirrups are necessary, proceed to Set IV.. If V, < Vc but V, > 1f2 Vc, proceed to step VI

+ + If V, < 1f2 +Vc, stirrups are not needed

~Iff·

(Sec. 5.11.5.5.1)

Calculate the shear strength v. to be provided by the stirrup. 1. Vn=Vu/tP r ·· 2. V. = V.- Vc = V,J+- Vc If v. ~ f .Jf; bwd, proceed to Step V (Sect. 5.11.5.6.8) If v. >

f .Jf; bwd, adjust the size of the beam .. .

-----~· -----·--· · ~-····· ..

(• /;I

;..

,

"

I

·'

(\ '

·- -~

'

(Sect. 5.11.5.6.8) .'

·/11 I

V. Spacing of stirrups: Spacing, s = Av

/y d; See Figure 4,2 in Page131 for the value of Av.

vs

If s < 25 mm, increase the value of Av by either using a bigger bar size or adding more shear area.

134

REINFORCED CONCRETE DESIGN

Maximum spacing, s:

t fj'; bw d, When V. > t fj'; bw d,

(a) When Vs ~ (b)

Smax Smax

= d/2 or 600 mm

= dj 4 or 300 mm

VI. If Vu < $Vc but Vu > V2 $Vc: . . . Av = bws area of stirrup, (Sect. 5.11.5.5.3) M 1mmum 3/y where s = d/2 or 600 mm (whichever is smaller)

131

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

ILLUSTRATIVE PROBLEMS PROBLEM4.1

Determine the minimum cross section required for a rectangular beam from a she&r standpoint so that no web reinforcement is required by the Code if V, = 168 kN and f c = 27.6 MPa. Use Vc = fj'; bd. Assumed= 1.75b.

t

SOLUTION V,= 168kN

t

Vc = .J27.6 bw d Vc = 0.8756 bd (N)

q, Vc = 0.85(0.8756 bd) q, Vc = 0.74426 bd According to Section 5.11.5.5, shear reinforcement is necessary · only if V,f cjl > 112 Vo then V, = lf2
(

~, ..,~, - .

PROBLEM 4.2 (CE BOARD)

A reinforced concrete beam pas the following properties: Beam width, b = 320 mm - ·· Effective depth, d = 640 mm ·. Concrete strength,fc= 25 MPa ; ' yeinforci~~teel stren&!_!1~~"400 M..,P~ · If the lacrored shear IcifcEi"' at tne crTffcaTsec;tion is 200,000 N, compute the nominal shear carried by the shear reinforcement according to the ACI Specifications: Hint: Vc = 1/6 times the square root off c times b times d. Use q, = 0.85 ,. l . \

SOLUTION

c·

(r

.

l -; (

The nominal shear capacity of the section is given by: V, = Vc+ Vs Vc = fj'; bu, d

l

136

REINFORCED CONCRETE DESIGN

v, = t .fi5 (320)(640) V, = 170,667 N

vu v,.-- -.-.

vr1

v =

\!C

$

200,000 0.85 VII= 235,294 N 11

then,

235,294 = 170,667 + Vs Vs = 64,627N V. = 64.627 kN

(tl• c{ . { t h C ,L ·(_t.

l. ·~~ _:- \ c +t ·1' \ /

•; (' .

•

i J

·. ·' t· -- \j' ·. c

i

PROBLEM 4.3 (CE BOARD)

The required stirrup spacing for a 10 mm diamet€r ties in a reinforced concrete beam with effective beam depth of 800 mm to carry the net shear of 83.8 kN, ifJy = 200 MPa, is nearest to: SOLUTION

The required stirrup spacing is given by the formula;s Av = 2 X

t

(10)2

Av = 157.1 mm2

\ '

= Avfyd

vs

I

I / r :· I ·. d. :•· {· · (I ,, ~

t

V. = 83.8 kN V. = 83.~ x 103 f\!(net shear) .s = _15_7.--'1('--20--'0)'--'-:(8:-00~) 83.8x 10 3 s=300mm

};I

Note: We cannot check for maximum spacing because bw is not given.

137

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

PROBLEM4.4

A simply supported reinforced concrete beam with a width b of 230 mm and an effective depth d of 500 mm has a span of 6 m. The beam carries a live load of 18 kN/m and a dead load of 9 kNjm including its own weight. Usi~g 10-mm diameter stirrups, determine the required spacing near the support. Assumefy = 345 MPa andfc = 28 MPa. SOLUTION

According to section 5.11.1.3.1 of NSCP, sections located less than a distance d from the face of support may be designed for the same shear V, as that computed at a distance d.

d

R . . . - - - - - L = 6m ---~ R

[w.. = 1.4DL + 1.7LL] w, = 1.4(9) + 1.7(18) w, = 43.20 kN/m Reaction: R =w,L/2 R = 43.2(6)/2 R= 129.6kN

·· ·· · .·~

V, = 129.6- w ..d

v, = 129.6- 43.2(0.50)

·~

V, = 108kN

[Vr =

t .{1'; bw d ]

(

f

/ . ..., •. ; 11 · /

t

Vc = J28 (230)(500) Vc = 101,420 N Vc =101.42 kN cjl Vc = 0.85(101.42) cjl Vc = 86.207 kN

Since V, > cjl Vc, web reinforcement is necessary.

V,.= Vc+ Vs V,.= V.. jcjl v, = 127.06

v. = 127.0Q- 101.42 Vs

= 25.64 kN

'r~ . (

i •· .

1

Cr I

! •

: : ( ( ""''I C· :~ l

.

qe

REINFORCED CONCRETE DESIGN

Check if the beam size is adequate for the required shear:

i J7': bwd = i .JiB (230)(500) t J7': bw d =405680 N f J7': b,.,d = 405.68 kN > V, (OK) Using vertical U stirrup: Avfyd s=-Vs

Av = 2 X T(10)2 Av = 157.1 s = _15_7._;1('---34---'5)'-'-(5_00....:...) 25640 s= 1,056mm Maximum stirrup spacing (Code requirement 5.11.5.4)

t ffc b,. d ~ t .fiB (230)(500) t J7': b,., d = 202.84 kN Since V, < t J7': bw d, Smax = Smax=

d/2 = 500/2 = 250 mm or 600mm

Therefore; use s = 250 mm

PROBLEM 4.5

A rectangular beam with b = 350 mm and d = 600 mm is provided with 10mm vertical U stirrups withfy = 414 MPa. Assume /c = 20.7 MPa a) Determine the required stirrup spacing for V, = 62 kN. b) Determine the required stirrup spacing for V, = 380 kN. c) Determine the requiTed stirrup spacing for V, = 710 kN. SOLUTION

t .[f; b,..dJ Vc = t J20.7 (350)(600)

[Vc=

V,= 159240N

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

Vc

= 159.24 kN

t Vc = 1/2(0.85)(159.24) t "Vc = 67.677 kN t JTc b.,d = 2 .J20.7 (350)(600) 0

f JTc bwd = 636,961 N f JTc b.,d = 636.961 kN For V,=62kN Since V,. < !0Vc, Stirrups are not needed For V, =380 kN Since V, > 0V0 stirrups are needed

t

Design of stirrups:

[V,.= Vu] $

v

380 0.85 V, =447kN =

11

[Vs= V,- Vc] v. = 447 - 159.24 Vs = 287.76 KN Vs = 287,760 N Avfyd

[s= - - ]

vs

Av = 2 X

f

(10)2

Av = 157.1 s = _157.1( 414)(600) 287,760 s= 135.6mm

___:._..;....:_~

Maximum spacing provided by the code:

t JTc bw d = t .J20.7 (350)(600)

t JTc bw d =318,481 N t JTc bu, d = 318.481 kN

139

REINFORCED CONCRETE DESIGN

140 since Vs <

t ..{f;bw d, maximums= d/2 = 600/2 = 300 mm

Therefore; use 10-mm (#3) stirrup at 135 mm o.c. For V, =710 kN Vs= V,- Vc

= Vu

- Vc

cjl

= 710 - 159.24 0.85 Vs = 676.05 kN

!

Since Vs > .[!'; bw d, the beam size is not adequate to carry the shear (Code Section 5.11.5.6.8)

PROBLEM4.6 Design the spacing of a 10~mm U stirrups for the beam shown in Figure 4.3, for which DL = 60 kN/m and LL = 87 kN/m. Usefc = 27.6 MPa andfy = 414 MPa.

f11111111 IIIIIll IIIll! IIIll! IIlUI II!Ill IIIIll II1111 L = 4.4 m

375mm

T E .E

R

t.n

j_ Figure4.3

~

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

141

SOLUtiON w,. = 1.4(60) + 1.7(87) w,. = 231.9 kN/m

R= WuL ~

2

R

R = 231.9(4.4) 2 R=510.18kN V, =

t .[l';bwd t'

v, = ./27.6 (375)(570) V, = 187,158 N Vc = 187.16 kN cjl Vc = 159.086 kN Factored shear near the support:

V,

= R- w,.d

v,. = 510,18- 231.9(0.57)

V,. = 378 kN > cjl Vc

V,.jcp = 378/0.85 V,.j cjl = 444.7 kN V. = V,jcp- V,

v. = 444.7- 187.16

Vs = 257.54 kN Verify if the section is Cilfequate to carry the shear:

t .[l'; bw d = t ./27,6 (375)(570) t jJ'; bw d = 748,634 N > Vs Thus, the section is adequate to carry the shear.

[s

=

Avfyd

v.

]

Av = f (10) 2 X 2 Av= 157inm2 157(414)(570) 257,540 s = 144 mm ·

s = --'----'-'---'-

REINFORCED CONCRETE DESIGN

Maximum spafing: bw d = 374,317 N

t .Jl':

Since Vs <

t .Jl': bw d

= d/2 = 570/2 Smax = 285 nun or 600 nun Smax

Use s = 144 nun o.c. near the supports

510.18 kN

Vu Diagram

Is not needed w/ln

this range

'Xt

-~

510.18-159.1 510.18 Xt = 1.51 m x2 2.2=510.18 -79.5 510.18 x2 = 1.86m

_ _! : , . _ _ _

@

0. 9 m from suppor~: v.. = 510.18- 231.9(0.9) V,. = 301.47 kN > ~ V,

v.= v..N- v, v. = 301.47/0.85 -187.16 v. = 167.5kN

s!:: 157(414)(570) 167,500 s=221nun

143

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

@ 1.2 m from support: v, = 510.18- 231.9(1.2) V, = 231 .9 kN > $Vc

v. = 231.9/0.85-187.16 • V. = 85.66 kN 157( 414)(570) 85,660 S = 433 mm > Sma x (use Smax = 285 mm) s=

---'-~'-----'-

Summary of spacing (symmetrical with the centerline)

Length

Spacing 1 @70mm 7@140 .mm 1@220mm The rest @ 285 mm 1@ 70

7@ 140

70mm 980mm 220mm

1@ 220

Total distance from support 70mm 1050mm 1270mm

@ 285

144

REINFORCED CONCRETE DESIGN

PROBLEM 4.7

Design the spacing of 10-mm U stirrups for the beam shown in Figure 4.4, if fc = 20.7 MPa and fy = 275.8 MPa. The dead load shown includes beam weight. Do not consider movement of load. LL = 200 kN

350mm

Flgure4.4 SOLUTION

R = 1/2[126(6) + 340] R=548kN

t .[l';bwd Vc = t ..J20.7 (350)(635}

Pu

= 1.7(200) =340 kN

Wu

= 1.4(90) = 126 kN/m

Vc=

Vc = i68,529 N Vc =168.53 kN 41 Vc = 0.85(168.53) 41 Vc = ~43.25 kN

Near the support: Vu = 548 .:..126(0.635) Vu =468 kN > 41Vc

R

R

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

Vs"' V,J
t .Jf: bw d"' t J20.7 (350)(635)

t .Jf: bw d"' 674,118 N > Vs (OK) [s =

Avfy d

vs Av =

f

]

{10)2 X 2

Av"' 157mm2 157(275.8)(635) s = ---'----'-'-----'382,060 . s"'72mm Maximum spacing:

t .Jf: bw d = 337,059 N Since Vs >

t .[!'; bw d

Smax =

d/4"' 635/4

Smax

= 158.75 mm or 300 mm

Use s =72 mm o.c. @

0.9 m from support: . v, = 548 -126(0.90) V, = 434;6 kN >
v. =434.6/0.85- 168.53 Vs = 342.76 kN > t .[!'; bw d {Smax"' 158.75) Avfyd s = --"--

v.

s = _15_7(_,_27_5_.8)'-'-(6_35....:...) 342,760 s=80mm @

1.2 m from support: v, = 548 - 126(1.2) V, "' 3%.8 kN >
145

146

REINFORCED CONCRETE DESIGN

Vs = 396.8/0.85- 168.53 Vs = 298.3 kN <

s=

t .[1': bw d

(Smax

= 317.5)

(Smax

= 317.5)

(Smax

= 317.5)

Av /y d

---:.-"--

vs

s = _15_7_,_(2_7_5.-'-8)_,_(6_35-'--) 298,300 s = 92mm @

1.8 m from support: Vu = 548 -126(1.8) VII= 321.2 kN > +Vc

v. = 321 .2/0.85- 168.53 V, = 209.35 kN < t .[1': bw d Avfyd

s = ---=--

vs

157(275.8)(635) s = --'-'---~-'-'----'-209,350 s =131 mm @

2.4 m from support: = 548 - 126(2.4) ·Vu = 245.6 kN > +Vc

v,

= 245.6/0.85- 168.53 Vs = 120,41 kN < .[1': bw d Vs

t

s=

Avfyd

--=-

Vs 157(275.8)(635) s= . 120,410 s=228mm @

3 m from support:

v, = 548 - 126(3) = 170 kN > +Vc

VII

Vs = 170/0.85- 168.53 V 5 = 31.47 kN <

t .[1': bw d .

(Smax

= 317.5)

147

CHAPTER 4 -SHEAR AND DIAGONAL TENSION

Av ___.::__ /y d s=_

vs

s = _15_7_,_(2_7_5.8....:;)_,_(6_35....:..) 31,470 s=873mm Uses =317mm

Summary of spacing (symmetrical with the centerline) Spacing 1@35mm 13@70mm 4@80mm 6@90mm 5@130mm The rest at 225 mm

· Length 35mm 910mm 320mm 540mm 650mm

Total distance from support 100mm 945mm 1265mm 1805mm 2455mm

148

REINFORCED CONCRETE DESIGN

BRACKETS AND CORBELS (SECTION 5.11.9)

Brackets and corbels are members having a ratio of shear span to depth aj d of 1 or less. The shear span a is the distance from the point of load to the face of support.

The depth of a bracket or corbel at its outer edge shall not be less than one-half of the required depth d at the support. Reinforcement shall consist of main tension bars with area As and shear reinforcement of area A 11 • The shear reinforcement shall consist of closed ties parallel to the tension reinforcement. The area of the shear bars shall not be less than 0.5As or more than 1.0As, and shall be uniformly distributed within 2/3 of the depth of the bracket adjacent to the main tension bars. The ratio p =As/ bd shall not be less than 0.04 fcl fi,. At front face of bracket or corbel, primary tension reinforcement A. shall be anchored by one "of the follow,i ng: (a) by a structural weld to a transverse bar of at least equal size; weld to be designed to develop specified yield strength Jy of As bars; (b) by bending primary tension bars As back to form a horizontai loop, or (c) by some other means of positive anchorage.

SHEAR FRICTION DESIGN METHOD (SECTION 5.11.7.4)

When the ratio of aj.d is 0.5 or less, the bracket design may comply with Section 5.11.7.4 of NSCP. With this method, a , failure crack location is assumed. Reinforcementis then provided perpendi~ular to the crack to prevent failure. Due to the rough surface at a crack, friction develops under the tension in the reinforcement anp hol~s together the two sections on opposite sides of the

14f9

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

crack. An equal compression load develops in the concrete at the confined crack. According to Section 5.11.7.5, the shear force at the crack, at the face of the colulll11. or bracket, shall not exceed 0.2 fc Ac nor 5.5 ACJ in Newtons, where Ac is area of concrete section resisting shear transfer. The area of, shear-friction reinforcement Aut required in addition to reinforcement provided is:

Eq. 4-15 where V, is the design shear in Newton, at the section; h is the reinforcement yield strength, but not more than 415 MPa; and J.l, the coefficient of friction given as follows: Concrete placed monolithically .................................. ................. 1.4A. Concrete placed against hardened concrete with surface intentionally roughened as specified in Sec. 5.11.7.9 ......... 1.0/... Concrete placed against hardened concrete not intentionally roughened ......................................................... 0.6A. Concrete anchored to as-rolled structural steel by headed studs or by reinforcing bars (see Sec. 5.11.7.10) .................. 0.7A. where A.= 1.0 for normal weight concrete, 0.85 for "sand-lightweight" concrete and 0.75 for "all light-weight'' concrete. Linear interpolation is permitted when partial sand replacement is used. · The tension reinforcement As should be adequate at the face of the support to resist the moments due to the vertical load and ·any horizontal forces. The reinforcement rriust be properly developed to prevent pull-out, or proper anchorage within the support and by a crossbar welded to the bars at the end of the bracket.

150

REINFORCED CONCRETE DESIGN

DESIGN FOR TORSION {NSCP ClOl-01) Acp

= area enclosed by outside perimeter of concrete cross-section, mm2

A, = total area of longitudinal reinforcement to resist torsion. mm2

Ao = gross area enclosed by shear flow, mm2 A 0 ,, = area enclosed by centerline of the outermost dosed transverse torsional reinforcement, mm2 A 1 = area of one leg of a closed stirrup resisting torsion within a distance s, mm2 fPc= compressive stress in concrete (after allowance for all prestress losses) at centroid of cross-section resisting externally applied loads or at junction of web and flange when the centroid lies within the flange, MPa Jy1 = yield strength of longitudinal torsional reinforcement, MPa fyv = yield strength of closed transverse torsional reinforcement, MPa h = overall thickness of member, mm pep = outside perimeter of the concrete cross-section, mm pt1 = perimeter of centerline of outermost closed transverse torsional reinforcementmm s = spacing of shear or torsion reinforcement in direction parallel to longitudinal reinforcement, mm e = angle of compression diagonals in truss analogy for torsion 411.7.1 It shall be permitted to neglect torsion effects when the factored torsional . moment T, is less than. • 1. For non-prestressed members:

~ff [Aep2) 12

Eq.4-16 .

Pep

2. For prestressed members:

~fj;

[Aep2]

12

Pep

3fpc 1+--

ff

Eq. 4-17

For members cast monolithically with a slab, the overhanging flange wiath used in computing Acp and pep shall conform to Section 413.3.4. ·

CHAPTER 4 - SHEAR AND DIAGONAL TENSION

151

Calculation of F'actored Torsional Moment T u•

411.7.2.1 If the factored torsional moment T, in a member is required to maintain equilibrium and exceeds the minimum value given in Section 411.7.1, the member shall be designed to carry that torsional moment in accoq;l.ance with Sections 411.7.3 through 411.7.6. 411.7.2.2 In a statically indeterminate structure where reduction of the torsional moment in a member can occur due to redistribution of internal forces upon cracking, the maximum factored torsional moment T, shall be permitted to be reduced to 1. For non-prestressed members, at the sections described in Section 411 .7.2.4:

$..{1';

[Aep 2]

3

Pep

Eq. 4-18

2. For prestressed members, at the sections described in Section 411.7.2.5:

$..{1'; [Aep2] .

3

Pep

3fpc 1+--

..{1';

Eq. 4-19

In such a case, the correspondingly redistributed bending moments and shears in the adjoining members shall be used in the design of those members. 411.7.23 Unless determined by a more exact analysis, it shall be p~rmitted to take the torsional loading from a slab as unifor:ffily distributed along the member. 411.7.2.4 In non-prestressed members, sections located less than a distance d from the face of a support shall be designed for not less than the torsion T, computed at a distance d. If a concentrated torque occurs within this distance, the critical section for design shall be at the face of the support. 411.7.2.5 In prestressed members, sections located less than a distance h/2 from the face of a support shall be designed for not less than the torsion T u computed at a distance h/2. .If a concentrated torque occurs within this distance, the critical section for design shall be at the face of the support.

],52

REINFORCED CONCRETE DESIGN

Torsional Moment Strength

411.7.3.1 The cross-sectional dimensions shall be such that:

1. For solid sections:

Eq. 4-20

· 2. For hallow sections:

Eq. 4-21

411.7.3.2 If the wall thickness varies around the perimeter of a hollow section, Eq. 4 - 21 shall be evaluated at the location where the left-hand side of Eq. 4 21 is a maximum. 411.7.3.3 If the wall thickness is less than Ao~,fp11, the second term in Eq. 4- 21 shall be taken as:

Eq. 4-22

I

where tis the thickness of the wall of the hollow section at the location where • are being checked. the stresses 411.7.3.4 Design yield strength of non-prestressed torsion reinforcement shall not exceed 415 MPa. 411.7.3.5 The reinforcement required for torsion shall be determined from: T,s;~T,

Eq. 4-23

411.7.3.6 The transverse reinforcement for torsion shall be designed using:

Eq. 4-24

• CHAPTER 4 - SHEAR AND DIAGONAL TENSION

153

where Ao shall be determined by analysis except that it shall be permitted to take Ao equal to 0. 85Aoll; e shall not be taken smaller than 30 degrees nor larger than 60 degrees. It shall be permitted to take 8 equal to: · 1. 45° for non-prestressed members or members with less p,restress than in Item 2 below, 2. 37.5° for prestressed members with an effective prestress force not less than 40 percent of the tensile strength of the longitudinal reinforcement. 411.7.3.7 The additional longitudinal reinforcement required for torsion shall

not be less than: Eq. 4-25

where 8 shall be the same value used in Eq. 4 - 24 and A 1/ s shall be taken as the amount computed from Eq. 4 - 24 not modified in accordance with Section 411.7.5.2 or 411.7.5.3. 411.7.3.8 Reinforcement required for torsion shall be added to that required for the shear, moment and axial force that act in combination with the torsion. The most restrictive requirements for reinforcement spacing and placement must be met. 411.7.3.9 It shall be permitted to reduce the area of longitudinal torsion

reinforcement in the flexural compression zone by an amount equal to M,.j(0 .9 d fy1), where M,. is the factored moment acting at the section in combination with T,. except that the reinforcement provided shall not be less than that required by Section 411.7.5.3 or 411.7.6.2. In Prestressed Beams: 1. The total longitudinal reinforcement including tendons at each section shall resist the factored bending moment at that section plus an additional concentric longitudinal tensile force equal to A1 fyt, based on the factored torsion at. that section, and 2. The spacing of the longitudinal reinforcement including tendons shall satisfy the requirements in Section 411 .7.6.2. 411.7.3.11 In prestressed beams, it shall be permitted to reduce the area of longitudinal torsional reinforcement on the side of the member in

154

REINFORCED CONCRETE DESIGN

compression due to flexure below that required by Section 411.7.3.10 in accordance with Section 411.7.3.9. Details of Torsional Reinforcement

411.7.4.1 Torsion reinforcement shall consist of longitudinal bars or tendons and one or more of the following: 1. Closed stirrups or closed ties, perpendicular to the axis of the member, or 2. A closed cage of welded wire fabric with transverse wires perpendicular to the axis of the member, or 3. In non-prestressed beams, spiral reinforcement. 411.7.4.2 Transverse torsional reinforcement shall be anchored by one of the following: • 1. A 135-degree standard hook around a longitudinal bar, or 2. According to Section 412.14.2.1, 412.14.2.2 or 412.14.2.3 in regions where the concrete surrounding the anchorage is restrained against spalling by a flange or slab or similar member. 411.7.4.3 Longitudinal torsion reinforcement shall be developed at both ends. 411.7.4.4 For hollow sections in torsion, the distance measured from the centerline of the transverse torsional reinforcement tO" the inside face of the wall of a hollow section shall not be less than 0.5Aoll/ p,,. Minimum Torsion Reinforcement

411.7.5.1 A minimum area of torsion reinforcement shall be provided in all regions where the factored torsional moment 1;, exceeds the values specified in Section 411.7.1. 411.7.5.2 Where torsional reinforcement is required by Section 411.7.5.1, the minimum area of transverse closed stirrups shall be computed by: 1 ,bw S (Au+ 2Ar) = - -

3

Eq.

/yv

4-261

411.7.5.3 Where torsional reinforcement is required by Section 411.7.5.1, the minimum total area of longitudinal torsional reinforcement shall be computed by:

5Jl': Acp A1, min = ___.c __ ~ 12fyt

(~) f yv s

!yt

PIJ

Eq. 4-27

CHAPTER 4 -SHEAR AND DIAGONAL TENSION

where A,j s shall not be taken less than

155

t b..,j/yv·

Spacing of Torsion Reinforcement.

411.7.6.1 The spacing of transverse torsion reinforcement shall not exceed the sma!Fer of p;,/8 or 300 mm. 411.7.6.2 The longitudinal reinforcement required for torsion shall be distributed around the perimeter of the closed stirrups with a maximum spacing of 300 mm. The longitudinal bars or tendons shall be inside the stirrups. There shall be at least one longitudinal bar or tendon in each comer of the stirrups. Bars shall have a diameter at least 1/24 of the stirrup spacing but not less than a 10 mm diameter bar. · 411.7.6.3 Torsion reinforcement shall be provided for a distance of at least (b, + d) beyond the point theoretically required.

Shear failure of beam

156

REINFORCED CONCRETE DESIGN

SUPPLEMENTARY PROBLEMS PROBLEM 4.8

Calculate the required spacing of 10-min U stirrup in a rectangular beam with b = 280 mm and d = 420 mm at a section where V, = 410 kN. Use f c = 28 MPa and fy=345 MPa.

PROBLEM 4.9

Calculate the required spacing of 10-mm U stirrup in a rectangular beam with b = 280 mm and d = 440 mm at a section where V, = 250 kN. Use f , = 20.7 MPa and fY = 276 MPa.

PROBLEM 4.10 A rectangular beam with b = 270 mm and d = 510 mm is provided with 10-mm

vertical U stirrups withfy = 276 MPa. Assumefr = 22 MPa a) Determine the required stirrup spacing for V, = 45 kN b) Determine the required stirrup spacing for V, = 95 kN c) Determine the required stirrup spacing for V, = 247 .kN d) Determine the required stirrup spacing for V, = 480 kN

PROBLEM 4.11

Select the stirrup spacing for the T-beam beam shown. The beam is simply supported over a span of 6 m and carries a uniform dead load of 60 kN/m (including its own weight) and live load of 100 kN/m. Use 10-mm U stirrups and assumef, = 20.7 MPa andfy = 275.8 MPa 1400 mm

T

157

CHAPTER 5- BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

Chapter 5 Development Length, Hooks, and Splicing of Reinforcement Bon~d,

BOND

In reinforced concrete, we assume that the concrete and steel work as a.unit. For this to happen there must be absolutely no slippage of the bars in relation to the surrounding concrete. The steel .and concrete must stick or bond together for them to act as a unit. If there is slipping of steel with respect to surrounding concrete, there will be no transfer of stress from steel to concrete and vice versa and as a result, the concrete will act as an unreinforced member and will be subject to collapse.

DEVELOPMENT LENGTH

For the cantilever beams shown in Figure 5.1, theoretically the maximum moment occurs in the beam at the face of the support and ·at a small distance from the back ofthe support is zero. Thus, it would seem that reinforcing bars would only be necessary in the beam at the face of the support and a little at the back of the support as in Figure 5.1 (a). Obviously, this beam would easily fall down. (It's like a man playing tug of war holding the tip of the rope. No matter how strong that man and that rope is, it would easily slip off his hand. )

(a) No development length (beam will fall)

(b) With development length

Figure 5.1

'-
158

REINFORCED CONCRETE DESIGN

Figure 5.2: Development of bars in footing

DEVELOPMENT LENGTH OF STRAIGHT BARS

Bar development length Ld is the embedment necessary to assure that the bar can be stressed to its yield point with some reserved to insure member toughness. Development length is a function of bar diameter db, yield point Jy, · and concrete strength fc· Other items affecting the development length are bar spacing, concrete cover, and transverse reinforcement.

BASIC CONCEPT OF DEVELOPMENT LENGTH

In the basic concept of anchorage length, a bar is embedded in a mass of concrete as shown. Under initial loading, the actual bond stress will be larger near the surface and nearly zero at the embedded end. Near failure, the bond stress along the bar will be more uniformly distributed. If the average bond stress at ultimate is u, then

F = ~ fv

F = Foond Ab fy = u X 7t db Ld 1j db2 fy = u x 1t db La

159

CHAPTER 5 - BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

Eq. s -1 According to Section 5.12.1, calculated tension or compression in reinforcement at each ~section of reinforced concrete members shall be developed on each side of that section by embedment length, hook or mechanical device, or a combination thereof. Hooks may be used in developing bars in tension only. The Code provides the basic development length ldb for various situations. The values provided by the code have to be modified for different condition. Thus, the minimum development length Ld required by the code can be expressed as Ld

= ldb x applicable modification factor(s), m

Eq. 5-2

but shall not be less than 300 mm, except for the lengths required for tension lap splices and for the development of shear reinforcing.

BASIC DEVELOPMENT LENGTH OF BARS IN TENSION

According to Section 5.12.2 of the Code, the basic development shall be: For 32 mm bar & smaller and deformed wire:

ldb

=

0.02Ab

ff;

/y

but not less than 0.06 dbfy ·

Eq. 5-3

For 36 mm bar: Eq. 5-4

For deformed wire Eq. 5-5

1

160

REINFORCED CONCRETE DESIGN

MODIFICATION FACTORS FOR BARS IN TENSION Basic development length ldb shall be multiplied by the applicable modification factors m for the following conditions: Condition

Modification Factor, m

(a) For bars in beams or columns with a minimum 1.0 cover not less than specified the Code: (b) Bars in beams or columns with transverse 1.0 reinforcement satisfying tie requirements of Code: (c) Bars in beams or columns with clear spacing of not 1.0 less than 3db: (d) Bars in the inner layer of slabs or wall 1.0 reinforcement and with clear spacing of not less than3db: (e) Any bars with cover of not less than 2db and with 1.0 clear spacing of not less than 3db: (j) For bars with cover of db or less or with clear 2.0 spacing of 2db or less: 1.4 (g) For bars not included in items a to f. (h) For 32 mm bars and smaller with clear spacing not less than 5db and with cover from face of member to edge bar, measvred in the plane ofthe bars, not less than 2.5db , the factors in items a to g may be multiplied by 0.8. 1.3 (i) Top reinforcement: 1.3 (j) Lightweight aggregate concrete: (k) Lightweight aggregate whenfi-, is specified:

.JTc I (1.8 fi-,)

(l) For reinforcement enclosed within special reinforcement not less than 6mm diameter and not more than 100 mm pitch, within 12mm or larger circular ties spaced at not more than 100mm on center or within 12 mm or larger ties or stirrups spaced not more than 100 mm on center and arranged such that alternate bars shall have support provided by the corner of a tie hoop with an included angle of not more than 135°, the factors in items a through g may be multiplied by 1.8. (m) Excess Reinforcement. Development length may be As required reduced where reinforcement in a flexural member As provided is more than that required by analysis by a factor:

161

CHAPTER 5 - BOND, DEVELOPMENT LENGfH, HOOKS, AND SPLICES

BASIC DEVELOPMENT OF BARS IN COMPRESSION

According to Section 5.12.3.2 of the Code, the basic development for bars in. compression shall be: ldb

=

0.24db !y

Jf:

Eq. 5-6

but not less than 0.04 db,[y

MODtFICATION FACTORS FOR BARS IN COMPRESSION

Basic development length ldb may be multiplied by applicable factors for: Condition (a) Excess Reinforcement. Reinforcement IIJ.Ore than

that required by analysis (b) Spirals and Ties. Reinforcement enclosed within spiral reinforcement not less than 6mm diameter and not more than 100 mm pitch or within 10 mm ties and spaced at not more than 100 mm on center

Modification Factor, m A 5 required A 5 provided 0.75

DEVELOPMENT OF BUNDLED BARS

Development length of individual bars within a bundled, in tensio~ or compression, shall be that for the individual bar, increased 20 percent for threebar bundle, and 33 percent for four-bar bundle. For determining the appropriate modification factors, a unit of bundled bars shall be treated as a single bar of a diameter derived from the equivalent total area.

DEVELOPMENT OF FLEXURAL REINFORCEMENT (SEC. 5.12.10)

Tension reinforcement in flexural members may be developed by: a) bending across the web to be anchored or

b) made continues with reinforcement on the opposite face of member. Critical sections for development of reinforcement in flexural members are at points of maximum stress and at points within the span where adjacent reinfor~ement terminates, or is bent. Reinforcement shall extend beyond the point at which it is no longer required to resist flexure for a distance equal to the

162

REINFORCED CONCRETE DESIGN

effective depth of member or 12db, whichever is greater, except at supports of simple spans and at free end of cantilevers. Continuing reinforcement shall have an embedment length not less than the development length ld beyond the point where bent or terminated tension reinforcement is no longer required to resist flexure. Flexural reinforcement shall not be terminated in a tension zone unless one of the following conditions is satisfied: a) Shear at the cutoff point does not exceed two-thirds that permitted including shear strength of shear reinforcement provided. b) Stirrup area in excess of that required for shear and torsion is provided along each terminated bar or wire over a distance from the termination point equal to the three-fourths the effective depth of member. Excess stirrup area Av shall be not less than 0.4 bw sjfy· Spacing s shall not exceed d/BI3b where pb is the ratio of area of reinforceme~t cut off to total area of tension reinforcement at the section. c) For 32-rnrn bar and smaller, continuing reinforcement provides double the area required for flexure at the cutoff point and shear does not exceed three-fourths that permitted. Adequate anchorage shall be provided for tension reinforcement in flexural members where reinforcement stress is not directly proportional to moment, such as: sloped, stepped, or tapered footings; brackets; deep flexural members; or members in which tension reinforcement is not parallel to compression face.

DEVELOPMENT OF POSITIVE MOMENT BARS

According to Section 5.12.11 of the Code, at least one-third the positive moment reinforcement in simple members and one-fourth the positive moment reinforcement in continuous members shall extend along the same face of ·member into the support. In beams, such reinforcement shall extend into the support at least 150 rnrn .. At simple supports and at points of inflection, positive moment tension reinforcement shall be limited to a diameter such that Ld computed by Eq. 5-2 need not exceed Eq. 5-7. The purpose of this limitation is to keep bond stress~s within reason at the,se points of low moments and large shears.

M"+ a1 Ld::; Eq.5-7 • ~·--_____________________v_u______________________~

I

163

CHAPTER 5 - BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

where: Mn is nominal moment strength assur:ting all reinforcement at the section to be stressed to the specified yield strength Jy. V, is factored shear force at the section {at point of support for simple . $Upport and at point of inflection for continuous beam) at a support shall be embedment length beyond center of support.

z. z.

at a point of inflection shall be limited to the effective depth of member or 12db, whichever is greater.

Value of MnfV, may be increased 30 percent when the ends of reinforcement are confined by a.compressive reaction, such as where there is a column below but not when a bea:m frames into a girder. i.e. Eq.

5-81

When Ld computed by Eq. 5 - 2 exceed Eq. 5 - 7 or Eq. 5 - 8, use a smaller bar size, or increase the value of end anchorage as by the use of hooks.

z.

Mn

= ~ fv (d -a/2)

a = ~ fv/(0.85 fc b) Vu

Figure 5.3: Development length for positive moment on simply supported beam

164

REINFORCED CONCRETE DESIGN I, is the larger value of d or 12db

Max L.t Ia

Mn/Vu

Moment Diagram

Mn = A. fv (d - a/2) a = A. fy/(0.85 f, b) Figure 5.4: Development length for positive moment

on continuous beam

DEVELOPMENT Of NEGAnYE MOMENT REINFORCEMENT

Negative-moment reinforcement should have an embedment length into the span to develop the calculated tension in the bar, or a length equal to the effective depth of the member, or 12db, whichever is greatest. At least_one-third of the total negative reinforcement should have an embedment length beyond the point of inflection not less than the effective depth of the member, or 12db, or 1/16 of the clear span, whichever is greatest.

CHAPTER 5 - BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

Ln

= clear span

Moment diagram

Figure 5.5: Development length for negative moment

ln2

Figure 5.6: Recommended bar details for continuous beams

165

166

REINFORCED CONCRETE DESIGN

HOOKS

If sufficient space is not available to anchor tension bars by running them straight for the required development length as required by the Code, hooks maybe used. ,. 12

~

i

Bend diameter, D = 2r: D = 6 db for 10 mm through 25 mm bars D = 8 db for28 mm through 32 mm bars D = 10 db for 36 mm bar

(a) 90° hook

(b) 180° hook Figure 5.7: Standard hooks

'

I I

r

Critical section

4 db for lOmm through 25 mm bar 14--...-.--+15 d~ for 28mm through 32 mm bar 4db 6 db for 36 mm bar

I

(65 mm min.)

lcsb Figure 5.8: Hooked-bar detail for development of standard hook

Cl-tAPTER 5- BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES ,

DEV.ELOPMENT OF STANDARD HOOKS

16Z

-

According to Section S.12.5, .the basic development length l11bfor standat:d hooks with Jy;,. 41.5 MPa is equal to 100dbj

J1': ..·

.

.

The achlal developine.nt length ld11 is taken as the basic development length hh multiplied by applicable modification factors, but ld" shall not qe Jess than Bdb nor less than 150 mm. "' Modification .factors (Sect. 5.12.5.3)

. 1.

If the reinforcing bar has anjy otl1er than 415 MPa,l1,b is to be multiplied . by_{y/415. (Sec. 5.12.5.3.1) >

•

•

2.

When 90°.hooksand 32~ or smaller bars are used and when 60 mm or more of side cover normal to the hook is present, together with at least 50 mm cover for the bar extension, Z,.b is to be multiplied by 0.70. (Sec. 5,12.5.3.2)

3.

When hooks made of 32 mmor smaller bars are enclosed vertically and horiz6ntally within ties or stirrup ties spaced no farther apart than 3db, ·hb is to ,be multiplied by0.80. (Sec. 5,12.5.3.3) · ·

4.

Where the amount of flexural . reinforcement exceeds the theoretical . amount required and where the ~pecifications being used do not specifically require that development lengths be based .on Jy the value of )hb may be multiplie(i by (A; required)/ (As -provided}. (Sec. 5.12.5.3.4)

5.

W:hen lightweight concrete are used, a modification factor of 1.3. ~ust be applied. (Sec. 5.12.5.3.5) · . .. • .

6.

For bars being developed by standard hook at discon!lnuous ends of members with both side cover .a nd top (or bottom) cover over' hook less than: 60 mm, hooked bar shall be enclosed within ties or stirrup ties spaced,along the full d(;!velopment length Idl, not greater than 3db where db . is the diameter of hooked bar. For this case, the factor mentioned in item · 3 shali not apply. (Sec..5.12.5~4) · . ·

-

''

-·

'

\

SPUCES OF REINFORCEMENT, GENERAL It is generally necessary to splice bars, partly because of the limited length of the commercialbars but more because bf the <,iiffisulty of interweaving long bar~ on the job. Splicing may be done by welding, by mechanical connections, OI' most

frequently by lapping bars. Lapped bars are_usually tied in contact ..

168

REINFORCED CONCRETE DESIGN

Lap Splices

.,

Lap splices shall riot be used for bars larger than 32 mm except as provided by :~ the Code. Bars spliced by non-contact lap splices in flexural members shall not -~ be spaced transversely farther apart than 1/5 the required lap splice length, nor .;; 150mm. · . A

..

··-~

. ·~ f Welded Splices and Mechanical Connections i' Welded splices and other mechanical connections are perrn.jtted by the Code. A --~ full welded splices shall have bars butted and welde(i to develop iri tension at -~ least 125 percent of specified yield strength fy of the bar. A full mechanical ' ':d connections shall develop in tension or co~pression, as required at least 125 _ percen~_of specified yield strength fy of the bar. -

.j

Splices in Tension The minimum length of lap for tension lap splices shall be as required for Class . A or Bsplice, but not less than 300 nlrn.,where Class A splice .......... .... ,..... 1.0 Ld Class B spikes :...... .. :...... :... 1.3 Ld

j j ~

'

..;J -~

~

where Ld ·is the ten5ile development length for the specifi~ yield strength fy.

-1

~_.J

:~

Lap splices of deformed bars and deformed wir'e in tension shail be. Class B j splice~ except th;3.t Class A splices are allowed when: · "' ~ . (a) the area · of reinforcement provided is at ieast twice that required by ~ analysis over the entire length of the splice, and - ·~

(b) -one-half or less of the total reinforcement is spliced within the required lap strength. ,.

'

Welded ~plic~s or mechanical connections u~ed· \·vhere area of reinforcement :,~ provided is at least twice .that required by analysis shall meet the following: ·~ (a) splices shall .be staggered at least 6QQ ·rnrn and in such manner ·as to develop at ever}' section a~ least twice the calculated tens!le fo.rce at that -~ · _section but not less than 140 MPa for totaLarea ofreinforcemerit provided, 'l

l

~

i

(b) i~ com,puting tensile force developed at _ea~h portion;· spliced '"~ reinforcement maybe rated .at ·.. the _specified _splice ·strength. In spliced ·~ reinforcement shall be rated at thatfracti<>n offy defined by the ratiO of the ·i shorter actual development length to Ld reqtiired to develop the specified :j yield streng~h fy. . · - . ~ ./

169

CHAPTER 5 - BONO, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

Splices of Deformed Bars in CompreSsion . Compression bars may be splice~ by lapping_ by end bearing, and by weldin'g.. or mechanical devices. According,to the Section 5.12.16.1, the minimum splice \ length of such barsshould be the development length Ld but may not be less '\ than0.Q7jyd;, for fy of 415 MPa or less, or (0.13fy - 24)d,_ for Jy greater than 415 , MPa. Should the concrete strength f c less than 20 MPa, the length of lap should ·· be increased by orie-third.

When bars{>f different size are lap spliced incompression, splice length shall be the larger of development length of larger bar, or splice length of smaller bar:

UPDATE FROM NSCP 2001; . (C101~01J Notations

Ab = area of an indjvidualbar, mm2 As= area of non~prestressed tension reinforcement, nun 2 . Atr =-total cross~sectional area of all transverse reinforcement which is within the spacings arid which crosses the potential plane of splitting through the reinforcement being developed, mm2 Av = area ofshear reinforcement witl\in a distances, mm2 Aw =area of an individual wireto be developed or spliced, mm2 a ::::depth of equivalent rectangular stress block asdefinedin Section 410.3.7.J, nuri . bw = web _width, or diameter of circular section, mm c.= spacing or cover dimension, mm. See Section 412.3.4 d =: distance ·from extreme compression fiber . to centroid of tension · I·· reinforcement, mm db = nominal diameter of bar, wire or prestressing strand, imn. f c = sp~ified compressive strength of concrete, MPa ·'· -

.JF:- ;;._square root of specified compressive strength ofcpncret~, MPa

.

/ct=: average splittingtensile strength of lightweight aggregate c_oncrete, MPa , fps

=stre5s in prestressed ~einfcm:em~nt.at nomin~fstrength, MPa .

. ': · f~ ,,; effective stre_ss irt prestressed reirtforceinent (after allowance for all prestress losses);MPa · · .·· · ·

fy = spedfiedyield strength of non-prestressed reinforcement, MP~ fy, = specified yi~ld strength of transverse reinforcement, MPa h =overall thickness. ofmember, mm . Ktr = transverse reinforce;ment index =A,,ht/1 Osn · (

REINFORCED CONCRETE DESIGN

170

la = additional embedment length at support or at point of inflection,' rrun ld = development length, mm ld = ldb multiplied by applicable modification factors ldb = basic development length, rrun ld11 = development length of standard hook in tension, measured from critical

ldh

section to outside .end of hook [11traight embedment length between critical section and start of hook (point of tangency) plus radius of bend and one bar diameter], mm = lhb times applicable modification factors

lw = b~sic development length of standard hook in tension, mm

M.. = nominal moment strength at section, Newton meter

:4n =Ash (d- a/2)

N =number of bars in a layer being spliced or developed at a critical section -n = number of bars or wires being spliced or developed along the plane of splitting s = maximum \center to !=enter spacing of transverse reinforcement within ld, mn\

= spacing ~f wire to be developed or spliced, m:rh Vu ='factored shear force at section a= reinforcement location factor. See Section 412.3.4. ~ = coatingfactor. See Section 412.3.4. ~b = ratio of area of reinforcement cut off to total area of tension reinforcement at section y = reinforcement size factor. See Section 412.3.4. , t..' =lightweight 'aggregate concrete factor. See Section 412.3.4. Si"

DEVELOPMENT OF ~EIN.FORCEMENT- GENERAL 412.2.1 Calculated tension or compression ih reinforcement at each section of structural concrete members shall be developed on each side of tha,t section by emb~dment length, hook or mechanical device, or a combination thereof. Hooks shall not be used to develop bars in compression.

412.2.2 The values of' f]'; used in Section 412 shall not exceed 8.0 MPa,

171

CHAPTER 5- BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

Development of defonned Bard and ~eformecl Y,lire in Tension 412.3.1 Development length, l4, in terms of diameter, db, for deformed bars artd d~formed wire in tension shall be determined from either Section 412.3.2 or 412.3.3, but ld shall not be less than 300 mm.

4123.2 Fbr' deformed bars or deformed wire, 14/ db shall be. as follo'ws: . \

'

spacing of bars being developed or spliced rtot less . than db _clearcover not less than d", and_stirrups or ties thtougho\lt ld notless than the code minimum or ·Clear spacing of bars being developed or spliced notless . ·than

-

, td _ 12/yc;xPA

a;-

Other cases

25.{f;

'

ld _ 3/ycxPA

a;-

s.Jt;

ld _ 9fya.PX

d~- - 10J7':

4123.3 For deformed bars or deformed Eq.

s~

9'

in which the tern\ (c + k,)j db shall not be taken greater than 2.5 4123.4 The factors for use in the expressions for d~velopment of deformed bars and defo~ed wires in tension in Secti~ris 412.1 through 41~:20 are as follows: ·:'

REINFORCED CONCRETE DESIGN

where: A, = totaLcross-sectional area of all transverse reinforcement which is within the spacings andwhich crosses the potential plane of splitting through the reinforcement being developed, square millimeters. fy, = specified yield strength of tran5verse reinforcement, square m.illimeters. · s = maximum center-to-center spaCing of transv.erse reinforcement within ld, millimeters. . · . . . . N = number of bars or wires being developed along the plane of splitting. It shall be permitted to use K, = (} as a design simplification even if transverse reinforcement is present. 412.3.5 Excess reinforcement. Reduction. in devek1pmerit length shall be permitted wher.e reinforce01ent in a flexural member is in excess of that required by analysis except where anchorage or .development for h is specifically required or the reinforcement is designed under provisions of Section 421.2.1.4 ·····································~·····························HA~ reqwred)/(A. PJ'!'Vided)]

CHAPTER 5 - BOND, OEVELOPMENT LENGTH, HOOKS, AND SPLICES

·1-73

Development of Deformed Bars. in Compression

4i2.4.i Developmerirlength ld, in millimeters, for deformed bars in co~pression. shall be computed as the product of the basic development length lab and, applicable modification factors-as defined in·this section, but la shall not be less than -209 mm, . . .

.

.

-

412.4.2 Basic·development length ·lab shall be

I

..• Eq

5-101

412.4.3. Basic development lerigth lab shall be -permitted to be multiplied by

applicable factors for:

·

-

412.4.3.1 Excess remforcement. ..Reinforcement in excess of that required by analysis ............................... ~ ...........................:····· ..... .-........ (As required)/ (As provided) 412.4.3.2 Spirals and ties Reinforcement enclosed within spiral reinforcement

not less than 10 nun diameter and not more than 100 mm pitch or within 12 mm diameter ties in conformance with Section 407.11.5 and spaced hot more · than 100 min on c~~tE,!r ................ ;; ............................. ,................. ,.........:.......... .-;0.75

.REINFORCED CONCRETE DESIGN

174

ILLUSTRATIVE PROBLEMS · PROBLEM 5.1

A rectangular beam 260 nun by 580 nun is reinforced with four 2$ ttun diameter top bars, with strength fy = 375 MPa, to resist tensile stress. Jf the concrete strength [c is 21 MPa, calculate the required development length. SOLO~ON

Basic development length for 25-nun-diameter bar: ldb = lab=

0.02Ab

/y

(Sec. 5.12.2.2)

[71""

vfc

0.02xf(25) 2 x (375)

---=--=,.----

Jil '

lab= 803 mm

and lab shall be not less than lab= 0.06 db fy = 0.06 (25)(375) = 562.5 nun

· -Modification factor for top bar= 1.3

(Sectiolll5.12.2.4.1)

Then,La= 803 x1.3 =1044mm

PROBLEM 5.2

Determine the development length required·for 25-nun diameter top bars·in lightweight concrete. Assume fy = 345 MPa and [c = 20.7 MPa. SO LUttON

For 25-nun bar, lab=

0.02Ab

/y

..[f;

_ 0.02 X f(25)f X 345 .J20.7 ldb = 744m but not less than, lab= 0.06 db}'y = 0.06 (25)(345) =5t7.5mm ·

CHAPTER 5 - BONQ, DEVELOPMENT l-ENGTH, HOOKS, AND SPLICES

175

Modification factors: For top bars =1.3 · For lightweight concrete= 1.3 theri, Ld=; 744 x 1.3 x 1.3 · =1,257mm

PROBLEM 5.3 ·.

A reinforced. concrete wall footing has 25-mrn~diameter straight bottom .ba~s extended from face of column to within 75 mm of the edge of the footing . .If fy= 414 MPa ijndfc = 20.7MPa, how far should the edge of the footing from the face of the wall? · . SOluTION

·x= zd+75

but not less than; ld =0.06 dt>fy =0.06 x 25 x 414 · =621 mrn , , Use Ld ,.,; 893.3 m:rn as there are no applicable modification factors .

.· Then~ = 893.3 + 75 = %8 mm say 97(hnm

PROBLEM 5.4

A cartti]ever beam is reinforced with four 28-mrn diameter b~r ~ithfy = ~76 MPa. Detemune the requir~d devclopm~nt)ength ·if the bars ate straight. Usefc =27.6MPa and assume side, top, and bottom cover to be greater than ·

60min.

176

. REINFORCED CONCRETE DESIGN

SOLUttON

If the bars are straight; 0.02Ab fy I

---==-::..._

ldb =

ffc. 0.02x f (28) 2 x 276

= ldb

.}27.6

= 647mm

b~t

not less than,

·

ldb

= 0,06 dbjy = 0.06 x 28 x 276

= 463.68mm

Modification factor for top bars =1.3 Required development length, Ld = 647 x 1.3 Required development length, Ld= 841.1 mm say 850 mm

PROBLEM 5.5 . A cantilever beam is reinforced with four 28-mm diameter bar with fY = 276 MPa. Use f c =27.6 MPa and assume side, top, and bottom cover to be greater than60.mm. · a) Determine.the required development length if a 180° hook is used. b) Determine the required development length if a 90° hook is used. SOLUttON

Using a180°· hook: - 100db ' ' lllb- ffc (Sect. 5.12.5.2) :.. 100(28) - .i2'Z.6 ldb=53.3.mm Modification factor forfyother fhan415MPa (sec. 5.12.5.3.1) m =fy/ 415 · = 276 I 41s m = 0.665

=

Required development length, Ld11 53.3 x 0.665 Required development length, Ldl, = 354.4 mm SflY Ld11 = 360 mm

CHAPTER 5- BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

17.7

Using a 90° hook:

JJ! .

. lOOd 'I,.~= .~

· . ·.. ($ect. 5,12.5.2)

- 100(28) ~ . ~27.6

ldb= 533mm .

'

Modification factor for fy Qther than 415 MPa (Sec. 5.12.5.3.1) m=JY/415 =·276 1415 m = 0.665 °

°

•

Modification factorfor 90° hook= 0.70 (Sect. 5.12.5.3.2) Required development-length, Ldh = 533 x 0.665 x 0.70 Requiredde'vefopment length, Ldh = 248 inm sayLdh= 250mm

PROBLEM 5.6 For the simply supported beam shown Figure 5.9,investigate whether the biu siZes are satisfactory for the required d~velopment length. The-;beam is reinforced with 28 mm bars and two bars were extended from the maximum' moment area and into the support. Jy = 414: MPa, fc =20.7 MPa,;V, = 290 kN. The beam is made.of normal sand-gravel concrete and the reactiort produces compression on concrete.

m

175mm

.Figure 5.9

°

178

REINFORCED CONCRETE DESIGN

SOLUTION·

Basic development length, ldb= 0.02 Ab/y / zdb ldb

,fJ'; but not les~ than 0.06 dbfy

=o.o:i f(28)2 (4H)/ .J2o.1 ~ . 1,121

,,' -I~

1 .:

1!.

mm f

·--- ~~

hit not less than .0.06 db fy = 0.06(28)(414) = 695.5 mm Sin~e

there is no applicablemodification factor, Ld = 1,121 ,llUll

. . M . Maximum Ld = 1.3-1!..+ la Vu Mn =Asfy (d- aj2). A. sfy. a= .--"--0.85-f'cb

= . t(28{x 2(414) 0.85(20.7)(300) . tz=96.6mm_

= t (28)2 X 2 (414)(600- %.6/2) . Mn = 281,280',266 N

. M;,

M. . . . L 281,280,266 + 175 . • · axxmum d =1.3 .. 290,000. Maximum Ld = 1436 nun > 1,121 (OK) · Thus, the ba:rsare satisfadory Note: If this condition had not been satisfied, a smaller bar size may be used or the · anchorage 1. may .be increased, or !:he by the use of hooks. ·

PROBLEM 5.7

A rectan'gular beam has.b = 380 mm and d = 500 mm. The beam is simply Supported over·a length of 6 m (measured from-the center of support) and is " reiriforced·for tensi9n only w~ 6 :.. 25 mm bars. Assutning.fY = 276 MPa c:tJtd f, = 2lMPa, draw the detail of the bars. showing the cut-off points of each ; bar. Assume that the beam carries a uniformly distributed load throughout . its lettgth and is made of normalsand-grav:el concrete. The .reaction .a.t the . - -ends produces compression on concrete. Maximum value of la =150 mm. . · ·V 11 = 210 kN ~t support. · ·

CHAPTER 5 - BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

179

SOLUTION

Basic development length for 25 mm bars in tension: lab= 0.02 Abfy / ..[F; but not less than 0.06 dbfy ·~

= 0.02f (25) 2 (2'76)/ffl lab= 591 mm 0.06 dbfy = 0.06(25)(276) 0.06 dbfy = 414 mm Uselab == 591 mm

Since there is no applicable modification factor, La= 591 mm At the point of maximum moment (at midspan), the required area is total area of the bars' As = f (25) 2(Q) As ,;. 2945 mm2.

the

The following table shows how the moment is affected as tl,le. bar area is · changed. Steel area (mm2)

M,. (kN-m)

As= 2945 ~As,;, 1963

322

!As= 982

117

3

'

It can be observed that as the area is reduced

224

tQ 2/3, the moment is re<:luced to a value a little higher than 2/3 of its original value (224 > 2/3 o£322) and as the area is reduced to 1/3, the mon:(ent is red~ced to a vall!e a little higher than 1/3 of its original value (117 > 1/3 of 322). Thus, to avoid tedious calculation, the cut-off points of the bars may be ~aken (conservatively) from the shape of the moment diagram

REINFORCED CONCRETE DESIGN

180

-~

l

) .... . ·.·•t•.:· J. ·,•. ~··.

4 bars X2

X2

' X!

2 bars

X!

For illustration purposes, the bars are drawn in thr~e layers (actually they are placed in one layer). The code (Section 5.12.11.1) requires that at least l/3 of positive moment reinforcement (As) be extended into the support, then 2. bars will be extended into the support as shown in the "bottom" layer. · .

.

The theoretical length of each layer on each side "from the centerline is . computed as follows (using the squared property of parabola):· · X 2 X 2 32 _2_ = __1_ =·--

y/3

2y/3

y

=2.45m· X2 :;:J.73m"'

Xt

The code (Section 5.12)0.3) also requires that reinforcement be extend beyond ·the point at which it is no longer required to resist flexure fof. a distance equal
12 db =12(25) =300 mm effective depth, d = 500 mm

CHAPTER 5 - BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

Thus;

Lt

181

= x2 + 500 = 1730 +500

Lt = 2230 xnm> Ld (no need of hook) L2 = =

L2

Xt + 500 . 2450 +500 2950 tnm > Ld (no need of hook)

=

For the "bottom layer" the Code {5.12.11.3) requires that the bars shall be limited to diameter so thatLd shoulcl not~xceed 1.3 M,.jV,; + la:

a

.

As {y

a=~---"--

0.85f'cb A$=

f

(25)2.x 2

As=982mm2 982(276) 0.85(21)(380) a=40mm a=

= As{y (d- aj2) = 982(276)(500- 40/2) Mn = 130,095,360 N-mm

M 11

1 .3 Mn + la =1 _3 130,095,360 + 150 vu 210,000

M

.

vu '

.

1.3 -.·-" + ~a= 955 > Ld (OK)

Thus,

.

L3 '=.3000+ 150 L3 =31SO nun (no neecl of hook)

Cuttin$J detail (symmetrical with the center of beam)

REINFORCED CONCRETE DESIGN

182 PROBLEM 5.8

Figure 5.10 shows the first inte~or support of a continuous · beam. The beam is reinforced with six 25 riun ·bars to resist a negative moment of 496 ·· kN-m for which the calculated As required is 2600 mm2. Determine .and draw the detail of the lengths of the bars requir_e d if the normal sand-gravel concrete is used. Use fy == 4~4 MPa and fc =20.7 MPa,

b =350 mm d

2.4 m 2.1 m

Figure 5.10

SOL'!f!ON

Section A

.

= 60()mm

CHAPTER 5 - BOND, DEVELOPMENT LENGTH, HOOKS, AND SPLICES

For illustration purposes, let us assume X1

183

= 330 mm and X2 = 300 mm

Basic development length for 25 mm bars in tension: ldb

.[1': but not less than 0.06 dbfv 0.02 Ab/y I .[1': = 0.02 t (25)2 (414)1 .J20.7 0.02 Abfy I .[1': = 893 mm

= 0.02 Abfy I

0.06 db/y = O.Q6(25)(414) = 621 mm Use ldb = 893 mm For bar a: (Total As at section = 2-25 mm) The Code (Sect. 5.12.121.3) requires that at least one-third the total tension reinforcement provided for negative moment at a s'u pport shall have an embedment length beyond the point of inflection not less than effective depth of member, 12db, or one-sixteenth the clear span, whichever is greater.

t of 6 = 2 bars Embedment length, the larger value of: a) · d=600mm b) 12 db = 12(25) = 300 mm c) 1,116 = 7000116 = 438 mm for the 7-m span 1,116 = 10000116 = 625 mm for the 10-m span For the 7-m span, use 600 mm For the 10-m span, use 625 mm Thus;

L3 = 2400 + 600 = 3000 mm L4 = 2100 + 625 = 2725 mm

For barb: (Total A. at section = 4-25 mm) The Code (Sect. 5.12.10.3) requires that reinforcement shall extend beyond the point at which it is no longer required to resist flexure for a distance equal to the effective depth of member or 12db, whichever is greater, except at supports•of simple spans and at free end of cantilevers. Extension, the larger value of: a) d = 600mm b) 12 db = 12(25) = 300 mm Thus,

L1 = 330 + 893 = 1,223 mm L2 = 300 + 893 = 1,193 mm

REINFORCED CONCRETE DESIGN

184

For bar c: (Total As at section = 6-25 mm) Required Ld = ldb x modification factor The applicable modification factor, m m=

2600

t (25) 2 (6)

Ld = 893 X 0.88 Ld = 785 mm = Ldt

=

=

As reqd/ As provided

0.88

= Ld2

SUPPLEMENTARYPROBLEMS

.

PROBLEM 5.9

Calculate the basic development length fo;: a 25-mm bar havirig fy = 345 MPa embedded in concrete with fc = 27 MPa to resist tensile forces.

PROBLEM 5.10

Calculate the basic development length for a 25-mm bar having fY embedded in concrete with f c = 48 MPa to resist tensile forces.

= 414

MPa

PROBLEM 5.11

Calculate the basic development length for a 20-mm bar having fy = 276 MPa embedded in concrete withfc = 20.7 MPa to resist compressive forces.

PROBLEM 5.12 ·

Calculate the basic development length for a 25-mm bar having fy = 414 MPa embedded in concrete withfc = 48 MPa to resist compressive forces.

PROBLEM 5.13

A rectangular beam is reinforced with 4-28 mm top bars to resist tensile forces. Assumingfr = 21 MPa andfy = 414 MPa, determine the required development length.

PROBLEM 5.14

A rectangular beam is reinforced with 4-28 mm top bars to resist tensile forces. Assuming f , = 21 MPa and fY = 414 MPa, determine the required development length if the bars have clear spacing of 30 mm.

CHAPTER 6 -AXIALLY LOADED COLUMNS

185

Chapter 6 Axially Loaded Columns CLASSIFICATION OF COLUMNS In general, columns are classified as short columns and long columns. If the height of the column is less than three times its least lateral dimension, it may be considered as short compression blocks or pedestal. Pedestals may be designed without reinforcement with a maximum permissible compressive strength of 0.850 f" where 121 is 0.70 (Sect. 5.10.15). If the compressive strength is greater than this value, the pedestal will have to be designed as a reinforced concrete short column. If the reinforced concrete column fails due to initial material failure, it is classified a·s short columns. The load of the short columns depends on the dimension and the strength of the material of which it is made. If the length of the column is increased, the chances that it will fail by lateral buckling will be increased. Columns that fail by buckling are called long

columns.

·

P-delta Moment When a column is subjected to priman; moments M, such as those caused by applied loads or joint rotation, the axis of the member deflects laterally. This deflection causes additional moment applied . to the column, whiCh is equal to the column load times the lateral deflection. This moment is called secondary moment or P-delta moment, as shown in FIGURE 6.1.

p

\

Figure 6.1: Secondary or P-delta moment

186

REINFORCED CONCRETE DESIGN

If the secondary moment becomes too large, the column is said to be long column and it is necessary to design its section for the sum of both primary and secondary moments. However, the Code permits that columns be designed as short columns if the secondary or PL'l effect does not reduce their strength by more than 5%:

TYPES OF COLUMNS b

Steel tubing

...... M

II

.c

x

"' ::E

(a) Plain concrete pedestal

(b) Tied column

(c) Spiral column

(d) Composite columns

Figure 6.2: Types of coi(Jmns

(a) Plain concrete pedestal - This may be used only if the height does not exceed three times the least lateral dimension. (b) Tied columns - A column in which the longitudinal bars are braced with a series of closed ties. (c) Spiral columns - a column in which the longitudinal bars and concrete core are wrapped with a closely spaced helix or spiral. (d) Composite columns - These columns may contain a structural steel shape surrounded by longitudinal bars with ties or spirals or it may consist of high-strength steel tubing filled with concrete. Tied and spiral columns are the most common forms. Either type may be circular, octagonal, square, or rectangular section. Tied columns may also be L, T or other irregular shape.

CHAPTER 6 -AXIALLY LOADED COLUMNS

187

AXIAL LOAD CAPACITY OF COLUMNS Axial load without moment is not a practical case in design of columns, but the discussion of such case is necessary for explaining the theory involved in eccentrically loaded columns. For .a column subjected purely by an axial load, the nominal load Pu that it can carry is the sum of the strength of steel which is fyAst and the strength of concrete 0. 8~f,(A 8 - A5t), where A8 - Ast is the net concrete area, or P, = 0.85fr(Ag- Ast) + fyA st

Eq. 6- 1

~~----------------~--~

To counter the effect of possible eccentricities, the nominal strength P, is multiplied by 0.80 for tied columns and 0.85 for spiral columns. Finally, the ultimate axial load capacity of the column P" is 0Pu, where 0 is 0.70 for tied columns and 0.75 for spiral columns.

TIED COLUMN

s

s

s

Figure 6.3: Tied column

The axial load capacity of the tied column is given by

P"

= 0

P,=

0

0.80 [0.85 f c (Ag- A,,)+ fy A,,]

Eq. 6- 2

--~~~~----------~--~

0 = 0.70 Ag "' gross concrete area = b x t Ast = area of steel reinforcement I These maximum load limits govern ·wherever the moment is ,s mall enough to keep the eccentricity under O.lOh where h is the column width parallel to the applied moment.

where

188

REINFORCED CONCRETE DESIGN

Limits of Reinforcement for Tied Columns (Section 5.10.9)

I. Ast shall not be less than 0.01A 8 and Ast shall not be more than 0.06A 8 .

II. The minimum number of longitudinal bars is 4 for bars within rectangular or circular·ties, 3 for bars within triangular ties. Sizes and Spacing of Main Bars and Ties

I. Clear distance between longitudinal bars shall be not less than 1.5db nor 40 mm. (Section 5.7.6.3) II. UseJO-mm diameter ties for 32-mm bars or smaller and at least 12 mm in size for 36 mm and bundled longitudinal bars. (Section 5.7.10.5.2) III. Vertical spacing of ties shall be the smallest of the following: (Sect. 5.7.10.5.2) 1. 16 x db (d11 =longitudinal bar diameter)

2. 48 x tie diameter 3. least dimension of the column IV. Ties shall be arranged such that every corner and alternate longitudinal bar shall have latera] support provided by the corner of the tie with an included angle of not more than 135° and no bar shall be farther than 150 rrun clear on each side along the tie from such a laterally supported bar. Where longitudinal bars are located around the perimeter of a circle, a complete circular tie is allowed. (Section 5.7.10.5.3). 150 mm (max)

150 mm (max)

150 mm (max)

....v iS 3

3

Figure 6.4: Typical tie arrangement

189

CHAPTER 6- AXIALLY LOADED COLUMNS

SPIRAL COLUMN

5

Pitch, 5

h

Figure 6.5: Spiral column

The axial load capacity of a spiral column is given by

', I L

P, =

0

P, =

0

0.85 [0.85 f , (Ag- A,,) + fy A,,]

Eq. 6-3

I

where

0 =

0.75

This maximum load limit governs wherever the moment is small enough to keep the eccentricity under 0.05h.

Limits of reinforcement for spiral columns (Section 5.10.9)

I. Ast shall not be less than 0.01A 8 and A,, shall not be more than 0.06A 8 . II. The minimum number of longitudinal bars is 6. I

I I

Sizes and spacing ·of spirals

I.

.

For cast-in-place construction, size of spirals shall not be less than 10 mm (Section 5.7.10.4.2)

II. Clear spacing between spirals shall not exceed 75 rnrn, nor less than 25 mm. (Section 5.7.10.4.3) III. Anchorage of spiral reinforcement shall be provided by 1-% extra turns of spiral bar. (Section 5.7.10.4) IV. Splices of spiral reinforcement shall be lap splices of 48db but not less than 300 mrn or welded. (Section 5.7.10.5)

190

REINFORCED CONCRETE DESIGN

V. The percentage of spiral steel Psis computed from the following equation

p.=

volume of spiral in one loop volume of concrete core for a pitch s

~----------~--------~~--

_ 4a 5 (D, -db) p---5

sD

c

Eq. 6-4 Eq. 6-5

2

where a5 is the cross-sectional area of spiral bar, D, is diameter of the core out to out of the spiral, and d1, is the diameter of the spiral bar. VI. The minimum spiral percentage is given by: (Section 5.10.9.3)

Psmin "= 0.45 (Ag -lJL£ A,

fy

where fy is the specified yield strength of spiral reinforcement but not more than 415 MPa.

ECONOMICAL COLUMN ·DESIGN

In beams, where 60% to 70% of its section is under tension and assumed to be cracked, a section can be made economical by making the tension part smaller in area, as in I or T section. In columns where all the concrete is under compression, savings can be made by using small percentage of longitudinal percentages (since reinforcing bars are quite expensive). This can be accomplished by "using larger column size and/ or higher-strength concrete. If floor space is not a problem, tied columns are more economical than spiral columns particularly if square or rectangular shapes are used. For multi-story buildings, savings can be achieved by using uniform column size. This means that a designer may select a column size for the top floor with the least \ percentage of steel then continue to use the same size for as many stories as J possible by increasing the steel percentage floor by floor as required. ·\' Consistency of column sizes will provide appreciable savings in labor cost.

I

\

191

CHAPTER 6 -AXIALLY LOADED COLUMNS

COMPOSITE COLUMNS (SECTION 5.10.14)

Composite compression members include all such members reinforced longitudinally with structural steel shapes, pipe, or tubing with or without longitudinal bars. Strength of a composite member is computed for the same limiting j;Onditions applicable to ordinary reinforced concrete members. Any axial load strength assigned to concrete of a composite member should be transferred to the concrete by members or brackets in direct bearing on the composite member concrete. All axial load strength not assigned to concrete of a composite member should be developed by direct connection to the structural steel shape, pipe, or tube. According to Sec. 5.10.3.5.1, the design axial strength P, of a composite member is:

l_ __________P_,_=_0_P_n_=_0__0._85~[0_.8_5~f_cA_,_·+~!J~y_A_st_+_F~y_A~~]~______E_q~._6_-_!l~ where

~

= 0.75 for composite member with spiral reinforcement

= 0.70 for other reinforcement As, = area of reinforcing steel of strength fy ~

Ass = area of structural steel shape of strength Fy A c = net concrete area For evaluation of slenderness effects, radius of gyration of a composite section should not be greater than the value given by

Eel 8 I 5 + E5 I 1 EcAg I 5 + £ 5 A 1

r= [

Eq. 6-8

- - - - - - - - - '

Structural Steel Encased Concrete Core (Section 5.10.14.6) ~ t

D

t (a)

t

Steel pipe filled with conc;rete

(b) Steel tubing filled with concrete

Figure 6.6: Composite columns

192

REINFORCED CONCRETE DESIGN

For steel pipe filled with concrete Figure 6.6 (a) :

Eq. 6-9

For steel tubing filled with concrete Figure 6.6 (b):

Eq. 6-10

Spiral Reinforcement Around Structural Steel Core (Section 5.10.14.7)

7\ composite member with spirally reinforced concrete around a structural steel · core should conform to the following: 1. Specified compressive strength of concrete [c should be not less than 17 MPa.

2. Design yield strength of structural steel core should be the specified minimum yield strength for grade of structural steel used but not to exceed 350 MPa. 3. Spiral reinforcement should conform to Sec. 5 . 10 .~.3 (See page 189) 4. Longitudinal bars located within the spiral should be not less 0.01 nor more than 0.08 times net area of concrete section. 5. Longitudinal bars located within the spiral may be considered in computing A,, and I,.

.

Tied Reinforcement Around Steel Core (Section 5.10.14.8)

A composite member with laterally tied concrete around a structural steel core should conform to the following: 1. Specified compressive strength of concrete f c should be not less than 17 MPa. 2. Design yield strength of structural steel core should be the specified minimum yield strength for grade of structural steel used but not to exceed 350 MPa. 3. Lateral ties should extend completely around the structural steel core. 4.

Lat~_ral ties should have a diameter not less than 1/50 times the greatest side dimension of composite member, except that ties should not be smaller than 10 mm and are not required to be larger than 16 mm. Welded wire fabric of equivalent area is permitted.

193

CHAPTER 6 -AXIALLY LOADED COLUMNS

5. Vertical spacing of lateral ties should not exceed 16 longitudinal bar diameters, 48 tie bar diameters, or V2 times the least dimension of the composite member. 6. Longitudinal bars located within the ties should be not less than 0.01 nor .more than 0.08 times net area of concrete section. 7. A longitudinal bar should be located at every corner of a rectangular cross section, with other longitudinal bars spaced not farther apart than one half the least side dimension of the composite member. 8. Longitudinal bars located within the ties may be considered in computing Ast for strength but not in computing It for evaluation of slenderness effects.

(a) Spiral reinforcement around structural steel core

(b) Tied reinforcement around structural steel core

Figure 6.7: Composite columns with spiral and tie reinforcement

194

REINFORCED CONCRETE DESIGN

ILLUSTRATIVE PROBLEMS PROBLEM 6.1

A square tied column 400 mm on each side is reinforced with 8-25 mm bars withfy = 275 MPa. Assumingfc = 22 MPa, determine the ultima te axial load capacity of this column. SOLUTION

Pu = $ 0.8 [ 0.85 /c (Ag - Ast) + fy Ast] Ast =

f

(25)2

X

8

Ast = 3927 mm2 •

P,. = 0.70(0.8) ( 0.85(22)(4002 - 3927) + 275(3927)] Pu = 2,239,154.456 N P, =2,239kN

PROBLEM 6.2

Design a square tied column is to support an axial dead load of 575 kN and an axial live load of 795 kN. Assume f r = 27.6 MPa, and Jy = 414 MPa. Use 28 mm main bars and 10 mm ties. • SOLUTION

In the design of column, first we assume value of steel ratio from 1% to 6% of the gross concrete area. (Ast = 0.01A 8 to 0.06A 8 ). Obviously, if we assume small values of this ratio, the column .size would be bigger and the steel area would be smaller, and vice versa. The author suggests using a value less than the upper limit of 6%A8 , to provide an allowance for excess reinforcement due to availability of bar sizes. The ideal value is from 0.015A 8 to 0.03A 8 . Let us assume Ast = 0.02A 8 The axial load capacity of a tied column is Pu = 00.80[0.85 /r {Ag- Ast) + fy Ast] where 0 = 0.70 P,. = 1.4DL + 1.7LL . = 1.4(575) + 1.7(795) Pu = 2,156.5 kN

Ast= 0.02A 8

CHAPTER 6 -AXIALLY LOADED COLUMNS

195

2156.5 X 103 = (0.70)(0.80)[0.85(27.6)(Ag- 0.02Ag) + 414(0.02Ag)] Ag = 123147 mm2 = tz t 2 = 123,147 t =351 mm ~

As, = 0.02(123,147) A st

= 2463 mm2

f

(28) 2 X N = 2463 N = 4 bars Use 355mm x 355mm column with 4-28 mm bars Spacing of ties: a) 16 x db = 16(28) = 448 mm b) 48 x tie diameter= 48(10) = 480 mm c) Least dimension of column = 355 m.m Use 10 mm ties at 355 mm o.c.

PROBLEM 6.3

Design a square tied column of smallest cross-section to carry an axial dead load of 684 kN and an axial live load of 542 kN. Assume f c = 20.7 MPa and fy = 276 MPa. Use 22 nun main bars and 10 m.m ties. SOLUTION

For the section to be smallest, use A ,, = 0.06 A 8 (the maximum value) P" = 00.80[0.85 f , (A 8 -A,,) + fy A,,]

where 0 = 0.70

p/1 = 1.4(684) + 1.7(542) P11 = 1879 kN 1879 X 103 = 0.70(0.80)(0.85(20.7)(Ag- 0.06 A g) + 276(0.06 Ag)] A 8 = 101,372 mm2 = t2 t = 318 mm say 320 mm

A,,= 0.06(101,372) Ast

= 6,082 mm2

Number of bars: ~- (22)2 N = 6,082 N

= 16 bars

196

REINFORCED CONCRETE DESIGN

Check for maximum steel ratio: A,,= (22)2 X 16

t

A,, = 6,082 mm2 Ag = 320 X 320 Ag = 102,400 mm2

Pg

Ast / Ag 6,082/102,400 Pg = 0.059 < 0.06 (OK) = =

.:

PROBLEM 6.4

• Calculate the ultimate axial load capacity of a round spiral column having a diameter of 450 mm reinforced with six 25 mm bars having fy = 276 MPa. Assume f, = 34 MPa. SOLUTION

P" = 00.85[0.85 f,(Ag

~A,,)

+ Jy A,,]

f

(25) 2 X 6 Ast = 2945 mm2

Ast =

Ag = f (450)2 Ag = 159,043 mm2 P11 = 0.75(0.85)[0.85(34)(159,043- 2945) + 276(2945)] = 3,394,083 N P,. = 3,394 kN

PROBLEM 6.5

Design a round spiral column to support an axial dead load of 800 kN and an axial live load of 1350 kN. Assume that 2% longitudinal steel is desired, fc = 27.6 MPa, and fy = 414 MPa. Use 25-mm main reinforcement and 10-mm spiral with 30 mm steel covering. SOLUTION

The axial load capacity of spiral column is: P" = 00.85[0.85 fc(Ag- A,,) + Jy Ast] - c where 0 = 0.75

197

CHAPTER 6 -AXIALLY LOADED COLUMNS

P" = 1.4DL + 1.7LL = 1.4(800) + 1.7(1350) P" = 3415 kN A,t = 0.02A 8 3415 X 103 = (0.75)(0.85)[(0.85)(27.6)(Ag- 0.02Ag) + 414(0.02Ag)] Ag= 171,306 Ast = 0.02(171,306) AM= 3,426 mm2

Diameter of column: D 2 = 171,306 D = 467 mm say 470 mm

t

Number of bars: f (25)2 N = 3,426 N= 7 bars

Spiral pitch, s: d' = covering = 30 mm D,. = 470 - 2(30) 0,=410mm A 8 = f (470)2 = 173,494 mm2

f

A,. =

(410)2 = 132,025 mm2

d'

o

E

E

0

"

v Psmin

= 0.45

(Ag -1JD_ JIJ

Ac

= 0.45[173,494 -1] 27.6 132,025 414

Ps min = 0.00942 _ 4a, (Dc- db) Ps-

sOc

2

as= f (10)2 as= 78.5 mm2 0.00942

= 4(78.5)( 410 -10) s(410) 2

s = 79 mm (clear spacing s = 79- 10 = 69 mm)

d'

198

REINFORCED CONCRETE DESIGN

Maximum clear spacing by the Code = 75 mm Mirumum clear spacing by the Code = 25 mm Thus, use 10 mm spiral bar with pitch s = 79 mm

PROBLEM 6.6

Design a spiral column to carry a factored load of 1,570 kN and a factored moment of 20 kN-m. Assume [c = 27.6 MPa. Use 22 mm main bars with fy = 345 MPa and 10 mm diameter spiral bar with jy = 276 MPa. SOLUTION

The eccentricity of the load is, e =I! M .. / P .. = 20/1570 = 0.0127 m = 12.7 mm This column can be designed as axially loaded if the eccentricity is kept within 0.05/z, where h in this problem id the column diameter. Assuming that e < 0.05h P .. =

0

0.85[0.85 [c(Ag- A,,) + jy Ast]

Assume e = 0.03A8 1570 X 103 = 0.75(0.85)[0.85(27.6)(Ag - 0.03Ag) + 345(0.03Ag)] A 8 = 74,389 mm2

fD 2 = 74,389 D =308mm 0.05(308) = 15.4 > 12.7 (OK) Thus, this column can be designed as axially loaded with D = 310 mm Ast Ast

f

= o:03(74,389) = 2,232 mm 2

(22) 2 N = 2,232

N = 5.87 say 6 bars 25

Spiral: (Use concrete covering of 25 mm) De= 310- 2(25} De= 260mm A 8 = f (310) 2 A 8 = 75,476 mm2 · Ac = f (260) 2

E

0

Ac = 53,093 mm2 25

; ...,.....

CHAPTER 6 -AXIALLY LOADED COLUMNS

Psmin

=

. =

~ Ps mm

Ps min

0.45

(~-1)D,_ Ac /y

0.45[75,476 -1] 27.6 53,093 276 r

= 0.01897

a,=

f

(10)2 a, == 78.5 mm2 0.01897 = 4(78.5)(260- 10) . . s (260) 2 s = 61 mm (clear spacing = 61 - 10 =51 mm) Maximum clear spacing by the Code = 75 mm Minimum clear spacing by the Code = 25 mm Thus, use 10 mm spiral bar with pitch s = 60 mm

PROBLEM 6.7

Calculate the ultimate axial load capacity of the composite column shown. Assume fc = 21 MPa and Fy = 250 MPa for the W section. Properties of Wl4 x 211: Weight= 315 kg/m Area = 40,000 mm2 Depth, H = 399 mm Ir = 1,107 X 106 mm4 ly = 429 x 106 mm4 SOLUTION

P, = 0 P, =0 0.85 [0.85 fr Ac + Fy A..] A,,= 40,000 mm2 Ac = Ag- Ass Ac = 4802 -40,000 Ac =190,400 mm2

1ft

200

REINFORCED CONCRETE DESIGN

P, P,

= 0.70(0.85)(0.85(21)(190,400) + 250(40,000)] = 7,972,191 N = 7,972.2 kN

PROBLEM 6.8

Calculate the maximum axial load that the concrete-filled pipe shown can resist. Verify also if this section complies with the requirement of the Code. Use f , = 27.6 MPa and Fy = 250 MPa for the steel pipe.

SOLUTION

Verify if the section complies with the Code: fmin

= D ~ /y

8E 5 ,..--....,..,.,.-,----

= 300 tmin

250 8(200,000)

= 3.75 mm < 12 rnrn (OK)

[P, = 121 Pn] P, = 121 0.85 [0.85 f, A,+ Fy Ass) A, =

t

(276)2

A,= 59,828 rnrn2 Ass = (300 2 - 276 2)

i"

Ass = 10,857 rnrn2 P, = 0.70(0.85)[0.85(27.6)(59,828) + 250(10,857)] P, = 2,450,100 N = 2,450 kN . . II oad , pn = -Pu = 2,625 Maxtmum ax1a -

q,

Maximum axiaiioad, P,

0.70

= 3500 kN

CHAPTER 6- AXIALLY LOADED COLUMNS

201

PROBLEM 6.9

Determine the ultimate axial load capacity of the composite column shown. Use f, = 20.7 MPa, fy = 276 MPa for steel reinforcement, and Fy = 250 MPa for the structural steel section. Properties of W14 x 48: Area = 9,097 mm2 Depth, h = 350 nun

Weight= 72 kg/m

Ix = 201,87 x 106 mm 4

SOLUTION

Pu = 0 Pu = 0 0.85 [0.85 [c Ac + fy Ast + Fy Ass] Ass = 9,Q97 rnrn2 Ast = f (20)2 X 8 Ast = 2,513 rnrn2 Ac = 5002- 9,097- 2,513 A· = 238,390 rnrn2 P 11 = 0.70(0.85)[0.85(20.7)(238,390) + 276(2,513) + 250(9,097)] = 4,261,575 N

P.. =4,262kN

202

REINFORCED CONCRETE DESIGN

SUPPLEMENTARY PROBLEMS PROBLEM 6.10

Calculate the ultimate axial load capacity of a rectangular column 350 mm x 450 mm reinforced with six 25 mm bars. Use fy = 276 MPa and fc = 28 MPa. PROBLEM 6.11

Design a square tied column to support an axial dead load of 850 kN and an axial live load of 1040 kN. Use fy = 414 MPa and fc = 27.6 MPa. Assume 2% steel ratio and use 28 mm main bars and 10 mm ties.

PROBLEM 6.12

Repeat Problem 6.11 using 5% steel ratio.

PROBLEM 6.13

·Calculate the ultimate axial load capacity of a 480-mm round spiral column reinforced with six 22 mm bars. Use fy = 345 MPa andfc = 34 MPa.

PROBLEM 6.14

Design a round spiral column to support an axial dead load of 950 kN and an axial live load of 1210 kN. Use fy = 276 MPa and fr = 27.6 MPa. Assume 2% steel ratio and use 28 mm main bars and 10 mm spiral. Use 30 mm steel cover.

PROBLEM 6.15 .

Repeat Problem 6.14 using 5% steel ratio, 25 mm longitudinal bars, and 12 mm spiral.

CHAPTER 7 - SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

203

Chapter 7 Short C.olumns Subject to Axial Load and Bending AXIAL LOAD AND BENDING All columns are subject to axial forces as well as some bending and they need to ·be proportioned to resist both forces. The load capacity given by Eq. 6 - 2 and Eq. 6- 3 are only applicable of an eccentricity of 0.10h for tied column and 0.05h for spiral columns. Columns will tend to bend under the action of moment, .which produces · compression on one side of the column and tension on the other side. The following failures are possible under the combined axial and bending loads. 1.

Large axi~lload with negligible momentFailure under this condition occur by crushing of concrete with all reinforcing bars in the column having reached their yield stress in compression

2.

Large axial load and small moment with the entire cross-section in compression Failure occurs by crushing of concrete with all bars in compression.

3.

Large axial load with.moment larger than in (2) - Bars in far side in tension but have not yielded. Failure occurs by crusping of concrete.

4.

Balanced loading condition - Bars on tensile side yield at the same time concrete on compression side crushes at 0.85 f ,.

Plastic~·

centroid

204

REINFORCED CONCRETE DESIGN

5.

Large moment, relatively small axial load - Failure initiated by yielding of tensile bars.

6.

Large bending moment - Failure occurs like a beam.

PLAStiC CENTROID The plastic centroid of a column cross section is the point through which the . resultant column load must pass to produce uniform strain in failure. It represents the location of the resultant force produced by the steel and concrete. The eccentricity of a column load is the distance from the load to the plastic centroid of the column.

.

In locating the plastic centroid, all concrete is assumed to be stressed in compression to 0.85 fc and all steel to Jy in compression and the centroid is then located by taking moments due to these forces. For symmetrical sections, the plastic centroid coincides with the centroid of the column cross-section.

~Centroid I

See PROB,LEM 7.1

205

CHAPTER 7 - SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

ANALYSIS OF ECCENTRICALLY LOADED COLUMNS

The following procedure and formulas may be applied on determining the value of P" for columns with four rows of reinforcement perpendicular to the axis of bending (along side h).

~·.. ~

:t

h

;:

.....

~

T

J

J

N•

rvi

v-·

~

~

;: ~

J

b

l

,. '

'

~x2-+:

~X3--.:

' '

,

''

;----,-X4~

Given or known data: A.t, As:u A,3, As4, fy, fer b, h, d', e, Xt, X2, X3, and X4:

Z3

= =

Z4

=d'

Z2

----X----+:'

x = e + lf2x2 d=h-d'

X4- X2 X4- X3

Xc

b

= d- a/2

Steel stress:

d-e · must not be taken more than fY c

fs 1 = 600 - -

c-z 2 fs 2 = 600-c

must not be taken more than fY or less than -fy

c-z 3 /s3 = 600 - must not be taken more c than fY or less than -fy c-z4 fs4 = 600 - - must not be taken more than fy c T = Ast/st

~

c2 = Asz/sz

Cc = 0.85 [c a b = 0.85 [ c ~1 C b

C3 = As3/s3 [Lfv

= 0]

[LMr= 0]

=As4/s4

~Z2~ : I :

'

I

+-Z3~ I

I

' M

8 0

206

• REINFORCED CONCRETE DESIGN

The task is to solve the value of c or a. .If all steel yields, the value of c or a can be solved by quadratic equation. However, if some or all steel will not yield, the equation becomes a cubic equation, which can be solved by trial and error. Another approach to solve for Pn is to have series of assumption for the values of c until equilibrium conditions are satisfied.

ECCENTRICALLY LOADED COLUMN WITH TWO ROWS OF REINFORCEMENT If there are only two rows of reinforcements, this procedure can also be used with, As2 = As3 = 0. The following formulas can be applied for columns with two rows of reinforcements. FiJr column with large eccentricity and when all steel has yielded:

[f,l ... /s4 .. fy) T= A.tfy Cc • 0.85 /c a b (but since .Asl = As4 =due to symmetry) c4 ... A,1Jy

(4 .. AsAfy

['LFv =0]

P" = Cc + C4- T (since C4 = 1) P" =C, = 0.85 fc b a

['LMr .. OJ

C, Xc + c4 X4- P,. X = 0 X4

and x are known values

x.- = d- a/2 0.85fc b a (d- a/2) + As1fy X4- 0.85 fc b a X= 0 0.5 a2 + (x- d) a- Ast /y x 4 = 0 0.85 f', b Let m =x-d

Eq. 7-1

Ast /y X4 n= ---=-0.85/', b

Eq. 7-2

0.5 a2 + ma - n = 0 - m ± ~,.-m-2 ---4-(0-.5-)(--n-)

a=

2(0.5)

207

CHAPTER 1 - SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

Eq. 7-3

C""a/lh d-e

/st :;::600-c c-d' /54""600-c

Eq. 7-4 Eq. 7-5

If both /st and /s4 exceed fy, then assumption is correct and P.. = 0.85 fr b a See Problem 7.3.

BALANCED LOADING CONDmON Columns normally fail by either tension or compression. In between the two lies the so-called balanced load condition where failure may be of either type. Balanced loading occurs when the tension steel just reached its yield strain hiEs and the concrete is strained to 0.003. For every column there is always a balanced loading situation where an ultimate load Pb, placed at an eccentricity eb will produce a moment Mboo· If the eccentricity of a column is less than its balance eccentricity eb (e < eb), the column fails in compression (compression controls, /st <-fy), otherwise tension controls (/st = fy). In computing the . balanced loading, the procedure presented in page ·205 is applied with/st =hand solving for c. See Problem 7.2.

COLUMN INTERACTION DIAGRAMS It can be seen that the analysis of column~ with statics equations is very tedios and complicated. As a result, designers resort to diagrams or computer in designing columns. Interaction diagram .is a plot the axial load P, that the column can qury versus its moment M, capacity. This diagram is very useful for studying the strengths of columnS with varying proportidns of loads ~d moments. Any combination of loading that falls inside the curve is satisfactory, whereas arty combination that falls outside represents failure. The diagram is made by plotting the axial load capacity of the column at A, then the balanced loading B, then the bending strength of the column if it is subjected

208

REINFORCED CONCRETE DESIGN

to pure moment only at C. In between the points A and C, the column fails due to combination of axial and bending. Point B is called the balanced point. In reference to point D, the vertical and horizontal dotted lined represents the particular load combination of axial load and moment.

+ A

:1

Pure axial load

D

IC Compression failure

0

Figure 7.1: Interaction diagram

•

209

CHAPTER 7- SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

ILLUSTRATIVE PROBLEMS

.

PROBLEM 7.1

The T-shaped column shown is reinforced with 4-28 mm diameter bar with fy = 414 MPa. Determine the plastic centroid of the column measured from the 400-mm side. Assumefc = 27.6 MPa.

E E

~

~~ 150 mm

SOLUTION

The plastic centroid of the column is at the resultant of the forces due to concrete and steel.

200 mm

X

Dividing the section into two rectangles; For concrete: Ct = 0.85 [c Ac Ct = 0.85(27.6)(150)(400) Ct = 1,407,600 N c2 = o.85(27.6)(200)(200) C2= 938,400

8 N

8.....

~~ ~~

. For steel (less concrete) Ab = t (28) 2 = 616 mm2 c3= c4 c3 = (/yAb- 0.85fcAb) X 2 c3 = 2Ab(fv- 0.85fc) c3 = 2(616)[414 - o.85(27.6)J C3= 481,145 N Total C = C1 + C2 + 2C3 C = 3,308,290 N

'

E

E

~

210

REINFORCED CONCRETE DESIGN

Solving for x: . C x = C1(7S) + C2(2SO) + C3(75) + (4(275) 3308290x =1407600(75) + 938400(250) + 481145(75) + 481145(275) x=154mm

PROBLEM 7.2

. A rectanghlar column 350 mm by 600 mm is reinforced with 6-28-mm diameter bars with three bars along each 350 mm side. The center of the bars is located 65 mm from the column edge. Assume fy = 414 MPa and /c = 20.7 • MPa. Calculate the balanced loading Pbn, eb, and M,, for bending parallel to the long side of the column.

SOLUTION

With reference to the procedure presented in Page 205: d=h-d'=600-65 d=535mm X4

= h- 2d'

X4

=470mm

Asl = A.s4

= {- {28}2 X 3

As1 = A .. = 1847 mm2

d-e /sl =600- =fy

c·

414 = 600 535 -c

c

c=317mm a = ~1 c = 0.85(3l7) a=269mm

Xc

= d- aj2

Xc=400.5mm

/s4 = 600 c- z4

.

c

'

CHAPTER 7 - SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

/s4 = 600 317-65 = 477 MPa > fy 317 Use /s4 = fy = 414 MPa T = Ast/st = 1847(414) ~ T = 764,658 N ~ = As4/s4

=1847(414)

c4 = 764,658 N C= 0.85f,a b

= 0.85(20.7)(269)(350)

C =1,656,569 N [LFv =0] Pbn = ~ + C,- T

= 764,658 + 1,656,569 - 764,658

Pb,

= 1,656,569 N = 1656.6 kN

[Th1r= 0] ~ X4 + C Xc - P, X = 0 764,658(470) + 1,656,569(400.5)- 1,656,569 X= 0 x=617.45mm

x=eb+x4/2 617.45 = eb + 470/2 eb=382mm

Mb, M~n,

= P~n, x eb

=1656.6(0.382) = 632.82 kN-m

211

PROBLEM 7.3

In Problem 7.2 , calculate the nominal axial load capacity of the column that can be applied at an eccentricity of 450 mm. SOLUTION

With reference to the procedure presentE7_9 in Page 205: X4 X4

= h - 2d' = 600 - 2(65) =470mm

x=e+lflx4 .•

i = 450 + 1/2 (470)

x,;.685mm

Assuming all steel yields:

a= -m + ~m 2 +.2n m=x-d = 685-535 m=150mm Asl

/y X4

n= ----"--

0.85 f'c b

= 1847(414)(471/ 0.85(20.7)(35fJ/ n ~ 58,359 0/

a= -150 +

~150 2 + 2(513S9)

a=223mm

c =a/131 = 223/0.85 c=262mm Check for steel stress: d-e /sl = 600·- . c = 600 535 - 262 f,sl 262 /s1 = 625 MPa > fy (OK)

•

0' C'

e

I

CHAPTER 7- SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDJNG

213

c-d' /!4=600-c

{ = 600 262 - 65 )!4 262 /!4 = 451 MPa > fy (OK)

P, = 0.85f,a b P, = 0.85(20.7)(223)(350) P, = 1,373.3 kN

=1,373,290 N

PROBLEM 7.4

Calculate the nominal axial load capacity of the column shown that can be applied at an eccentricity of 200 mm. Use fc = 20.7 MPa and fy =413.7 MPa.

SOLunON

With reference to the procedure presented in Page 205: X4=d-2d' X4 =450mm

x = e + 1/2(450) x=425mm d=d-d' d=525mm

REINFORCED CONCRETE DESIGN Xc Xc

= d- a/2 = 525- P1c/2 = 525 - 0.425c

Ast = As4 = f (25)2 X 4 Asl = As4 = 1,963 'nun2

Assume compression steel yields: j,4 = 413.7 MPa

[{sl

d-e = 600-] c

/s1 = 600 525 -c c [Cc = 0.85/ca b] Cc = 0.85(20.7)(P1 c)(400)

Cc =5982.3 c

[T= As1/s1] T = 1,963 X ,600 525 - c c

525 -c T= 1,177,800

c

. [~ =As4/s4] ~

= 1,963(413.7)

~ = 812,093 N · [LFv=OJ. P, = Cc + c.- T

)1

'

t

~1·.

t

1

\ · \.

l

525 ..:"c P, = 5,982.3 c + 812,0~ -1,177,800----Lc

[LMr= 0] Cc Xc + ~ X4 - P, X = 0 (5982.3 c)(525- 0.425c) + 812,093(450) - (5,982.3 c + 812,093- 1,177,800

525

c

- c )(425) = 0

7390 c- 5.98 c2 + 859,863- 5,982.3 c- 812,093 + 1,177,800 525 -c = 0 c 1,407.7 c2- 5.98 c3 -1,130,030 c + 618,345,000 = 0 1407.7 c·- 5.98 c2 + 47,770 + 1,177,800

525

c

-c

=0

CHAPTER 7- SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

215

Solving for c by trial and error: After successive trials, c = 403 mm Steel stress:

d-e ./sl = 600--

c

= 600 525- 403 403

./s1 = 181.6 MPa
c = 600 403-75 403 js4 = 488 MPa > fy (OK)

Thus,

525-c

P,. = 5,982.3 c + 812,093-1,177,800-c P" = 2,866,405 N Pu = 2,866.4 kN

The student can now imagine how tedious the solution is if all steel does not yield and can now realize the importance computer programs or the interaction diagram.

Using Interaction Diagram Interaction diagrams are
Using the Interaction Diagram: y = 450/600 y = 0.75 e/h = 200/600 ejh = 0.333 Pg =As/ Ag

- 2(1963) pg - 600( 400) pg = 0.016

216

REINFORCED CONCRETE DESIGN 50

INTERACTION DIAGRAM

f c =3 ksi (20.7 MPa)

45

fy y

=60 ksi (413.7 MPa) =0.75 ---- n____.,

ll_rh---1 1

40

•• I :• •• i :

35

b •

",.0==

10

~,.~ 0

1

2

'= 3 " 4

5

6

7

9

0

(W,JAg)(elh), MPa

Figure 7.2: Interaction diagram

From the diagram shown:

~Pn = 8.2 MPa Ag ~

P,

= 8.2(600 X 400)

~

P" = 1,968,000 N P., = 1;968 kN p = 1,968 0.7 P, = 2,811 kN n

11

'y

13

4

5

PROBLEM 7.5

Calculate the nominal axial load capacity of the column shown that can be applied at an eccentricity of 200 nun. Use fc = 20.7 MPa and fy = 413.7 MPa.

SOOmm 360mm

e=400mm

SOLUTION

A Ag

[pg= _ s J 2

- {(28) (16) Pg - 500(500) Pg = 0.0394

ejh = 400/500 ejh = 0.80 y = 360/500 y= 0.72

·.

Since there is no available interaction diagram for y = 0.72, let us use the diagrams for y = 0.6 andy= 0.75 (with fy = 413.7 MPa and /r = 20.7 MPa) and interpolate the values obtained.

218

REINFORCED CONCRETE DESIGN

From Figure 7.3:

~Pn

=

4.6 MPa

Ag

From Figure 7.4:

~pn

= 5.8 MPa

Ag

y

~P,jA 8

0.60 0.72 0.75

4.6 X

5.8

By interpolation: X- 5.8 0.72-0.75 4.6- 5.8 0.60-0.75 x =5.56MPa

~Pn = 5.56 MPa Ag

P = 5.56(500x500) 0.70 , P, = 1,985,714 N P, = 1,985 kN 50

INTERACTION DIAGRAM

= = r =o.6o

f c 3 ksi (20.7 M~a) fy 60 ksi (413.7 MPa)

40

l ••••• • I •

r

h

I 1,...___.¢_~

.•••••.

b •

•

'

~n ;,<> _

,!g = 0.03!

:.o=I=

10

Figure 7.3: Interaction diagram for y

= 0.6

CHAPTER 7 -SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

219

Figure 7.4: Interaction diagram for y = 0.75

PROBLEM 7.6 (CE BOARD MAY 2000)

For the spiral column shown: a) Determine the pg in percent, if the eccentricity is 150. millimeters. b) Determine the ratio of the center-to-center spacing of.reinforcement to the column dimension in the direction of bending. c) Using the Interaction Diagrah1, determine the maximum downward load that the column can support.

220

REINFORCED CONCRETE DESIGN

(+PrJAg)(e/h) =+M.J (Agh), ksi

Note: 1 ksi =6.8928 MPa

SOLUTION

A [pg = ---lL] Ag

t(22) 2 x8 Pg t(500)2 .

pg = 0.0155 y=375/500 y = 0.75

e/h = 150/500 e/h= 0.3 From the interaction diagram

~Pn

'A g

=.1.3 ksi x 6.8928 MPa/ksi

~Pn = 8.961 MPa Ag

221

CHAPTER 7- SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

0.75 Pn = f (500)2 X 8.961 Pn =2346kN

INTERACTION DIAGRAM 6.0 J--+-+--1---1---+---+---.4

fc = 4 ksi {27.6 MPa) fy = 60 ksi {413.7 MPa) y = 0.75

2.00

PROBLEM 7.7 (CE BOARD NOVEMBER 2002)

A rectangular column is shown in Figure 09. following loads:

It is acted upon by the

Axial load due to dead load = 450 kN Axial load due to live load= 500 kN Bending moment due to dead load = 134 kN-m Bending moment due to live load = 150 kN-m The column is to be analyzed and designed using the strength method. Use b = 400 mm, h = 600 mm, and y = 0.75. a) Determine the eccentricity of the column, in millimeters, b) Determine the area of th~ required steel reinforcement.

222

REINFORCED CONCRETE DESIGN

Figure 09

SOLUTION P, = 1.4(450) + 1.7(500) P, = 1480kN

[Pn

= pu ] q, p = 1480 n

Pn

0.7

= 21~4.28 kN

M, = 1.4(134) + 1.7(150) M, = 442.6 kN-m [M,

=

Mu]

q, = 442.6

M II

0.7

Mn = 632.28 kN-m Mn 632.28 . . EccentnCity, e = -- = - - Pn 2114.28 Eccentricity, e =0.3 m = 300 mm

~Eccentricity

of the column

223

CHAPTER 7- SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

= 300 = 0.5 h 600 $Pn = 0.7(2114.28x1000) A8 600(400)

!_

~ $Pn

=6.17 MPa

Ag

$Mn

=

A8 h

$Mn A8 h

0.7(632.28x 106 ) [(600)(400)](600)

= 3.07 MPa

INTERACTION DIAGRAM rc = 21 MPa fy = 415 MPa

600

m!< ~ .. Pn

e .1

:=r 1_

From the interaction diagram, pg"" 0.017 A .Pg = Ast g

Ast = 0.017(600 X 400) Ast

= 4,080 mm2 7

Required steel reinforcement

REINFORCED CONCRETE DESIGN

PROBLEM 7.8

Determine the required number of 25 mm bars to be used in two end faces only for the 300 mm x 500 mm rectangular column shown to support the following loads: PoL PLL

MoL=80kN-m = 110 kN-m

=440kN = 490kN

MLL

Usefc = 20.7 MPa and fy = 413.7 MPa

625

m~· E E

~

SOLUTION

P11 = 1.4(440).+ 1.7(490) Pu = 1449kN [p ,

= Puq, ]

P, =

1449 = 2oio kN 0.7

M 11 = 1.4(80) + 1.7(110) Mu=299kN-m

[M, = Mu]

. q,

299 M,=- =427kN-m 0.7

500mm jf-r_ _ 37_5_mm_-----*1

·~.5 mm

225

CHAPTER 7 - SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

M [e= _n]

pn

e=

427 2070

= 0.206 m = 206 mm

efh = 206/500 = 0.412 y = 375/500 =0.75 cjl Pn

= 0.7(2070 X 10 3 )

Ag

500(300)

cjl Pn Ag

= 9.66 MPa = 1.4 ksi

--

From the interaction diagram in Figure 7..5: Ps = 0.032 < 0.06 (OK) As= pgAg As = 0.032(300 x 500) :;: 4,800 mm2

f

(25) 2 N = 4,800

N

= 9.78 say 10 bars .(5 on each side)

0

0.20

0.40

0;60·

0;80

1.00

I .20

Figure 7.5: Interaction diagram

I AO

1.60

1.80

2.00

226

REINFORCED CONCRETE DESIGN

PROBLEM 7.9

Design a square tied column to carry a factored axial load of 2,000 kN and a factored Il10ment of 190 kN-m. Use 25 mm bars to be placed uniformly around the faces of the column. Assume f , = 20.7 MPa and fy = 413.7 M!a.

SOLUTION The size of the column for this condition can be. obtained by assuming an· average compressive stress in concrete under the load P,.. This assumed value must be less ·than 0.85 f , (usually from 0.5f, to 0.6f,). With the column dimension known, the steel ratio can be computed. However, if p • obtained from this assumption is unreasonable, the size can be revised and a new value of p is obtained. Assume average compressive stress as 0.5fc: A = g

_!.y_ 0.5f',

_ 2000x10 3 A g0.5(20.7) Ag = 193,237 mm2 = h2 h =439mm

·

h = 450 mm

62~ (It-'(--=325,____~)1 )~.5

I

E

Try 450 x 450 column M e= _u_

Pu •

E 0

~ II

.c.

190 2000

e=-e=0.095m e=95mm efh = 95/450 efh =0.211 y=325/450 y = 0.722

I __

e = 95 mm

227

CHAPTER 7 -SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

Since ~ere is no available diagram for y diagrams for y = 0.6 andy = 0.75

Pn = pu

•

Pn=

=

0.722, let us use the available

fh : 4,.

¢

2000 =2857kN 0.7 I

+Pn = 0.70(2,857 x 10 3 ) Ag 450(450) +Pn Ag

-----

= 9.876MPa ·= 1.433 ksi 7.0

IN11l&ACI10N

I 'l-+-of:oi'llfa~

3.0

+·

++-t--HH

, •.;,=).018-· :z.o

q

0.20

0.40

0.60

0.10

1.00

l.lO

£&. )(!. .&,kll A II A 11 1

From the diagram, pg = 0.018

1

1.40

1.60

1.10

1.00

228

REINFORCED CONCRETE DESIGN

From the diagram, p1 ,;., 0.016

x-0.016 0.722-0.75 = 0.6-0.75 0.018- 0.016 X = 0.01637 = Pt

As = Pg Ag = 0.01637(450 X 450) A.=3315mm2 f (25)2 N = 3315 N= 6.75

y 0.60 0.722 0.75

Pt O.Ql8 X

0.016

Since the bars must be placed uniformly around the faces, use 8-25 mm bars with 3 bars in each face. Computer calculation for this column (with 8-25 nun bars and e = 95 mm) yields the following results: Pn = 3,089kN Pu = 2162.3 kN > 2000 (OK) Mn = 293 kN-m M,. = 205.1 kN-m >190 (OK)

Co!IIJ'IIf,, 1•1 <~,,u1111' ti11 , ottol'lc ntoii/JI'r, lilt ' '" aila/J!c at GERTC You
CHAPTER 7 -SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

229

AXIAL LOAD PLUS BENDING IN BOTH AXES (BIAXIAL BENDING) In most cases, columns are subject to bending in both axes, or biaxial bending. This is t:Jle usual case of corner columns in buildings where beams or girders frame into the column from both directions only . Biaxial bending on circular columns would not be a problem due to polar symmetry of the column. If there is bending moment about both x and y axes, the biaxial moment and eccentricity can be computed from the following formulas: ,-------------~======~------------~ 2

M,=~(M 11 xf+(M 11 y) c=

Eq.7-6

~(e,)2 +(ey) 2

Eq. 7-7

For column shapes other than circular ones, the analysis would be as shown in the figure below. Y

N.A.

\'"

cc)

\ \ T3

\\/

c 0.003

~ JM

REINFORCED CONCRETE DESIGN

One could think how difficult to solve for Pu using the statics equation as presented in Problem 7.4. Such solution would lead to correct answer, but the mathematics involved is so complicated that the method is not a practical one, but with the aid of computer such is not a problem.

BRESLER EQUATION

A method published by Professor Boris Bresler in 1960 relates the desired value of 4lPu under biaxial loading (ex and ey) to thre~ other P, values. The equation is: 1 1 1 1 -=-+--pn Pnx Pny pno

Eq. 7-8

where: P,x

= axial load capacity of the column for eccentricity ex with ey = 0 P,y = axial load capacity of the column for eccentricity ey with ex = 0 P, 0 = pure axial capacity of the column Eq. 7 ~ 9

The Bresler equation works well as long as P" is at least as large as 0.1P,o. Should P, be less than 0.1P""' it is satisfactory to neglect the axial force completely and design the section as a member subject to biaxial bending only.

CHAPTER 7- SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

231

ILLUSTRATIVE PROBLEM PROBLEM 7.10

Calcu}ate the permissible load capacity P11 of the short tied column shown if ex= 200 mm and ey = 100 mm. Use [ c = 20.7 MPa and fy = 413.7 MPa.

SOLUTION pg=

A -;t g

1!.(28) 2 (8)

= ~00(375) Pg = 0.022

Pg

Using theinteraction diagram: For eccentricity ex: (Bending about Y-axis) y = 450/600 y = 0.75 ex= 200 mm ejh = 200/600 ejlz = 0.333

232

REINFORCED CONCRETE DESIGN

·'

o

0.20

o.40

o.60

o.ao

hOO

tao

.&x!.-~,bl A1

+Pnx Ag

~

= 1.28 ksi

+Pnx = 8.823 MPa Ag

= 8.823(600 X 375)

p

0.7 Pnx = 2,835,918 N P,.x =2,836 kN !IX

For eccentricity ey: (Bending about X-axis) y = 225/375 y =0.6 ejh = 100/375 ejh = 0.267

A~

uo

1.60

uo

i:'oo

233

CHAPTER 7 - SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING J.O

, U'l liiKA\iUUI'I·

.r. • 3 kll (20.7 IO'l>

Ia'

~•

6:0

I

'j a

.6 0ki1(4t).?'IO'a) 0.60

-.-,--.-:

'T : ·1"' I" ~

5.0

( ·

,,(~

0.00

0.15 l.l

0.07 O.DJ 1.00 l\00 1.01 t.g, 1 17 1.24 ·J.ll )')' )I

P,

·'

... ~.. i ·~

4.0

·A,.

.!!a.kll

.· 1e/h 3,0

,

=0~267

r

I

'

:z.o

iPg= 0

O.:ZO

0.40

~.~2

0.60

0.80

AA

1.00 X~ •

1

jlj

J.:ZO

.f!L. bl A jlj 1

~Pny = 1.35 ksi = 9.305 MPa Ag

p = 9.305(600 X 375) ny 0.7 P,y = 2,990,893 N P,v = 2,991 kN P,o = 0.85 f , Ag + A.fy P,0 = 0.85(20.7)(600 X 375) + P,o = 5,996,768 N Pno = 5,997kN 1

1

1

1

P,

P,_,.

Pill/

P,IO

1

1

f

{28)2 X 8 {413.7)

-=-+--1

1

-= - +----P,, 2,836 2,991 5,997 Pn = 1,922 kN P, = cj> P" = 1345.4 kN

1.40

1.60

1.80

:Z.OO

234

REINFORCED CONCRETE DESIGN

SUPPLEMENTARY PROBLEMS PROBLEM 7.11

Calculate the nominal axial load capacity of the . column shown that can be applied at an eccentricity of 80 mm. Usefc = 20.7 MPa andfy = 413.7 MPa. SSOmm

E E

g

Pn . ®

v

PROBLEM 7.12

Repeat Problem 7.11 withe= 150 mm.

PROBLEM 7.13

Repeat Problem 7.11 withe= 450 mm.

PROBLEM 7.14

Repeat ~roblem 7.11 usingfc = 27 MPa,fy = 345 MPa and e = 300 mm.

PROBLEM 7.15

In Problem 7.11, calculate the balanced eccentricity eb and balanced loading P~n,.

PROBLEM 7.16

Repeat Problem 7.11 usingfc = 27 MPa,fy = 345 MPa and e = 80 mm.

CHAPTER 7 - SHORT COLUMNS SUBJECT TO AXIAL LOAD AND BENDING

235

PROBLEM 7.17

Calculate the n~minal all:ial load capacity of the column shown that can be applied at an eccentricity of 150 mm. Use fc = 20.7 MPa and fv = 413.7 MPa.

PROBLEM 7.18

Repeat Problem 7.17 withe= 600 nun. Find also the balanced loading Pbn·

PROBLEM 7.19

Calculate the nominal axial load capacity of the spiral column shown that can be applied at an eccentricity of 250 mm. Use fc = 20.7 MPa and fy = 413.7 MPa.

60omm

236

REINFORCED CONCRETE DESIGN

PROBLEM 7.20

Determine the required number of 28 mm bars to be distributed uniformly along each side of a 450mm x 450mm column. The column is to carry a factored load of 1,180 kN and a factored moment of 295 kN-m. Used' ;., 62.5 mm. Assume [c = 20.7 MPa and fy =413.7 MPa. ·

CHAPTER 8- LONG COLUMNS

237

Chapter 8 Long Columns · SLENDERNESS EFFECTS IN COLUMNS

The slenderness of columns depends on its unsupported length and the geometry of its section. As the slenderness increases, the tendency that it will buckle also increases. To visualize the effect of slenderness, let us imagine a stick (say wire or broomstick) with the same cross-sectional area but with varying length, .being compressed until it breaks as shown in Figure 8.1.

Figure 8.1: Stick of the same material and cross-sectional area subjected to different compressiv!'! force P until it breaks

Obviously, Figure 8.1 (a) and Figure 8.1 (b) would have larger value of P until it fails by crushing. This is the situation of a short column. However, Figure 8.1 (c) will fail by lateral buckling due to its length (which increases the slenderness) 'and the value ofP would be lesser than that of(a) and (b). According to Section 5 .10.10.1 of NSCP, design of compression members shall be based on forces and moments determined from analysis of the structure. Such analysis should take into account influence of axial loads and variable moment of inertia on member stiffness and fixed-end moments, effects of

238

REINFORCED CONCRETE DESIGN

deflections on moments and forces, and the effects of duration ofJoads. In lieu of this procedure, the slenderness effects in compression members may be evaluated in accordance with the approximate procedure presented in Sec. 5.10.11.

APPROXIMATE EVALUATION OF SLENDERNESS EFFECTS (SECTION 5.10.11) Unsupported Length of Compression Members

Unsupported length lu of a compression member should be taken as the clear distance between floor slabs, beams, or other members capable of providing lateral support for that compression member. Where column capitals or haunches are present, unsupported length should be measured to the lower extremity of capital or haunch in the place considered.

·effective Length Factors (5.10.11.2.1 & 5.10.11.2.2)

For compression members braced against sidesway, effective length factor k should be taken as 1.0, unless analysis shows that a lower value is justified. For compression members not braced against sidesway, effective length factor k should be determined with due consideration of eff~cts of cracking and reinforcement on relative stiffness, and should be greater than 1.0.

Radius of Gyration

Radius of gyration r may be taken equal to 0.30 times the overall dimension in the direction stability is being considered for rectangular compression members, and 0.25 times the diameter for circular compression members. For other shapes, r may be computed for the gross concrete section. For rectangular compression members: r

= 0.3h

Eq. 8-1

where h =overall dimension in the direction stability is being considered For circular compression members:

r= 0.250

Eq. 8-2

CHAPTER 8- LONG COLUMNS

239

CONSIDERATION OF SLENDERNESS EFFECTS

According to Section 5.10.11.4.1 of the Code, for compression members braced against sidesway, effects of slenderness may be neglected when k lu < r

_ 34 12

Mlb M2b

where M1b is the smaller factored end moment (positive if bent in single curvature) and M2b is the larger factored end moment. For compression members not braced against sidesway, effects of slenderness may be neglected when klu < 22 r

For all compression members with kl, I r > 100, an analysis as defined in Sec. 5.10.10.1 (See Page 237) should be made. ·

Braced and Unbraced Frames

As a guide in judging whether a frame is braced or unbraced, the Commentary on ACI 318-83 indicates that a frame may be considered braced if the bracing elements, such as shear walls, shear trusses, or other means resisting lateral movement if a storey, have a total stiffness at least six times the sum of the stiffnesses of all the columns resisting lateral movement in that storey.

Alignment Charts

The ACI Committee 441 has proposed that k should be obtained from the Jackson and Moreland alignment chart as shown in Figure 8.2. To use this chart, a parameter 'VA for end A of column AB, and a similar parameter \jiB must be computed for end B. The parameter 'V at one end of the column equals the sum of ·the stiffnesses (.L: EI I L) of the column meeting at that joint (including the column in question), divided by the sum of all the stiffnesses of the beam meeting at that joint. Once \j/A and 'VB are known k is obtained by placing a straightedge between 'VA and 'VB· The point where the straightedge crossed the middle monograph is k. I

\jl

LEII L___ of columns = -=__:_ _ .L:EIILofbeams

Eq. 8-3

240

REINFORCED CONCRETE DESIGN ljJ = oo

fA

for pinned ends and 1.0 for fixed ends

;a

k 1.0 0.11

'

k

CD

50.0 10.0 5.0 3.0 2.0 lQ.O

0.8

0.7

8.0

1.0 0.8

6.0

4.0 3.0

0.6 0.4

2.0

0.3 0.6

0.2 1.0 0.1

o.5

0

0

BRACED FRAMES (a)

UNBRACED FRAMES (b)

Figure 8.2: Alignment chart

For columns for which the slenderness ratio lies between 22 and 100, and therefore the slenderness effect on load-carrying capacity must be taken into account, either an elastic analysis can be performed to evaluate the effects ~f lateral deflections · and other ·effects producing secondary stresses, or an approximate method based on MOMENT MAGNIFICATION may be used.

MOMENT MAGNIFIER METHOD

The effect in slenderness in long columns may be approximately accounted for in design by empirically increasing the factored design moment. According to Section 5.10.11.5.1 of the Code, compression members should be designed using the factored axial load P, from a conventional frame analysis and a magnified factored moment Me defined by

Me= ov M2b + o.M2s

Eq. 8-4

211

CHAPTER 8- LONG COLUMNS

where M1b

Mw

= value of smaller factored end moment on a compression member due to the loads that result in no appreciable sideways, calculated by conventional elastic frame analysis, positive if member is bent in single curvature, negative if bent in double curvature. = value of larger factored end moment on compression member due to loads that result in. appreciable sidesway, calculated by conventional elastic frame analysis. According to Sect. 5.10.11.5.4, for use in Eq. 8-4 M2b ~

Pu(15 + 0.03h)

where h is the column dimension in the direction of bending. M2s = value of larger factored end moment on compression member due to

loads that result in appreciable sidesway (such as wind, earthquake, and other lateral loads), calculated by conventional elastic frame analysis. According to Sect. 5.10.11.5.4, M2s

~

P,(15 + 0.03h)

where h is the column dimension in the direction of bending. 8b

= moment

magnification factor that takes into account the effect of member curvature in a frame braced against sidesway and:is equal to

emp

->1 .0

Eq. 8-5

1--u

$Pc 8s = moment magnification factor that takes into account the lateral drift of a column caused by lateral and gravity loading the frame not being braced against sidesway and is equal to Eq. 8-6

and Eq. 8-7

REINFORCED CONCRETE DESIGN

242

"'.P, and "'.Pr are the summations for all columns in a story.

For frames not braced against sidesway, both Ob and o, shall be computed. For frames braced against sidesway, o, shall be taken as 1.0. In calculation of P.., k shall be computed according to Sec. 5.10.11.2.1 for Ob and according to Sec. 5.10.11.2.2 for Os (See Page 238) In lieu of a more accurate calculation, EI in Eq. 8- 7 may be taken either as

Eq. 8-8

or conservatively Eq. 8-9

·where f3d

= the ratio of maximum factored dead load moment to maximum total factored moment (always positive), where the load is due to gravity effects only in the calculation of P, in Eq. 8 - !), or the ratio of the maximum factored sustained lateral load to • the maximum total factored lateral load in that story in the calculation of Pc in Eq. 8 - 6. f3d

Max. factored dead load moment Total factored moment

= ------------

Eq. 8-10

lg

= moment of inertia of gross concrete section about centToidal axis, neglecting reinforcement lse · =moment of inertia of reinforcement about centroidal axis of member cross section · Ec = modulus of elasticity of concrete, MPa

Ec = 4700

JTc

Eq. 8-11

E, = modulus of elasticity of reinforcement= 200,000 MPa In Eq. 8-5, for members braced against sidesway and without transverse loads between supports, there is a modification factor C, that relates the actual moment diagram to ai:J. equivalent uniform moment diagram. For braced

CHAPTER 8- LONG COLUMNS

243

frames without transverse loads, it can vary from 0.40 to 1.0. The value of C'" may be taken as M1b Cu = 0.6 + 0.4--, but not less than 0.4.

Eq. 8-12

M2 b

For all other cases, Cu shall be taken as 1.0.

According to Section 5.10.11.5.4, the Ratio M11>/ M2b in Eq. 8 - 12 shall be determined by either of the following: (a) When computed end eccentricities are less than (15 + 0.03h) mm, computed end moment shall be used to evaluate M1b j M.2[>.

(b) If computations show that there is essentially no moment at both ends of a compression member, the ratio M1h / M21r shall be taken equal to one.

MINIMUM ECCENTRICITY WHEN SLENDERNESS IS TO BE CONSIDERED According to Section 5.10.11.5.4, if computations show that there is no moment at both ends of a braced compression member or that computed end eccentricities are less than (15 + 0.03h) mm, M2~ in Eq. 8- 4 shall be based on a minimum eccentricity of (15 + 0.03h) mm about each principal axis separately. If computations show that there is no moment at both ends of a cop1pression member not braced against sidesway or that computed end eccentricities are less than (15 + 0.03h) mm, M2s in Eq. 8 - 4 shall be based on a minimum eccentricity of (15 + 0.03h) mm about each principal axis separately.

MOMENT MAGNIFIER o FOR BIAXIAL BENDING For compression members subject to bending about both principal axes, moment about each axis shall be magnified by 8, computed from corresponding conditions of restraint about that axis.

244

REINFORCED CONCRETE DESIGN

ILLUSTRATIVE PROBLEM PROBLEM 8.1

A square column having an unsupported length of 6 m is used in a frame braced against sidesway (k "" 1.0). The column is bent in single curvature and subjected to factored end moments of 80 kN-m at the top and 60 kN~m at the bottom. Find its minimum dimension such that slenderness may not be considered in the analysis. SOLUTION

Mtb = smaller factored end moment= +60 kN-m M2b = larger factored end moment = 80 kN-m • So that slenderness may not be considered: k lu < _ Mlh 34 12 r

M2b

1 (6000) ' = 34 -12(60/80) r

1(6000) = 25 r r= 240 = 0.3h

h=800mm

PROBLEM 8.2 (CE BOARD NOVEMBER 1997)

A rectangular tied concrete column has dimensions of300mm x 380mm. The column length is 4.5 m and is to be used in a frame braced against sidesway (the effective length factor k can be taken as 1 and EI = 34 MN-m 2) . The column is loaded in single curvature by the ultimate (factored) moments of 110 kN-m at its top end and 120 kN-m at its bottom end. The column carries factored axial load due to dead load of 150 kN and 350 kN due to live load. Calculate the magnified factored moment Me. SOLUTION

M2b = larger factored end moment = 120 kN-m Mtb =smaller factored end moment= +110 kN-m Note: Mt b is positive because it is bent in single curvature

Mtb/ Mzb = 110/120 Mtb/ M2b = 0.917

245

CHAPTER 8- LONG COLUMNS

Radius of gyration = 0.3h Note: This problem did not mention on which side the moments were applied, but practically for columns subject to bending on one side, h should be bigger than b. Thus, for this problem, let us assume h = 380 mm r = 0.3(380) r= 114

L, =4.5m L, =4500m

= 1(4500)

kL,

r

114

kL,

= 39.47

r

34-12

Mlb M2b

= 34 -12(0.917)

34 - 12

Mlb M2b

= 22.996

Since kL, > 34 -12 r

M25=0

o. = 1.0

Mlb , M2b

slenderness must be considered. (Sect. 5.10.11.4.1) ,

.

(because it is not given) (Sect. 5.10.11.5.1)

Since the given axial loads were already FACTORED loads, then P, = 150 + 350 P, =500kN rr:2

EI

P, = - - -

(kL,)2

EJ=34MN-m2 EI = 34 x 1012 N-mm2 2 12 1t (34x 10 ) p = --'----::--'( . [l( 4500)] 2 = 16,571,188 N P, = 16:,571 kN

246

REINFORCED CONCRETE DESIGN M1 b em= 0.6 + OA--

M2b

= 0.6 + 0.4(0.917)

ell/= o.9668

0.9668 8b = - -·'"""=5o=-=o:---

1 - - - -0.7(16,571)

,. ,\

J1

)

Db= 1.0103

I(

Me = 1.0103{120) Me= 121.24 kN-m

ij

.I PROBLEM 8.3 Repeat Problem 8.2 if wind loads cause an axial load of 130 kN and a moment of 100 kN-m to the column. SOLUTION M2s = 0.75(1 .7 Wind Load) M2s = 0.75(1.7(100)] M2s = 127.5 kN-m P,. = 0.75(1.4Fot + 1.7PLL + 1.7PWL)

(Section 5.9.2.2, See Page 21)

(Section 5.9.2.2, See Page 21)

Where 1.4Pot + 1.7PL.L =Factored axial load 1.4Pot + 1.7PLL = 150 + 350 = 500

P,.

= 0.75(500 + 1.7(130)]

P,.

= 540.75 kN

em &b = 1- Pu

~pc

0.9668 Ob = --"::":':":=-==--1_ 540.75 0.7(16,571)

ob = 1.014 Me = Db M2b + Os M2s Me= 1.014(120) + 1(127.5) Me= 249.18 kN-m

l '1 )

'

CHAPTER 8- LONG COLUMNS

247

PROBLEM 8.4

Using the results in Problem 8.3, select the steel area for the column using b • 300 mm, h = 380 nun, and d' = 47.5 mm with bars on two faces of the column only. Use fv = 413.7 and fc = 20.7~ MPa. SOLUTION

M, =Me= 249.18 kN-m P, = 540.75 kN M

e=-" pu

-249.18 -540.75 = 0.461 m e =461 mm !.. = 461 h

380

!.. = 1.213 h

285 y= 380 y

= 0.75

P,= Pu

cp

540.75 0.7 P, =772.5kN

cpPn = 0.7(772.5x 1000) 300(380)

Ag

cp Pn = 4.74 MPa Ag

From the interaction diagram, pg = 0.04 < 0.06 (OK) As= pgAg = 0.04(300)(380) A.=4560mm2 Using 25 mm bars: f (25)2 N =4560

N

= 9.29 say 10 (5 in each side)

248

REINFORCED CONCRETE DESIGN

50

45

INTERACTION DIAGRAM f c = 3 ksi (20.7 MPa) fy =60 ksi (413.7 MPa) y =0.75 h

40

1'1

35

b •

•• ••

yh

••• ••

PROBLEM 8.5

The column shown is subject to an axial dead load of 265 kN and an axial live load of 440 kN. The frame is braced against sidesway and the·column is bent in single curvature with equal end moments of MoL = 160 kN-m and Mtt = 190 kN-m. Use fy = 20.7 MPa and f r = 413.7 MPa. Investigate the adequacy of the column for an unsupported length of a) 3 meters, and b) 6 meters. Assume k = 1.

CHAPTER 8- LONG COLUMNS

SOLUTION

f

As =

(32)2 X 10 As = 8,042 mm 2

8,042

= 375(500)

Pg

pll = 0.043

a)

Lu=3m r = 0.3(500)

r= 150mm

= 1.4(160) + 1.7(190)

M1b

= 547 kN-m M2b = 547kN-m M1b/M2b = 1 k Lu = 1(3000)

(positive for single curvature)

M1b

150

r

kLu = 20 r

. M 34 - 12 ____!!!_

= 34 -

12(1) = 22

M2b

kL

Mtb

r

M2b

·

·

Since .- u < 34 -12· -,slenderness may be neglected

= 1.4(265) + 1.7(440) P, = 1,119 kN P,.

P,= pu

+

= 1,119

p

0.7 P,= 1599kN II

Mu

= M2b = 547 kN-m M

e=-u Pu 547 1,119

e= -

250

REINFORCED CONCRETE DESIGN

e = 0.489m e =489mm ejh = 489/500 ejh = 0.978

375 y= 500

y = 0.75

From the interaction diagram,

~ Pn Ag

= 6 MPa

0.7P,. = 6(375)(500) P, = 1,607,143 N P, =1,607 kN > 1,599 (adequate) 50

INTERACTION DIAGRAM

f c =3 ksi (20.7 MPa) fy = 60 ksi (413.7 MPa) y =0.75 h

45

40

I"

35

b :

•

:

'I • I :

yh

i

:

ri"

b)

Lu = 6 m kLu r:.

= 1(6000)

kLu

= 40 > 34-12 Mtb

r

150 ,

.

M2b

(Slenderness must be considered) .

211

CHAPTER 8- LONG COLUMNS

Me

= ob Mzb + os M2s M2s=O Os = 1.0 Mzb = 547 kN-m but not less than M = P,(15 + 0.03h) M = 1,119[15 + 0.03(500)]/1000 = 33.57 kN-m (OK)

Use M2b = 547 kN-m ob=

em

-~-

1- pu

$P, Mlb 0.6 + 0.4-M2b c,/1 = 0.6 + 0.4(1) Cm = 1.0 C111

P, P"

_

-

=

1.4(265) + 1.7(440)

= 1,119 kN n 2 EI

P,=--

(kLu )2

(E, I g _ / 5)_ + £_ 5 I se £1=-___:;:._ _ 1+~d

. bh 3 Ig=u 3

=

I

375(500) 12 18 = 3,906,250,000 mm4 8

E, = 4,700 ..{j'; E, = 4,700 .J20.7 E, = 21,384 MPa

Es = 200,000 MPa Ise =LAs y2 (about centroidal axis) As =

f

(32)2 X 5

As = 4,021 mm2 (in each row)

y = 375/2 y= 187.5mm

252

REINFORCED CONCRETE DESIGN

lse

= 4,021(187.5)2 X 2

I.. = 282,726,563 mm4 A

Max. factored dead load moment Total factored moment

_

I-'d-

Max. Mu oL = 1.4(160) = 224 kN-m M, = 1.4(160) + 1.7(190) M, =547 224

J3d = 547 J3d = 0.4095 EI = (21,384 X 3,906,250,000 I 5) + 200,000(282,726,563) 1 +0.4095

EI = 51,969,891,876,552 N-mm2 Pc =

rt

2

(51,969,891,876,552)

(1 X 6000) 2 = 14,247;841 Pc = 14,248 kN ~b

1 = ---::-:-:-=----

~b

=1.126 > 1 (OK)

1-

1,119 0.7(14,248)

Me= 1.126(547) + 1(0) M.- = 615.922 kN-m Let us now investigate the adequacy of the column with this modified moment: M, =Me= 615.922 kN-m P, =1,119 kN M

e=-u Pu 615.922 1,119 e =0.550 m = 550 nun p

p,:::

PII

...E..

•

119 = 10.7 ' = 1 599 kN I

"!

.253

CHAPTER 8-LONG COLUMNS

;,,

ej h = 55Q.f500 ejh=1.1

'·

y = 375/500 = 0.75

From the interaction diagram, $ pn = 5.5 MPa Ag 0.7P, = 5.5(375 X 500) P, = 1,473,214 N P, = 1,473 kN < 1,599 (not adequate) 50 45 40 35

INTERACTION DIAGRAM f c 3 ksi (20.7 MPa) fy =60 ksi (413.7 MPa) y = 0.75 h

=

I' I•

rh

•I

'I

• • b • •• I ••• • i •

Comment: Computer calculation shows that the column will be adequate with 6-32 mm bars on each side, for a total of 12 bars, with Pn = 1,670 kN. However, with these steel requirements, the author suggests to increase the size (specially h) of the column to for reasons of economy.

254

REINFORCED CONCRETE DESIGN

PROBLEMS. 6

Oesign the steel requirements for a 7.5-m, 600 mm x 600 mm square tied column ·bent in single curvature in a braced frame with 1J1 value assumed equal to 1.0 at one end and 2 at the other end. The column is used to carry the following loads: Axial dead load = 800 ,k N Axial live load = 88Q kN Dead load moment = 135 kN-m Live load moment = 175 kN-m Use f, = 20.7 MPa, Jy = 413.7 MPa and place the bars in the two end faces orily with d' = 75 mm. SOLUTION

P, = 1.4(800) + 1.7(880)

Pu = 2,616 kN M2b =1.4(135) + 1.7(175) . M2b = 486.5 kN-m E E

M1b/M2b= 1

~

34 -12 Mtb = 34 -12(1) M2b

34-12 Mtb = 22 M2b

Value of k, from the alignment chart, k = 0.82

r =0.3h :;: 0.3(600) r=180mm k lu = 0.82(7500) r 180 klu = 34.17 > M-12 Mtb r

Slenderness must be considered

M2b

M2b = 486.5 kN-m but not less than Pu(15 + 0.03h) = 2,616[15 + 0.03(600)]/1000 P,(15 + 0.03h) = 86.328 kN-m

M1b =.M2b =+486.5 kN-m

255

CHAPTER 8- LONG COLUMNS

jA

k 1.0

tB co

!50.0 10.0 5.0 3.0 2.0 1.0 0.8 0.6 0.4

0.3 0.2 0.1 0.5

0

BRACED FRAMES

Since the steel area is not known yet, EI may be computed conservatively as: (Section 5.10.11.5.2) Ec Ig /2.5

EI = --"----1 + 13d Ec = 4,700 ..jJ';

E,. = 4,700 .J20.7 Ec = 21,384 MPa

256

REINFORCED CONCRETE DESIGN

I = 600(600)

3

12

g

I8

= 10.8 x 109 mm4

~d

= Max. factored dead load moment Total factored moment Max. factored dead load moment= 1.4(135) Max. factored dead load moment = 189 kN-m

Total factored moment= 1.4(135) + 1.7(175) Total factored moment= 486.5 kN-m 189 ~d = 486.5 ~d = 0.3885 9 EI = 21,384(10.8 X 10 ) I 2.5 1 + 0.3885 EI = 66,531,422,398,271 N-mm2

Pc =

n 2 (66,531,422,398,271)

--'--------=--_:_

[0.82(7500)] 2 Pc = 17,361,063 N Pc = 17,361 kN 1 o,, = ---::-:;-::-:;-1-

&,,

2,616 0.7(17,361) = 1.274

Me = o, M2, + 8. M2s Me= 1.274(48q.5) + 0 Me=;' 619.801 kN-m Design the column with M, = 619.8 kN-m and P, = 2,616 kN

M e=-u

pu

619 8 e= · = 0.237 m 2,616 e=237mm ejh = 237/600 ejh = 0.395 y = 450/600 y = 0.75

257

CHAPTER 8- LONG COLUMNS

Pn"' Pu . cj>

p "' 2,616 71

0.7

J!n "'3737.14 kN c!>Pn _ 0.7(3737.14x 10 3 ) Ag cj> Pn

600 2

"' 7.27 MPa

Ag 50

INTERACTION DIAGRAM f c 3 ksi (20. 7 MPa} fy- 60 ksi (413.7 MPa) y- 0.75

45

't .I

II'

40

yh

.I

b :

I

:

:

i

:

•

35

•

~n ,\)

= 0.1)11

:.

:.of==

0

(+P,/'\ )(Bih),

From the interaction diagram, p8 = 0.016 A.= p8 A8 A. = 0.016(600 X 600) A. = 5,760 mm2 Using 25 mm bars: t ' (25)2 N = 5,760 N

=11.7 say 12 (6 on each side)

MPa

258

REINFORCED CONCRETE DESIGN

SUPPLEMENTARY PROBLEMS PROBLEM 8.7

The column shown has an unsupported length of 8 m, and subjected to moment along the 600 mm side. Assume f.- ~ 28 MPa and fy = 345 MPa. The column is use in a frame braced against sidesway and is bent in single curvature. Calculate the value of M ... Po= 1200 kN = 900 kN

PL

.600 mm

Mo = 120 kN-m ML = 160 kN-m

PROBLEM 8.8

The column shown is 5.5 m long and is part of a braced frame. The column is braced against sidesway with k factor of 1.0. Is the column satisfactory to support a P11 of 885 kN and an Mnx of 200 kN-m? Assume !3d= 0.40, fc = 20.7 MPa, andfy ='413,7 MPa.

E

E 0 0

v

CHAPTER 9 • FOOTINGS

259

Chapter 9 Footings DEFINmON

Footings are structural members used to support columns or walls and transmit their load to the underlying soils. Reinforced concrete is the most suited material for footing for reinforced concrete and structural steel buildings, walls, towers, bridges, and other structures. ~ince

the bearing capacity of soils is normally low (usually less than 400 kPa), and the load from a column or wall is large (usually greater than 1000 kPa), the footing spreads the column or wall pressure to the soil by providing bigger bearing area, thus reducing the bearing pressure within permissible values.

TYPES OF FOOTINGS

The common types of footing are the wall footing, isolated or single-column footing, combined footing, raft or mat, and pile caps. , 1. A wall footing, is a continuous strip of concrete that supports a bearing wall. · 2. An isolated or single-column footing, is a square, rectangular, or circular slab of concrete that supports an individual column. These are widely used for columns with light load and are not closely spaced. 3. A combined footing is a longer rectangular slab strip that supports two or more individual columns. This type might be economical where two heavily loaded columns are so spaced that when designed for isolated footing would run into each other. Isolated footings .are usually square or rectangular and, when used for columns located right at the property line, would extend beyond those lines. The footing for such a column can be combined with an interior column to fit within the property line. 4. A floating, raft, or mat foundation is a single thick mat or slab that supports the entire structure. This kind of foundation is used where soil strength is low or where column loads are large but where piles or caissons are not used. For these types of footings, the excavations are deep. The goal is to remove an amount of earth approximately equal to the building weight.

260

REINFORCED CONCRETE DESIGN

5.

Pile caps are slabs of reinforced concrete used to distribute column loads to group of piles.

Wall Footing

Mat or Raft Foundation

Columns

Pile Cap

Figure 9.1: Types of footing

CHAPTER 9- FOOTINGS

261

PERMISSIBLE SOIL PRESSURES, qa The allowable soil bearing capacity q" to be used in the design of footing can be obtained by the principles of soil mechanics through the services of a soils engineer. This can be derived on the basis of test borings, load tests, and other experiL11ental investigation.

In the absence of soil investigation, the building code of the Philippines provide certain approximate allowable bearing pressures that can be used for the type of soil and soil conditions. Table 9.1: Allowable Soil Pressure, q, Source: National Building Code of the Philippines/ Table 7.04-(A) Classification of Material

Minimum depth of footing below adjacent virgin ground

1

Value permissible if footing is at minimum depth

2 Meter

3 Feet

kg/m

2

kPa

Increase in value for each 1 m of depth that footing is below minimum depth 4 Kg/m

2

kPa

Maximum value 5 kg/m

2

kPa

Compact coarse sand

0.6

2

20% ultimate crushing strenath *7,500 *75

*5,000

*50

20% ultimate crushing strenath 40,000 400

Compact fine sand

0.6

2

*5,000

·so

*3,300

*33

40,000

Loose sand Hard clay or sanoy clay Medium stiff clay or sandv clav Soft sandy clay or clay Compact inorganic sand and silt mixtures Loose inorganic sand . silt mixtures Loose organic and silt mixtures and muck

0.9

3

*25

*16

15,000

150

0.6

2

*1,600 13,30 0

133

40,000

400

0.6

2

3,300

33

30,000

300

0.20 Rock

0.3

1

0

0

400

0.9

3

*2,500 20,00 0 10,00 0 5,000

50

830

8.3

10,000

100

0.6

2

5,000

50

3,300

33

20,000

200

0.9

3

2,500

25

1,600

16

5,000

50

0

0

0

0

0

0

200 100

• These values are for footing 300 mm in width and may be increased in direct proportion to the width of the footing to a maximum of three times the designed value

262

REINFORCED CONCRETE DESIGN

Table 9.2: Allowable Foundation Pressure Source· NSCP Table No 7-B Allowable Foundation Pressure 2 kN/m (3)

Lateral Bearing (kN/m 2 of depth) below natural

/m

Lateral Sliding (1)

1. Massive Crystalline Bedrock

200

190

Coefficien t (5) 0.70

2. Sedimentary and Foliated Rock

100

60

0.35

3. Sandy Gravel and/or Gravel (GW & GP) 4. Sand, Silty Sand, Clayey and Clayey Gravel and Clayey Gravel (SW, SP, SM, SC, GM and GC). 5. Clay, Sandy Clay. Silty Clay and Clayey Silt (CL, ML, MH, and CH)

100

30

-

75

25

0.25

-

50

15

Classes of Material (1)

Grade (4)

Resistant KN/111 2 (6)

7

(1) Lateral bearing and lateral sliding resistance may be combined For soil classifications OL, OH and PT (i.e. organic clays and peat), a foundation investigation shall be required. (3) All values of allowable soil pressure are for footing having a minimum width of 300 mm and a minimum depth of 300 mm into natural grade. Except as in Footnote (7) below, increase of 20% is allowed for each additional foot of width and/or depth to maximum value of three times the designated value. (4) May be increased in the amount of the designated value for each additional 300 mm of depth to a maximum of 15 times the designated value . Isolated poles for uses such as flagpoles or signs and poles used to support buildings which are not adversely affected by a 12-mm motion at ground surface due to short term lateral loads may be designed using lateral bearing values equal to two times the tabulated values. (5) Coefficient to be multiplied by the dead load . (6) Lateral sliding resistance value to be multiplied by the contact area. In no case shall the lateral sliding resistance exceed one half the dead load. (7) No increase for width is allowed.

pl

LOADS AND REACTIONS IN FOOTING

According the Cqde Section 5.15, the base area of footing and the number of piles may be determined from unfactored forces and moments transmitted by footing to soil or piles and permissible soil pressure or permissible pile capacity. Unfactored load (D L + LL) Effective soil pressure, qe

= -------'-----'-

Eq. 9-1

Unfactored load (DL + LL) . Number of pt1es = -------'-----'Load capacity per pile

Eq. 9-2

Area of footing

ag .

CHAPTER 9 • FOOTINGS Natural grade

. hs

'

Soil, Ys

"

.

where q, is the effective soil bearing capacity and is given as qe = qa- Yc he- Ys hs . :

Eq. 9-3

· where Yc is the unit weight of concrete (usually taken as 23.54 kN/m 3),h c is the . total depth of footing, Ys is the unit weight of soil above the footing, and h5 is .the height of soil above the footing.

CRITICAL SECTIONS IN FOOTINGS

The critical sections for moment, shear, and development reinforcement in footings supporting a rectangular or square columns or pedestals are measured at the face of the column or pedestal. For footings supporting a circular or regular polygon shaped columns orpedestal; the Code Section 5.15.3 permits to treat these sections as square members .with the same area. ·

Circle

Square with equal area as the circle

Regular polygon

Square with equal area as the polygon

CRITiCAL SECTIONS FOR MOMENT

Footings are similar to beams or slabs carrying the effective soil pressure as the load and the column as the support, hence it is subject to moments. · According to Section 5.15A.l, the external moment on any sectio~ for a footing may be determined by passing a :vertical plane to the footing, and computing the

264

REINFORCED CONCRETE DESIGN I

moment of the forces acting over the entire area on one side of that vertical plane. For isolated footings, the critical sections fot moment are located as follows: (a) At the .face of column, pedestal, or wall for footings supporting a

concrete column, pedestal, or walL

.. (b) Halfway betv.;reen middle and edge of wall, for footing 'supporting a masonry wall. ' ,

Middle pf wall

~t t/4

(c) flalfway· between face of column and edge of steel base plate, for footing supporting a column with steel base plate:

Steel base

a

CHAPTER 9 - FOOTINGS

DISTRIBUTION OF. FLEXURAL OR MAIN REINFORCEMENT '' Footings may be classified .as a one-waY, footing o:r: two 1vay footing . One-way footings are those, which are reinforced' in one ditection only, while two-way footings are reinforced in two directions. ·.

'

.

According to Section 5.15.4, in one-way foo.tings, and two-way square footings, reinforcement may be distributed uniformly across th~ entire width of footing.

One-way footing Two-way footing

In two-way rectangul~r footings, reinforcements may be distributed as follow;s! (a) Reinforcement in long directions may be distributed uniformly across .the entire width of footing. ' . · · (b) For .the reinforcement in the short directions, a portion of the total reinforcement may be distributed uniformly over a bandwidth (with center on c¢nterline of column). equal to the length of the short side of footing. The rest of the reinforcement may be distributed \lDifon!Uy outside the center b~ndwidthof footing. · The area of reinforcement in the center band is given by the formula

A 5 in center band width TotalA 5 inshortdirection where . long side of footing short side of footing

2

P+l

Eq. 9-4

266

REINFORCED CONCRETE DESIGN '

'

:

1:

;

: : :

•

: :

.\

: ;

I

.Outside center band

T

Center b'and, S

:

: :

T Vl

.Q) . "0

'iii

' t:

..

0

.s::;;

. Vl

:

J

Outside center band

Long side, L Figure 9.2: Reinforcement distribution for two-way r~angular footing

SHEAR IN FOOTINGS . The shear strength of slabs and footings in the vicinity of the columns, concentrated load, or reactions. is governed · by the more severe of two conditions, the .beam action or one-way shear and the two-way · or punching shear. In any of these two conditions, the Code requires that the maximum value of V, if stirrups are not used is ia V(/ where Vc. is the shear strength · l?rovided by concrete. 1. Beam action (one-way), where each critical' section . to be investigated extends in a plane across the entire width. For this case, the slab .or footing may be designed in accordance.to Section 5.11.1 through Section 5.11.5. According to this section, the shear strength provided by concrete Vcmay n~t exceed bw d.

t ..JF:

c j

L

Eq. 9-6

~ -··

CHAPTER 9 • FOOTINGS

With reference to the figure, V,; = q" x. shad~d area; where q, is t~1' factored soil pressure and is equal to P,;j A tooting· 2. Two-way action where each of the critical section to be investigated may ~e located so that its perimeter bois a mfnimum but need not approach dqserthan d/2 to: (a) edges or corners of columns, concentrated loads, or reaction areas, or

(b) changes' in slab thickness such as edges of capitals or drop panels ..

c

Qu

L

With referen~¢ to the figure,_bo = 4(c + d), V"

=

q" x shaded area.

For two-way action, V, is tile smaller value of Eq. 9 -7 & Eq. g,_ 9. ... ··. 2

I

)ff

Eq, 9 c 7

V . c= ( 1+- - - bod

'

·, · 13c

6

''

where long.side of column short side of column

Eq: 9-8

v'· = l3

·Eq. 9-9

13r = --=--,------'-. (71!' b A VJ c ""'

'

One"way shear will very often control the depths for rectangvlar footings, whereas twocway shear normally controls the-depth of square footings. · ·

REINFORCED CONCRETE DESIGN

268

MINIMUM DEPTH OF FOOTING According to Section 5.15.7, the depth of footing above bottom reinforcement may not be less ·than 150 rnrn for footings on soil, and 300 mm for footings on · piles.

CRITICAL SECTIONS FOR DEVELOPMENT Q.F R.EINFORCEME·NT IN FOOTINGS The developmeht of reinforcem€mt in footings is in accordance with Section 5.12. The critical sections for development of reinforcement may be assumed at the same locationas those of critical moment.

LOAD TRANSFER FROM COLUMNS TO FOOTINGS All forces acting at the base of a column must be transft!rred into the footing. Compressive forces may be transferred directly by bearing, while uplift or tensile forces must be transferred by developed reinforcing such as dowels and · mechanical connectors. At the base of the column, the permissible bearing strength of for either surfaces is 0(0.~S f, A1), where 0

=

0.70, but it may be.multiplied by ~A 2 / A1 :5:2 for

bearing in the footing (Section 5.10.15) where A1 is the column area and A2 is the area of the portion ofthe supporting footing tl;lat is geometrically similar and concentric with the columns. . :::. :;:::;< . . . .

. . .

::

.. . : '::;,:::::.:

CHAPTER 9 - FOOTINGS

.269

DOWELS If the computed bearing force.is higher than the allowable value, it is necessary to provide dowels to cauy the excess force . . Thiscanalso.b e done by extending . the column bars ihto the footing. If the computed bearing force is less than the allow~ble, theoretic<;~lly, no dowels are heeded but the code specifies a rrtinimum value. • ·· · · · · Fqr 'cast-in-place columns and pedestalS, the area of reinforcement across interface shall not be less than 0.005 times the gross area of the colunin or ped~stal, and at footings and 3p-mm longitudinal bars, in compression only, rnay be lap spliced with qowels to provide the required reinforcement. bowels may not be larger than 32 mrh bar and may extend into colu~n a distance not less than the development length of 36 mm bars or the sphce length of the dowel, whichever is greater, and into the footing a distance not less than the development leng.t h of the dowels (Sections 5.15.8.2.1 and 5.15.8.2.3).

I I I

11 . ' II II II II

..-----11I

e-:e---;•

Footing \Nith dowel

I I I I

:..._-----~ A

·g- 1! .- -

§'

I

A -p-

-e-.- 9

Colum'~ bars extending into footing

2

270

REINFORCED CONCRETE DESIGN

ILLUSTRATIVE PROBLEMS

PROBLEM 9.1

A ·square column footing is to support a 400-mm square tied column that . carries a dead load of 880 kN ahd a live load of 710 kN. the column is reinforced ,with 8-25 mm bars. · The base .of the footing is 1.50 m below the natural grade where the allowable soil pressure is 23~ kPa. The soil above ;j the footing has a weight of 15.6, kN/m3.: Assuming fy = 275 MPa, fc = 27.5 .._ -;_ :_~~· MPa, and unit weight of concrete as 23.50 kN/m3,design the footing. Use 25 l min main bars. .J SOLUTION Our firsrtask in the design of footing is' the determination of its depth. This requires several cycles of trial and error procedure because its value affects the .effective soil bearing capacity; There are several rules of thumb used by designers for making initial thickness estimates, such as 20% qf the footing.width plus 75 mm. However, with the aid of computer (available at GERTC), this will become easier.

lriitial estimate of footing depth: A ttg = L2 = (880 + 710)/235 _ L = 2.6m L = 2600mm Depth = 20% (2,600) + 75 = 595 mm say 600 mm ·Effective s'lil .bearing capacity: q, = q. - 'Y h =i35 .:: 23.5(0.6) - 15.6(1.5- 0.6) q. =:= 2o6.86 kPa

r.

Dimension ofthe footing: · Unfactored'Load A~ = .

qe

E

=880+710 206.86 Attg

= 7,.69 m 2 = L x _L

L ~ 2.77m say 2.8 m Footing dimension= 2.8 m x 2.8 m

p

y..,. = 15.6 KN/m 3 Yconc = 23,5 KN/m3

271

CHAPTER 9 • FOOTINGS

D'pth of Footing:

q, = .

Factore Load . Area of Footing

1.4(880). + 1.7(710) 2.8(2:8) = 311 .1 kPa q, = 0.3111 MPa =

E E O ·

g N

Based on wide-beam shear: V, ,;, q, A shaded

(0:3111)[2800(1200 -d)] .

=

v, '= 871.08(1200- d)N Vc ~ · t ..jf; bw ti =

t .J27.5 (2800) d .

Vc = 2447.2d N V, = Q! Vc 871.08(1200 - d) = 0.85(2447.2d) 1200 - d ;, 2.388d d=354.2mm Based on two~way or purtching shear: V, ;,. q, A shaded , . . = (0.3111)[(2800)2- (400 + d)2] = 0.3111(28002 -160000 - 800d- d2) V, = 0.3111(7,680,000- 800d .,.' d2)

2800

.bo = 4{400 + tf) , Vc =

f

.J27.5 [4{400 + d)]d

v, =·6. 99(400d + d2) ]V, = ~Vc] ·. 0.3111(7,6~0,000- 800d- dl) = 0.85[6.99(400d + dl)] 7,680,000- 800d- d2 = 7639d + 19d2 20dl + 8439d - 7,680,000 =0 2 -8439 ± ~(8439) ~ 4(20)(-7~,680,000) d= . _ __ ::...;__;_,_---..;._:,_.:..__ _ __:_. . 2(20)

. d = ·443.6 mm say 445 mm

m.m

272

REINFORCED CONCRETE DESIGN

Total-depth of footing= 445 + 1.5(25) + 75 Total depth= 557.5 mm < 600mm (OK) Required Steel Area: d =445:atm

M"

= (311.1)(1.2)(2.8){1 .2/2)

· = 627.18 KN-m M., = cp R" b d2 . . 1()6 = 0.9 R" (2800)(445) 2 , R"= 1.26 MPa . 627~18

X

Qu

f1 _.· 1 . . : 2R /y l 0.85 f = 0.85(27.5) . f1 _ _ 2(1.26) .· j . ' 275 l 1. 0.85(27.5) '

p=0:85j',

11 '

= 311.1 KPa

.j·

c

'

p= 0.00471

'

'

·1.4

Pmtn= -· -

·.

' P~r~in

u~

/y

1.4

= - .-

·,

275

l, ,

= 0.0050~11

P = o.oo5091 A,"= pbd , . = 0.005091(2800)(445) . A, = 6,343 mm2

Number of 25-mm bars: t (25)2 N = 6,343 N =12.9 say 1~ · Development Length: lilb =0.02 Ab fyj ldb = 0.02 x

t

.{f;

.

(25) 2 (275)/ .J47.5

=515 mm

·. or ldb = 0.06 db h = 0.06(25)(275) .,:, ~12.5 IIWl· '' .\ .. Furnished Ld =1200 - 75 = 1125 mm > 515 mm (OK) •

I

273

CHAPTER 9 • FOOTINGS

Vedfy if dowels or column bars extension are necessazy: · Actual bearing strength =P,. ;= 1.4(880) + 1.7(710)

· J?, = 2439 kN P-ermissible bearing stress: 2) $ 0.85.fr. A1 = 0.7{0.85){27.5)(400 ..

= 2,618,000 N

q, 0;85f, A1 = 2,618 kN But this may be multiplied by~A 2 I A1. :S 2 A1 = 0.4 x.0.4 =0.16 m2 A2 = 2.8 x 2.8 = 7,84 m2

~A2 I A 1 =7use1 . Permissible bearing stress = 2,618(2) =5,236 kN > 2439 kN (~o need) . Minimum area of dowel or extension bar required by the Code: Area = 0.005(400 x 400) • 800 mm2 · At least two column.bars (25-mm) must be extended into the footing. · .

.

'

Use 2.8 m x2.8 m footing with an effective depth to top bars of445mm (total depth = 560 m), with 13-25 min bars on.each side of tl;ze footing, and at least two column bars (25-mm as given) must be extended into the footing.

PROBLEM 9.2/

. _ _ ._ _-, A 600 mm >< 600 nun column caiTies a total live ioad of 1,200 kN and a total . .dead load of 1,500 kN. . The column is to be supported by a rectangular .) spread footing whose width is limited to 3 m (lnd whose bottom is 2 m below the ground surface. Allowable soil bearing capacity at the l:>ase of the: .:~' . footing is 230 kPa. l:}nit weight of soil above footing is 16 kN/m3 and unit :,; weight ofconcrete is 23.5 kN/m3• Assume f C:=18MPa and fy = 275 MPa. j

1

J

SOLUTION

Trial depth= 20%(3000) + 75 = 675 say 700 mm

Effective soil pressure qe .;,;qa- L,yh = 230- 16(1.3) - 23.5(0.7) qe =192.75kPa ,' , ~iZe of footing: Att = . Unfactored Load

qe

g

. .

•

1200 1500 + =14.01 m2 192.75 ' 3(L)'= 14.01 L = 4.67 m say 4.7 m

A

=

ftg

Depth qf foofing: · Factored Load q,=----Ajtg = 1:4(1500)+ 1.7(1200) 3(4.7)

=293.6kPa q, = 0.2936 MPa Based on wide beam shear: '

V, :i:: q, Ashaded '= 0.2936(3000)(2050 .:- d) N .v, .::= 880.8(2050 - d)

V,= fJfc .b;,d

4700 mm

~ --

CHA~A 9 • FOOTINGS

Vc =

215 . .

i J28 {3000)d

Vc = 2645.75d N V, = ~ Vc 880.8(2050 - d)= 0.85(2645.75d) 2050 - d 2.55d

=

d= .577min

Based on two-way shear: V,

= q, Ashadro

v,

= 0.2936[4700(3000) - (600 + d)2] = 0.2936(13,740,000 -1200d- d2]

Vc ;=

E

t J1': bo d .

E

8 M

bo := 4{600 +d) Vc =

t J28 (4{600 + d)]d

Vc = 7.05S(600d + di)

[V, = ~Vc] .

0.2936(i3,740,000- 1200d- d2] = 0.85[7.055(600d + d2)] 13,740,000 - 1200_d'- d 2 = 12255d + 20.4d2 ' . . 21.4d2 + 13,455d - 13,740,000 0 '

=

d= .

-13,455± ~(i3,455) 2 - 4(21.4)(-13,740,000) . . . 2(21.4) '

d=546~38mm

Used =577mm Total depth= 577 + 1.5(25) + 75 TotaFdepth =:: 689.5 .< 700 (OK) . .

'

'

'

Steel requirements Along long direction: · . M, = (293.6)(2.05)(3)(2.05/2) . M, = 1850.781 kN-m . M,=~R,,bd2

=

1850.781 X 106 0.90R,(3000)(577) 2 R, = 2.059 MPa .. . p=

·o.85f', .['" /y

..

t~

z'R, ]

0.85 f',

276

= 0:85(28)[1p

275

p

= 0.0078

1- 2(2.059) 0.85(28)

REINFORCED.CONCRETE DESIGN

l

1.4

'1.4

Pmin

= /y = 275

Pmin

=0.0051

= 0.75 Ph . . . . = 0.75·0.85(28)(0.85)(600) = 0.0378

Pmax

· Pmax

.·

275(600 + 275)

,

Use p = 0.0078 As"' pbd A5 = 0.0078(3000)(577) .ll (28)2 N = 13502 . 4 . .

=13502 mm2

N=2L9say22 Along short direction:· M,= 293.6(4.7)(1.2)(1.2/2) M,. = 993.54 kN-m

E ...;

N

M, =•R, bd2 993.54 X 106 = 0.90 ~~~ (4700)(577)2 R,. =0.7055 MPa . p

l

= 0:85 J', •[ 1 - r-l·-_-2...--R-.-.~-. . /y 0.85 f',

= •0,85(28.) [ 1 -

p . ... 275

.

1 _ 2(0. .7·0.S5) ]· . ' 0.85(28)

p =0.0026 < Pmin

Use p = Pnl1n =0.0051 .As= pbd= 0.0051(4700)(577 + 28) =14,502 rnrrt2 f (28)2 N = .14,502 .

·N

= 23.55 .say 24

Development length: LJ =ldb

=0.02 Abfy/ ..{f;

id =0.02 'x. f (25)2{275)/ .J27.5 .

or Ld == o,o6 db fv

= 515 mm •

=0.06(25)(275) =412.? mm

.

)

277

CHAPTER 9 • FOOTINGS

Minimum L.t furnished=:= 1200- 75 (no need to bend the bats)

= 1.1.25,mm >515 .~ (OK)

Bar distribution in short direction: f} = long side offooting . = 4.7 . shortsideoffooting 3 ~

=1.57

Along center band: · N center band N N center band

24

2 ~+1 ··

2 1.57+1

N center barid"" 18.7 say 19 bars . N outer band=:: (24 -19)/2 = 2.5 say B bars

3 mcenter band, 19 bars 4.7 in 25 bars

PROBLEM 9.3

A reinforced concrete square footing s11pports a 400 nuh x 400 mttl square J column carrying a total dead load of 700 kN and a total live load of 1100 kN. } The footing dimension is 3m x 3m and is supported by 9 piles spaced 1 m, ;r.J apart on a 3 x 3 formation. f, = 30 MPa, fy = 375 MPa. Design the footing. : Assume the piles are adequate to resist the loads. . · SOLunON

Factored load on each pile: P, = 1.4(700) + 1.7(1100) P,=2850kN 9Ru := P, = 2850 f{, = 316.67 kN

Effective depth of Footing

Based of Wide.:beam shear

- Vc =,

t ,fJ'; bw d

= t J30 (3000)d v, = 2738.6 d (N)

1

V,, =3R, :: 3(316,67)

v, ... 950kN

[Vu

1

=~ Vc] 950 X 1()3 = 0.85 X 2738.6 d d=408mm

1m Based on punching shear

3m

l ,fJ'; bod = t J30 [4(400 + d)]d

V, =

• V,= 7.303(400d + d2) V,

~

8R,.= 8(316.67)..

. v~ = ~3.3'6 kN

,'_:1

.-

- ~~ ·.....•..·.!: ··..

279

CHAPTER 9 · FOOTINGS

[VII= Vc] 2533.36 X 103 = 0.85(7.303) X (400 d + d2) d2 + 400d - 408,109 = 0 d=469.4 mm

Used= 470 m

Main bars: Mu = (3 R11 )(0.8) = (3 X 316.67)(0.8) M~~=760kN-m

[M11 =Rub d2 ] 760 X 106 = 0.90 Ru (3000)(470)2 R 11 = 1.274 MPa p= 0.85/'c [ 1 -

/y

=

p

1 _ 2Ru ] 0.85 f'c

0.85(30) [1- 1- 2(1.274) 375 0.85(30)

1.3 m

l

p = 0.0035 1 .4 = 0.0037 375 Use p = 0.0037 Pmin

=

A,= pbd = 0.0037(3000)(470)

= 5,217 mm2

Using 25 mm bars: 1- (25)2 N = 5217 N = 10.6 say 11 bars on both sides

Development length: Ld = ldb = 0.02 Ab jy/ .fj'; Ld = 0.02 x

f

(25)2(375)/

J30

=

672 mm

or Ld = 0.06 db jy = 0.06(25)(375) = 562.5 mm Ld furnished = 1,300 - 75 = 1,225 mm > 672 mm(OK)

PROBLEM9.4

Design the footing shown using the following data: Soil bearing capacity, qa = 180 kPa Steel strength, fy = 275 MPa Concrete strength, [c = 27.5 MPa Unit weight of soil above the footing= 15.2 kNfm3 Unit weight of concrete = 24 kN I m3 Deal load, PDL = 1,400 kN Live load, Pu = 1,850 kN Dead load moment, Mot = 450 kN-m Live load moment, MLL = 280 kN-m Column size = 600 mm x 600 mm Depth of footing = 1.8 m Use 28 mm diameter bars.

.j

1------- L

SOLUTION

Assume depth of footing = 750 mm Effective depth, d = 750- 75 -1.5(28) d=633mm Effective soil bearing capacity: q. = 180- 24(0.75) - 15.2(1.8 - 0.75) q. = 146.04 kPa .

281

CHAPTER 9- FOOTINGS

For combined axial load and bending: P Me q=-A±-I-

P 6M bd bd 2 p = 1,400 + 1,850 P= 3,250kN

qmax=----

•

M=450+280 M=730kN-m b=4.5m d=L

-146.04 =- 3,250 - 6(730) 4.5(L) 4.5L2 L2- 4.945L - 6.665 = 0 L = 6.04 m say 6.1 m

Verify if the stress at the other end is compression: qmin = _ 3,250 + _6__:.(7_3_:.0)-=4.5{6.1) 4.5(6.1) 2 qmin = -92.24 (compression, OK) Note: Should the stress at the other end is(+) tension, the value of L must be computed using the following procedure. (Since soil pressure cannot be in tension).

e p

e=M/P

lh(a)(q,)(b) = P 2P

a=-= qe b

L/2 = e + a/3 L = 2(e + aj3)

p

a/3 a

282

REINFORCED CONCRETE DESIGN

Design of Footing: · P, = 1.4(1400) + 1.7(1850) P, =5,105kN M, = 1.4(450) + 1.7(280) M, = 1,106 kN-m -

5,105

6(1,106)

qu-- (4.5}(6.1) _:!: 4.5(6.1) 2 •

q, max= -225.61 kPa (compression) q, min = -146.34 kPa (compression) Investigating the adequacy of assumed "d" on wide-beam shear:

d = 633 mm (assumed) 0.6 m

_}f_ = 79.27 ;3.983 6.1 y = 51.759

z = 146.34 + 51.759

t

z = 198.1 kPa

79.27 -----+1225.61

Vu = 225.61 + 198.1 (2.l17) 2 V, = 2018.2 kN

t Jl':bwd = t ./27.5 (4500)(633)

Vc=

=

2,489,610 N Vr = 2,489.61 kN ljl Vc = 0.85(2,489.61) ~ V, = 2116 kN > V,. (OK)

X

45

J.

283

CHAPTER 9 - FOOTINGS Note: This type of footing seldom fail by two-way or punching shear.

0.6m

Steel Requirements

2.75 m

Alopg long direction:

y_ =

79.27 3.35 6.1 y = 43.53

f

79.27

z = 43.53 + 146.34 z = 189.87 kPa

-~I = ¥2(2.75)(189.87)(4.5) 2X5 M11 = 3,636.18 kN-m

. M 11

[M11

+ 112(2.75)(225.61)(4.S)i (2.75)

= 4> R,. b d2] 3,636.18 X 106 = 0.90 R, (4500)(633)2 R,. = 2.241 MPa P = 0.85 f' c [ 1 -

/y

1_

= 0.85(27.5) [1-

275 p

2 Ru ] 0.85 f'c

1- 2(2.241) 0.85(27.5)

l

= 0.00858 Pmin

Pma x

= 1 .4 = 0.005091 275

= 0.75 Pb =

Pma x

Use p

0.75 0.85(27.5)(0.85)(600) 275(600 + 275)

= 0.0372

= 0.00858

As = pb10d = 0.00858(4500)(633) As = 24,440 mm2 f (28)2 N = 24,440 N = 39.7 say 40 bars

225.611

284

REINFORCED CONCRETE DESIGN

Along short direction: F, = 225.61 + 146.34 (6 .1)(1 .95 ) 2 F, = 2212.17 kN M, = F,(0.975) M, = 2156.9 kN-m

d=633+28 d=661 mm

[M, = +R,bd2] 2156.9 X 1()6 = 0.90 R,(6100)(661)2 R, = 0.899 MPa p = 0.85 f'c [ 1 -

/y

= 0.85(27.5) 275

1 _ 2 Ru 0.85 f'c

[1- 1-

l

2(0.899) 0.85 (27.5)

'.i

1.95 m

l

p =0.0033 Use p = Pmin = 0.005091

A.=' pbd = 0.005091(6100)(661)

As = 20,527 mm2

f

(28) 2 N = 20527

N =33.3 say 34 bars Distribution of bars: j} = 6.1/4.5 ~ =1.356 N center band 2 1.356+ 1 34 N = 28.9 say 29 bars Use 29 bars across center band width Use 3 bars acr.oss outer strip

285

CHAPTER 9 - FOOTINGS

Development length:

Ld = ldb = 0.02 Abfy/ .[1'; =

0.02 X

t (28)2(275)/ .J27.5

Ld= 646mm or Ld = 0.06 dbfy = 0.06(28)(275)

= 462 mrn

Min Ld furnished = 1950 - 75 Min Ld furnished = 1,875 mm > 646 mm (OK)

. r

6.1 m with 35 bars, 29 across center band and 3 across each outer bMd

---1 1

PROBLEM 9.5

Design a rectangular column footing to carry the following column loads: PoL= 800 kN MoL = 160 kN-m PLL = 670 kN MLL = 170 kN-m The column is 500 mm x 500 mm and is reinforced with 8-25 mm bars. The base of footing is 1.6 m below the natural grade and the effective soil bearing capacity may be conservatively taken as 190 kPa. Design the footingsuch that the soil pressure at the base is uniform.. Take L = 1.4B and use fc = 27.6 • ·MPa andfy = 414 MPa. Use 20 mm main bars. SOLUTION

For the soil pressure to be uniform, the centroid of footing must coincide with the resultant column load, which is at a distance of "e" from the column center. M . . Eccentricity, e = p

e = 160+ 170 = 0.224 m 800+670 e=224mm L = 3.3 m e = 224 mm 1 I

1.65 m

287

CHAPTER 9 · FOOTINGS

Since the soil pressure is uniform, then; Area of footing

PoL+ PLL = -'-='---"-'-'--

Area = 800 + 670 190 Area= 7.74 m2 = L x B (1.4B) X B = 7.74 B = 2.35 m say 2.4 m L(2.4) = 7.74 L = 3.225 m say 3.3 m P, = 1.4(800) + 1.7(670) P, = 2,259kN p

2,259

q, = L;'B = 3.3(2.4), q, = 285.23 kPa Effective depth of footing: Based on wide-beam shear:

v, = q,

X

A shaded

= 285.23(2.4)(1.624- d) V, = 684.552(1.624 - d) (kN)

V,

=

t .jl'; bwd

=

t

L = 3.3 m

r

1.624- d

E

-./27.6 (2400)(dx1000)

= 2,101,428 d (N) V, = 2,101.43 d (kN) V,=
X

2,101.43 d

Qu =

285.23

288

REINFORCED CONCRETE DESIGN

Check for adequacy of "d" in punching shear: bo = 4(c + d) bo = 3800

t =t

V, =

= 4(500 + 450)

JF;bod

.J27.6 (3,800)(450) V, = 2,994,535 N = 2,994.5 kN

41 v, = 0.85(2,994.5) ell V, = 2,545 kN

Vu

= qu (Attg- Apunch) Apunch = (0.5 + 0.45)2 = 0.9025 m 2

= 285.23(2.4 X 3.3- 0.9025) Vu = 2,002 kN < ell V, (OK) Vu

Design of reinforcement L = 3.3 m

.,.E

...,; II

..0

Bars alon& the len!¢t:

Mu = qu b Lt2/2 Mu = 285.23(2.4)(1.624)2/2 Mu = 902.7 kN-m [Mu

=4»R,btf2] 902.7 X 1()6 ~ 0.90Ru{2400)(450)2 R,=2.06MPa

289

CHAPTER 9 - FOOTINGS

_ 0.85 f'c [ 1- 1 ---~2 Ru ] p!y 0.85 f'c = 0.85(27.6) [1414

1- 2(2.06) 0.85(27.6)

l

p = 0.00522

Pmin = 1.4/fy Pmin =1.4/414 = 0.00338 Pmax

= 0.75 Pb

= 0.75 0.85(27.6)(0.85)(600) 414(600 + 414) Pmax = 0.0214 Use p = 0.00522 As = pbd = 0.00522(2400)(450) As= 5638mm2

f (20)2 N = 5638 N = 17.9 say 18 bars to be distributed across the 2.4-m side Bars along the width: d=450+db d=470mm M, = q, XL X L22/2 = 285.23(3.3)(0.95)2/2 M, = 424.74 kN-m

[M,

=$R, b d2] where b = 3300 mm 424.74 X 102 = 0.90 R, (3300)(470) 2 R, = 0.647 MPa p= 0.85J'c [ 1 -

!y

.

1 _ _2_R~l 0.85f c

= 0.85(27.6) [1- 1

414 p

= 0.00158

Use p

= Pmin

= 0.00338

2 (0.647) 0.85 (27.6)

l

290

REINFORCED CONCRETE DESIGN

A, = pbd = 0.00338(3300)(470) As = 5,242 mm2 f (20)2 N = 5,242 N= 16.6870 N center band 2 --Ntotal P+ 1 p = 3·3 = 1.375 2.4

N center band 2 16.687 1.375 + 1 N center band= 14.05 say 15 bars N outer bands = 2 bars Development length: Ld = ldb = 0.02 Abfy I..[!'; = 0.02 X

t

(20)2 (414)/.J27.6

k=495mm or Ld = 0.06 dbfy = 0.06(20)(414) = 497 mm Minimum Ld furnished = 950 - 75 = 875 mm > 497 mm (OK)

500 mm x 500 mm

Total depth

= 560mm

CHAPTER 9 - FOOTINGS

PROBLEM 9.6 (CE MAY 1998)

For the wall footing shown in the Figure: fc = 28 MPa fv = 280 MPa

unit weight of cone. = 24 kN/m unit weight of soil = 16 kN/m 3

3

tI

Po= 200 kN/m} . = 180 kN/m serv1ce

pL

Ho HL

loads

= 60 kN/m} = 30 kN/m service loads

E 0

~

.....

Determine the effective soil pressure, in KiloPascals, if the allowable soil pressure is 200 KiloPascals (effective soil pressure is the remaining soil pressure available to support the wall loads after the effects of the soil and concrete weights are deducted) · b) Determine the minimum width of the wall footing, in meters rounded upwards to the nearest 0.10 meter, such that the effective soil pressure is not exceeded. c) Using the dimension obtained in (b), and considering a one-meter strip, determine the ultimate shear due to factored loads, in KiloNewtons, acting on the critical section for one-way or beam shear. d) Using 25 nun diameter bars, what is its required spacing. e) Using 10 nun shrinkage and temperature bars with Jy = 275 MPa, determine the required spacing. a)

SOLUTION

Part a: Effective soil pressure, q.:

q, = q.- L.yh = q.- Yconc hconc- Ysoil hsoil

= 200- 24(0.46} - 16(1.2- 0.46)

q, = 177.12 kPa

292

REINFORCED CONCRETE DESIGN

Part b: Considering 1 m strip:

I Po =200 kN/m

't Pl = 180 kN/m

E E

~

·a The maximum soil pressure is given by the equation: P 6M qmax = - + . S q, · A bd 2

P = 200 + 180 = 380 kN (unfactored load) A= B(1) (considering 1m width of footing only) M = (60 + 30)(1.04) M = 93.6 kN-m (moment at column base) b = 1m (width along the axis of bending) d = B (width transverse to the axis of bending) then; - 380 6(93.6) B(1) + . 1(8)2

qmax-

where qmax =177.12 177.1282 - 380B- 561.6 = 0 B = 3.15 say 3.20 m

293

CHAPTER 9 - FOOTINGS

Part c: 1.45m

Critical Section for beam shear

Qumax

Qu min

= 265.39

= 100.86

2.14m .

.

); (

1.06m

:I

3.20m

The ultimate soil pressure qu is given by: (considering 1m strip)

Pu

6Mu

q" = 1\ ± 1(B) 2 P" = 1.4Pv +-1.7PL P,. = 1.4(200) + 1.7(180) = 586 kN A= 1(3.2) = 3.2 m2 M" = Hu(1.04) Mu = [1.4(60) + 1.7(30)] (1.04) Mu = 140.4 kN-m then; 586

6(140.4)

qu = 3.2 ± 1(3.2) 2 using(+) using(-)

qumax qumin

= 265.39 kPa = 100.86 kPa

From the stress diagram shown above: q, = 100.86 + y Solving for y from similar triangles: J_ = 164.53 2.14 3.2

294

REINFORCED COI';-ICRETE DESIGN

y = 110.03 kPa qc = 100.86 + 110.03 = 210.89 kPa 1.06 m

The ultimate shear Vu acting on the critical section is the volume of the diagram shown to the right

v,. = [1/2(210.89 + 265.39)(1.06)1(1) V. =252kN Verifying the adequacy of" d" against wide-beam shear:

t ..Jl':

Vc = bw d bw = 1000 mm; d = 390 mm Vc =

t J28 (1000)(390)

Vc = 343,948 N ~ Vc

i

= 343.948 kN

j

l

= 0.85(343.948) = 292 kN > Vu (OK)

·.11

'~ l

i

Part d: Steel Requirements

..J

:l

I i

·~

I

'I

.,' '

265.39

_}/_ = 164.53

1.75 m

1.75 3.20 y = 89.977 kPa q~ =

Mu Mu

1.45 m 3.20 m

100.86 + 89.977 =190.837 kPa (1.45) + 1/2(1.45)(265.39)

= 1/2(1.45)(190.837) X = 252.87 kN-m

t

X

i (1.45)

aps

CHAPTER 9 - FOOTINGS

[Mu

' ..

=+R,; li tPJ

, ,

·252.87 X 106 = 0.90 Ru (1000){390)2 Ru = 1.847 MPa

• .. , ..

l~

= 0.85f'c [ 1.· _

/y

·p

. .· ·

2R"] · 0.85 f'c ,

'= 0.85(28) [1- 1- 2 (1.847)

280

0.85 (28)

p = 0.00687 . Pmin Pmax

J

-

=1.4/280 =(J.005 = 0.75 Pb

=0.75 0.85(28)(0.85)(600) Pmax

·

.

280{600 :t.280)

= 0.036 . 9 ,

Use p = 0.00687 . As= pbd = 0.00687(1000)(390). A,=2679mm2 f (25)2 N = 2679;

. ' 1000 Spacmg = - . 5.458

spacmg . = 3200-75(2) 19.619 Spacing= 155 mm

= 5.458

. . = 18·.3. mm say 180. mm o.c.

Parte: _ Shrinkage and temperature bars: .. A$, = 0.002 b h . = 0.002(3200)(460) Ast = 2,944 mm2 f (16)2 N = 3,944 N= 19.616

N

,.

I .~

296

REINFORCED CONCRETE DESIGN

COMBINED FOOTINGS . Combined footings support more than one column. One situation where these footings may be used is when the columns are so close together so that isolated or individual footing would run into each other. Another situation is when the column is very near the property line, such that an isolated footing would extend across the line. A trapezoidal ·footing or strap (T) footings may also be used 'the two adjacent column are very near the property line. , In. any of these shapes, it is very ip1portant to let the centroid bf the footing coincide with the centroid of the combined column loads. In this manner, the oearing . pressure underneath the footing would be unif~rm a~d it prevents uneven settlement. '"' - ··

Interior columns with equal loads

1~'lr[!l ,

Rectangular corl')bined footing

q

Interior & exterior columns with Load 2 > Load 1

Property line

Rectangular (free to extencj beyond column 2)

Property line ..

.,

\

Exterior columns with Load 2 > Load 1

I

Trapezoidal combined footing

Figure 9.3: Combined footings

CHAPTER 9 - FOOTINGS •

. •·.

. .

.

.

.

I

'

·STRAP OR CANTILEVER FOOTING When space is restricted for -a single columrt footing, the soil pressure under tl;e footing c~n be made uniform by co"mbining it with the adjacent colUilU'l or columns using a rectangular of trapezoidal shape. As the distance between -such columns increases, the cost of such shapes· rises rapidly: - For column spacing inore than 4.5 m, strap footing may be more econoll)ical. It consists of• a separate footing under each colun,m connected by a }Jearn or strap to distribute the column loads.

a

The footings are sized to produce the same constant pressui~ under ~ts base: This is attained wh,li!n the centroid of their areas coincide with the resultant of the column loaqs.

( .Pl ~ S'tr'?!

t, +., J r_-

[

.

i1r:,., n /?\

PLAN

ELEVATION

298

REINFORCED CONCRETE DESIGN

Usually, the strap is raised above the bottom of the footing so ,as not to bear on · the· soil. The strap should be designe.d as a rectangular beam spanning between the columns. The loads on it inc_lude its own weight (when it does not rest on soil), the1upward pressure from the footings, and the colun1n loads. The width strap is usually Selected equalto that of the largest ·c9lumn plus 100 mm to 200mm so thatcolumn forms can be supported on top of the strap. Its depth is determined by the maximufl' bending moment.

of

The main reinforcement in the s.trap is· placed near the tOJ? and stirrups are normally needed near, tfie columns. Longitu?inal placement .s.teeUs also set r'i.ear the bottom, plus reinforcement to guard against Settlement stresses. The footing under the exterior column may be designed as a wall footing, The interior footing should be designed as a single-column footing; however its Gt"itical section for punching shear should be computed on a section parallelto the strap at a diSt~r'i.ce d/2 from its face.

..

••

CHAPTER 9 - FOOTINGS

·ItLUSTR.t\TIVE PROBLEMS

PROBLEM 9.7 .

Design the combined footing· to support the two columns shown. The base ·· oHootingis 2 m below the ground surf~ce. Use the following qata:· Yconc = 23.5 kNjm3, Yson ~ 17.2 'kN/m3, jy = 345 MPa, /c = 21.5 MP~. Use 25 nun . diameter main bars. Allowable soil bearing pressure, q. = 290 kPa · · Column2: PDL = 1,120 kN Ptt = 1,430 kN

Column 1: PoL =.650kN PLt=940kN

20()

mm

SOLUTION

Solving for L:

p

'

I

J:

- I· ·o


·! ·. pl ,

g:~ l I I(

X1

.I I v

f .I

300

REINFORCED CONCRETE DESIGN.

PI= 650+ 940

p, = 1,590 kN' x, =;' 0.2 in p2 = 1,120 + 1,430 Pz = 2,550 kN Xz = 0.2 + 4 = 4.2 nt P = P, + Pz = 4,140 kN-

X

__lP.

=?

V~rigtt6n 11' lt'\11) ~,

g · •

[PXg= P, x, + Pz xz] 4,140 Xg = 1,590(0.2) + 2,550(4.2) Xg = 2.664 m = L/2 L = 5.33m '!Note: Due to complexi,ty of the calculation, the value of d for combined footing is usually assumed and checked later. Usually two or more trials are made before getting its most reasonable. The student may find this procedure · too tedious and tiresome, but one should think that iffooting fails, the wholebuilding fails,. so this effort is worth it.

Tryd = 680 mm (the author got this value after several trials) Total depth offooting = d + 0.5 x bar diam. +cone. cover Total depth of footing, h, = 680 + 0.5(25)+ 75 Total depth of footing, he= .= 767Ssay 768 mm

•

fleightof soil above footing= 2- 0.768 = 1.232 m

qc = q;,- Yc he c Ys-hs q. = 290 - 23.5(0.768) - 17.2(1.232) . q. = 250:8 kPa Area

offootin~ = !_ qe

. = --,------'4,140 A rea o f' f.ooting . . 250.8

= 16.51 m 2

Area offooting := 5.33 ~ B = 16.51 B .~3.lm

P,,, =1A(650) + 1.7(940) · P;11 = 2,508 kN . ' Pu2= 1.4(1,120) + 1.7(1,430) · Puz = 3,999 kN

P" = P111 + p,;2 Pu = 2,508 + 3,999 = 6,507kN

_c_H_A_PT_E_R_9_-..,F_o_o_TI_N_G_s_ __..._ _ _ _ _ _ _ _ _....;..._ __;._;...._...,;._.. · ' ';', ' ,

.

6,507 ·q,.= _p_u_ .= ~--

. · Area

3.1(5.33)

q,. = 393.815 .kPa . _ Check "d'' for two-way or punching shear:

Column 1: b.= 0.74(2) + 1.08 = 2.56 m b.=2,560mm

V,. = Put - q,. X Ashad'ed ';" 2,508.,. 393.815(0.74 X 1.08) j .

J

V,. =2193.26kN

' 1

v'

=

r -"fY"U--

3

rii'J'· b d "1/J c 0 .

t

./27.5 (2,560)(68q)

= .1.

, s·~

V, = 3,042,944 N

rv -·

.

= 0.85(3,042,944) = 2,586,502 N ~ v; =2,586.5 kN > V,. (OK)

~ V,

Column2: · bo = 1.18(4) = 4.72 m b. =4,720 trim.

P-el-.

302

REINFORCED CONCRETE DES.IGN

V, =· P,2- q,

X

Ashaded

= 3,999 _; 393.815(1.18)2

V, ; 3450.65 kN

·v=

1. ·· ~f . I ·· b .a· 3 vJ. c o

I

t

=

.J27.5 (4,720)(680)

V c = 5,610,428 N ·.··

$Vc= 0.85($,610,428) $Vc = 4,768,864 N = 4,769 kN > V, (OK)

. Check "d" for

one~wayor · wide

beam shear:

V,, = q,(0.4 + 0.68)(3.1)- P,1 = 393.815(1.08)(3.1}- 2,508

v,l

=-1189.5 kN

·

·

q,G

Vu2 = P,20.5 + 0.68)(3.1) . = 3,999 S?8~ 5(2.06)(3.1 ) / V,2 = 1484.1 kN · /

·

v,3 = -q,(0.88 '- o.68) V!'3 = -(393.815)(0.2) =~78.76 Max V,

= 1484.·1 kN

Vc= =

t

.'.=:

Jf;bwd

t .J27.5(3100)(680)

. Vc = l,842,408N = 1,842.4kN

$ Vc =0.85(1,842.4) $ Vc = 1,566 kN > v,·(OK) Design of main bars along length: WJ = 2,508/0.4 W1 = 6,270 kNjm = 3,999/~.5 . w2 :;:_7,998 kN/m

lV2

.

w, =393.815(3.1) w, = 1220.83 kNjm

CHAPTER.9- FOOTINGS

E

From the. shear and moment diagram shown: X.

3.55

2019.668 + 2314.2785 2019.668 x:o:1.654m

,

304

REINFORCED CONCRETE DESIGN

M = Area of shear diagram M1 = 1/2(0.4)\--2019.668) . M1 = .-403.93 kN-m

-M2 = 1ff(0.4 + 1.654)(-2,019.668) / M 2 = -2074.2 kN-m

M3 = -2074.2 + 1h(3.55 - ~(2314.2785) M3 = 119.74 kN-m .

M. =1220,83(0.88)(0.88/2) M. = 472.7 kN-m

,,._.·•

131 =0.85

.··.:

··::';

- 0.85 !', 131 600 Pb- fy(600+ /y) .

-'l '·

,; 0.85(27.5)(0.85)(600) Pb · , 345(600 + 3~5)

= 0.03657

Pm•x = 0.75 Pb Pmax

=0.0274

Pmin =.1.4/345

=0.00406

b =:= 3.1 m = 3,100 mm . d=680mm Abar = 'i (25) 2 = 491 rhJn2 r>-

.

::;:,·,·

·;~

...,

...

-~

>:

~- ~"'~'\~ .

Moment,Mu. M ·

;,·· . · · "·,}~~t

...

'. !, ',. -2074.2 .

-403.93

~o1

,.,

•

119.74

472.7

0.31310

·z60779

0.09281I

-0.36641

0.85/'c 2Rup=. - [ 1-) 1 /y 0.85f'c

0.00091

· . o.~

0.00027

0.00107

Usep

0.00406 ·' 8,558 17.4 18 Top _

000406 '

0.00406

Ru= - " .. 2

+6d

J

As=pbd Number Of bars, N . UseN= Location .

.

=As/A~ -

!

0.00483 10,187 20)' 21 Top

I) 8,558 17.4 ' 18 Bottom

8~558

17.4 18 . Bottom

' >

':-,·'

301

CHAPTER 9 - FOOTINGS

Design of main bars along width

E

.....

,...;

Note: The Code did not specify the width to be considered in the design of transverse bars. It is usually assumed equal to column width plus 0.75 d.

Column 1: b =400 + 0.75(680) b;.,910nun d = 680 - 25 = 655 (tt;ansverse bars on top of longitudinal) Mut =393.815(0.91)(1.352/2) Mut = 326.57 kN-m Column2: b = 500 + 0.75(680) b=1010ni lvfu2 = 393.815(1;01)(1.32/2) Mu2 =336.1 kN-m

0~929

0.862

0.00275

0.00255

REINFORCED CONCRETE DESIGN

306 Development length: Ld = l~b ~ 0.02Ab.fv /..{f;

= o.oz .x 491 (345)/ .J27.5 Ld=646mm ·or Ld =0.06 db.fv =0,06(25)(345)

=518 mm

Minimum Ld furnished = 1800 - 75 . Minimum Ld furirished = 1725 mm > 646 mm (OK) Shrinkage and temperature bars: Using 16 mm bars withf:v = 275 MPa For b = 1000 mm: Ast = 0.002bh = 0.002(1000)(793) ' Ast = 1586 mm2

f

(16)2 N =1,586 N= 7.888 1000 . Spacmg = - 7.888

=127 say 125 mm p.c.

75mm

~~~~~~~~~~.:r~ 910 mm

1.

~...-_~J

75 mm

307

CHAPTER 9 - FOOTINGS

PROBLEM 9.8

Design the combined footing to support the two columns shown.· The base of footing is 2.2 m below the ground surface. Use the following data: icon~' • 23.5 kN/m3, Ysoil = 17.6 kN/m3, JY '"\275 MPa, fc = 27.5 MPa; Use 25 m.m diameter main bars. Allowable soil bearing pressure, qa = 245 kPa. Use 28- · mm diameter main bars. Column 1: Column2: PoL= 550 kN PoL= 945 kN PL~~ S60kN PLL = 1,175 kN,

Length, L

SOLUTION

Pt =550+ 860 Pt =1,410 kN Xt = l.m·,

>«;

p2 .= 945 + 1,175 P2= 2,120 kN x2=4m I(

P= Pt + P2. P =3,530 kN P Xc = Pt Xt + P2 X2 3,530 Xc 1,410(1) +2,120(4) Xc 2.802 m =L/2 L = 5.?04 m say 5.61 m

=

=

= L/2

30~t

REINFORCED .CONCRETE DESIGN

Try d = 540 mm (the author goUhis value after several trials) Total depth of footing= d + 0.5 x bar diam +cone. cover Total depth of footing, he= 540 + 0.5(28) + 75 Total depth of footing, he = 629 say 630 m.Q.l Height of soil above footing :: 2.2 "" 0.6~ = 1.57 m q, = qa - Ychc - Ys hs . q, = 245- 23.5(0.63)- 17.6(1.57) q, = 202.56 kPa ' .

p

A rea: o ff. ooting = -

·

~

qe

3,530 202.56

= -. - .

Area of footing= 17.43 m2· At:ea offooting = 5.61 _x B 17.44

=

B = 3.11 m P,1 P,1

= 1.4(550) + 1.7(860) = 2,232 kN

P;,2 = 1.4(945)+ 1.7(1,175) P,2 = 3,320.5 kN P,

= P,1 + P,2

= 2,232 + 3,320.5 P, = 5,552.5 kN Pu q, = Area 5,552.5 3.11(5.61) q, = 318.25 kPa

Check" d" fbr two-way or punching shear: Convert the circular column tb square of~qual area; (Code Section 5.15.3) Asquare

=: Acircle

a2 = f (480)2 a=425mm . \!

•

CHAPTER 9 • FOOTINGS

r E

For column ~: VII =·P,;t '- q,. X Ashaded = 2,232- 318.25(0.99 v,~ 1,920.1 kN

=

V,=;=

X

0.99)

t ..[1'; bod

t

= .J27.5 (990 X 4)(540) = 3,737,955 N V, = 3,738 ,kN

v, =0.85(3,738) .~ v, = 3,177.3 kN > VII (OK) ~

For column 2: V, = Pu2 - q11 X Ashaded = 3,320.5- 318.25(0.965 VII =3,024 kN . . V, =

t .J27.5 (965

X

X

0.965)

4)(540)

= 3,643,562 N Vc= 3,644kN ·~ V<

== 0.85(3,644)

~ V,

= 3097.4 kN > 3,024 kN (OK)'

310

~EINFORCED CONCRETE DESIGN

Check "d" for

one~way

shear:

Solving for the Vu: At section a: VII= 318.25(0.235)(3.11)

= 232.6 kN

At section b: V,

= 318.25(1.765)(3.11)- 2,232 = -485.1 kN

At section c: V, =3,320.5- 318.25(2.3645)(3.11) = 982.2 kN At section d: V,

= -318.25(0.8575)(3.11) = ~848.7 kN

= 982.2 kN Vc:= f.[l';bwd

UseV,

where,b;,, = 3.11 m == 3110 mm

t

Vr = )27.5(3110)(540) V, = 1,467,808 N = 1,468 kN $ v, = 0.85(1,4.68) $ V, = 1247.8 kN > V,, (OK)

. .~~ •.

JU

CHAPTER 9 • FOOTINGS

Moment along long direction: X

.b

I E

.... ....

450

425

,....;

L~-----+-'-~ :

1m

~

-w<~~-- 3m -----M--1.61 m 5.61 m Pu1 •

2,232 kN

............ ......' ..

::::::::::

1

, .., , '

I

'

1

:~

. :~

~

3,320.5 kN

c :. :... :. .: .. ' : .' .: :. :. :... ... .. . . :.. ::: : .: . . :::. ::. : ...

i qu = 318.25 kPa

I

I

Pu1 •

I

•• \

I

~_./\l

,, . .. ..

j// ~

\ · ~ \ -~ ,' '.' / Moment diagram \. / •

~i ~ i '. \ \ .-

..

. · .,," _,,' ~-~ ··_· ,....,___,

•

At section a: , M, • 318.25(3.11)(0.7752/2) .. 297.24 kN-m At section b: M, • 318.25(3.11)(1.2252/2)- 2,232(0.45/2) • 240.4 kN-m

Shear diagram

•

REINFORCED CONCRETE DESIGN

At section c: Solve for x (point of zero shear) . Vr = 318.25(3.11) X- 2,232 = 0 x=2.255m , Mu = 318.25{3.11)(2.2552/2)- 2,232(2.255- 0.775- 0.45/2) M, =-284.7kN At section d: M, = 318.25(3.11)(1.82252/2)- 3,320.5(0.425/2) = 938.1 kN-m At section e: M, = 318.25(~.11)(1.39752 /2) ~1

= 966.5 kN-m

= 0.85 - _0._85~/-=''..:....~,:_16_00_ Pb/y(600+ /y) = . 0.85(27.5)(0.85)(600)

Pb

= 0.0495

275(600 + 275)

Pmax Pmln

=0.75 Pb = 0.0371 =1.4/275 = 0.0051

b•3110mm d=540mm · As~~"" t (28) 2 - 616 mm2

a

b

c

d

e

Moment,M,

297.24

240.4

284.7

938.1

966.5

_ Mu R , - -,-

0.3642

0.2945

0.3488

1.1494

0.3642

_ OR.Sf', p - - [ 1-} 1 -2R, --

0.0013

0.0011

0.0013

0.0043

0.0013

Usep As= pbd Number of bars, N =A,f Ab UseN= Location

0.0051 8564.9 13.9 .

0.0051 8564.9 13.9

0.0051

0.0051 8564.9 13.9

0.0051 8564.9 13.9

Section~

41bd 2

!y

0.85f',

l

8564.~

13.9

14

14

14

14

14

Bottom

Bottom

Top

Bottom

Bottom

313

CHAPTER 9 • FOOT.INGS

Moment along short direction:

Column 1: bl = 450 + 0.75(540) b1 =855mm M, = 318.25(0.855)(1.332/2) M, = 240.66 kN-m Column2: b2 = 425 + 0.75(540) b2 =830mm M, =: 318.25(0.83)(1.34252/2) M, = 238.04 kN"m

' dl = d2 = 540 - 28 d1 = d2 = 512 mm (transverse bars above longitudinal) Section

~

Moment, M, (kN-m) b_(mm)

R,= Mu ~bd 2

i

0.85f'c p= - [ 1- 1 -2Ru - -]

fy

0.85 f'c

Usep As= pbd Number of bars, N =As/ Ab UseN= Location

Column 1

Column2

240.66 855

238.04 830

1.19

1.216

0.00446

0.00454

0.0051 2,233 3.6

0.0051 2,167 3.5

4

4

Bottom

Bottom

314

REINFORCED CONCRETE DESIGN

Shrinkage and temperature bars: Using 16 mm bars withfy = 275 MPa For b = 1000 mm: Ast = 0.002bh = 0.002(1000)(657) Ast = 1,314 mm2

f

(16)2 N

= 1,314

N = 6.535 1000 . Spacmg= - 6.535 Spacing = 153 say 150 mm o.c.

Development length: Ld = ldb = 0.02 Abfy I

ffc

Ld = 0.02 x 616 (275)/.J27.5 = 646 mm or Ld = 0.06 dbjy = 0.06(28)(275) = 462 mm

Minimum Ld funtished = 1,330 + 450 - 75 Minimum La furnished= 1,705 mm (OK)

CHAPTER 9 • FOOTINGS

PROBLEM 9.9

Given the following column properties and loads: Column 1 300 mrn x 300 mrn 4 - 25 mrn bars DL=425kN LL = 340 kN ' :!!~ • -----

~"

Column 2 400 mrn x 400 mrn 6 - 25 mrn bars DL =535 kN LL =490kN 4.5m ----~..~

Cd~~l

Design a suitable trapezoidal-shaped footing. Use fc = 21 MPa, fy = 414 MPa, and assume q. = 160 kPa. Use 20 mrn main bars and 16 mrn temperature bars withfy = 275 MPa. SOLUTION

Solving fo~ the location of the resultant force on footing: Pt = 425 + 340 Pt = 765kN Xt = 0.3/2 xt=0.15m p2 = 535 + 490 P2 = 1,025 kN X2 = 4.5- 0.4/2 x2=4.3m

P= Pt + P2 P= 1,790kN p XG = Pt Xt + p2 X2

1,790 XG = 765(0.15) + 1,025(4.3) XG= 2.526m

316

REINFORCED CONCRETE DESIGN

Solving for dimensions a and b: p 1,790 Ang=- = - qe 160 Ang = 11.1875 m2 ~-----

L

= 4.5 m -------+~

A

b

A1 = V2(a)(4.5) =2.25 a A2 =1/2(b)(4.5) = 2.25 b A =A1 +A2 11.1875 =2.25a + 2.25b

a • 4.972- b

~

Eq. (1)

A Xc • A1(1.5) + A2(3) 11.1875(2.526) = 2.25a(1.5) + 2.25b(3)

a + 2b =8.373

~

Eq. (2)

Substitute "a" in Eq. (1) to Eq. (2): 4.972- b + 2b = 8.373 b =3.401 m a= 4.972-3.401 =1.57 m Use a "" 1.57 m and b =3.41 m Actu aifootingarea= 1.57 + 3.41 (4.5) 2 Actual footing area:= 11.205 > 11.1875 (OK)

317

CHAPTER 9 - FOOTINGS P111

= 1.4(425) + 1.7(340)

P111

= 1,173 kN

= 1.4(535) + 1.7(490) P112 =:. 1,582 kN

pl/2

P" =Put+ Pu2 P, = 2,755kN Pu

2,755 11.205

q~~=--=--

Aactual

q, = 245.87 kPa

I

j

.

I

d

I

I

~j

I

.

j I

200 Wt

=

q,. X a

=245.87(1.57)

Wt

·w2

w2

= 386.02 kN/m

=qu x b = 245.87(3.41) = 838.42 kN/m

311

REINFORCED CONCRETE DESIGN 1173 kN

1582 kN

838.42

l •

838.42- 386.02 4.5 y •100.533x X

W•

386.02 + 100.533 X

Width of footing at any value of x: 4.Sm .

b •1.57 + 0.4089x

Shear at any point: V • 386.02 x + Vz(x)(100.533x) -1173 V • 50.21 x2 + 386.02 x -1,173

~

Eq. (1)

Moment at any polr\t: M • 386.02(-t'/2) + Vz(x)(100.533x)(x/3)- 1173(x- 0.15) M •193.01 xl + 16.76 xs -1173x + 175.95 ~ Eq. (2)

Ataume d • 620 mm: Wide beam •hear at column 1: x• 0.3 +d x•0.92m Vu • 50.27 (0.92)2 + 386.02 (0.92} - 1,173 Vu • -775.3 kN b •1.57 + 0.4089(0.92) b•1.946m

CHAPTER 9 • FOOTINGS

v, = t ffi (1,946)(620) V, = 921,495 N = 921.495 kN
v, = 783 kN > VII (OK)

Wide beam shear at column 2; x = 4.5 - 0.4 - d = 3.48 m VII= 50.27(3.48) 2 + 386.02(3.48) -1,173 VII= 779.14 kN b = 1.57 + 0.4089(3.48) b = 2.993 m

v, = t ffi (2,993)(620) V, = 1,417,284 N = 1,417.28 kN
v, =1,204.7 kN > VII (OK)

Punching shear at column 1; V., = P11t - q11 x Area = 1,173- 245.87[(0.3 + 0.62/2)(0.3 + 0.62)] VII = 1,035.02 kN b0 = 2(300 + 620 /2) + (300 + 620) bo= 2,140mm

v,"'

t ffi (2,140)(620) = 2,026,720

V, = 2,026.72 kN v, =1,723 kN > VII (OK)


Punching shear at column 2; V11 =P112 - q11 x Area .. 1,582- 245.87[(0.4 + 0.62/2)(0.4 + 0.62)] VII= 1,404kN b0 = 2(400 + 620/2) + (400 + 620) bo=2,440mm

V, =

t ffi (2,440)(620) =2,310,840 N

V, = 2,310.84 kN
v, = 1,964 kN > VII (OK)

319

320

REINFORCED CONCRETE DESIGN

The assumed depth is OK, governed by wide beam shear at column 1:

Longitudinal Reinforcement Moment at the face of column 1: x=0.3m Mu = 193.01(0.3)2 + 16.76(0.3)3 -1173(0.3) + 175.95 Mu = -158.13 kN-m b .. 1.57 + 0.4089(0.3) b=1.693m Moment at the face of column 2: X =4.5 -0.4 X""4.1 m M, == 193.01(4.1)2 + 16.76(4.1)3 -1173(4.1) + 175.95 M .. = -233.74 kN-m b = 1.57 + 0.4089(4.1) b=3.246m Maximum moment (point of zero shear) V = 50.27 x2 + 386.02 x- 1,173 =0 x=2.33m

.

M, = 193.01(2.33)2 + 16.76(2.33)3 -1173(2.33) + 175.95 M, = -1,297.3 kN-m b ... 1.57 + 0.4089(2.33) b=2.523m · Transverse Reinforcement At column 1: = 0.3 + 0.75d x=0.765m X

b = 1.57 + 0.4089(0.765) b= 1.883m Lt = (1.57- 0.3)/2 = 0.635 L2 = (1.883- 0.3)/2 = 0.7915 m L = (Lt + L2)/2., 0.713 m

M, =q, (x)(L2/2)

= 245.87(0.765)(0.7132/2)

Mu = 47. 81 kN-m

!Z!

CHAPTER 9 - FOOTINGS

Atcolumn2:

---

--- --- --- ---

... -- --- --Y1

I

I

a

~ --- --- ---

Xt •

0.4

b 0.4

--- --- ---

--- --- ---

+ 0.75d = 0.865 m

x = 4.5 - 0.865 = 3.635 m b =1.57 + 0.4089(3.635) =3.056 m Yt

= (3.056- 0.4)/2 =1.328 m

yz = (3.41 - 0.4)/2 = 1.505 m L = (y1 + yz)/2 = 1.4165 m

=qu (xt) (L2j2) = 245.87(0.865)(1.41652/2) Mu = 213.4 kN-m Mu

Pmln

14 • = 414

= 0.00338

= 0.75 Pb = 0 75 0.85(21)(0.85)(600) Pmox • 414(600 + 414) Pmax

Ab =

t

(~0) 2

= 314 mm2

3.41

=0.0163

322

REINFORCED CONCRETE DESIGN

, .,.·· iij; ...\\ J}.

............

~p;"'" ·

'

b,_(mm) Moment, Mu (kN-m) Ru,.

Mu .

fbd 2

r

l

p• 0.85/', - - [ 1- 1 -2Ru -fy

0.85 f'c

Usep A,• pbd Number of bars, N = A,j Ab UseN·· Location

.,,

e

1,523 1297.3

3,246 233.74

765 47.81

865 213.4

0.27

1.49

0.21

0.1806

0.7131

0.00066

0.00375

0.00051

0.000438

0.00176

0.0034 3569 11.4

0.00375 5866 18.7

0.0034

12 Top

19 Top

21.8 22

0.00338 1603 5.1 6

0.00338 1812 5.8 6

Top

Botto~

Bottom

6843

Using 16 mm bars with Jy = 275 MPa For b = 1000 mm: h =620 + 0.5(20) + 75 h-705mm

A., = 0.002bh

f

1,410 mm2

(16)2 N • 1,410

N•7.0127

Spacing •

1000 7.0127

=143 say 140 mm o.c.

Development length:

Lt = ldb ... 0.02 Abfy I

.[1';

Lt = 0.02 x 314 (414)/ J2l

E

1,693 158.13

Shrinkage and temperature bars:

A,, • 0.002(1000)(705) •

I!) ·

= 567 mm

or Lt = 0.06 dbfy =0.06(20)(414) =497 mm Minimum Lt furnished (transverse on at column 1) ;, 635 + 300 - 75 .. 860 mm (OK)

323

CHAPTER 9 ~ FOOTINGS

~--'-----

L = 4.5 m -------~

4-20 mm

PROBLEM 9.10

Given the following column properties and loads: , Column 1 400 mm x 400 mm 4- 25mm bars DL =480kN LL =350kN

Column2 450 mm x 450 mm 6-25 mm bars DL =640kN LL =510kN

The edge of column 1 is at the property line and the footing is 2.2 rn below the ground surface. The spacing of columns is 6.5 rn o.c.. q. = 200 kPa, Yc = 23.5 kN/rn3, Ys = 15.4 kN/rn3, /c = 27.5 MPa. Use 25 mm bars for footing and 28 mm bars for strap, with fy = 345 MPa. Use 16 mm temperature bars with fy = 275 MPa. SOLUTION

n

'·'l--

-.Xg

1'---:

q.

6.7m-~'l

325

CHAPTER 9 • FOOTINGS

In the previous problems, we start the design by assuming a value of tl. Another procedure is to assume a value of effective soil bearing capacity q,. qe must not exceed, qa- Ys hs = 200- 15.4(2) = 169.2 kPa Assume q. = 160 kPa Pt = 480 + 350 P, =830kN p2 = 640 + 510 P2 = 1,150kN

P= P, + P2 P= 1,980kN 1,980 qe 160 Atotal = 12.375 m2 p

Atotal = -

= --

At + A2 = 12.375 m2

~

Eq. (1)

For the soil pressure to be uniform, the centroid of A 1 and At must coincide with the resultant of Pt and P2. · p Xg = Pt Xt + p2 X2 1,980 Xg = 830(0.2) + 1,150(6.7) Xg"'3.975m

We will start by assuming a value of Lt until a desirable ratio L1/B1 is obtained (usually from 0.75 to 1) Try L, = 2.2 m A Xg = A,(L,/2) + A2(6.7) 12.375(3.975) == A,(1.1) + 6.7A2 At= 44.72- 6.091A2 Substitute At in Eq. (2) to Eq. (1): 44.72- 6.091A2 + A2 •12.375 A2 = 6.353m2 A,= 44.72- 6.091(6.353) At= 6.024 m2

7 Eq. (2)

326

REINFORCED CONCRETE DESIGN

[Al = LJ

X

81]

[A2 = L2 x 82]

6.024 = 2.2 X Bl 81 = 2.74m LJ/B1 = 0.8 (this appears to be reasonable) Using square footing, L2 = B2 6.353 = L22 L2 = 82 = 2.5205 say 2.53 m

Design of footing Pul = 1.4(480) + 1.7(350) Pu1 =1267kN

P112 = 1.4(640) + 1.7(510) Pu2= 1763 kN P11 = 1,267 + 1,763 P,. =3,030kN

'Attg =A1+ A2 A1 = 2.2(2.74) = 6.028 m2 A2 = 2.532 = 6.401 m2 Attng = 6.028 + 6.401 Attng = 12.429 m 2

_ Pu _ 3,030 q, - A ftg - 12.429 q,. = = 243.78 kPa Footing 1: · Solve for d from wide-beam shear:

Assume width of strap = 550 mm (larger than the column)

q,. = 0.24378 MPa V,. = q,. X Ashaded

b= 2200 mm

= 0.24378(2200)(1095- d)

1095- d

v,. = 536.316(1095- d)

t .Jf; bwd = .t .J27.5 (2200)d

Vr=

Vc = 1,923 d

~-----'L-----t

d

550 mm

L----....

327

CHAPTER 9 • FOOTINGS

[V, =
q, = qu- Yr he- Ys hs = 200- 23.5(0.36)- 15.4(1.84) q, = 163.204 kPa > 160 (OK) This means that the q, used in the design is lesser than the actual value.

Before we proceed with the design of bars, let us first solve the depth required for footing 2 so that we can check for q,. Since Footing 2 is square, punching shear will surely govern.

= Pu2 - q, X Ashaded = 1763 X103- 0.24378(450 + d)2 Ve = ! ..{1'; bo d

V, V,

=

t

'0

+

~27.5 [4(450 + d)](d)

0

~

Ve = 6.992(450d + cfl) [V,

=
Check for q,: he =343 + 0.5(25) + 75 =430.5 say 431 mm h.~ 2.2- 0.431 =1.769 m qe = qu - Yc he - Ys hs =200- 23.5(0.431)- 15.4(1.769) q, = 162.6 kPa > 160 kPa (OK)

•

328 '

REINFORCED CONCRETE DESIGN

Moment: 0.2~

6.5 m

L •

Footing 1 (transverse section): M .. = 243.78(2.2)(1.0952/2) M, = 321.53 kN-m b=2200mm d = 271 rnm Footing 2 (transverse section): M .. 243.78(2.53)(0.992/2) M;, = 302.24 kN-m b= 2,530mm d=343mm

=

Footing 2 (Longitudinal section): M, = 243.78(2.53)(1.042/2) • . M.1 : : 3~3.55 kN-m b= 2,530mm d = 343- 25 = 318 mm (longitudinal above transverse) Pmin

= 1.4/fy = 1.4/345

Pmin

= 0.00406

Pmax

'f'max

Ab =

= 0.75 Pb = 0.75 0.85(27.5)(0.85)(600) 345(345 + 600)

=0.0274

t (25)

2

= 491 mm2

.

CHAPTER 9 • FOOTINGS Section~

Moment, M, (kN-m) R, = M, (MPa) 2 . - +bd _ 0.85f', [ 1- ~1 2R, p---.-...-- -]

1

fy

0.85f'c

Usep As= pbd Number of bars, N = AJ_Ab UseN= Location

Footing1 Transverse

Footing2 Transverse

LongitudUial

321.53

302.24

333.55

2.21

1.13

1.45

0.00674

0.00336

0.00434

O.OQ674 4,018 8.18 9 Bottom

0.00406 3,523 7.2 8 Bottom

0.00434 3,492 7.1 8 Bottom

Shrinkage and temperature bars for Footing 1: (h = 360 mm) Using 16 mm bars with fy = 275 MPa

Forb =1000 mm: A., = 0.002 b h = 0.002(1000)(360) Ast=720mm2

f

(16)2 N = 720 N=3.58 . 1000 Spacmg= - 3.58 Spacing = 280 mm o.c . ./ Development length:

L.t = ldb = 0.02 Abfy I.[!':

L.t = = 0.02 x 491 (345)/ .J27.5 = 646 mm-~' or Ld = 0.06 db fy = 0.06(25)(345) Minimum Ld furnished Minimum Ld furnished

=518 mm

=990 + 550 - 75 =1,465 mm (OK)

Footing2

.

330

REINFORCED CONCRETE DESIGN

IE----2.53

___ ,, .. "---- . . ....

'' ''

~ , "'

--------------- ..... --- _..

'

Moment Diagram

"

At section A-A: M, = Rut(1.1)- Put(2) = 243.78(2.2)(2.74)(1.1)- 1267(2) Mu = -917.54 kN-m

Vu =Rut- "Put = 243.78(2.2)(2.74) - 1267

V, =202.5kN Depth of beam based on beam shear:

='+t

Vu Vc Vu = .{f; b., d, where bw =550 nun 202.5 X 1()3 = 0.85

t

.J27.5 (550)d

d=495.6mm

Depth of beam based on moment: · Use

= 0. p

6

Pb

= _ 0.85(27.5)(0.85)(600) 06 · 345(345 + 600)

p = 0.0219

...-......'\·..

331

CHAPTER 9 - FOOTINGS

w=pjy/fc = 0.0219(345)/275 (J) = 0.275

fvr" = ~ !c w b d2 (1- o.59 w) 91754 X 106 = 0.9(27.5)(0.0275)(550) f12 (1 - 0.59 X 0.275) d = 541 nun./ Used= 550mm RII-

Mu

~bd2

917.54 X 10 6 0.9(550)(550) 2 Ru = 6.128 MPa

= p

0.85(27.5) [1- 1 345

p = 0.021

A,= pbd = 0.021(550)(550) A, = 6,353 mm2

N= 6,353 t(28)2

N = 10.32 say 11 bars

16-mm temp. bars @280 mmo.c.

2(6.128) 0.85(27.5)

l

332

REINFORCED CONCRETE DESIGN

SUPPLEMENTARY PROBLEMS PROBLEM 9.11

Design a square footing to support a 500 mm x 500 mm column to carry an axial dead load of 650 kN and an axial live load of 570 kN. Use 20 mm main reinforcing bars withfy = 345 MPa. Assumefc = 27.5 MPa, y,. = 23.5 kN/m3, Ys = 18.2 kN/m3, depth of footing= 1.8 m.

PROBLEM 9.12

Design a rectangular column footing to carry the following column loads: PoL= 380kN MoL = 125 kN-m PLL = 275kN MLL=98kN-m

The column is 400 mm x 400 mm and is reinforced with 6-25 mm bars. The base of footing is 1.6 m below the natural grade and the allowable soil pressure is 220 kPa. Design the footing such that the soil pressure at the base is uniform. Take L = 1.68 and use f c = 28 MPa and fy = 414 MPa. Use 20 mm ptain bars.

PROBLEM 9.13

Design a wall footing to carry the following loads: PoL= 180 RN/m PLL = 145 kN/m MDL=57kN/m

MLL=36kN/m

f,

Wall thidness is 300mm. = 27.5 MPa, fy = 345 MPa, Yt =;23.5 kN/in3, Ys = 17.8 kN/m3, q. = 180 kPa. The footing is 2m below the ground: Use 20 ritin main bars.

333

CHAPTER 9 - FOOTINGS

PROBLEM 9.14

Design the combined footing to support the two columns shown. The base of footing is 1.9 m below the ground surface. Use the following data: Yconr •· 24 kN/m 3, Ysoil = 18 kN/m 3,fv = 275 MPa,f,. = 27.5 MPa. Use 25 mm diameter main bars. All_owable soil bearing pressure, q., = 170 kPa Column 1: = 460 kN PLL = 380 kN

Prn

Column 2: Pot= 530kN PLL = 475 kN

PROBLEM 9.15

Given the following column properties and loads: Column 1 Column 2 300 mm x 300 mm 380 mm x 380 mm 6- 25mmbars 4-25 mm bars DL =470kN DL = 380kN LL =435 kN LL = 320kN

~~.- - - - -

~flj 8.,

~: Column 1

4.0m

----~.~

~~ ~

Column 2 : ~

334

REINFORCED CONCRETE DESIGN

Design a suitable trapezoidal-shaped footing. Use f, = 28 MPa, h = 375 MPa, and assume q. = 135 kPa. Use 20 mm main bars and 16 mm temperature bars with fy = 275 MPa.

PROBLEM 9.16

Given the following column properties and loads: Column 1

.

400 mm x 400 mm 4- 25mm bars DL=520kN LL=410kN .

Column 2 500 mm x 500 mm 6-25mmbars DL =690kN LL =545kN

The edge of column ~ is at the property line. The spacing of columns is 7 m o.c.. Use 25 mm bars for footing and 28 mm bars for strap, withfy = 345 MPa. Use 16 mm temperature bars withfy = 275 MPa. Assumefc = 28 MPa. Assume q. = 180 kPa.

CHAPTER 10- TWO-WAY SLAB

335

Chapter 10 Two-way Slab When a rectangular reinforced-concrete slab is supported on all four sides, reinforcement placed perpendicular to the side may be assumed effective in the two directions. These slabs ~e known as two-way slabs. The bending on these slabs occurs in both directiOns. However, if a rectangular slab is supported in all four sides but the long side is two or more times the short side, the slab will, for all practical purposes, act as a one way slab, with' bending occurring in the short direction.

Figure 10.1: Bending of two-way slab

The Code specifies two methods of designing two-way slabs. These are the direct design method (Section 5.13.6) and equivalent frame method (Section 5.13.7). However, there are other methods that can be used. These include the strip method and moment coeffidents method (Method 2).

COLUMN AND MIDDLE STRIPS When the design moments have been determined by either the direct design method or equivalent frame method, the moments are distributed across each panel. The panel is divided into column and middle strips. Column strip is a design strip with a width on each side of a column centerline equal to 0.25 x L2 or 0.25 x Lt, whichever is less. Column strip includes beams, if any. The middle strip is a design strip bounded by two column strips.

336

REINFORCED CONCRETE DESIGN

Middle Sbip

0.25 Lt or 0.25 Lz whichever Is smaller

0.25 L, or 0.25 Lz whichever Is smaller

, Flgu~ 10.2: Column and middle strips

MINIMUM SLAB THICKNESS (SECTION 5.9.5.3.2) • The minimum thickness of slabs without interior beams spanning between the supports shall be in accordance with the provisions of Table 10.1 and shall not be less the following values: (a) Slabs without drop panels ........................................................ 125 mm (b) Slabs with drop panels .......................... :................................... 100 mm Table "10.1: Minimum Thickness of Slabs without Interior beams Without drop panels Note (2)

With drop panels Note (2}

Yield Stress

fy, MPa Note (1)

ExteriOr panels

Interior panels

Without With edge edge beams Note (3) beams

(1) (2) (3)

Exterior panels

Interior panels

Without With edge edge beams · beams Note(J}

275

l.J33

l.J36

LJ36

LJ36

L.J40

l.J40

415

LJJO

LJ33

LJ33

l.J33

l.J36

l.J36

For values d reinfortement yield stress between 275 and 415 MPa minimum thickness shaH be obtained by linear InterpolatiOn. · Drop panel Is deftned In Sections 5.13.4.7.1 and 5.13.4.7.2. Slabs with beams b!!tween cOlumns along exterior edges. The value d a for the edge beam shall not be less than 0.8.

337

CHAPTER 10- TWO-WAY SLA6

The minimum thickness of slabs with or without beams spanning between the supports on all sides and having a ratio of long to short span not exceeding 2 shall be h=

L (800 + 0.73 /y) ·

11 ----------"---,-----

Eq. 10-1

L 11 (800 + 0.73 JlJ) .

Eq. 10-2

36,000+ 5,000~[am -0.12(1 + 1/~)]

but not less than It=

36,000 + 9,000~ and need not be more than L 11 (800 + 0.73/y) h =------=-. 36,000

Eq. 10-3

The values obtained from Eq. 10- 1, Eq. 10- 2, or Eq. 10- 3 shall be modified as required by Sec. 5.9.5.3.4 and Sec. 5.9.5.3.5 but in no case shall the thickness be less than (a) for am < 2.0 ······················· ······ ······················································ 125 mm ~ 2.0 ..................................................................................... 90 mm

(b) for a,.

Section 5.9.5.3.4: For slabs without beams, but with drop panels extending in each direction from centerline of support a distance not less than one-sixth the span length in that direction measured center-to-center of supports, and projection below the slab at least one-quarter the slab thickness beyond the drop, thickness required by Eq. 10- 1, Eq. 10- 2, or Eq. 10- 3 may be reduced by 10%. Section 5.9.5.3.5: At discontinuous edges, an edge beam shall be provided with a stiffness ratio a not less than 0.80; or the minimum thickness required by Eq. 10 - 1, Eq. 10 - 2, or Eq. 10 - 3, shall be increased by at least 10 % in the panel with a discontinuous edge. where: L,

= length of clear span in long direction of two-way construction, measured face-to-face of supports in slabs without beams and face-toface of beams or other supports in other cases. a 111 = average value of a for all beams on edges of a panel.

338

REINFORCED CONCRETE DESIGN

a = ratio of flexural stiffness of beam section to flexural stiffness a width of slab bounded laterally by centerline of adjacent panel (if any) in each side of beam.

I

Eq. 10-4

p = ratio of clear spans in long to short direction of two-way slabs. E,,, =modulus of elasticity of beam concrete E,, =modulus of elasticity of slab concrete I, = moment of inertia about centroidal axis of gross section of beams as

defined in Sec. 5.13.2.4. Section 5.13.2.4: For monolithic or fully composite construction, a beam indudes that portion of slab on each side of the beam extending a distance equal to the projection of the beam above or below the slab, whichever is greater, but not greater than four times the slab thickness.

l, = moment of inertia about centroidal axis of gross section of slab Is= Jt3..!12 times width of slab defined in notations a and ~ 1

The student may find this Code procedure in solving the nummum slab thickness very tedious, but for slabs up to 8 m in length. and with ~ams in all four sides having almost the same size, the minimum slab thickness is usually not governed by Eq. 10- 1.

DIRECT DESIGN METHOD (SECTION 5.13.6)

Limitations of Direct Design Method 1. There shall ~a minimum of three continuous spans in each -direction. 2. Panels shall be rectangular with a ratio of longer to shorter span centerto-center of supports within a panel not greater than 2. 3. Successive span lengths center-to-center of supports in each direction shall not differ by more than one-third the longer span. 4. Columns ~ offset a maximum of 10 percent of the span (in direction of offset) from either axis ~tween centerlines of successive columns. 5. All loads shall ~ due to gravity ori.ly and uniformly distributed over an entire panel. Live load shall not exceed three times dead load. 6. For a panel with beams between supports on all sides, the relative stiffness of beams in two perpendicular directions.

339

CHAPTER 10 -TWO-WAY SLAB

Eq. 10-5

and shall not be less than 0.2 nor greater than 5.0. where: L1 = length of span in direction that moments are being determined, measured center-to-center of supports. L2 = length of span transverse to L1, measured center-to-center of supports. See also Figure 10.2.

Moments in Slabs (Section 5.13.6.2) The total moment that is resisted by the slab equals absolute sum of positive and average negative factored moments in each direction shall not be less than

Eq. 10-6 where w, is the factored load in Pa or kPa. If the transverse span of panels on either side of the centerline of supports varies, L2 in Eq. 10- 6 shall be taken as the average of adjacent transverse spans. When the span adjacent and parallel to an edge is being considered, the distance from edge to panel centerline shall be substituted for L2 in Eq. 10- 6.

Clear span L, shall extend from face to face columns, capitals, brackets, or walls. Value of L,, used in Eq. 10 - 6 shall not be less than 0.65LJ. Circular or regular polygon shaped supports shall be treated as square supports with the same area.

Negative and Positive Factored Moments (5.13.6.3) Negative factored moments shall be located at face of rectangular supports. Circular or regular polygon shaped supports shall be treated as square supports with the same area.

A. In an interior span, total static moment Mo shall be distributed as follows: Negative factored moment ................................................. 0.65 Positive factored moment·······················'···························· 0.35

340

REINFORCED CONCRETE DESIGN

B. In an end span, total factored static, moment Mo shall be distributed as given in Table 10.2. Table 10.2: Distribution of total span moment in an end span

Exterior edge unrestrained

Slab with beams between all supports

0.75

0.70

0.70

0.70

0.65

0.63

0.57

0.52

0.50

0.35

0

0.16

0.26

0.30

0.65

Negative moment sections shall be designed to resist the larger of the two interior negative factored moments determined for spans framing into a common support unless an analysis is made to distribute the unbalanced moment in accordance with stiffness of adjoining eleptents. Edge beams or edges of slab shall be proportioned to resist in torsion their share of exterior negative factored moments.

'

For moment transfer between slab and an edge column, column strip nominal moment strength provided shall be used as the transfer moment for gravity lbad. Factored Moments in Column Strips

Column strips shall be proportioned to resist the following portions in percent of interior negative factored moments: Table 10.3

I:Jh (ati;Jh) =0

(aM1~)
0.5 75 90

1.0 75 75

2.0 75 45

Unear interpolation shall be made between values shown.

Ml

CHAPTER 10- TWO-WAY SLAB

Table 10.4: Interpolated values of Table 10.3 Ll/L,

a,L2fl,

uo

0.60

0.70

0.80

0.90

1.00

1.10 75.00

1.20

1.30

75.30 75.00 74.70

74.40

0.20 '

78.00

77.40 76.80 76.20

75.60 75.00 74.40

73.80 73.20 72.60

74.10 73.80

74.10 73.20 72.30 71.40

76.20 75.00

73.80 72.60 71 .40

0.50

82.50 81.00 79.50 78.00

76.50 75.00

73.50 72.00

77.70

0.60

64.00 82.20 80.40 78.60

76.80 75.00 73.20

0.70

85.50 83.40 81.30 79.20

n.10 75.00

0.80

71.40

75.00 71.00

72.60 72.30 72.00

75.00

73.50 73.20

75.00 75.00

75.90 75.60

79.50 78.60

75.00

72.90

75.00 75.00

75.00 75.00

76.50 76.20

81.00 79.80 78.60 77.40

75.00

1.70

75.00 75.00

0.30

uo

1.60

0.10

0.40

1.80

1.50

0.00

76.80 75.90 75.00

75.00 75.00

1.40

72.00

71.40 70.80

70.20 69.60

Ul

69.00

70.50 69.60 86.70 67.80 86.90 86.00

70.20 69.00 67.80 86.60 65.40 64.20 63.00

70.50 69.00 67.50 86.00 64.50 63.00

61.50 60.00

69.60 67.80 86.00 64.20 62.40

58.80 57.00

60.60

72.90 70.80 68.70 86.60 64.50 62.40

60.30 58.20 56.10 54.00

87.00 64.60 82.20 79.80 n.40 75.00

72.60 70.20 87.80 6540 63.00

58.20 55.80 53.40 51.00

0.90

68.50 85.80 83.10 80.40 n .10 75.00

72.30 89.60 86.90 64.20 81.50 58.80 56.10 53.40

~1.00

10.00 87.00 84.00 81 .00

78.00 75.00

72.00 89.00 86.00 83.00 60.00

60.60

57.00 54.00

50.70 48.00

51.00 48.00 45.00

Column strips shall be proportioned to resist the following portions in percent of exterior negative factored moments: Table 10.5 0.5 100 75 100 90

L:z/L1 (a1Lz/L1)

=0

(a1lz/lt) ~ 1.0

fu =0 Bt;:: 2.5

at= o

Bt;:: 2.5

1.0 100 75

2.0 '100 75

100

100

75

45

Linear interpolation shall be made between values shown, Wher~ supports consist of columns or walls extending for a distance equal to or greater than three-quarters the spah length L2 used to compute Mo, negative moments shall be considered to be uniformly distributed across ,L2.

Column strips shall be proportioned to resist the following portions in percent of positive factored moments: Table 10.6 L:z/L (atlz!Lt) = 0 ( a1L:zll1) ;;:: 1.0

0.5 60 90

1.0 60 75

2.0 60 45

Linear interpolations shall be made between values shown.

342

REINFORCED CONCRETE DESIGN Table 10.7: Interpolated values of Table 10.6

L2/ L,

u 1LjL,

0.50

0.60

0.70

0.80

0.90

1.00

1.10

1.20

1.30

1.40

60.00 60.00

1.50

1.60

1.70

1.80

1.90

2.00

60.00 60.00 60.00 60.00 60.00 60.00

0.00

60.00 60.00

60.00 60.00

60.00 60.00

60.00

60.00

0.10

63.00

62.70

62.40

62.10

61.80

61.50

61.20

60.90 60.60 60.30

0.20

66.00 65.40

64.80

64.20

63.60

63.00

62.40 61 .80 61.20

0.30

69.00

68.10

67.20 66.30

65.40 64.50 63.60

62.70

61.80 60.90

60.00

59.10 58.20 57.30 56.40 55.50

0.40

72.00

70.80

69.60 68.40

67.20 66.00

64.80

63.60

62.40

61.20

60.00

58.80 57.60 56.40 55.20 54.00

0.50

75.00

73.50

72.00

69.00

67.50

66.00

64.50

63.00

61.50 60.00 58.50 57.00 55.50 54.00 52.50

70.50

60.00

59.70 59.40 59.10 58.80 58.50

60.60 60.00

59.40 58.80 58.20 57.60 57.00

0.60

78.00

76.20

74.40

72.60

70.80

69.00

6720

65.40

63.60 61.80 60.00

0.70

81.00 78.90

76.80

74.70

72.60

70.50

68.40

66.30

64.20 62.10

0.80

84.00 81.60 79.20

76.80

74.40 72.00

69.60

67.20 64.80

76.20

81.60 78.90

60.00

62.40 60.00

58.20 56.40 54.60 52.80 51.00 57.90 55.80 53.70 51.60 49.50 57.60 55.20 52.80 50.40

48.00

.0.90

87.00 84.30

73.50

70.80 68.10

65.40 62.70 60.00

~1.00

90.00 87.00 84.00 81.00 78.00 75.00

72.00 69.00

66.00 63.00 60.00 57.00 54.00 51.00 48.00 45.00

57.30 54.60 51.90 49.20 46.50

For slabs with beams between supports, the slab portion of column strips shall be proportioned to resist that portion of column strip moments not resisted by beams.

Factored Moments in Beams (Section 5.13.6.5) Beams between supports shall be proportioned to resist 85 percent of column strip moments if (a.1L2/L1) is equal to or greater than LO. For values of (a.1L2/ L;) between 1.0 and zero, proportion of column strip moments resisted by beams shall be obtained by linear interpolation between &; and zero percent.

Factored Moments in Middle Strips That portion of negative and positive factored moments not resisted by column strips shall be proportionately assigned to corresponding half middle strips. Each middle strip shall be proportioned to resist the sum of the moments assigned to its two half rriiddle strips. A middle strip adjacent to and parallel with an edge supported by a wall shall be proportioned to resist twice the moment assigned to the half middle strip corresponding to the first row of interior supports. Modification of Factored Moments Negative and positive factored moments may be modified by 10 percent provided the total static moment for a panel in the direction considered is not less than that required b.y Eq. 10- 6. ·

343

CHAPTER 10- TWO-WAY SLAB

'

'

Factored Shear in Slab System with Beams Beams with (a.tL2/Lt) equal to or greater than 1.0 shall be proportioned to Nlilt shear caused by factored loads on tributary areas bounded by 45° lines drawn from the comers of the panels and the center-lines of the adjacent panels parallel to the long sides. Beams with (a.tL2/Lt) less than 1.0 may be proportioned to resist sh:ear obtained by linear interpolation, assuming beams carry no load at a. =0.

rj c.s. for wide beam shear

~

bw·-·t ···-+;;.~~=~-~~·=:r·~-=~~-jj__·_~~~~+' I

i

!

',

••.

X' ', ..

I I

i i

: i i i

/

··..

'

"~~

/

,/

_,/-jl~·-..

~

i i LU2 ·I. I i i

l

/

...... ,.., ,,' ;-.· . ',

r

I

:

Lz

i i / ~ i j45" / ••• i i / ••• i ~.'.:.·-··-·-·-·-·-·-·-;-·-·-·~·-·-·-·-·-·~~ .............~..............

I

/

/

',

/

••.

REINFORCED CONCRETE DESIGN

344

ILLUSTRATIVE PROBLEM PROBLEM 10.1

Using the NSCP Specifications, f,ietermine the minimum slab thickness for the exterior panel shown. The slab has beam between all supports which are poured monolithically with the slab. Use fy • 414 MPa and f, • 21 MPa. Assume E, be the same for slab, beam, and column.

sm~

SmTSm a-

1

Panel to be designed

At

6

tA

-r-

a-

.

6m

I

il

350mm

Section

A-A

Section a-a

I 350mm

345

CHAPTER 10- TWO-WAY SLAB

SOLUTION

1.

Ln (800 + 0.73 /y) Assume h = - - - - - - = 36,000 + 9,ooop

p=

6f-

longclearspan shortclearspan

6000-350 5000-350 p = 1.22

h = 5650(8oo + o:73 x 414) 36,000 + 9,000(1.22) h = 133 nun say 150 nun 2.

Effective flange projection of beams (Section 5.13.2.4) a) 500 - 150 = 350 mm b) 4h = 4(150) = 600 mm

3.

The value of I is computed from that of a T-beam. This procedure, however, is very tedious. From computer calculation, the author found that for edge beam, with slab on one side only, I"" 1.4 bH3/12 and for interior beams with slab on both sides, I"" 1.6 bd3 /12, where /1 is the beam width and d is the total depth of beam. Moment of inertia of the beam (approximate value): 350(500) 3 For edge beam, I= 1.4 x ---''----'12 I= 5,104 xl06 mm4 . . 350(500) 3 For interior beams, I = 1.6 x ---'---'-12 I = 5,833 x 106 mm4

4.

Value of a Ecb :xI of beam a = ____:;:. ,____ _ Ecs xI of slab

Ecb = Ers = Ec For edge beam with 3 m slab width:

an=

5104x10 6

-----=--3000(150)3 112

a.= 6.05

_346

REINFORCED CONCRETE DESIGN

For interior beam with 5-m slab width: (2 beams) 5833x10 6 Cl.b = -....,-,- - - ; ; - 5000(150)3 /12 Cl.b

= 4.15

For interior beam with 6-m slab width: 5833x10 6 Cl.c=---~6000(150)3 /12 Cl.c = 3.46 , Avera~e, Cl.m

= a n + 2ab +a c

4 6.05 + 2( 4.15) + 3.46 4

Average, Cl.m

5

.

~s

= 4.45

= length of co~tinuous edges penmeter

2(6) + 5 2(6) + 2(5) ~s = 0.773 =

6.

L" = 6000 - 350 L" =5650mm

h=

+

L 11 (800 0.73 /y) <

<

36,000 + 5,000~[ Cl. Ill - 0.12(1 + 1/13)] 5650(800 + 0.73 X 414) 36,000+ 5,000(1.22)[4.45- 0.12(1 + 1/1.22)] h = 101 mm

but not less than: L11 (800 + 0.73/y)

h=-'----~

36,000 + 9,000~

= 5650(800+ 0.73x 414) 36,000 + 9,000(1.22) h = 133mm

•

CHAPTER 10- TWO-WAY SLAB

but need not be more than: Ln (800 + 0.73/y) h = ------"-36,000 . _ 5650(800+0.73x414) 36,000 h=173mm Also, h may not be less than 90 mm (for a, > 2), see Page 337 Thus, hmin = 133 mm

PROBLEM 10.2

Design the slab in Problem 10.1 assuming that the floor carries a uniform live load of 5.7 kPa and a uniform dead load of 1.3 kPa not including its own weight. Use 12-mm main bars. Solution

Useh

=150mm

Sm

Floor weight = Yconc x slab thickness = 23.5 X 0.15 Floor weight = 3.53 kPa

2.5 m

ri ·i4s• '-·- ·- ·- :- ·- ·- · ·

l!! : · · ·. .··..

Total dead load= 1.3 + 3.53 Total dead load = 4.83 kPa

I I

w,. = 1.4(4.83) + 1.7(5.7) = 16.452 kPa

L2 L; = 4.15(5/6)

0.]

.!2 = 3.45 > 1 Ll

2.5..;. 0.35/2- 0.124 x=2.201 m X=

_...··.//_.·

•, '•,

r

i

I

I

i

/

).~·· r ,'

I I

/ /

I

0.)

,'

\m:~»\li:ll••~m~~%~~~::.. ~. b

Using 12 mm bars: d = 150 - ¥2(12) - 20 d=124mm Check the depth for shear: (Sect. 5.13.6.8)

· - · - · - · - · -45~~7i

I'

_l ~ .....

T: / . y'

,'

•,

', ', , ',

·· ..,

··.. •

I I

[1\-·-·-~-·-·-·-·- - - - - -· ~·~

-+J

~

350

"---1 c.s. for wide beam shear

318

REINFORCED CONCRETE DESIGN

Taking b =1m V,. = W 11 X Ast.aded = 16.452(2.201)(1) V, =36.21 kN

t = t

V,=

.{J';bd

.,fii (1000)(124)

V, = 94,706 N

• v, = 0.85(94.706)

+V, = 80.5 kN > V, (OK) Momenhlong the short span (5-m interior span): •

Note: This an interior span, so Code Sect. 5.13.6.3.2 applies: (See Page 339)

Mo = (wuL2 )Ln 2 8 L, = 5-0.35 . L, _= 4.65m L2=6m

Mo = (16.452 X 6)(4.65) 2 8 Mo = 266.8 kN-m Negati've factored moment = -0.65(266.8) Negative factored moment= -173.42 kN-m Pos{tive factored moment = 0.35(266.8) Positive factored moment = 93.38 kN-m Distributing these moments to beam and column strips: L2/Lt = 6/5 . L2/Lt = 1.2 Clt = a, = 3.46 (in the direction of Lt) at(L2/ Lt) = 4.15 From Table 10.4 the percentage of interior negative moment to be resisted

by co~umn strip is 69%(-173.42) = -119.66 kN-m.

CHAPTER 10- 'T'NO·WAY SLAB

According to Section 5.13.6.5 (See 342), 85% of -119.66 • -101.71 kN·m wtll be resisted by the beam, and 15% of -119.66 = -17.95 kN-m to the slab. The remaining -(173.42 -119.66) = -53.76 is allotted to the middle strips. Fr?m Table 10.7, the,percentage of the positive moment to be resisted by column strip is 69%(93.38) .. 64.43 kN-m. 85% of 64.43 = 54.77 kN-m goes to the beam and 15% of 64.43 = 9.66 kN-m goes to the slab. The remaining 93.38 - 64.43 = 28.95 is allotted, to the middle strips. Moment along the short span (along edge beam): According to section 5.13.6.2.4: L2 = 6/2 + 0.35/2 L2 =3.175m L, = 5-0.35 L, =4.65m M., = (wuL2 )Ln 2

8 = (16.452 X 3.175)(4.65) 2

.8 M., =141.18 kN-m

Negative factored moment =-0.65(141.18) Negative factored moment • -91.78 kN-m Positive factored moment= 0.35(141.18) Positive factored moment= 49.40 kN-m For this case, Table 10.5 will be used for distribution of negative moments

13, = E,b C

350

2E,5 15

E.,.= Ecs = E, C=

1:(1-0.63~ )x:y

350

3

3

= (t- o.63 350) 350 (500) + ( 1 _ 0.63 t5o) 150 (350) 500 3 350 3 C • 4282 x 10' mm4

350

REINFORCED CONCRETE D.ESIGN 3

I = 3000(150) < 12 I,= 843.75 x 106 mm4

Pt

4282x 10 6 = 2(843.75 X 10 6 )

p, = 2.54 L2/L1

=

6/5 = 1.2

ex, = ex. = 6.05 (for edge' beam) exl (L2/ LJ) = 7.26

By interpolation from Table 10.5: 1-12 1-2

Percentage = 75 - - -·- (75 - 45) Percentage = 69% Exterior Negative Moment: Column strip= 69% x (-91.78) Column strip = -63.33 kN-m Beam= 85%(-63.33) Beam = -53.83 kN-m Slab= 15%(-63}3) Slab = -9.5 kN-m Middle Strip= -(91.78- 63.33) Middle Strip = -28.45 kN;.m Positive Moment (Percentage = 69% from Table 10.7) Column strip =69% x (49.4) Column strip = 34.1 kN-m Beam= 85%(34.1) Beam= 28.99 kN-m Slab= 15%(34.1) Slab= 5.12 kN-m Middle Strip= (49.4- 34.1) Middle Strip = 15.3 kN-m

'*

CHAPTER 10- TWO-WAY SLAB·

strip ~

"'.,;

'+

..."' ~

~fll ":lEI

~~ .....

...":lEI ' 't'

'!l

E

"'Pi

If ;I

1!3';

~fll

H

strip

Moment along the long span (6 m end span) L2=5m Ln =6- 0.35 Ln=5.65m

Lz

=5 m

Mo = (wu L2)Ln 2 ' 8 = (16.452 X 5)(5.65) 2

8 Mo = 328.24 kN-m From Column 8 of Table 10.2: Factored interior negative moment = -0.7(328.24) Factored interior negative moment = -229.77 kN-m Factored positive moment =0.57(328.24) Factored positive= 187,1 kN-~ Factored exterior negative moment= -0.16(328.24) Factored exterior negative moment = = -52.52 kN-m

L2/Lt = 5/6 L2/Lt = 0.83

/

352

REINFORCED CONCRETE OEfGN

a1 =ab=4.15 a1 (Lz/ L1) = 4.15(0.83) a1(Lz/L1) = 3.44 From Table 10.4 Percentage of negative moment= 81- 2_ (81-78) . 10 Percentage of negative moment = 80.1% Interior Negative Moment: Column strip= 80.1% x (-229.77) Column strip = -184 kN-m Beam= 85%(-184) Beam= -156.4 kN-m Slab= 15%(-184) Slab = -27.6 kN-m Middle Strip= -(229.77 -184) Middle Strip"" -45.77 kN-m Exterior Negative Moment: (80.1% by interpolation from T&ble 10.5) Column strip= 80.1% x (-52.52) •. Column strip =-42 kN-m Beam= 85%(-42) Beam = - 37.5 kN-m Slab= 15%(-42) Slab = -6.3 kN-m Middle strip = -(52.52 - 42) Middle strip= -10.52 kN-m Positive Moment (80.1% from Table 10.7) Column strip= 80.1% x (187.1) Column strip = 150 kN-m Beam= 85%(150) Beam= 127.5 kN-m Slab= 15%(150) Slab = 22.5 kN-m Middle Strip= 187.1-150 Middle Strip = 37.1 kN-m

CHAPTER 10 -TWO-WAY SLAB

353

Note: The student must understand that the column strip exists in both sides of the beam. Since we are to consider only the part on one side, the value of the moment allotted to slab must be divided by 2. However, the middle strip in no longer divided by 2 because the same moment is also all<,?tted to it by the opposite column strip.

Ab =

f

(12) 2

Ab=113mm2

1.4 Pmin = 414 Pmin = 0.00338 = 0 75 0.85(21)(0.85)(600) Pmax . 414(600 + 414) Pmax =0.01626

354

REINFORCED CONCRETE DESIGN

E

!G

...i

1.2sm

'

2.Sm

1.2Sm

CHAPTER 10- TWO-WAY SLAB

According to Section 5.13.4.1, reinforcement in each direction shall not be less than the required spacing for shrinkage and temperature bars. Temperature bars: A,,= 0.0018(1000)(150) = 270 mm2; N =2.39 Required Spacing= 1000/2.39 =418 mm < 260 Maximum spacing of bars (Section 5.13.4.2) • 2 x slab thickness =300 mm

e ~-+++......,liT 1.0

t+-HH--l

12 mm ' @ 260 11lm,

bothways bent at

1.25 m from middle of beam

356

REINFORCEQ CONCRETE DESIGN

CHAPTER 11 -ALTERNATE DESIGN METHOD (WORKING STRENGTH)

357

Chapter 11 Alternate Design Method (Working Strength) NSCP 2001 (ClOl-01) NOTATIONS Ag = gross area ofsection, znm2 Av =area of shear reinforcement within a distances, mm2 A,= loaded area A2 = maximum area of the portion of the supporting surface that is geometrically similar to and concentric with the loaded area bo = perimeter of critical section for slabs and footings, mm bw = web width, or diameter of circular section, mm d . = distance from extreme compression fiber to centroid of tension reinforcement, mm Ec = modulus of elasticity of concrete, MPa. Es = modulus of elasticity of reinforcement, MPa fc = specified compressive strength of concrete, MPa = square root of specified compressive strength concrete, MPa

Jl':

fc 1 = average splitting tensile strength of lightweight aggregate concrete, MPa

/s = permissible tensile stress in reinforcement, MPa

fy = specified yield strength of reinforcement, MPa M = design moment n = modular ratio of elasticity = E./ Ec N = design axial ,load normal to cross section occurring simultaneously with V; to be taken as positive for compression, negative for tension, and to include effects of tension due to creep and shrinkage s = spacing of shear reinforcement in direction parallel to longitudinal reinforcement, mm v = design shear stress Vc = permissible shear stress carried by concrete, MPa V" =permissible horizontal shear stress,.MPa V =design shear force at section a = angle between inclined stirrupsand longitudinal axis of member ~c =ratio of long side to short side of concentrated load or reaction area p11• = ratio of tension reinforcement = As/ bw d cp = strength reduction factor

358

. REINFORCED CONCRETE DESIGN

424.2 SCOPE

424.2.1 Non-prestressed reinforced concrete members shall be permitted to be designed using service loads (without load factors) and permissible service load stresses in accordance with provisions of Section 424. 424.2.2 For design of members not covered by Section 424, appropriate provisions of this code shall apply. 424.2.3 All applicable provisions of this code for nonprestressed concrete, except Section 408.5, shall apply to members designed by the Alternate Design Method. 424. 2.4 Flexural members shall meet requirements for deflection control in Section 409.6, and requirements of Sections 410.5 through 410.8 of this code .

.

424.3 GENERAL

424.3.1 Load factors and strength reduction factors ~ shall be taken as unity for membe;rs designed by the Alternate Design Method. 424.3.2 It shall be permitted to proportion members for 75 percent of capacities required by other parts of Section 424 when considering wind or earthquake forces combined with other loads, provided the resulting section is not less than that required for the combination of dead and live load. 424.3.3 When dead load reduces effects of other loads, members shall be designed for 85 percent of dead load in combination with the other loads. 1 424.4 PERMISSIBLE SERVICE LOAD STRESSES

424.4.1 Stresses in' concrete shall not exceed the following: 1. Flexure:

e Extreme fiber stress in compression .. 0.45 f.2. Shear:

e

Beams and one-way slabs and footings : • Shear carried by concrete, l'.- ........................................................ 0.38

.J7':

• Maximumshear carried by concrete plus shear reinforcement, Vc ............................................... : ..........• 0.38

.J7':

e Joists: • Shear c1.1rried by concrete, v.- .........................................·............... 0.09

.J7':

CHAPTER 11 - ALTERNATE DESIGN METHOD (WORKING STRENGTH)

359

e Two-way slabs and footings: • Shear carried by concrete, v .. .... ....................... . but not gre~ter than

t ..jf;

2. Bearing on loaded area .................. .............. ..... :............. ............................. 0.3 f,

424.4.2 Tensile stress in reinforcement shall not exceed the following: 1. Gmde 275 reinforcement ................................................................ .. ..... 140 MPa 2. Grade 415reinforcement or greater and welded wire fabric (plain or deformed) ............................................._.. 170 MPa 3. For flexural reinforcement, 10 mm or less in diameter, in one-way slabs of not more than 4 m span ................................................ 0.50fv but not greater than 200 MPa

424.5 DEVELOPMENT AND SPLICES OF REINFORCEMENT

424.5.1 Development and splices of reinforcement shall be as required in Section 412 of this Chapter. 424.5.2 In satisfying requirements of Section 412;12.3, M11 shall be taken as computed moment capacity assuming all positive moment tension reinforcement at the section to be stressed to the permissible tensile stress f. and Vu shall be taken as unfactored shear force at the section.

424.6 FLEXURE

For investigation of stresses at service loads, straight-line theory (for flexure) shall be used with the following assumptions: 424.6.1 Strains vary linearly as the distance from the neutral axis, except for deep flexural members with overall depth-span ratios greater than 2/5 for continuous spans and 4/5 for simple spans, a nonlinear distribution of strain shall be considered. 424.6.2 Stress-strain relationship of concrete is a straight line under service loads within permissible service load stresses.

360

REINFORCED CONCRETE DESIGN

424.6.3 In reinforced concrete members, concrete resists no tension. 424.6.4 It shall be permitted to take the modular ratio, n = Es/ E,. as the nearest

whole number (but not less than 6). Except in calculations for deflections, value of 11 for lightweight concrete shall be assumed to be the same as for normal weight concrete of the same stret'lgth. 424.6 5 In doubly reinforced flexural members, an effective modular ratio of 2E,f E, shall be used to transform compression reinforcement for stress

computations. Compr~sive stress in such reinforcement- shall not exceed permissible tensile stress. 424.7 COMPRESSION MEMBERS WITH OR WITHOUT FLEXURE ~4.7.1 Combined flexure and axial load capacity of compression members shall .be taken as 40% of that computed in accordance with provisions in Section 410 of this Chapter.

_424.7.2 ~lenderness effects shall be included according to requirements of Sections 410.10 through 410.13. In Equations (410-10) and (410-19) the term P, shall be replaced by 2.5 times the design axial load, and the factor 0.75 shall be taken equal to 1.0. 424.7.3-Walls shall be designed in accordance with Secti~n 414 of this Chapter with flexure and axial load capacities taken as 40 percent of that computed using Section 414. In Equation (414-1), $shall be taken equal to 1.0.

424.8 SHEAR AND TORSION

424.8.1 Design shear stress v shall be computed by

v

v=--

bw d

Eq. 11-1

'

where Vis design shear force at section considered. 424.8.2 When the reaction, in direction of applied shear, introduces compression into the end regions of a member, sections located less than a distance d from

face of support shall be permitted to be designed for the same shear as that computed.at a distance d. 424.8.3 Whenever applicable, effects of torsion, in accordance with provisions of Section 411 of this Chapter, shall be added. Shear and torsional moment

11

CHAPTER 11 -ALTERNATE DESIGN METHOD (WORKING STRENGTH)

strengths provided by concrete and limiting maximum strengths for tor1lon shall be taken as 55 percent of the values given in Section 411.

424.8.4 SHEAR STRESS CARRIED BY CONCRETE

424.8".4.1 For members subject to shear and flexure only, shear stress carried by concrete P, shall not exceed 0.09 .fj'; unless a more detailed calculation is made in accordance with Section 424.7.4.4. 424.8.4.2 For members subject to axial compression, shear stress carried by concrete Pr, shall not exceed 0.09 .fj'; unless a more detailed calculation is made in accordance with 424.7.4.5. 424.8.4.3 For members subject to significant axial tension, shear reinforcement shall be designed to carry total shear, unless a more detailed calculation is made using Vc

= 0.09(1 + 0.6NI Ag} .fj';

Eq. 11-2

where N is negative for tension. Quantity NI Ag shall be expressed in MPa. 424.8.4.4 For members subject to shear and flexure only, it shall be permitted to compute v .. by

v, = 0.85 .,j7'; + 0.9 p,.. Vdl M

Eq. 11-3

but Vc shall not exceed 0. 14 .,[f; . Quantity Vdl M shall not be taken greater than 1.0, where M is design moment occurring simultaneously with V at section considered. 424.8.4.5 For members subject to axial compression, it shall be permitted to compute Vc by .

v, = 0.09(1 + 0.09NI Ag) Quantity N I Ag shall be expressed in MPa.

ffc

Eq. 11-4

362

REINFORCED CONCRETE DESIGN

424.8.4.6 Shear stresses carried by concrete v, apply to normal weight concrete. When lightweight aggregate concrete is used, one of the following modifications shall apply:

1. When fit is specified and concrete is proportioned in accordance with Section 405.3,fir/6.7 shall be substituted for .jl'; but the value of fi,j 6.7 shall not exceed

.jl'; .

2. When fa is not specified, the value of ff: shall be multiplied by 0.75 for "all-lightweight" concrete and by 0.85 for "sand-lightweight" concrete. Linear interpolation shall be permitted when partial sand replacement is used, In determining shear stress carried by concrete v.., whenever applicable, effects of axial tension due to creep and shrinkage in restrained members shall be included and it shall be permitted to include effects of inclined flexural compression in variable-depth members.

~24.8.4.7

424.8.5 SHEAR STRESS CARRIED BY SHEAR REINFORCEMENT

424.8.5.1 Types of shear reinforcement

Shear reinforcement shall consist of one of the followin~ 1. Stirrups perpendicular to axis of member; 2. Welded wire fabric with wires located perpendicular to axis of member making an angle of 45 degrees or more with longitudinal tension reinforcement; 3. Longitudinal reinforcement with bent portion making an angle of 30 degrees or more with longitudinal tension reinforcement; 4. Combinations of stirrups and bent longitudinal reinforcement; 5. Spirals. 424.8.5.2 Design yield strength of shear reinforcement shall not exceed 415 MPa. 424.8.5.3 Stirrups and other bars or wires used as shear reinforcement shall extend to a distance d from extreme compression fiber and shall be anchored at both ends according, to Section 412.14 of this Chapter to' develop design yield strength of reinforcement.

CHAPTER 11 -ALTERNATE DESIGN METHOD (WORKING STRENGTH)

363

424.8.5.4 SPACING LIMITS FOR SHEAR REINFORCEMENT

424.8.5.4.1 Spacing of shear reinforcement placed perpendicular to axis of member shall not exceed d/2, nor 600 mm. 421.8.5.4.2 Inclined stirrups and bent longitudinal reinforcement shall be so spaced that every 45-degree line, extending toward the reaction from middepth of member (d/2) to longitudinal tension reinforcement, shall be crossed by at least one line of shear reinforcement. 424.8.5.4.3 When (v - v,) exceeds .

t ,[1';

maximum spacing given in

Sections 424.7.5.4.1 and 424.7.5.4.2 shall be reduced by one-half.

424.8.5.5 MINIMUM SHEAR REINFORCEMENT

424.8.5.5.1 A minimum area of shear reinforcement shall be provided in all reinforced concrete flexural members where design shear stress v is greater than one-half the permissible shear stress v, carried by concrete, except: 1. Slabs and footings; 2. Concrete joist construc.tion defined by Section 408.12 of this Chapter; 3. Beam with total depth .not greater than 250 mm, 2.5 times thickness of flange, or one-half the width of web, whichever is greatest. 424.8.5.5.2 Minimum shear reinforcement requirements of Section 424.8.5.5.1 shall be permitted to be waived if shown by test that required ultimate flexural and shear strength can be developed when shear reinforcement is omitted. 424.8.5.5.3 Where shear reinforcement is required by Section 424.8.5.5.1 or by analysis, minimum area of shear reinforcement shall be computed by Eq. 11-5

where bw and s are in rnm. 424.8.5.6 DESIGN OF SHEAR REINFORCEMENT 424.8.5.6.1 Where design shear stress v exceeds shear stress carried by concrete Vc, shear reinforcement shall be provided in accordance with Sections 424.8.5.6.2 through 424.8.5.6.8 ..

364

REINFORCED CONCRETE DESIGN

424.8.5.6.2 When shear reinforcement perpendicular to axis of member is used: Eg. 11-6

424.8.5.6.3 When inclined stirrups are used as shear reinforcement, Eg.2-1

424.8.5.6.4 When shear reinforcement consists of a single bar or a single group of parallel bus, all bent up at the same distance from the support, Eg. 2-2

where (v- Vr) shall not exceed

t..JJ: .

424.8.5.6.5 When shear reinforcement consists of a ~eries of parallel bentup bars or groups of parallel bent-up bars at different distances from the support, required area shall be computed by Eq. 2- 1 . 424.8.5.6.6 Only the center three-quarters of the inclined portion of any longitudinal bent bar shall be considered effective for shear reinforcement. 424.8.5.6.7 When more than one type of shear reinforcement is used to reinforce the same portion of a member, required area shall be computed as the sum of the various types separately. In such computations, Vc shall be included only once. 424.8.5.6.8 Value of (v -v,) shall not exceed

J..[j';.

424.8.6 SHEAR FRICTION Where it is appropriate to consider shear transfer across a given plane, such as an existing or potential crack, an interface between dissimilar materials, or an interface between two concretes cast at different times, shear-friction provisions of Section 411.8 of this Chapter shall be permitted to be applied, with limiting maximum stress for shear taken as 55 percent of that given in Section 411.8.5.

CHAPTER 11 -ALTERNATE DESIGN METHOD (WORKING STRENGTH)

365

Permissible stress in shear-friction reinforcement shall be that given in Section 424.4.2.

424.8.7 SPECIAL PROVISIONS FOR SLABS AND FOOTINGS

424.8.7.1 Shear capacity of slabs and footings in the vicinity of concentrated loads or reactions is governed by the more severe of two conditions: 424.8.7.1.1 Beam action for slab or footing, with a critical section extending in a plane across the entire width and located at a distance d from face of concentrated load or reaction area. For this condition, the slab or footing shall be designed in accordance with Sections 424.8.1 through 424.8.5. 424.8.7.1.2 Two-way action for slab or footing, with a critical section perpendicular to plane of slab and located so that . its perimeter · is a minimum, but need not approach closer than d/2 to perimeter of concentrated load, or reaction area. For this condition, the slab or footing shall be designed in accordance with Sections 424.8.7.2 and 424.8.7.3. 424.8.7.2 Design shear stress v shall be computed by Eq.2-3

where V and b., shall be taken at the critical section defined in Section 424.8.7.1.2. 424.8.7.3 Design shear stress v shall not exceed v, given by Eq. 2- 4 unless shear reinforcement is provided

Eq.2-4

but

Vc

shall not exceed

t

.[1: . Pc

is the ratio of lo~g side to short side of

concentrated load or reaction area. When lightweight aggregate concrete is · used, the modifications of Section 424.8.4.6 shall apply. 424.8.7.4 If shear reinforcement consisting of bars or wires is provided in accordance with Section 411.13.3 of this Chapter, and v shall not exceed 0.25 ..fj'; .

Vc

shall not exceed

-fz.{f;

366

REINFORCED CONCRETE DESIGN

424.8.7.5 If shear reinforcement consisting of steel 1- or channel-shaped sections (shearheads) is provided in accordance with Section 411.13.4 of this Chapter, von the critical section defined in Section 424 .8.7.1.2 shall not exceed 0.3

!J':

exceed

and v on the critical section defined in Section 411.13.4.7 shall not

t !J':.

In Equations (411-39} and, (411-40), design shear force V shall

be multiplied by 2 and substituted for V,.

424.8.8 SPECIAL PROVISIONS FOR OTHER MEMBERS

For design of deep flexural members, brackets and corbels, and walls, the special provisions of Section 411 of this Chapter shall be used, with shear strengths provided by concrete and limiting maximum strengths for shear taken .as 55 percent of the values given in Section 411 . ln Section 411 .11.6, the design a.cial load shall be multiplied by 1.2 if compression and 2.0 if tension, and substituted for N,. 424.8.9 COMPOSITE CONCRETE FLEXURAL MEMBERS

For design of composite c~ncrete flexural members, permissible horizontal shear stress v11 shall not exceed 55 percent of the horizontal shear strengths given in Section 417.6.2 of this Chapter.

317

CHAPTER 11 -ALTERNATE,OESJGN METHOD (WORKING STRENGTH)

DESIGN OF BEAMS FOR FLEXURE

fJE.. + fJE.

·b

TE'ir--c..,....

kd

_j_

d

jd

N.A. : ' '' '

n As

.,__ ---------- __ .,

T

To solve for c, take moment of area about N.A. Moment of area above N.A. = (n A,)(d- c) b cz = 2 11 A, d - 2 n A, c b cz + 2 11 A s c - 2 n A, d = 0

=

Moment of area below N.A.

(b)(c)(c/2)

5 c = ----'--'-----'-------

-2nA ±~~(2_n_A-~-)2---4-(-b)-(--2-n-A-,d-)

2(b)

c=

2 - 2nA + 8nA ;___ 5 + ~4nA, 5 bd _ _...:...___;_ ____ 2b

Eq. 2-5

jd

= d-

tkd

j=l.[M = C xjd] M = lf2({c,)(kd)(b)

X

tk

Eq. 2-6

jd M

= lf2/c j k bd2

Eq. 2-7

[M= Txjd] M=

A,fsjd

Eq. 2-8

368

REINFORCED CONCRETE DESIGN

BALANCED DESIGN

kd

d

jd

:;:::;:;:;::::::

.::::·::::::;.;:::;:::::::;:::;1;::::::

'

' •-------------

-·'

T

From the stain diagram (balanced condition) kd

-·- - =

d

lc IE, lc IE, +Is IE, k= lc IE, x ~c lc IE, + Is I Es E, k= lc lc + ls(E, IEs) But E.IEc = n Ec/Es = 1ln k=

lc = nl, fc + fs In nlc + Is

Eq. 2-9

CHAPTER 11 -ALTERNATE [)~SIGN METHOD (WORKING STRENGTH)

ILLUSTRATIVE PROBLEMS PROBLEM 11 - 1

A reinforced concrete beam having a width of 300 mm and an effective depth of 520 nun is reinforced for tension only with 5-28 mm bars. Concrete strength.fs = 128 MPa, [ c = 27 MPa, fc = 0.45 [on= 9. Use working strength design. Determine the following: a) The balance moment capacity of the beam. b) If the tension steel is 5-28 mm bars, determine the moment capacity of the beam.

SOLUTION

fi· = 0.45(27) = 12.15 MPa Part a: For balanced condition: k;,. __ 1-::--

1+_1~ II

fc

1 128 1+--9(12.15) k = 0.4607

j = 1- k/3 = 0.8464

j

M=%fcjkbd2 = 1/2(12.15)(0.8464)(0.4607)(300)(520)2 = 192.16 x 106 N-mm M = 192.16 kN-m Part b:

300 mm

300mm

T E

As = f (28) X 5 As = 3078.8 mm2 n As = 27,709 mm2 2

E :;;:: Lfl

1

N.A. ''

520- c

: nA, = 27,709

.1.

~ I-- •- - --- --- -- _ I

370

REINFORCED CONCRETE DESIGN

[l:ay

=

0] 300(c)(c/2) = 27709(520- c) 150 c2 + 27709 c- 14,408,680 = 0 c = 231.04mm

[c = kd] 231.04 = k(520) k = 0.444 j j

= 1 - k/3 = 0.852 = 85.2%

In terms of concrete, the resisting moment is: M = V2Jcj k b d2 = %(12.15)(0.852)(0.444)(300)(520)2 = 186.42 x 106 N-mm M = 186.42 kN-m In terms of steel: M = A,fsj d = 3078.8(128)(0.852)(520) = 174.6 x 106 N-mm M = 174.6 KN-m Thus, the moment capacity is 174.6 KN-m

PROBLEM 11 - 2 (CE NOVEMBER 1998)

In a reinforced concrete beam, b = 300 mm, d = 500 mm, As= 1500 mm2, 11 = 8. The beam is ·subjected to a bending moment of 70 kN-m. Use working strength design. Determine the following: a) The maximum stress in concrete. b) The maximum stress in steel.

371 .. ,

CHAPTER 11 -ALTERNATE DESIGN METHOD (WORKING STRENGTH)

SOLUTION b

Taking moment of area about N.A. 12000(500- kd)- 300(kd)(kdj2) ~ 0 (kd)2 + 80(kd) - 40000 = 0 kd = 164 mm

k = 164/500 k = 0.328 j = 1- k/3 j = 0.891

= 300

500 500- kd . : ':::!:

[M =- lf2 j k{r b d2] 70 X 106 =' 1/2(0.891)(0.328)({c)(300)(500)2

nA. = 8(1500) nA. = 12,000 mm2

fi = 6.39 MPa [M =As f.

X

jd]

70 X 106 =' 1500 j. (0.891)(500) j.

= 104.75 MPa

PROBLEM 11 - 3

A reinforced concrete tee-beam has the dimensions shown in the Figure. A moment of 112 kN-m acts on the section. It is required that the neutral axis is to be at section X-X. Use Es/ E, = 10. Determine a) the required steel, b) the stress in concrete and c) the stress in steel. 600mm

X

E E ~

"'

100 mm

225 mm

372

REINFORCED CONCRETE DESIGN

SOLUTION w = }'cone x Area of cross-section

w = 23.5[0.6(0.15) + 0.225(0.5 + 0.1)]

=5.29 kN/m fc

600mm

N.A.

~

§

8

1/')

lOOmm

E E

225mm

a) Part a Taking moment of area about N.A.: 10 As (500) = 600(150)(150/2) As=1350mm2 b) Part b [M = C(600)] 112 X 106 = [¥2/c (150)(600)](600) /c = 4.148 MPa b) Parte [T=q . As/s =112/c 150 (600) 1350 f.= 1/2 (4.148)(150)(600) f. =138.27 MPa

Another Solution: With N.A. along a-a, kd =150 mm k(650) =150 k =0.231 j=1-k/3 = 1-0.231/3 j= 0.923

373

CHAPTER 11 -ALTERNATE DESIGN METHOD (WORKING STRENGTH)

[M = %fcj k bd2] 112 X 106 = lf2 /r (0.923)(0.231 )(600)(650)2 fi =4.144 MPa

[M =As.fsj d] .

112 X 106 = 1350 Is (0.923)(650) /s = 138.28 MPa .

PROBLEM 11 - 4

The T-beam shown in the Figure is reinforced with 1,613 sq. mm. of steel. Assume n = 12, /c :S 4,14 MPa, .fs :S 124 MPa. Determine the following: a) The distance of the neutral axis from the top of the flange. b) The moment of inertia about N.A. of the transformed section. c) The moment capacity of the section. 750mm

400 mm

SOLUTION 750mm

100

}

___

N.A.

SOOmm

(](V) r_r.-~) +-( x-J~ )(_Jfb){!

,db

=:: ~19 ;

'

'

3SW( (idb-

:I:::

n As= 19356

'!5D60 X- 37SV d7fb .

I

f (x-tm/'(J7r) Taking moment of area about N.A. 750(100)(50 + x) + 400(x)(x/2) =19356(500- x) 3750000 + 75000 X+ 200 X2 = 9678000-19356 X x2 + 471.78 x- 29640 = 0

;(2;. /<(t

,;~-~. ~

~ ~ ~ +I~ __.--

7..mz; K- ~ 7ftl (Jff4 + 3U {"' 7S-PI..f,

=

-

i II

(Q f 'J I ~ 6'b -\

10

REINFORCED CONCRETE DESIGN

374

x=56.14mm

y = 100 +X y = 156.14 mm/ I= 750(100)3 + (750)(100)(50 + 56.14)2 + 400(56.14)3 12 3 + 19356(500- 56.14)2 = 4744.4 x 106 mm4 I = 0.00474 m4 In terms of permissible concrete stress:

[fr = M~]

I . = M(156.14) 4 14 4744.4x10 6 M = 125.8 x 106 N-mm M = 125.8 kN-m

In terms of permissible steel stress:

[ fs n

= Me] I 124 _ M(500- 56.14) 12 - 4744.4 X 10 6 M = 110.45 x 106 N-mm M = 110.45 kN-m

.

Thus, the maximum moment the T-beam can carry is 110-.45 kN-m

375

ANSWERS TO SUPPLEMENTARY PROBLEMS

•

Problem 2.23: As= 1054mm2 Problem 2.24:

b=250mm d=435mm As =3280mm2

Problem 2.25: As=5549mm2 Problem 2.26: Mu=36lkN-m Problem 2.27: M,.=3WkN-m Problem 2.28: M, ... 355kN-m

11::

Problem 3.13: As= 3900mm2 Problem 3.14: As = 7,865 mm2 Problem 3.15: M,.=420kN"m Problem 3.16: Mu=900kN-m Problem 3.17: As "" 4,373 mm2 A's7905 mm2 Problem 3.18: As= 5,971 mm2 A's = 1,925 mm2 Problem 3.19: M,.=634kN-m Problem 3.20: Mu = 1,139 kN-m

376

ANSWERS TO SUPPLEMENTARY PROBLEMS

Problem 4.8:

5 ""

60 mm

Problem 4.9:

5=

95 mm

Problem 4.10: a) stirrup is not needed b) 5 = 255 mm c) s = 120mm d) section is inadequate Problem 4.11: One set of spacing: · 1 @40mm, 12@ 80mm, 5@ 100mm, 4@ 150 mm and 2@300mm

Problem 5.9:

ldb = 652mm

Problem 5.10: ldb .. 621 mm Problem 5.11: ldb = 364 inm Problem 5.12: ldb=414 mm Problem 5.13: Ld•1147mm Problem 5.14: Ld=2894mm

ii;

,.,

. __ ft

"'

.

..~

Problem 6.10: P,.= 2,510kN Problem 6.11: Column size: 415 mm x 415 mm 6-28mm bars Tie spacing: 415 mm Problem 6.12: Column size: 355 mm x 355 mm 10 - 28 mm bars Tie spacing: 355 mm Problem 6.13:

P,. .. 3,790kN

Problem 6.14: Column diameter: 490 mm 7- 28mm bars Spiral pitch: 53 mm }>roblem 6.15: Column diameter: 435 mm 15 - 25 mm bars Spiral pitch: 75 mm

.......

-'

'

.

'

.

ANSWERS TO SUPPLEMENTARY PROBLEMS

Problem 7.11:

P, =4,320kN

Problem 7.12: P, =3,340kN Problem 7.13: P,= 1,520kN Problem 7.14: P,=2,350kN Problem 7.15: eb=403 mm Pbn =1720kN Problem 7.16:

P, =4,920kN

Problem 7.17: · P, = 2,820 kN Problem 7.18: P, = 890 kN Pbn = 1490 kN (eb • 367 mm) Probl~m

7.19: P, = 2,100 kN

Problem 7.20: 8 - 28 mm bars

Problem 8.7:

Me = 751 kN-m

Problem 8.8:

Yes; P, = 1200 kN

The following are one of the answers of each problem: Problem 9.11: Size of footing: 2.8 m x 2.8 m d=350mm Reinforcement: 14-20 mm both ways Problem 9.12: Footing size: 2m x 3.9 m d=420mm Reinforcement: Along long side: 10 - 20 mm Along short side: 13 - 20 mm 9 across center band & 2 in each outer bands Problem 9.13: Footing size: 1.5 m x 2.4 m d=370mm Center of column • 340 mm from center of footing (measured along the length) Bars along length: 10- 20 mm Bars along wiath: 11 - 20 mm

377

378

ANSWERS TO SUPPLEMENTARY PROBLEMS

Problem 9.14: Footing width= 3.5 m d=325mm Main bars (along width): 20 mm@ 120 mm o.c. Problem 9.15:

B = 2.68m L = 5.21 m

d=460mm Longitudinal Bars: Face of column 1: 13- 25 nun (top bars, entire width) In between columns: 26 - 25 mm (top bars, entire length) Face of column 2: 13 - 25 mm (top bars, entire length) Face of column 2: 13 - 25 mm (bottom bars, L = 2m) Transverse Bars: Column 1:3-25 mm within 645 mm (bottom bars) Column 2:4- 25 mm within 745 mm (bottom bars) Problem 9.16:

a= 2.02m b= 3.93 m d=435mm Longitudinal bars (top bars): Face of Column 1: 12- 20 mm Face of column 2: 20- 20 mm Middle of footing: 24 - 20 mm

GLOSSARY OF CIVIL ENGINEERING TERMS

.Glossary of Civil Engineering Terms const- Constntttion and engineering terms [l11id - Fluid mechanics gen - General engineering terms soil - Geotechnical water- Water supply, wastewater, sewerage, hydrology, and other related topics

A A A 5 H T 0 (const) -American Association of State Highway mid Transportation Officials AS T M (const) -American Society for Testing and Materials A W G (const)- American Wire Gage Abnormal Failure (const)- Artificially induced malfunction/ failure of a component Abrasion (const) - Wear or removal of the surface of a solid material as a result of relative movement of other solid bodies in contact with it. Abrasion resistance (const) - Ability of a construction element to resist mechruucal abrasion such as foot traffic and wind blown particles which tend to progressively remove materials from exposed surfaces such as roofing the membranes Absolute Pressure (gen) - Gage pressure plus atmospheric pressure Absolute Pressure Transducer (gen) - A transducer that has an internal reference chamber sealed at or close to 0 psia (full vacuum) and normally provides increasing output voltage for increases in pressure Absorpotion (soU) - The taking in or soaking up of one substance into the body of another by molecular or chemical action (as tree roots absorb dissolved nutrients in the soil) . Absorption Capacity (soil) - The amount of liquid which a solid material can absorb. Sand, as an example, can hold approximately one-third of its volume in water, or three cubic feet of dry sand can contain one cubic foot of water. A denser soil, such as clay, can hold much less water and thus has a lower absorption capacity. Absorption Rate (soil) -The speed at which a measured amount of solid material can absorb a measured amount of liquid. Under pressure, water can infiltrate a given volume of gravel very rapidly. The water will penetrate (or be absorbed by) sand more slowly and will take even longer to saturate the same amount of clay. Acceleration (gen) -The first derivative of velocity with respect to time. Units expressed in "g" Accelerometer (gen) - A transducer which converts mechaiLical motion into an electrical signal that is proportional to the acceleration value of the motion; it measures acceleration or gravitational force capable of imparting acceleration Accuracy (gen)- The combined error of nonlinearity, repeatability, and hysteresis expressed as a pen;ent of full scale output

G-2

GLOSSARY OF CIVIL ENGINEERING TERMS

Accuracy vs. Precision (gen) - If the actual value is 5.321 and you say that it is 5.30, then you are precise to 3 places but inaccurate by .021 ; If a value is represented as a bullseye on a target, a group of guesses or measurements represented by closely grouped points have a high degree of precision. If that group is near the center, it is highly accurate as well. On a bullseye, think of accuracy as how close to the center your arrow hits, · and your measurement of precision as how closely you can gr.oup your shots Acid (gen)- A substance that tends to lose a proton. 0 A substance that dissolves in water with the formation of hydrogen ions. 3) A substance containing hydrogen which may be replaced by metals to form salts. 4) A substance that is corrosive. · Acid Rain (water) -Precipitation which has been rendered (made) acidic by ai~bome pollutants. Acid Regression Stage (water) - A time period when the production of volatile acids is reduced during anaerobic digestion. During this stage of digestion ammonia compounds form and cause the pH to increase. Acidic (water) - The condition of water or soil which contains a sufficient amount of acid substances to lower the pH below 7.0. Acidified (water)- The addition of an acid (usually nitric or sulfuric) to a sample to lower the pH below 2.0. The purpose of acidification is to "fix" a sample so it won't change until it is analyzed. · . Acidity (water) -The capacity of water or wastewater to neutralize bases. Acidity is expressed in milligrams per liter of equivalent calcium carbonate. Acidity is not the same as pH because water does not have to be strongly acidic (low pH) to have a high acidity. Acidity is a measure of how much base must be added to a liquid to raise the pH to 8.2. Acrylic resin (const) - One of a group of thermoplastic resins formed by polymerization of esters or amides of acrylic acid; used in concrete or masonry"construction as a bonding agent or surface sealer. Activated Carbon (water) - Adsorptive particles or granules of carbon usually obtained by heating carbon (such as wood) . These particles or granules have a high capacity to selectively remove certain trace and soluble materials from water. Activated Sludge (water) - Sludge particles produced in raw· or settled wastewater (primary effluent) by the growth of organisms (including zoogleal bacteria) in aeration tanks in the presence of dissolved oxygen. The term "activated" comes from the fact that the particles are teeming with bacteria, fungi, and protozoa. Activated sludge is different from primary sludge in that the sludge particles contain many living organisms which can feed on the incoming wastewater. Activated Sludge Process (water)- A biological wastewater treatment process which speeds up the decomposition of wastes in the wastewater being treated. Activated sludge is added to wastewater and the mixture (mixed liquor) is aerated and agitated. After some time in the aeration tank, the activated sludge is allowed to settle out by sedimentation and is disposed of (wasted) or reused (returned to the aeration tank) as needed. The remaining wastewater then undergoes more treatment. Adhesion (gen) -The force that resists the separation of two bodies in contact. Admixture.(const)- A material,.other than aggregate, cementitious material or water, added in small quantities to the mix in order to produce some (desired) modifications, either to the properties of the mix or of the hardened product.

GLOSSARY OF CIVIL ENGINEERING TERMS

G-3

Admixture (const) - Material other than water, aggregate, or hydraulic cement, used as in ingredient of concrete and added to concrete before or during its mixing to modify its properties. Adsorbate (water)- Th~ material being removed by the adsorption process. ·Adsorbent (water) - The material (activated carbon) that is responsible for removing the uhdesirable substance in the adsorption process. Adsorption (water) -The gathering of a gas, liquid, or dissolved substance on the surface or interface zone of another material. Advanced Waste Treatment (water) - Any process of water renovation that upgrades treated wastewater to meet specific reuse requirements. May include general cleanup of water or removal of specific parts of wastes insufficiently removed by conventional treatment processes. Typical processes include chemical treatment and pressure filtration. Also called TERTIARY TREATMENT. Aeration (water) - The process of adding air to water. Air can be added to water by either passing air through water or passing water through air. In wastewater treatment, air is added to freshen wastewater and to keep solids in suspension. With mixtures of wastewater and activated sludge, adding air provides mixing and oxygen for the microorganisms treating the wastewater. Aeration Liquor (water) - Mixed liquor. The contents of the aeration tank including living organisms and material carried into the tank by either untreated wastewater or primary effluent. Aeration Tank (water) -The tank where raw or settled wastewater is mixed with return sludge and aerated. The same as aeration bay, aerator, or reactor. Aerobes (water) - Bacteria that must have molecular (dissolved) oxygen (DO) to survive. Aerobes are aerobic bacteria. Aerobic (water) - A condition in which atmospheric or dissolved molecular oxygen is present in the aquatic (water) environment. Aerobic Bacteria (water) - Bacteria which will live and reproduce only m an environment containing oxygen which is available for their respiration (breathmg), namely atmospheric oxygen or oxygen dissolved in water. Oxygen combined chemically, such as in water molecules (H20), cannot be used for respiration by aerobic bacteria. Aerobic Decomposition (water) - The decay or breaking down of organic material in the presence of "free" or dissolved oxygen. Aerobic Digestion (water) - The breakdown of wastes by microorganisms in the presence of dissolved oxygen. This digestion process may be used to treat only waste activated sludge, or trickling filter sludge and primary (raw) sludge, or waste sludge from activated sludge treatment plants designed without primary settling. The sludge to be treated is placed in a large aerated tank where aer6bic microorganisms decompose the organic matter in the sludge. This is an extension of the activated sludge process. Aerobic Process (water)- A waste treatrrient process conducted under aerobic (in the presence of "free" or dissolved oxygen) conditions. Age Tank (water) - A tank used to store a known concentration of chemical solution for feed to a chemical feeder. Also called a DAY TANK Agglomeration (water) -The growing or coming together of small scattered particles into larger floes or particles which settle rapidly. Also see FLOC.

G-4

GLOSSARY OF CIVIL ENGINEERING TERMS

Aggregate (const) - Granular materials, such as sand, gravel, crushed stone, and iron blastfurnace slag, used with a cementing medium to form a hydraulic cement concrete or mortar. Aggregate lightweight (const)- Aggregate with a dry, loose weight Qf 1100 kg/ m3 or less. Agronomic Rates (water) - Sludge application rates which provide the amount of nitrogen needed by the crop or vegetation grown on the land while minimizing the amount that passes below the root zone. Air Binding (water) -The clogging of a filter, pipe or pump due to the presence of air released from water. Air entering the filter media is harmful to both the filtration and backwash processes. Air can prevent the passage of water during the filtration process and can cause the loss of filter media during the backwash process. Air Gap (water) - An open vertical drop, or vertical empty space, that separates a drinking (potable) water supply to be protected from another water system in a water treatinent plant or other location. This open gap prevents the contamination of drinking water by backsiphonage or backflow because there is no way raw water or any other water can • reach the drinking water. Air Lift (water) - A special type of pump. This device consists of a vertio:al riser pipe submerged in the wastewater or sludge to be pumped. Compressed air is injected into a tail piece at the bottom of the pipe. Fine air bubbles mix with the wastewater or sludge to form a mixture lighter than the surrounding water which causes the mixture to rise in the discharge pipe to the outlet. An airlift pump works like the center stand in a percolator coffee_pot. Air Padding (water) - Pumping dry air (dew point -40°F) into a container to assist with the withdrawal of a liquid or to force a liquified gas such as chlorine. out of a container. Air Relief (water) - A type of valve used to allow air caught in high spots in pipes to escape. Air Stripping (water) - A treatinent process used to remove dissolved gases and volatile substances from water. Large volumes of air are bubbled through the water being treated to remove (strip out) the dissolved gases and volatile substances. Air Test (water) -A method of inspecting a sewer pipe for leaks. Inflatable or similar plugs are ph1ced in the line and the space between these plugs is pressurized with air. A drop in pressure indicates the line or run being tested has leaks. Algae (water}- Microscopic plants which contain chlorophyll and live floating or suspended in water. They also may be attached to structures, rocks or other submerged surfaces. Excess algal growths can impart tastes and odors to potable water. Algae produce oxygen during sunlight hours and use. oxygen during the night hours. Their biological activities appreciably affect the pH, alkalinity, and dissolved oxygen of the water. Algal Bloom (water) - Sudden, massive growths of microscopic and macroscopic plant life, such as green or bluegreen algae, which develop in lakes and reservoirs. Algicide (water) - Any substance or chemical specifically formulated to kill or control algae. Aliphatic Hydroxy Acids (water)- Organic acids with carbon atoms arranged in branched or unbranched open chains rather than in rings. Alkali (watet) - Any of certain soluble salts, principally of sodium, potassium, magnesium, and calcium, that have the property of combining with acids to form neutral salts and may be used in chemical water. treatinent processes.

I

GLOSSARY OF CIVIL ENGINEERING TERMS

G• 5

Alkaline (water) - The condition of water or soil which contains a sufficient amount of alkali substances to raise the pH above 7.0. Alkalinity (water) - The capacity of water to neutralize acids. This capacity is caused by the water's content of carbonate, bicarbonate, hydroxide, and occasionally borate, silicate, and phosphate. Alkalinity is expressed in milligrams per liter of equivalent calcium carbonate. Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have a high alkalinity. Alkalinity is a measure of how much acid must be added to a liquid to lower the pH to 4.5. Alluvial (water) - Relating to mud and/ or sand deposited by flowing water. Alluvial deposits may occur after a heavy rainstorm. Alluvial Deposit (water)- Sediment (clay, silt, sand, gravel) deposited in place by the action of running water. Altitude Valve (water) - A valve that automatically shuts off the flow into an elevated tank when the water level in the tank reaches a predetermined level. The valve automatically opens when the pressure in the distribution system drops below the pressure in the tank. Aluminum (gen) - symbol AI, most abundant metallic element in the earth's crust. The atomic number of aluminum is B; the atomic weight is 26.9815. Aluminum is a lightweight, silvery metal. In contact with air, aluminum rapidly becomes covered with a tough, transparent layer of aluminum oxide that resists corrosion. Aluminum is neverfound as alone but commonly occurs as aluminum silicate or as a silicate of aluminum mixed with other metals. Expensive to refine, these silicates are not useful ores. Bauxite, an impure hydrated aluminum oxide, is the commercial source of aluminum and its compounds. A low-cost technique dating from the 1880s is still the major method of production. Aluminum weighs less than one-thin\ as much as steel. Its high strength-to-weight ratio makes aluminum useful in many applications · Ambient (water)- Surrounding. Ambient or surrounding atmosphere. Ambient Con1pensation (canst) - The design of an insh·ument such that changes in ambient temperature do not affect the reading~ of the instrument Ambient C<'llditions (gen) -Conditions around a transducer (pressure, temperature, etc.) Ambient Temperature (water) - Temperature of the surrounding air (or other medium). For example, temperature of the room where a gas chlorinator is installed. Anaerob~s

(water)- Bacteria that do not need molecular (dissolved) oxygen (DO) to survive.

Anaerobic (water) - A condition in whicl1 ahnosphcric or dissolved molecular oxygen is NOT present in the aquatic (water) environment. AnaProbic Bacteria (water) - Bacteria that live and reproduce in an environment containing no "free" or dissolved oxygen. Anaerobic bacteria obtain their oxygen supply by . breaking down chemical compounds which contain oxygen, such as sulfate (5042-). Anaerobic Decomposition (water) - The decay or breaking down of organic material in an environment containing no "free" or dissolved oxygen. Anaerobic Digester (water) - A wastewater solids treatment device in which the solids and water (about 5 percent solids, 95 percent water) are placed in a large tank where bacteria decompose the solids in the absence of dissolved oxygen. Anaerobic Digestion (water) - Wastewater solids and water (about 5% solids, 95% water) are-placed in a large tank where bacteria decompose the solids in. the absence of dissolved oxygen. At least two general groups of bacteria act in balance: (1) SAPROPHYTIC bacteria

G-6

GLOSSARY OF CIVIL ENGINEERING TERMS

break down complex solids to volatile acids, the most common of which are acetic and propionic acids; and (2) METHANE FERMENTERS break down the acids to methane, carbon dioxide, and water. Anaerobic Selector (water) - Anaerobic refers to the practical absence of dissolved and chemically bound oxygen. Selector refers to a reactor or basin and environmental conditions (food, lack of DO) intended to favor the growtP of certain organisms over others. Also see SELECTOR. Anchor (const) - Device providing a fixing to a solid surface Anchorage (const) - In post-tensioning, a device used to anchor tendon to concrete member, in pretensioning, a device used to anchor tendon during hardening of concrete. Anemometer (gen) - Instrument for measuring and/ or indicating the velocity of air flow Angle of Repose (gen) - The angle between a horizontal line and the slope or surface of unsupported material such as gravel, sand, or loose S
GLOSSARY OF CIVIL ENGINEERING TERMS

G-7

It is used in roofing materials, surfacing roads, in lining the walls of water-retaining

structures such as reservoirs and swimming pools, and in manufacturing floor tiles. Asphalt should not be confused with tar, a similar looking substance made from coal or wood and incompatible with petroleum derivates Aspirate (water)- Use of a hydraulic device (aspirator or eductor) to create a negative pressure (srn:tion) by forcing a liquid through a restriction, such as a Venturi. An aspirator (the hydraulic device) may be used in the laboratory in place of a vacuum pump; sometimes used instead of a sump pump. Attached Growth· Processes (water) - Wastewater tr,eatment processes in which the microorganisms and bacteria treating the wastes are attached to the media in the reactor. The wastes being treated flow over the media. Trickling filters and rotating biological contactors are attached growth reactors. These reactors can be used for BOD removal, nitrification and denitrification. Autotrophic (water) - Describes organisms (plants and some bacteria) that use inorganic materials for energy and growth. Average Demand (wate1)- The total demand for water during a period of time divided by the number of days in that time period. This is also called the average daily demand. Axial Load (const)- Load applied along or parallel to and concentric with the primary axis

B B 0 D (water) - Biochemical Oxygen Demand. The rate at which organisms use the oxygen in water while stabilizing decomposable organic matter under aerobic conditions. In decomposition, organic matter serves as food for the bacteria and energy results from its oxidation. BOD measurements are used as a measure of the organic strength of wastes in water. B 0 D 5 (water) - BODS refers to the five day biochemical oxygen demand. The total amount of oxygen used by microorganisms decomposing organic matter increases each day until the ultimate BOD is reached, usually in 50 to 70 days. BOD usually refers to the five-day BOD or BODS. B T U (gen)- British thermal units; the quantity of thermal energy required to raise one pound of water at its maximum density, 1 degree F. One BTU is equivalent to .293 watt hours, or 252 calories. One kilowatt hour is equivalent to 3412 BTU Back Pressure (water) - A pressure that can cause water to backflow into the water supply when a user's water system is at a higher pressure than the public water system. Backfill (soil) - Material used to fill in a trench or excavation. D The act of filling a trench or excavation, usually after a pipe or some type of structure has been placed in the trench or excavation. Backfill Compaction (soil) - Tamping, rolling or otherwise mechanically compressing material used as backfill for a trench or excavation. Backfill is compressed to increase its density so · that it will support the weight of machinery or other loads after the material is in place in the excavation. D Compaction of a backfill material can be expressed as a percentage of the maximum compactability, density or load capacity of the material being used.

G·B

GLOSSARY OF CIVIL ENGINEERING TERMS

Backflow (water) - A reverse flow condition, created by a difference in water pressures, which causes water to flow back into the distribution pipes of a potable water supply from any source or sources other than an intended source. Also see BACKSIPHONAGE. Backflusing (water) - A procedure used to wash settled waste matter off upstream structures to prevent odors from developing after a main line stoppage has been cleared. Backsiphonage (water) - A form of backflow caused by a negative or below atmospheric pressure within a water system. Also see BACKFLOW. Backwashing (water) -The process of reversing the flow of water back tlvough the filter media ' to remove the entrapped solids. '

Backwater Gate (water) - A gate installed at the end of a drain or outlet pipe to prevent the backward flow of water or wastewater. Generally used on storm sewer outlets into streams to prevent backward flow during times of flood or high tide. Also called a TIDE GAT~.

Bacteria (water) - Bacteria are living organisms, microscopic in size, which usually consist of a single cell. Most bacteria use organic matter for their food and produce waste products as a result of their life processes. Baffle (water) - A flat board or plate, deflector, guide or similar device constructed or placed in flowing water or slurry systems to cause more uniform flow velocities, to absorb energy, and to divert, guide, or agitate liquids (water, chemical solutions, slurry). Baffle (water) - A flat board oi plate, deflector, guide or similar device constructed or placed in flowing water, wastewater, or slurry systems to cause more uniform flow velocities, to absorb energy, and to divert, guide, or agitate liquids (water, chemical solutions, slurry). Ballirig (water) - A method of hydraulically cleaning a sewer or. storm drain by using the pressure of a water head to crea~ a high cleansing velocity of water around the ball. In :normal operation, the ball is restrained lly a cable while water washes past the ball at high velocity. Special sewer cleaning balls have an outside tread that causes them to spin or rotate, resulting in a "scrubbing" action of the flowing water along the pipe wall. Baluster (const)- Vertical member supporting the railing. Balustrade (const) -A railing composed of balusters capped by a handrail. Batch Process (water) - A treatment process in which a tank or reactor is filled, the water is treated-or a chemical solution is prepared, and the tank is emptied. The tank may then be filled.and the process repeated. Bearing (const) - The linear or a real dimension over which a higher component transmits load to a lower component Bearing Wall (const) -A wall that supports any vertical load in addition to its own weight. Bedding (const) - A layer, usually of concrete or mortar, for providing continuous support to such items as bricks, slabs, pipes. 0 The prepared base or bottom of a trench or excavation on which a pipe or other underground structure is supported. Bell (water) - In pipe fitting, the enlarged female end of a pipe into which the male end fits. Also called a HUB. Bellmouth (water) - An expanding, rounded entrance to a pipe or orifice. Biodegradable (water) - Organic matter that can be broken down by bacteria to more stable forms which will not create a nuisance or give off foul odors is considered biodegradable.

GLOSSARY OF CIVIL ENGINEERING TERMS

Biodegration (water) -The breakdown of organic matter by bacteria to more stable forms which will not create a nuisance or give off foul odors. Bioflocculation (water) - The clumping together of fine, dispersed organic particles by the action of certain bacteria and algae. This results in faster and more complete settling of the organic solids in wastewater. Biological Growth (water) -The activity and growth of any and all living organisms. Biological Process (water) - A waste treatment process by which bacteria and other microorganisms break down complex organic materials into simple, nontoxic, more stable substances. Biomass (water) - A mass or clump of organic material consisting of living organisms feeding on the wastes in wastewater, dead organisms and other debris. Also see ZOOGLEAL FILM. Biosolids (water) - A primarily organic solid product, produced by wastewater treatment processes, that can be beneficially recycled. The word biosolids is replacing the word sludge. Biosurvey (water) - A survey of the types and numbers of organisms naturally present in the receiving waters upstream and downstream from plant effluents. Comparisons are made between the aquatic organisms upstream and those organisms downstream of the discharge. Bleeding (const)- The separation of water from an unhardened mix. P: The process of diffusion of a soluble colored substance from, into, and through a paint or varnish coating from beneath, thus producing an undesirable staining or discoloration. Used similarly to refer to the transfer of soluble material from bitumen impregnated roofing materials, in limerich water, causing staining of soffits of concrete slab roofs Blind Stop (const) - A thin sheet of wood machined to fit the exterior vertical edge of the pulley stile or jamb and keep the sash in place. Blister (const) - A local separation of a surface layer causing a raised area on the surface with a cavity below, usually happening in flat roofs Bond (const)- Adherence between materials such as bricks/mortar, or plies of felt, or between felts and other elements of roof systems, which use bitumen or other materials as the cementing agent Bonded tendon (const) - Prestressing tendon that is bonded to concrete either directly or through grouting. Bonder (const) - (See Header) Brick (const) - A rectangular masonry building unit, not less than 75% solid, made from burned clay, shale, or a mixture of these materials. Buildability (const) - The extent ·to which the design of a building facilitates ease of· construction, subject to the overall requirements for the com~leted building. Building Control (const) - (on site) Responsibility of government or government agency or designated professional, who by periodic checking ensures that work on site is in accordance with approved construction plans and regulations. Building Services Design - Design. of the building services elements within a construction. Normally specialist building services engineers will be responsible for this work on large projects. On smaller projects may fall within the responsibility of the architect.

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GLOSSARY OF CIVIL ENGINEERING TERMS

Buttress (const) -A bonded masonry column built as an integral part of the wall and decreasing in thickness from bottom to top, although never thinner than the wall. It is used to provide lateral stability to the wall.

c C Factor (water) - A factor or value used to indicate the smoothness of the interior of a pipe. The higher the C Factor, the smoother the pipe, the greater the carrying capacity, and the smaller the friction or energy losses from water flowing in the pipe. To calculate the C Factor, measure the flow, pipe diameter, distance between two pressure gages, and the friction or energy loss of the water between the gages. C 0 D (water) - Chemical Oxygen Demand. A measure of the oxygen-consuming capacity of organic matter present in wastewater. COD is expressed as the amount of oxygen consumed from a chemical oxidant in mg/L during a specific test. ResUlts are not necessarily related to the biochemical oxygen demand (BOD) because the chemical • oxidant may react with substances that bacteria do not stabilize. C S 0 (water) - Combined Sewer Overflow. Wastewater that flows out of a sewer (or lift station) as a result of flows exceeding the hydraulic capacity of the sewer. CSOs usually occur during periods of heavy precipitation or high levels of runoff from snow melt or other runoff sources. Caisson (water) - A structure or chamber which is usually sunk or lowered by digging from the inside. Used to gain access to the bottom of a stream or other body of water. Calcium Carbonate Equilibrium (water) - A water is considered stable when it is just saturated with calcium carbonate. In this condition the water will neither dissolve nor deposit calcium carbonate. Thus, in this water the calcium carbonate is in equilibrium with the hydrogen ion concentration. Calcium Carbonate Equivalent (water) - An expression of the concentration of specified constituents in water in terms of their equivalent value to calcium carbonate. For example, the hardness in water which is caused by calcium, magnesium and other ions is usually described as calcium carbonate equivalent. Alkalinity test results are usually reported as mg/L CaC03 equivalents. To convert chloride to CaC03 equivalents, multiply the concentration of chloride ions in mg/L by 1.41, and fur sulfate, multiply by 1.04. Calibration (gen) - A procedure which checks or adjusts an instrument's accuracy by comparison with a standard or reference. Calorie (water) - The amount 0f heat required to raise the temperature of one gram of water one degree Celsius. Capillarity (fluid) - Absorption of a liquid due to surface tension _ "rising damp" in walls is caused by capillary rise of the water in small pores of the walling materials Capillary Action (water) - The movement of water through very small spaces due to molecular forces. Capillary Effect (water) -Also called "wicking e.ffect." The ability of a liquid to rise above an established level to saturate a porous solid. Capillary Forces (water) - The molecular forces which cause the movement of water through very small spaces.

GLOSSARY OF CIVIL ENGINEERING TERMS

G ·11

Capillary Fringe (water) - The porous ma~rial just above the water table which may hold water by capillarity (a property of surface tension that draws water upward) in the smaller void spaces. Carbonaceous Stage (water) - A stage of decomposition that occurs in biological treatment processes when aerobic bacteria, using dissolved oxygen, change carbon compounds to carbon dioxide. Sometimes referred to as "first stage BOD" because the microorganisms attack organic or . carbon compounds first and · nitrogen compounds later. Also see NITRIFICATION STAGE. Carbonation (gen)- The .transformation of the free alkali and alkali-earth hydroxides existent in the cement matrix into carbonates, due to a reaction with carbon dioxide available l.n the atmosphere. Carcinogen (water) - Any substance which tends to produce cancer in an organism Qrriage (canst) - Rough timber supporting the steps of wood stairs. Catalyst (water) - A substance that changes the speed or yield of a chemical reaction without being consumed or chemically changed by the chemical reaction. Catalyze (water) -To act as a catalyst. Or, to speed up a chemical reaction. Catch Basin (water) - A chamber or well used with storm or combined sewers as a means of removing grit which might otherwise enter and be deposited in sewers. Also see STORM WATER INLET and CURB INLET. Cathode (water) - The negative pole or electrode of an electrolytic cell or system. The cathode attracts positively charged particles or ions (cations). Cathodic Protection (water) - An electrical system for prevention of rust, corrosion,. and pitting of metal surfaces which are in contact with water or soil. A low voltage current is made to flow through a liquid (water) or a soil in contact with the metal in such a manner that the external electromotive force renders the metal structure cathodic. This concentrates corrosion on auxiliary anodic parts which are deliberately allowed to corrode instead of letting the structure corrode. Cation (water) - A positively charged ion in an electrolyte solutioh, attracted to the cathode under the influence of a difference in electrical potential Sodium ion (Na+) is a cation. Cation Exchange Capacity (water) - The ability of a soil or other solid to exchange cations (positive ions such as calcium, Ca2+) with a liquid. Cationic Polymer (water) - A polymer having positively charged groups of ions; often used as a coagulant aid. Caulk (water) - To stop up and make watertight the joints of a pipe by filling the joints with a waterproof compound or material. · Caulking (water) - A waterproof compound or material used to fill a pipe joint. 0 The act of using a waterproof compound or material to fill a pipe joint. Cavitation (water) - The formation and collapse of a gas pocket or bubble on the blade of an impeller or the gate of a valve. The collapse of this gas pocket or bubble drives water into the impeller or gate with a terrific force that can cause pitting on the impeller or gate surface. Cavitation is accompanied by loud noises that sound like someone is pounding · on the impeller or gate with a hammer. Cavity .Wall (canst) - (See Hallow Wall)

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GLOSSARY OF CIVIL ENGINEERING TERMS

Cell Test (const) - Cells of 500 feet length are constructed for vanous combinations of bituminous, concrete and aggregate. They repre5ent a wide range of pavement types with varying combinations of surface, base, subbase, drainage and compaction Cementation (water) • A spontaneous electrochemical process that involves the reduction of a more electropositive (noble) species, for .example, copper, silver, mercury, or cadmillill,. by electronegative (sacrificial) metals such as iron, zinc, or aluminum. This process is used to purify spent electrolytic solutions and for the treatment of waste'Xaters, leachates, and sludges bearing heavy metals. Also called ELECTROLYTIC RECOVERY. 0 The process of heating two substances that are placed in contact with each other for the purpose of bringing about some change in one of them such as changing iron to steel by surrounding it with charcoal and then heating it. Cementation Tank (water) - A tank in which metal ions are precipitated onto scrap aluminum, steel or other metals. The collected metal can be sent to a smelter for recovery. This process does not require electric current. Centrcilized Waste Treatment (CWT) Facility (water) - A facility designed to properly handle treatment of specific hazardous wastes from industries with similar waste streams. The wastewaters containlng the hazardous substances are transported to the facility for proper storage, treatment and disposal. Differen~ facilities treat different types of 'hazardous wastes. Centrate (water) - The water leaving a centrifuge after most of the solids have been removed. Centrifugal Pump (water) - A pump consisting of an impeller fixed on a rotating shaft that is enclosed in a casing, and having an inlet and discharge connection. As the rotating · impeller whirls the liquid around, centrifugal force builds up enough pressure to (orce the 'w ater through the discharge outlet. Centrifuge (water) - A mechanical device that uses centrifugal or rotational forces to separate solids from liquids. Ceramic Veneer (const) - Hard-burned, non-load-bearing, clay building units, glazed or unglazed, plain or ornamental. Cesspool (water) - A lined or partially lined excavatiOn or pit for dumping raw household wastewater for natural decomposition and percolation into the soil. Chain of Custody (water) - A record of each person involved in the handling and possession of a sample from the person who collected the sample to the person who analyzed the sample in the laboratory and to the person who witnessed disposal of the sample. Charge Chemistry (water) -. A branch of chemistry in which the destabilization and neutralization reactions occur between stable negatively charged and stable positively charged particles. Chase (const)- A continuous recess in a wall to receive pipes, ducts, and conduits. Check Valve (water)- A special valve with a hinged disc or flap that opens in the direction of normal flow and is forced shut when flows attempt to go in the reverse or opposite direction of normal flows. Chemical Grouting (water) - Sealing leaks in a.-pipeline or manhole structure by injecting a chemical grout. In pipelines, the chemicals are injected through a device called a "packer." In operation, the packer is located at the leak point with the use of a television camera. Inflatable boots at either end of the packer isolate the leak point · and the grouting

GLOSSARY OF CIVIL ENGINEERING TERMS

G ·13

chemicals are then forced into the leak under pressure. After allowing time for the to set, the packer is deflated and moved to the next location. ·

srout

Chemical Process (water) - A treatment process involving the addition of chemicals to achieve a desired level of treatment Any given process solution in metal finishing is also called a "chemical process." Chloramination (water) - The application of chlorine and ammonia to water to form chloramines for the purpose of disinfection. Chloramines (water) - Compounds formed by the reaction of hypochlorous acid (or aqueeus chlorine) with ammonia. Chlorination (water) - The application of chlorine to water, generally for the purpose of disinfection, but frequently for accomplishing other biological or chemical results (aiding coagulation and controlling tastes and odors). Chlorinator (water) - A metering device which is used to add chlorine to water. Chlorine Demand (water) - Chlorine demand is the difference between the amount qf chlorine added to water and the amount of residual chlorine remaining ~er a given contact time. Chlorine demand may change with dosage, time, temperature, pH, and nature and amount of the impurities in the water. Chlorophenoxy (water) - A class of herbiddes that may be found in domestic water supplies and cause adverse health effects. Two widely used chlorophenoxy herbicides are 2,4D (2,4Dichlorophenoxy acetic acid) and 2,4,5TP (2,4,5Trichlorophenoxy propionic add (silvex)). Chlororganic (water) - Organic compounds combined with chlorine. These compounds generally originate from, or are associated with, life processes such as those of algae in water. Christy Box (water) - A box placed over the connection between the pipe liner and the house sewer to hold the mortar around the cleanout wye and riser in place. Chromium (water) - A hard, brittle metallic element often used in- metal alloys and as a corrosion-resistant surface coating for metal parts. Chromium is an especially toxic metal, with hexavalent chromium being appreciably more toxic than _trivalent chromium. Inadequate or improper handling and disposal of chromium may create serious environmental hazards. Also see CHROME PLATE, HEXAVALENT CHROMIUM and TRIVALENT CHROMIUM. Ciliates (water) - A class of protozoans distinguished by short hairs on all or part of their bodies. Circle of Influence (water) - The circular outer edge of a depression produced in the water table by the pumping of water from a well. Also see CONE OF INFLUENCE and CONE OF DEPRESSION. Circuit Breaker (water) - A safety device in an electric circuit that automatically shuts off the circuit when it becomes overloaded. The device can be manually reset. Cistern (water) -A small tanl~usually covered) or a storage fadlity used to store water for a home or farm. Often used to ·store rainwater. Cladding (const) - The external covering to the frame or structural walls of a building or structure. The veneer is non- load-bearing, and as such it is designed to carry only its own weight (dry and/or wet), and a limited number of loads such as wind and seism. In

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GLOSSARY OF CIVIL ENGINEERING TERMS

relationship with the structure it encloses, it can be either fully bonded or separated by an air barrier

Clarification (water) - Any process or combination of processes the main purpose of which is to . reduce the concentration of suspended matter, in a liquid. Clarifier (water) - A large circular or rectangular tank or basin in which water is held for a period of time during which the heayier suspended solids settle to the bottom Clarifiers are also called settling basins and sedimentation basins. Cleanout (water) - An opening (usually covered or capped} in a wastewater collection system used for inserting tools, rods or snakes while cleaning a pipeline or clearing a stoppage. Cleanout, Two-way (water) - A cleanout designed for rodding or working a snake into a pipe in either direction. Two-way cleanouts are often used in building lateral pipes at or near a property line. Clear Well (water) - A reservoir for the storage of filtered water of sufficient capacity to prevent the need to vary the filtration rate with variations in demand. Also used to provide • chlorine contact time for disinfection. Client (const) - The persOn or legal entity who contracts wit!:} an individual or organization under a construction contract and pays for the works . . Coagulant (water) - A chemical that causes very fine particles to clump (floc) together into larger particles. This makes it easier to· separate the solids from the liquids by settling, skimming, draining or filtering. ·Coagulant Aid (water) - Any chemical or substance used to assist or modify coagulation. Coagulate (water) - The use of chemicals that cause very fine particles to clump (floc) together into larger particles. 'fhil! makes it easier to separate the solids from the liquids by settling, skimming, draining or filtering. Coagulation (water) - The clumping together of very fine particles into larger particles (floc) caused by the use of chemicals (coagulants). The chemicals neutralize the electrical charges of the fine particles, allowing them to come closer and form larger clumps. This clumping together makes it easier to separate the solids from the water by settling, skimming, draining or filtering. Cohesive (water) -Tending to stick together. Coliform (water) ·- A group of bacteria found· in the intestines of warm-blooded animals (including humans) and also in plants, soil, air and water. Fecal coliforms are a specific class of bacteria which only inhabit the intestines of warm-blooded animals. The presence of coliform bacteria is an indication that the water is polluted and may contain pathogenic (disease-causing) organisms. Collar Joints (const) -A vertical joint betWeen wythes or a wythe and backup. Collection Main (water) - A collection pipe to which building laterals are connected. Collection System (water) - A network of pipes, manholes, cleanouts, traps, siphons, lift stations and other strUctures used to collect all wastewater and wastewater-carried wastes of an area and transport them to a treatment plant or disposal system. The collection system 4ncludes land, wastewater lines and appurtenances, pumping stations and general property. Colloids (Water)- Very small, finely divided solids (particles that do not dissolve) that remain dispersed in a liquid for a long time due to their small size and electrical charge. When most of the particles in water have a negative electrical charge, they tend to repel each

GLOSSARY OF CIVIL ENGINEERING' TERMS other. This repulsion prevents the particles from clumping together, becomin& and settling out.

a·••

hiiWir,

Colorimetric Me~urement (water) - A means of·measuring unknown chemical conCentratioN in water by measuring a sample's color intensity. The specific color of the 1Amplt, developed·by addition of chemical reagents, is measured with a photoelectric colol'imettr or · is compared with ''color standards" using, or corresponding with, known concentrations of the chemical. Column (const) - A compression member with width not exceeding four times the thickneA, and with height more than three times the least lateral dimension. Column (const) - Member with a ratio of height-to-least-lateral dimension of 3 or greater used primarily to support axial compressive load. · Combined Available Chlorine (water)- The concentration of chlorine which is combined with ammonia (NH3) as chloramine or as other chloro derivatives, yet is still available to oxidize organic matter. . · Combined Available Residual Chlorine (water) -The concentration of residual ~lorine which is combined with ammonia (NH3) and/or organic nitrogen in water as a chloramine (or other chloro derivative) yet is still available to oxidize organic matter and use its bactericidal properties. · Combined Residual Chlorination (water) - The application of chlorine to water or wastewater to produce a combined available chlorine residual. The residual may consist of chlorine compounds formed by the reaction of chlorine with natural or added ammonia (NH3) or with certain organic nitrogen compounds. Combined Residual Chlorine (water) - The application of chlorine to water to produce combined available chlorine residual. This residual can be made up of monochloramines, dichloramines, and nitrogen trichloride. Combined Sewer (water)- A sewer designed to carry both sanitary wastewaters and storm or surface water runoff. Combined System (water) - A sewer designed to carry both sanitary wastewaters and s,torm or surface water runoff. · · Combined Wastewater (water) - A mixture of storm or surface runoff and other wastewater such as domestic or industrial wastewater. Combustible Uquid (water) - A liquid whose flashpoint is at or above lOO"F (38"C). Flammable liquids present a greater fire or explosion hazard than combustible liquids. Also see FLAMMABLE LIQUID. . Commercial Contribution (water) - Uquid and liquid
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GLOSSARY OF CIVIL ENGINEERING TERMS

Commodity-Demand Method (water) · A cost allocation method used by water utilities to · determine water rates for the various water user groups. This method considers the commodity costs (water, chemicals, power, amount of water use), demand costs (treatment, storage, distribution), customer costs (meter maintenance and reading, billing, collection, accounting) and fire protection costs. Common Services (const) • Common services are those services provided by the management contractor to each works contractor on an identical basis.. They include; for example, hoisting, welfare facilities and temporary roads. Compaction (water) • Tamping or rolling of a material to achieve able to support predicted loads.

asurface or density that is

Compaction Test (water) · Any method of determining the weight a compacted material is able to support without damage or displacement. Usually stated in pounds per square foot. Compatible Pollutants (water) • Those pollutants that are normally removed by the POTW treatment system. Biochemical oxygen demand (BOD), suspended solids (55), and ammonia are considered compatible pollutants. Competitive Tender (const) -See Traditional Contracting. Complete Treatment (water) • A method of treating water which consists of the addition of coagulant chemicals, flash mixing, coagulation-flocculation, sedimentation and filtration. Also called CONVENTIONAL FILTRATION. Composite concrete flexural members (const) · Concrete flexural members of precast and/ or . cast-in-place concrete elements constructed in separate placements but so interconnected that all elements respond to loads as a unit. Compound (water) ·A' pure substance composed of two or more elements whose composition is constant. For example, table salt (sodium chloride, NaCl) is a compound. Concentration Polarization (water) • A buildup of retained particles on the membrane surface due to dewaterptg of the feed closest to the membrane. The thickness of the concentration polarization layer is controlled by the flow velocity across the membrane. 0 Used in corrosion studies to indicate a depletion of ions near an electrode. 3) The basis for chemical analysis by a polarograph. Concentric Manhole C:one (water) - Cone tapers uniformly from barrel to manhole cover. Concrete (const) - Mixture of Portland cement or any other hydraulic cement, fine aggregate, coarse aggregate, and water, wi.th or without admixtures. Concrete Block (const) - A machine-formed masonry building unit composed of portland cement, aggregates, and water. Concrete, specified compressive strength of, (fc) (const) - Compressive strength of concrete used in designed and evaluated in accordance with provisions of Sec..504, ·expressed in megapascals (MPa). Whenever the quantity f c is under a radical sign, square root of numerical value only is intended, and result has units of megapascals (MPa). Concrete, structural lightweight (const) ·Concrete containing lightweight aggregate and has an air-dry unit weight is determined by " Test Method fur Unit Weight of Structural Ughtw~ight Concrete" (PNS/ASTM C 567), not exceeding 1900 kg/m'. Condensation (const) - Precipitation of liquid from its vapor resulting from lowering of the temperature under constant pressure,.especi8.lly the deposition of water from w~ moist air on to a relatively cold surface.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 17

Conductance (water) - A rapid method of estimating the dissolved solids content of a water supply. The measurement indicates the capacity of a sample of water to carry an electric current, which is related to the concentration of ionized substances in the water. Also called SPECIFIC CONDUCTANCE. Conductivity (water)- A measure of the ability of a solution (water) to carry an electric current. ConduGtor (water) - A substance, body, device or wire that readily conducts or carries electric current. 0 A pipe which carries a liquid load from one point to another point. In a wastewater collection system, a conductor is often a large pipe witl;l no service connections. Also called a CONDUIT, interceptor (see INTERCEPTING SEWER) or INTERCONNECTOR. 3) In plumbing, a line conducting water from the roof to the storm drain or other means of disposal. Also called a DOWNSPOUT. 4) In eleCtricity, a substance, body, device or wire that readily conducts or carries electric current: Conduit (water) - Any artificial or natural duct, either open or closed, for carrying fluids from one point to another. An electrical conduit carries electricity. Cone of Depression (water) - The depression, roughly conical in shape, produced in the water table by the pumping of water from a well. Also called the CONE OF INFLUENCE. Also see CIRCLE OF INFLUENCE. Cone of Influence (water) - The depression, roughly conical in shape, produced in the. water table by the pumping of water from a well. Also called the CONE OF DEPRESSION. Also see CIRCLE OF INFLUENCE. Coning (water) - Development of a cone-shaped flow of liquid, like a whirlpool, through sludge. This can occur in a sludge hopper during sludge withdrawal when the sludge becomes too thick. Part of the sludg~ remains in place while liquid rather than sludge flows out of the hopper. Also called coring. Conservative Pollutant (water) - A pollutant found in wastewater that is not changed while passing through the treatment processes in a conventional wastewater treatment plant. This type of pollutant may be removed by the treatment processes and retained in the plant's sludges or it may leave in the plant effluent. Heavy metals such as cadmium and lead are conservative pollutants. Consortia (const) - A consortium .is the grouping together of three or more organizations, generally of differing skills, with the .objective of carrying out a specific project. Constructability (const) - A system for achieving optimum integration of construction knowledge in the construction process and balancing the various project and environmental constraints to achieve maximizatiq_n_ _of project goals and construction perfortnance. (Complementary to buildability or substitutive of it?) Construction Activity (const) - The process of creating a project or part of a project by the employment of construction resources. Construction Contract (const) - An agreement entered into for · the construction, repair, renovation or restoration of abuilding or civil engineering work. Construction CostS (const)- All costs that arise from .t he resources used in the construction of a construction project excluding the costs of the land. Construction Design (const) - Development of the conceptual design into the more detailed design (working drawings), undertaken by an architect, construction engineer, architectural technician, professional builder, etc. Construction Firm (const)- See Contractor.

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GLOSSARY OF CIVIL ENGINEERING TERMS

CoNtruction Industry (const) - All parties in the industry ~gaged in designing, executing and maintaining buildings including those supplying materials. Construction Management (const) -The overall management of the processes required to bring the site operations of a project to a satisfactory conclusion, typically carried out either by a private consultant or an employee of the project client. Is a management form of contract synonymous with management contracting except that works contractors are appointed as direct contractors to the client, rather than as subcontractors to the contract manager. Construction Management Contract (canst) -This contract is similar to a Management Contract except that the client is the employer in each works construction contract. Construction Manager (const) - The perSon or firm responsible for the execution of a construction project Construction Materials (const) - All materials, elements and components used for the construction of projects that are incorporated in the final constructed product. Construction Method (const) - The mode of carrying out a construction process to arrive at a finished element, operation or product.

.

Construction Process (const) -The designing and construction of a project from the conception of the project in a client's mind to its completion for commissioning and use. Consultancy Service (const) - In relation to construction materials, processes ~d the survey and assessment of the condition of built constructions. Consultants (const) - The client's advisers on design, c;ost and other matters. Such advisers might include project managers. Contact Stabilization (water).- Contact stabilization is a modification of the conventional activated sludge process. In contact stabilization, two aeration '¥lks are used. One tank is for separate reaeration of the return sludge for at least four hours before it is permitted to flow into the other aeration tank to be mixed with the primary effluent requiring treatment. The process may also occur in one long tank. Contamination (water) - The introduction into water of microorganisms, chemicals, toxic substances, wastes, or wastewater in a concentration that makes the water unfit for its next intended use. Continuous Process (water) - A treatment process in which water is treated continuously in a tank or. reactor. The water being treated continuously flows into the tank at one end, is treated as it flows thro1,1gh the tank, and flows out the opposite end as treated water. Continuous Sample (water) - A flow of water from a particular place in a plant to the location where samples are collected for testing. This continuous stream may be used to obtain grab or composite samples. Frequently, several taps (faucets) will flow continuously in the laboratory to provide test samples from various places in a water treatment plant. Contract Administration Management (const) - Process by which a formal contractfor design or construction services ·is. administered including the issuing of instructions, change control procedures, payment and the measuring and reviewing of progress. Contract Manager (canst) -. A manager appointed by a contractor to be responsible for managing a number of site contracts. Contractor (const) - A person or organization which, as a party to a contract, is responsible for the organization, management, and ·execution of that construction comprised in the contract with the employer.

GLOSSARY OF CML ENGINEERING mMS

Contribution (water) - Waters, wastewaters or liquid-carried wutet entering a wut.water collection system. Control Loop (water) • The path through the control system between the sensor, which measures a process variable, and the controller, whidt controls or adjusts the proceu variable. Control- System (water) - An instrumentation system which senses and controls its own operation on a dose, continuous basis in what is called propOrtional (or modulating) control. Conventional Filtration (water) - A method of treating water which consists of the addition of coagulant chemicals, flash mixing, coagulation-flocculatiOn, sedimentation and filtration. Also called COMPLETE TREATMENT. Also see DIRECT FILTRATION and INUNB FILTRATION. Conventional Pollutants (water) - Those pollutants which are us~y found in domestic, commercial or industrial wastes such as suspended solids, biochemical oxygen demand, pathogenic (disease-causing) organisms, adverse pH levels, and oil and grease. Conventional Treatment (water) -The preliminary treatment, sedimentation, flotation, trickling filter, rotating biological contactor, activated sludge and chlorination wastewater treatment processes. Coping (const) - A cap or finish on top of a wall, pier, chimney, or pilaster to prevent penetration of water to mason:y wall. Corbel (const) -·Successive course ~f masonry projecting from the face of a wall to increase its thickness or to form a shelf or ledge. Corporation Stop (water) - A water service shutoff valve located at a street water main. This valve cannot be operated from the ground surface because it is buried and there is no valve box. Also called a corporation cock. Corrosion (const) • Deterioration of a metal by chemical or electrochemical reaction with its environment (BS 3660). Occasionally used, incorrectly, to apply to non-metallic materials, eg. concrete Corrosion (water) - The graqual decomposition or destruction of a material by chemical action, often due to an electrochemical reaction~ Corrosion may be caused by (1) stray. ctirrent electrolysis, (2) galvanic corrosion caused by dissimilar metals, 01 (3) differential . concentration cells. Corrosion starts at the surface of a material and moves inward. Corrosion Inhibitors (water) -Substances that slow the rate of corrosion. Corrosive Gases (water) - In water, dissolved oxygen reacts readily with metals at the anode of a corrosion cell, accelerating the rate of corrosion until a film of oxidation products such as rust forms. At the cathode where hydrogen gas may form a coating on the cathode and slow the corrosion rate, oxygen reacts rapidly with hydrogen gas forming water, and again increases the rate of corrosion. Corrosive Material (water) • A mat~ which through its chemical action is destructively injurious to body tissues or other materials. Corrosivity (water) - An indication of the corrosiveness of a water. The corrosiveness of a water is ,described by the water's pH, alkalinity, hardness, temperature, total dissolved aolids, dissolved oxygen cOncentration. and the Langelier Index. • Cost control (const) • The process of controlling th.e cost of a project within a predetermined sum throughout its various stages from inception to completion. ·

G- 20

GLOSSARY OF CIVIL ENGINEERING TERMS

Coulomb (water) - A measurement of the amount of electri'al charge carried by an electric current of one ampere in one second. One coulomb equals about 6.25 x 1018 electrons (6,250,000,000,000,000,000 electrons). Counterceurrent Rinsing (water) - A rinsing procedure in which rinse water flows from tank to tank in a direction that is opposite to movement of parts being rinsed from tank to tank. Coupling (water) - A threaded sleeve used to connect two pipes. 0 A device used to connect two adjacent parts, such as a pipe coupling, hose coupling or drive coupling. Coupon (water) - A steel specimen inserted into water to measure the corrosiveness of water. The rate of corrosion is measured as the loss of weight of the coupon (in milligrams) per surface area (in square decimeters) exposed to the water per day. 10 decimeters= 1 meter • 100 centimeters. Course (const) - A continuous horizontal layer of masonry units bonded together. Crack (const) - Linear .discontinuity produced by fracture. Elongated narrow opening. Synonyms can include: break, split, fracture, fissure, separation, cleavage, in various applications Cradle to Grave (water) - A term used to describe a hazardous waste manifest system used by regulatory agencies to track a hazardous waste from the point of generation to the hauler and then to the ulti~te disposal site. · Crazing (const) - Network of surface cracks. Used generally to describe surface cracking of concrete surfaces and paint film. Also used specifically to describe the fine network cracking of ceramic glazes by, for example, differential thermal expansion between glaze and tile body, or moisture expansion of the body Creep (const) -Slow deformation of a stressed material at temperatures which may be Within or above the normal working range of the material • Cross Braces (water) - Shoring members placed across a trench to hold other horizontal and

vertical shoring members in place. Cross Connection (water) - A connection between a drinking (potable) water system and an unapproved water supply. For example, if you have a pump moving nonpotable water and hook into the drinking water system to supply water for the pump seal, a cross , connection or 11\iXing between the two water systems can occur. This mixing may lead to contamination of the drinking water. Cryptosporidium (water) - A waterborne intestinal parasite that causes a disease called cryptosporidiosis (CRIP-toe-spo-rid-ee-0-sis) in infected humans. Symptoms of the disease include diarrhea, cramps, and weight loss. Cryptosporidium contamination is found in most surface waters and some groundwaters. Commonly referred to as "crypto.'' Curb inlet (water) - A chamber or well built at the curbline of a street to admit gutter flow to the storm water drainage system. Also see STORM WATER INLET and CATCH BASIN. Curb Stop (water) - A water service shutoff valve located in a water service pipe near the curb and betWeen the water main and the building. This valve is usually operated by a wrench or valve key and is used to start or stop flows in the water service line to a building. Also called a curb cock. Curie (wa~- A measure of radioactivity. One Curie of radioactivity is equivalent to 3.7 x 1010 or 37,000,000,000 nuclear disintegrations per second. Current (water) - A movement or flow ofelectricity; Water flowing in a pipe is measured in gallons per second past a certain point, not by the number of water molecules going past a

GLOSSARY OF CIVIL ENGINEERING TERMS

G • 21 point. Electric current is measured by the number of coulombs per second flowin& pMt 1

certain point in a conductor. A coulomb iS equal to about 6.25 x 1018 electroN (6,250,000,000,000,000,000 .electrons). A flow of one coulomb per second is called one ampere, the unit of the rate of flow of current. Curtain Wall (const)- Anon-load-bearing exterior wall. Curvature friction (const) - Friction resulting from bends or curves in the speCified prestressing tendon profile. · Curvilinear (water) - In the shape of a curved line. Cyanide (water) -The cyanide ion (CN-) consiSts of carbon (C) arid nitrogen (N). Cyanide is commonly found in metal plating wastewaters because most metal cyanides are soluble and plating occurs readily from cyanide solutions. The cyanide ion is extremely toxic and must be removed from metal wastes before discharge to the environment. Treatment of wastes containing cyanide under acidic conditions may produce extremely toxic gases which must never come in contact with people or animals. Cycle (water) - A complete alternation of voltage and/or current in an alternating current (A. C) circuit.

D D 0 (water) - Abbreviation of DiSsolved Oxygen. DO is the molecular (atmospheric) oxygen dissolved in water or wastewater. D P D (water) - A method of measuring the chlorine residual in water. The residual may be determined by either titrating or comparing a developed color with color standards. DPD stands for N, Ndiethylpphenylenediamine. Dado (const) -A rectangular groove cut across the grain of a frame member. Dalton (water) - A unit of mass designated as one-sixteenth the mass of oxygen16, the lightest and most abundant iSotope of oxygen. The dalton iS equivalent to one mass unit. Dampness (const) - Condition of being slightly wet: usually not so wet that liquid water is evident, eg. wetness caused by condensation on a porous substrate or water transmitted up a porous wall by capillarity Datum Une (water) - A line from which heights and depths are calculated or measured. Also called a datum plane or a datum level. Day Tank (water) - A tank used to store a chemical solution of known concentration for feed to a chemical feeder. A day tank usually stores sufficient chemical solution to properly treat the water being treated for at least one day. Also called an AGE TANK. DCP (Dyruimic Cone Penetrometer) (const) - Instrument used to measure the strength of soil and granular materials used in roadway construction Dead End (water) - The end of a water main which iS not connected to other parts of the distribution system by means of a connecting loop of pipe. Deadend Manhole (water) - A manhole located at the upstream end of a sewer and having no inlet pipe. Also called a TERMINAL MANHOLE.

G • 22

GLOSSARY OF CIVIL ENGINEERING TERMS

Debris (water) - Any material in wastewater found floating, suspended, settled or moving along the bottom of a sewer. This material may cause stoppages by getting hung up on roots or settling out in a sewer. Debris includes grit, Raper, plastic, rubber, silt, and all materials except liquids. Decant (water) -To draw off the upper layer of liquid (water) after the heavier material (a solid or another liquid) has settled.

Decomposition (const) - The separation of a material into elements or parts Defect (const) - The non-conformity of the result of ·a test with the specification for a characteristic (ISO 2071). In Building Pathology, used sometimes almost as a synonym of 'fault' or 'failure', but preferred meaiung is to indicate only a deviation from some (perceived) standard which may, but will not necessarily result in a failure Deformed reinforcement (canst) - Deformed reinforcing bars, bar mats, deformed wire, welded plain wire fabric, and welded deformed wire fabric. Delamination (const) - The breakdown ofa material by separation of the layers of which it is composed De;ign &t Build (canst) - Design &t Build or Design &t Construction is a form of construction procurement whereby the contractor who constructs the works, also undertakes all of, or a proportion of, the de-sign of the works under one contract. Design &t Construct (const) - See Design &t Build. Design &t Manage (const) - Ah extension to management contracting in which a design responsibility is included as well as construction. .Deterioration (const) -A reduction in ability to perform up to the anticipated standard Development length (const) - Length of embedded reinforcement•required to develop the design strength of reinforcement Deviation (gen) - Divt!tgence of the value of a quantity from a standard or reference value. Used generally to indicate a divergence from what was originally intended. Dipstick (canst) - The dipstick is an instrument used to calculate the elevation profile of the road. Drip Cap (const) - A ·molding placed on top of the head casing of a window frame to direct water away from it. Durability (const) - The quality of maintaining satisfactory aesthetic, economic, and functional performance for the useful life of the structure Dynamic Sensors (canst)- traffi!= triggered sensors

GLOS.SARY OF CIVIL ENGINEERING TERMS

G- 23

E E G L (water) - ENERGY GRADE LINE Earth Shift (soil) - The movement or dislocation of underground soil or structure. Earth shift is usually caused by external forces such as surface loads, slides, stresses or nearby construction, water movements or seismic forces. Easement (water) - Legal right to use the property of others for a specific purpose. For example, a utility company may have a five-foot easement along the property line of a home. This gives the utility the legal right to install and maintain a sewer line within the easement. Eccentric Manhole Cone (water) - Cone tapers non-uniformly from barrel to manhole cover with one side usually vertical. Economic Control (const) - Ensuring project costs are kept within budget and measuring ongoing progress of work in order to facilitate payment of contractors and subcontractors. Eductor (water) - A hydraulic device used to create a negative pressure (suction) by forcing a liquid through a restriction, such as a Venturi. An eductor or aspirator (the hydraulic device) may be. used in the laboratory in place of a vacuum pump. As an injector, it is used to produce vacuum for chlorinators. Sometimes used instead of a suction pump. Effective depth of section (d) (const) - Distance measured from extreme compression fiber to centroid of tension reinforcement.' '

Effective prestress (const) - Stress remaining in prestressing tendons after all losses have occurred, excluding effects of dead load and super imposed load. Effective Range (water) - That portion of the design range (usually from 10 to 90+ percent) in which an instrument has acceptable accuracy. Also see RANGE and SPAN. Effective Size (ES) (water) - The diameter of the particles in a granular sample (filter media) for which 10 percent of the total grains are smaller and 90 percent larger on a weight basis. Effective .size is obtained by passing granular material through sieves with varying dimensions of mesh and weighing the material retained by each sieve. The effective size is also approximately the average size of the grains. Effective Soil Depth (water) - The depth of soil ·in the leach field trench that provides a satisfactory percolation area for the septic tank effluent. Efflorescence (const) - White salts brought to the surface of porous building materials by water movement (BS 4049) Efflorescence (water) - The powder or crust formed on a substance when moisture is given off upon exposure to the atmosphere. Effluent (water) - Water or other liquid - raw (untreated), partially or completely treated flowing FROM a reservoir, basin, treatment process, or treatment plant. Effluent Limits (water) - Pollutant limitations developed by a POTW for industrial plants discharging to the POTW ·system. At a minimum, all industrial facilities are. required to comply with federal prohibited discharge standards. The industries covered by federal categorical standards must also comply with the appropriate discharge limitations. The POTW may also establish local limits more stringent than or in addition to the federal standards for some or all of its industrial users. Ejector (water) - A device used to disperse a chemical solution into water being treated.

G- 21

GLOSSARY OF CIVIL ENGINEERING TERMS

Elbow (water) - A pipe fitting that connects two pipes at an angle. The angle is usually 90 degrees Wlless another angle is stated. Also called an "ell." Electrochemical Corrosion (water) - The decomposition of a material by: (1) stray current electrolysis, (2) galvanic corrosion caused by dissimilar metals, and (3) galvanic corrosion caused by differential electrolysis. Electrodialysis (water) - The selective separation of dissolved solids on the basis of electrical charge, by diffusion through a semi-permeable membrane across which an electrical potential is imposed. Electrolyte (water) - A substance which dissociates (separates) into two or more ions when it is dissolved in water. Element (gen) - A substance which cannot be separated into its constituent parts and still retain its chemical identity. For example, sodium (Na) is an element. Elevation (gen) -The height to which something is elevated, such as the.height above sea level. Elutriation (water) - The washing of digested sludge with either fresh water, plant effluent or other wastewater. The objective is to remove (wash out) fine particulates and/ or the alkalinity in sludge. This process reduces the demand for conditioning chemicals and improves settling or filtering characteristics of the solids. _,,I Embedded Strain Gauge (const) - A sensor that measures static and horizontal strains in concrete and asphalt layers by means of five different models placed in various locations and orientations. Embedment length (const) - Length of embedded reinforcement provided beyond a critical section. Employer (const) -Sec Client or Owner Empty Bed Contact Time (water)- The time required for the liquid in a carbon adsorption bed to pass through the carbon column assuming that all liquid passes through at the same velocity.lt is equal to the volume of the empty bed divided by the flow rate. Emulsion (water)- A liquid mixture of two or more liquid substances not normaiJy dissolved in one another; one liquid is held in suspension inthe other. Endrin (water) - A pesticide toxic to freshwater and marine aquatic life that produces adverse health effects iii domestic water supplies. Energy Design (const) - Work associated with energy systems within an overall social context, including supply systems and the development of alternative energy sources. ENERGY GRADE LINE (EGL) (water) - A line that represents the elevation of energy head (in feet) of water flowing in a pipe, conduit or channel. The line is drawn above the hydraulic grade line (gradient) a distance equal to the velocity head (V2/2g) of the water flowing at each section or point along the pipe or channel. Also see HYDRAULIC GRADE Ll NE. Enteric (water) - Of intestinal origin, especiaiJy applied to wastes or bacteria. Entrain (water) - To trap bubbles in water either mechanically through turbulence or chemicaiJy through a reaction. Enzymes (water) -Organic substances (produced by living organisms) which cause or speed up chemical reactions. Organic catalysts and/ or biochemical catalysts. Epidemic (water) -A disease that occurs in a large number of people in a locality at the same · time and spreads from person to person.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 25

Epilimnion (water) - The upper layer of water in a thermally stratified lake or reservoir. This layer consists of the warmest water and has a fairly uniform (constant) temperature. The layer is readily mixed by wind action. Equalizing Basin (water) - A holding basin in which variations in flow and composition of a liquid are averaged. Such basins are used to provide a flow of reasonably uniform volume and·composition to a treatment unit. Also called a balancing reservoir. Equilibrium, Calcium Carbonate (water) - A water is considered stable when it is just saturated with calcium carbonate. In this condition the water will neither dissolve nor deposit calcium carbonate. Thus, in this water the calcium carbonat~ is in equilibrium with the hydrogen ion concentration. Equipment/plant (const) - All mechanical plant and machines used as a means of production on a construction site Ester (water)- A compound formed by the reaction between an acid and an alcohol with the elimination of a molecule of water. Estimated Flow (water) - A rough guess of the amount of flow in a collection system. When greater accuracy is needed, flow could be computed using average or typical flow quantities. Even greater accuracy would result from metering or otherwise measuring the · actual flow. Estimating (const) -The task of estimating the likely cost of construction works either on behalf of clients or on behalf of contractors bidding for work. Estuaries (water) - Bodies of water which are located at the lower end of a river and are subject to tidal fluctuations. Eutrophic (water) - Reservoirs and lakes which are rich in nutrients and very productive in terms of aquatic animal and plant life. Eutrophication (water)- The increase in the nutrient levels of a lake or other body of water; this usually causes an increase in the growth of aquatic animal and plant life. Evaporation (water)- The or ammonia vapor).

pro~ess

by which water or other liquid becomes a gas (water vapor

Evapotranspiration (water) - TI1e process by which water vapor passes into the atmosphere from living plants. Also called TRANSPIRATION. 0 The total water removed from an area by transpiration (plants) and by evaporation from soil, snow and water surfaces. Exfiltration (const) - Leakage out of a material or structure Exfiltration (water) -Liquid wastes and liquid-carried wastes which unintentionally leak out of a sewer pipe system and into the environment. Extrados

(wate~-

The upper outside curve of a sewer pipe or conduit.

G- 26

- GLOSSARY OF CIVIL ENGINEERING TEAMS

F F/M Ratio (water)- Food to microorganism ratio. A measure of food providedto bacteria in an aeration tank. Faced Wall (const) - A wall in which the masonry facing and backing are of different materials and son bonded as to exert a cominon reaction under load. Fadlities Management (const) - Management of the organization in operating and maintaining a completed project. Facultative (water) - Facultative bacteria can use either dissolved molecular oxygen or oxygen obtained from food materials such assulfate or nitrate ions. In other words, facultative bacteria can live under aerobic or anaerobic conditions. Facultative Pond (water)- The most common type of pond in current use.The upper portion (supernatant) is aerobic, while the bottom layeris anaerobic. Algae supply most of the oxygen to the supernatant. 4

Failure (const) - The termination of the ability of an item to perform a required function. See defect &: fault Fast Tracking (const) - Fast tracking is a means of reducing project time by the overlapping of design and construction. Each trade's work commences as its plans and specifications are s~bstantially completed. Fatigue (const) - The weakening of a material caused by repeated or alternating loads; may be used in conjunction with either static or dynamic loading Fault (const) - Any defect which impairs normal operation; 2) seismic events start. See failure &: defect

geol~gic

discontinuity where

Fault (soil) - A fracture in the earth's crust .that leaves land on one side of the crack out of alignment with the other side. Faults are generally a result of earth shifts and earthquakes. Feasibility Study (const) - An initial study of a project, or method of operation, in outline form to determine the physical and economic feasibility. Feeboard; (water) - !he vertical distance from the normal water surface to the top of the confhung wall. 0 The vertical distance from the sand surface to the underside of a trough in a sartd filter. This distance is also called AVAlLABLE EXPANSION. Feedwater (water) - The water that is fed to a treatment process; the water that is going to be treated. Filamentous Organisms (water) - Organisms that grow in a thread or filamentous form. Common types are Thiothrix and Actinomycetes.A common cause of sludge bulking in the activated sludge process. • Filter Aid (water) - A chemical (usually a polymer) added to water to help remove fine colloidal suspended solids. Final design (const) - The fully detailed project as constructed; the design on which the drawings for construction are based. Finished Wafer (water) - Water that has passed through a water treatment plant; all the treatment processes are completed or "finished." This water is ready to be delivered to consumers. Also cal1ed J;'RODUCT WATER.

GLOIIAAV OF CIVIL ENGINEERING TERMS

G- 27

Fire Point (water) - The lowest temperature of a liquid at which a mixture of air and vapor from the liquid will continue to bum.

Fissure (const) -A crack or split Fixed Price Contract (const) - A fixed price contract may be a lump sum contract or a measurement contract based on fixed prices for units of specific work. Fla~~~tes (water) - Microorganisms that move by the action of tail-like projections.

Flap Gate (water) - A hinged gate that is ~9unted at the top of a pipe or channel to allow flow in only one direction. Flow in. ,the wrong direction closes the gate. Also see CHECK VALVE and TIDE GATE. Flash Point (water) -The minimum temperature of a liquid at which the liquid gives off a vapor in sufficient concentration to ignite when tested under specific conditions. Flight (const) - A series of steps extending from floor to floor, or from a floor to an intermediate landing or platform. Landings are used where turns are necessary or to break up long climbs. Flights (water) - Scraper boards, made from redwood or other rotresistant woods or plastic, used to collect and move settled sludge or floating scum. Float (Control) (water) - A device used to measure the elevation of the surface of water. The float rests on the surface of the water and rises or falls with it. The elevation of the water surface is measured by a rod, chain, rope or tape attached to the float. Float Line (water) - A length of rope or heavy twine attached to a float, plastic jug or parachute to be carried by the flow in a sewer from one manhole to the next. This is called "stringing the line" and is used for pulling through winch cables, such as for bucket machine work or closed circuit television work. Float System (water) - A method of operating a water storage facility. Daily flow into the facility is approximately equal to the average daily demand for water. When consumer demands for water are low, the storage facility will be filling. During periods of high demand, the facility will be emptying. Floc (water) - Clumps of bacteria and particulate impurities that have come together and formed a cluster. Found in flocculation tanks and settling or sedimentation basins. Flocculation (water) - The gathering together of fine particles after coagulation to form larger particles by a process of gentle mixing. Flotation (water) - The stress or forces on a pipeline or manhole structure located below a water table which tend to lift or float the pipeline or manhole structure. 0 The process of raising suspended matter to the surface of the liquid in a tank where it forms a scum layer that can be removed by skimming. The suspended matter is raised by aeration, the evolution of gas, the use of chemicals, electrolysis, heat or bacterial decomposition. Flotsam (water) -Material floating or drifting about on the surface of a body of water. Flow (water) -The continuous movement of a liquid from one place to another. Flow Equalization System (water) - A device or tank designed to hold back or store a portion of peak flows for release during low flow periods." Flow isolation (water)- A procedure used to measure inflow and infiltration (1/1). A section of sewer is blocked off or isolated and the flow from the section is measured. Flow Line (water) - The top of the wetted line, the water surface or the hydraulic grade line of water flowing in an open channel or partially full conduit. 0 The lowest point of the

G- 28

GLOSSARY OF CIVIL ENGINEERING TERMS

channel inside a pipe or manhole. See INVERT. NOTE: (2) is an improper definition, althpugh used by some contractors. . Fluidized (water) - A mass. of solid particles that is made to flow like a liquid by injection of water or gas is said to. have been fluidized. In water treatment, a bed of filter media is fluidized by backwashing water through the filter. 1

Flume (water) - An open conduit of wood, masonry, metal, or plastic constructed on a grade and sometimes elevated. Sometimes called an "aqueduct" or "channel." Fluoridation (water) - The addition of a chemical to increase the concentration of fluoride ions in drinking water to a predetermined optimum limit to reduce the incidence (number) of dental caries (tooth decay) in children. Defluoridation is the removal of excess fluoride in drinking water to prevent the mottling (brown stains)of teeth. Flusher Branch (water) - A line built specifically to allow the introduction oflarge quantities of water to the collection system so the line scan be "flushed out" with water. Also installed to provide access for equipment to clear stoppages in a sewer. Fl4.!!hing (water) - A method used to clean water distribution lines. Hydrants are opened and water with a high velocity flows through the pipes, removes deposits from the pipes, and. flows out the hydrants. Flux (water) - A flowing or flow. Foot Valve (water)- A special type of check valve located at the bottom end of the suction pipe on a pump. This valve opens when the pump operates to allow water to enter the suction pipe but closes when the pump shuts off to prevent water from flowing out of the· suction pipe. Force Main (water) -A pipe that carries wastewater under pressure ~m the discharge side of a pump to a point of gravity flow downstream. Fracture (const) - To make or become discontinuous otherwise than by cutting. Usually of relatively brittle materials · Free Available Chlorine (water)- The amount of chlorine available in water. This chlorine may be in the form of dissolved gas (Cl2), hypochlorous acid (HCX3), or hypochlorite ion (Ocl), but does not include chlorine combined with an amine (ammonia or nitrogen)or other organic compound. Free Chlorine (water) - Free chlorlhe is chlorine (CI2)in a liquid or gaseous form. Free chlorine combines with water to form hypochlorous (HOCI) and hydrochloric (HCl) acids. In wastewater free chlorine usually combines with an amine (ammonia or nitrogen)or other organic comp<}unds to form combined chlorine compounds. Free Oxygen (water) - Molecular oxygen available for respiration by organisms. Molecular oxygen is the oxygen molecule, 02.that is not combined with another element to form a compound. Free Residual Chlorination (water) - The application of chlorine to water to produce a free available chlorine residual equal to at least 80 percent of the total residual chlorine (sum of free and combined available chlorine residual). Friability (w~ter) - The ability of a soil or substance to crumble under moderate or light pressure. .

the

Friction Loss (water) -The head lost by water flowing in a stream or conduit as the result of disturbances set up by. the contact .between the moving water and its containing conduit and by intermolecular friction.

GLOSSARY OF CIVIL ENGINEERING TERMS

G • 29

Fungi (water) - Mushrooms, molds, mildews, rusts, and smuts that are small non-chlorophyll· bearing plants lacking roots, stems and leaves. They occur in natural waters and grow best in the absence of light. Their decomposition may cause objectionable tastes and odors in water. Fungus (const) - A plant growth obtaining its nutrition by breakdown of organic matter, usually associated with the presence of dampness, eg. in timber. The plants iue characterized by the absence of chlorophyll. FWD (Falling Weight Deflectometer) (const) - Instrument that determines the structural condition of each pavement layer.

G Gage (water) - A device for checking or measuring a particular dimension of something, using specific standardized units. For example, a gage might measure the elevation of a water surface, the velocity of flowing water, the pressure of water, the amount or intensity of precipitation, and the depth of snowfall. Gages also are used to determine the location or position of equipment during installation and after operation. Gage Pressure (water) - The pressure within a closed container or pipe as measured with a gage. Ih contrast, absolute pressure is the sum of atmospheric pressure (14.7 lbs/sq in) PLUS pressure within a vessel (as measured with a gage). Most pressure gages read in "gage pressure" or psig (pounds per square inch gage pressure). Galvanize (water) - To coat a metal (especially iron or steel) with zinc. Galvanization is the process of coating a metal with zinc. · Garnet (water) -A group of hard, reddish, glassy, mineral sands made up of silicates of base metals (calciUin. magnesium, iron and manganese). Garnet has a higher density than sand. Gas (Sewer) (water) - (See SEWER ~AS) Gasification (water) - The conversion of soluble and suspended organic materials into gas during aerobic or anaerobic decomposition. In clarifiers the resulting gas bubbles can become attached to the settled sludge and cause large clumps of sludge to rise and float on the water surface. In anaerobic sludge digesters, this gas is collected for fuel or disposed of using a waste gas burner. Gate (water) - A movable watertight barrier for the control of a liquid in a waferway. Gauge Pipe (water) - A number that defines the thickness of the sheet used to make steel pipe. The larger the number, the thinner the pipe wall. Geology- The science that deals with the origin, history and structures of the earth, as recorded in the rocks, together with the forces and processes now operating to modify rocks. Germicide (water) (water) - A substance formulated ·to kill germs or microorganisms. The germicidal properties of chlorine make it an effective disinfectant. Giardia (water) - A waterborne intestinal parasite that causes a disease called giardiasis (GEEareDIEuhsis) in infected humans. Symptoms of the disease include diarrhea, cramps, and weight loss. Giardia contamination .is found in most surface waters and some groundwaters. · Giardiasis (water) - Intestinal disease caused by an infestation of Giardia flagellates. GPCD (water) -Initials standing for "Gallons Per Capita Per Day."

G- 30

GLOSSARY OF CIVIl ENGINEERING TERMS

GPO (water) -Initials standing for "Gallons Per Day." GPM (water)- initials standin~ for "Gallons Per Minute." GPY (water)- Initials standing for "Gallons Per Year." Grab Sample (water)- A single sample of water collected at a particular time and place which represents the composition of the water only at that time and place. Grade (water) - The elevation of the invert (or bottom) of a pipeline, canal, culvert, or similar conduit. 0 The." inclination or slope of a pipeline, conduit, stream channeL or natural ground surface; usually expressed in terms of the ratio or percentage of number of units of vertical rise or fall per unit of horizontal distance. A 0.5 percent grade would be a drop of one half fC?Ot per hundred feet of pipe. Grade Ring (water) - A precast concrete ring 4 to 12 inches high which is placed on top of a manhole cone to raise the manhole cover frame flush with the surface grade. Sometimes called a "spacer." Gradient - The upward or downward slope of a pipeline. Granular (const) - Any substance that appears to consist of separate granules or grains. Examples are sand and gravel. Gravimetric - A means of measuring unknown concentrations of water quality indicators in a sample by WEIGHING a precipitate or residue of the sample. Gravity Flow (water) - Water· or wastewater flowing from a higher elevation to a lower elevation due to the force of gravity. The water does not flow due to energy provided by a pump. Wherever possible, wastewater collection systems are designed to use the force of gravity to convey waste liquids and solids. Grease Trap (water) - A receptacle designed to collect and retain grease and fatty substances usually found in kitchens or from similar wastes. It is installed _in the drainage system between the kitchen or other point of production of the waste and the building wastewater collection line. Commonly used to control grease from restaurants. Greensand (water) - A mineral (glauconite) material that looks like ordinary filter sand except that it is green in color. Greensand is a natural ion exchange material which is capable of softening water. Greensand which has been treated with potassium permanganate (KMn04) is called manganese greensand; this product is used to remove iron, manganese and hydrogen sulfide from ground waters. Grinder Pump (~ater) - A small submersible centrifugal pump with an impeller designed to serve as a pump with grinder elements which. grind solids into small pieces that pass through the pump impellers. Grit (water) - The heavy material present in wastewater, such as sand, coffee grounds, · eggshells, gra~el and cinders. Grit Catcher (water) -A chamber usually placed at the upper end of a depressed collection line or at other points on combined or storm water collection lines where wear from grit is possible. The chamber is sized and shaped to reduce the velocity of flow through it and thus permit the settling out of grit. Also called a ;'sand catcher." See GRIT CHAMBER and SAND TRAP. Grit Chamber (water) - A detention chamber or an enlargement of a collection line designed to reduce the velocity of flow of the liquid to permit the separation of mineral solids from organic solids by differential sedimentation.

GLOSSARY OF CIVIL ENGINEERING TERMS

G • 31

Grit Channel (water) - An enlargement in a collection line where grit can easily settle out of the flow. 0 The waterway of a grit chamber. Grit Tank (water)- A structure located at the inlet to a treatment plant for the accumulation and removal of grit. Grit Trap (water) - A permanent structure built into a manhole (or other convenient location in a collection system) for the accumulation and easy removal of grit. Groundwater (water) - Subsurface water in the saturation wne from which wells and springs are fed. In a strict sense the term applies only to water below the water table. Also called "phreatic water" and "plerotic water." Groundwater Depth (water) - The distance of the groundwater table below the surface at any · selected location. Groundwater Elevation (water) - The elevation of the groundwater table above mean sea level at any selected location. Groundwater Table (water) - The .average depth or elevation of the groundwater over a selected area. Grout {const) - A substance in a paste or liquid form which solidifies after placement or treatment. Used to fill spaces, holes or voids in oilier materials. Grout (const) -Extremely fluid mixture of sand and gravel; Grouted Masonry (const) - Masonry in which the interior joints are filled by pouring grout into them as the work progresses. Gunite (const) - A mixture of sand and cement applied prieumatically that forms a highdensity, resistant concrete.

H Hairline Crack (water) - A stress crack in a pipe;·the crack looks like a piece of hair. Hallow Masonry Unit (const) - Masonry .with net cross-seetional area in any plane parallel to the bearing surface less than 75% of its gross cross-sectional area measured in the same plane. Hallow Wall (const) - A wall of masonry so arranged as to provide an air space within the wall between the inner and outer wythes. A cavity wall is built of masonry units or plain concrete, or a combination of these materials, arranged to provide an air space within the wall, which may be filled with insulation, and in which inner and outer wythes are tied together with metal ties. Hand Rod - A sewer rod that can be inserted manually (by hand) into a sewer to clear a stoppage or to prevent a stoppage from developing. Handhole Trap (water) - A device made of pipe fittings used to prevent sewer gases escaping from the branch or lateral sewer from entering a building sewer. Hard Water (water) - Water having a high concentration of calcium and magnesium ions. A water may be considered hard if it has a hardness greater than the typical hardness of water from the region Some textbooks define hard water as water with a hardness of more than 100 mg/L as calcium carbonate. •

G- 32

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GLOSSARY OF CIVIL ENGINEERING TERMS

Hardness, Water (water) - A characteristic of water caused mainly by the salts of calcium and magnesium, such as bicarbonate, carbonate, sulfate, chloride and nitrate. Excessive hardness in water is undeSirable because it causes the formation of soap curds, increased use of soap, deposition of scale in boilers, damage in some industrial processes, and sometimes causes objectionable tastes in drinking water. Head (water) - The vertical distance (in feet) equal to the pressure (in psi) at a specific point. The pressure head is equal to the pressure in psi times 2.31 ft/ psi. Head Loss (water) -The head, pressure or energy (they are the same) lost by water flowing in a pipe or channel as a result of turbulence caused by the velocity of the flowing water and the roughness of the pipe, channel walls, or restrictions caused by fittings. Water flowing in a pipe loses head, pressure or energy as a result of friction losses. The head loss through a filter is due to friction losses caused by material building up on the surface or in the top part of a filter. Also see FRICTION LOSSES. Header (Bonder) (const) - A brick or other masonry unit laid flat across a wall with end surface exposed, to bind to wythes. Header (water) - A large pipe to which a series of smaller pipes are connected. Also called a • MANIFOLD. Headroom (const) - Minimum dear height from a tread to overhead construction, such as the ceiling of the next floor, ductwork, or piping. Headworks (water) - The facilities where wastewater enters a wastewater treatment plant. The headworks may consist of bar screens, comminutors, a wet well and pumps. Health and Safety Control (const) - Work on site concerned with checking the fulfilltnent of health and safety project provisions. Health and Safety Management (const) - Work concerned with e~uring the fulfillment of health and safety requirements related to both general and local legislation during the design and construction stages. Health and Safety Planning (const) - Work taking into account health and safety aspects in the conception stages (i.e. briefing, designing, construction detailing, estimating, etc.) and planning health and safety aspects of the project. Hepatitis (water) - Hepatitis is an inflammation of the liver usually caused by an acute viral infection. Yellow jaundice is one symptom of hepatitis. Herbicide (water) - A compound, usually a manmade organic chemical, used to kill or control plant growth. Heterotrophic (water) - Describes organisms that use organic matter for energy and growth. Animals, fungi and most bacteria are heterotrophs. High-line Jumpers (water) - Pipes or hoses connected to fire hydrants and laid on top of the ground to provide emergency water service for an isolated portion of a distribution system. High-velocity Oeaner (water) - A machine designed to remove grease and debris from the smaller diameter sewer pipes with high-velocity jets of water. Also called a "jet cleaner," "jet rodder," "hydraulic cleaner,• "high-pressure cleaner," or "hydro jet." Honeycombing (canst)- usually used to refer to a defective condition in concrete. The concrete contains interconnecting large voids due to loss or lack of mortar Horizontal Clip Gauge - Sensc;lr that measures the width of concrete joint openings.

GLOSSARY QF,CIVIL ENGINEERING TERMS

G- 33

Hose Bib (water) - Faucet. A location in a water line where a hose is connected. Hot Tap (water) - Tapping into a sewer line Wlder pressure, such as a force main or a smalldiameter sewer Wlder pressure. Hub (water) - In pipe fitting, the enlarged female end of a pipe into which the male end fits. Also called a BELL Humus Sludge (water) - The sloughed particles of biomass from trickling filter media that are removed from the water being treated in secondary clarifiers. Hydrated Ume (water) - Umestone that has been "burned" and treated with water Wlder controlled conditions Wltil the calcium oxide portion has been converted to calcium hydroxide (Ca(OH)2). Hydrated lime is quicklime combined with water. CaO + H20 -> Ca(OH)2. Also called slaked lime. Also see QUICKLIME. Hydraulic Block (water) - The movement of water in such a way that the flow of water from one direction blocks or hinders the flow of water from another direction. Hydraulic Grade Line (HGL) (water) - The surface or profile of water flowing in an open channel or a pipe flowing partially full. If a pipe is Wlder pressure, the hydraulic grade line is at the level water would rise to in a small vertical tube connected to the pipe. Also see ENERGY GRADE LINE. Hydraulic Gradient (water) - The slope of the hydraulic grade line. This is the slope of the water surface in an open channel, the slope of the water surface of the grom1dwater table, or the slope of the water pressure for pipes Wlder pressure. Hydraulic Jump (water) - The sudden and usually turbulent abrupt rise in water surface in an open channel when water flowing at high velocity is suddenly retarded to a slow velocity. Hydraulic Loading (water) - Hydraulic loading refers to the flows (MGD or cu m/ day) to a treatment plant or treatment process. Detention times, surface loadings and weir overflow rates are directly influenced by flows. Hydrogeologist (water) - A person who studies and works With grom1dwater. Hydrologic Cycle (water) - The process of evaporation of water into the air and its return to earth by precipitation (rain or snow). This process also includes transpiration from plants, groWldwater movement, and runoff into rivers, streams and the ocean. Also called the WATER CYCLE. Hydrology (water) - The applied science concerned with the waters of the earth in all their states - their occurrence, distribution, and circulation through the Wlending hydrologic cycle of precipitation, consequent rWloff, stream flow, infiltration, and storage, eventual evaporation, and reprecipitation. Hydrology is concerned with the physical, chemical, and physiological reactions of water with the rest of the earth and its relation to the life of the earth. Hydrolysis (water) - A cherriical reaction in which a compound is converted into another compoWld by taking up water. 0 Usually a chemical degradation of organic matter. Hydrophilic (water) - Having a strong affinity (hking) for water. The opposite of HYDROPHOBIC. Hydrophobic (water) - Having a strong aversion (dislike) for water. The opposite of HYDROPHILIC. Hydropneumatic (water) - A water system, usually small, in which a water pump is automatically controlled (started and stopped) by the air pressure in a compressed air tank.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 31

Hydrostatic Pressure (water) - The pressure at a specific elevation exerted by a body of water at rest, or 0 In the case of groundwater, the pressure at a specific elevation due to the weight of water at higher levels in the same zone of saturation. Hydrostatic System (water) - In a hydrostatic sludge removal system, the surface of the water in the clarifier is higher than the surface of the water in the sludge well or hopper. This d,ifference in pressure head forces sludge from the bottom of the clarifier to flow through pipes to the sludge well or hopper. Hydroxide Precipitation (water) - A method of removing common metals from wastestreams by the precipitation process. The pH of the metal waste is increased to an optimum level for hydroxide metal precipitates to form for the wastes 'being treated. The metal precipitates are settled out of the wastestream in clarifiers and are removed from the bottom of the clarifiers as metal sludges. Hygroscopic (water) - Absorbing or attracting moisture from the air. Hypochlorination (water) - The application of hypochlorite compounds to water for the purpose.of disinfection.

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Hypochlorinators (water) - Chl()rine pumps, chemical feed pumps or devices used to d.ispense chlorine solutions made from hypochlorites such as bleach (sod.ium hypochlorite) or calcium hypochlorite into the water being treated. H.ypochlorite (water) - Chemical compounds containing available chlorine; used for disinfection They are available as liquids (bleach) or solids (powder, granules, and pellets) in barrels, drums, and cans. Salts of hypochlorous acid. Hypolimnion (water) - The lowest layer in a thermally stratified lake or reservoir. This layer consists ofcolder1 more dense water, has a constant temperature and no mixing occurs.

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I Imhoff Cone (water) - A clear, cone-shaped container marked with graduations. The cone is used to measure the volume of settleable solids in a specific volume (usually one liter) of water. Immiscible (water) - Not capable of being mixed. Impeller (water) - A rotating set of vanes in a pump or compressor designed to pump or move water or air. Impeller Pump (water) -Any pump in which the water is moved by the continuous application of power to a rotating set of varies from some rotating mechanical source. Impermeable (water) - Not easily penetrated. The property of a material or soil that does not allow, or allows only with great difficulty, the movement or passage of water. Imported Backfill (const) ~ Material used for backfilling a trench or excavation which was not the original material removed during excavation. This is a common practice where tests on the original material show it to have poor compactability or load capacity. Also called BORROW BACKFILL. Impurity (water) - A hazardous substance which is unintentionally present with another substance or mixture. (Definition from California Labor Code, Division 5, Chapter 2.5.) Inceneration (water) -The conversion of dewatered wastewater solids by combustion (burning) to ash, carbon dioxide, and water vapor.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 35

Indole (water) - An organic compound (CSH7N) containing nitrogen which has an ammonia odor. Industrial Wastewater (water}- Liquid wastes originating from industrial processing. Because industries have peculiar liquid waste characteristics r.equiring special consideration, these sources are usually handled and treated separately before being discharged to a wastewater collection system. Infiltrated Debris . (water) - Sand, silt, gravel and rocks carried or washed into a collection system by infiltration water flows. Infiltration (const) -Leakage into a material or structure; water ingress Infiltration (water) - The seepage of groundwater into a sewer system, including service connections. Seepage frequently occurs through defective or cracked pipes, pipe joints, connections or manhole walls. Infiltration Head (water) - The ·distance from a point of infiltration leaking into a collection system to the water table elevation. This is the pressure of the water being forced through the leak in the collection system. Infiltration/inflow (water) - The total quantity of water from both infiltration and inflow without distinguishing the source. Abbreviated I & I or 1/I. Inflatable Pipe Stopper (water) - An inflatable ball or bag used to form a plug to stop flows in a sewer pipe. Inflow (water) - Water discharged into a sewer system and service connections from sources other than regular connections. This includes flow from yard drains, foundation drains and around manhole covers. Inflow differs from infiltration in that it is a direct discharge into the sewer rather than a leak in the sewer itself. Influent (water) - Water or other liquid - raw (untreated) or partially treated - flowing INTO a reservoir, basin, treatment process, or treatment plant. Injector Water (water) - Service water in which chlorine is added (injected) to form a chlorine solution. Inlet (water) - A surface connection to a drain pipe. 0 A chamber for collecting storm water with no well below the outlet pipe for colle<;ting grit. Often connected to a CATCH BASIN or a "basin manhole" ("cleanout manhole") with a grit chamber. In-line Filtration (water) - The addition of chemical coagulants directly to the filter inlet pipe. The chemicals are mixed by the flowing water. Flocculation and sedimentation facilities are eliminated. This pretreatment method is commonly used in pressure filter installations. Also see CONVENTIONAL FILTRATION and·DIRECT FILTRATION. Inoculate (water) -To introduce a seed culture into a system Inorganic (water) - Material such as sand, salt, iron, calcium salts and other mineral materials. Inorganic substances are of mineral origin, whereas organic substances are usually of animal or plant origin Also see ORGANIC. Inorganic Waste (water)- Waste material such as sand, salt, iron, calcium, and other .mineral materials which are only slightly affected by the action of organisms. Inorganic wastes are chemical substances of mineral origin; whereas organic wastes are chemical substances of an animal or plant origin. Input Horsepower (water)- The total power used in operating a pump and motor. Insecticide (water) - Any substance or chemical formulated to kill or control insects.

G- 36

GLOSSARY OF CIVIL ENGINEERING TERMS

Insertion Puller (water) - A device used to pull long segments of flexible pipe material into a sewer line when slip lining to rehabilitate a deteriorated sewer. lnsituform (water) - A method of installing a new pipe within an old pipe without excavation. The process involves the use of a polyesterfiber felt tube, lined on one side with polyurethane and fully impregnated with a liquid thermal setting resin. Insoluble (water) -Something that cannot be dissolved. Integrity (const) - In Building Pathology: soundness, with no part or element deficient in performance Intercepting Sewer (water) - A sewer that receives flow from a number of other large sewers or outlets and .conducts the waters to a point for treatment or disposal. Often called an "interceptor." Interceptor (water) - A septic tank or other holding tank which serves as a temporary wastewater storage reservoir for a Septic Tank Effluent Pump (STEP) system. See SEPTIC TANK. Iaterconnector (water) - A sewer installed to connect two separate sewers. If one sewer becomes blocked,. wastewater can back up and flow through the inter-connector to the other sewer. Interface (water) - The common boundar; layer between two substances such as water and a solid (metal); or between two fluids such as water and a gas (air); or between a liquid (water) and another liquid (oil). Internal Flow (water) - Non-sanitary or industrial wastewaters generated inside of a domestic, commercial or industrial facility and being discharged into the sewer system. Examples are cooling tower waters, basement sump pump discharge waters, continuous flow drinking fountains, and defective or leaking plumbing fixtures.· Internal Friction (water) -Friction within a fluid (water) due to cohesive forces. Interstice (water) - A very small open space in a rock or granular material. Also called a PORE, VOID, or void space. Also see VOID. Interstitial (const) - Occurring within the thickness of some material element. usually used in the context of 'interstitial condensation' which means condensation which occurs within the thickness oi a building element or within its component materials Intrados (water) -The upper inside curve or surface of a sewer pipe or conduit. Inversion (water) - An Insituform process in which the Insitutube or liner is turned inside out (inverted) during the installation of the liner. Invert (water) -The lowest point of the channel inside a pipe, conduit, or canal. Inverted Siphon (water) - A pressure pipeline used to carry wastewater flowing in a gravity collection system under a depression such as a valley or roadway or under a structure such as a building. Also called a "depressed sewer." Ion (water)- An electrically charged atom, radical (such as S042-), or molecule formed by the loss or gain of one or more electrons. Ion Exchatlge (water) - A water treatment process involving the reversible interchange (switching) of ions between the water being treated and the solid resin. Undesirable ions in the water are switched with acceptable ions on the resin.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 37

Ion Exchange Resins (water)- Insoluble polymers, used m water treatment, that are capable of exchanging (switching or giving) acceptable cations or anions to the water being treated for less desirable ions. Ionic Concentr.ation (water) - The concentration of any ion in solution, usually expressed in moles per liter. Ionization (water)- The splitting or dissociation (separation) of molecules into negatively and positively charged ions. 0 The process of adding electrons to, or removing electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharge~, and nuclear radiation can cause ionization.

J, K, L Jacking force (const) - In prestressed concrete, temporary force exerted by device that introduces tension into prestressing tendons. Jamb (const) -Part of a frame that surrounds and contacts the window or door it supports. Jar Test (water) - A laboratory procedure that simulates a water treatment plant's coagulation/flocculation units with differing chemical doses and also energy of rapid mix, energy of slow mix, and settling time. The purpose of this procedure is to ESTIMATE the minimum or ideal coagulant dose required to achieve certain water quality goals. Samples of water to be treated are commonly placed in six jars. Various amounts of chemicals are added to each jar, stirred and the settling of solids is observed. The dose of chemicals that provides satisfactory settling, removal of turbidity and/ or color is the dose used to treat the water being taken into the plant at that time. When evaluating the results of a jar test, the operator should also consider the floc quality in the flocculation area and the floc loading on the filter. Jetsam (water)- Debris entering a collection system which is heavier than water. Also see GRIT. Joint (construction -, expansion -, control -) (const) - Position where two or more building materials, components or assemblies are put together, fixed or united, with or without the use of extra jointing products Joint (water) - A connection between two lengths of pipe, made either with or without the use of another part. Joule (phy) - A measure of energy, work or quantity of heat. One joule is the work done when the point of application of a force of one newton is displaced a distance of one meter in the direction of the force. Approximately equal to 0.7375 ft-lbs. Key Manhole (water) - In collection system evaluation, a key manhole is one from which reliable or specific data can be obtained. Kinetic Energy (water) - Energy possessed by a moving body of matter, such as water, as a result of its motion. · Kite (water) - A device for hydraulically cleaning sewer lines. Resembling an airport wind sock and constructed of canvas type material, the kite increases the velocity of a flow at its outlet to wash d!!bris ahead of it. Also called a PARACHUTE. Laminar (water) - Laminar flow is smooth or viscous flow; not turbulent flow.

G- 38

GLOSSARY OF CIVIL ENGINEERING TERMS

Lamp Hole (water) - A small yerhcal pipe or shaft extending from the surface of the groun~i to a sewer. A light (cr larripj may be lowered down the pipe for the purpose of inspecting the sewer. Rarely constructed today. Lamping (water) - Using reflected sunlight or a powerful light beam to inspect;{ sewer between two adjacent manholes. The light is directed down the pipe from one manhole. If it can be seen from the next manhole, it indicates that the line is open and straight. Langelier Index (L.I.) (water) - An index reflecting the equilibrium pH of a water with respect to calcium and alkalinity. This index is used in stabilizing water to control both corrosion and the deposition of scale. Langelier Index = pH - pHs, where: pH = actual pH of the water, and pHs= pH at which water having the same alkalinity and calcium content is just saturated with calcium carbonate. Lateral Break (water) - A break in a lateral pipe somewhere between the sewer,main and the building connection. Lateral Cleanout (water) - A capped opening in a building lateral, usually located on the property line, through which the pipelines can be cleaned. I..3teral Sewer (water) - A sewer that discharges into a branch or other sewer and has no other common sewer tributary to it. Sometimes called a "street sewer" because it collects wastewater from individual homes. Laundering Weir (water) -Sedimentation basin overflow weir. A plate with V-notches along the top to ensure a unifo~ flow rate and avoid short circuiting. Launders (water) - Sedimentation basin and filter discharge channels consisting of overflow weir plates (in sedimentation basins) and conveying troughs. Level Control (water)- A float device (or pressure switch) which senses changes in a measured variable and opens or closes a switch in response to that change. In its simplest form, this control might be a floating ball connected mechanically to a switch or valve such as is used to stop water flow into a toilet when the tank is full . Lift (water) -Vertical distance water is lifted from upstream water surface up to downstream water surface (which is at a higher elevation). Lift Station (water) - A wastewater pumping station that lifts the wastewater to a higher elevation when continuing the sewer at reasonable slopes would involve excessive depths of trench. Also, an installation of pumps that raise wastewater from areas too low to drain into available sewers. These stations may be equipped with air-operated ejectors or centrifugal pumps. Sometimes called a PUMP STATION, but this term is usually reserved for a similar type of facility that is discharging into a long FORCE MAIN, while a lift station has a discharge _line or force main only up to the downstream gravity sewer. Throughout this manual when we refer to lift stations, we intend to include pump stations. Limit state (const)- State at which performance criteria are just met Lindane (water) - A pesticide that causes adverse health effects in domestic water supplies and also is toxic to fre~hwater and marine aquatic life. Lipophilic (water) - Having a strong affinity for fats. Compounds that dissolve in fats, oils and greases. Liquefaction (water) - The conversion of large solid particles of sludge into very fine particles which either dissolve or remain suspended in wastewater.

GLOSSARY OF CIVIL ENGINEE~ING TERMS

G- 39

Liquid Vehicle (water) - Water in a collection system that is used to carry waste solids. The standard toilet provides around seven gallons of water per flush as a vehicle to carry wastes through the pipe system. Liquor (water) - Water, wastewater, or any combination; commonly used to mean the liquid portion when other wastes are also present. Littorai .Zone (water) - That portion of a body of fresh water extending from the shoreline lakeward to the limit of occupancy of rooted plants. 0 The strip of land along the shoreline between the high and low water levels. Load, dead (const) - Dead weight supported by a member, as defined by NSLP of which this chapter/code forms a part (without load factors). Load, factored (const) - Load multiplied by appropriate by appropriate load factors, used to proportion members by the strength design method of this chapter. Local Authority, Environment and Control of Construction Plans (const) -The fulfillment of statutory requirements regarding construction standards, safety and . approval of construction projects and their effett on the environment. Loss (const)- Consequences of a defect or failure, expressed in terms of costs, injuries, loss of life, etc. Lqwer Flamable Limit (LFL) (water) - The lowest concentration of a gas or vapor (percent by volume in air) that bums if an ignition source is present. Lump Sum Contract (const)- With a lump sum contract, the contractor agrees to perform the work for one fixed price, regardless of the ultimate cost. Lump Sum Tender (const)- A tender at a fixed price to which a contractor undertakes to carry out all the work specified on the drawings and in the contract documents. Lysimeter (water) - A device containing a mass of soil and designed to permit the measurement of water draining through the soil.

M M or Molar (water) - A molar solution consists of one gram molecular weight of a compound dissolved in enough water to make one liter of solution. A gram molecular weight is the molecular weight of a compound in grams. For example, the molecular weight of sulfuric add (H2S04) is 98. A one M solution of sulfuric acid would consist of 98 grams of H2S04 dissolved in enough distilled water to make one liter of solution. Macronutrient (water) - A chemical element of which relatively large quantities are essential for the growth of an organism. Macroscopic Organisms (water) - Organisms big enough to be seen by the eye without the aid of a microscope. Mail Line (water) - Branch or lateral sewers that collect wastewater from building sewers and service lines. Main Sewer (water) - A sewer line that receives wastewater from many tributary branches and sewer lines and serves as an outlet for a large territory or is used to feed an intercepting sewer.

G- 40

GLOSSARY OF CIVIL ENGINEERING TERMS

Maintenance (const)- Combination of any actions carried out to retain an item in, or restore it to, an acceptable condition. J' Maintenance Management (const)- Preparing ongoing programs for the planned maintenance of constructions and managing the implementation of these works. Maintenance Projects (const) - Ongoing repair and maintenance of existing constructions increasingly being incorporated within the broader activity of facilities management. Management (const)- Effective utilization and co-ordination of resources such as capital, plant, materials, and labor to achieve defined objectives with maximum efficiency. Management Contract (const) - This is a· contract in which management is regarded as a separate discipline and responsibility from that of construction. Construction (works) contractors contract with a management contractor, who is there-fore their· client or employer. Management Contracting (const)- Is the method of carrying out a construction project whereby a contractor is appointed at the pre-construction stage and paid on a fee basis, to manage and deliver the project. The fee comprises a percentage for profit and fixed overheads. All construction work is carried out by the sub-contractors, selected and appointed in consultation with the client and his professional advisers. Management Contractor (const) - The ~nanagement contractor is appointed by the client to work alongside the design and cost consultants, providing a construction management service on a number of professional bases. The management contractor does not undertake either design or direct construction work. The design requirements are met by letting each element of the construction to specialist sub-contractor. Management Fee (const)- An agreed sum for management services. Management Information (const)- Information for management deci;ion-making. Management of Construction (const) - Embraces all those job functions necessary to plan, control and co-ordinate the design, execution and long term care of construction projects. Management Style (const) - Approach adopted by managers in exerCismg authority, encouraging participation in decision-making, motivating staff, delegating authority, communication information and maintaining control. Management Technique (const) - A means used by managers, to define and assist with the solution of a problem. Manager (const) - A person responsible for directing and running an organization or project. Manhole (water) - An opening in a sewer provided for the purpose of permitting operators or equipment to enter or leave a sewer. Sometimes called an "access hole" or a "maintenance hole." Manhole Bedding (water) - The prepared and compacted base on which a manhole is constructed. Manhole Depth (water) - The measurement from the top of the manhole opening to the invert or lowest point of the trough at the bottom of the manhole. Manhole Vents (water)- One or a series of one-inch diameter holes through a manhole lid for purposes of venting dangerous gases found in sewers. Manifold (water) -A large pipe to which a series of smaller pipes are connected. Also called a HEADER.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 41

Manometer (water)- An instrument for measuring pressure. Usually, a manometer is a glass tube filled with a liquid that is used to measure the difference in pressure across a flow measuring device such as an orifice or a Venturi meter. The instrument used to measure blood pressure is a type of manometer. Masonry (const) - A built-up construction or combination of masonry units, such as day brick, concrete block, or stone, bonded together with mortar or other cementitious material. Masonry (const) - The science, art, craft and trade of building in natural or artificial stone. The term is often extended to work in brick and tile. Ancient examples of immense. irregular blocks of stone, laid together without mortar, have been found throughout Europe, Americas, Africa, and Asia. The ancient Greeks and Romans developed masonry techniques that are still used today. Rubble masonry uses irregular and coarsely jointed quarried or field stone. Ashlar masonry contains carefully worked stones set with fine, close joints. Either kind of masonry may be laid with or without mortar Materials management (const)- The creation of conditions to bring about the optimum use of all materials available for the construction of a project to ensure availability at the right time and control of inventory. Mean Cell Residence Time (MCRT) (water) - An expression of the average time that a microorganism will spend in the activated sludge process. MCRT, days= Total Suspended Solids in Activated Sludge Process, lbs/Total Suspended Solids Removed From Process, lbs/day Mechanical Aeration (water) -The use of machinery to mix air and water so that oxygen can be absorbed into the water. Some examples are: paddle wheels, mixers, or rotating brushes to agitate the surface of an aeration tank; pumps to create fountains; and pumps to discharge water down a series of steps forming falls or cascades. Media (water) - The material in a trickling filter on which slime accumulates and organisms grow. As settled wastewater trickles over the media, organisms in the slime remove certain types of wastes thereby partially treating the wastewater. Also the material in a rotating biological contactor or in a gravity or pressure filter. Meniscus (water) - The curved surface of a column of liquid (water, oil; mercury) in a small tube. When the liquid wets the sides of the container (as with water), the curve forms a valley. When the confining sides are not wetted (as with mercury), the curve forms a hill or upward bulge. · Mesh (water) - One of the openings or spaces in a screen or woven fabric. The value of the mesh is usually given as the number of openings per inch. This value does not consider the diameter of the. wire or fabric; therefore, the mesh number does not always have a definite relationship to the size of the hole. Mesophilic Bacteria (water) - Medium temperature bacteria. A group of bacteria that grow and thrive in a moderate temperature range between 68°F (20•q and 113•F (4s•q. The optimum temperature range for these bacteria in anaerobic digestion is ss•F (30"C) to 1oo•F (38•q. Mesotrophic (water) - Reservoirs and lakes which contain moderate quantities of nutrients and are moderately productive in terms of Metabolism (water) - The biochemical processes in which food is used and wastes are formed by living organisms. 0 All biochemical reactions involved in cell formation and growth. 2: All of the processes or chemical changes in an organism or a single cell by which food is built up (anabolism) into living protoplasm and by which protoplasm is broken down (catabolism) into simpler compounds with the exchange of energy.

GLOSSARY OF CIVIL ENGINEERING TERMS

G -42

Metalimnion (water) - The middle layer.in a ~~rmally stratified lake or reservoir. In this layer there is a rapid decrease in temperature with depth. Also called the THERMOCLINE. Method Statement (const) - A statement of the construction methods and resources to be employed in executing construction work. The statement is normally closely linked to the tender program. Methoxychlor (water) - A pesticide which causes adverse health effects in domestic water supplies and is also toxic to freshwater and marine aquatic life. The chemical name for methoxychlor is 2,2bis (pmethoxyphenol)l,l,ltrichloroethane. Methyl Orange Alkalinity (water) - A measure of the total alkalinity in a water sample. The alkalinity is measured by the amount of standard sulfuric acid required to lower the pH of the water to a pH level of 4.5, as indicated by the change in color of methyl orange from orange to pink. Methyl orange alkalinity is expressed as milligrams per liter equivalent calcium carbonate. MG (water)- Initials for "Million Gallons." M_GD (water)- Initials for "Million Gallons Per Day." MGY (water)- Initials for "Million Gallons Per Year." Microbial Growth (water) - The activity and growth of microorganisms such as bacteria, algae, diatoms, plankton and fungi. · Micron (gen) - J.lm, Micrometer or Micron. A unit of length. One millionth of a meter or one thousandth of a millimeter. One micron equals 0.00004 of an inch . . Micronutrient (water) - A trace element or an organic compound which is essential in tiny amounts for the growth of organism.

an

Microorganisms (water) - Uving organisms that can be seen individ'ually only with the aid of a microscope. D Very small organisms that can be seen only through a microscope. Some microorganisms use the wastes in wastewater for food and thus remove or alter much of the undesirable matter. Microscreen (water) - A device with a fabric straining media with openings usually between 20 and 60 microns. The fabric is wrapped around the outside of a rotating drum. Wastewater enters the open end of the drum and flows out through the rotating screen cloth. At the highest point oJ the drum, the collected solids are backwashed by high-pressure water jets into a trough located within the drum. Mil (gen) - A unit of length equal to 0.001 of an inch. The diameter of wires and tubing is measured in mils, as is the thickness of plastic sheeting. Mildew (const) -Mold whenever it occurs on fabrics, leather, etc. Millimicron (gen) - A unit of length equal to 10-3J.1 (one thousandth of a micron), 10-6 millimeters, or l0-9meters; correctly called a nanometer, nm. Mineral (water) - Any substance that is neither animal nor plant. Minerals include sand, salt, iron, calciWll. and nutrients. Miscible (water) " Capable of being mixed. A liquid, solid, or gas that can be completely dissolved in water. Mixed Uquor (water) - When the activated sludge in an aeration tank is mixed with primary effluent or the raw wastewater and return sludge, this mixture is then referred to as mixed liquor as long as it is in the aeration tank. Mixed liquor also may refer to the contents of mixed aerobic or anaerobic digesters.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 43

Mixed Liquor Suspended Solids (MLSS) (water) - Suspended solids in the mixed liquor of an aeration tank. Mixed Liquor Volatile Suspended Solids (MLVSS) (water)- The organic or volatile suspended solids in the mixed liquor of an aeration tank. This volatile portion is used as a measure or indication of the microorganisms present. MLSS (water) - Mixed Liquor Suspended Solids, mg/L. Suspended solids in the mixed liquor of an aeration tank. MLVSS (water) - Mixed Liquor Volatile Suspended Solids, mg/L. The organic or volatile suspended solids in the mixed liquor of an aeration tank. This volatile portion is used as a measure or indication of the microorganisms present. Modulus of elastidty (const) - Ratio of ~ormal stress to corresponding strain for tensile or compressive stresses below proportional limit of material. Mold (const) - Woolly or powdery fungal growth that forms on the surface of materials in damp, stagnant atmospheres Monomictic (water) - Lakes and reservoirs which are relatively deep, do not freeze over during the winter months, and undergo a single stratification and mixing cycle during the year. These lakes and reservoirs usually become destratified during the mixing cycle, usually in the fall of the year. Mortar (const) - A plastic mixture cementitious materials, fine aggregates, and water. 0 Mixture of lime and/ or cement with sand and water, used either as a binding material for bricks and stone or as a plaster Motile (water) - Capable of self-propelled movement. A term that is sometimes used to distinguish between certain types of organisms found in water. MPN (water) - MPN is the Most Probable Number of coliform group organisms per unit volume of sample water. Expressed as a density or population oforganisms per 100 mL of sample water. Mudballs (water) - Material that is approximately round in shape and varies from peasized up to two or more inches in diameter. This material forms in filters and gradUiilly increases in size when not removed by the backwashing process. Multi-stage Pump (water) - A pump that has more than one impeller. A single stage pump has one impeller. Muntin (const) - A short light bar. Mutagenic (water) - Any substance which tends to cause mutations or gene changes prior to conception.

G -41

GLOSSARY OF CIVIL ENGINEERING TERMS

N Nappe (water) - The sheet or curtain of water flowing over a weir or dam. When the water freely flows over any structure, it has a well defined upper and lower water surface. Negotiated Contract (const) - In a negotiated contract the client selects, at the outset, one main contractor with whom to negotiate. In essence the arrangement is the same as that for a two-stage tender. · Net Wastewater Contribution (water) - In a wastewater collection system, the net wastewater contribution consists of the liquid wastes and liquid carried wastes transported by the pipelines or received by the pipelines. This value would be the only wastewater found in a collection system if all sources of infiltration, inflow and exfiltration were eliminated. Net Wastewater Flow (water) - The actual wastewater flow from a collection system that reaches a wastewater treatment plant. The net wastewater flow includes the net wastewater contribution, infiltration and inflow and does not include losses through exfiltration. Neutralization (water)- Addition of an add or alkali (base) to a liquid to cause the pH of the liquid to move toward a neutral pH of 7.0. Newel Post (const) -Post at which the railing terminates at each floor level. ·Nitrification (water) - An aerobic process in which bacteria reduce the ammonia and organic nitrogen in water into nitrite and then nitrate. · Nitrification Stage (water) - A stage of decomposition that occurs in biological treatment processes when aerobic bacteria, using dissolved oxygen, change nitrogen compounds (ammonia and organic nitrogen) into oxidized nitrogen (usually nitrate). The second-stage BOD is sometimes referred to as the "nitrification stage" (first-stage BOD is called the "carbonaceous stage"). Nitrifying Bacteria (water) - Bacteria that change the ammonia and organic nitrogen in wastewater into oxidized nitrogen (usually nitrate). Nitrogenous (water) - A term used to describe chemical compounds (usually organic) containing nitr~gen in combined forms. Proteins and nitrate are nitrogenous compowtds. NOM (Natural Organic Matter) (water) - Hwnic substances composed of hwnic and fulvic adds that come from decayed vegetation. Nonbearing Wall (const) - A wall that supports no vertical load other than its own weight. Nonbiodegradable (water) - Substances that cannot readily be broken down by bacteria to simpler forms. · Noncompatible Pollutants (water) - Those pollutants which are normally NOT removed by the POTW treatment system. These pollutants may be a toxic waste and may pass through the POTW untreated or interfere with the treatment system. Examples of non-compatible pollutants include heavy metals such as copper, ¢ckel, lead, and zinc; organics such as methylene chloride, l,l,ltrichloroethylene, methyl ethyl ketone, acetone, and gasoline; or sludges containing toxic organics or metals. Nonpoint SOurce (water) - A runoff or discharge from a field or similar source. A point source refers to a discharge that comes out the end of a pipe. Nonpotable (water) • Water that may contain objectionable pollution, contamination, minerals, or infective agents and is considered unsafe and/ or unpalatable for drinking.

GLOSSARY OF CIVIL ENGINEERING TERMS

G -45

Nonvolatile Matter (water) - Material such as sand, salt, iron, calcitun_ and other mineral materials which are only slightly affected by the actions of organiSms and are not l<>st on

ignition of the dry solids at sso•c. Volatile materials are chemical substances usually of animal or plant origin. Also see INORGANIC WASTE and VOLATILE MATIER or VOLATILE SOUDS.

Nosing·(const)- Projection of a tread beyond the riser below. Novation (const) - A hybrid variation of design & build procurement where the client appoints a designer (architect) to develop a concept design and passes on that designer to the contractor. Nutrient (water) - Any substance that is assimilated (taken in) by organisms and promotes growth. Nitrogen and phosphorus are nutrients which promote the growth of algae. There are other essential and trace elements which are also considered nutrients. Nutrient Cycle (water) - The transformation or change of a nutrient from one form to another 1fntil the nutrient has returned to the original form, thus completing the cycle. The cycle may take place under either aerobic or anaerobic conditions.

0 0 R P (water) .,. Oxidation Reduction Potential. The electrical potential required to transfer electrons from one compound or element (the oxidant) to another compound or element (the reductant); used as a qualitative measure of the state of oxidation in water treatment systems. ORP is measured in millivolts, with negative values indicating a tendency to reduce compounds or elements and positive values indicating a tendency to oxidize compounds or elements. Obligate Aerobes (water) - Bacteria that must have atmospheric or dissolved molecular oxygen to live and reproduce. Olfactometer (water) - A device used to measure odors in the field by diluting odors with odorfree air. Olfactory Fatigue (water) - A condition in. which a person's nose, after exposure to certain odors, is no longer able to detect the odor. Oligotrophic (water) - Reservoirs and lakes which are nutrient poor and contain little aquatic plant or animal life. ~

Open Standpipe Pipe (water) - That has been plllfed vertically into the ground to measure the water table level. , Open Tender (const) -A tender received a result

of~dvertising for competiti~e tender.

Organic (water) - Substances that come from ani'mal or plant sources. Organic substances always contain carbon. (Inorganic materials chemical substances of mineral origin.) Also see INORGANIC. Organic Waste (water) - Waste material which com mainly from animal or plant sources. Organic wastes generally can be consumed by cteria and other small organisms. Inorganic wastes are chemical substances of mineral · "gin. Organism (water) - Any form of animal or plant life. Also Orifice (water) - An opening (hole) in a plate, wall, or p tition. An orifice flange or plate placed in a pipe consists of a · slot or a calibrated · ular hole smaller than the pipe

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GLOSSARY OF CIVIL ENGINEERING TERMS

diameter. The difference in pressure in the pipe above and at the orifice may be used to determine the flow in the pipe. Orthotolidine (water)- Orthotolidine is a colorimetric indicator of chlorine residual. If chlorine is present, ·a yellow-colored compound is produced. This reagent is no longer approved for chemical analysis to determine chlorine residual. •

Osmosis (water) -The passage of a liquid from a weak solution to a more concentrated solution across a semi-permeable membrane. The membrane allows the passage of the water (solvent) but not the dissolved solids (solutes). This process tends to equalize the conditions on either side of the membrane. Outfall (water) - The point, location or structure where wastewater or drainage discharges from a sewer, drain, or other conduit. 0 The conduit leading to the final disposal point or area. Outfall Sewer (water) - A sewer that receives wastewater from a collection system or from a wastewater treatment plant and carries it to a point of ultimate or final discharge in the environment. See OUTFALL. Outlet (water) - Downstream opening or discharge end of a pipe, culvert, or canal. Overall Effidency, Pump (water) - The combined effidency of a pump and motor together. . Also called the WIRETOWATER EFFICIENCY. Overdraft (water) -The pumping of water from a groundwater basin or aquifer in excess of the supply flowing into the basin. This pumping results in a depletion or "rniniilg" of the groundwater in the basin. Overflow Manhole.(water) - A manhole which fills and allows raw wastewater to flow out onto the street or ground. Overturn (water) - The almost spontaneous mixing of all layers of water in a reservoir or lake when the water temperature becomes similar from top to bottom. This may occur in the fall/winter when the surface waters cool to the same temperature as the bottom waters and also in the spring when the surface waters warm after the ice melts. Owner (const) -See Client or Employer Oxidation (water) - qxidation is the addition of oxygen, removal of hydrogen, or the removal . of electrons from an element or compound. 'n the environment, organic matter is oxidized to more stable substances. The opposite of ~EDUCTION . Oxidation Ditch (water) - The oxidation di~h is a modified form of the activated sludge process. The ditch consists of two chann~ls placed side by side and connected at the ends to produce one continuoqs loop of wasyewater flow and a brush rotator assembly placed across the channel to provide aeration d circulation. Oxidation-Reduction Potential (ORP) (wa er) - The electrical potential required to transfer electrons from one compound or ele ent (the oxidant) to another compound or element (the reductant); used as a qualitativ measure of the state of oxidation in water treatment systems. ORP is measured in · .: olts, with negative values indicating a tendency to reduce compounds or elements d positive values indicating a tendency to oxidize compounds or elements. · Oxidized Organics (water) - Organi materials that have been, broken down in a biological process. Examples of these mat rials are carbohydrates and proteins that are broken down to simple sugars.

OLOSIAAY OF CML ENGINEERING TERMS

G- 47

Oxidizing Agent (water) - Any substance, such as oxygen (02) or chlorine (Cl2), that will readily add (take on) electrons. The opposite is a REDUCING AGEN;f. Oxygen Defidency (water) - An atmosphere containing oxygen at a concentration of less than 19.5 percent by volume. Oxygen Enrichment (water) - An atmosphere containing oxygen at a concentration/of more than 23.5 percent by volume. Ozonation (water) - The application of ozone to water for disinfection or for taste and odor control.

p Palatable (water)- Water ~t a:,desirable temperature that is free from objectionable tastes, odors, colors, and turbidity. Pie sing to the senses. Parachute (water) - A device used to catch wastewater flow to pull a float line between manholes. See FLOAT LI Parasitic Bacteria (water)- Paras1 ·c bacteria are those bacteria which normally live off another "host." living organism, known as Parghall Flume (water) - A device used to measure the flow in an open charmel. The flume narrows to a throat of fixed di ensions and then expands again. The rate of flow can be calculated by measuring the di erence in head (pressure) before and at the throat of the flume. Particulate (water) - A very small so d suspended in water which can vary widely in size, shape, density, and electrical cha e. Colloidal and dispersed particulates are artifidally gathered together by the processes f coagulation and flocculation. Partition (const) - An interior wall one sto or less in height. Parts Per Million (PPM) (water) - Parts pe million parts, a measurement of concentration on a ivalent to milligrains per liter (mg/L) which is the weight or volume basis. This term is preferred term. Party Wall (const) - A wall on an interior I buildings.

line used or adapted for joint service for two

Pathogenic Organisins (water) - Organisms, i luding bacteria, viruses or cysts, capable of causing diseases (giardiasis, cryptosporidio ·s, typhoid, cholera, dysentery) in a host (such as a person). There are many types of org nisins which do NOT cause disease. These orgar!isms are called nonpathogenic. Pathogens (water) - Pathogenic or disea~ausing o anisms. Pave Tech Van Vehicle (const) -With three cameras ·at record video images of the pavement surface, pavement profile, rutting and faul · . Performance (Fr.: Performance). A quantitative expression of behavior related to use. · · Peaking Factor (water) - Ratio of a maximum flow to · e average flow, such as maximum hourly flow or maximum daily flow to the average, ·· y flow. Pedestal (const)- Upright compression member with a ra least lateral dimensions of less than 3.

of unsupported height to average

G -48

GLOSSARY OF CIVIL ENGINEERING TERMS

Percolating Water (water)- Water that passes through soil or rocks under the force of gravity. Percolation (water) - The slow passage of water through a filter medium; or, the gradual penetration of soil and rocks by water. Periphyton (water) - Microscopic plants and animals that are firmly attached to solid surfaces . under water such as rocks, logs, pilings and other strUctures. Permeability (soil) - The property of a material or soil that permits considerable movement of water through it when it is saturated. ~

Permeate (water) - To penetrate and pass through, as water penetrates and passes through soil and other porous materials. 0 The liquid (demineralized water) produced from the reverse osmosis process that contains a WW concentration of dissolved solids. Pet Cock (water)- A small valve or faucet used to drain a cylinder or fitting. pH (water) - pH is an expression of the intensity of the basic or acidic condition of a liquid. Mathematically, pH is the ·logarithm (base 10) of the reciprocal of the hydrogen ion activity. The pH may range from 0 to 14, where 0 is most acidic, 14 most basic, and 7 • neutral. Natural waters usually have a pH between 6.5 and -.5.

I

pH Test Paper (water) - A strip of paper which is treated with ~veral dyes that change color at narrow and different pH ranges. To determine the pH a solution, place a drop of the solution on the test paper. Then compare the color that velops with the colors on a chart which relates color to pH Also see LITMUS PAPER. Phen.o l (water) - An organic compound that is a derivative Phenolic Compounds (water) -Organic compounds that a

derivatives of benzene.

ter sample.measured by the amount Phenolphthalein Alkalinity (water)- The alkalinity in a of standard acid required to lower the pH to a lev of 8.3, as indicated by the change in color of phenolphthalein from pink to clear. Phe olphthalein alkalinity is expressed as milligrams per liter of equivalent calcium carbona e. Photosynthesis (water) - A process in which organis , with the aid of chlorophyll (green plant enzyme), convert carbon dioxide and inorg · substances into oxygen and additional plant material, using sunlight for energy. All en plants grow by this process. Physical Wastewater Process (water) - Physical w te treatment processes include use of racks, screens, comminutors, clarifiers (sedimenta n and flotation) and filtration. Chemical or biological reactions are important trea nt processes, but NOT part of a physical treatment process. Phytoplankton (water) - Small, usually micr scopic plants (such as algae), found in lakes, reservoirs, and other bodies of water. Pico (gen) - A prefix used in the metric sy em and other scientific systems of measurement which means 10-12 or 0.000000000 00 Picocurie (water) - A measure of radioac · ity. One pico Curie of radioactivity is equivalent to 0.037 nuclear disintegrations per sec d. Pier (const) - An isolated column of sonry. A bearing wall not bonded at the sides into associated masonry is considered pier when its horizontal dimension measured at right angles tO the thickness does not ceed four times its thickness. Piezo Accelerometer Sensor (const) That measures the vertical acceleration of concrete slabs under dynamic lbadings. The suiting data, when integrated twice, yields deflections

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 49

Piezometer (water) - An instrument used to measure the pressure head in a pipe, tank, or soil. It usually consists. of a small pipe or tube connected or tapped into the side or wall of ~ pipe or tank and connected to a manometer pressure gage, water or mercury column, or other device for indicating pressure head. · Pilaster (const) - A bonded or keyed column of masonry built as a part of a wall and of uniform thickness throughout its height. It serves as a vertical beam, column, or both. Pipe Liner (water) - A plastic liner pulled or pushed into a pipe to eliminate excessive infiltration or exfiltration. Other solutions to the problem of infiltration/ exfiltration are the use of cement grouting or replacement of damaged pipe. Pitot Tube (water) - An instrument used to measure fluid (liquid or air) velocity by means of the differential pressure between the tip (dynamic) and side (static) openings. Plain concrete (canst) -Concrete that does not conform to definition of reinforced concrete. Plain reinforcement (canst) - Reinforcement that does not conform to definition of deformed reinforcement. Plankton (water) - 1. Small, usually microscopic, plants (phytoplankton) and animals (zooplankton) in aquatic systems. Planning (const) - The process of establishing the sequence and relationship of a series of operations prior to construction work commencing, Pollutant (water)- Any substance which causes an impairment (reduction) of water quality to a degree that has an adverse effect on any beneficial use of the water. Pollution (water) - The impairment (reduction) of water quality by agricultural, domestic, or industrial wastes (including thermal and radioactive wastes) to a degree that has an adverse effect on any beneficial use of water. Polychlorinated Biphenyls (water) - A class of organic compounds that cause adverse health effects in domestic water supplies. Polymer (water) - A long chain molecule formed by the union 9f many monomers (molecules of lower molecular weight). Polymers are used with other chemical coagulants to aid in binding small suspended particles to larger chemical floes for their removal from water. Ponding (water) - A condition occurring on trickling filters when the hollow spaces (voids) become plugged to the extent that water passage through the filter is inadequate. Ponding may be the result of excessive slime growths, trash, or media breakdown. Porcupine (water) - A sewer cleaning tool the same diameter as the pipe being cleaned. The tool is a steel cylinder having solid ends with eyes cast in them to which a cable can be attached and pulled by a winch. Many short pieces of cable or bristles protrude from the cylinder to form a round brush. Pore (soil) - A very small open space in a rock or granular material. Also called an INTERSTICE, VOID, or void space. Also see VOID. Pore Water Pressure Gauge Sensors (canst) -That measure static and dynamic soil pore water pressures using two different models Porosity (soil) - A measure of the spaces or voids in a material or aquifer. 0 The ratio of the volume of spaces in a rock or soil to the total volume. This ratio is usually expressed as a percentage. Positive Pressure. (water) - A positive pressure is a pressure greater than atmospheric. It is measured as pounds per square inch (psi) or as inches of water column. A negative

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GLOSSARY OF CIVIL ENGINEERING TERMS

pressure (vacuum) is less than ahnospheric and is sometimes measured in inches of mercury. In the metric system pressures are measured in kg/ sq m, kg/ sq em or pascals (1 psi = 6,895 Pa = 6.895 kNI sq m). Postchlorination (water) - The addition of chlorine to the plant effluent, FOLLOWING plant treatment, for disinfection purposes. Post-tensioning (const) - Method of prestressing in which tendons are tensioned after concrete · has hardened. Potable Water (water) - Water that does not contain objectionable pollution, contamination, minerals, or infective agents and is considered satisfactory for drinking.

\.

PPM (water) - Initials for "Parts Per Million." The number of weight or volume units of a minor constituent present with each one million units of the major constituent of a solution or mixture. Used to express the results of most water and wastewater analyses, but more recently milligrams per liter (mg/L) is the preferred term. Pre-Aeration (water) - The addition of air at the initial stages of treahnent to freshen the • wastewater, remove gases, add oxygen, promote flotation of grease, and aid coagulation. Precast concrete (const) - Plain or reinforced concrete element casf elsewhere than its final position in the structure. Prechlorination (water) - The addition of chlorine at the headworks of the plant PRIOR TO other treahnent processes mainly for disinfection and control of tastes, odors, and aquatic growths. Also applied to aid in coagulation and settling. Precipitate (water) - An insoluble, finely divided substance which is a product of a chemical reaction within a liquid. D The separation from solution of an insoluble substance. Precipitation (water) - The process by which ahnospheric moisture ialls onto a land or water surface as rain, snow, hail, or other forms of moisture. D The chemical transformation of a substance in solution into an insoluble form (precipitate). Precursor (water) - Natural organic compounds found in all surface and groundwaters. These compounds MAY react with halogens (such as chlorine) to •form trihalomethanes (triHALoMETHhanes) (THMs); they MUST be present in order for THMs to form. Prescriptive (water)- Water rights which are acquired by diverting water and putting it to use in accordance wl.th specified procedures. These procedures include filing a request (with a state agency) to use unused water in a stream, river or lake. Preservation (const) - The technology of protecting wood from deterioration by living organisms by application of chemical wood preservatives Pressure H~ad (water) - The vertical distance (in feet) equal to the pressure (in psi) at a specific point. The pressure head is equal to the pressure in psi times 2.31 ft/psi. Prestressed concrete (const) - Reinforced concrete in which internal stresses have been introduced to reduce potential tensile stresses in concrete resulting from loads. Pretensioning (const) - Method of prestressing in which tendons are tensioned before concrete is placed. Procurement (const) - Procurement is ' the amalgam of activities undertaken by the client to obtain
GLOSSARY OF CIVIL ENGINEERING TERMS

G- 51

treatment plant and is ready to be delivered to the consumers. Also called FINISHED WATER Professional Constructor (const) - Responsible master of that discipline which comprises the whole of the construction process as well as the essential parts thereof; possessing such skills founded on knowledge acquired through prescribed education and refined by experience, or earned equivalently as a recognized practitioner; who initiates, develops, produces or delivers, in whole or essential part, construction works at prices, times, and standards of quality which assures advantage to clients and society as a whole. Progress Analysis (const) - Breakdown of a project in identifiable components so that it is possible to control the process of construction. Progress Control (const) -The process of measuring actual progress against predicted planning and scheduling. Project (const) - Combination of activities of different specialized groups, directed at a nonrpetitive result with a clear beginning and end. Project Brief (const) - The project embodiment of the selected option for the fulfillment of a stated requirement for a facility or works. Project Documentation (const) - Systematic arrangement of information about a project during the course of the process. Project Management (const) - Project management is concerned with the overall planning and co-ordination of a project from inception to completion aimed at meeting the client's requirements and ensuring completion on time, within cost and to required quality standards. Project management is typically carried out either by a private consultant or an employee of the project client. Project Manager (const) - The person or firm appointed by the Client responsible for the planning, co-ordination and controlling of a project from inception to completion, meeting the client's requirements and ensuring completion on time, within cost and to required quality standards. Project Supervision (const) - Supervision and approval of the work of suppliers and other organizations working on site, typically carried out either by a private consultant or an employee of the client. Protoplasm (water) - A complex substance (typically colorless and semi-fluid) regarded as the physical basis of life, having the power. of spontaneous motion and reproduction; the living matter of all plant and animal cells and tissues. Protozoa (water) - A group of motile microscopic organisms (usually single-celled and aerobic) that sometimes cluster into colonies and often consume bacteria as an energy source. Psychrophilic Bacteria (water) - Cold temperature bacteria. A group of bacteria that grow and thrive in temperatures below 68°F (20°C) . . Pump (water) - A mechanical device for causing flow, for raising or lifting water or other fluid, or for applying pressure to fluids. Pump Station (water) - Installation of pumps to lift wastewater to a higher elevation in places where flat land would require excessively deep sewer trenches. Also used to raise wastewater from areas too low to drain into available collection lines. These stations may be equipped with air operated ejectors or centrifugal pumps. See LifT STATION. Pumping Water Level (water) - The vertical distance in feet from the centerline 'of the pump discharge to the level of the free pool while water is being drawn from the pool.

G ·52

GLOSSARY OF CIVIL ENGINEERING TERMS

Purge (water) - To remove a gas or vapor from a vessel, reactor or confined space, usually by displacement or dilution. Putrefaction (water)- Biological decomposition of organic matter, with the production of foul smelling and -tasting products, associated with anaerobic (no oxygen present) conditions. Putrescible (water) - Material that will decompose under anaerobic conditions and produce nuisance odors. Pyrometer (water) - An apparatus used to measure high temperatures.

Q,R Quality Control (canst) - Work undertaken by contractor, client's representative or, possibly, insurance company to ensure the quality of materials and work on site is in accordance wfth the agreed specifications and accepted standards. R A.S (water) - Return Activated Sludge, mg/L. Settled activated sludge that is collected in the secondary clarifier and returned to the aeration basin to mix with incoming raw or primary settled wastewater. Rabbling (water) - The process of moving or plowing the material inside a furnace by using the center shaft and rabble arms. Rack (water) - Evenly spaced parallel metal bars or rods located in the influent channel to remove rags, rocks, and cans from wastewater. Rain (water) - Particles of liquid water that have become too large to be held by the atmosphere. Their diameter generally is greater than 0.02 inch 31'\d they usually fall to the earth at velocities greater than 10 fps in still air. See PRECIPITAT! ON. Raw Water (water) - Water in its natural state, prior to any treatment. 0 Usually the water entering the first treatment process of a water treatment plant. Reaeration (water) -The introduction of air through forced air diffusers into the lower layers of the reservoir. As the air bubbles form and rise through the water, oxygen from the air dissolves into the water and replenishes the' dissolved oxygen. 'The rising bubbles also cause the lowe!" waters to rise to the surface where oxygen from the atmosphere is transferred to the water. This is sometimes called surface re aeration. Recarbonation (water) - A process in which carbon dioxide is bubbled into the water being treated to lower the pH The pH may also be lowered by the addition of acid. Recarbonation is the final stage in the lime-soda ash softening process. This process converts carbonate ions to bicarbonate ions and stabilizes the solution against the precipitation of carbonate compounds. Receiving Water (water) - A strecun_ river, lake, ocean, or other surface or ground waters into which treated or untreated wastewater is discharged. Recharge Rate (water) - Rate at which water is added beneath the ground surface to replenish or recharge groundwater. Reclamation (water) - The operation or process of changing the condition or characteristics of water so "that improved uses can be achieved. Recycle (water) - The use of water or wastewater within (internally) a facility before it is discharged to a treatment system. Also see REUSE.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 53

REDOX (wnter) - Reduction oxidation reactions in which the oxidation state of at least one reactilnt is raised while that of another is lowered. Reducing Agent (water) - Any substance, such as base metal (iron) or the sulfide ion (52-) that will readily donate (give up) electrons. The opposite is an OXIDIZING AGENT. Reductant (water),- A constituent of wastewater or surface waters that uses either free (02) or combined oxygen in the process of stabilization. Reflux (water) - Flow back. A sample is heated, evaporates, cools, condenses, and flows back to the flask. Refractory Materials (water) - Materials difficult to remove entirely from wastewater such as nutrients, color, taste and odor-producing substances and some toxic materials. Rehabilitate (canst) - Extensive maintenance intended to bring property or building up to current acceptable condition, often involving improvements Rehabilitation Project (canst) - Work associated with the rehabilitation and refurbishment of buildings, normally the responsibility of people within the above disciplines who have developed a particular expertise in this area. Reinforced concrete - Concrete reinforced with no less than the minimum amount required by this chapter, prestressed or non-prestressed, and designed on the assumption that the two materials act together in resisting forces. Reliquefaction (water) - The return of a gas to the liquid state; for example, a condensation of chlorine gas to return it to its liquid form by cooling. Renovate (canst) - Generally used to mean 'restore' Repair (canst) - To restore an item to an acceptable condition by the renewal, replacement or mending of decayed or damaged parts Resident Engineer (canst) - The site representative of the Engineer responsible for issuing instructions and drawings to the contractor's representative. Residue (water) - The dry solids remaining after the evaporation of a sample of water or sludge. Also see TOTAL DISSOLVED SOLIDS. Resistivity Probe (canst) - Sensors that measure depths of freezing and thawing fronts in the pavement structUre Respiration (water) - The process in which an organism uses oxygen for its life processes and gives off carbon dioxide. Restore (canst)- To bring back an item to its original appearance or state Restraint (canst) - The partial or total restriction of movement. A device which produces this effect Retention (water) - That part of the precipitation falling on a drainage area which does not escape as surface stream flow during a given period. It is the difference between total precipitation and total runoff during the period, and represents evaporation, transpiration, subsurface leakage, infiltration, and, when short periods are considered, temporary surface or underground storage on the area. 0 The delay or holding of the flow of water and water
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GLOSSARY OF CIVIL. ENGINEERING TERMS

Return Activated Sludge (RAS) (water) - Settled activated sludge that is collected in the secondary clarifier and returned to the aeration basin to mix with incoming raw or primary settled wastewater. Reverse Osmosis (water) - The application of pressure to a concentrated solution which causes the passage of a liquid from the concentrated solution to a weaker solution across a semipermeable membrane. The membrane allows the passage of the water (solvent) but not the dissolved solids (solutes). The liquid produced is a demineralized water. Also see OSMOSIS. Riprap (const) - Broken stones, boulders, or other materials placed compactly or irregularly on levees or dikes for the protection of earth surfaces against the erosive action of waves. Rise (const) -Distance from floor to floor. Riser (const) - Vertical face of a step. Its height generally is taken as the vertical distance between the treads. Rising Sludge (water) - Rising sludge occurs in the secondary clarifie~ of activated sludge plants when tlte sludge settles to the bottom of the clarifier, is compacted, and then starts to rise to the surface, usually as a result of denitrification. Roof Leader (water) - A downspout or pipe installed to drain a roof gutter to a storm drain or other means of disposal. Root Mop (water) '" When roots from plant life enter a sewer system, the roots frequently branch to form a growth that resembles a string mop. Root Sewer (water) - Any part of a root system of a plant or tree that enters a collection system. Rotameter (water) - A device used to measure the flow rate of gases and liquids. The gas or liquid being measured flows vertically up a tapered, calibrabid tube. Inside the tube is a small ball or bullet-shaped float (it may rotate) that rises or falls depending on the flow rate. The flow rate may be read on a scale behind or on the tube by looking at the middle of the ball or at the widest part or top of the float. Rotary Pump (water) - A type of displacement pump consisting essentially of elements rotating in a pump case which they closely fit. The rotation of these elements alternately draws m and discharges the water being pumped. Such pumps act with neither suction nor discharge valv,es, operate at almost any speed, and dp not depend on centrifugal forces to lift the water. Rotifers (water) - Microscopic animals characterized by short hairs on their front end. Rubble, Coursed (const) - Masonry composed of roughly shaped stones fitting approximately on level beds, well bonded and brought at vertical intervals to continuous level beds of courses. Rubble, Ordinary (const) - Masonry composed of irregularly shaped stones laid without regularity of coursing, but well bonded. Rubble, Random (const) - Masonry composed of roughly shaped stones, well bonded and brought at irregular intervals vertically to discontinuous but approximately level beds or courses. Run (const).- Total length of stairs in a horizontal plane, including landings. Runoff (water) - That part of rain or other precipitation that runs off the surface of a drainage area and does not enter the soil or the sewer system as inflow.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 55

Rutting Dipstick (const) - A manually operated device used to record transverse profiles for the bituminous cells.

s SA R (Sodium Adsorption Ratio) (water)- This ratio expresses the relative activity of sodium ions in the exchange reactions with soil. The ratio is defined as follows: S V I (Sludge Volume Index) (water) - This is a calculation which indicates the tendency of activated sludge solids (aerated solids) to thicken or to become concentrated during the sedimentation/thickening process.SVI is calculated in the following manner: (1) allow a mixed liquor sample from the aeration basin to settle for 30 minutes; (2) determine the suspended solids concentration for a sample of the same mixed liquor; (3) calculate SVI by dividing the measured (or observed) wet volume (mL/L) of the settled sludge by the dry weight concentration of MLSS in grams fL. Sacrificial Anode (water) - An easily corroded material deliberately installed in a pipe or tank. The intent of such an installation is to give up (sacrifice) this anode to corrosion while the water supply facilities remain relatively corrosion free. Saddle (water)- A fitting mounted on a pipe for attaching a new connection. This device makes a tight seal against tl1e main pipe by use of a clamp, adhesive, or gasket and prevents the service pipe from protruding into the main. Safe Water (water) - Water that does not contain harmful bacteria, or toxic materials or chemicals. Water may have taste and odor problems, color and certain mineral problems and still be considered safe for drinking. Safe Yield (water) - The annual quantity of water that can be taken from a source of supply over a period of years without depleting the source permanently (beyond its ability to be replenished naturally in "wet years"). Salinity (water) - The relative concentration of dissolved salts, usually sodium chloride, in a given water. 0 A measure of the concentration of dissolved mineral substances in water. Salt (water) - A compound which upon dissociation yields cations (positively charged) of a metal, and anions (negatively charged) of an acid radical. Sand Trap (water) - A device which can be placed in the outlet of a manhole to cause a settling pond to develop in the manhole invert, thus trapping sand, rocks and similar debris heavier than water. Also may be installed in outlets from car wash areas. Also see GRIT CATCHER. Sanitary Sewer (water) - A pipe or conduit (sewer) intended to carry wastewater or waterborne wastes from homes, businesses, and industries to the POTW (Publicly Owned Treatment. Works). Storm water runoff or unpolluted water should be collected and transported in a separate system of pipes or conduits (storm sewers) to natural watercourses. ·saprophytes (water)- Organisms living on dead or decaying organic matter. They help natural decomposition of organic matter in water. Saprophytic Organisms (water) - Organisms living on dead or decaying organic matter. They , help natural decomposition of the organic solids in wastewater. Sash (const)- A single assembly of stiles and rails made into a frame for holding glass, with or without dividing bars. It may be supplied glazed or unglazed.

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GLOSSARY OF CIVIL ENGINEERING TERMS

Saturated Soil (soil) - Soil that cannot absorb any more liquid. The interstices or void spaces in the soil are filled with water to the point at which runoff occurs. Saturation (water) - The condition of a liquid (water) when it has taken into solution the maximum possible quantity of a given substance at a given temperature and pressure. Saturator (water) - A device which produces a fluoride solution for the fluoridation process. The device is usually a cylindrical container with granular sodium fluoride on the bottom. Water flows either upward or downward through the sodium fluoride to produce the fluoride solution. Scale (water) - A combination of mineral. salts and bacterial accumulation that sticks to the inside of a collection; pipe under certain conditions. Scale, in extreme growth circumstances, creates additional friction loss to the flow of water; Scale may also accumulate on surfaces other than pipes. 0 The marked plate against which an indicator or recorder reads, usually the same as the range of the measuring system. See RANGE. Schedule, Pipe (water) - A sizing system of numbers that specifies the l.D. (inside diameter) and O.D. (outside diameter) for each diameter pipe. The schedule number is the ratio of • internal pressure in psi divided by the allowable fiber stress multiplied by 1,000. Typical schedules of iron and steel pipe are schedules 40, 80, and 160. Other forms of piping are divided into various classes with their own schedule schemes. Schmutzdecke (water) - A layer of trapped matter at the surface of a slow sand filter in which a dense population of microorganisms develops. These microorganisms within the film or mat feed on and break down incoming organic material trapped in the mat. In doing so the microorganisms both remove organic matter and add mass to the mat, further developing the mat and increasing the physical straining action of the mat. Scooter (water) - A sewer cleaning tool whose cleansing action dep~ds on the development of high water velocity around the outside edge of a circular shield. The metal shield is rimmed with a rubber coating and is attached to a framework on wheels (like a child's scooter). The angle of the shield is controlled by a chain spring system which regulates the head of water behind the scooter and thus the cleansing velocity of the water flowing around the shield. Screen (water) - A device used to retain or remove suspended or floating objects in wastewater. The screen has _openings that are generally uniform in size. It retains or removes objects larger than the openings. A screen may consist of bars, rods, wires, gratings, wire mesh, or perforated plates.

Scum (water) - A layer or film of foreign matter (such as grease, oil) that has risen to the surface of water or wastewater. 0 A residue deposited ori the ledge of a sewer, channel, or wet well at the water surface. 3) A mass of solid matter that floats on the surface. SeCI.ling Water (water) - Water used to prevent wastewater or dirt from reaching moving parts. SeCI.ling water is at a higher pressure than the wastewater it is keeping out of a mechanical device. Seasonal Water Table (water) - A groundwater table that has seasonal changes in depth or elevation. Secondary Oarifier (water) - A wastewater treatment device which consists of a rectangular or circular tank that allows those substances not removed by previous treatment processes that settle or float to be separated from the wastewater being treated. Secondary Treatment (water) - A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually the process follows primary treatment by sedimentation. The process commonly

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 57

is a type of biological treatment process followed by secondary clarifiers that allow the solids to settle out from the water being treated.

Sediment (water) -Solid material settled from suspension in a liquid. Sedimentation (water) - A water treatment process in which solid particles settle out of the water being treated in a large clarifier or sedime!ltation basin. Sedimentation Basin (water) - Clarifier, Settling Tank. A tank or basin in which wastewater is held for a period of time during which the heavier solids settle to the bottom and the lighter materials float to the water surface. Seed Sludge (water) - In wastewater h·eahnent, seed, seed culture or seed sludge refers to a mass of sludge which contains populations of microorganisms. When a seed sludge is mixed with wastewater or sludge being treated, the process of biological decomposition takes place more rapidly. Seismic (gen)- Relating to an earthquake or violent earth vibration such as an explosion. Select Backfill (const) - Material used in backfilling of an excavation, selected for desirable compaction or other characteristics. Select Bedding (water) - Material used to provide a bedding or foW1dation for pipes or other underground structures. This material is of specified quality for desirable bedding or other characteristics and is often imported from a different location. Selector (water) - A reactor or basin in which baffles or other devices create a series of compartments. The environment and the resulting micwbial population within each compartment e
G- 58

GLOSSARY OF CIVIL ENGINEERING TERMS

Sequestration (water) - A chemical complexing (forming or joining together) of metallic cations (such as iron) with certain inorganic compounds, such as phosphate. Sequestration prevents the precipitation of the metals (iron). Also see CHELATION. Serial Tender (const) - A serial tender is where a number of similar projects are awarded to a contractor, following a competitive tender on a master bill of quantities. This master bill forms a standing offer open for the client to accept for a number of contracts. Each contract is separate and the price for each calculated separately. Series Operation (water) - Wastewater being treated flows through one treatment unit and then flows through another similar treatment unit. Also see PARALLEL OPERATION. Service Pipe (water) - The pipeline extending from the water main to the building served or to the.consumer's system. Service Root (water) - A root entering the sewer system in a service line and growing down the pipe and into the sewer main. Settle.ment (soil) - Downward movement of the soil or of a structure which it supports Sewage (water) - The used household water and water-carried solids that flow in sewers to a wastewater treatment plant. The preferred term is WASTEWATER. Sewer (water) - A pipe or conduit that carries wastewater or d~ainage water. The term "collection line" is often used also. · Sewer Ball (water) - A spirally grooved, inflatabler semi-hard rubber ball designed for ; hydraulic cleaning of sewer pipes. See BALLING. I

'wer Cleanout (water) - A capped opening in a sewer main that allows access to the pipes for rodding and cleaning. Usually such cleanouts are located at terminal pipe ends or beyond terminal manholes. Also called a FLUSHER BRANCH. Sewer Gas (water) - Gas in collection lines (sewers) that results from the decomposition of organic matter in the wastewater. When testing for gases found in sewers, test for lack of oxygen and also for explosive and toxic gases. 0 Any gas present in the wastewater collection system, even though it is from such sources as gas mains, gasoline, and cleaning fluid. Sewer Main (water) - A sewer pipe to which building laterals are connected. Also called a COLLECTION'MAlN. Sewerage (water) - System of piping with appurtenances for collecting, moving and treating wastewater from source to discharge. · Shear Wall (const) - A wall that resist horizontal forces applied in the plane of the wall. Shock Load (water) - The arrival at a water treatment plant of raw water containing lJI\USual amounts of algae, colloidal matter, color, suspended solids, turbidity, or other pollutants. Shredding (water) - Comminution. A mechanical treatment process which cuts large pieces of wastes into smaller pieces so they won't plug pipes or damage equipment. SHREDDING and COMMINUTION usually mean the same thing. Shrinkage (const) -Decrease in length or volume Sidestream !water)- Wastewater flows that develop from other storage or treatment facilities . . This wastewater may or may not need additional treatment. Significant Figure (gen) - The number of accurate numbers in a measurement. If the distance between two points is.measured to the nearest hundredth and recorded as 238.41 feet, the measurement has five significant figures.

GLOSSARY OF CIVIL ENGINEERING TERMS

G -59

Sill (const) -The horizontal bottom of a frame. Silting (water) - Silting takes place when the pressure of infiltrating waters is great enough to carry silt, sand and other small particles from the soil into the sewer system. Where lower velocities are present in the sewer pipes, settling of these materials results in silting of the sewer system. Single-Stage Pump (water) - A pump that has only one impeller. A multistage pump has more than one impeller, Siphon (water) - A pipe or conduit through which water will flow above the hydraulic grade line (HGL) under certain conditions. Water (or other liquid) is first forced to flow or is sucked or drawn through the pipe by creation of a vacuuin. As long as no air enters the pipe to interrupt flow, atmospheric pressure on the liquid at the elevated (higher) end of the siphon will cause the flow to continue. Site Co-ordination (const) - Responsibility for the co-ordination of day-to-day operations on site in accordance with the project and the predetermined program, typically carried out by an employee of the contractor. Site Management (const) - The overall management of the processes required to bring the site operations of a project to a satisfactory conclusion, typically carried out either by private consultant or an employee of the project client. · Site Manager (const) - The person responsible on behalf of the client for controlling and coordinating all the work of others in order to bring the site operations of a project to a satisfactory conclusion. Site works (const) - All work carried out within the site of a construction project Skatole (water) - An organic compound (C9H9N) that contains nitrogen and has a fecal odor. Slake (water) - To mix with water so that a true chemical combination (hydration) takes place, such as in the slaking of lime. Sliplinirtg (water) - A sewer rehabilitation technique accomplished · by inserting flexible polyethylene pipe into an existing deteriorated sewe~:. Slope (water) - The slope or inclination of a trench bottom or a trench side Wall is the ratio of the vertical distance to the horizontal distance or "rise over run." Also see GRADE (2). Sloughing (water) - Biological or biomass growths which break off from the fixed film media. The "sloughed" biological growth becomes suspended in the fixed film effluent and is later removed in the secondary clarifier as sludge. Sludge (water) -The settleable solids separated from water during processing. Sludge Age (water) - A measure of the length of time a particle of suspended solids has been retained in the activated sludge process. Sludge Density Index (SDI) (water) - This calculation is used in a way similar to the Sludge Volume Index (SVI) to indicate the settleability of a sludge in a secondary clarifier or effluent. The weight in grams of one milllliter of sludge after settling for 30 minutes. SDI = 100/SVI. Also see SLUDGE VOLUME INDEX (SVI). Sludge Digestion (water) - The process of changing organic matter in sludge into a gas or a liquid or a more stable solid form. These changes take place as microorganisms feed on . sludge in anaerobic (more common) or aerobic digesters. Sludge Gasification (water) - A process in which soluble and suspended organic matter are converted into gas by anaerobic decomposition. The resulting gas bubbles can become

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GLOSSARY OF CIVIL ENGINEERING TERMS

attached to the settled sludge and cause large clumps of sludge to rise and float on the · water surface. Sludge Volume Index (SVI) (water) - This is a calculation which intiicates the tendency of activated sludge solids (aerated solids) to thicken or to become concentrated during the sedi~entation/thickening process. SVI is calculated in the following manner: (1) allow a mixed liquor sample from the aeration basin to settle for 30 minutes; (2) determine the suspended solids concentration for a sample of the same mixed liquor; (3) calculate SVI by dividing the me!lsured (or observed) wet volume (mL/L) of the settled sludge by the dry weight concentration of MLSS in gran:s/L. Sludge-Volume Ratio (SVR) (water) - The volume of sludge blanket divided by the · daily volume of sludge pumped from the thickener. Slugs (water) - Intermittent releases or discharges of if\dustrial wastes. Slurry (water) - A watery mixture or suspension of insoluble (not dissolved) matter; a thin, watery mud or any substance resembling it (such as a grit slurry or a lime slurry). S'l'oke Test (water) - A method pf blowing smoke into a closed off section of a sewer system to locate sources of surface inflow. Snake (water) - A stiff but flexible cable that is inserted into sewers to clear stoppages; also known as a "sewer cable." ·Soap Cake or Soap Buildup (water)- A combination of detergents and greases that accumulate in sewer systems, build up over a period of time, and may cause severe flow restrictions. Soft Water (water) - Water having a low concentration of calcium and magnesium ions. According to U.S. Geological Survey guidelines, soft water is water having a hardness of 60 milligrams per liter or less. Soil Displacement (water) - Movement of soil from one place to another. Generally accompanies SILTING of a sewer system. Where infiltration is taking place and silt is carried into a sewer system, such silt or soil is removed from the ground around the sewer pipe and the result is soil displacement. Soil Pipe (water) - A type of wastewater or service connection pipe made of a low grade of cast iron. 0 In plumbing, a pipe that carries the discharge of toilets or similar fixtures, with or without the discharges from other fixtures. Soil Pollution (water)- The leakage (exfiltration) of raw wastewater into the soil or ground area · around a sewer pipe. Soil Pressure Gauge (soil) -Sensors that measure static and dynamic stresses, both vertical and horizontal, in soils and oilier unbounded layers. Soil Stabilization (water) -Injection of chemical grouts into saturated or otherwise unstable soil. The process seals out water and prevents further instability. Solid Masonry Unit (const) - A masonry \lfrlt with net cross-sectional area in every plane parallel to the bearing surface 75% or more of its gross cross-sectional area measured in the same plane. Solids Concentration (water) -The solids in the aeration tank which carry microorganisms that feed on wastewater. Soluble BOD (water) - Soluble BOD is the BOD pf water that has been filtered in the standard suspended solids test..

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 61

Solute (water) -The substance dissolved in a solution. A solution resistant to disinfectants and heat than most organisms. Spring Line (water) - Theoretical center of a pipeline. Also, the guid~line fo'i iaying a course of bricks.

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GLOSSARY OF CIVIL ENGINEERING TERMS

Srteriliution (water) - The rsmoval or destruction of all microorganisms,' including pathogenic and other bacteria, vegetative forms and spores. Compare with DISINFECTION. Stabilization (water) - Conversion to a form that resists change. Organic material is stabilized by bacteria which convert the material to gases and other relatively inert substances. Stabilized organic material generally will not give off obnoxious odors. Stabilize (water) - To convert to a form that resists change. Organic material is stabilized by bacteria which convert the material to gases and other relatively inert substances. Stabilized organic material generally will not give off obnoxious odors. Stabilized Waste (water) - A waste that has been treated or decomposed to the extent that, if discharged or released, its rate and state of decomposition would be such that the waste would not cause a nuisance or odors. Stain (const) - To discolor. An uncontrolled discoloration, usually on concrete, masonry, and wood Stale Water (water)- STALE WATER Standard Deviation (gen) - A measure of the spread or dispersion of data. Standard Solution (water) (water) - A solution in which the exact concentration of a chemical or compound is known. Stasis - Stagnation or inactivity of the life processes within organisms. Static Head (water) - When water is not moving, the vertical distance (in feet) from a specific point to the water surface is the static head. (The static pressure in psi is the static head in feet times 0.433 psi/ ft.) Also see DYNAMIC PRESSURE and STATIC PRESSURE. Static Lift (water) - Vertical distance water is lifted from upstreazn water surface up to downstream water surface (which is at a higher elevation) when no water is being pumped. · Static Pressure (water) - When water is not moving, the vertical distance (in feet) from a specific point to the·water surface is the static head. The static pressure in psi is the static head in feet times 0.433 psi/ ft. Also see DYNAMIC PRESSURE and STATIC HEAD. Static Sensors (const) - Those sensors that generate data at 15 minute intervals Examples are weather sensors, etc. Static Water Depth (water) - The vertical distance in feet from the centerline of the pump discharge down to the surface level of the free pool while no water is being drawn from the pool or water table. Static Water Head (water)- Elevation or surface of water that is not being pumped. Static Water Level (water)- .The elevation or level of the water table in a well when the pump is not operating. 0 The level or elevation to which water would rise in a tube connected to an artesian aquifer, basin, or conduit under pressure. Station (water)- A point of reference or location in a pipeline is sometimes called a "station." As an example, a building service located 51 feet downstream from a manhole could be reported to be at "station 51." Step-Feed Aerption (water) - Step feed aeration is a modification of the conventional activated sludge process. In step atfration, primary effluent enters the aeration tank at several points along the length of the tank, rather than all of the primary effluent entering at the beginning or head of the tank and flowing through the entire tank in a plug flow mode.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 63

Stilling Well (water) - A well or chamber which is connected to the main flow channel by a small inlet. Waves and surges in the main flow stream will not appear in the well due to the small diameter inlet. The liquid surface in the well will be quiet, but will follow all of the steady fluctuations of the open channel. The liquid level in the well is measured to determine the flow in the main channel. Stirrup (const) - Reinforcement used to resist shear and torsion stresses in a structural member: typically bars, wires or welded wire fabric (smooth or deformed) either single leg or bent into L, U, or rectangular shapes and located perpendicular to or at an angle to longitudinal reinforcement. (The term "stirrups" is usually applied to lateral reinforcement in flexural members and the term "ties" to those in compression members.) See also Tie. Stitching (const) -Insertion of new bricks to replace existing damaged bricks Stool (const) -The part of the sill inside the building. Stop Log (water) - A log or board in an outlet box or device used to control the water level in ponds. Storm Collection System (water) - A system of gutters, catch basins, yard drains, culverts and pipes for the purpose of conducting storm waters from an area, but intended to exclude domestic and industrial wastes. Storm Runoff (water) - The amount of runoff that reaches the point of measurement within a relatively short period of time .after the occurrence of a storm or other form of precipitation. Also called "direct runoff." Storm Sewer (water) - A separate pipe, conduit or open channel (sewer) that carries runoff from storms, surface drainage, and street wash, but does not include domestic and Industrial wastes. Storm sewers are often the recipients of hazardous or toxic substances due to the illegal dumping of hazardous wastes or spills created by acddents involving vehicles and trains transporting these substances. Also see SANITARY SEWER. Storm Water (water) - The excess water running off from the surface of a drainage area during and immediately after a period of rain. See STORM RUNOFF. Storm Water Inlet (water) - A device that admits surface waters to the storm water drainage system. Also see CURB INLET and CATCH BASIN. Stratification (water) -The formation of separate layers (of temperature, plant, or animal life) in a lake or reservoir. Each layer has similar characteristics such as all water in the layer has the same temperature. Also see THERMAL STRATIFICATION.. Stray Current Corrosion (water) - A corrosion activity resulting from stray electric current originating from some source outside the plun;tbing system such as D.C. grounding on phope systems. Strength design (const) - Nominal strength multiplied by a strength reduction factor,

0.

Strength, nominal - Strength of a member or cross-section _calculation in accordance with provisions and assumptions of the strength design method of this chapter before application of any strength reduction factors. Strength, required - Strength of a member or cross section required to resist factored loads or related internal moments and forces in such combinations. Stress (gen) - Intensity of force per unit area. Stretch (water) ~Length of sewer from manhole to IID1nh0le.

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61

GLOSSARY OF CIVIL ENGINEERING TERMS

Stringers (const)- Inclined members along the sides of a stairway. The stringer along the wall is called a wall stringer. Open stririgers are those cu to follow the lines of risers and treads. Closed stringers have parallel top and bottom, and treads and risers are supported along their sides or mortised into them. In wood stairs, stringers are placed outside the carriage to provide a finish. · Stringers (water) - Horizontal shoring members, usually square, rough cut timber, that are used to hold solid sheeting, braces or vertical shoring members in place. Also called WALERS. Stripped Gases (water) - Gases that are released from a liquid by bubbling air through the liquid or by allowing the liquid to be sprayed or tumbled over media. Stripped Odors (water) - Odors that are released from a liquid by bubbling air through the liquid or by allowing the liquid to be sprayed or tumbled over media. Structural Defect (const) -:A flaw or imperfection of a structure or design which was built into a project, pipeline or other collection system appurtenance. Structural Design (const) - Design of the structural elements of large constructions, undertaken by a structural engineer. In smaller and less complex constructions this work will • normally be within the responsibility of other construction professionals. Structural Failure (water) - A condition that exists when one or more components of a system break down or fail to perform as expected. A structural failure may result from defective parts or design or may result from other circumstances that occur after the completion of construction. Struvite (water) - A deposit or precipitate of magnesium ammonium phosphate hexahydrate found on the rotating components of centrifuges and centrate discharge lines. Struvite can be formed when anaerobic sludge comes in contact with spinnirlg centrifuge components rich in oxygen in . the presence of microbial activity. Struvite can also be formed in digested sludge lines and valves in the presence of oxygen and microbial activity. Struvite can form when the pH level is between 5 and 9. Stuck (water) - Not working. A stuck digester does not decompose organic matter properly. · The digester is characterized by low gas production, high volatile acid to alkalinity relationship, and poor liquidsolids separation. A digester in a stuck condition is sometimes called' a "sour" or "upset" digester. Submergence (water) -The distance between the water surface and the media surface in a filter. Subsidence (water) - The dropping or lowering of the ground surface as a result of removing excess water (overdraft or overpumping) from an aquifer. After excess water has been reindved, the soil will settle, become compacted and the ground surface will drop and can cause the settling of underground utilities. Subsoil Geology (soil) -The study of soil conditions existmg below the surface of the ground at · any selected site. Substrate (water) - The base on which an organism lives. The soil is the substrate of most seed plants; rocks, soil, water, or other plants or animals are substrates for other organisms. 0 Chemical used by an organism to support growth. The organic matter in wastewater is a substrate. for the organisms in activated sludge. Subsurface Leaching System (water) - A method of treatment and disposal of septic tartk effluent, sand filter effluent, or other treated wastewater. The effluent is applied to soil below the ground surface through open"jointed pipes or drains or through perforated pipes (holes in the pipes). The effluent is treated as it passes through porous soil or rock

GLOSSARY OF CIVIL ENGINEERING TERMS

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sb'ata (layers). Newer subSiuface leaching systems include chamber and · gravelless systems, and also gravel b'enches without pipe the full length of the b'ench. Subsystem (water) - An extensive underground sewer system connected to the main collection system, but not considered part of the main system. An example might be the undergro.u nd sewer system of a mobile home park. Sucker Rods (water) - Rigid, coupled sewer rod~ of metal or wood used for clearing stoppages. Usually available in 3ft, 39in, 4ft, Sft and 6ft lengths. Suction Head (water) - The POSffiVE pressure [in feet (meters) or pounds per square inch] on the suction side of a pump. The pressure can be measured from the centerline of the pump UP TO the elevation of the hydraulic grade line on the suction side of the pump. Suction lift (water)' The NEGATIVE pressure (in feet (meters) of water or inches (centimeters) of mercury vacuum] on the suction side of the pump. The pressure can be measured 'from the centerline of the pump OOWN TO (lift) the elevation of the hydraulic grade line on the suction side of the pump. Sump (water) -The term "sump" refers to a facility which connects an indusb'ial discharger to a public sewer. The facility (sump) could be a sample box, a clarifier or an intercepting sewer. Sump Card (water) - A 3x5 reference card which identifies the location of a sump, lists the monitoring devices located in the sump (pH for example), and indicates which b'eatment processes are connected to the sump. Superchlorination (water) - Chlorination with doses that are deliberately selected to produce free or combined residuals so large as to require dechlorination. Sup,ematant (water) - Uquid removed from settled sludge. Supernatant commonly refers to the liquid between the sludge on the bottom and the sewn on the water surface of a basin or container. Supersaturated (water) - An unstable condition of a solution (water) in which the solution contains a substance at a concenb'ation greater than the saturation concentration for the substance. Surcharge (water) - Sewers are surcharged when the supply of water to be carried is greater than the capacity of the pipes to carry the flow. The surface of the wastewater in manholes rises above the top of the sewer pipe, and the sewer is under pressure or a head, rather than at atmospheric pressure. Surcharge Manhole (water) - A manhole in which the rate of the water entering is greater than the capacity of the outlet under gravity flow conditions. When the water in the manhole rises above the top of the outlet pipe, the IDanhole is said to be "surcharged." Surface Loading (water) - One of the guidelines for the design of settling tanks and clarifiers in b'eatment plants. Used by operators to determine if tanks and clarifiers are hydraulically (flow) over or underloaded. Also called OVERFLOW RATE. Surface Runoff. (water) - The precipitation that cannot be absorbed by the soil and flows across the surface by gravity. 0 The water that reaches a sb'eam by b'aveling over the soil surface or falls directly into the sb'eam channels, including not only the large permanent sb'eams but also the tiny rills and rivulets. 3) Water that remains after infilb'ation, interception, and surface storage have been deducted from total precipitation. Surfaced Defect (water) - A break or opening in a sewer pipe where the covering soil has been washed away and the opening or break is exposed on the ground surface.

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GLOSSARY OF CIVIL ENGINEERING TERMS

Surfaced Void (water)- A dip or depression in the ground that appears when silting has taken place to a degree that a void is caused in the subsoil. Through successive caveins, the void reaches the surface of the ground. Surfactant (water) - Abbreviation for surface-active agent. .The active agent in detergents that possesses a high cleaning ability. Surge Chamber (water) - A chamber or tank connected to a pipe and located at or near a valve that may quickly open or close or a pump that may suddenly start or stop. When the flow of water in a pipe starts or stops quickly, the surge chamber allows water to flow into or out of the pipe and minimize any sudden positive or negative pressure waves or surges in the pipe. Suspended Growth Process (water) - Wastewater treatment processes in which the microorganisms and bacteria treating the wastes are suspended in the wastewater being treated. The wastes flow around and through the suspended growths. The various modes of the activated sludge process make use of suspended growth reactors. These reactors can be used for BOD removal, nitrification and denitrification. Suspended Solids (water) - Solids that either float on the surface or are suspended in water, wastewater, or other liquids, and which are largely removable by laboratory filtering. 0 The quantity of material removed hom water in a laboratory test, as prescribed in STANDARD METHODS FOR THE EXAMINATION OF WATER AND WASTEWATER, and referred to as.Total Suspended Solids Dried at 103-lOS"C. Swab (water) - A circular sewer cleaning tool almost the same diameter as the pipe being cleaned. As a final cleaning procedure after a sewer line has been cleaned with a porcupine, a swab is pulled through the sewer and the flushing action of water flowing around the tool cleans the line. Synergistic Reaction (water) - An interaction between two or mor~ individual compounds which produces an injurious effect upon the body (or an organism) which is GREATER than either of the substances alone would have produced.

T T 0 C (water) -Total Organic Carbon. TOC measures the amount of organic carbon in water. Tag Line (water) ~ A line, rope or cable that follows equipment through a sewer so that equipment can be pulled back out if it encounters an obstruction or becomes stuck. . Equipment is pulled forward with a pull line. Tap (water) - A small hole in ·a sewer where a wastewater service line hom a building is connected (tapped) into a lateral or branch sewer. Temporary Groundwater Table (water) - During and for a period following heavy rainfall or snow melt, the soil is saturated at elevations above the normal, stabilized or seasonal groundwater ·table, often hom the surface of the soil downward. This is referred to as a temporary condition and thus is a temporary groundwater table. D When a collection system serves agriculturill areas in its vicinity, irrigation of these areas ,can cause a temporary rise in the elevation of the groundwater table. · Tender (const) - An offer which incorporates the sum of money, time and other conditions required to carry out the contract obligations in order to complete a project or a part of it consisting of specified works.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 67

Tendering (const) - Tendering is the management and commercial function of determining the tender based upon the estimate and other details prepared by the contractor's estimator and other personnel. ' Tendon (const) - Steel element such as wire, cable, bar, rod, or strand, or a bundle of such elements, used to impart prestress to concrete. Teratogenic (water) - Any substance which tends to cause birth defects after conception. Terminal Cleanout (water)- When a manhole is not provided at the upstream end of a sewer main, a cleanout is usually provided. This is called a "terminal cleanout" or. a FLUSHER BRANCH. Terminal Manhole (water) - A manhole located at the upstream end of a sewer and having no inlet pipe. Also called a DEAD END MANHOLE. Tertiary Treatment (water)- Any process of water renovation that upgrades treated wastewater to meet specific reuse requirements. May include general cleanup of water or removal of specific parts of wastes insufficiently removed by conventional treatment processes. Typical processes include chemical treatment and pressure filtration. Also called ADVANCED WASTE TREATMENT. Thermal shock (const) - Force, arising out of thermal expansion or contraction, which causes disruption of a material on sudden heating or cooling Thermal Stratification (water) - The formation of layers of different temperatures in a lake or reservoir. Also see STRATIFICATION. Thermocline (water) - The middle layer in a thermally stratified lake or reservoir. In this layer there is a rapid decrease in t~mperature with depth. Also called the METALIMNION. Thermohygrograph (const) - Device that measures and records simultaneously air temperature and relative humidity Thermophilic Bacteria (water) - Hot temperature bacteria. A group of bacteria that grow and thrive in temperatures above 113°F (45°C). The optimum temperature range for these bacteria in anaerobic decomposition is 120°F (49°C) to 135°F (57"C). Aerobic thermophilic bacteria thrive between 120°F (49°C) and 158°F (70°C). Thickening (water) - Treatment to remove water from the sludge mass to reduce the volume that must be handled. Thief Hole (water) - A digester sampling well which allows sampling of the digester contents without venting digester gas. Threshold Limit Value (TLV) (water) - The average concentration oftoxic gas or any other substance to which a normal person can be exposed without injury during an average work week. Threshold Odor (water) - The minimum odor of a water sample that can just be detected after successive dilutions with odorless water. Also called ODOR THRESHOLD. Threshold Odor Number (TON) (water) - The greatest dilution of a sample with odor-free water that still yields a just detectable odor. Thrust Block (water) - A mass of concrete or similar material appropriately placed around a pipe to prevent movement when the pipe is carrying water. Usually placed at bends and valve structures. Tide Gate (water) - A gate with a flap suspended from a free-swinging horizontal hinge, usually placed at . the end of a conduit discharging into a body of water having a

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GLOSSARY OF CIVIL ENGINEERING TERMS

fluctuating surface elevation. The gate is usually closed because ofoutside water pressure, but will open when the water head inside the pipe is great enough to overcome the outside pressure, the weight of the flap, and the friction of the hinge. Also called a BACKWATER GATE. Also see CHECK VALVE and FLAP GATE. Tie (const) - Loop of reinforcing bar or wire enclosing longitudinal reinforcement. See also stirrup. Time Lag (water) - The time required for processes and control systems to respond to a signal or to reach a desired level. Time Weighted Average (water)- The average concentration of a pollutant based on the times and levels of concentrations of the pollutant. The time weighted average is equal to the sum of the portion of each time period (as a decimal, such as 0.25 hour) multiplied by the pollutant concentration during the time period divided by the hours in the workday (usually 8 hours). Total Contribution (water) - All water and wastewater entering a sewer system from a specific facility, subsystem or area. This includes domestic and industrial wastewaters, inflow and • infiltration reaching the main collection system. Total Dissolved Solids (TDS) (water) - All of the dissolved solids in a water. TDS is measured on a sample of water that has passed through a very fine mesh filter to remove suspended solids. The water passing through the filter is evaporated and the residue represents the dissolved solids. Also see SPECIFIC CONDUCTANCE. Total Dynamic Head (TDH) (water) - When a pump i;; lifting or pumping water, the vertical distance (in feet) from the elevation of the energy grade line on the suction side of the pump to the elevation of the energy grade line on the discharge side of the pump. Total Organic Carbon (TOC) (water)- TOC measures the amount of oPganic carbon in water. Total Residual Chlorine (water) - The amount of available chlorine remaining after a given contact time. The sum of the combined available residual chlorine and the free available residual chlorine. Also see RESIDUAL CHLORINE. Totalizer (water) - A device or meter that continuously measures and calculates (adds) a process rate variable in cumulative fashion; for example, total flows displayed in gallons, million gallons, cubic feet, or some other unit of volume measurement. Also called an INTEGRATOR. ' Toxaphene (water) - A chemical that causes adverse health effects in domestic water supplies and also is toxic to freshwater and marine aquatic life. Toxic (water)- A substance which is poisonous to a Jiving organism. Toxic Organic Management PJ.cin (TOMP) (water) - A strategy for keeping track of all solvents delivered to a site, their storage, use and disposal. This includes keeping spent solvents segregated from other process wastewaters to maximize the value of the recoverable solvents, to avoid contamination of other segregated wastes, and to prevent the discharge of toxic organics to any wastewater collection system or the environment. The plan should describe measures to control spills and leaks and to ensure that there is no deliberate dumping of solvents. Also known as a SOLVENT MANAGEMENT PLAN. Toxicity (water) - The relative degree of being poisonous or toxic. A condition which may exist in wastes and will inhibit or destroy the growth or function of certain organisms. Traditional Contracting (const) - Is the method of construction procurement in which independent professionals (i.e. architects, engineers, quantity surveyors) are employed by the client to complete the design work. The client then enters into separate contract with a

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 69

contractor to execute the designed construction. The contractor is selected on some basis of competition. Tramp Oil (Free Oil) (water) -Oil that comes to the surface of a tank due to natural flotation. Transfer (const)- Act of transferring stress in prestressing tendons from jacks or pretensioning bed to concrete member. Transmissivity (water) - A measure of the ability to transmit (as in the ability of an aquifer to transmit water). Transpiration (water) - The process by which water vapor is released to the atmosphere by living plants. This process is similar to people sweating. Also see EVAPOTRANSPIRATION. Trap (water) - In the wastewater collection system of a building, plumbing codes require every drain connection from an appliance or fixture to have a trap. The trap in this case is a gooseneck that holds water to prevent vapors or gases in a collection system from entering the building. 0 Various other types of special traps are used in collection systems such as a GRIT TRAP or SAND TRAP. Tread (canst) -Horizontal face of a step. Its width usually is taken as the horizontal distance between risers . . Tremie (water)- A device used to place concrete or grout under water. Trichloroethane (water) - An organic chemical used as a cleaning solvent that causes adverse health effects in domestic water supplies. Trickling Filter (water) - A treatment process in which the wastewater trickles over media that provide the opportunity for the formation of slimes or biomass which contain organisms that feed upon and remove wastes from the water being treated. Trickling Filter Media (water) - Rocks or other durable materials that make up the body of the filter. Synthetic (manufactured) media have been used successfully. True Color (water) - Color of the water from which turbidity has been removed. The turbidity may be removed by double filtering the sample through a Whatrnan No. 40 filter when using the visual comparison method. Trunk Sewer (water) - A sewer that receives wastewater from many tributary branches or sewers and serves a large territory and contributing population. Trunk System (water) - A system of major sewers serving as transporting lines and not as local or lateral sewers. Tube Settler (water) - A device that uses bundles of small-bore (2 to 3 inches or 50 to 75 mm) tubes installed on an incline as an aid to sedimentation. The tubes may come in a variety of shapes including circular and rectangular. As water rises within the tubes, settling solids fall to the tube surface. As the ~Judge (from the settled solids) in the tube gains weight, it moves down the tubes and settles to the bottom of the basin for removal by conventional sludge collection means. Tube settlers are sometimes installed in sedimentation basins and clarifiers to improve particle removal. Tubercle (water) - A protective crust of corrosion products (rust) which builds up over a pit caused by the loss of metal due to corrosion. Tuberculation (water) - The development or formation of small mounds of corrosion products (rust) on the inside of iron pipe. These mounds (tubercles) increase the roughness of the inside of the pipe thus increasing resistance to water flow (decreases the C Factor).

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GLOSSARY OF CIVIL ENGINEERING TERMS

Turbid (water) - Having a cloudy or muddy appearance. Turbidity (water) - The cloudy appearance of water caused by the presence of suspended and colloidal matter. In the waterworks field, a turbidity measurement is used to indicate the clarity of water. Technically, turbidity is an optical property of the water based on the amount of light reflected by suspended particles. Turbidity caru:tot be directly equated to suspended solids because white particles reflect more light than dark-colored particles and many small particles will reflect more light than an equivalent large particle. Turbidity Meter (water) - An instrument for measuring and comparing the turbidity of liquids by passing light through them and determining how much light is reflected by the particles in the liquid. The normal ·measuring range is 0 to 100 and is expressed as Nephelometric Turbidity Units (NTUs). Turbidity Units (water) -Turbidity units are a measure of the cloudiness of water. If measured by a nephelometric (deflected light) instrumental procedure, turbidity units are expressed in nephelometric turbidity units (NTU) or simply TU. Those turbidity units obtained by visual methods are expressed in Jackson Turbidity Units GTU) which are a measut:e of the cloudiness of water; they are used to indicate the clarity of water. There is no real connection between NTUs and JTUs. The Jackson turbidimeter is a visual method and the nephelometer is an instrumental method based on defle<;ted light. Turbulent Mixers (water) - Devices that mix air bubbles and water and cause turbulence to dissolve oxygen in the water. Turnkey (const) - A turnkey contract is one where the client has an agreement with one single administrative entity, who provides the design and construction under one contract, and frequently effects land acquisition, financing, leasing, etc. Two-Stage Filters (water) - Two filters are used. Effluent from the first filter goes to the second filter, either directly or after passing through a clarifier. Two-stage Tender (const) - With a two-stage tender three or four con-tractors with appropriate experience are first separately involved in detailed discussions with the client's professional advisers regarding all aspects of the project. Price competition is introduced in the second stage. Two-Way Cleanout (water)- An opening in pipes or sewers designed for rodding or working a snake into th~ pipe in either direction. Two-way cleanouts are most often found in building lateral pipes at or near a property line.

u,v Ultrafiltration (water) - A membrane filter process used for the removal of some organic , compounds in an aqueous (watery) solution. Unconsolidated Formation (water) - A sediment that is loosely arranged or unstratified (not in layers) or whose particles are not cemented together (soft rock); occurring either at the ground surface or at a depth below the surface. Also see CONSOLIDATED FORMATION. Undermined (water) - A condition that occurs when the bedding support under a pipe or manhole has been removed or washed away. Conditions leading to or causing this are believed to be the presence of excess water during backfill. Other causes are horizontal boring operations, excavations adjacent to the pipe or manhole and exfiltration or infiltration at drop joints. 0 When flow through a broken section of pipe carries away soil

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 71

around the break leaving a void or empty space, the surfaces over the void are said to be "undermined." Undisturbed Soi (water)! - Soil, at any depth, which has not been excavated or disturbed by excavation or construction. Uniformity Coefficient (water)- The ratio of (1) the diameter of a grain (particle) of a size that is barely too large to pass through a sieve that allows 60 percent of the material (by weight) to pass through, to (2) the diameter of a grain (particle) of a size that is barely too large to pass through a sieve that allows 10 percent of the material (by weight) to pass through. The resulting ratio is a measure of the degree of uniformity in a granular material such as filter media. Upper Explosive limit (water) - The point at which the concentration of a gas in air becomes too great to allow an explosion upon ignition due to insufficient oxygen present. Upper Flamable limit (water) -The point at which the concentration of a gas in air becomes too great to sustain a flame upon ignition due to insufficient oxygen present. Upset (water)- An upset digester does not decompose organic matter properly. The digester is characteqzed by low gas production, high volatile acid/ alkalinity relationship, and poor liquidsolids separation. A digester in an upset condition is sometimes called a "sour" or "stuck" digester. Upstand (const) - Portion of roof covering turned up against a vertical surface, yet not necessarily tucked into a groove Upstream (water) - The direction against the flow of water; or, toward or in the higher part
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GLOSSARY OF CIVIL ENGINEERING TERMS

r Viscosity (water) - A property of water, or any other fluid, which resists efforts to change its shape or flow. Syrup is more viscous (has a higher viscosity) than water. The viscosity of water increases significantly as temperatures decrease. Motor oil is rated by how thick (viscous) it is; 20 ~eight oil is considered relatively _thin while 50 weight oil is"relatively thick or viscous. V-Notch Weir (water) - A triangular weir with a "V" notch calibrated in gallons per minute readings. By holding the weir in a pipe with rubber seals forcing a flow to pass through the "V," a measure of the gallonage flowing through the pipe can be read on the basis of . the depth of water flowing over the weir. Void (const) - (in the context of cellular materials, such as concrete) cavity formed either intentionally or unintentionally Void (soil)- A pore or open space in rock, soil or other granular material, not occupied by .solid matter. The pore or open space may be occupied by air, water, or other gaseous or liquid material. Also called an INTERSTICE, PORE, or void space. Volatile (water)- A volatile substance is one that is capable of being evaporated or changed to • a vapor at relatively low temperatures. Volatile substances., also can be partially removed by air stripping. 0 ln terms of solids analysis, volatile refers to materials lost (including most organic matter) upon ignition in a muffle furnace for 60 minutes at 550°C. Natural volatile materials are chemical substances usually of animal or plant origin. Manufactured or synthetic volatile materials such as ether, acetone, and carbon tetrachloride are highly volatile and not of plant-or animal origin. Also see NONVOLATILE MATIER. Volatile Adds (water)- Fatty acids produced during digestion which are soluble in water and can be steamdistilled at atmospheric pressure. Also called organic acids. Volatile acids are commonly reported as equivalent to acetic acid. Volatile Uquids (water)- Uquids which easily vaporize or evaporate at room temperature. Volatile Matter (water)- Matter in water, wastewater, or other liquids that is lost on ignition of the dry solids at SSOOC. Volatile Solids (water)- Those solids in water or other liquids that are lost on ignition of the dry solids at sso-c. Volumetric (water~- A measurement based on the volume of some factor. Volumetric titration is a means of measuring unknown concentrations of water quality indicators in a sample BY DETERMINING 1HE VOLUME of titrant or liquid reagent needed to complete particular reactions. Volumetric Feeder (water) - A dry chemical feeder which delivers a measured volume of chemical during a specific time period. Volute (water)- The spiral-shaped casing which surrounds a pump, blower, or turbine impeller and collects the liquid or gas discharged by the impeller. Vortex (water) -A revolving mass of water which foril\S a whirlpool. This whirlpool is caused by water flowing out of a small opening in the bottom of a basin or reservoir. A funnelshaped opening is created downward from the water surface. W A S (water) - Waste Activated Sludge, mg/L The excess growth of microorganisms which musf be removed from the process to keep the biological system in balance.

GLOSSARY OF CIVIL ENGINEERING TERMS

G- 73

W, X, Y, Z Walers (water) -Horizontal shoring members, usually square, rough cut timber, that are used to hold solid sheeting, braces or vertical shoring members in place. Also called STRINGERS. Wall (const)- Member, usually vertical, used to enclose or separate spaces. Wall (const) - Vertical or near-vertical construction for enclosing space or retaining earth or stored materials. Warp (const)- Change from a straight or true plane condition Wasteline Cleanout (water) - An opening or point of access in a .building wastewater pipe system for rodding or snake operation. '«asteline Vent (water) - Most plumbing codes require a vent pipe connection of adequate size and located downstream of a trap in a building wastewater system. This vent prevents the accumulation of gases or odors and is usually piped through the roof and out of doors. Wastewater (water) - A conununity's used water and water-carried solids (including used water from industrial processes) that flow to a treatment plant. Storm water, surface water, and groundwater infiltration also may be included in the wastewater that enters a wastewater treatment plant. The term "sewage" usually refers to household wastes, but this word is being replaced by the term "wastewater." Wastewater Collection System (water) -The pipe system for collecting and carrying water and watercarried wastes from domestic and industrial sources to a was.tewater treatment plant. Wastewater Facilities (water) - The pipes, conduits, structures, equipment, and processes required to collect, convey, and treat domestic and industrial wastes, and dispose of the · effluent and sludge. Wastewater Treatment Plant (water)- An arrangement of pipes, equipment, devices, tanks and structures for treating wastewater and industrial wastes. D A water pollution control plant. Water Audit (water) - A thorough examination of the accuracy of water agency records or accounts (volumes of water) and system control equipment. Water managers can use audits to determine their water distribution system efficiency. The overall goal is to identify and verify water and revenue losses in a water system. Water Cycle (water) -The process of evaporation of water into the air and its return to earth by precipitation (rain or snow). This . process also includes transpiration from plants, groundwater movement, and runoff into rivers, sh·eams and the ocean. Also called the HYDROLOGIC CYCLE. Water Hammer (water) -The sound like someone hammering on a pipe that occm:s when a valve ' is opened or closed very rapidly. When a valve position is changed quickly, the water pressure in a pipe will increase and decrease back and. forth very quickly. This rise and fall in pressures can cause serious damage to the system. · Water Lance (water) - A pipe on the end of a water hose that is used to hydraulically jet out solids. Water Table (water) - The upper surface of the zone of saturation of groundwater in an unconfined aquifer.

G -74

GLOSSARY OF CIVIL ENGINEERING TERMS

Water vapor (const) - Creates a pressure just like any other gas. Cold air has a relatively low vapor pressure, while warm air (with larger amounts of water vapor) has a greate1 pressure. The difference in pressure cause the vapor to penetrate building materials in th€ direction from high to low v~por pressure Watersh~d

(water)- The region or land area that contributes to the drainage or catchment area above a specific point on a stream or river.

Wayne Ball (water) - A spirally grooved, inflatable, semi-hard rubber ball designed for hydraulic cleaning of sewer pipes. See BALLING and SEWER BALL. Weather (const) - To degrade under the action of the weather. Also used to describe the inclusion of a slight slope to throw off rain~ater, eg. on a sill Weathering (const) - Action of weather in producing degradation; aging 2) Alternatively used as a noun to describe a slight construction slope designed to throw off rainwater Weir (water) - A wall or plate placed in an open channel and used to measure the flow of water. The depth of the flow over the weir can be used to calculate the flow rate, or a chart or conversion table may be used to convert depth to flow. 0 A wall or obstruction used to control flow (from settling tanks and clarifiers) to ensure a uniform flow rate and avoid short-circuiting. Weir Loading (water) - A guideline used to determine the length of weir needed on settling tanks and clarifiers in treatment plants. Used by operators to determine if weirs are hydraulically (flow) overloaded. Weir, Proportional (water) - A specially shaped weir in which the flow through · the weir is directly proportional to the head. Well Isolation Zone (water) - The surface or zone surround~ a water well or well field, supplying a public water system, with restricted land uses to prevent contaminants from a not permitted land use to move toward and reach such water well or well field. Also see WELLHEAD PROTECTION AREA (WHPA). Well Log (water) - A record of the thickness and characteristics of the soil, rock and waterbearing formations encountered during the drilling (sinking) of a well. Well Point (water) - A hollow, pointed rod with a perforated (containing many small holes) tip. · A well poinl is driven into an excavation where water seeps into the tip and is pumped out of the area. Used to lower the water table and reduce flooding during an excavation. Well Protection Area (water) - The surface and subsurface area surrounding a water well or well field, supplying a public water system, through which contaminants are reasonably likely to move toward and reach such water well or well field. Also see WELL ISOLATION ZONE. Wet Oxidation (water) - A method of treating . or conditioning sludge before the water is removed. Compressed air is blown into the liquid sludge. The air and sludge mixture is fed Into a pressure vessel where the organic material is stabilized. The stabilized organic material and inert (inorganic) solids are then separated from the pressure vessel effluent by dewatering in lagoons or by mechanical means. Wet Well (water) - A compartment or tank in which wastewater is collected. The suction pipe of a ·pump may be connected to the wet well or a submersible pump may be located in the wet well. Wetted Perimeter (water) - The length of the wetted portion of a pipe or channel covered by flowing water.

GLOSSARY OF CIVIL ENGINEERING TERMS

Wholesome Water (water)- A water that is safe and palatable for human consumption. Winders (const) -Steps with tapered treads in sharply curved stairs. Wire-To-Water Efficiency (water) - The combined efficiency of a pump and motor together. Also called the OVERALL EFFICIENCY. Wobble friction (const) - In prestressed concrete, friction caused by unintended deviation of prestressing sheath or duct from its specified profile. Wrinkle (const) - Slight ridge caused by folding, rumpling or creasing. In roofing may refer to the common wrinkled pattern that forms over the joints of insulation in insulated roof systems. Similar to buckling Wye Strainer (water)- A screen shaped like the letter Y. The water flows in at the top of theY and the debris in the water is removed in the top part of theY. Wythe (const)- Each continuous vertical section of a wall one masonry unit in thickness. Yield (const) - Permanent deformation which a material undergoes when it is stressed beyond its elastic limit Yield strength (const) - Specified minimum yield strength or yield point of reinforcement in megapascals.

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GLOSSARY OF CIVIL ENGINEERING TERII

INDEX

I- 1

Index Aggregate, 1 Alignment chart, 239 Alternate design method, 357

Pt. 26,32 Balance design, 29 Bend, 11 Bond,157 Braced frame, 239 Brackets, 148 Bresler equation, 230 Bundled bars, 8, 11 Development of, 161 Coefficients for continuous beams and slabs, 39 Coefficient of resistance, 28 Columns, 185 Axial load capacity of, 187 Axial load and bending, 203 Composite, 191 Structural steel encased • concrete core, 191 Economical design, 190 Spiral, 189 Limits of reinforcement, 189 Sizes and spacing of spirals, 189 Tied, 187 Limits of reinforcement, 188 Sizes and spacing of bars, 188 Types of, 1786 Columns, eccentrically loaded Analysis of, 205 Axial plus bending in both axis, 229 Balanced loading, 207 Inter~ction diagram, 207 Columns, long, 237 Combined footing, 259

Concrete Average strength, 6 Compressive strength of, 4 Heavyweight, 3 Lightweight, 2 Modulus of elasticity of, 3 Normal weight, 3 Proportion, 2 Concrete protection for reinforcement, 9 Corbels, 148 Cracking moment, Me,, 36

Deep beams, 111 Deflection of beam, 36 Maximum permissible, 38 Development length, 157, 171 Basic concept of, i58 Basic development length, 159, 161 Bundled bars, 161 Flexural reinforcement, 161 Hooks, 167 Modification factors Tension bars, 160 Compression bars, 161 Negative mo01ent bars, 164 Positive moment bars, 162 Doubly reinforced beam, 106 Analysis of, 106 ·Steps in design of, 107 Steps in investigation of, 109 Dowels, 269

Earthquake load, 21 ·Effective length factors, 238

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IN DE)

I -2 Floati~ foundation, 259 Footing, 259 Cr~tical section, 263 Distribution of reinforcement, 265 Loads and reactions in, 262 Minimum depth of, 268 Shear in, 266 Types of, 259

Honeycomb, 1 Hooks, 11, 166 Development of, 167

• Interaction diagram, 207 Isolated footing, 259

Loads, 11 Arrangement of, 12 · Combination, 21 Dead load, 11 Live load, 12 Minimum roof loads, 14 Special loads, 14 Load factors, 21, 24 Load transfer from column to footing, 268 Long column, 185, 237 Long-term deflection 37

Mat foundation, 259 Minimum thickness of flexural members, 35 Modulus of elasticity, 3 Modulus of rapture, 36 Moment magnifier method; 240 Biaxial bending, 243 Nominal moment, 28 Normal weight concrete, 3

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One-way slab, 74 Maximum spacing of reinforcement, 74 Steps in design, 75 Overreinforced design, 29

P-delta moment, 185 Pedestal, 185 Pile caps, 259 Plastic centroid, 204

Radius of gyration, 238 Reinforcement Deformed, 7 Metal,6 Plain, 7 Spacing limits of, 8 Required strength, 21, 23

Secondary moment, 185 Shear and t~rsion, 22 Shear and diagonal tension, 125 Critical section for beam, 132 Footing, 266 Steps in vertical stirrup design, 133 Types of, 126 Shear friction design method, 148 Shear reinforcement, 130 Minimum amount of, 131 Spacing limits of, 131 Types of, 130 Shear span, 126 Shear strength provided by concrete, 127 Shear strength provided by · reinforcement, 129 Short column, 185 Short compression block, 185 Shrinkage reinforcement, 74 Singly reinforced beam, 27. Steps in desigh, 33, 34 .Steps in investigation of, 34

INDEX

Slab One-way, 74 Two-way, 335 Slenderness effects in columns, '237 Approximate evaluation of, '238 Consideration of, '239 Effective length factors, '238 Soil pressure, permissible, 261 Spacing of reinforcement, 8 Splices of reinforcement, 1567 Lap, 1568 Steel ratio p, 27, 29 Balanced, 30 Maximum,32 Minimum, 31, 32, 90 Stirrup, 129 Design yield strength, 130 Inclined, 129 Strain, .26 Strap footing, 324 Strength reduction factors, 22 Structural steel encased concrete core, 191

T-beams,87 Balanced and maximum steel area, 89 Minimum steel ratio, 90 Steps in design of, 93 Steps in investigation of, 95 With negative moment, 90 Temperature reinforcement, 74 Time-dependent factor, 37 Torsion, 128, 150 Details of reinforcement, 154 Minimum reinforcement, 1454 Spacing of reinforcement, 155 Torsional moment, 151 Trapezoidal footing, 315 Two-way slab, 335 Column and middle strips, 335 Direct design method, 338 Minimum thickness, 336

1- 3 Ultimate moment, 28 Unbraced frame, '239 Underreinforced design, 29

Wall footing, 259 Water, 1 Potable, 2 Water-cement ratio, 4 Wind load, 21 Wind pressure, 15 Pressure coefficients for, 16 Working strength, 357