Ejemlo Posta WeldedSteelTankCalcs_071713_PRINT (1)

AWWA D100 Moin - Costa Rica

Engineer: T. Tovey, PE Check: S. Goto, PE

Define Units

References 1) AWWA D100-11, IBC 2009 and ASCE 7-05 2) Basis of Seismic Provisions for welded Steel Oil Storage Tanks by Wozniak & Mitchell. 3) Steel Plate Engineering Data Vol. 1, Useful Information on the Design of Plate Structures, Steel Tanks for Liquid Storage 1982, SPFA 4) Structural Engineering Handbook, by Gaylord, 3rd Edition Chapter 27, Steel Water Tanks, by Bob Wozniak 5) ACI 318, Chapter 9 and AISC Manual of Steel Construction cone roof slope s =3/4":12"

tank diameter "D" water depth "h"

height of tank shell ="Hs"

ring wall depth "Df"

Dimensions and Design Criteria π 2 Diameter D  33.0  ft , water height h p  40  ft resulting in V   D  h p  255923.1  gal 4 R 

D 2

G  1.0

R  16.5  ft

diameter of tank and radius, ft.

specific gravity of water

Roof Snow load: pg  0  psf

Assumed snow load for Costa Rica

However, AWWA D100-11 minimum pressure for live load or snow load is 25 psf; therefore use: LL  25  psf

2/28/2013

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Wind Loads: Design wind load: from Drawing 003-S-0001 m Vdes  42   93.951  mph s

V 

Vdes mph

Cf  .60

force coef. per AWWA D100, Table 2

G'  1.0

wind gust factor (Sec. 3.1.4)

 93.951

I  1.15

wind importance factor (Sec. 3.1.4)

Soil and Seismic Factors:

Allowable bearing pressure:

f brg  200  kPa  4177.087  psf

Site Class, Sms and Sm1 values from project Geotech, Nason McCullough on 2-14-13: Soil underneath tank is to be 'vibro-compacted soil': Seismic parameters: SMS  1.0

SM1  1.0

Seismic Use Group: III

Site Class = D

IE  1.5

From Table 24 for Importance factor I  1.5 E

Design response spectra; U  .67 scaling factor This U scaling factor value should be .67 for 5% dampening Refer to IBC and to the AWWA D100 STD and eq 16-39 and 16-40 of IBC 2009. (Eqn. 13-7) SDS  U  SMS SDS  0.670 SD1  U  SM1

SD1  0.670

(Eqn. 13-8)

A v  0.14  SDS

A v  0.094

vertical acceleration per AWWA D100, Section 13.5.4.3

Tc  2  π 

D

 3.68  h p  3.68  g  tanh  D 

Tc  3.318 s

Eqn. 13-22 impulsive first mode slosh period

TL  16  sec region dependent transition period per Nason McCullough on 2-14-13 Ts 

SD1 SDS

Sai  SDS 2/28/2013

Ts  1 Sai  0.67

Section 13.2.7.3.1 Section 13.2.9.2 Ground-supported flat-bottom tanks.

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Check above formulas for application of design response spectrum for convective component Sac = design spectral response acceleration for the convective component, 0.5% damped, at the first mode sloshing wave period TC stated as a multiple (decimal) of g Tc  3.318 s K  1.5 K  SD1 Tc

TL  16 s

"1" means true

T c  TL  1

damping scaling factor, Section 13.2.7.3.2

 sec  0.303 K  SD1 Tc

K  TL  SD1

AWWA Eq 13-12

Tc

 sec  SDS  1

2

 sec  1.461

AWWA Eq 13-13

"1" means true

logic to pick design response spectrum for convective component Sac 

 K  SD1  min   sec SDS if Tc  TL  Tc    K  TL  SD1 Tc

2/28/2013

2

 sec otherwise

"Eq 13-12 Governs"

if Tc  TL

"Eq 13-13 Governs"

otherwise

 "Eq 13-12 Governs"

Sac  0.303

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Horizontal Design Accelerations; AWWA Section 13.2.9 for ground supported flat bottom tanks section 13.2.9.2 : GENERAL PROCEDURE uses equations 13-9, 13-10, 13-11 and equations 13-12 and 13-13 Select Response Modification Factors: Table 28 Response modification factors Ri and Rc Response Modification Factor Rc (convective component) -

Structure

Ri (impulsive component)

Cross-braced, column-supported elevated tank 3.0* Pedestal-type elevated tank 3.0 Ground-supported flat-bottom tank Mechanically-anchored 3.0 1.5 Self-anchored 2.5 1.5 * The response modification factor Ri for cross-braced, column-supported elevated tanks only applies to tanks with tension-only diagonal bracing. Tanks that utilize tension-compression diagonal bracing are beyond the scope of this standard.

Tank will be Ground supported, flat bottom, mechanically anchored: AWWA D100, Table 28: Ri  3

Rc  1.5

Determine Design Impulsive Acceleration: per AWWA Eq 13-17 Sai  IE

A i 

1.4  Ri

AWWA Eq 13-17; site specific procedure is based on 5 percent damped, Sai

 0.239

Determine Design Convective Acceleration: per AWWA Eq 13-18 A c 

Sac  IE 1.4  Rc

AWWA Eq. 13-18 design convective acceleration - site specific procedure

 0.216

ss  19.33

Maximum design tensile stress from Table 34

Input Table: First column is the design shell thickness. Second column is to determine height of

tank. Third column is needed for Chapter 14 tank steel strengths if different strength steels are used at different shell courses.

.3125  .3125  .375 tt    .375   .5   .5 2/28/2013

5 ss  8 8 8 8 8

 0.313 ss  0.313   ss   0.375 ss  0.375   0.5 ss    0.5 ss  

5 19.33 



8 19.33  8 19.33 



8 19.33  8 19.33 

n  rows ( tt)

n6

number of shell courses



8 19.33 

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  2 w  submatrix  tt 1 n 1 1   ft 1 t  submatrix tt 1 n 1 1  in

Hs 




shell course thk. shell course width total shell height of tank

w Hs  45 ft

Summary of Allowable stresses for chosen weld joint efficiency; E  1 Allow.

Allow. Shell

Shell

Stress times

5.0

Stress, ksi 19.33

E, ksi 19.33

0.3125

8.0

19.33

19.33

3

0.375

8.0

19.33

19.33

4

0.375

8.0

19.33

19.33

5

0.5

8.0

19.33

19.33

6

0.5

8.0

19.33

19.33

Shell Course

Shell Thickness

Shell

(in)

Width (ft)

1

0.3125

2

(from top)

Static & Dynamic Analysis Prgm

Static & Dynamic Shell Summary; Req'd

Shell

Shell

Course

Dynamic

Shell

Thick., in Shell

(from top)

Req'd

Static

Static Thick., in.

Stress, ksi

Shell Thick., in

Dynamic

Impulsive

Shell

Hoop Force, Hoop Force,

Stress, ksi Ni, lbs/in

Convective Nc, lbs/in

Hydrostatic Hoop Force, Nh, lbs/in

1

0.31

0.19

2.28

0.02

3.30

131

132

429

2

0.31

0.19

5.93

0.06

7.57

280

54

1115

3

0.38

0.19

9.59

0.09

11.70

353

22

1802

4

0.38

0.19

13.24

0.11

15.57

362

9

2488

5

0.50

0.19

16.89

0.14

19.43

362

4

3175

6

0.50

0.20

19.33

0.17

21.95

362

3

3861

The tank manufacturer will design the roofing system and rafter spacing. Estimated roof wt. estimated_roof_unitwt  15  psf W r  estimated_roof_unitwt  h' 

 D  12  2 

.75

2/28/2013



π 4

2

D

W r  13  kip

total roof DL

h'  12.375  in roof rise

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Sloshing of Water in Tank: 13.5.4.4 The freeboard provided shall meet the requirements of Table 29, unless otherwise specified. The sloshing wave height shall be determined by the equation; note SD1  0.67 and SDS  0.67

Sloshing calculations: A c  0.216 Tc  3.318 s

A f 

Convective and impulsive design accelerations

A i  0.239

Since Tc is less than T.L, equation 13-55 applies for Seismic Use Group III

K  SD1 Tc

 0.303

Convective design acceleration for sloshing

sec

Eqn 13-52

d  .5  D  A f  4.998 ft

Minimum freeboard for Seismic Use Group III is: per AWWA D100, Table 29 (min freeboard =d)

Freeboard  5  ft

Detailed Prgm. to Analyze Each Shell Course (not currently in AWWA). Determine convective & impulsive water weights and moment arms around tank base; calc moments for both tank shell (EBP=excluding bottom pressure) & slab foundation (IBP=including bottom pressure); determine shell wt., roof wt., shears, moments and slosh height; D  33  ft and hTank  ft p  40 Moments & Shears Prgm

Summary of Tank Moments & Shears; Shell Course (from top)

Accum. Sum of

Shell

Slab

M oment,

M oment,

432

kip*ft 20

kip*ft 20

67

67

Shear, kips

1

Shell wts., 7

2

17

434

3

30

437

646

662

4

43

440

1462

3045

5

60

444

4550

6525

6

76

448

8047

10076

M slab  max ( g')  kip  ft Fy  36000 2/28/2013

M slab  10076  kip  ft

ASTM A36 yield stress

6 of 17



The following program determines the vertical shell buckling stress and required shell thickness of each shell course (not in AWWA D100) Vertical Buckling Prgm.

The following program determines effective shell stress and required shell thickness of each shell course based upon principle dynamic hoop stress (tension) and vertical stress (compression) using Henky Von Mises Eqs. σe =

σx2  σx σy  σy2 (not req'd by AWWA)

Effective Stress Prgm.

The following programs determine greater of static, dynamic, vertical buckling, effective stress (not req'd by AWWA) or 1/4" min. shell thickness for each shell course (this departs from AWWA); pick greatest for req'd design; compare existing shell thickness to required design shell thickness..."OK" if exst. is greater than design; determine order of equations used to solve for max. wall thickness Shell Thickness Summary Prgms

Shell Summary Table; Shell Course

Shell Thick

(from the top)

(in)

Req'd Shell

Shell Course

Req'd Shell

Wt (kips)

Thickness (in)

Course Wt ( Status

Governing Condition

kips)

1

0.31

6.6

0.25

5.3

OK

1/4" min.

2

0.31

10.6

0.25

8.5

OK

1/4" min.

3

0.38

12.7

0.25

8.5

OK

1/4" min.

4

0.38

12.7

0.25

8.5

OK

1/4" min.

5

0.50

16.9

0.25

8.5

OK

1/4" min.

6

0.50

16.9

0.29

9.8

OK

Vert. Buckling

Tank Wind Base Shear and Overturning Moments;

Pw  q z GC f  30C f

V  93.951 mph

q z  0.00256 K z IV 2

AWWA Eq. 3-1

AWWA Eq. 3-2

Wind Pressure Prgm

Tank Base Wind Shears and Overturning Moments Summary; D i st ance t o G r o und , ft 4 6 .0 4 5.0 4 0 .0 3 2 .0 2 4 .0 16 . 0 8 .0

2/28/2013

Kz

qz, p sf

Exp o sur e D Pw , F, ar m, p sf kip s ft

1.2 7 1.2 7 1.2 7 1.2 7 1.2 7 1.2 7 1.2 7

3 3 .0 3 3 .0 3 3 .0 3 3 .0 3 3 .0 3 3 .0 3 3 .0

19 .8 19 .8 19 .8 19 .8 19 .8 19 .8 19 .8

0 .3 3 .3 5. 2 5. 2 5. 2 5. 2 5. 2 2 9 .7

4 5.3 4 2 .5 3 6 .0 2 8 .0 2 0 .0 12 .0 4 .0

M o ment , ki p * f t 15. 3 13 8 .9 18 8 .2 14 6 .4 10 4 .6 6 2 .7 2 0 .9 6 76 . 9

7 of 17


Kz

qz, p sf

Exp o sur e D Pw , F, ar m, p sf kip s ft

1.2 7 1.2 7 1.2 7 1.2 7 1.2 7 1.2 7 1.2 7

3 3 .0 3 3 .0 3 3 .0 3 3 .0 3 3 .0 3 3 .0 3 3 .0

19 .8 19 .8 19 .8 19 .8 19 .8 19 .8 19 .8

D i st ance t o G r o und , ft 4 6 .0 4 5.0 4 0 .0 3 2 .0 2 4 .0 16 . 0 8 .0

0 .3 3 .3 5. 2 5. 2 5. 2 5. 2 5. 2

4 5.3 4 2 .5 3 6 .0 2 8 .0 2 0 .0 12 .0 4 .0

2 9 .7


M o ment , ki p * f t 15. 3 13 8 .9 18 8 .2 14 6 .4 10 4 .6 6 2 .7 2 0 .9 6 76 . 9

Exposure D: values from table above Vw  26.5  kips

M w  536.4  kip  ft Pw

Check AWWA Eq 3-36 for Intermediate Wind Girders; P   19.802 aw psf D tank dia. D  D  33 tt  .3125 top shell course thickness ft h' 

10.625  106  tt

D Paw     tt 

Conclusion:

1.5

h'  154.52

allowable height, ft., of tt  0.313 plate between intermediate wind girders or boundaries

tt  0.313 " shell course height Hs  45  ft is less than h'  154.52 ft total

height calculated; therefore intermediate wind girders are not req'd for this shell area. Intermediate Wind Girder Prgm

Check tank stability for Seismic overturning to determine seismic loads would require anchor bolts. Hs  45  ft and D  33 The equations apply to self anchored tanks only (where J<.785) and do not apply to mechanically anchored tank.

Tank Base Seismic Moments & Shears Summary; Ground Supported Flat Bottom Tank

Ri

Rc

Ai

Ac

M s, kip*ft

Vf, kip

Ground Supported Flat Bottom Tank, M echanically

3

1.5

0.239

0.216

8047

450

Ground Supported Flat Bottom Tank, Self Anchore

2.5

1.5

0.287

0.216

9485

537

RESISTANCE TO SEISMIC OVERTURNING NEEDS TO BE CHECKED NOW. Resistance is either provided by designing a self anchored tank where J< 0.785 or anchoring the tank. First check to see what is required if you use a Self Anchored Tank. Ms_a  8047  kip  ft

2/28/2013

Moment for Mechanically Anchored Tank

8 of 17



Moment for Self-Anchored Tank

Ms_sa  9485  kip  ft

Check using tank bottom thickness = 1/4 inch then use thicker tank bottom thickness until J<0.785. try using tank bottom thickess = 1/2 inch or more if 1/4 inch thickness does not work. Refer to Table below that shows solutions for varying annular ring thicknesses 1 tb   in 2

assumed yield stress of bottom annular ring, psi

Fy  36000

.216 

tb in



Annular Ring thickness (minimum 1/4" permitted by AWWA); but not to 1 exceed the bottom shell course of tn  0.5  in and  in  tb  tn  1 4

Fy H ft

 ft  4.207

G

A  ft

0.5

s .035  D  1.155

0.5

lb

logic to select lesser value for minimum width of bottom annulus per Eq. 13-38

 tb L  min  .216   in    wL  0

ws 

Ws π  D  ft

  ft .035  D  ft Hs  G  ft  Fy

L  1.155  ft

Width of bottom annulus

max. weight of tank contents that may be used to resist tank uplift, lbs/ft for a mchanically anchored tank

ws  738 

lbf ft

weight of tank shell, lbs/ft

Weight of portion of tank roof that bears on tank shell, lbs/ft. Use 1.5 factor to account for weight of rafters and girders in addition to assumed roof weight of:

wr 

Wr π  D  ft

wt  ws  wr

2/28/2013

estimated_roof_unitwt  15  psf  1.5  185.625  plf

wt  923 

lbf ft

Estimated weight of tank shell & roof, lbs/ft, Eq. 13-41

9 of 17


wt 

wt lbf

unit wt. of shell & portion of roof, lbs/ft

wt  923

ft

wL  0


max. resisting wt. of tank contents, lbs/ft

AWWA D100, 13.5.4.1...

1. The resisting force is adequate for tank stability when the overturning ratio J determined by Eq 13-36 is less than 1.54. The maximum width of annulus for determining the resisting force is 3.5 percent of the tank diameter D. 2. The shell compression satisfies Sec. 13.5.4.2. 3. The required thickness of the bottom annulus tb does not exceed the thickness of the bottom shell ring per Sec. 13.5.4.1.2.4. 4. Piping flexibility requirements of Sec. 13.6 are satisfied. 5. For tank stability there are 3 conditions; 1) For J < 0.785 there is no shell uplift due to the overturning moment and the tank is self-anchored. 2) For 0.785 < J < 1.54 there is shell uplift, but the tank is stable provided the shell compression requirements of Sec. 13.5.4.2 are satisfied. 3) For J > 1.54 the tank is not stable. Modify the bottom annulus, within the limits of tb and L, or provide mechanical anchors. The CH2M HILL policy permits self anchored tanks only if J<0.785. Ms_sa

J 

ft  lbf 2



J  9.802



D  wt  1  0.4  A v  wL  

Stability 

"No uplift"

if J  .785

AWWA Eq. 13-36 Overturning ratio

Stability  "Must Anchor Tank"

"Uplift" if .785  J  1.54 "Must Anchor Tank"

Conclusion:

2/28/2013

since J  9.802

otherwise

tank will uplift and needs to be anchored.

10 of 17



Annular Ring Prgm

AWWA D100, Section 13.5.4.2.2: Longitudinal shell compression for mechanically anchored tanks shall be determined by eqn 13-39: wt  923.177

A v  0.094

Ms_a     1.273  ft  lbf  1  σc  wt  1  .4  A v    psi  1727.409 psi   2 t n D   12 





σc  1727  psi

in

Allowable buckling stress per Eq. 13-48 for Fy  36000 ; FL 

t_Rc 

and t'  tn or t'  0.5  in

.0031088 if 25000  Fy  34000

R  16.5 ft

 psi

.0035372 if 34000  Fy

 R 

t'   t'  17.5  105   1  50000   

2

t'  if  t_Rc  R R 

AWWA Table 9 FL  5828  psi

t' if t_Rc   .0125 R

 t'   if 25000  Fy  34000 R

5775  738  103  

 t'   otherwise R

6925  886  103   otherwise

15000 if 25000  Fy  34000 18000 otherwise

Allowable shell stress per Eq 13-48 for mechanically anchored tank: σa  FL  5828.229 psi

Conclusion:

σe  1.333  σa  7769.03 psi

maximum longitudinal shell compression stress at bottom shell

course : σc  1727  psi is less than σe  7769  psi <--- OK

2/28/2013

11 of 17



Anchor Bolt Design AWWA D100-11, Section 3.8.5.1 Anchor bolts requirements: 1. When exposed to weather, a corrosion allowance of 1/4 in. (6.35 mm) shall be applied to the root thread diameter of anchor bolts less than 1 1/4 in. (31.8 mm) diameter. 3. The minimum anchor bolt diameter shall be 1 in. (25.4 mm). 4. Anchor bolt embedment shall terminate in a head, nut, washer plate, or U-bolt. 5. For ASTM A193, Grade B7 bolts, lock nuts shall be provided. 6. Anchor bolt project above foundation shall be specified to provide a 2-in nominal projection of the threaded ends of the anchor bolts above the design elevation of the tops of the anchor-bolt nuts (or lock screws.) M  Ms_a

M  8047  kip  ft

Seismic base moment

M w  536  kip  ft Wind base moment

lbf wt  wt  ft

wt  0.923 

W'  π  D  ft  wt

kip ft tank shell wt. plus roof DL on shell

W'  96  kip

Net Tensile Area, AISC Table 7-17 for 1.25" diameter bolt: ASTM A193, Grade B7 bolts 2

d  2.0  in

A b 

π 4

d

2

A net  2.5  in

2

A b  3.142  in

Number of anchors:

SL 

π  D  ft nbolt

anchor bolt gross area per AISC

nbolt  20

 5.184 ft

D  33

Anchor bolt spacing (max spacing = 10')

Allowable anchor bolt stress per AWWA D100, Chapter 3, Table 5: AWWA D100, Section 3.3.3:

Seis  1.33

Pallow  A net  1.33Ft  103.9  kip Dac  D  ft  4  in 2/28/2013

Dac  33.33 ft

Ft  31.25  ksi

Seismic increase allowed

Allowable tensile load per bolt assumed anchor bolt circle diameter

12 of 17



Seismic Anchorage; Pas 

4 M nbolt  Dac



W' nbolt

Pas  43.5  kip

Seismic anchor bolt load perAWWA Eqn. 3-42

Pallow  103.9  kip OK

Wind Anchorage; Paw 

4  Mw nbolt  Dac



W' nbolt

Paw  1.57  kip

Wind anchor bolt load perAWWA Eqn. 3-41; per 3.8.9.1 Wind anchorage is not required

Anchor Bolt Chair Design: Steel Plate Engineering Data Vol. 2, Useful Information on the Design of Plate Structures, Anchor Bolt Chairs 1985, SPFA

R  16.5 ft

tank radius, in

d  2  in

bolt diameter

Pas  43.5  kip Load on ASTM A193, Grade B7 bolt emin  4  in

assumed min. eccentricity of load, based geometry of anchor chair

t  tn

t  0.5  in

tank shell thickness at bottom course

g  d  1  in

g  3  in

distance in between vert. plates

a  g  4  in

a  7  in

assumed width of chair to accomodate use of hydraulic bolt tensioner (clearance between tank shell and bolt)

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1 assume jmin =  in 2

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m  tb

m  0.5  in


assumed bottom or base plate thickness

Assumed height of chair, in (max. is 3  a  21  in)

h  18  in σ  1.33  20  ksi

σ  26.6  ksi

Allowable local stress per AWWA D100-11, 3.8.6.1...The allowable local shell or pedestal stress

for the design uplift case shall be 20,000 psi (137.9 MPa) plus the permissible increase for wind or seismic loads (1.33), if applicable.

Shell Thickness Prgm.

Conclusion:

Shell thickness:

Req'd shell plate thickness for chair; tmin  0.38  in

t  0.5  in

OK

Check top plate thickness using Steel Plate Engineering Data Vol. 2, eqn 45: Pas  43.5  kip

S  σ S  26.6  ksi

d  2  in

f 

 

b   d 

1 4

d 2



1 8

 in f  1.125  in

 

 in  2  4.5  in

emin  2  8  in

Exx  60ksi

weld filler metal strength assumed

Top plate length

1 2

 Pas  c   ( .375  g  .22  d)  S  f   0.998  in  c 1    in  in 8 

c  Ceil 

c  1  in

jmin  max [ .5  in .04  ( h  c) ]

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top plate thickness

top plate thickness roundedup to nearest 1/8"

jmin  0.68  in

Min side plate thickness

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Find req'd shell plate thickness, height of chair, top plate width, top plate depth, top plate thickness, stiffener thickness, and fillet weld sizes using Eqs 45-51, Z 

1.0  in .177  a  m

 m

 0.941

2

(Eqn 47)

  1.0  in t   Rt

Sv 

Pas  e 2

t





1.32  Z



  1.43  a  h 2 2  4 a h   Rt



1



   21487102.878  pcf R  t   

.031

3

(Eqn 46)

Vertical and horizontal loads on weld: eqns 49, 50, 51 W v 

Pas ( a  2  h)

W weld 

 1.012 

kips

W H 

in

Pas  emin a  h  .667  h

kips 2 2 W v  W H  1.132  in

2

 0.509 

kips in

Total load on weld, klf per inch of weld

Strength of 1/4" fillet weld assuming E60 electrode:

 2 1 kips    in  3.182   2  4 in

Fweld  .30  60  ksi  

W weld  1.132 

kips in

OK

Summary - Anchor Bolt Chair Dimensions Chair Height:

h  18  in

Top plate width

a  7  in

Top plate length

b  4.5  in

Top plate thickness

c  1  in

Vertical side plate thickness

jmin  0.68  in

Min req'd shell thickness

tmin  0.38  in

2/28/2013

Use 3/4"

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Type 1, Ring Wall Foundation Hoop Reinforcement; see Structural Engineering Handbook, by Gaylord, 3rd Edition Chapter 27, Steel Water Tanks by Bob Wozniak strength reduction factor for tension per 9.3.2.1

ϕ  .90

ACI 318, Eqs. 9-6 where H is load due to soil & water pressure

U = .9  D  1.6  W  1.6  H ft

tank diameter

q  γw  h

q  93.37  psf

D  33

h p  40 ft water height pressure

Ko  .50

assumed at rest lateral soil pressure

f y  60  ksi

grade 60 reinforcing yield stress

Df  4.0  ft

height of ring wall

b  5  ft

width of ring wall

1

T 

2

A s 

 Ko  Df  D  ft  q 1.6  T

tension in ring wall (unfactored)....see Gaylord ref. above pg. 27-4 Eqs. (6)

T  3.081  kip

required cross sectional area of hoop reinforcement per ACI 318, 9-6

2

A s  0.091  in

ϕ  fy

Minimum temperature and shrinkage steel: 2

A st_min  0.003  12  in  Df  1.728  in b  5 ft

No_6     No_8 

Steel per foot of width ringwall

2

b  A st_min  8.64 ft  in

 .44  2    in 0.79 

areas of #6 & #8 bars

Try 4 bars T& B and 3 bars on EF: 14 bars total

2

2

A st  12  .79  in  9.48  in

Use twelve #8 bars o.c. with #5 ties at 12" o.c.

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Ring Wall Bearing Pressure: wt. of concrete ring wall:

wt_ring  Df  b  γc

wt_ring  3.000 

wt. of tank shell & portion of roof bearing on shell;

wt  0.923 

wt. of water over portion of ring wall (assume width is

b 2

kip ft

kip ft

 30  in)

b kip wt_water  h p   γw wt_water  6.225  2 ft

 wt_ring  3.000      kip  wt   0.923     6.225  ft  wt_water   

static bearing pressure;

A  b

total wt. on ring wall base

P' 

A  5

 ft

 wt_ring     wt    wt_water 

2

3

I  π  R  b

 σtoe     σ   heel 

I  70562 ft

 P' M'     S A   P' M'     S  A

4

P' σstatic  A

ft

seismic bearing pressure; assume M'  Ms_a

c  R

 σtoe  3911        psf σ   148   heel   σtoe     b  19556.3   lbf σ   739.5  ft  heel 

P'  10.148 

kip ft

σstatic  2030  psf

M'  8047  kip  ft

c  16.5 ft

S 

I c

S  4276  ft

3

toe & heel pressures are positive f brg  4177  psf

OK

unit footing loads

Conclusion: The computed positive pressure (see above) on both the anchor bolt tension side of the tank and the anchor bolt compression side of the tank indicates uplift due to seismic (this analysis based on overall tank moments). The rectangular footing is considered by contractors to be less expensive since it can be placed in one pour and stem wall forming is not required extra.

2/28/2013

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Ejemlo Posta WeldedSteelTankCalcs_071713_PRINT (1)

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