Foundation Design Calculation of Tower Type 2DT6 For Soil Category-2
1st Subm.
17-Apr-11
Md. Giasuddin
Submission Status
Date
Designed By
Description
Approved By
EMPLOYER :
CONTRACTOR :
POWER GRID COMPANY OF BANGLADESH LTD.
SANERGY CO.
NAME OF PROJECT :
DESIGN-BUILD AND TRUNKEY CONTRACT FOR CONSTRUCTION OF 230kV BIBYANA COMILLA TRANSMISSION LINE (LOT-3) AUTHORITY DESIGNED BY CHECKED BY APPROVED BY
NAME & SIGN Md. Giasuddin Md. Giasuddin
DATE 17-Apr-11
SUBMISSION SOUGHT For approval For construction As Built
Paper Size
Language
Total Sheets
A4
English
13
Scale :
N/A
Revision 1st Sub.
Document No. : PGCB/230kV/TL/B-C/Lot-3/Des.Cal/Local/08
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) Contents
Page No.
1. General.
03
1.1 Foundation Loads
03
1.2 Geotechnical Information
03
1.3 Foundation Strength Factors
03
1.4 Factored Foundation Loads
03
1.5 Codes & Standards Considered
03
1.6 Material Properties
03
1.7 Geometrical Data of the Tower 2DT6
03
1.8 Layout Plan Of the Foundation
04
2. Residual Shear Calculation
04
3. Foundation Geometry
05
4 : Design Calculation for Pile
05
4.1 - Pile Design Load Against Compressive Load
05
g Load oad Against ga Up 4.2 - Pile Design Uplift
05
4.3 - Minimum Length of Pile Group Against Uprooting
05
4.4 - Check for pile head deflection
06
4.5 - Ultimate Stress on Pile Section
07
Section-5 :Structural Design of Chimney & Pile Cap
07
5.1 - Design of Chimney
07
5 2 - Design 5.2 D i off Pile Pil Cap C
08
5.2.1.- Check Punching of cleats
08
5.2.1.a Check For Compression
08
5.2.1.b Check For Uplift
08
5.2.2 - Check cap thickness for Flexural Shear
08
5.2.3.- Check for position of Piles
08
5.2.4 - Check for Bending Moment
09
5.2.5 - Reinforcement Calculation
09
5.2.5.1 - Bottom Reinforcement
08
5.2.5.2 - Top Reinforcement
09
5.2.5.3 -Vertical Reinforcement Around The pile cap
09
5.2.5.4 -Horizontal Reinforcement Around The pile cap
10
6 - Structural Design of Pile
10
6.1 Design of upper segment of pile
10
6.1.1 Design for Compression Plus Bending
10
6.1.2 Design for Tension Plus Bending
10
6.2 Calculation to Find Point of Zero Moment in the Pile
10
Annexure-1
12
Annexure-2
13
Giasuddin
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 1. General. The objective of this generic design is to compute loads on individual pile top, length of fixity of pile and is to design pile, pile cap and chimney. If not mentioned otherwise, values with suffices x, y and z indicate three global directions with outward positive. 1.1 Foundation Loads :
Ultimate Loads Along Global Direction ( Pull and Thrust Vertical) Items
Fz ( kN )
Fx (kN)
Fy (kN)
Max Compression Case
3154.98
893.33
831.62
Max Uplift Case
2840.17
893.33
831.62
1.2 Geotechnical Information: Angle of Int. Friction, ø = 32 Degree Soil Density = 18 kN/Cum. Soil Submerged Density = 8 kN/Cum. Frustum angle = 15 Degree; As per techinical specification 1.3 Foundation Strength Factors : Strength Factor
Applied Loading Case
2DL, 2DL 2D1
2D25, 2D25 2DT6
1.23
1.35
For All Load Cases
1.4. Factored Foundation Loads. Factored Loads by using Foundation Strength Factor from Appendix (7.A2),Volume 2 of 3
Factored Ultimate Loads Along Global Direction ( Pull and Thrust Vertical) Items
Fz ( kN )
Fx (kN)
Fy (kN)
Max Long. Case in Comp.
4259.22
1206.00
1122.69
Max Long. Case in Uplift
3834.23
1206.00
1122.69
1.5 Codes & Standards Considered : ACI BS 8110 1.6 Material Properties and Clear Cover : 28 days cube strength of concrete for Pile; fc' = 30 Mpa. 28 days cube strength of concrete for Pile-Cap; fc' = 25 Mpa. Corresponding cylinder strength of concrete for Pile-Cap; fc' = 21.25 Mpa. Yield Strength Reinforcing Steel ;fy = 415 Mpa. Concrete Clear Cover at top and sides of Cap & Column is = 50 mm. Concrete Clear Cover for sides of Pile is = 75 mm. Unit Weight of Concrete = 24 kN/Cum. 1.7 Geometrical Data of the Tower 2DT6 : Face Slope = Ø = 13.306 Degree. Diagonal Slope = Ø = 18.493 Degree.
Md. Giasuddin
Page 3 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 1.8 Layout Plan Of the Foundation
1800
450
450
1800
1800
450
1800
900
450
1800
900
450
1800
900
4500
900
4500
1800
450
1800
450
450
4500
4500
CP
1800 900
450
450
1800
900
1800
900
4500
4500
900
1800
450
4500
450
4500
450
1800
1800
450
450
1800
1800
450
Layout Plan of Foundation
2. Residual Shear Calculation :
Items
Vertical Loads Fz ( kN )
Leg Shear ( kN ) = Fz*Tan Fxleg
Fyleg
Residual Shear ( kN ) Fx (kN)
Fy (kN)
FxRes = Fx-Fxleg
FyRes = Fy-Fyleg
Max Compression Case
4259.22
1007.31
1007.31
1206.00
1122.69
198.69
115.38
Max Uplift Case
3834.23
906.80
906.80
1206.00
1122.69
299.20
215.89
Md. Giasuddin
Page 4 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 3. Foundation Geometry : Size of the column = 900 mmX900 mm. Dia of the Pile, Dp = 600 mm. h'' = 280.5 mm. h' = 400 mm. f = 300 mm. Pile Center to center Distance = 1800 mm. Height of column, h = 700 mm. Length/Width of the Cap, L/B = 4500 mm. Cap Thickness, t = 1250 mm. No. of Pile Per Leg = 8 Nos Weight Calculation Weight of Column, Wcol = 13.61 kNs.
Foundation Layout Detail
Typical Pile Cap Section
Weight of Pad, Wpad = 607.5 kNs. Weight of Superimposed Soil, Ws =109.35 kNs. Bouyant Weight of Column, W'col = 7.94 kNs Bouyant Weight of Pad, W'pad = 354.38 kNs Bouyant Weight of Superimposed Soil, W's = 48.6 kNs
Loads on Pile top : For Maximum Comp. Resultant Compressive Load = Rzc =Fz+ 1.35*(Wcol+Wpad+Ws) = 5157.69 kNs. Moment Mx = Moment for Leg and Residual Shear = Fxleg*0.0 + FxRes*(t+h+h''-0.15) =376.12 kN.m Moment My = Moment for Leg and Residual Shear = Fyleg*0.0 + FyRes*(t+h+h''-0.15) = 218.41 kN.m For Maximum Uplift : Resultant Uplift = Rzt=Fz - W'col - W'pad - W's = 3423.31 kNs Moment Mx = Moment for Leg and Residual Shear = Fxleg*0.0 + Fxres*(t+h+h''-0.15) = 566.39 kN.m Moment My = Moment for Leg and Residual Shear = Fyleg*0.0 + Fyres*(t+h+h''-0.15) = 408.68 kN.m 4 : Design Calculation for Pile : Reaction of pile with applied vertical loads and biaxial bending moment can be expressed by the following equation:
RV =
R V M x *d1x M y *d1y ± ± 8 ∑ dix 2 ∑ diy 2
Where , d1x and d1y denote the distances from pile center to cap center along X or Y Direction. In this case d1x=d1y= 0.9 m.
∑
dix
2
∑
diy
2
6*1.8^2 = 19.44 Sqm.
4.1 - Pile Design Load Against Compressive Load : Maximum compresive load that a pile will be imposed can be expressed by : So Rcmax = 699.76 kNs.
R Cmax =
( Pile weight is to be considered during Pile schedule)
R zc 8
M x *d1x ∑ dix 2
M y *d1y
∑ diy
2
4.2 - Pile Design g Load Against g Uplift p : Maximum compresive load that a pile will be imposed can be expressed by : So Rtmax = 518.2 kNs.
R Tmax =
( Pile weight is to be considered during Pile schedule)
R zt 8
M x *d1x ∑ dix 2
M y *d1y
∑ diy
2
4.3 - Minimum Length of Pile Group Against Uprooting : Soil body to Resist Uplift Say minimum length of pile =8 m Depth of pile, d = 9.625 m. So a = d/2 = 4.813 m. The base size of the soil frustum at the lowest point b' = 4.2m X4.2 m The base size of the soil frustum at Mid Height ; b =4.979 m X4.979 m Average Area = (4.2^2+4.979^2)/2 =21.22 sqm.
Md. Giasuddin
Page 5 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) So Frustum Volume = 21.22 * 4.8125 =102.12 cum The upper soil volume = 4.979^2*4.813= 119.32 cum
GL
Total soil Volume = 221.44 Cum Total weight of soil body = 221.44*8=1771.52 kN Skin resistance of pile group is Given by :
Qsu =2 * ( L
B) * H * f s
Where L and B are the overall length and width of pile group, H is the depth of soil block and f s is the unit skin friction
a
1 K p Tan 2 s d
which is given by fs
Ks =1 ;( soil to soil co-efficient of earth pressure) Pd= d,
= = 32 Degree
y = Submerged Density of soil = 8 kN/Cum. Pd =8 8 *9 9.625 625 = 77 kNs kNs. So fs = 24.06 kN/Sqm. L= B = b' = 4.2 m and H = d = 9.625 m. So Qsu = 3890.5 kNs
L
d
b
Ultimate uplift capacity of pile group = Skin Resistance + Submerged Weight of soil body = 5662.02kNs. Allowable capacity (FS=1.5) = 3774.68 kNs Resultant Uplift = 3423.31 kNs. Which is less than 3774.68 kNs So OK.
a
4.4 - Check for pile head deflection: For Max Compression: Fx = Leg Shear = 1007.31 kN Fy = Leg Shear = 1007.31 kN Passive resistance by Cap Only ( Same in x and y face)
Passive resistance by Pile Cap is
1 k p γ*(1.55+0.30)*1.25*4.5 γ*(1 55+0 30)*1 25*4 5 = 2
Where k p = Co-efficient of passive earth pressure =
1+sin 1-Sin
135 47 kN 135.47
3.25
γ=Submerged density of soil =8 kN/Cum.
b' GL 300
Net Fx = Leg Shear = 871.84 kN Net Fy = Leg Shear = 871.84 kN
Cap Top
Vres=Sqrt.(871.84^2+871.84^2)=1232.97 kN Lateral Load carried by a single Pile = 154.12 kN For Max Uplift:
1250
Fx = Leg Shear = 906.8 kN Fy = Leg Shear = 906.8 kN Net Fx = Leg Shear = 771.33 kN Net Fy = Leg Shear = 771.33 kN Vres=Sqrt.(771.33^2+771.33^2)=1090.83 kN Lateral Load carried by a single Pile = 136.35 kN
Cap Bot.
Design shear carried by a single Pile Qmax = 154.12 kN For fixed head pile depth of fixity is given by
Lf/T = 2.15; (Ref. to figure no 2 , appendix C of IS: 2911) For fixed head piles .
Where, T Where ; E
5
EI K1 and
4700 I
fc ' d4 64
Kp h
Passive Pressure on Cap
K1 = 0.146 For Submerged Medium Dense Sand 25742.96 Mpa = 257430 kg/sqcm. 636172.5 cm4
EI = 163769889855 kg.sqcm.
So T = 257.03 cm = 2.57 m So depth of fixity, Lf = 5.53 m Deflection, Y = Q*(Lf)^3/12EI = 1.326 cm. = 13.26 mm; Which is less than 25mm, So OK.
Md. Giasuddin
Page 6 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 4.5 - Ultimate Stress on Pile Section For Max Compression For fixed head long pile : Moment M=m.MF = 0.82*Q*Lf/2 = For Max Compression M = 349.44 kN.m For Max Uplift M = 309.15 kN.m For Max Compression. Q = Hu = 154.12 kN. So Mu = 349.44 kN.m For Max Uplift Q = Hu = 136.35 kN. So Mu = 309.15 kN.m Ultimate loads on Single Pile : Compressive load = Rc = 699.76 kN Uplift load = Rt = 518.2 kN For Max Compression ultimate Moment , Mu = 349.44 kN.m For Max Uplift ultimate Moment , Mu = 309.15 kN.m Section-5 : Structural Design of Chimney & Pile Cap 5.1 - Design of Chimney : Ultimate Compression = 4259.22 kN 50% of Ult. Compression = 2129.61 kN Residual shear : Fxmax = 299.20 kN Fymax = 215.89 kN Resultant Fxy = 368.96 kN
1 of 12 of dia. 20 mm
y 0.793 = 292.6 kN.m. M = Fxy* Pu = 2129610.00 N Mu = 292582755.1 N.mm D = 900.00 mm b = 900 mm d' = 66 mm d'/D = 0.073 mm fck = 25.0 Mpa fy = 415.0 Mpa
Pu/fckbD = 0.105 Mu /fckbD2 = 0.016 For the above values, graph ( see annexure-1 ) shows that no rebar is needed. As per Code Min Rebar Required = 0.004*900^2 = 3240 mm2 Consider Bar Dia. 20 mm
Column Section
Provide 12 nos 20mm dia. Embedded Length of Rebar. C Compression i tto b be resisted i t db by th the rebars b iin chimney hi =F Fz = 2129 2129.61 61 kN Total Nos. of reinforcement is 12 of dia 20 12mm. As per BS 8110, Ultimate bond stress in compression bars uu is given by : uu=0.5√fc' Mpa
Development length l d
is given by : l d =
Fs ;where∑ o is the total perimeter of all rebars, Fs=Fz uu ∑ o
So Uu = 2.3 Mpa. So Development length ld required = 1228 mm.
Cap thgickness is = 1250 mm and Clear Cover at bottom = 75 mm Let Chimney rebar rest on the bottom mesh of cap. So Embedded length provided = 1250-75-32 = 1143 mm which is more than requirement, so Ok.
Md. Giasuddin
Page 7 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 5.2 - Design of Pile Cap : 5.2.1.- Check Punching of cleats: 5.2.1.a Check For Compression: Ultimate Compression = 4259.22 kN Compression to be carried by cleats = 50% of Comp.= 2129.61 kN Consider 4 cleat group with 4 three cleats in each group. The size of cleats is 150X150X20 ; length 160 . Load Carried by each Cleat =0.5* Ccomp./16 = 133.1 kN The Capacity P of each cleat is given by :
P
1.19 f 'c b(t
x / 2)
r
Where , b = Length of Angle Shear Connector = 160 mm
1/ 2
x
t = Thickness of Angle Shear Connector = 20 mm
⎡ Fy ⎤ t⎢ ⎥ 1 19 f 'c ⎦ ⎣1.19
w r
t.
r = Radius of fillet = 40 mm w = width of angle shear connector = 150
( Ref. : Art.7.6.2, Design of Latticed Steel Transmission Structures; Published by The American Society of Civil Engineers) x = 68.19 mm;
So P = 537.47 kN
>133.1 kN So OK .
5.2.1.b Check For Uplift: Ultimate Uplift = 3834.23 kN Consider 4 cleat group with 4 three cleats in each group. The size of cleats is 150X150X20 ; length 160 . Load carried by each cleat = 239 239.64 64 kN
The Capacity P of each cleat is given by :
P
1.19 f 'c b(t
r
x / 2)
Where , b = Length of Angle Shear Connector = 160 mm t = Thickness of Angle Shear Connector = 20 mm
1/ 2
x
⎡ Fy ⎤ t⎢ ⎥ ⎣1.19 f 'c ⎦
w
r
x = 68.19 mm;
t.
r = Radius of fillet = 40 mm w = width of angle shear connector = 150
So P = 537.47 kN
>239.64 kN So OK .
5.2.2 - Check cap thickness for Flexural Shear : Total shear acting at a distance d/2 from the face of the column = 3*Rmax; Where Rmax=Rc or Rt whichever is larger. Rmax = 699.76 kN So Total Shear,Vc =2*699.76 =1399.52 kN Where, b = 4500 mm Consider clear cover 75 and dia of Bar 16 mm , So d ( Outer Layer) = 1250-75-8 =1167 mm , where d is the effective depth of cap. d ( Inner Layer) = 1250-75-16 - 8 = 1151 mm dave = ( 1167+1151 )/2 = 1159 mm dave. So, Vc = Vc/bd = 0.27 Mpa AS per ACI Shear Stress applied to concrete should be less than 0.17√f'c Mpa. In present case which is coming 0.93 Mpa. This is greater than applied stress so consideration is quite Ok. 5.2.3.- Check for position of Piles : Distance from pile edge to pile cap edge, x = 200 mm Distance from pile center to pile cap edge = 500 mm Diameter of punching plane, y = 800 mm Perimeter of punching plane = PI()*800 =2513 mm So area of concrete to resist punching of pile = 2513*200 = 502600 Sq.mm Punching stress developed = Rmax*1000/502600 = 1.39 Mpa Where Rmax is the Maximum pile reaction = Rcmax = 699.76 kN AS per ACI Shear Stress applied to concrete should be less than 0.34√f'c Mpa. In present case which is coming 1.52 Mpa. This is greater than applied stress, 1.39 Mpa, so consideration is quite Ok.
Md. Giasuddin
Page 8 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 5.2.4 - Check for Bending Moment : Maximum moment acting at the face of the column=2*Maximum pile reaction*distance between pile center to column face. So Mmax=3*Rmax*x' , Where x' = 1.350 m
ρ b =0.85*0.85*
Mmax= 1889.4 kN.m.
Mu
fy ⎞ ⎛ f ybd 2 ⎜1 0.59 ⎟ ...; Where f 'c ⎠ ⎝ Mu
d f y b(1
0.59
fy fc '
b=
fc ' 600 f y 600 fy
0.02187
max=
0.75*
b
=
0.01640194
0.9 Which is less than dprovide ; so OK
290.70 mm
)
5.2.5 - Reinforcement Calculation : 5.2.5.1 - Bottom Reinforcement : Consider clear cover 75 and dia of Bar 16 mm , So d (Outer Layer) = 1250-75-8 = 1167 mm; where d is the effective depth of cap. d ( Inner Layer) = 1250 -75 -16 - 8 = 1151 mm dmin = MIN( 1151,1167) = 1151 mm Compressive pile reactions will produce tension at the bottom of the cap. Mdes = 1889.352 kN.m Assuming depth of stress block, a = 22.7 mm Area of steel, As = M*1000000/(0.9*fy*(d-a/2)) =4439 mm2.
42 Nos. of Dia. 16 mm along both dic.
(Ref. -Design of concrete structure, By-Nilson & Winter,Page 83 ,10th Ed.) Check for a a = As*fy/(.85*fc'*b) = 22.7 mm Consideration is OK, So As = 4439 mm2. But Min Rebar Required = 0.0015bt = 8437.5 mm2 Consider bar Size = 16 mm So Nos. of Bars = 42 Nos 5.2.5.2 - Top Reinforcement : Consider clear cover 50 and dia of Bar 16 mm , So d (Outer Layer) = 1250 -50-8 = 1192 mm Where d is the effective depth of cap from Cap Bottom to Rebar center at Top. d ( Inner Layer) = 1250 -50-16 - 8 = 1176 mm d = Min(1192,1176) = 1176 mm
Cap Reinforcement Plan at Bottom
Tensile pile reactions will produce tension at the top of the cap. So Mu= 2*Rt*x' , Where x' = 1.35 m
42 Nos. of Dia. 16 mm along both dic.
Mdes = 1399.14 kN.m Assuming depth of stress block, a = 16.4 mm Area of steel, As = M*1000000/(0.9*fy*(d-a/2)) = 3208 mm2 (Ref. -Design of concrete structure, By-Nilson & Winter,Page 83 ,10th Ed.) Check for a a = As*fy/(.85*fc'*b) = 16.4 mm Consideration is OK, So As = 3208 mm2 Min Rebar Required = 0.0015bt = 8437.5 mm2 Consider bar Size = 16 mm So Nos. of Bars = 42 Nos 5.2.5.3 -Vertical Reinforcement Around The pile cap : Total uplift to be resisted by the vertical rebars around the pile cap = Fz = 3834.23 kN Cap Reinforcement Plan at Top
So As = Fz*1000/0.7/Fy = 13198.73 mm2 Total Nos. of top reinforcement is 168 whose total area is 33778 mm2. So if all top bars are bent downwards this will be good enough for uplift. As per BS 8110, Ultimate bond stress in tension bars uu is given by : Uu = 0.4√fc' = 1.84 Mpa
Development length ld is given by : l d = So Development length ld required = 247 mm
Fs ;where∑ o is the total perimeter of all rebars, Fs=Fz uu ∑ o
Provide all top bars bent downwards for the half depth of the cap.It will be suffient for development length.
Md. Giasuddin
Page 9 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 5.2.5.4 -Horizontal Reinforcement Around The pile cap : Provide 5 nos. of 10mm dia bar around the cap distributed along the whole depth with 300 mm lapping at the joint. 6 - Structural Design of Pile Ultimate loads on Single Pile : Compressive load = Rc = 699.76 kN Uplift load = Rt = 518.2 kN Ultimate Moment For Maximum Compression , Mu = 349.44 kN.m Ultimate Moment For Max Uplift , Mu = 309.15 kN.m 6.1 Design of upper segment of pile 6.1.1 Design g for Compression p Plus Bending g Pile diameter, h = 600 mm
Ac = /4h2 = 282743.3 Sqmm.
Pile Section at Upper Segment
⎛ c ⎞ N ⎜ 1.5 ⎟ f A ⎝ ⎠ c c M ⎛ c ⎞ ⎜ 1.5 ⎟ f A h ⎝ ⎠ c c ⎛ c ⎞ Atot f y ⎜ 1.5 ⎟ A f ⎝ ⎠ c c c
= 1.5
N = Normal Load = 699760.00 N fc = 30.00 MPa M = Moment = 349440000.00 N.mm so
= 0.082
And
= 0.069
&
= 0.2
For above values of
( From chart of Annexure-2 )
Pile Section at Lower Segment
So Atot = 1.5 Acfc/ cfy = 4087.9 Sqmm. Rebar Dia = 25 mm So Nos. of Bar = 9 Nos. 6.1.2 Design for Tension Plus Bending N = Normal Load = 518200.00 N fc = 30.00 MPa M = Moment = 309150000.00 N.mm so
= 0.061
And
= 0.061
&
= 0.28
For above values of
Hu ( From chart of Annexure-2 )
Rebar Dia = 25 mm So Nos. of Bar = 12 Nos. Provide 13 nos. of dia. 25mm. Length of fixity is 5.53 meter.
( Ref. to clause4.4 - Check for pile head deflection: )
For safe dissipation of moment at the point of fixity designed rebar is extended by 1.97 meter below the point of fixity. Hence length of upper segment of the pile is 7.5 meter. 6.2 Calculation to Find Point of Zero Moment in the Pile
Moment at aheight h is
Hu * h
1 k p γh*h*Pile Dia*h/3 =0.0 2
Where k p = Co-efficient of passive earth pressure =
1+sin 1-Sin
h= 1st Segment Length of pile
So Atot = 1.5 Acfc/ cfy = 5723.0 Sqmm.
3.25
Since Tension plus Bending combination requires more reinforcement than that of compression plus bending combination, Uplift case is taken into consideration.
Kp h Passive Pressure on Pile
Hu ( for Uplift ) = 136.35 kN So Moment =-0.1 at a distance 7.237 m from Pile Top
Md. Giasuddin
Page 10 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) h = 7.237 m and Pile Dia = 0.6 m
(h should be measured from GL but 1st segment of pile is considered Conservatively)
Upper segment considered = 7.5 meter Rebar Requirement to Resist Tensile force : Acting tension at any point = Tension at pile top - Frictional Resistance by Soil Skin Friction is g given by y = 0.5*Ks*Pd*tand*As Where; Ks=0.7,
=
= 32 Degree
Submerged Density of soil = 8 KN/Cum Pd=7.5 *8 = 60 kN/Sqm As=PI()*0.6*7.5 = 14.14 Sqm So, Frictional Resistance by soil=0.5*0.7*60*Tan15*14.14 = 185.55 kN Net Tension at the point = 518.2 - 185.55 = 332.65 kN Tensile Force to be resisted = 332650 N Consider no tension to be resisted by concrete that means all tensile forces shall be resisted by rebar only. Yield Strength of Rebar = 415 Mpa So Tensile Strength Can be considered as = 0.7*415=290.5 Mpa So Rebar area required to resist Tensile force = 332650 / 290.5 = 1146 mm2 Minimum Rebar for pile section is = 0.004*X-Sectinal area of pile = 1131 mm2. 6 nos. of dia 16 mm for the lower segment is ok from structural point and minimum requirement as well.
Md. Giasuddin
Page 11 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3)
Annexure-1: Reinforcement Chart for Chimney
Md. Giasuddin
Page 12 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-2 SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) Annexure-2: Reinforcement Chart for Pile
Md. Giasuddin
Page 13 of 13
Date : 17 April '11
Foundation Design Calculation of Tower Type 2DT6 For Soil Category-3
1st Subm.
17-Apr-11
Md. Giasuddin
Submission Status
Date
Designed By
Description
Approved By
EMPLOYER :
CONTRACTOR :
POWER GRID COMPANY OF BANGLADESH LTD.
SANERGY CO.
NAME OF PROJECT :
DESIGN-BUILD AND TRUNKEY CONTRACT FOR CONSTRUCTION OF 230kV BIBYANA COMILLA TRANSMISSION LINE (LOT-3) AUTHORITY DESIGNED BY CHECKED BY APPROVED BY
NAME & SIGN Md. Giasuddin Md. Giasuddin
DATE 17-Apr-11
SUBMISSION SOUGHT For approval For construction As Built
Paper Size
Language
Total Sheets
A4
English
13
Scale :
N/A
Revision 1st Sub.
Document No. : PGCB/230kV/TL/B-C/Lot-3/Des.Cal/Local/09
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) Contents
Page No.
1. General.
03
1.1 Foundation Loads
03
1.2 Geotechnical Information
03
1.3 Foundation Strength Factors
03
1.4 Factored Foundation Loads
03
1.5 Codes & Standards Considered
03
1.6 Material Properties
03
1.7 Geometrical Data of the Tower 2DT6
03
1.8 Layout Plan Of the Foundation
04
2. Residual Shear Calculation
04
3. Foundation Geometry
05
4 : Design Calculation for Pile
05
4.1 - Pile Design Load Against Compressive Load
05
g Load oad Against ga Up 4.2 - Pile Design Uplift
05
4.3 - Minimum Length of Pile Group Against Uprooting
05
4.4 - Check for pile head deflection
06
4.5 - Ultimate Stress on Pile Section
07
Section-5 :Structural Design of Chimney & Pile Cap
07
5.1 - Design of Chimney
07
5 2 - Design 5.2 D i off Pile Pil Cap C
08
5.2.1.- Check Punching of cleats
08
5.2.1.a Check For Compression
08
5.2.1.b Check For Uplift
08
5.2.2 - Check cap thickness for Flexural Shear
08
5.2.3.- Check for position of Piles
08
5.2.4 - Check for Bending Moment
09
5.2.5 - Reinforcement Calculation
09
5.2.5.1 - Bottom Reinforcement
08
5.2.5.2 - Top Reinforcement
09
5.2.5.3 -Vertical Reinforcement Around The pile cap
09
5.2.5.4 -Horizontal Reinforcement Around The pile cap
10
6 - Structural Design of Pile
10
6.1 Design of upper segment of pile
10
6.1.1 Design for Compression Plus Bending
10
6.1.2 Design for Tension Plus Bending
10
6.2 Calculation to Find Point of Zero Moment in the Pile
10
Annexure-1
12
Annexure-2
13
Giasuddin
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 1. General. The objective of this generic design is to compute loads on individual pile top, length of fixity of pile and is to design pile, pile cap and chimney. If not mentioned otherwise, values with suffices x, y and z indicate three global directions with outward positive. 1.1 Foundation Loads :
Ultimate Loads Along Global Direction ( Pull and Thrust Vertical) Items
Fz ( kN )
Fx (kN)
Fy (kN)
Max Compression Case
3154.98
893.33
831.62
Max Uplift Case
2840.17
893.33
831.62
1.2 Geotechnical Information: Angle of Int. Friction, ø = 30 Degree Soil Density = 17 kN/Cum. Soil Submerged Density = 7 kN/Cum. Frustum angle = 15 Degree; As per techinical specification 1.3 Foundation Strength Factors : Strength Factor
Applied Loading Case
2DL, 2DL 2D1
2D25, 2D25 2DT6
1.23
1.35
For All Load Cases
1.4. Factored Foundation Loads. Factored Loads by using Foundation Strength Factor from Appendix (7.A2),Volume 2 of 3
Factored Ultimate Loads Along Global Direction ( Pull and Thrust Vertical) Items
Fz ( kN )
Fx (kN)
Fy (kN)
Max Long. Case in Comp.
4259.22
1206.00
1122.69
Max Long. Case in Uplift
3834.23
1206.00
1122.69
1.5 Codes & Standards Considered : ACI BS 8110 1.6 Material Properties and Clear Cover : 28 days cube strength of concrete for Pile; fc' = 30 Mpa. 28 days cube strength of concrete for Pile-Cap; fc' = 25 Mpa. Corresponding cylinder strength of concrete for Pile-Cap; fc' = 21.25 Mpa. Yield Strength Reinforcing Steel ;fy = 415 Mpa. Concrete Clear Cover at top and sides of Cap & Column is = 50 mm. Concrete Clear Cover for sides of Pile is = 75 mm. Unit Weight of Concrete = 24 kN/Cum. 1.7 Geometrical Data of the Tower 2DT6 : Face Slope = Ø = 13.306 Degree. Diagonal Slope = Ø = 18.493 Degree.
Md. Giasuddin
Page 3 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 1.8 Layout Plan Of the Foundation
1800
450
450
1800
1800
450
1800
900
450
1800
900
450
1800
900
4500
900
4500
1800
450
1800
450
450
4500
4500
CP
1800 900
450
450
1800
900
1800
900
4500
4500
900
1800
450
4500
450
4500
450
1800
1800
450
450
1800
1800
450
Layout Plan of Foundation
2. Residual Shear Calculation :
Items
Vertical Loads Fz ( kN )
Leg Shear ( kN ) = Fz*Tan Fxleg
Fyleg
Residual Shear ( kN ) Fx (kN)
Fy (kN)
FxRes = Fx-Fxleg
FyRes = Fy-Fyleg
Max Compression Case
4259.22
1007.31
1007.31
1206.00
1122.69
198.69
115.38
Max Uplift Case
3834.23
906.80
906.80
1206.00
1122.69
299.20
215.89
Md. Giasuddin
Page 4 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 3. Foundation Geometry : Size of the column = 900 mmX900 mm. Dia of the Pile, Dp = 600 mm. h'' = 280.5 mm. h' = 400 mm. f = 300 mm. Pile Center to center Distance = 1800 mm. Height of column, h = 700 mm. Length/Width of the Cap, L/B = 4500 mm. Cap Thickness, t = 1250 mm. No. of Pile Per Leg = 8 Nos Weight Calculation Weight of Column, Wcol = 13.61 kNs.
Foundation Layout Detail
Typical Pile Cap Section
Weight of Pad, Wpad = 607.5 kNs. Weight of Superimposed Soil, Ws =103.28 kNs. Bouyant Weight of Column, W'col = 7.94 kNs Bouyant Weight of Pad, W'pad = 354.38 kNs Bouyant Weight of Superimposed Soil, W's = 42.53 kNs
Loads on Pile top : For Maximum Comp. Resultant Compressive Load = Rzc =Fz+ 1.35*(Wcol+Wpad+Ws) = 5150.22 kNs. Moment Mx = Moment for Leg and Residual Shear = Fxleg*0.0 + FxRes*(t+h+h''-0.15) =376.12 kN.m Moment My = Moment for Leg and Residual Shear = Fyleg*0.0 + FyRes*(t+h+h''-0.15) = 218.41 kN.m For Maximum Uplift : Resultant Uplift = Rzt=Fz - W'col - W'pad - W's = 3429.38 kNs Moment Mx = Moment for Leg and Residual Shear = Fxleg*0.0 + Fxres*(t+h+h''-0.15) = 566.39 kN.m Moment My = Moment for Leg and Residual Shear = Fyleg*0.0 + Fyres*(t+h+h''-0.15) = 408.68 kN.m 4 : Design Calculation for Pile : Reaction of pile with applied vertical loads and biaxial bending moment can be expressed by the following equation:
RV =
R V M x *d1x M y *d1y ± ± 8 ∑ dix 2 ∑ diy 2
Where , d1x and d1y denote the distances from pile center to cap center along X or Y Direction. In this case d1x=d1y= 0.9 m.
∑
dix
2
∑
diy
2
6*1.8^2 = 19.44 Sqm.
4.1 - Pile Design Load Against Compressive Load : Maximum compresive load that a pile will be imposed can be expressed by : So Rcmax = 698.83 kNs.
R Cmax =
( Pile weight is to be considered during Pile schedule)
R zc 8
M x *d1x ∑ dix 2
M y *d1y
∑ diy
2
4.2 - Pile Design g Load Against g Uplift p : Maximum compresive load that a pile will be imposed can be expressed by : So Rtmax = 518.96 kNs.
R Tmax =
( Pile weight is to be considered during Pile schedule)
R zt 8
M x *d1x ∑ dix 2
M y *d1y
∑ diy
2
4.3 - Minimum Length of Pile Group Against Uprooting : Soil body to Resist Uplift Say minimum length of pile =9 m Depth of pile, d = 10.625 m. So a = d/2 = 5.313 m. The base size of the soil frustum at the lowest point b' = 4.2m X4.2 m The base size of the soil frustum at Mid Height ; b =5.247 m X5.247 m Average Area = (4.2^2+5.247^2)/2 =22.59 sqm.
Md. Giasuddin
Page 5 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) So Frustum Volume = 22.59 * 5.3125 =120.01 cum The upper soil volume = 5.247^2*5.313= 146.27 cum
GL
Total soil Volume = 266.28 Cum Total weight of soil body = 266.28*7=1863.96 kN Skin resistance of pile group is Given by :
Qsu =2 * ( L
B) * H * f s
Where L and B are the overall length and width of pile group, H is the depth of soil block and f s is the unit skin friction
a
1 K p Tan 2 s d
which is given by fs
Ks =1 ;( soil to soil co-efficient of earth pressure) Pd= d,
= = 30 Degree
y = Submerged Density of soil = 7 kN/Cum. Pd =7 7 *10 10.625 625 = 74.375 74 375 kNs. kNs So fs = 21.47 kN/Sqm. L= B = b' = 4.2 m and H = d = 10.625 m. So Qsu = 3832.4 kNs
L
d
b
Ultimate uplift capacity of pile group = Skin Resistance + Submerged Weight of soil body = 5696.36kNs. Allowable capacity (FS=1.5) = 3797.57 kNs Resultant Uplift = 3429.38 kNs. Which is less than 3797.57 kNs So OK.
a
4.4 - Check for pile head deflection: For Max Compression: Fx = Leg Shear = 1007.31 kN Fy = Leg Shear = 1007.31 kN Passive resistance by Cap Only ( Same in x and y face)
Passive resistance by Pile Cap is
1 k p γ*(1.55+0.30)*1.25*4.5 γ*(1 55+0 30)*1 25*4 5 = 2
Where k p = Co-efficient of passive earth pressure =
1+sin 1-Sin
109 27 kN 109.27
3.00
γ=Submerged density of soil =7 kN/Cum.
b' GL 300
Net Fx = Leg Shear = 898.04 kN Net Fy = Leg Shear = 898.04 kN
Cap Top
Vres=Sqrt.(898.04^2+898.04^2)=1270.02 kN Lateral Load carried by a single Pile = 158.75 kN For Max Uplift:
1250
Fx = Leg Shear = 906.8 kN Fy = Leg Shear = 906.8 kN Net Fx = Leg Shear = 797.53 kN Net Fy = Leg Shear = 797.53 kN Vres=Sqrt.(797.53^2+797.53^2)=1127.88 kN Lateral Load carried by a single Pile = 140.99 kN
Cap Bot.
Design shear carried by a single Pile Qmax = 158.75 kN For fixed head pile depth of fixity is given by
Lf/T = 2.15; (Ref. to figure no 2 , appendix C of IS: 2911) For fixed head piles .
Where, T Where ; E
5
EI K1 and
4700 I
fc ' d4 64
Kp h
Passive Pressure on Cap
K1 = 0.146 For Submerged Loose Sand 25742.96 Mpa = 257430 kg/sqcm. 636172.5 cm4
EI = 163769889855 kg.sqcm.
So T = 257.03 cm = 2.57 m So depth of fixity, Lf = 5.53 m Deflection, Y = Q*(Lf)^3/12EI = 1.366 cm. = 13.66 mm; Which is less than 25mm, So OK.
Md. Giasuddin
Page 6 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 4.5 - Ultimate Stress on Pile Section For Max Compression For fixed head long pile : Moment M=m.MF = 0.82*Q*Lf/2 = For Max Compression M = 359.93 kN.m For Max Uplift M = 319.67 kN.m For Max Compression. Q = Hu = 158.75 kN. So Mu = 359.93 kN.m For Max Uplift Q = Hu = 140.99 kN. So Mu = 319.67 kN.m Ultimate loads on Single Pile : Compressive load = Rc = 698.83 kN Uplift load = Rt = 518.96 kN For Max Compression ultimate Moment , Mu = 359.93 kN.m For Max Uplift ultimate Moment , Mu = 319.67 kN.m Section-5 : Structural Design of Chimney & Pile Cap 5.1 - Design of Chimney : Ultimate Compression = 4259.22 kN 50% of Ult. Compression = 2129.61 kN Residual shear : Fxmax = 299.20 kN Fymax = 215.89 kN Resultant Fxy = 368.96 kN
1 of 12 of dia. 20 mm
y 0.793 = 292.6 kN.m. M = Fxy* Pu = 2129610.00 N Mu = 292582755.1 N.mm D = 900.00 mm b = 900 mm d' = 66 mm d'/D = 0.073 mm fck = 25.0 Mpa fy = 415.0 Mpa
Pu/fckbD = 0.105 Mu /fckbD2 = 0.016 For the above values, graph ( see annexure-1 ) shows that no rebar is needed. As per Code Min Rebar Required = 0.004*900^2 = 3240 mm2 Consider Bar Dia. 20 mm
Column Section
Provide 12 nos 20mm dia. Embedded Length of Rebar. C Compression i tto b be resisted i t db by th the rebars b iin chimney hi =F Fz = 2129 2129.61 61 kN Total Nos. of reinforcement is 12 of dia 20 12mm. As per BS 8110, Ultimate bond stress in compression bars uu is given by : uu=0.5√fc' Mpa
Development length l d
is given by : l d =
Fs ;where∑ o is the total perimeter of all rebars, Fs=Fz uu ∑ o
So Uu = 2.3 Mpa. So Development length ld required = 1228 mm.
Cap thgickness is = 1250 mm and Clear Cover at bottom = 75 mm Let Chimney rebar rest on the bottom mesh of cap. So Embedded length provided = 1250-75-32 = 1143 mm which is more than requirement, so Ok.
Md. Giasuddin
Page 7 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 5.2 - Design of Pile Cap : 5.2.1.- Check Punching of cleats: 5.2.1.a Check For Compression: Ultimate Compression = 4259.22 kN Compression to be carried by cleats = 50% of Comp.= 2129.61 kN Consider 4 cleat group with 4 three cleats in each group. The size of cleats is 150X150X20 ; length 160 . Load Carried by each Cleat =0.5* Ccomp./16 = 133.1 kN The Capacity P of each cleat is given by :
P
1.19 f 'c b(t
x / 2)
r
Where , b = Length of Angle Shear Connector = 160 mm
1/ 2
x
t = Thickness of Angle Shear Connector = 20 mm
⎡ Fy ⎤ t⎢ ⎥ 1 19 f 'c ⎦ ⎣1.19
w r
t.
r = Radius of fillet = 40 mm w = width of angle shear connector = 150
( Ref. : Art.7.6.2, Design of Latticed Steel Transmission Structures; Published by The American Society of Civil Engineers) x = 68.19 mm;
So P = 537.47 kN
>133.1 kN So OK .
5.2.1.b Check For Uplift: Ultimate Uplift = 3834.23 kN Consider 4 cleat group with 4 three cleats in each group. The size of cleats is 150X150X20 ; length 160 . Load carried by each cleat = 239 239.64 64 kN
The Capacity P of each cleat is given by :
P
1.19 f 'c b(t
r
x / 2)
Where , b = Length of Angle Shear Connector = 160 mm t = Thickness of Angle Shear Connector = 20 mm
1/ 2
x
⎡ Fy ⎤ t⎢ ⎥ ⎣1.19 f 'c ⎦
w
r
x = 68.19 mm;
t.
r = Radius of fillet = 40 mm w = width of angle shear connector = 150
So P = 537.47 kN
>239.64 kN So OK .
5.2.2 - Check cap thickness for Flexural Shear : Total shear acting at a distance d/2 from the face of the column = 3*Rmax; Where Rmax=Rc or Rt whichever is larger. Rmax = 698.83 kN So Total Shear,Vc =2*698.83 =1397.66 kN Where, b = 4500 mm Consider clear cover 75 and dia of Bar 16 mm , So d ( Outer Layer) = 1250-75-8 =1167 mm , where d is the effective depth of cap. d ( Inner Layer) = 1250-75-16 - 8 = 1151 mm dave = ( 1167+1151 )/2 = 1159 mm dave. So, Vc = Vc/bd = 0.27 Mpa AS per ACI Shear Stress applied to concrete should be less than 0.17√f'c Mpa. In present case which is coming 0.93 Mpa. This is greater than applied stress so consideration is quite Ok. 5.2.3.- Check for position of Piles : Distance from pile edge to pile cap edge, x = 200 mm Distance from pile center to pile cap edge = 500 mm Diameter of punching plane, y = 800 mm Perimeter of punching plane = PI()*800 =2513 mm So area of concrete to resist punching of pile = 2513*200 = 502600 Sq.mm Punching stress developed = Rmax*1000/502600 = 1.39 Mpa Where Rmax is the Maximum pile reaction = Rcmax = 698.83 kN AS per ACI Shear Stress applied to concrete should be less than 0.34√f'c Mpa. In present case which is coming 1.52 Mpa. This is greater than applied stress, 1.39 Mpa, so consideration is quite Ok.
Md. Giasuddin
Page 8 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 5.2.4 - Check for Bending Moment : Maximum moment acting at the face of the column=2*Maximum pile reaction*distance between pile center to column face. So Mmax=3*Rmax*x' , Where x' = 1.350 m
ρ b =0.85*0.85*
Mmax= 1886.8 kN.m.
Mu
fy ⎞ ⎛ f ybd 2 ⎜1 0.59 ⎟ ...; Where f 'c ⎠ ⎝ Mu
d f y b(1
0.59
fy fc '
b=
fc ' 600 f y 600 fy
0.02187
max=
0.75*
b
=
0.01640194
0.9 Which is less than dprovide ; so OK
290.51 mm
)
5.2.5 - Reinforcement Calculation : 5.2.5.1 - Bottom Reinforcement : Consider clear cover 75 and dia of Bar 16 mm , So d (Outer Layer) = 1250-75-8 = 1167 mm; where d is the effective depth of cap. d ( Inner Layer) = 1250 -75 -16 - 8 = 1151 mm dmin = MIN( 1151,1167) = 1151 mm Compressive pile reactions will produce tension at the bottom of the cap. Mdes = 1886.841 kN.m Assuming depth of stress block, a = 22.6 mm Area of steel, As = M*1000000/(0.9*fy*(d-a/2)) =4433 mm2.
42 Nos. of Dia. 16 mm along both dic.
(Ref. -Design of concrete structure, By-Nilson & Winter,Page 83 ,10th Ed.) Check for a a = As*fy/(.85*fc'*b) = 22.6 mm Consideration is OK, So As = 4433 mm2. But Min Rebar Required = 0.0015bt = 8437.5 mm2 Consider bar Size = 16 mm So Nos. of Bars = 42 Nos 5.2.5.2 - Top Reinforcement : Consider clear cover 50 and dia of Bar 16 mm , So d (Outer Layer) = 1250 -50-8 = 1192 mm Where d is the effective depth of cap from Cap Bottom to Rebar center at Top. d ( Inner Layer) = 1250 -50-16 - 8 = 1176 mm d = Min(1192,1176) = 1176 mm
Cap Reinforcement Plan at Bottom
Tensile pile reactions will produce tension at the top of the cap. So Mu= 2*Rt*x' , Where x' = 1.35 m
42 Nos. of Dia. 16 mm along both dic.
Mdes = 1401.19 kN.m Assuming depth of stress block, a = 16.4 mm Area of steel, As = M*1000000/(0.9*fy*(d-a/2)) = 3212 mm2 (Ref. -Design of concrete structure, By-Nilson & Winter,Page 83 ,10th Ed.) Check for a a = As*fy/(.85*fc'*b) = 16.4 mm Consideration is OK, So As = 3212 mm2 Min Rebar Required = 0.0015bt = 8437.5 mm2 Consider bar Size = 16 mm So Nos. of Bars = 42 Nos 5.2.5.3 -Vertical Reinforcement Around The pile cap : Total uplift to be resisted by the vertical rebars around the pile cap = Fz = 3834.23 kN Cap Reinforcement Plan at Top
So As = Fz*1000/0.7/Fy = 13198.73 mm2 Total Nos. of top reinforcement is 168 whose total area is 33778 mm2. So if all top bars are bent downwards this will be good enough for uplift. As per BS 8110, Ultimate bond stress in tension bars uu is given by : Uu = 0.4√fc' = 1.84 Mpa
Development length ld is given by : l d = So Development length ld required = 247 mm
Fs ;where∑ o is the total perimeter of all rebars, Fs=Fz uu ∑ o
Provide all top bars bent downwards for the half depth of the cap.It will be suffient for development length.
Md. Giasuddin
Page 9 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) 5.2.5.4 -Horizontal Reinforcement Around The pile cap : Provide 5 nos. of 10mm dia bar around the cap distributed along the whole depth with 300 mm lapping at the joint. 6 - Structural Design of Pile Ultimate loads on Single Pile : Compressive load = Rc = 698.83 kN Uplift load = Rt = 518.96 kN Ultimate Moment For Maximum Compression , Mu = 359.93 kN.m Ultimate Moment For Max Uplift , Mu = 319.67 kN.m 6.1 Design of upper segment of pile 6.1.1 Design g for Compression p Plus Bending g Pile diameter, h = 600 mm
Ac = /4h2 = 282743.3 Sqmm. ⎛ c ⎞ N ⎜ 1.5 ⎟ f A ⎝ ⎠ c c M ⎛ c ⎞ ⎜ 1.5 ⎟ f A h ⎝ ⎠ c c ⎛ c ⎞ Atot f y ⎜ 1.5 ⎟ A f ⎝ ⎠ c c c
= 1.5
Pile Section at Upper Segment
N = Normal Load = 698830.00 N fc = 30.00 MPa M = Moment = 359930000.00 N.mm so
= 0.082
And
= 0.071
&
= 0.2
For above values of
( From chart of Annexure-2 )
So Atot = 1.5 Acfc/ cfy = 4087.9 Sqmm. Rebar Dia = 25 mm So Nos. of Bar = 9 Nos. 6.1.2 Design for Tension Plus Bending N = Normal Load = 518960.00 N fc = 30.00 MPa
Pile Section at Lower Segment
M = Moment = 319670000.00 N.mm so
= 0.061
And
= 0.063
&
= 0.3
For above values of
Hu ( From chart of Annexure-2 )
Rebar Dia = 25 mm So Nos. of Bar = 13 Nos. Provide 14 nos. of dia. 25mm. Length of fixity is 5.53 meter.
( Ref. to clause4.4 - Check for pile head deflection: )
For safe dissipation of moment at the point of fixity designed rebar is extended by 2.97 meter below the point of fixity. Hence length of upper segment of the pile is 8.5 meter. 6.2 Calculation to Find Point of Zero Moment in the Pile
Moment at aheight h is
Hu * h
1 k p γh*h*Pile Dia*h/3 =0.0 2
Where k p = Co-efficient of passive earth pressure =
1+sin 1-Sin
h= 1st Segment Length of pile
So Atot = 1.5 Acfc/ cfy = 6131.8 Sqmm.
3.00
Since Tension plus Bending combination requires more reinforcement than that of compression plus bending combination, Uplift case is taken into consideration.
Kp h Passive Pressure on Pile
Hu ( for Uplift ) = 140.99 kN So Moment =-0.1 at a distance 8.194 m from Pile Top
Md. Giasuddin
Page 10 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) h = 8.194 m and Pile Dia = 0.6 m
(h should be measured from GL but 1st segment of pile is considered Conservatively)
Upper segment considered = 8.5 meter Rebar Requirement to Resist Tensile force : Acting tension at any point = Tension at pile top - Frictional Resistance by Soil Skin Friction is g given by y = 0.5*Ks*Pd*tand*As Where; Ks=0.7,
=
= 30 Degree
Submerged Density of soil = 7 KN/Cum Pd=8.5 *7 = 59.5 kN/Sqm As=PI()*0.6*8.5 = 16.02 Sqm So, Frictional Resistance by soil=0.5*0.7*59.5*Tan15*16.02 = 192.61 kN Net Tension at the point = 518.96 - 192.61 = 326.35 kN Tensile Force to be resisted = 326350 N Consider no tension to be resisted by concrete that means all tensile forces shall be resisted by rebar only. Yield Strength of Rebar = 415 Mpa So Tensile Strength Can be considered as = 0.7*415=290.5 Mpa So Rebar area required to resist Tensile force = 326350 / 290.5 = 1124 mm2 Minimum Rebar for pile section is = 0.004*X-Sectinal area of pile = 1131 mm2. 7 nos. of dia 16 mm for the lower segment is ok from structural point and minimum requirement as well.
Md. Giasuddin
Page 11 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3)
Annexure-1: Reinforcement Chart for Chimney
Md. Giasuddin
Page 12 of 13
Date : 17 April '11
POWER GRID COMPANY OF BANGLADESH LIMITED Foundation of Tower Type 2DT6 for SC-3 SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3) Annexure-2: Reinforcement Chart for Pile
Md. Giasuddin
Page 13 of 13
Date : 17 April '11
