Transmission Tower Foundation Design

1st Subm.

17-Apr-11

_{Md. Giasuddin}

Submission

Status

Date

AUTHORITY

NAME & SIGN

DATE

Paper Size

Language

Total Sheets

DESIGNED BY

Md. Giasuddin

17-Apr-11

For approval

A4

English

13

CHECKED BY

Md. Giasuddin

For construction

Scale :

N/A

Revision

1st Sub.

APPROVED BY

As Built

SUBMISSION SOUGHT

Document No. :

PGCB/230kV/TL/B-C/Lot-3/Des.Cal/Local/08

Designed By

Description

Approved By

EMPLOYER :

POWER GRID COMPANY OF

BANGLADESH LTD.

CONTRACTOR :

SANERGY CO

.

NAME OF PROJECT :

DESIGN-BUILD AND TRUNKEY CONTRACT FOR CONSTRUCTION OF 230kV BIBYANA -

COMILLA 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

4.2 - Pile Design Load Against Uplift

g

oad ga

Up

05

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 D i

f Pil C

08

5.2 - Design of Pile Cap

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

1. General.

1.1 Foundation Loads :

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.

Fz ( kN ) Fx (kN) Fy (kN)

3154.98 893.33 831.62

2840.17 893.33 831.62

1.2 Geotechnical Information: Items Max Compression Case

Max Uplift Case

Ultimate Loads Along Global Direction ( Pull and Thrust Vertical)

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 :

2DL 2D1

Applied Loading Case Strength Factor

2D25 2DT6

1.4. Factored Foundation Loads.

Factored Loads by using Foundation Strength Factor from Appendix (7.A2),Volume 2 of 3

F ( kN ) F (kN) F (kN)

2DL, 2D1

1.35 1.23

Factored Ultimate Loads Along Global Direction ( Pull and Thrust Vertical)

2D25, 2DT6 For All Load Cases

Items Fz( kN ) Fx(kN) Fy(kN)

4259.22 1206.00 1122.69

3834.23 1206.00 1122.69

1.5 Codes & Standards Considered : ACI

BS 8110

Max Long. Case in Uplift Max Long. Case in Comp.

Items

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.

1.8 Layout Plan Of the Foundation

450

1800

1800

450

450

450

1800

1800

450

450

4500

900

900

1800

1800

4500

900

900

1800

1800

4500

CP

450

4500

450

4500

450

4500

450

4500

900

900

1800

1800

4500

₉₀₀

900

1800

1800

Layout Plan of Foundation

450

1800

1800

450

450

450

1800

1800

450

450

2. Residual Shear Calculation :

Fxleg Fyleg _{= F}FxRes

x-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

Vertical Loads Fz ( kN )

Items

Residual Shear ( kN ) Fx (kN) Fy (kN)

3. Foundation Geometry :

Size of the column = 900 mmX900 mm. Dia of the Pile, Dp = 600 mm. h'' = 280.5 mm.

h' 400 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. 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 :

Foundation Layout Detail Typical Pile Cap Section

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:

y V x V 2 2

M *d1y

R

M *d1x

R =

±

±

8

∑

dix

∑

diy

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. 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. ( Pile weight is to be considered during Pile schedule) 4.2 - Pile Design Load Against Uplift :

∑

2

∑

2

diy

dix

y zc x Cmax 2 2

M *d1y

R

M *d1x

R

=

8

∑

dix

∑

diy

g g p

Maximum compresive load that a pile will be imposed can be expressed by :

So Rtmax = 518.2 kNs. ( Pile weight is to be considered during Pile schedule) 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. y zt x Tmax 2 2

M *d1y

R

M *d1x

R

=

8

∑

dix

∑

diy

So Frustum Volume = 21.22 * 4.8125 =102.12 cum The upper soil volume = 4.979^2*4.813= 119.32 cum 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 :

GL

Q =2 * (

L

B

) *

H

*

f

Ks =1 ;( soil to soil co-efficient of earth pressure) Pd= d, = = 32 Degree

y = Submerged Density of soil = 8 kN/Cum.

Pd =8 *9 625 = 77 kNs

a

su

s

Q =2 * (

) *

*

Where L and B are the overall length and width of pile group,

H is the depth of soil block and f is the unit skin friction

1

which is given by

₂

s s d

L

B

H

f

fs

K p Tan

Pd 8 9.625 77 kNs. So fs = 24.06 kN/Sqm. L= B = b' = 4.2 m and H = d = 9.625 m. So Qsu = 3890.5 kNs Allowable capacity (FS=1.5) = 3774.68 kNs Resultant Uplift = 3423.31 kNs.

Which is less than 3774.68 kNs So OK.

Ultimate uplift capacity of pile group = Skin Resistance + Submerged Weight of soil body = 5662.02kNs.

b

_d

L

Which is less than 3774.68 kNs So OK. 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)

135 47 kN

a

1

Passive resistance by Pile Cap is

k γ*(1 55+0 30)*1 25*4 5 =

135.47 kN 3.25

γ=Submerged density of soil =8 kN/Cum.

Net Fx = Leg Shear = 871.84 kN Net Fy = Leg Shear = 871.84 kN

Vres=Sqrt.(871.84^2+871.84^2)=1232.97 kN Lateral Load carried by a single Pile = 154.12 kN

b'

GL

Cap Top

300

p

1+sin

Where k = Co-efficient of passive earth pressure =

1-Sin

p

Passive resistance by Pile Cap is

k γ*(1.55+0.30)*1.25*4.5 =

2

For Max Uplift:

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

Design shear carried by a single Pile Qmax = 154.12 kN

Kp h

Cap Bot.

1250

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 .

K1 = 0.146 For Submerged Medium Dense Sand

Where ;

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. 5

Where,

T

EI K

1 and

4700

c

'

E

f

4 64 d I

Kp h

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 M = Fxy* 0.793 = 292.6 kN.m.y 1 of 12 of dia. 20 mm 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 Provide 12 nos 20mm dia. Embedded Length of Rebar.

C i t b i t d b th b i hi F 2129 61 kN

Column Section

Compression to be resisted by the rebars in chimney = Fz = 2129.61 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

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.

s

d d

u

F

Development length l is given by : l = ;where o is the total perimeter of all rebars, Fs=Fz

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 . The Capacity P of each cleat is given by :

Where , b = Length of Angle Shear Connector = 160 mm t = Thickness of Angle Shear Connector = 20 mm r = Radius of fillet = 40 mm

Load Carried by each Cleat =0.5* Ccomp./16 = 133.1 kN

1/ 2

1.19 '

(

/ 2)

.

1 19 '

c y

P

f

b t

r

x

F

x

t

w

r

t

f

⎡

⎤

⎢

⎥

⎣

⎦

_{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 64 kN

1.19

f

c

⎣

⎦

Load carried by each cleat = 239.64 kN The Capacity P of each cleat is given by :

Where , b = Length of Angle Shear Connector = 160 mm t = Thickness of Angle Shear Connector = 20 mm r = Radius of fillet = 40 mm

w = width of angle shear connector = 150

x = 68.19 mm; So P = 537.47 kN >239.64 kN So OK . 1/ 2

1.19 '

(

/ 2)

.

1.19 '

c y c

P

f

b t

r

x

F

x

t

w

r

t

f

⎡

⎤

⎢

⎥

⎣

⎦

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. = ( 1167+1151 )/2 = 1159 mm So, Vc = Vc/bd = 0.27 Mpa

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

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.

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.

5.2.4 - Check for Bending Moment :

So Mmax=3*Rmax*x' , Where x' = 1.350 m b= 0.02187

Mmax= 1889.4 kN.m. max= 0.75* b = 0.01640194

Maximum moment acting at the face of the column=2*Maximum pile reaction*distance between pile center to column face.

f

⎛

⎞

b ' 600 ρ =0.85*0.85* 600 c y y f f f

290.70 mm Which is less than dprovide ; so OK

5.2.5 - Reinforcement Calculation : 5.2.5.1 - Bottom Reinforcement : 2

_{1 0.59}

_...;

_0.9

'

y u y c

f

M

f bd

Where

f

⎛

⎞

⎜

⎟

⎝

⎠

(1 0.59 ) ' u y y c M d f f b f

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.

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.

(Ref. -Design of concrete structure, By-Nilson & Winter,Page 83 ,10th Ed.) d ( Inner Layer) = 1250 -75 -16 - 8 = 1151 mm

dmin = MIN( 1151,1167) = 1151 mm

42 Nos. of Dia. 16 mm along both dic. 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.

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 d = Min(1192,1176) = 1176 mm

d ( Inner Layer) = 1250 -50-16 - 8 = 1176 mm

Cap Reinforcement Plan at Bottom

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.)

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

a = As*fy/(.85*fc'*b) = 16.4 mm Check for a

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 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

So Development length ld required = 247 mm

Provide all top bars bent downwards for the half depth of the cap.It will be suffient for development length.

Cap Reinforcement Plan at Top

s d

u

F

Development length ld is given by : l =

;where

o is the total perimeter of all rebars, Fs=Fz

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 : 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 for Compression Plus Bendingg p g

Pile diameter, h = 600 mm

Ac = /4h2 =282743.3 Sqmm.

c= 1.5

Pile Section at Upper Segment

1.5 1.5 1.5 c c c c c c tot y c c c N f A M f A h A f A f ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ N = Normal Load = 699760.00 N fc = 30.00 MPa M = Moment = 349440000.00 N.mm so = 0.082 And = 0.069

For above values of & = 0.2 ( From chart of Annexure-2 )

So Atot = 1.5 Acfc/cfy =4087.9 Sqmm. Rebar Dia = 25 mm

Pile Section at Lower Segment

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

For above values of & = 0.28 ( From chart of Annexure-2 )

Hu

So Atot = 1.5 Acfc/cfy =5723.0 Sqmm.

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: )

6.2 Calculation to Find Point of Zero Moment in the Pile

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.

Se

gm

ent Lengt

h

of

pi

le

3.25 Hu ( for Uplift ) = 136.35 kN

So Moment =-0.1 at a distance 7.237 m from Pile Top

Since Tension plus Bending combination requires more reinforcement than that of compression plus bending combination, Uplift case is taken into consideration.

p

1+sin

Where k = Co-efficient of passive earth pressure =

1-Sin

Kp h

h= 1st

Passive Pressure on Pile

p

1

Moment at aheight is

*

k γh*h*Pile Dia*h/3 =0.0

2

u

h = 7.237 m and Pile Dia = 0.6 m 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 given by = 0.5*Ks*Pd*tand*As

(h should be measured from GL but 1st segment of pile is considered Conservatively)

g y s d s

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.

1st Subm.

17-Apr-11

_{Md. Giasuddin}

Submission

Status

Date

AUTHORITY

NAME & SIGN

DATE

Paper Size

Language

Total Sheets

DESIGNED BY

Md. Giasuddin

17-Apr-11

For approval

A4

English

13

CHECKED BY

Md. Giasuddin

For construction

Scale :

N/A

Revision

1st Sub.

APPROVED BY

As Built

SUBMISSION SOUGHT

Document No. :

PGCB/230kV/TL/B-C/Lot-3/Des.Cal/Local/09

Designed By

Description

Approved By

EMPLOYER :

POWER GRID COMPANY OF

BANGLADESH LTD.

CONTRACTOR :

SANERGY CO.

NAME OF PROJECT :

DESIGN-BUILD AND TRUNKEY CONTRACT FOR CONSTRUCTION OF 230kV BIBYANA -

COMILLA 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

4.2 - Pile Design Load Against Uplift

g

oad ga

Up

05

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 D i

f Pil C

08

5.2 - Design of Pile Cap

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

1. General.

1.1 Foundation Loads :

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.

Fz ( kN ) Fx (kN) Fy (kN)

3154.98 893.33 831.62

2840.17 893.33 831.62

1.2 Geotechnical Information: Items Max Compression Case

Max Uplift Case

Ultimate Loads Along Global Direction ( Pull and Thrust Vertical)

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 :

2DL 2D1

Applied Loading Case Strength Factor

2D25 2DT6

1.4. Factored Foundation Loads.

Factored Loads by using Foundation Strength Factor from Appendix (7.A2),Volume 2 of 3

F ( kN ) F (kN) F (kN)

2DL, 2D1

1.35 1.23

Factored Ultimate Loads Along Global Direction ( Pull and Thrust Vertical)

2D25, 2DT6 For All Load Cases

Items Fz( kN ) Fx(kN) Fy(kN)

4259.22 1206.00 1122.69

3834.23 1206.00 1122.69

1.5 Codes & Standards Considered : ACI

BS 8110

Max Long. Case in Uplift Max Long. Case in Comp.

Items

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.

1.8 Layout Plan Of the Foundation

450

1800

1800

450

450

450

1800

1800

450

450

4500

900

900

1800

1800

4500

900

900

1800

1800

4500

CP

450

4500

450

4500

450

4500

450

4500

900

900

1800

1800

4500

₉₀₀

900

1800

1800

Layout Plan of Foundation

450

1800

1800

450

450

450

1800

1800

450

450

2. Residual Shear Calculation :

Fxleg Fyleg _{= F}FxRes

x-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

Vertical Loads Fz ( kN )

Items

Residual Shear ( kN ) Fx (kN) Fy (kN)

3. Foundation Geometry :

Size of the column = 900 mmX900 mm. Dia of the Pile, Dp = 600 mm. h'' = 280.5 mm.

h' 400 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. 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 :

Foundation Layout Detail Typical Pile Cap Section

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:

y V x V 2 2

M *d1y

R

M *d1x

R =

±

±

8

∑

dix

∑

diy

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. 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. ( Pile weight is to be considered during Pile schedule) 4.2 - Pile Design Load Against Uplift :

∑

2

∑

2

diy

dix

y zc x Cmax 2 2

M *d1y

R

M *d1x

R

=

8

∑

dix

∑

diy

g g p

Maximum compresive load that a pile will be imposed can be expressed by :

So Rtmax = 518.96 kNs. ( Pile weight is to be considered during Pile schedule) 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. y zt x Tmax 2 2

M *d1y

R

M *d1x

R

=

8

∑

dix

∑

diy

So Frustum Volume = 22.59 * 5.3125 =120.01 cum The upper soil volume = 5.247^2*5.313= 146.27 cum 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 :

GL

Q =2 * (

L

B

) *

H

*

f

Ks =1 ;( soil to soil co-efficient of earth pressure) Pd= d, = = 30 Degree

y = Submerged Density of soil = 7 kN/Cum.

Pd =7 *10 625 = 74 375 kNs

a

su

s

Q =2 * (

) *

*

Where L and B are the overall length and width of pile group,

H is the depth of soil block and f is the unit skin friction

1

which is given by

₂

s s d

L

B

H

f

fs

K p Tan

Pd 7 10.625 74.375 kNs. So fs = 21.47 kN/Sqm. L= B = b' = 4.2 m and H = d = 10.625 m. So Qsu = 3832.4 kNs Allowable capacity (FS=1.5) = 3797.57 kNs Resultant Uplift = 3429.38 kNs.

Which is less than 3797.57 kNs So OK.

Ultimate uplift capacity of pile group = Skin Resistance + Submerged Weight of soil body = 5696.36kNs.

b

_d

L

Which is less than 3797.57 kNs So OK. 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)

109 27 kN

a

1

Passive resistance by Pile Cap is

k γ*(1 55+0 30)*1 25*4 5 =

109.27 kN 3.00

γ=Submerged density of soil =7 kN/Cum.

Net Fx = Leg Shear = 898.04 kN Net Fy = Leg Shear = 898.04 kN

Vres=Sqrt.(898.04^2+898.04^2)=1270.02 kN Lateral Load carried by a single Pile = 158.75 kN

b'

GL

Cap Top

300

p

1+sin

Where k = Co-efficient of passive earth pressure =

1-Sin

p

Passive resistance by Pile Cap is

k γ*(1.55+0.30)*1.25*4.5 =

2

For Max Uplift:

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

Design shear carried by a single Pile Qmax = 158.75 kN

Kp h

Cap Bot.

1250

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 .

K1 = 0.146 For Submerged Loose Sand

Where ;

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. 5

Where,

T

EI K

1 and

4700

c

'

E

f

4 64 d I

Kp h

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 M = Fxy* 0.793 = 292.6 kN.m.y 1 of 12 of dia. 20 mm 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 Provide 12 nos 20mm dia. Embedded Length of Rebar.

C i t b i t d b th b i hi F 2129 61 kN

Column Section

Compression to be resisted by the rebars in chimney = Fz = 2129.61 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

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.

s

d d

u

F

Development length l is given by : l = ;where o is the total perimeter of all rebars, Fs=Fz

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 . The Capacity P of each cleat is given by :

Where , b = Length of Angle Shear Connector = 160 mm t = Thickness of Angle Shear Connector = 20 mm r = Radius of fillet = 40 mm

Load Carried by each Cleat =0.5* Ccomp./16 = 133.1 kN

1/ 2

1.19 '

(

/ 2)

.

1 19 '

c y

P

f

b t

r

x

F

x

t

w

r

t

f

⎡

⎤

⎢

⎥

⎣

⎦

_{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 64 kN

1.19

f

c

⎣

⎦

Load carried by each cleat = 239.64 kN The Capacity P of each cleat is given by :

Where , b = Length of Angle Shear Connector = 160 mm t = Thickness of Angle Shear Connector = 20 mm r = Radius of fillet = 40 mm

w = width of angle shear connector = 150

x = 68.19 mm; So P = 537.47 kN >239.64 kN So OK . 1/ 2

1.19 '

(

/ 2)

.

1.19 '

c y c

P

f

b t

r

x

F

x

t

w

r

t

f

⎡

⎤

⎢

⎥

⎣

⎦

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. = ( 1167+1151 )/2 = 1159 mm So, Vc = Vc/bd = 0.27 Mpa

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

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.

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.

5.2.4 - Check for Bending Moment :

So Mmax=3*Rmax*x' , Where x' = 1.350 m b= 0.02187

Mmax= 1886.8 kN.m. max= 0.75* b = 0.01640194

Maximum moment acting at the face of the column=2*Maximum pile reaction*distance between pile center to column face.

f

⎛

⎞

b ' 600 ρ =0.85*0.85* 600 c y y f f f

290.51 mm Which is less than dprovide ; so OK

5.2.5 - Reinforcement Calculation : 5.2.5.1 - Bottom Reinforcement : 2

_{1 0.59}

_...;

_0.9

'

y u y c

f

M

f bd

Where

f

⎛

⎞

⎜

⎟

⎝

⎠

(1 0.59 ) ' u y y c M d f f b f

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.

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.

(Ref. -Design of concrete structure, By-Nilson & Winter,Page 83 ,10th Ed.) d ( Inner Layer) = 1250 -75 -16 - 8 = 1151 mm

dmin = MIN( 1151,1167) = 1151 mm

42 Nos. of Dia. 16 mm along both dic. 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.

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 d = Min(1192,1176) = 1176 mm

d ( Inner Layer) = 1250 -50-16 - 8 = 1176 mm

Cap Reinforcement Plan at Bottom

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.)

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

a = As*fy/(.85*fc'*b) = 16.4 mm Check for a

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 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

So Development length ld required = 247 mm

Provide all top bars bent downwards for the half depth of the cap.It will be suffient for development length.

Cap Reinforcement Plan at Top

s d

u

F

Development length ld is given by : l =

;where

o is the total perimeter of all rebars, Fs=Fz

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 : 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 for Compression Plus Bendingg p g

Pile diameter, h = 600 mm

Ac = /4h2 =282743.3 Sqmm.

c= 1.5

Pile Section at Upper Segment

1.5 1.5 1.5 c c c c c c tot y c c c N f A M f A h A f A f ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ N = Normal Load = 698830.00 N fc = 30.00 MPa M = Moment = 359930000.00 N.mm so = 0.082 And = 0.071

For above values of & = 0.2 ( From chart of Annexure-2 )

So Atot = 1.5 Acfc/cfy =4087.9 Sqmm. Rebar Dia = 25 mm

Pile Section at Upper Segment

So Nos. of Bar = 9 Nos. 6.1.2 Design for Tension Plus Bending

N = Normal Load = 518960.00 N fc = 30.00 MPa

M = Moment = 319670000.00 N.mm so = 0.061

And = 0.063

For above values of & = 0.3 ( From chart of Annexure-2 )

Pile Section at Lower Segment

Hu

So Atot = 1.5 Acfc/cfy =6131.8 Sqmm.

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: )

6.2 Calculation to Find Point of Zero Moment in the Pile

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.

Se

gm

ent Lengt

h

of

pi

le

3.00 Hu ( for Uplift ) = 140.99 kN

So Moment =-0.1 at a distance 8.194 m from Pile Top

Since Tension plus Bending combination requires more reinforcement than that of compression plus bending combination, Uplift case is taken into consideration.

p

1+sin

Where k = Co-efficient of passive earth pressure =

1-Sin

Kp h

h= 1st

Passive Pressure on Pile

p

1

Moment at aheight is

*

k γh*h*Pile Dia*h/3 =0.0

2

u

h = 8.194 m and Pile Dia = 0.6 m 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 given by = 0.5*Ks*Pd*tand*As

(h should be measured from GL but 1st segment of pile is considered Conservatively)

g y s d s

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.