Transmission Tower Foundation Design

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