Transmission Tower Foundation Design

1st Subm. 17-Apr-11 Md. Giasuddin

Foundation Design Calculation of Tower Type 2DT6 For Soil Category-2

Submission Status

Date

AUTHORITY NAME & SIGN DATE Paper Size Language Total Sheets

DESIGNED BYMd. Giasuddin

17-Apr-11 For approval A4 English 13

CHECKED BYMd. Giasuddin

For construction Scale : N/ARevision1st 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)

POWER GRID COMPANY OF BANGLADESH LIMITED

Contents Page No.

1. General. 03

1.1 Foundation Loads 03

Foundation of Tower Type 2DT6 for SC-2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3)

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 05g oad ga Up 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 085.2 - 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

Annexure-2 13

Giasuddin Date : 17 April '11

POWER GRID COMPANY OF BANGLADESH LIMITEDFoundation of Tower Type 2DT6 for SC-2 FOR

1. General.

1.1 Foundation Loads :

Foundation of Tower Type 2DT6 for SC 2 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3)

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 2D1Applied 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

1.351.23

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.

Md. Giasuddin of 13 Date : 17 April '11

POWER GRID COMPANY OF BANGLADESH LIMITEDFoundation of Tower Type 2DT6 for SC-2 FORFoundation of Tower Type 2DT6 for SC 2 FOR

BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3)

1.8 Layout Plan Of the Foundation

450 1800 1800 450

450

45018001800450

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

45018001800450

450

2. Residual Shear Calculation :

Fxleg FylegFxRes

= 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

Vertical LoadsFz ( kN )Items

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

Leg Shear ( kN ) = Fz*Tan




3. Foundation Geometry :

Size of the column = 900 mmX900 mm.

Dia of the Pile, Dp = 600 mm.

h'' = 280.5 mm.

h' 400h' = 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:

yV xV 2 2

M *d1yR M *d1xR = ± ±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 :

∑ ∑ 22 diydix

yzc xCmax 2 2

M *d1yR M *d1xR =8 dix diy∑ ∑

g g p


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 UpliftSay 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.

yzt xTmax 2 2





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

1which 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 dL


4.4 - Check for pile head deflection:

For Max Compression:

Fx = Leg Shear = 1007.31 kN

Fy = Leg Shear = 1007.31 kNPassive resistance by Cap Only ( Same in x and y face)

135 47 kN

a

1Passive 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

p1+sinWhere k = Co-efficient of passive earth pressure = 1-Sin

pPassive resistance by Pile Cap is k γ*(1.55+0.30)*1.25*4.5 =2

For Max Uplift:


Fy = Leg Shear = 906.8 kN

Net Fx = Leg Shear = 771.33 kN


Vres=Sqrt.(771.33^2+771.33^2)=1090.83 kN


Design shear carried by a single Pile Qmax = 154.12 kN Kp hCap 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.

5Where, 1 andT EI K4700 'cE f

4

64dI

Kp hPassive Pressure on Cap




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. 1 of 12 of dia. 20 mmy

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.

sd d

u

FDevelopment length l is given by : l = ;where o is the total perimeter of all rebars, Fs=Fzu o ∑∑




5.2 - Design of Pile Cap :

5.2.1.- Check Punching of cleats:

5.2.1.a Check For Compression:


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

Fx 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 cf⎣ ⎦

Load carried by each cleat = 239.64 kN






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

Fx 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 kNWhere, 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 mmdave. = ( 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' 600ρ =0.85*0.85*600

c

y y

ff 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 yc

fM f bd Where

f⎛ ⎞⎜ ⎟⎝ ⎠

(1 0.59 )'

u

yy

c

Md ff 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


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


Consideration is OK, So As = 3208 mm2Min Rebar Required = 0.0015bt = 8437.5 mm2



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

sd

u

FDevelopment length ld is given by : l = ;where o is the total perimeter of all rebars, Fs=Fzu o ∑∑




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 :



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 mmAc = /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 yc

c c

Nf A

Mf A hA fA 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


fc = 30.00 MPa

M = Moment = 309150000.00 N.mm

so = 0.061

And = 0.061For above values of & = 0.28 ( From chart of Annexure-2 )

Hu


Rebar Dia = 25 mmSo 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.

Segm

ent L

engt

h of

pile

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.


Kp h

h= 1

st

Passive Pressure on Pile

p1Moment at aheight is * k γh*h*Pile Dia*h/3 =0.02uh H h




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 mm2Minimum 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.




Annexure-1: Reinforcement Chart for Chimney




Annexure-2: Reinforcement Chart for Pile


1st Subm. 17-Apr-11 Md. Giasuddin

Foundation Design Calculation of Tower Type 2DT6 For Soil Category-3

Submission Status

Date

AUTHORITY NAME & SIGN DATE Paper Size Language Total Sheets

DESIGNED BYMd. Giasuddin

17-Apr-11 For approval A4 English 13

CHECKED BYMd. Giasuddin

For construction Scale : N/ARevision1st 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)

POWER GRID COMPANY OF BANGLADESH LIMITED

Contents Page No.

1. General. 03

1.1 Foundation Loads 03

Foundation of Tower Type 2DT6 for SC-3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3)

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 05g oad ga Up 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 085.2 - 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

Annexure-2 13

Giasuddin Date : 17 April '11

POWER GRID COMPANY OF BANGLADESH LIMITEDFoundation of Tower Type 2DT6 for SC-3 FOR

1. General.

1.1 Foundation Loads :

Foundation of Tower Type 2DT6 for SC 3 FOR BIBYANA - COMILLA 230kV TRANSMISSION LINE (LOT-3)

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 2D1Applied 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

1.351.23

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.

Md. Giasuddin Page 3 of 13 Date : 17 April '11



1.8 Layout Plan Of the Foundation

450 1800 1800 450

450

45018001800450

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

45018001800450

450

2. Residual Shear Calculation :

Fxleg FylegFxRes

= 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

Vertical LoadsFz ( kN )Items

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

Leg Shear ( kN ) = Fz*Tan




3. Foundation Geometry :

Size of the column = 900 mmX900 mm.

Dia of the Pile, Dp = 600 mm.

h'' = 280.5 mm.

h' 400h' = 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:

yV xV 2 2

M *d1yR M *d1xR = ± ±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 :


So Rcmax = 698.83 kNs. ( Pile weight is to be considered during Pile schedule)

4.2 - Pile Design Load Against Uplift :

∑ ∑ 22 diydix

yzc xCmax 2 2


g g p


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 UpliftSay 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.

yzt xTmax 2 2





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

1which 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.


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

b dL


4.4 - Check for pile head deflection:

For Max Compression:


Fy = Leg Shear = 1007.31 kNPassive resistance by Cap Only ( Same in x and y face)

109 27 kN

a

1Passive 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


Vres=Sqrt.(898.04^2+898.04^2)=1270.02 kN


b'GL

Cap Top

300


pPassive resistance by Pile Cap is k γ*(1.55+0.30)*1.25*4.5 =2

For Max Uplift:


Fy = Leg Shear = 906.8 kN

Net Fx = Leg Shear = 797.53 kN


Vres=Sqrt.(797.53^2+797.53^2)=1127.88 kN


Design shear carried by a single Pile Qmax = 158.75 kN Kp hCap 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.

5Where, 1 andT EI K4700 'cE f

4

64dI

Kp hPassive Pressure on Cap




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 :



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 :


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. 1 of 12 of dia. 20 mmy

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.

sd d

u

FDevelopment length l is given by : l = ;where o is the total perimeter of all rebars, Fs=Fzu o ∑∑




5.2 - Design of Pile Cap :

5.2.1.- Check Punching of cleats:

5.2.1.a Check For Compression:


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

1/ 2

1.19 ' ( / 2)

.1 19 '

c

y

P f b t r x

Fx t w r t

f⎡ ⎤⎢ ⎥⎣ ⎦


( 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 cf⎣ ⎦

Load carried by each cleat = 239.64 kN






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

Fx 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 kNWhere, 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 mmdave. = ( 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' 600ρ =0.85*0.85*600

c

y y

ff 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 yc

fM f bd Where

f⎛ ⎞⎜ ⎟⎝ ⎠

(1 0.59 )'

u

yy

c

Md ff 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


Area of steel, As = M*1000000/(0.9*fy*(d-a/2)) =4433 mm2.


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



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


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


Consideration is OK, So As = 3212 mm2Min Rebar Required = 0.0015bt = 8437.5 mm2



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

sd

u

FDevelopment length ld is given by : l = ;where o is the total perimeter of all rebars, Fs=Fzu o ∑∑




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 :



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 mmAc = /4h2 = 282743.3 Sqmm.

c = 1.5Pile Section at Upper Segment

1.5

1.5

1.5

c

c c

c

c c

tot yc

c c

Nf A

Mf A hA fA f

⎛ ⎞⎜ ⎟⎝ ⎠

⎛ ⎞⎜ ⎟⎝ ⎠

⎛ ⎞⎜ ⎟⎝ ⎠


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 )


Rebar Dia = 25 mm

Pile Section at Upper Segment

So Nos. of Bar = 9 Nos.

6.1.2 Design for Tension Plus Bending


fc = 30.00 MPa

M = Moment = 319670000.00 N.mm

so = 0.061

And = 0.063For above values of & = 0.3 ( From chart of Annexure-2 )

Pile Section at Lower Segment

Hu


Rebar Dia = 25 mmSo 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.

Segm

ent L

engt

h of

pile

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.


Kp h

h= 1

st

Passive Pressure on Pile

p1Moment at aheight is * k γh*h*Pile Dia*h/3 =0.02uh H h




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 mm2Minimum 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.




Annexure-1: Reinforcement Chart for Chimney




Annexure-2: Reinforcement Chart for Pile


Transmission Tower Foundation Design

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