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#CALC. No. #

PILE CAP FOR 3 PILE GROUP(3PC1)

A) Pile Cap Details & Load CalculationsPile Cap Details

Size of pile cap Length Lx = m

Lx1 = m

Width Lz = m

Lz1 = m

Depth of the pile cap Hpc = m

Height of soil below HPP h1 = 100 - 99

m

Pedestal Details

Size of Column/Pedestal Height Hp = m

Length lx = m

Width lz = m

Centre of the pedestal from to top edge of pile cap l = m

Z

Design Sheet Axis

P1 l

C.L of Fdn

ZP3 Staad Model Axis

C.L of Fdn

(U/S of base plate) EL

40 thk Grout

EL

2.80

H.P.P

H = 750x750

EL

EL

400

100.000

As the column centre line is located in line with the centre of the piles P1 & P2 and placed in between the piles. So, considered the pile cap acting like a two pile cap with pile P1 & P2 tied with the another pile P3.

2000

100.300

99.000

1500

97.500

750

Based on the above assumption, super structure loads i.e., vertical load(Fy), horizontal loads in z-direction(Fz) and respective moment(Mx) are transferred through piles P1 & P2 and remaining loads horizontal loads in x-direction(Fx) and respective moment(Mz) are transferred through piles P1, P2 & P3.

1850

400

0.80

400

P2 400

1200

SAFETY CALC.:

6.175

0

#REF!

1.850

0.750

2.000

1.000

1.300

X

These pile caps provided at three locations in north west of the platform columns. The staad reactions from the steel structure received from IEC and the reactions are converted into forces on foundations with respect to design sheet access as given below. Reactions have been attached in Appendix-A for reference.

0.750

1.50

APPROVERCHECKER

#REF! #REF!#REF!

X

REV. DATE ORIGINATOR

#REF!

400

650

0.75

0.75

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SAFETY CALC.:

#REF!

APPROVERCHECKER

#REF! #REF!#REF!

REV. DATE ORIGINATOR

#REF!

Pile Details

1

2

Total number of piles n =

Number of piles in line with column in Z-direction n1 =

C.G of the pile group xg = (x )/n = m

C.G of the pile group zg = (z )/n = m

Lever arm between the piles about Z axis Zzz = x1 - x3

m

Section Modulus of Pile group about X axis Zxx = z1 - z2

m

Self Weight of Foundation

Area of pile cap Apc = Lz*Lx1+0.5*(Lz+Lz1)*(Lx-Lx1)

= 2*0.75+0.5*(2+0.75)*(1.85-0.75)

= m2

Area of Pedestal Apd = lz * lx= 0.75*0.75

= m2

Area of soil above the pile cap As = Apc -Apd

= 3.01-0.5625

= m2

Weight of the pile cap Wpc = Apc*Hpc*c

= (3.01*1.5*24)= kN

Weight of the Pedestal Wpd = Apd*Hp*c

= (0.56*1.3*24)= kN

Weight of the soil above the pile cap Ws = As*h1*s

= (2.45*1*18)= kN

Consider Surcharge Load = 10 kN/m2 Wsur = 10*As

= 10*2.45

= kN

Total weight of foundation excluding surcharge weight W = Wpc+Ws+Wpd

= 108.45+44.1+17.55= kN

Total weight of foundation including surcharge weight. W = Wpc+Ws+Wpd+Wsur

= 108.45+44.1+17.55+24.5= kN

Eccentricity of the Pile Cap

C.G of the pile cap weight from top edge of pile cap =

in X-direction

=

= m

194.6

(2 0.75 0.75/2+0.5 (2+0.75) (1.850.75)*(0.75+1/3*(2*0.75+2)/ (2+0.75)))/ (2*0.75+0.5*(2+0.75)*(1.85-0.75))

0.776

(Lz*Lx1*Lx1/2+0.5*(Lz+Lz1)*(Lx-Lx1)*(Lx1+1/3*((2*Lz1+Lz)/ (Lz+Lz1)))/ (Lz*Lx1*Lx1/2+0.5*(Lz+Lz1)*(Lx-Lx1))

17.55

44.10

24.50

170.1

1.200

0.400m m

3.01

0.56

2.45

3

108.45

1.050

2

0.400

3.000 2.250

P1 0.400

3 P3 1.000 1.450

P2 1.600

S.No Pile No.z x

0.750

1.000

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SAFETY CALC.:

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APPROVERCHECKER

#REF! #REF!#REF!

REV. DATE ORIGINATOR

#REF!

Load Calculations

Foundation dead weight on piles * -170.1*0.25 =

** -194.6*0.25

Each support is checked for all the unfactored load combinations and only critical load cases are summarised.

a) Loads at the top of pedestal

b) Loads at the bottom of pile cap(Except Dead Weight of Foundation)

FXB = FX MXB = MX + FZ * H

FYB = FY MZB = MZ - FX * H

FZB = FZ

B) Analysis of Pile Group

a) Check for compression capacity of the pile

Maximum compression load on the Pile

Node No. , L.C

Max compressive load, P1 = FYB/n1 + Fsd - MXB/Zxx - MZB/(Zzz*n1)

= CHECK N.No. & L.C

= kN

P2 = FYB/n1 + Fsd + MXB/Zxx - MZB/(Zzz*n1)

= CHECK N.No. & L.C

= kN

P3 = Fsd - MZB/(Zzz)

= CHECK N.No. & L.C

= kN

The Pile capacity increased by 25%, as the critical loads are combination of the wind loads

1300

1300

1200

649 1400

649 1400

603

629

603

1300

1300

1200

603

629

603

1200 522.2 870.0

-40.1 -422.77 98.64

316.7 Safe!

Safe!

P3

870.0

Check

98.6 870.0

-445.09 258.64

-173.60

Safe!

Safe!

P1

48.65** 48.65

-230.36

-229.60 0.00 -1.40

97.3

Pile-P1 Pile-P2 Pile-P3

42.53* 42.53 85.05Without Surcharge Load(Fd)

With Surcharge Load(Fsd)

3

S.NoSTAAD

NodeNo.Load comb

Pmax Pmax,allow

4 649 1400

1300

1 603

522.18 517.52

792.34 503

2 629

262.64

-162.29

603

-2.80 0.00

kN kN

603 110

CHECK

4 0.50 -561.50 -82.00

258.6 870.0

792.31300

P2

Pile Loads (kN)

0.00 -173.60

2 60.50 -866.00 -60.60 -169.68 0.00 -169.40

1 62.00 1032.70 -62.00

3 82.27 723.00 -1.00

MYB MZB

kN kN kN kNm kNm kNmSTAAD

NodeNo.Load comb

FXB FYB FZB MXB

0.00 0.00 0.00

4 0.50 -561.50 -82.00 0.00 0.00 0.00

0.00 0.00 0.00

2 60.50 -866.00 -60.60 0.00 0.00 0.00

1 62.00 1032.70 -62.00

CHECK

3 82.27 723.00 -1.00

S.No

kN kN kN kNm kNm kNmS.No

STAAD NodeNo.

Load combFX FY FZ MX MY MZ

C.G of the pile group and the pile cap are closer to each other. So, consider the 50% of the dead weight due to self weight of the pile cap and soil weight transferring through pile P3 and remaining 50% equally shared by piles P1 and P2.

Max.Vertical

ECK N.No. &

Min.Vertical

Max.Hor

Min.Hor

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#REF!

b) Check for tension capacity of the pile

Minimum load on the Pile

Node No. , L.C

Min compressive load, P1 = FYB/n1 + Fd - MXB/Zxx - MZB/(Zzz*n1)

= CHECK N.No. & L.C

= kN

P2 = FYB/n1 + Fd + MXB/Zxx - MZB/(Zzz*n1)

= CHECK N.No. & L.C

= kN

P3 = Fd + MZB/(Zzz)

= CHECK N.No. & L.C

= kN

The Pile capacity increased by 25%, as the critical loads are combination of the wind loads

The tension capacity of the piles at node 12 need to increase by increasing the length of the reinforcement in the pile.

c) Check for shear capacity of the pile

Resultant Horizontal Force

Node No. , L.C

Min compressive load, P1 = Sqrt((Fx/n)^2 + (Fz /n1)^2)

= CHECK N.No. & L.C

= kN

P2 = Sqrt((Fx/n)^2 + (Fz /n1)^2)

= CHECK N.No. & L.C

= kN

P3 = Fx/n

= CHECK N.No. & L.C

= kN

The Pile capacity increased by 25%, as the critical loads are combination of the wind loads

36.4 36.4 20.17

P3

786.22 496.88

110

37.26

CHECK

CHECK

37.26 20.67

Check

P3

Unsafe!

Safe!

Safe!

Safe!

Safe!

Safe!

Safe!

Check

3 603 1200 27.4 87.027.43 27.43 27.43

2 629 1300 36.4 87.01 603 1300 37.3 87.0

S.NoSTAAD

NodeNo.Load comb

Hmax Hmax,allow

kN kNPile Loads (kN)

P1 P2

4 649 1400 -428.9 -450.0-46.22 -428.89 83.72

3 603 1200 -134.4 -450.0516.06 511.4 -134.35

2 629 1300 -451.2 -450.0-168.41 -451.21 -76.29

1 603 1300 -80.3 -450.0-80.29

S.NoSTAAD

NodeNo.Load comb

Pmin Pmin,allow

kN kN

Pile Loads (kN)

P1

12 127

12

CHECK

P2

ECK N.No. &

ECK N.No. &

CHECK