Tower Crane Foundation Design 24.07.2016

TOWER CRANE FOUNDATION DESIGN Structural Design Report

Prepared by Edifice Consultants Pvt.Ltd

Tower Crane Foundation Design

1.0.0

GENERAL

1.1.0

Scope

This report is prepared to highlight the design calculations for a Tower Crane Foundation. 1.2.0

Brief Structural Description

The dimensions of the Foundation is 6000mmx6000mmx1500mm. The geometric centre of Tower Crane is placed at a eccentricity of 1350mm to the geometric centre of the foundation. (Refer to Annex 1). 2.0.0

DESIGN DATA

2.1.0

Material Properties

2.1.1

Soil

Bearing capacity of soil is 150 kN/m2 Friction angle is 30 2.1.2

Concrete

Density of the Concrete is 24kN/m3

2 Characteristic strength of concrete for columns, beams and slabs is fcu = 25N/mm 2.1.3

Reinforcement Steel

Characteristic strength of reinforcement steel is (Deform bars Type 2) fy = 460N/mm2

2.2.0

Loads

The Foundation reactions (Working loads) given by the ICC are as follows. Moment (M)

= 1598.5 kNm

Axial Force (P)

= 774.4 kN

Horizontal Reaction (H)

=25.2 kN

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Tower Crane Foundation Design

3.0.0

STANDARDS REFERRED

3.1.0

Design codes of practices

Structural use of concrete

BS 8110-Part I: 1997

Structural use of concrete

BS 8110-Part 2: 1985

3.2.0

Manuals and Hand books

Structural Foundation Designer's Manual by W.G Curtin, G.Shaw, G.I Parkinson & J.M Golding.

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Tower Crane Foundation Design

4.0.0

SLS Checks

4.1.0

Checks for bearing

The bearing capacity of the soil is = 150 kN/m2 Base size

= 6mx6mx1.5m

Weight of the base

= 6 × 6 × 1.5 × 24 = 1296kN

Axial Force-P (from the Tower)

= 774.4kN

Eccentricity of to the Axial Force- e p

= 1.350m

Moment -M (from the Tower)

= 1598.5kNm

Horizontal Reaction-H (from the Tower)

= 25.2kN

Hence total axial load on the footing at SLS

= 774.4 + 1296 = 2070.4kN

Hence total Moment on the footing at SLS

= 1598.5 + 774.4 × 1.350 + 25.2 × 1.5 = 2681.74kN

Maximum pressure beneath the footing can be evaluated as below. σmax =

P A

+

6M 2070.4 6 × 2681.74 = + = 57.51 + 74.49 = 132kN/m2 < 150kN/m2 3 2 3 B 6 6

Minimum pressure beneath the footing can be evaluated as below. σmax =

P A

−

6M 2070.4 6 × 2643.94 = − = 57.51 − 74.49 = -16.98kN/m2 < 0kN/m2 3 2 3 B 6 6

Hence Tensile Stress develops beneath the footing. Hence Pressure distribution beneath the footing needs to be readjusted . Assume the Length of the Foundation under compression is Lb

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Tower Crane Foundation Design

Figure 4.1 : Extract from Structural Foundation Designer's Manual

As per Figure 4.1,

Pe + M + Hh 774.4 × 1.350 + 1598.5 + 25.2 × 1.5 p et = = = 1.30m T 2070.4

Lb = 3 ×

 L − e  = 3 ×  6 − 1.3 = 5.1m  2 T   2 

Hence maximum pressure beneath the footing is,

σ

max

=

2T 2 × 2070.4 = = 135.32kN/m2 < 150kNm × BL 6 5.1 b

Hence Bearing Capacity is Ok.

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Tower Crane Foundation Design

4.2.0

Checks for sliding

Weight of the base

= 6 × 6 × 1.5 × 24 = 1296kN

Axial Force-P (from the Tower)

= 774.4kN

Hence total axial load on the footing at SLS

= 774.4 + 1296 = 2070.4kN

Resisting force to the sliding

= 2070.4 × tan30 = 1195.3kN

Horizontal Reaction-H (from the Tower)

= 25.2kN

FOS against sliding

=

1195.3 = 47.4 > 2.5 25.2

Hence FOS against sliding is adequate.

4.3.0

Checks against overturning

Resisting moment

6 = 1296 × + 774.4 × 4.35 = 7256.64kNm 2

Overturning moment

= 1598.5 + 25.2 × 1.5 = 1636.3kNm

FOS against overturning

=

7256.64 = 4.43 > 2.5 1636.3

Hence Foundation is safe against overturning.

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Tower Crane Foundation Design

5.0.0

Ultimate Limit State Design

Assume a F.O.S of 1.5 at Ultimate Limit Stare. 5.1.0

Checks for the Bending

The maximum bending moment at tower face can be found as follows. The Ultimate Pressure at the tower face

= 1.5

 135.32 × 2.475 = 98.50kN/m2  5.1 

1 2.475 M = × 98.50 × 2.475 × = 100.56kNm/m 2 3 (Please note that the moment is calculated for a 1m width strip of the footing) T16 bars to be used as reinforcement. Cover to reinforcement is 50mm.

d = 1500 − 50 − 16 −

16 2

= 1426mm

Consider a Unit Width of the footing (Clause 3.4.4.4 of BS 8110-1:1997)

k=

M f bd2 cu

=

100.56 × 106 25 × 1000 × 14262



k 



0.9 



0.002 



0.9 

z = d0.5 + 0.25 −

z = d0.5 + 0.25 −

= 0.002 < 0.156,Hence compressio n r/f not required.



 = 0.99d > 0.95d

z = 0.95d

As =

M 0.95fy z

=

100.56 × 106 0.95 × 460 × 0.95 × 1426

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= 170mm2 /m

Page 6

Tower Crane Foundation Design

Checks for the minimum amount of reinforcement (As per Table 3.25 of BS 8110-1:1997) A 100 s = 0.13 A c

A s,min =

0.13 × 1000 × 1500 100

= 1950mm2

Provide T16 @ 100 mm C/C Both Ways.

A s ,provided = 2010mm2 /m A s ,provided = 2010mm2 /m Hence the requirement for the minimum reinforcement is satisfactory. ,

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Tower Crane Foundation Design

6.0.0

Checks for shear

6.1.0

Maximum shear stress at Tower face

The Maximum Shear Force at Tower Face, 1 V = × 98.50 × 2.475 = 121.90kN 2

Hence shear stress at column face, v=

121.90 × 103 = 0.09N/mm2 1000 × 1426

Maximum possible shear 0.8 fcu or 5N/mm2 which is lesser

Hence v

max

= 0.8 fcu = 0.8 25 = 4N/mm2

Hence Maximum Shear is OK. 6.2.0

Shear at 1.0 d from the face of the Tower

Design concrete shear strength 100As bd

=

1

100 × 2010 (1000 × 1426)

= 0.14 < 3

1

 400  4 =  400  4 < 1  d   1426  Hence design concrete shear strength is, 1

vc

1

 100As  3  400  4 1 = 0.79 ×   ×  × δm  d   bd  1 1 = 0.79 × (0.14 ) 3 × 1 × 1.25

= 0.33N/mm2 > 0.09N/mm2

Hence shear at 1.0 d is OK.

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Tower Crane Foundation Design

6.3.0

Punching Shear Check

Tower Crane Consists of 4 Tower Legs and each Leg is connected to the Foundation through a Base Plate and Anchor Bolts. Assume the dimensions of the Base Plate is 350mmx350mm. Assume the Tower Moment (1598.5 kNm) is applying from a Diagonal Direction. Hence Maximum Compression force on a Tower Leg due to Moment (diagonal direction) is N = moment

1598.5 = 580kN 2 2 1.95 + 1.95

Assume Tower Axial Force (774.4 kN) is equally carried by the 4 Tower Legs. Hence Axial Force per Leg, N = axial

774.4 4

= 193.6kN

Hence Maximum Tower Leg Reaction is, N = 580 + 193.6 = 773.6kN Leg, max

Hence Punching Shear Stress is,

v=

773.6 × 103 4 × 350 × 1426

= 0.39N/mm2 < 4N/mm2

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E-A

E-B

E-D

E-E

E-F

E-G

E-H

E-J

E-K

E-L

178 2

26800

55212 1600

3800

2400

3600

1800

2800

3000

4200

BOUND

ARY

3617

E-1

2084

4996

400

6200

E-3

300 2000

2200

E-5

E-7

E-9

900

6000

300 3800

BLOCK E

E-13

40600

E-11

E-15

Md

HA

m=1855

3000

E-19

A

3000 1349 975

E-18

676

E-17

E-21

6000 E-23

F-1

LEGEND EDGE OF PHASE II- CAR PARK

2000

END OF EXCAVATION LINE SHEET PILE LINE

3000 LEVEL 1 BUILDING LINE

6000

676

3000

LEVEL 2 BUILDING CANOPY

B 3000

3000

4349 6000

A

1651

1950 3000 1349 975

TEMPORARY SHEET PILE LINE

676

LEVEL 3 BUILDING LINE

3000

BOUND

ARY

E-25

6000

B

A

975 1349 3000 6000