B Pile cap design and structural analysis PDF

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DEPARTMENT OF CIVIL ENGINEERING

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IIT -D

IIT DELHI

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Dr. Suresh Bhalla Professor Tel: 2659-1040 Email: [email protected] 08/10/2019

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IIT -D

PILES PRECAST

CASED

UNCASED

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CAST-IN-SITU

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WHEN PILES SHOULD BE USED??

IIT -D

Soil is too weak

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Predominantly lateral loads High possibility of uplift

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Under marine environment

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The structural engineer should choose foundation type in consultation with the Geotechnical Engineer. 08/10/2019

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INPUTS FROM SOIL REPORT

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Pile type, diameter and length Load capacity in compression

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Load capacity in uplift

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Lateral load capacity

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In addition, good Geotechnical Engineers generally provide pile reinforcement. Otherwise, they should provide details of lateral load analysis. 08/10/2019

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(1)

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DESIGN OF PILE FOUNDATION SYSTEM Number and layout of piles (pile layout) Will depend on the load and moments at the base of

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the columns.

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(2) Design of pile caps

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NUMBER AND LAYOUT OF PILES Chipped off concrete

Hy

Mx

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Hx

ELEVATION

Hx

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D

P

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PLAN

My

Rebars

IIT -D

My

Min 50mm

Loads and moments must be calculated at the base of the pile cap Pt = P + Overburden Mxt = Mx + Hy * D Myt = My + Hx * D

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NUMBER AND LAYOUT OF PILES Chipped off concrete

Hy

Mx

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Hx

ELEVATION

Hx

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D

P

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PLAN

My

Rebars

IIT -D

My

Min 50mm Min 75mm thick levelling course (1:5:10 lean concrete) 08/10/2019

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NUMBER AND LAYOUT OF PILES Pile forces 3

My

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F1 = (Pt /4)+ (Mxt/2y)+ (Myt/2x)

Hx Hy

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(Compression)

y

Mx

F3 = (Pt /4)- (Mxt/2y)- (Myt/2x)

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Could be negative i.e uplift

x

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Lateral force = sqrt (Hx^2+Hy^2)/4

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Hx

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D

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Must make sure that Max compressive force...