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Design of Cantilevered

Retaining Walls

CE A433 RC Design

T. Bart Quimby, P.E., Ph.D.Spring 2009

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Introduction

A cantilever retaining wall is a system ofcantilever slabs (i.e. beams) that retain

soil. The key is to draw the appropriate FBDs

so that you can determine the internal

forces.

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Cantilever Retaining Wall

Shear Key

Toe

Stem

Heel

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Forces ACTING ON the Wall

Wall

Footing

Shear Key

Soil on Toe

Soilon

Heel

Active

LateralSoilPressure

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Reactions

PassiveLateral SoilPressure

Vertical

Reaction

Friction

ACTUAL FRICTIONis not the same as

FRICTION CAPACITY!

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Computing Soil Bearing Stress

Resolve applied forcesinto a concentricvertical force and

moment on the contactarea.

Ix = bL3/12

A = bL

c = L/2

smax = P/A + Mc/Ix smin = P/A Mc/Ix

P

M

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Sliding

DrivingForce

ResistingCapacity

Vslide =Driving Force= Demand

Vresist = sum(Resisting

Forces) = Capacity

FS =Vresist /Vslide

Design forFS > 1.5

Friction CAPACITY = N

Not Actual Friction Reaction

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Overturning

Driving

Force

Point ofRotation

ResistingForces

MOT =Driving Force*arm= Demand

MROT = sum(Resisting

Moments) = Capacity

FS = MROT / MOT

Design forFS > 2.0

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Draw FBDs

Stem

ToeHeel

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Stem Diagrams

FBD

Shear Moment

Capacity

Capacity

Makestemthick

enoughfor shear

Select Steel to provide flexural capacity

AddT&SSteel

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Toe

Shear

Moment

Design Shear

Design Moment

Vu can becalculated adistance d from

face of wall sincethere is acompressivereaction with thewall.

Mu is computed atthe face of thewall.

Flexural Steelextends a

development

length into theheel and shoulddevelop withinthe length of

the toe.

Add T&S Steel

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Heel

Shear

Moment

Design Shear

Design Moment

Vu must becalculated at theface of wall since

there is a tensilereaction with thewall.

Mu is computed atthe face of thewall.

Flexural Steelextends a

developmentlength into thetoe and shoulddevelop withinthe length of

the heel.

Add T&S Steel

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