Stresses Found In Structural Members

Forces Acting Simply Supported Beam

1.Bending

Bending

Support Wall Below

Load Load Applied

A

A

Beam will want to Bend

Bending

Support Wall Below

Load Load

A

A

We would prefer if it did this

Tension Induced

Support Wall Below

Load Load

A

A

Tension Induced

Support Wall Below

Load Load

A

A

Tension

If is does what we want

Counteract Tension

Support Wall Below

Load Load

A

A

Tension

Reinforcement to counteract

Counteract Tension

Support Wall Below

Load

Reinforcement as low as possible

Load Load

Tension

Effe

ctiv

e D

epth

Reo for crack control

Forces Acting Simply Supported Beam

Compression

Compression Induced to Top of Beam

Support Wall Below

Load Load

A

A

Tension

Compression

Usually the Concrete can Withstand without Reo

Compression Acting at Supports

Support Wall Below

Load

Reinforcement as low as possible

Load Load

Tension

Effe

ctiv

e D

epth

Reo for crack control

Compression Acting at Supports

Support Wall Below

Load

Reinforcement as low as possible

Load Load

Tension

Effe

ctiv

e D

epth

Reo for crack control

For high compression reo will prevent surcharge

Compression Acting at Supports

Support Wall Below

Load Load

A

A

Compression Acting at Supports

Wall Below

Load

Section A-A

Compression Acting at Supports

Wall Below

Load

Compression Acting at Supports

Wall Below

Load

Beam compressed against support by load

Compression Acting at Supports

Wall Below

Load

Stirrups placed to prevent bursting

Compression Acting at Supports

Support Wall Below

Load

Stirrups closely spaced to prevent bursting

Load Load

Compression Acting at Supports

Support Wall Below

Load

Stirrups spaced further apart as no compressive force

Load Load

Compression Acting at Supports

Support Wall Below

Load

Stirrups required to support top steel – FRAMING BARS

Load Load

Forces Acting Simply Supported Beam

Shear

Shear Acting On Simply Supported Beam

Support Wall Below

Load Load

A

A

What is Shear?

Shear

2 Types of Shear Forces

• Vertical Shear

• Horizontal Shear

Shear Forces

• Vertical Shear

Shear Forces

Support Walls Below resist downward force

Load Load Load

Shear Forces

No Resistance where there is no support

Load Load Load

Shear Forces

Beam will shear at support

Load Load Load

Shear Forces

Reinforcement at supports to resist shear

Stirrups omitted for clarity

Load Load Load

A

A

B

B

Shear Forces

Support Walls Below resist downward force

Load Load Load

Shear Forces

• Horizontal Shear & Diagonal Shear

Horizontal Shear

Support Wall Below

Load

Reinforcement to Prevent Horizontal Shear if requiered

Load Load

When 2 Types of Shear Forces Meet• Diagonal Tension Cracking

Diagonal Shear

Support Wall Below

Load

Stirrups Prevent Diagonal Shear

Load Load

Multi Span Beam

Load on Continuous span Bean

Support Walls Below

Load Load

Load on Continuous span Bean

Support Walls Below

Load Load

Load on Continuous span BeanLoad Load

Tension Tension

Tension

Forces that act on Beams

Compression

Shear

Bending

BendingCompression

ShearShear

Bending

Shear

Compression

Load Load

Contra flexure

Point of Maximum Bending

Point of Maximum Bending

Point of Maximum Bending

Contra flexure

Bending Reduces

Bending Reduces

Bending Reduces

Contra flexure

ZERO Bending

ZERO Bending

ZERO Bending

Fixed End Beam

Load on Continuous span Bean

Support Walls Below

Load Load

Fixe

d C

onne

ctio

n

Load on Continuous span Bean

Support Walls Below

Load Load

Fixe

d C

onne

ctio

n

Tension Tension

Tension Tension

Compression Acting at Supports

Support Walls Below

Load Load

Compression Acting at Supports

Support Walls Below

Load Load

Fixed End Beams

Support Walls Below

Load

Point of Contra flexure

Load Load

Forces that act on Beams

Fixed or Restrained End

Compression

Shear

Bending

Bending Compression

ShearShear

Bending

Bending

Shear

Compression

Load Load

Cantilevers

Compression Acting at Supports

Support Walls Below

Load Load Load

Compression Acting at Supports

Support Walls Below

Load Load Load

Point of Contra flexure

Forces That Affect Columns

Forces That Affect ColumnsLOAD

Forces That Affect ColumnsLOAD

Bursting Force`

Bursting Force`

Bursting Force`

Bursting Force

Bursting Force

Bursting Force

Compression Acting at Supports

Column compressed by load

Compression Acting at Supports

Stirrups to Counteract

S4[1].03Purnell Bros

Stirrups to prevent Bursting

Forces That Affect Columns

Bending

S4[1].03Purnell Bros

It is difficult to predict which way columns will bend

S4[1].03Purnell Bros

Columns must also be able to withstand mechanical impact

Resist bending

S2 Naremburn Church

Forces That Affect WallsNo Top Restraint

Shear

Forces That Affect Retaining Walls

Forces That Affect Retaining Walls

Footing

Retained Load

Forces That Affect Retaining Walls

Footing

Retained Load

Forces That Affect Retaining Walls

Retained LoadReinforcement in this location is virtually useless

Forces That Affect Retaining Walls

Retained Load

Reinforcement as close as possible to load

Forces That Affect Retaining Walls

Retained Load

Reinforcement as close as possible to load

Reinforcement should be embedded to maximum depth

Forces That Affect Retaining Walls

Retained Load

Reinforcement as close as possible to load

Reinforcement should be embedded to maximum depth

Forces That Affect Retaining Walls

Retained Load

Shear

Forces That Affect Retaining Walls

Retained Load

ShearShear force overcome by Reinforcement at Base

Forces That Affect Retaining Walls

Retained Load Wall will act as a Cantilevered BeamTe

nsio

n

S1 – 21 St Lukes Grammer

St Lukes Grammer S1 -23

S012 Cardiff Markets

Forces That Affect Retaining Walls

Footing

Retained Load

Forces That Affect Retaining Walls

Footing

Retained Load

Forces That Affect Retaining Walls

Retained LoadReinforcement is virtually useless

Tens

ion

Forces That Affect Retaining Walls

Retained Load

Reinforcement as close as possible to load

Tens

ion

Forces That Affect Retaining Walls

Retained Load

Reinforcement as close as possible to load

Reinforcement should be embedded to maximum depth

Tens

ion

Forces That Affect Retaining Walls

Retained Load

Reinforcement as close as possible to load

Reinforcement should be embedded to maximum depth

Tens

ion

Forces That Affect Retaining Walls

Retained Load

Shear

Forces That Affect Retaining Walls

Retained Load

Shear

Shear force overcome by Reinforcement at Base

Forces That Affect Retaining Walls

Wall will act as a Cantilevered BeamTe

nsio

n

S1-21

Forces That Affect Retaining WallsWith Top Restraint

Footing

Retained Load

First Floor Slab

Forces That Affect Retaining Walls

Footing

Retained Load

First Floor Slab

Shear

Shear

Forces That Affect Retaining Walls

Footing

Retained Load

First Floor Slab

Shear

Shear

Forces That Affect Retaining Walls

Retained Load

Shear

Shear

Forces That Affect Retaining Walls

Retained Load

Forces That Affect Retaining Walls

Retained Load

Tens

ion

Tens

ion

Tens

ion

Forces That Affect Retaining Walls

Retained LoadWall will act as beam restrained at ends

Tens

ion

Tens

ion

Tens

ion

Forces That Affect Retaining Walls

Retained LoadReinforcement at Centre as far from load as practical – Maximum Bending

Tens

ion

Tens

ion

Tens

ion

Forces That Affect Retaining Walls

Retained LoadWall will have a point of Contra flexure

Tens

ion

Tens

ion

Tens

ion

Section 11 @ S1-02

Walls not Retaining Loads

Stability

Force

Force may be;• Wind• Earthquake• Impact

Stability

Force

Force may be;• Wind• Earthquake• Impact

Stability

Force

Effective Width

Force may be;• Wind• Earthquake• Impact

Stability

Force

Effective Width

Force may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Embedment is Critical

Stability

Force

Effective WidthForce may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Effective Width Embedment is Critical

StabilityTypical Configuration

Force

Effective WidthForce may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Effective Width

Shear Reinforcement

Tension Reinforcement

Embedment is Critical

StabilityTypical Configuration

Force

Effective WidthForce may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Effective Width

Shear Reinforcement

Tension Reinforcement

Embedment is Critical

Stability

Force

Effective Width

Force may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Effective Width

Force

Embedment is Critical

Stability

Force

Effective Width

Force may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Effective Width

Force

StabilityEffective Width

Force may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Effective WidthEmbedment is Critical

Embedment is Critical

StabilityEffective Width

Force may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Effective WidthEmbedment is Critical

Embedment is Critical

Shear Reinforcement

Tension Reinforcement no need to embedIn base or top

StabilityEffective Width

Force may be;• Wind• Earthquake• Impact

Direction of force may not be predictable

Effective WidthEmbedment is Critical

Embedment is Critical

Shear Reinforcement

Tension Reinforcement no need to embedIn base or top