MEWAR UNIVERSITY

PRESENTATION ON

SINGLY REINFORCED BEAMBY WORKING STRESS

METHOD(D.C.S-1) PRESENTED BY

ABHISHEK KUMARB.TECH,5TH SEM.(SESSION-2012-13)

DEPT. OF CIVIL ENGINEERING

SUBMITTED TO:-ARVIND YADAV SIRASSOCIATE LECTURERDEPT. OF CIVIL ENGINEERING

DEFINITION

• When any concrete beam is reinforced in only tension side with steel, then it is known as singly reinforced beam. It is designed by various methods like• A) working stress method• B) limit state method

WORKING STRESS METHOD

Main assumption of this method is that the modulus of elasticity of concrete is constant at all stresses. So modulus ratio(ratio of modulus of elasticity of steel and concrete) is also constant, i.e.

m = 280/3* cbc

Terms used for formula

• Neutral axis(N.A.)=It is an imaginary line in cross section of beam through which moment of area of compression and moment of equivalent area of tension is equal.

• X= depth of N.A, xbal = depth of N.A. in balanced cond.

• b= width of beam. • d = effective depth of beam• Ast= area of steel.• cbc= compressive strength due to bending in

concrete• st= stress in steel.• m= modular ratio.

Diagram

Determination of Neutral axisBy formulaNeutral axis depth is determined.

Xbal=(93.33/93.99+st )*d

Now by bx*x/2=mAst(d-x)X is determined.When x<xbal.

It is under reinforced beam, otherwise over reinforced beam.

And when x=xbal

It is balanced section

Moment of resistanceFor balanced section Mr=T*z=C*zFor under reinforced

beamMr=T*zFor over reinforced

beamMr=C*z

Where

C=bx* cbc/2

T= st*Ast

Z=(d-x/3)

DESIGN OF A SECTION• Find xbal in terms of d by

Xbal=(93.33/93.99+st )*d• Find Mr in terms of b and d.

Mr=bx* cbc/2 * (d-x/3)

• Choose appropriate b and d ratio.• Equate M= Mr to find b and d.• By C=T we can find Ast

Any queries

?

THANK YOU