ak singly reinforced beam by working stress method
TRANSCRIPT
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