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# An R.C.C. beam of 6 m span is 30 cm wide and has a lever arm of 55 cm. If it carries a U.D.L. of 12 t per m and allowable shear stress is 5 kg/cm2, the beam

A. Is safe in shear

B. Is safe with stirrups

C. Is safe with stirrups and inclined bars

D. Needs revision of section

This Question Belongs to Civil Engineering >> RCC Structures Design

1. we know that moment M=V*LA where LA is liver arm (for given signs F=verticle shear force, v=horizontal shear force, x=longitudinal distance)
now v=M/LA , also M=F*x
shear stress S=V/(B*x)
S=F/(B*LA)
for question:
S=12000*6/2*(30*55)=21.82 >8 kg/cm^2 hence unsafe

2. Divide 12000 kg with 55*30 we will get 7.27 kg/sqcm but in question allowable shear stress is 5kg/sqcm so it will fail and section needs to be redesign.

3. can any one explain this question

Related Questions on RCC Structures Design

If the shear stress in a R.C.C. beam is

A. Equal or less than 5 kg/cm2, no shear reinforcement is provided

B. Greater than 4 kg/cm2, but less than 20 kg/cm2, shear reinforcement is provided

C. Greater than 20 kg/cm2, the size of the section is changed

D. All the above