A reinforced concrete beam is subjected to 5 kNm bending moment due to dead load and 25 kNm bending moment due to live load. What should be the design bending moment for limit state of collapse? 

A reinforced concrete beam is subjected to 5 kNm bending moment due to dead load and 25 kNm bending moment due to live load. What should be the design bending moment for limit state of collapse?  Correct Answer 45.0 kN.m

Explanation

Given:

Moment due to Dead load (DL) = 5 kNm;

Moment due to live load (LL) = 25 kNm;

Moment due to Seismic Load  (EL) = 0 kNm

We know

Design bending moment is Maximum of the following

1) Mu considering moment due to dead load and live load

Mu = 1.5 (DL + LL) = 1.5 × (5 + 25) = 45 kN-m

2) Mu considering moment due to dead load and Seismic load

Mu = 1.5 (DL + EL) = 1.5 × (5 + 0 ) = 7.5 kN-m

3) Mu considering moment due to dead load, live load and seismic load together

Mu = 1.2 (DL + LL + EL) = 1.2 × (5 + 25 + 0) = 36 kN-m.