Question

For a reinforced concrete beam with M 20 concrete with Fe 415 steel, the working moment corresponding to 'balanced failure' by the Limit State Method of Design is A times of the relatable magnitude of the working moment computed by the Working Stress Method. This value of A is nearly

• A. 1.0
• B. 1.5
• C. 2.0
• D. 2.5

Answer 1

The correct option is C 2.0

$\begin{array}{cc}& \text{Working moment by LSM}\\ & =\frac{0.138f_{ck}b{d}^2}{1.5}\\ & \text{Working moment by WSM}\\ & =0.130{\sigma }_{cbc}b{d}^2\\ \therefore A& =\frac{0.138f_{ck}b{d}^2}{1.5\times 0.13\times {\sigma }_{cbc}\times b{d}^2}\\ & =\frac{0.138\times 20}{1.5\times 0.13\times 7}=2.022\end{array}$