Question

A simply supported beam has a span of 12 m. A udl of 30 kN/m of 4 m length crosses the beam from left to right. The maximum bending moment at a section 5 m from left (in kN - m, round off to two decimals) is

• A. 291

Answer 1

The correct option is A 291

Bending moment at C will be maximum when load position is such that the section divides the load in the same ratio as it divides the span.

$\frac{x}{4-x}=\frac{5}{7}$
$7x=20-5x$
$x=\frac{20}{12}=1.667m$
$\sum M_B=0$
$R_A\times 12=30\times 4\times (7+1.667-2)$
$R_A=66.67kN$
$\therefore M_C=66.67\times 5-30\times \frac{{1.667}^2}{2}=291.67kN-m$