Question

A live load 20 kN/m, 6 m long, moves on a simply supported girder AB 12 m long. For maximum bending moment to occur at 4 m from left end A, where will the head of load be, as measured from A?

• A. 8 m
• B. 6 m
• C. 10 m
• D. 4 m

Answer 1

The correct option is A 8 m

Let C be the given section where bending moment is maximum.

$\therefore$ AC = 4 m and BC = 8 m

Let the head of the load after crossing the section C be at a distance 'a' from C.

For the bending moment at C to be maximum,

Average load on AC = Average load on BC

$\Rightarrow \frac{w(6-a)}{AC}=\frac{wa}{BC}$

$\Rightarrow \frac{6-a}{4}=\frac{a}{8}$



$\Rightarrow a=4m$

$\therefore$ Head of load from A = AC + a = 8 m