Question

Four wheel loads of 6 kN, 4 kN,8kN and 5 kN cross a girder of 20 m span followed by uniformly distributed load of 4 kN/m and 4 m long with the 6 kN load leading. The magnitude of bending moment at a section 8 m from the left support is kNm.

• A. 108.4

Answer 1

The correct option is A 108.4

Ordinate of influence line for BM at $C=\frac{8\times 12}{20}=4.8m$
Ordinate under 5 kN load $=\frac{4.8}{12}\times 7=2.8m$
Ordinate under 4 kN load $=\frac{4.8}{12}\times 10=4.0m$
Ordinate under 5 kN load $=\frac{4.8}{8}\times 6=3.6m$
Ordinate under head of UDL $=\frac{4.8}{8}\times 4=2.4m$
$\therefore M_C=(6\times 2.8)+(4\times 4)+(8\times 4.8)+(5\times 3.6)+(\frac{1}{2}\times 2.4\times 4\times 4)$
$=108.4kNm$