Question

Four wheel loads 80 kN, 100 kN, 160 kN and 120 kN spaced 2 m apart roll on a girder from left to right with the 120 kN load leading. The girder has a span of 25 m. For the condition of maximum bending moment at a section 8 m from the left end.

• A. The 120 kN load should be placed at the section
• B. The 80 kN load should be placed at the section
• C. The 160 kN load should be placed at the section
• D. The 100 kN load should be placed at the section

Answer 1

The correct option is D The 100 kN load should be placed at the section



$\begin{array}{cccc}\text{Load}& \text{Average load on AC (}{y}_1\text{)}& \text{Average load on BC}\left(y_2\right)& \text{Remarks}\\ \text{All the loads on span AC}& \frac{80+100+160+120}{8}& \frac{0}{17}=0& y_1>y_2\\ \text{120 kN load cross the section 'C;}& \frac{80+100+160}{8}=42.5& \frac{120}{17}=7.05& y_1>y_2\\ \text{160 kN load also cross the section 'C;}& \frac{80+100}{8}=22.5& \frac{120+160}{17}=16.67& y_1>y_2\\ \text{100 kN load also cross the section 'C'}& \frac{80}{8}=10& \frac{120+160+100}{8}=47.5& y_1<y_2\end{array}$

The 100 kN load should be placed at the section.