GATE 2022 CE (CE1) – Question 52
Consider a simply supported beam PQ as shown in the figure. A truck having 100 kN on the front axle and 200 kN on the rear axle, moves from left to right. The spacing between the axles is 3 m. The maximum bending moment at point R is _________ kNm. (in integer)
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Correct answer: 180
Explanation
The influence line for bending moment at R rises to $ab/L=1(4)/5=0.8$ m at R. Place the heavier rear axle at R; the front axle is then 3 m farther right at x=4 m, where the influence ordinate is $1(5-4)/5=0.2$ m.
The moment is $200(0.8)+100(0.2)=\mathbf{180}$ kNm. The alternative with the front axle at R gives only 80 kNm because the rear axle is off the span.