Fixed-End Moment in an L-Shaped Frame
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A planar L-shaped frame has a 4 m vertical column fixed at its base and a 6 m horizontal beam rigidly connected at the top. The beam carries a uniformly distributed load of 5 kN/m over its full length. The moment reaction at the fixed base is most nearly:
- A30 kN·m
- B60 kN·m
- C90 kN·m
- D120 kN·m
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Answer: C. 90 kN·m
The distributed load has resultant wL = 5(6) = 30 kN acting at the beam's midpoint, 3 m horizontally from the column. Taking moments about the fixed base, M = 30(3) = 90 kN·m. The column height does not enter, because the load is vertical and its moment arm is the horizontal distance only. Using the column height instead gives 120 kN·m.
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