Beam Moment from Tributary Floor Load
Mediumtributary widthbending moment
Parallel floor beams span 6 m and are spaced 3 m apart. The floor load is 4 kPa. The maximum moment in one interior beam is most nearly:
- A54 kN·m
- B18 kN·m
- C27 kN·m
- D108 kN·m
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Answer: A. 54 kN·m
Equations: line load on a beam w = (floor pressure) × (tributary width); Mmax = wL²/8. Values: floor load 4 kPa; beams are 3 m apart, so each interior beam collects half the spacing on each side = 3 m; span L = 6 m. Step 1: w = 4 × 3 = 12 kN/m. Step 2: Mmax = 12 × 6²/8 = 54 kN·m. 27 kN·m uses half the spacing (1.5 m); 108 kN·m uses wL²/4; 18 kN·m multiplies the pressure by the span.
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