Determine the moment of resistance:

A rectangular beam of size 40 mm × 60 mm is subjected to bending. The maximum bending stress is restricted to 75 N/mm². Determine the moment of resistance of the beam section.

Solution

Section modulus, Z = (1 /6)bd 2

= (1/6) × 40 × (60)² = 24 × 10³ mm³

Moment of resistance, M = σ × Z

                                         = 75 × 24 × 10³

                                         = 1800 × 10³ N mm = 1.8 kN m

Thus, moment of resistance of the beam section = 1.8 kN m.