Question

Calculate the plastic section modulus of a beam which is experiencing a maximum bending moment of 590.63 KN-m (take partial safety factor as 1.10 and yield strength of steel as 250 N/mm²)

1. 2246.64 cm³
2. 1568.16 cm³
3. 1856.15 cm³
4. 2598.77 cm³

Answer 1

Correct Answer - Option 4 : 2598.77 cm³

Calculation:

Given, Bending moment = 590.63 KN-m

Partial safety factor = 1.10 and Yield strength of steel (f_y) = 250 N/mm2

Plastic moment(M_p), 

M_p = Bending moment × F.O.S

      = 590.63 × 1.1

      = 649.693 KN-m

Mp = 649.693 × 10⁶ N-mm

Relation between Plastic moment and plastic section modulus of a beam,

Mp = fy × Zp 

649.693 × 106 = 250 × Zp 

Z_p = 2.59877 × 106 mm³

Zp = 2598.77 cm³.