250+ TOP MCQs on Design Strength of Laterally Supported Beams – II and Answers

Design of Steel Structures Problems on “Design Strength of Laterally Supported Beams – II”.

1. The design bending strength of beams when V ≤ 0.6Vd is given by
a) β_b /Z_pf_y γ_m0
b) β_bZ_pf_y / γ_m0
c) β_bZ_p /f_y γ_m0
d) β_bZ_pf_y γ_m0
Answer: b
Clarification: The design bending strength of beams when V ≤ 0.6Vd is given by M_d = β_bZ_pf_y / γ_m0 , where β_b is a constant, Z_p = plastic section modulus of cross section, f_y is yiled stress of material, γ_m0 = 1.1,partial safety factor.

2. The value of β_b in the equation of design bending strength for plastic section is given by
a) 1.5
b) 2.0
c) 0.5
d) 1.0
Answer: d
Clarification: The value of β_b in the equation of design bending strength is 1 for plastic and compact sections. The value of β_b in the equation of design bending strength for semi-compact section depends on section modulus.

3. The value of β_b in the equation of design bending strength for semi-compact section is given by
a) Z_e/Z_p
b) Z_eZ_p
c) Z_p/ Z_e
d) Z_e+Z_p
Answer: a
Clarification: The value of β_b in the equation of design bending strength for semi-compact section is given by β_b = Z_e/Z_p , where Z_e, Z_p are elastic and plastic moduli of the cross section.

4. The check for design bending strength for simply supported beams is given by
a) M_d = 2.4Z_pf_y/γ_m0
b) M_d < 1.2Z_pf_y/γ_m0
c) M_d ≤ 1.2Z_pf_y/γ_m0
d) M_d ≥ 1.2Z_pf_y/γ_m0
Answer: c
Clarification: The check for design bending strength for simply supported beams is given by M_d ≤ 1.2Z_pf_y/γ_m0 to ensure that onset of plasticity under unfactored loads is prevented.

5. The check for design bending strength for cantilever beams is given by
a) M_d = 2.4Z_pf_y/γ_m0
b) M_d ≤ 1.5Z_pf_y/γ_m0
c) M_d ≤ 1.2Z_pf_y/γ_m0
d) M_d ≥ 1.5Z_pf_y/γ_m0
Answer: b
Clarification: The check for design bending strength for cantilever beams is given by M_d ≤ 1.5Z_pf_y/γ_m0 to ensure that onset of plasticity under unfactored loads – dead loads, imposed loads and wind load- is prevented.

6. The design bending strength for slender sections is given by
a) M_d = Z_ef_y‘
b) M_d = f_y‘
c) M_d = Z_e /f_y‘
d) M_d = Z_e +f_y‘
Answer: a
Clarification: The design bending strength for slender sections is given by M_d = Z_ef_y‘ , where Z_e is elastic section modulus of cross section and f_y‘ is reduced design strength for slender sections.

7. IS 800 permits bolt holes in the flanges to be ignored when
a) 0.9f_uA_nf/γ_m1 ≤ 2f_yAgf/γ_m0
b) 0.9f_uA_nf/γ_m1 ≤ f_yAgf/γ_m0
c) 0.9f_uA_nf/γ_m1 ≥ f_yAgf/γ_m0
d) 0.9f_uA_nf/γ_m1 ≤ 0.5f_yAgf/γ_m0
Answer: c
Clarification: IS 800 permits bolt holes in the flanges to be ignored when the tensile fracture strength of flange is at least equal to tensile yield strength i.e. when 0.9f_uA_nf/γ_m1 ≥ f_yAgf/γ_m0 or (A_nf/Agf) ≥ (f_y/f_u)x(γ_m1 /γ_m0)x(1/0.9), where A_nf/Agf = ratio of net area to gross area of tension flange, f_y/f_u = ratio of yield stress to ultimate stress of material, γ_m1 /γ_m0 = ratio of partial safety factors against ultimate stress to yield stress.

8. The moment capacity of semi-compact section for V > 0.6V_d is given by
a) M_d = Zef_yγ_m0
b) M_d = Zef_y
c) M_d = f_y/γ_m0
d) M_d = Zef_y/γ_m0
Answer: d
Clarification: Few I-and channel sections are semi-compact because of width-thickness ratio. The moment capacity of semi-compact section for V > 0.6V_d is given by M_d = Zef_y/γ_m0, where Ze = elastic section modulus of whole section, f_y = yield stress of material, γ_m0 = partial safety factor.

Design of Steel Structures Problems,