This set of Design of Steel Structures Problems focuses 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_{p}f_{y} γ_{m0}

b) β_{b}Z_{p}f_{y} / γ_{m0}

c) β_{b}Z_{p} /f_{y} γ_{m0}

d) β_{b}Z_{p}f_{y} γ_{m0}

View Answer

Explanation: The design bending strength of beams when V ≤ 0.6Vd is given by M

_{d}= β

_{b}Z

_{p}f

_{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

View Answer

Explanation: 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_{e}Z_{p}

c) Z_{p}/ Z_{e}

d) Z_{e}+Z_{p}

View Answer

Explanation: 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_{p}f_{y}/γ_{m0}

b) M_{d} < 1.2Z_{p}f_{y}/γ_{m0}

c) M_{d} ≤ 1.2Z_{p}f_{y}/γ_{m0}

d) M_{d} ≥ 1.2Z_{p}f_{y}/γ_{m0}

View Answer

Explanation: The check for design bending strength for simply supported beams is given by M

_{d}≤ 1.2Z

_{p}f

_{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_{p}f_{y}/γ_{m0}

b) M_{d} ≤ 1.5Z_{p}f_{y}/γ_{m0}

c) M_{d} ≤ 1.2Z_{p}f_{y}/γ_{m0}

d) M_{d} ≥ 1.5Z_{p}f_{y}/γ_{m0}

View Answer

Explanation: The check for design bending strength for cantilever beams is given by M

_{d}≤ 1.5Z

_{p}f

_{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_{e}f_{y}‘

b) M_{d} = f_{y}‘

c) M_{d} = Z_{e} /f_{y}‘

d) M_{d} = Z_{e} +f_{y}‘

View Answer

Explanation: The design bending strength for slender sections is given by M

_{d}= Z

_{e}f

_{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_{u}A_{nf}/γ_{m1} ≤ 2f_{y}Agf/γ_{m0}

b) 0.9f_{u}A_{nf}/γ_{m1} ≤ f_{y}Agf/γ_{m0}

c) 0.9f_{u}A_{nf}/γ_{m1} ≥ f_{y}Agf/γ_{m0}

d) 0.9f_{u}A_{nf}/γ_{m1} ≤ 0.5f_{y}Agf/γ_{m0}

View Answer

Explanation: 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

_{u}A

_{nf}/γ

_{m1}≥ f

_{y}Agf/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_{y}γ_{m0}

b) M_{d} = Zef_{y}

c) M_{d} = f_{y}/γ_{m0}

d) M_{d} = Zef_{y}/γ_{m0}

View Answer

Explanation: 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.

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