Design of Steel Structures Multiple Choice Questions on “Behaviour of Real Beam”.
1. As the beam undergoes bending under applied loads, axial strain distribution at a point in beam
a) axial strain is not produced
b) remains constant
c) varies along depth of beam
d) varies along length of beam
Answer: c
Clarification: As the beam undergoes bending under applied loads, axial strain distribution at a point in beam varies along the depth of beam.
2. The beam buckles elastically if
a) Mcr < My
b) Mcr > My
c) Mcr = My
d) Mcr = 2My
Answer: a
Clarification: If Mcr critical moment of a section is less than yield moment My , then beam buckles elastically.
3. If Mcr > My of a beam section, then
a) beam does not buckle
b) beam buckles fully elastically
c) beam buckles completely plastically
d) some amount of plasticity is experienced
Answer: d
Clarification: When critical moment of a section Mcr is greater than My , some amount of plasticity is experienced at the outer edges before buckling is initiated.
4. Beams with intermediate slenderness fail by
a) elastic buckling
b) inelastic lateral buckling
c) attains Mp without buckling
d) do not fail
Answer: b
Clarification: Beams with intermediate slenderness (0.4 < √Mp/Mcr < 1.2) fail by inelastic lateral buckling at loads below Mp and above Mcr .
5. What are residual stresses?
a) stresses developed during construction
b) stresses developed due to seismic load
c) stresses developed due to vibration
d) stresses developed during manufacturing
Answer: d
Clarification: During the process of manufacture, steel sections are subjected to large thermal expansions resulting in yield level strains in sections. As subsequent cooling is not uniform throughout the section, self-equilibrating patterns of stresses are formed. These stresses are called residual stresses.
6. Which of the following is correct?
a) yielding of section starts at lower moments
b) yielding of section starts at higher moments
c) yielding of section does not start at lower moments
d) yielding of section does not occur
Answer: a
Clarification: Due to presence of residual stresses, yielding of section starts at lower moments. Then with increase in moment, yielding spreads through the cross section.
7. Match the pair
(i) high slender beams (A) attain Mp without buckling (ii) stocky beams (B) fail by inelastic buckling (iii) intermediate slender beams (C) fail by elastic buckling
a) i-A, ii-B, iii-C
b) i-C, ii-B, iii-A
c) i-C, ii-A, iii-B
d) i-A, ii-C, iii-B
Answer: c
Clarification: Beams with high slenderness fail by elastic lateral buckling at Mcr. Beams of intermediate slenderness fail by inelastic lateral buckling at loads below Mp and above Mcr. Stocky beams attains Mp without buckling with negligible lateral deformations.
8. Which of the following is correct?
a) torsional bracing attached to top flange should bend in single curvature
b) torsional bracing attached to top flange should not bend in reverse curvature
c) its flexural stiffness should be 6EIb/S
d) its flexural stiffness should be 4EIb/S
Answer: c
Clarification: Torsional bracing attached to top flange should bend in reverse curvature and its flexural stiffness should be 6EIb/S, where S is spacing between girders.