1. As per IS specification, the beam sections should be
a) not symmetrical about any principal axes
b) at least symmetrical about one of the principal axes
c) symmetrical about all principal axes
d) unsymmetrical about all principal axes
Explanation: The beam sections should be at least symmetrical about one of the principal axes as per IS specification. Angle and T-sections are inherently weak in bending while channels can only be used for light loads. Rolled I0section is generally preferred as beam.
2. Which of the following is the design criteria for beams?
(i) Strength in bending (ii) stiffness (iii)economy
a) ii only
b) i and iii
c) ii and iii
d) i, ii and iii
Explanation: Beams should be proportioned for strength in bending keeping in view the lateral and local stability of compression flange. beam should have adequate strength to resist applied bending moments and accompanying shear forces. Beams should be proportioned for stiffness, keeping in mind the deflections and deformations under service condition. Beams should be proportioned for economy. Member should be safe against buckling.
3. Which of the following is not true?
a) for optimum bending resistance, beam material should be near neutral axis
b) for optimum bending resistance, beam material should be far away from neutral axis
c) for optimum bending resistance, web area of beam has to be adequate for resisting shear
d) maximum bending and maximum shear usually occur at different cross section
Explanation: For optimum bending resistance, beam material should be far away from neutral axis and web area of beam has to be adequate for resisting shear. Maximum bending and maximum shear usually occur at different cross section. in continuous beams, they may occur at same cross section near interior supports, but interaction effects are normally neglected.
4. Which of the following assumptions is not an ideal beam behaviour?
a) local and lateral instabilities of beam are prevented
b) any form of local buckling is prevented
c) compression flange of beam is restrained from moving laterally
d) compression flange of beam is not restrained from moving laterally
Explanation: Two important assumptions are made to achieve ideal beam behaviour: (i) compression flange of beam is restrained from moving laterally, (ii) any form of local buckling is prevented. A beam loaded predominantly in flexure would attain its full moment capacity if local and lateral instabilities of beam are prevented.
5. To ensure that compression flange of beam is restrained from moving laterally, the cross section must be
a) plastic
b) semi-compact
c) slender
d) thin
Explanation: To ensure that compression flange of beam is restrained from moving laterally, the cross section must be plastic or compact. if significant ductility is required, section must invariably be plastic.
6. What are laterally restrained beams?
a) adequate restraints are provided to beam
b) adequate restraints are not provided to beam
c) economically not viable
d) unstable beams
Explanation: In laterally restrained beams, adequate restraints are provided to beam in plane of compression flange.
7. Characteristic feature if lateral buckling is ___________
a) entire cross section do not rotate as rigid disc without any cross sectional distortion
b) entire cross section rotates as rigid disc without any cross sectional distortion
c) entire cross section rotates as rigid disc with cross sectional distortion
d) entire cross section do not rotate as rigid disc
Explanation: The characteristic feature if lateral buckling is entire cross section rotates as rigid disc without any cross sectional distortion. This behaviour is similar to axially compresses long column which after initial shortening in axial direction, deflects laterally when it buckles.
8. Lateral buckling in beam is _________
a) does not occur in beam
b) one dimensional
c) two dimensional
d) three dimensional
Explanation: Lateral buckling in beam is three dimensional in nature. It involves coupled lateral deflection and twists that is when beam deflects laterally, the applied moment exerts a torque about the deflected longitudinal axis, which causes the beam to twist.
9. What is elastic critical moment?
a) bending moment at which beam do not fail by lateral buckling
b) bending moment at which beam fails by lateral buckling
c) shear force at which beam do not fail by lateral buckling
d) shear force at which beam fails by lateral buckling
Explanation: Bending moment at which beam fails by lateral buckling when subjected to a uniform end moment is called elastic critical moment.
10. Which of the following is not a method for providing effective lateral restraints?
(i) by embedding compression flange inside slab concrete
(ii) by providing shear connectors in compression flange
(iii) by bracing compression flanges of adjacent beams
a) i only
b) i, iii
c) ii, iii
d) i, ii, iii
Explanation: Effective lateral restraints can be provided by embedding compression flange inside slab concrete, by providing shear connectors in compression flange and embedding in concrete slab, by providing torsional bracings in the compression flanges of adjacent beams preventing twists directly.