# Design of Steel Structures Questions and Answers – Beam Types and Sections

This set of Design of Steel Structures Multiple Choice Questions & Answers (MCQs) focuses on “Beam Types and Sections”.

1. A beam section is provided on the basis of
(i) section modulus, (ii) deflection, (iii) shear
a) i, ii
b) ii, iii
c) i, iii
d) i, ii and iii

Explanation: A beam section is provided on the basis of (i) section modulus, (ii) deflection, (iii) shear. The beam should be economical with furnishing required modulus of section.

2. Which of the following is not correct?
a) Angles and T section are strong in bending
b) Channels can be used only for light loads
c) I sections are most efficient and economical shapes
d) I section with cover plates are provided when large section modulus is required

Explanation: Angles and T section are weak in bending. Channels can be used only for light loads. I sections (rolled and built-up) are most efficient and economical shapes. I section with cover plates are provided when large section modulus is required. Generally, ISLB or ISMB are provided in such cases.

3. Local buckling can be prevented by
a) limiting width-thickness ratio
b) increasing width-thickness ratio
c) changing material

Explanation: Local buckling of compression members of beam causes loss of integrity of beam cross section. It is a function of width-thickness ratio and can be prevented by limiting width-thickness ratio.

4. Which of the following is true?
a) in case of rolled section, less thickness of plate is adopted to prevent local buckling
b) for built-up section and cold formed section, longitudinal stiffeners are not provided to reduce width to smaller sizes
c) local buckling cannot be prevented by limiting width-thickness ratio
d) in case of rolled section, high thickness of plate is adopted to prevent local buckling

Explanation: In case of rolled section, higher thickness of plate is adopted to prevent local buckling. Local buckling cannot be prevented by limiting width-thickness ratio. For built-up section and cold formed section, longitudinal stiffeners are provided to reduce width to smaller sizes.

5. Which of the following is not true?
a) only plastic section can be used in intermediate frames
b) slender sections are preferred in hot rolled structural steelwork
c) compact sections can be used in simply supported beams
d) semi-compact sections can be used for elastic designs

Explanation: Only plastic section can be used in intermediate frames which form collapse mechanism. Compact sections can be used in simply supported beams which fail after reaching Mp at one section. Semi-compact sections can be used for elastic designs where section fails after reaching My at extreme fibres. Slender sections are not preferred in hot rolled structural steelwork, but they are extensively used in cold formed members.
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6. 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.

7. 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.

8. 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.

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