Design of Steel Structures Multiple Choice Questions 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
Answer: d
Clarification: 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
Answer: a
Clarification: 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
d) changing load on member
Answer: c
Clarification: 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
Answer: d
Clarification: 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
Answer: b
Clarification: 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.
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
Answer: b
Clarification: 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