Tough Strength of Materials Questions and Answers on “Bending Stress due to Eccentric Loading”.
1. Eccentrically loaded structures have to be designed for _______
a) Uniaxial force
b) Biaxial force
c) Combined axial force
d) Combined biaxial force
Answer: c
Clarification: When the line of action of the resultant compressive force doesn’t coincide with the centre of gravity of the cross section of the structure, it is called eccentrically loaded structure. They have to be designed for combined axial force.
2. ______ transfer the loads from beams or slabs to footings or foundations.
a) Pedestal
b) Post
c) Rib
d) Column
Answer: d
Clarification: A vertical member whose effective length is greater than 3 times its least lateral dimension carrying compressive loads is called a column. The main function of column is to transfer the loads from the beams or slabs to the footings or foundation.
3. In long columns, the lateral deflection causes at the ______
a) Supports
b) Throughout
c) Midspan
d) Along outer periphery
Answer: c
Clarification: A long column under the action of axial loads deflects laterally causing maximum deflection at the centre. A long column fails due to buckling.
4. Short columns causes deflection in the structure.
a) True
b) False
Answer: b
Clarification: If the ratio of the effective length of the column to the least lateral dimension is less than 12. The column is called a short column. It fails by crushing (pure compression failure) and there is no chance of causing deflections.
5. The approximate percentage of reinforcement provided in a beam varies from _______
a) 1-2%
b) 1-4%
c) 2-3%
d) 3-4%
Answer: a
Clarification: The approximate percentage of reinforcement provided in a beam varies from 1-2%.
Type of Structure | Approx. % of Steel |
Beam | 1-2% |
Slabs | 0.7-1% |
Columns | 1-4% |
6. To avoid the failure of a column by buckling ___________ limits are to be recommended.
a) Slenderness
b) Effective length
c) Kernel
d) Radius of gyration
Answer: a
Clarification: The column dimensions shall be such that it fails by material failure only (crushing due to compression) and not by buckling. To avoid the failure of column buckling clause 25.3 of IS 456 recommends the slenderness limits for the column.
7. According to IS 456- 2000, the minimum eccentricity subjected to a column is __________
a) 30mm
b) 20mm
c) 45mm
d) 50mm
Answer: b
Clarification: No column can have a perfectly axial load. There may be some moments acting due to the imperfection of construction or due to actual conditions of loading when IS 456-2000, recommends that all columns Shall be designed for minimum eccentricity of 20 mm.
8. Radius of gyration is denoted by _________
a) k
b) n
c) e
d) y
Answer: a
Clarification: The radius of gyration about a given axis is defined as the effective distance from the given axis at which the whole area may be considered or located. It is denoted by “k” or “r”. The units for the radius of gyration are mm.
9. Find the moment of inertia of a rectangular section of 40 mm width and 80 mm depth about the base.
a) 632×104mm4
b) 682×104mm4
c) 734×104mm4
d) 568×104mm4
Answer: b
Clarification:
Moment of inertia of the rectangular section passing through the base is bd3/ 3.
I = bd/3
= 40×(80)3/ 3
= 682.66×104mm4.