Design of RC Structures Questions and Answers – Singly Reinforced Beams – Moment of Resistance

This set of Design of RC Structures Multiple Choice Questions & Answers (MCQs) focuses on “Singly Reinforced Beams – Moment of Resistance”.

1. A beam has depth d. If its depth is doubled then what will be its effect on section modulus?
a) It will get double
b) It will get 4 times
c) It will be half
d) It will remain same

Explanation: Section modulus = 2times of depth
So if depth is doubled then it will become 4 times.

2. The resistance offered by the beam against bending moment is called ________
a) Moment of Resistance
b) Resistance
c) Shear Resistance
d) Punching Shear

Explanation: Moment of Resistance is the resisting moment offered by a beam section to resist the bending moment at the section.

3. Determine the moment of resistance for the beams shown in the following figure. Assume grade of concrete as M20 and steel as Fe250.

a) 166.8
b) 146.8
c) 156.7
d) 150.7

Explanation: Mu = 0.87 fy Ast (d – 0.42 xu)
= 0.87(250) (1963) {450 – 0.42(197.66)}
= 156.68 kNm

4. In what case will the MR be equal for tension and compression?
a) Total compression = Total tension
b) Compression > Tension
c) Tension > Compression
d) In under reinforced section

Explanation: MR is equal when the section is balanced which is a case of tension = compression.

5. The section in which quantity of steel required is different in tension and compression.
a) Balanced
b) Under Balanced
c) Over Balanced
d) Unbalanced

Explanation: This is a section in which quantity of steel required is different from that in balanced section.

6. In the case of under reinforced section, when the stress in steel reaches its permissible value, the corresponding extreme compressive stress reached in concrete will be more than its permissible value.
a) True
b) False

Explanation: This is a section in which quantity of steel provided is less than what is required for balanced section.

7. MR for under reinforced section is _____
a) Ast (d – n/3)
b) Ast (n/3 – d)
c) bn. c/2 (d – n/3)
d) bn. c/2 (n/3 – d)

Explanation: The stress t being taken at the allowable stress for steel.

8. MR for over reinforced section is ____
a) Ast (d – n/3)
b) Ast (n/3 – d)
c) bn. c/2 (d – n/3)
d) bn. c/2 (n/3 – d)

Explanation: The stress c being taken at the allowable compressive stress for concrete.

9. Relation to find the effective depth of actual neutral axis is _______
a) bnc c/2 (d – nc/3) = M
b) bnc d/2 (c – nc/3) = M
c) bnc2/2 (d – c/3) = M
d) bd/2 (c – nc2/3) = M

Explanation: Choose a convenient width b. By equating the moment of resistance to the given BM find the effective depth.

10. Point of contra flexure is also termed as ________
a) Pt. of max. shear force
b) Fixed end
c) Max. BM pt
d) Point of inflexion

Explanation: Point of contra flexure is a point where no bending occurs so it is also called point of inflexion.

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