# Design of RC Structures Questions and Answers – Beams

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

1. Which of the following is not a factor influencing the joint action of steel and concrete?
a) The bond between steel and concrete
b) Absence of corrosion of steel bars embedded in the concrete
c) Equal expansion of steel and concrete due to appliance of heat
d) Amount of steel

Explanation: Reinforced concrete is a system of concrete reinforced by steel bars where each of the component works rationally. The joint action of steel and concrete is dependent upon:
i) the bond between steel and concrete
ii) absence of corrosion of steel bars embedded in the concrete
iii) equal expansion of steel and concrete due to appliance of heat.

2. A beam is subjected to 200kN(P)force; what should be the force that is applied on the steel(modular ratio m=11)?
a) 173kN
b) 183 kN
c) 193 kN
d) 153 kN

Explanation: The force on the steel=mP/1+m
=11*200/(1+11)=183 kN.

3. A beam is subjected to 180kN(P)force; what should be the force that is applied on the concrete(modular ratio m=11)?
a) 25kN
b) 15kN
c) 5 kN
d) 35kN

Explanation: According to recommendation of IS:456-2000 the force on the concrete=P/(1+m)
=180/12=15kN.

4. What is the effective area of a beam 300*200 mm2 dimension and reinforced with 4 nos of 16mm dia bars(m=11)?
a) 68038.4 mm2
b) 78038.4 mm2
c) 88038.4 mm2
d) 98038.4 mm2

Explanation: IS 456:2000 gives the effective area = A+(m-1)As
=(300*200)+10*3.14*16*16/4=68038.4 mm2.

5. Straight line theory is one of the theories that can analyse reinforce concrete.
a) False
b) True

Explanation: For the analysis of reinforced concrete straight line theory or elastic theory is an effective one. There is one more theory that can analyse the reinforced concrete i.e. ultimate load theory or limit state theory.

6. What is the result of the tensile stress of steel reaching its ultimate value?
a) Beam will fail in tension
b) Beam will fail in compression
c) Beam will fail in moment
d) Beam will fail in torque

Explanation: If the tensile stress of the beam reaches its ultimate value: i.beam will fail in tension; ii. local crushing of concrete will occur at the top; iii. The beam would pop open.

7. A beam of 1000mm2 dimension is reinforced with 100 mm2 steel. What is the net increase of equivalent uncracked area(m=11)?
a) 1000 mm2
b) 2000 mm2
c) 3000 mm2
d) 4000 mm2

Explanation: According to the codal provision the equivalent uncracked area is = (m-1)Asteel
= (11-1)*100 mm2 = 1000 mm2.

8. A beam of 2000mm2 dimension is reinforced with 200 mm2 steel. What is the net increase of equivalent cracked area(m=11)?
a) .43
b) .83
c) .73
d) .63

Explanation: According to the codal provision the equivalent uncracked area is = (m)Asteel
= (11)*200 mm2 = 2200 mm2.

9. The assumption of elastic theory is the Young’s modulus is constant in all sections of the concrete beam.
a) True
b) False

Explanation: In elastic theory the Young’s modulus is assumed to be constant at all the sections and does not vary as the function of the duration of stress. Young’s modulus is generally determined by secant method.

10. The steel reinforcement does not have an initial stress value when it is embedded in the concrete.
a) True
b) False

Explanation: The application of elastic theory is based on some assumptions. One of these assumptions is the steel reinforcement is free from initial stresses and hence prestressed concrete is not analysed by this method.

Sanfoundry Global Education & Learning Series – Design of RC Structures

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