# Design of Steel Structures Questions and Answers – Properties of Steel

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

1. Steel is mainly an alloy of
a) Iron and Carbon
b) Sulphur and Zinc
c) Zinc and tin
d) Phosphorous and Tin

Explanation: Steel is alloy of iron and carbon. Apart from carbon, a small percent of manganese, sulphur, phosphorous, chrome, nickel, and copper are added to give special properties to steel.

2. Which of the following is a disadvantage of Steel?
a) High strength per unit mass
b) High durability
c) Fire and corrosion resistance
d) Reusable

Explanation: Steel has high strength per unit mass, highly durable, and is reusable. But steel is poor in fire and corrosion resistance, it needs to be protected.

3. Elastic Modulus of Steel is __________
a) 1.5 x 109 N/mm2
b) 2.0 x 105 N/mm2
c) 2.0 x 105 N/m2
d) 1.5 x 109 N/m2

Explanation: Elastic modulus = Stress/Strain. As per IS 800-2007, elastic modulus of steel is 2.0 x 10⁵ N/mm².

4. Unit mass of Steel = ________
a) 785 kg/m3
b) 450 kg/m3
c) 450 kg/cm3
d) 7850 kg/m3

Explanation: As per IS 800-2007, unit mass of steel is 7850 kg/m³. A steel member with small section which has little self-weight is able to resist heavy loads because steel members have high strength per unit weight.

5. Poisson’s ratio of steel is ________
a) 0.1
b) 1.0
c) 0.3
d) 2.0

Explanation: Poisson’s ratio = transverse strain/axial strain. As per IS 800-2007, Poisson’s ratio of steel is 0.3 in elastic range and it is 0.5 in plastic range.
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6. Structural Steel normally has carbon content less than _______
a) 1.0%
b) 0.6%
c) 3.0%
d) 5.0%

Explanation: Structural Steel normally have a carbon content less than 0.6%. Carbon content increases hardness, yield and tensile strength of steel but it decreases ductility and toughness.

7. What is the permissible percentage of Sulphur and Phosphorous content in steel?
a) 0.1%, 0.12%
b) 1.0%, 3.0%
c) 3.0%, 1.0%
d) 1.0%, 1.0%

Explanation: Sulphur content is generally between 0.02 – 0.1%. If more than 0.1%, it decreases strength and ductility of steel. If Phosphorous is more than 0.12%, it reduces shock resistance, ductility and strength of steel.

8. What happens when Manganese is added to steel?
a) decreases strength and hardness of steel
b) improves corrosion resistance
c) decreases ductility
d) improves strength and hardness of steel

Explanation: Manganese is added to improve strength and hardness of steel . Based on Manganese content, steel are classified as Carbon Manganese steel (Mn >1%) and Carbon Steel (Mn <1%). If its content exceeds 1.5%, it increases the formation of martensite and hence decreases ductility and toughness.

9. Which of the following is the effect of increased content of Sulphur and Phosphorous in Steel ?
a) yields high strength
b) affects weldability
c) increases resistance to corrosion
d) improves resistance to high temperature

Explanation: When sulphur and phosphorous is used beyond 0.06%, it imparts brittleness and affects weldability and fatigue strength.

10. Which of the following is added to steel to increase resistance to corrosion?
a) Carbon
b) Manganese
c) Sulphur
d) Copper

Explanation: Addition of small quantity of copper increases resistance to corrosion. Even Chrome and Nickel are added to impart corrosion resistance property to steel.

11. Which of the following properties are affected due to addition of carbon and manganese to steel?
(i) tensile strength and yield property (ii) Ductility (iii) Welding (iv) Corrosion resistance
a) i and ii only
b) i and iii only
c) i, ii, iii
d) i and iv only

Explanation: Increased quantity of carbon and manganese imparts higher tensile strength and yield properties but lowers ductility which is more difficult to weld.

12. Chrome and Nickel are added to Steel to improve _________
a) corrosion resistance and high temperature resistance
b) strength
c) ductility
d) weldablity

Explanation: Steel is weak in fire and corrosion resistance. So, to improve corrosion resistance and high temperature resistance, chromium and nickel are added to steel.

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