Question

The partial safety factors for material strength are

1. 1.15 for concrete and 1.5 for steel
2. 1.5 for concrete and 1.15 for steel
3. 1.5 for both concrete and steel
4. 1.15 for both concrete and steel

Answer 1

Correct Answer - Option 2 : 1.5 for concrete and 1.15 for steel

Explanation:

Factor of safety:

• It is the ratio of the ultimate strength of a member or piece of material to the actual working stress or the maximum permissible stress when in use.
• The design strength of concrete and steel is obtained by dividing the respective characteristic strengths by appropriate partial safety factors for concrete and steel.
  Factor of safety = \(\rm\frac{Ultimate \ strength}{Working\ stress}\)
• At ultimate loads i.e. at ultimate limit state,
  • ​​Partial safety factor for concrete = 1.5
  • Partial safety factor for steel = 1.15​
• ​At serviceability limit states, 
  • Partial safety factor for concrete, γc = 1 
  • Partial safety factor for steel, γc = 1