Question

In limit state design of concrete structures, partial safety factors for material strength of concrete and steel respectively, are taken as:

• A. 1.5 and 1.15
• B. 1.67 and 1.5
• C. 3 and 1.5
• D. 1.5 and 1.2

Hint:

Remember: In LSD (IS 456:2000), use 1.5 for concrete and 1.15 for steel as material partial safety factors.

Answer 1

The Correct Option is A

Step 1: Understanding Limit State Design (LSD).
In limit state design, partial safety factors are applied to material strengths to account for variability, uncertainties, and ensure safety.

Step 2: IS 456:2000 provisions.
According to IS 456:2000, the recommended partial safety factors are: - For concrete: \(\gamma_{m} = 1.5\)
- For steel: \(\gamma_{m} = 1.15\)

Step 3: Why not other options?
- (B) 1.67 and 1.5: These were used in working stress method, not LSD.
- (C) 3 and 1.5: Not relevant to RCC design.
- (D) 1.5 and 1.2: Incorrect values for LSD.

Step 4: Conclusion.
Thus, the partial safety factors for concrete and steel are \(\,1.5 \,\text{and}\, 1.15\).