Question

To avoid the limit state of collapse, the safety of RC structures is checked for appropriate combinations of dead load (DL), live load (LL), wind load (WL) and earthquake load (EQ). Which of the following combinations is not considered?

• A. \(1.5\,\mathrm{DL}+1.5\,\mathrm{LL}\)
• B. \(1.5\,\mathrm{DL}+1.5\,\mathrm{WL}+1.5\,\mathrm{EQL}\)
• C. \(0.9\,\mathrm{DL}+1.5\,\mathrm{WL}\)
• D. \(1.2\,\mathrm{DL}+1.2\,\mathrm{LL}+1.2\,\mathrm{WL}\)

Hint:

For limit state of collapse, wind load and earthquake load are generally considered separately, not together with full factored values. Common combinations include: \[ \boxed{ 1.5(DL+LL),\; 1.5(DL+WL),\; 1.2(DL+LL+WL),\; 0.9DL+1.5WL. } \]

Answer 1

The Correct Option is B

Step 1: Recall the load combinations as per IS 456:2000. Typical factored load combinations include \[ 1.5(DL+LL), \] \[ 1.5(DL+WL), \] \[ 1.2(DL+LL+WL), \] \[ 0.9DL+1.5WL, \] and corresponding combinations with earthquake load (EQ).

Step 2: Identify the incorrect combination. Wind load and earthquake load are not simultaneously considered with a factor of \(1.5\) each in the same load combination. Therefore, \[ \boxed{ 1.5DL+1.5WL+1.5EQL } \] is not a valid design load combination. Hence, \[ \boxed{(B)} \] is the correct answer.