In the Seismic Coefficient Method, the Design Horizontal Seismic Coefficient (Ah) is calculated using which of the following parameters? 1. Zone factor (Z) 2. Importance factor (I) 3. Response Reduction Factor (R) 4. Average Response Acceleration Coefficient (Sa/g) Select the correct combination:
- A1 and 2 only
- B1, 2 and 3 only
- C1, 3 and 4 only
- D1, 2, 3 and 4Correct
Solution
Concept
Design Horizontal Seismic Coefficient
Formula
Ah = (Z / 2) × (I / R) × (Sa / g)
Step-by-step solution
1. Recall the standard formula for the Design Horizontal Seismic Coefficient: Ah = (Z / 2) \* (I / R) \* (Sa / g). 2. Identify all the required parameters in the expression: Zone factor (Z), Importance factor (I), Response Reduction Factor (R), and Average Response Acceleration Coefficient (Sa/g). 3. Verify that all four parameters (1, 2, 3, and 4) are required and select Option (d) as the correct choice.
Explanation
The design horizontal seismic coefficient is calculated using the formula Ah = (Z / 2) × (I / R) × (Sa / g). Since all four parameters—Zone factor (Z), Importance factor (I), Response Reduction Factor (R), and Average Response Acceleration Coefficient (Sa/g)—are required in this formula, option d includes all of them and is correct.
Shortcut
To easily remember all 4 parameters in the formula Ah = (Z / 2) × (I / R) × (Sa / g), use the mnemonic "ZIRS": - Z: Zone factor (Z / 2) - I: Importance factor (I) - R: Response reduction factor (R in denominator) - S: Sa/g ratio (Average response acceleration coefficient)
Common mistake
A common mistake is selecting option B or C by overlooking one of the essential parameters in the formula Ah = (Z/2) × (I/R) × (Sa/g). Students often forget to include the Importance Factor (I) or the Average Response Acceleration Coefficient (Sa/g), mistakenly assuming that the horizontal seismic coefficient depends only on the seismic zone factor and response reduction.
Correct answer: D) 1, 2, 3 and 4