The commentary to ASCE 7 quantifies the intended performance for buildings in different Risk Categories. The below Table summarizes the anticipated reliability values. These values have not been validated with experience or in-depth analysis, but instead are notional values that represent the intent of 48 the building code committee. FEMA P-695 (2009) also suggests that the probability of collapse due to MCER ground motions should be limited to 10% for Risk Category II buildings. FEMA P-695 presents a detailed methodology for determining the collapse probability of classes of buildings. Several case studies have used the methodology to benchmark the performance of modern buildings, with results reported in FEMA P-695 (2009) and NIST (2010).
|
Risk Category |
Probability of Total or Partial Collapse ( % ) |
Probability of Failure that could result in endangerment of individual lives ( % ) |
|---|---|---|
|
I & II |
10 |
25 |
|
III |
6 |
15 |
|
IV |
2.5 |
10 |
Firstly, ASCE 7-16, the earthquake design values for most locations in the United States, have been adjusted so that structures having standard collapse fragility will have a collapse probability of 1% in 50 years.
According to ASCE 7-16, target reliability values for structural stability caused by an earthquake due to MCER earthquake ground motion is given below.
|
Risk Category |
Conditional Probability of Failure ( % ) |
Conditional Probability of Component or Anchorage Failure ( % ) |
|---|---|---|
|
I & II |
10 |
25 |
|
III |
5 |
15 |
|
IV |
2.5 |
9 |