Influence of earthquake duration on structural collapse assessment using hazard-consistent ground motions for shallow crustal earthquakes

This study quantitatively investigates the duration effect on structural collapse assessment, using hazard-consistent ground motion suites selected based on the generalized-conditional-intensity-measure approach. Sixteen scenario cases with varying magnitudes, distances, and conditioning periods are considered as targets. For each target case, four hazard-consistent ground motion suites with different distributions of duration (one base-duration (actual target) suite and three longer-duration suites respectively) are selected. Collapse fragility curves are derived by conducting incremental dynamic analysis on numerical models of four steel frames. Comparative results demonstrate that the duration effect on structural collapse capacity mainly depends on the magnitude of the mean significant duration (Ds(5-75)) ratio of two (longer/base) groups. The duration effect is statistically insignificant for cases where the mean Ds(5-75) ratio is smaller than 1.4, while it is more significant for cases with mean Ds(5-75) ratios larger than 1.4, with a reduction in median collapse capacity of, on average, about 10% when using the longer-duration suites as compared to the base-duration one. It is also found that a longer duration record suite with more cumulative intensity contained has a higher possibility to cause a reduction of structural collapse capacity.