Isolating the effect of ground-motion duration on structural damage and collapse of steel frame buildings

The debate over the significance of ground-motion duration is long-standing and the literature on the influence of duration on structural response is extensive. Decoupling of the duration from other characteristics of the ground motion is crucial for accurate quantification of its effect on structural responses. This article presents a new methodology that isolates the duration from the amplitude, frequency content, and rate of energy build-up of the ground motion. This is achieved by selecting short- and long-duration record pairs that are equated on the basis of spectral shape and the slope of the Husid plot. The use of the initial rate of Arias Intensity as a control parameter is novel in the literature. The proposed approach enables the examination of the sole effect of the duration on structural responses of 2-story and 9-story steel frame buildings. We find that the maximum interstory-drift ratios are not generally sensitive to the duration differences between short- and long-duration record sets, whereas the cumulative damage parameters (i.e. dissipated hysteretic energy and Modified Park–Ang Damage Index) of the buildings considered in this study are affected by duration. Finally, we extend the study to collapse limit states and find that duration has a small effect on structural collapse capacity, after controlling three key ground-motion parameters.