Duration Effects of Near-Fault Ground Motions on Structural Seismic Responses

This study reveals the duration effects of near-fault ground motions with distinct long-period pulse and without pulse on structural seismic responses and damage. To this end, several velocity-based duration measures (DMs) are proposed according to the characteristic of abundant low-frequency content in near-fault records, and non-structural compound intensity measures (IMs) incorporating DMs are suggested. Moreover, the correlations between the IMs and DMs of near-fault ground motions, as well as those between the IMs and DMs of ground motions and the seismic responses (i.e. maximum displacement D-max, input energy E-I and hysteretic energy E-H) of bilinear single-degree-of-freedom (SDOF) systems, are scrutinized. It is shown that the acceleration-based absolute uniform durations present strong correlation with the acceleration-related IMs, while the velocity-based absolute uniform durations highly correlate with the velocity- and displacement-related IMs. In the short-period region, the acceleration-based absolute uniform duration U-0.10 g is well correlated with the seismic responses, while in the medium-, medium-long- and long-period regions, the velocity-based absolute uniform duration U-v10 exhibits strong correlation. Additionally, the compound IMs combining with uniform durations (PGA center dot U-0.10 g and PGV center dot U-v10) are the competent indices to quantify duration effects of near-fault records. The similar observations for duration effects are validated by four representative frame buildings considering Bouc-Wen hysteretic behavior without or with degradation of strength and stiffness.