Study On Effects Of Near-fault Velocity Pulse On RC Framed Structures

The first time pulse was observed by seismologists in near-fault ground motions is about two decades ago. Then after more and more records with pulses were found, the researches on velocity pulse were increasing. The historic and current researches were reviewed and their results were summarized here. It is believed that velocity pulse could be able to be destructive to structures and it proved by several earthquakes. But when does it happen when a structure is exposed to velocity pulse and how many effects could the pulse be? Whether the effects of velocity pulse are included by the present design response spectrum? There is on answer about these questions.After collecting mostly all of the records with velocity pulse and classifying them, as to 1994 Northridge earthquake and 1999 ChiChi earthquake, those near-fault records without velocity pulse are also collected, the response spectrums of those with and without pulse records are calculated and graphed, their characteristic periods are also calculated at the same time. Compared those results with the graphs and numbers given by Code For Seismic Design of Buildings, and the response spectrums of the records with and without velocity pulse are compared with each other too. It indicates that compared with the response spectrums of no velocity pulse records, the response spectrums of velocity pulse records have longer maximum number range, as well as bigger numbers at long periods. Compared with the design spectrum, the numbers of the response spectrums of velocity pulse records are bigger from period 0.5 second to 2.5 second and smaller after period 3 second. No matter at site condition I or at site condition â…¡, the characteristic periods of velocity pulse records are more than 2 times bigger than the numbers given by code. So to those near-fault structures, it is necessary to adjust the design response spectrum to fit the effects of velocity pulse.In order to investigate the velocity pulse's effects to structure and whether those effects are included in the presently response spectrum theory, 5 records are chosen from 159 records which have distinguished velocity pulses, and their response spectrums are calculated. According to the same response spectrum, 3 synthesized...