The occurrence of a greater than magnitude 6 earthquake in an urban setting is a rare event; however, structural performance during such an earthquake is an important consideration. Unique to the near-fault region (less than 10 km) is the occurrence of a large pulse in the velocity time history trace. This large velocity pulse occurs when the conditions of forward directivity are met.
The ability to capture pulse-type ground motions in the near-fault region is of recent development and records of this type are few. The 1994 Northridge, California, and 1995 Kobe, Japan, earthquakes substantially in creased the current database of recorded ground motions. As technologies improve and seismic recording de vices become less expensive and easier to implement, the database of recorded near-fault directivity pulses will increase. For example, numerous devices in the near-fault region captured the recent (1999) Kocaeli, Turkey, and Chi- Chi, Taiwan, earthquakes. The effect of this recent data on previously completed work is discussed.
Correct modeling and design of structures subjected to near-fault, directivity pulse loading require a sound understanding of the pulse characteristics of near-fault motions. This report describes the procedure followed in defining a representative large velocity pulse for laboratory testing. The laboratory testing was sponsored by the Pacific Earthquake Engineering Research Center, University of California, Berkeley. Included in the discussion is an analysis of the factors affecting pulse characteristics.
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