The Earthquake Engineering Online Archive

Evaluation of seismic code provisions using strong-motion building records from the 1994 Northridge earthquake

Llera, Juan Carlos de la; Chopra, Anil K.

UCB/EERC-97/16, Earthquake Engineering Research Center, University of California, Berkeley, 1997, 308 pages (620/L63/1998)

Given the large network of accelerometers located in the area at the time of the Jan. 17, 1994, Northridge, California, earthquake, the recorded motions obtained during the earthquake probably constitute the richest database of recorded ground motions in world earthquake history. Different sources contribute to this database, the California Strong Motion Instrumentation Program (CSMIP) with 193 stations, the USGS National Strong-Motion Program (NSMP) with 100 permanent stations, the University of Southern California with 71 ground-response stations, and the Los Angeles Dept. of Water and Power (LADWP) with seven stations. In this report, the earthquake responses of eight instrumented buildings of the CSMIP database are studied. These buildings were selected from the 57 CSMIP-instrumented buildings that experienced and recorded strong motions during the earthquake. Intentionally, they cover a wide variety of structural types, including reinforced concrete frame and shear wall structures, steel braced frames and moment-resisting structures, mixed steel-concrete structural types, and steel shear walls. The general purpose of this investigation is to study the earthquake performance of these eight buildings using their recorded motions. More specifically, the investigation is separated into two clearly distinctive parts, a phase that involves interpretation of the recorded motions in buildings without introducing any strong modeling assumption and a second phase that involves a comparison between the analytically predicted response in the building and the actual recorded response. The objectives of the study are (1) to evaluate the existing uncertainty that results from using current code-recommended analysis techniques and (2) to propose improved building analysis procedures that are calibrated using recorded responses. Learning from the recorded motions in these eight buildings is an appropriate description of what was intended in this research. The results consistently show that the uncertainty in building models as used today in practice may lead to predictions of the building response that are in error in some cases up to an order of magnitude. This implies that design procedures must be sufficiently robust to lead to seismic designs that are able to accommodate this uncertainty.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-97-16.pdf (10 MB)