Critical review of current approaches to earthquake resistant design

The ATC-34 project is a five-year joint study by the National Center for Earthquake Engineering Research and Applied Technology Council into response modification factors and other critical seismic code issues. The initial objective of the study was to investigate the bases for the response modification factors used in current seismic codes. The scope of the ATC-34 project was broadened in mid-1993 to include a critical review of, and to recommend conceptual changes to current seismic design practice in the US. This paper presents some of the conclusions drawn to date from the ATC-34 project, outlines conceptual issues related to risk and reliability, describes the quantification of redundancy and configuration in seismic codes, and presents a draft formulation for the response modification factor used in seismic codes in the US.