Three Proposals for Characterizing MDOF Nonlinear Seismic Response

This paper reviews, compares, and contrasts the three methodologies proposed by C. A. Cornell, by Y. K. Wen, and by FEMA 273 (as proposed by H. Krawinkler) for predicting the postelastic response of buildings subject to seismic excitation. All three methods have the potential to contribute effectively to the problem of improving the practical prediction of seismic response of structures. Applications include preliminary design, routine (code) use, calibration of codes, and specific structure assessment. These methods appear different because their authors did not share the same objectives or information bases. The methods by Cornell and Wen are decisively prediction-oriented in explicitly probabilistic frameworks. The approach suggested by Krawinkler has instead the goal of understanding in some average sense the seismic response of structures at various performance levels. This last method has been adopted, however, for prediction purposes by the FEMA 273 Guidelines for rehabilitation of existing buildings. Despite the differences, the work proposed by these researchers is profitably brought under the same perspective here.