Prediction of collapse - How realistic and practical is it, and what can we learn from it?

A methodology for computing the collapse capacity and collapse fragility curves for building structures is summarized. Specific results are presented for generic moment-resisting frames and wall structures. The emphasis of the discussion is on the implication of collapse capacity estimates for the collapse safety of frame and wall systems designed according to present code requirements. It is found that the probability of collapse at the MCE (Maximum Credible Earthquake) level is very different for frame structures than for wall structures, and that for frame structures, the probability of collapse increases strongly with the fundamental period and attains unacceptable values for long-period structures-unless a minimum base shear requirement is enforced that by far exceeds the base shear obtained from a uniform hazard design spectrum. The situation is very different for wall structures provided the predominant mode of deformation is flexure and not shear. Such wall structures exhibit a much smaller probability of collapse if the design is based on presently employed R-factors. The upshot is that the R-factor approach employed in present codes is inappropriate since it leads to designs with vastly different probabilities of collapse. Copyright (c) 2007 John Wiley & Sons, Ltd.