Fourway: Graphical Tool for Performance-Based Earthquake Engineering

Abstract

Fourway is a simple graphical tool for estimating the conditional dependence of decision variables involved in the seismic design process on the earthquake intensity. The tool was formulated for use with the Pacific Earthquake Engineering Research Center’s performance-based earthquake engineering framework. The tool simplifies the development of decision fragilities by exact determination of first moments and approximate determination of second central moments (variance) of the corresponding probability distributions, without the need for numerical integration of intermediate probabilistic models. For commonly assumed probability distributions of the interim variables, the Fourway method was compared to closed-form and numerical solutions, including measures for evaluating the variance approximations. It is shown that Fourway is a useful first-pass assessment tool for approximating the parameters of the decision variable distributions. Furthermore, Fourway is a tool for evaluating the effects of varying the interim model parameters on the final decision variable fragilities. Examples are provided for the case of a reinforced concrete highway overpass bridge in California.