Evolutionary modal identification utilizing coupled shear–flexural response—implication for multistory buildings. Part I : Theory

A novel solution of dynamic response of multistory buildings is utilized in an evolutionary system identification algorithm for rapid and robust estimation of dynamic characteristics of instrumented building structures. The empirical characteristics obtained can be used for detection of possible seismic damage and for validating design assumptions with actual recorded structural response. Most structural identification procedures proposed to date only provide some estimates of the modal quantities from which inference to commencement of damage may not be trivial. In this proposed method, besides modal properties such as mode shapes and periods, an overall estimate of the participation of shear to flexural deformations in the lateral response of a building structure is examined. Therefore, any alteration in the mode of response between flexural and shear dominated can be monitored in a time‐varying fashion. The method is fully automated such that it can be used virtually without any delay in the aftermath of an urban earthquake. In a companion paper (Alimoradi and Naeim, 2006), the application of the proposed methodology and its capabilities are exhibited through numerous examples on building structures shaken by multiple earthquakes in their lives; many of them are amongst the most intensively studied instrumented building worldwide. The structural identification work presented here is a component of a comprehensive structural health‐monitoring system for instrumented building structures.