Inelastic condensed dynamic models for estimating seismic demands for buildings

Computationally-efficient simulations of structural responses, such as displacements and inter-story drift ratios, are central to performance-based earthquake engineering. Calculating these responses involves potentially time-consuming response history analysis of inelastic structural behavior. To overcome this burden, this paper introduces a new inelastic model condensation (IMC) procedure. The method presented here is non-iterative and uses the modal properties of the full model (in the elastic range) to condense the structural model such that the condensed elastic model preserves the modal properties of the full model at certain modes specified by the analyst. Then, by replacing the inter-story elastic forces with hysteretic forces, the inelastic behavior of the full finite element model is incorporated into the condensed model. The parameters of these hysteretic forces are easily tuned, in order to fit the inelastic behavior of the condensed structure to that of the full model under a variety of simple loading scenarios. The fidelity of structural models condensed in this way is demonstrated via simulation for different ground motion intensities on three different building structures with various heights. The simplicity, accuracy, and efficiency of this approach could significantly alleviate the computational burden of performance-based earthquake engineering.