On the selection and scaling of ground motions for fragility analysis of structures
Abstract
The ground motion selection approach adopted for conducting fragility analysis of structures through nonlinear dynamic analysis can affect significantly the results obtained. The scaling method of the selected ground motions is a second factor that plays a major role as well. This work presents a methodology for the selection and scaling of ground motion time histories in fragility analysis that is based on a combination of existing studies with the introduction of novel steps that are recommended so as to achieve specific objectives. The proposed methodology uses the conditional mean spectra, which are defined for the specific site and the specific structure under examination and for different levels of seismic intensity. Sets of unscaled ground motions are selected to match the mean and variance of the spectral ordinates related to each seismic intensity and the fragility analysis is conducted by scaling each set within predefined limits. To demonstrate the procedure, an application example is presented where the suggested methodology is implemented for a hypothetical five-storey light-frame wood building situated at a specific site in Tuscany, Italy. The results of different fragility analyses are then compared with the results obtained by using the state-of-practice approach of a single set of ground motions scaled uniformly within the context of incremental dynamic analysis procedure.