Calibration of a Simplified Model for Dynamic Response Assessment of Infilled RC Buildings

The prediction of the engineering demand parameters, such as interstorey drifts and peak floor accelerations due to a seismic event, represents a necessary stage for the assessment of direct economic losses in existing buildings. Generally, performing non-linear dynamic analyses on highly refined finite element models would be the most effective method for the estimation of such parameters. However, these procedures require a level of detail that is not employable on the large scale because of the required computational effort. This work presents a simplified model, that can be adopted for the rapid evaluation of the engineering demand parameters in infilled frames subject to seismic actions. The proposed simplified model consists of a system of masses concentrated at each storey, connected by means of non-linear elements that properly describe the interstorey behavior. The procedure adopted to construct the simplified model of a multi-span multi-storey frame is described in detail. The interstorey non-linear envelope is defined by properly assembling the envelope of individual members under the simplifying hypothesis that rotation at the end of the columns are restrained. The hysteretic behavior of non-linear elements is calibrated for each storey based on the response of a 3D building modeled adopting a refined finite element model, and using the results of non-linear cyclic pushover analysis. The calibration is performed by adopting a multi-objective optimization procedure that involves the use of a Genetic Algorithm. The results of the proposed model are compared with those obtained by finite element analysis of a reference building for different intensities. The proposed model can be easily applied to carry out simplified numerical analyses useful for the assessment of direct economic losses at the large scale.