Nonlinear Response of RC Structures: Statistical Effects of Artificial Ground Motions

The selection of seismic inputs for nonlinear dynamic analysis is widely debated, mainly focusing on the advantages and disadvantages provided by the choice of natural, simulated or artificial records. However, most of the available technical codes do not provide always the same suggestions and well-defined procedures for the generation of artificial ground motions. Considering that the strategy of the generation of accelerograms makes some doubts raise about the possible effect on the structural response, the work aims to investigate on the differences of the structural behavior by using accelerograms nominally equivalent but different in terms of stationarity. This paper presents a comparative study of the structural responses of some reinforced concrete buildings under artificial accelerograms, characterized by a different shape depending on the strategy of generation. Initially, nonlinear response under three sets of accelerograms (50 stationary, 50 non-stationary evenly modulated and 50 fully non-stationary) equivalent in terms of pseudo acceleration spectrum is evaluated and compared. Then, the responses derived by the Incremental Dynamic Analysis (IDA) are compared and discussed by the statistical point of view. In the comparisons, different levels of irregularity for the reference reinforced concrete structure have been considered.