HOW TO CHOOSE EARTHQUAKE RECORDINGS FOR NON-LINEAR SEISMIC ANALYSIS OF STRUCTURES

The research project presented here dealt with an important aspect of seismic structural response that is still not well understood. Its objective was to develop criteria to choose suitable earthquake recordings to be used in non-linear dynamic analyses for seismic design, evaluation and upgrade of ductile structures. The methodology adopted consists of systematic investigations of the non-linear response of single-degree-of-freedom (SDOF)-systems subjected to different types of earthquake recordings. The structural behavior is described by six different recognised hysteretic models. A database of 164 recorded time-histories was built based on the European Strong Motion Database. Different earthquake characteristics are investigated (effective peak ground acceleration, spectral acceleration, slope of response spectra, spectral intensity, etc.). The ductility demand of the SDOF systems is then correlated with the different earthquake characteristics. According to the conclusions of others, spectral intensity defined by Nau and Hall gives a good prediction of the seismic impact on structures. A modified spectral intensity is proposed here in order to improve its prediction. This modification takes into account the structural natural frequency and the design ductility. Corresponding recommendations are formulated for structural engineers that are believed to increase the reliability of non-linear seismic analysis. In addition, the impact of fling on structural behavior is addressed, too. 20 recordings from the Chi-Chi Taiwan earthquake containing fling were applied to the SDOF systems. The related ductility demand is compared with the one of the same recordings after extraction of the fling. The preliminary results, in general, show relatively small differences. Surprisingly, if differences occur, larger ductility demands result for the recordings without fling