Seismic Performance Evaluation Procedure for Regular and Irregular Bridges

This paper describes a simplified procedure for the performance based seismic evaluation of bridges. It is based on the definition of a non-linear response curve for a reference SDOF system corresponding to the mode which contributes the greatest to the response of these structures. This curve is obtained through non-linear modal spectral analyses taking into account the contribution of higher modes of vibration. The procedure is based on one previously used for the evaluation of multi-storey buildings where, through a multi-mode pushover analysis, the response curve of a simplified reference system is obtained and from this the seismic performance of the structure is determined. In this paper, this procedure is modified by using for the definition of the response curve of the reference system, modal spectral analyses which take into consideration in an implicit way, the displacement reversal characteristic of the earthquake action, and the participation of higher modes of vibration of importance in the evaluation of bridges whose response is governed by one mode of vibration and the transient nature of earthquake action. To illustrate the application of the procedure, the results of two bridges, one regular and the other irregular, obtained with this methodology for earthquakes of various intensities given by the design spectrum of Eurocode 8, are compared with the mean of the corresponding results from inelastic step by step dynamic analyses using an ensemble of earthquake records congruent with the design spectrum of this code.JRC.G.5-European laboratory for structural assessmen