EUROCODE 8-Part 2, Bridges: time history presentation of seismic action for base isolated bridges

The purpose of the investigations presented herein has been to show a developed and verified method for presentation of seismic action by a time history. These investigations are related to Eurocode 8, Part 2, Bridges, and have involved the use of recorded accelerogrammes obtained from occurred earthquakes. The method introduces optimization by which, for a period equal to the natural period of vibration of a structure, the ratio between the square root of the sum of squares of the spectra computed from both horizontal components of a single record—SRSS and the code spectrum is computed. While performing this task, pairs of horizontal components for which this ratio is equal or greater than 1.0 (up to a tolerance value) are selected for nonlinear dynamic analysis, provided that the scaling factor is limited. Verification of the method is given for a base isolated bridge on E-75 motorway, with a natural period of 1.4 s. Also, some important recommendations and discussions related to the presentation of the code spectrum by a time history are given.