The choice of the control displacement in pushover analysis of bridges: a case study

Seismic assessment of existing bridges requires consideration of the structural inelastic behaviour. Non-linear static methods (i.e., pushover) have become a standard tool in civil engineering practice for the analysis of various structural typologies, including bridges, due to simplicity compared to non-linear dynamic analysis. Nevertheless, the extensions of the applicability of pushover methods to bridges seem to show peculiar relevant questions. This work presents a case study of non-linear static analyses of an existing reinforced concrete (RC) highway beam bridge. Among the numerous proposals available, traditional pushover analysis has been chosen as the analysis method. The simply supported beams bridge has a total length of around 706 m, with 16 spans of 43 m each; the simple deck is made of reinforced concrete beams pinned over the multiple stem piers, whose height varies regularly from 11 m to 5.5 m. Non-linear behaviour of bearing devices, soil-abutment interaction system and expansion joints (closure) have been accounted for. The analysis has been performed in both longitudinal and transverse directions, subjecting the structure to the following load distributions: (i) constant along the deck and (ii) one that considers the contribution of the modes according to the response spectrum analysis. The case study seems to confirm the importance of the reference point selection in the bridge seismic assessment via pushover method. The pushover has been compared with the results of dynamic non-linear analysis.