Multidirectional pushover analysis for seismic assessment of irregular-in-plan bridges

• Assessment of irregular-in-plan bridges for various seismic input directions.
• Bridges with high curvature in plan exhibit variations up to 80% in its demands.
• Extension of traditional pushover procedures to account for this issue.
• Results validated by comparisons with nonlinear time-history analysis.

Nonlinear static procedures are becoming, evermore, popular tools for the seismic assessment of structures. Despite the considerable number of studies that have already addressed the improvement of pushover analysis, its limitations are still widely recognized by the scientific community, namely the inherent inability to accurately predict the behaviour of irregular structures. On the other hand, 3D structures exhibit a complex dynamic behaviour, in which the most critical direction of the ground motion input is many times not readily clear. In such cases, a multi-directional seismic analysis must be performed in order to capture the vulnerable earthquake demand direction of the structure. The study presented herein aims to assess the accuracy of pushover analysis in predicting the behaviour of irregular-in-plan RC curved bridges and to ascertain its effectiveness in multi-directional analysis. Particular attention is paid to the definition of the force distribution patterns, the direction of analysis and the determination of the target displacements, as well as to the modelling of the biaxial behaviour of the columns. The structural response of the bridges is assessed in terms of global and local behaviour. A comparative evaluation of the response of the bridges, estimated using nonlinear static (pushover) and dynamic analysis, illustrates the applicability of the pushover analysis technique as well as the influence of the directions of analysis, in the local and global structural demand of irregular-in-plan bridges.