Seismic behaviour of structures under bidirectional ground motion: Does the angle of incidence have any influence?

Inelastic seismic behaviour of structures is needed to be predicted as accurately as possible. As during the seismic design, structures are allowed to undergo a stipulated amount of inelastic deformation in the dual design phi-losophy and its further extension of performance-based design. To obtain reasonably accurate behaviour in post-elastic ranges has manifold issues to be addressed together. The simultaneous effect of bidirectional ground motion is one of the major factors that need to be considered, and many studies also did the same. However, hardly any of them did consider the interaction between the deformations along two principal orthogonal di-rections on the yield criteria, post-elastic range excursion and the criteria of unloading. The present study makes an attempt to address these issues. Further, a few more studies mentioned that the angle of incidence of such orthogonal components of ground motion might influence the response of the structure. Hence, along with incorporating the effect of bidirectional interaction in the post elastic range, the issue of incidence angle is also studied extensively to reach a conclusive end. The detailed results presented in the study not only help to develop the physical insight but also maybe help in fine-tuning the design provisions.