Response of Structures to Bidirectional Seismic Loading: Research Progress and Future Directions

Abstract

Rigorous assessment of structural response to seismic excitation poses challenges for researchers in their bid to account for the effects of (1) biaxial interaction; and (2) incidence angles of a ground motion relative to the structure. Keeping these two major issues in view, this paper presents a comprehensive review of the progress of research in the related areas. Studies since the 1970s clearly bring out the significance of interaction effect especially for stiff systems, and also the sensitivity of response to incidence angles. Further, a scrutiny of the design guidelines embodied in modern codes shows that, to account for the interaction effect, the codes primarily rely on the approximate combination rules evolved in the mid-1970s. In addition, both research findings and codified guidelines clearly reveal an apparent lack of consensus on the choice of appropriate incidence angle. With reference to bidirectional analysis, modern views of researchers on important aspects including quantification of damage and selection of ground motions are also discussed. Based on a critical review of the recent works and the codes, the paper recommends the use of an improved yet simple methodology for practical design. Directions for future research are also brought out.