Seismically induced torsional amplification in limited ductile buildings

This article deals with the seismic demand on limited ductile buildings featuring plan asymmetry. When the yielding occurs in a structural wall positioned at the edge of the building remote from the centre of resistance (CR), the position of the CR would shift even further away from the wall, causing an additional, and momentarily, increase in torsion. The undesirable shift in the position of the CR is usually shortlived and would reverse as other walls in the building also surpass the yield limit. However, the limited ductile construction (typical of low to moderate seismicity regions) can be vulnerable. This additional amplification in torsion can only be captured by Incremental Dynamic Analyses (IDA), but not by elastic analyses nor by nonlinear analyses of high ductility demand. Thus, the phenomenon as described is not widely known in spite of torsion being a well researched topic. In this study, parametric studies employing IDA of limited ductile buildings of different structural configurations were undertaken to capture the trends and develop recommendations for guiding structural design.