Seismic Response Modification Factors for Buildings Featuring a Gravity Transfer System by Incremental Dynamic Analyses

Tall buildings featuring transfer structures are commonly constructed in lower seismicity regions. Discontinuities in load paths of structural systems in the building were found to compromise ductility of the building. In a force-based seismic design procedure, response modification (R) factor is uncertain to cater for the undesirable features. This article presents a methodical approach for evaluating the seismic performance of such buildings. Results of incremental dynamic analyses of case study buildings indicated a high R-factor, due to the inherent over-strength. A local amplification factor ((Formula presented.) is recommended to account for localised shear at structural walls above the transfer floor level.