Implications of adopting different force reductions in seismic design of RC buildings

The implications of assigning different levels of force reductions by two seismic design codes on the relative safety margins of regular and irregular RC buildings are investigated in this study at various performance levels. Four moment-resisting frame structures are detailed according to two seismic design provisions; the Egyptian national design code in addition to the internationally recognised European design standard. The seismic demands of the buildings obtained from a large number of inelastic analyses are compared at the member and structure levels using detailed fibre-based simulation models. It is concluded that, in regions of medium seismicity, designing a building using more conservative force reduction factors has lower impacts on improving its seismic performance compared with the key role played by ductility and capacity design. The comparative study sheds light on the performance of structures when designed to different seismic forces but with adequate ductility, which helps in realising the differences between design standards.