Seismic strength demand for performance-based design

Despite the evolution of new seismic design concepts in recent years, it is perceivable that the base shear strength of the structure Will remain to be a fundamental design requirement for a long time to come. Traditionally, the seismic design strength is specified for the ultimate limit state in conjunction with the ductility requirement. This paper presents a direct damage-based approach for determining the seismic strength demand in terms of the so-called seismic strength reduction factor. The damage based strength requirement takes into account the cumulative damage due to energy dissipation, thus allowing for a particularly targeted state of the structural damage to be achieved through choosing an appropriate strength. The potential application of the damage based strength reduction factor in the evaluation of the seismic performance of a structural system is also discussed.