SEISMIC PERFORMANCE BASED DESIGN PHILOSOPHY

The current seismic design practice in the most countries of the world such as Iran are based on the force-based design philosophy, with a partial incorporation of the capacity design concepts. These current codes have the following characteristics:* The basic objective is life safety for the design level ground shaking * They attempt to increase the detailing and/or seismic design force requirements, but the resulting level of enhanced performance is not explicitly defined. * The design of the seismic load resisting system is based on a pseudo seismic load, which is reduced from the ductility factor R value The R value is used to reduce the design lateral load on the entire building. There is only one R value for the entire building. Thus, the same reduction is applied to beams, columns, braces, foundations, bolts, welds, diaphragms, etc., independent of the element's ductility. Performance based seismic engineering is the modern approach to earthquake resistant design rather than being based on prescriptive code formulations. Performance based design is an attempt to predict buildings with predictable seismic performance. Therefore, performance objectives such as life safety , collapse prevention, or immediate occupancy are used to define the state of the building following adesign earthquake. In one sense, performance based seismic design is limit-states design extended to cover the complex range of issues faced by earthquake engineers. This workshop provides a basic understanding of the promises and limitations of performance based seismic engineering.