Implications of importance factor on seismic design from 2000 SAC-FEMA perspective

The seismic design of buildings uses global ductility factor and occupancy importance factor (IF) as two major fixed parameters in defining the safety of the structure. The study of performance variation of the structure with global ductility factor is available but there is hardly any study that provides information regarding the increase in the level of safety achieved by increasing the IF values. Being a building categorical dependent parameter, IF is used by the international seismic design codes for increasing the design loads of the structure. The change in the level of safety achieved through the variation in the value of the IFs for reinforced concrete (RC)–framed buildings will perhaps be an important and useful representation of the stakeholders for the approximate damage cost estimation. This article performs the structural safety assessment against seismic load using a standard structural reliability method with second-order hazard approximation to evaluate the effect of the IF on the level of safety and the cost associated with the building. Results show that an overall reduction of 50%–60% in the damage index of the selected buildings can be achieved by increasing the IF from a value of 1.0–2.0 with a consequent increase in the cost of the building.