Effect of Superstructure Deformation Capacity on the Collapse Performance of Seismically Isolated Buildings

Earlier studies found that acceptable probabilities of collapse for seismically isolated buildings could be achieved by an appropriate combination of strength in the superstructure, isolator displacement capacity, and stiffening behavior. The results were based on the study of braced and moment frames in which the story drift ratio at collapse was predetermined on the basis of the design details of the frames (special or ordinary in steel). This paper further investigates the effects the value of the peak story drift limit at which collapse occurs, in combination with the displacement capacity of the isolation system, have on the collapse probability of these structures. The results provide information on the utilization of superstructures with fewer ductile design details in seismically isolated buildings. This is important because buildings with fewer ductile design details have lower construction costs and can be built more quickly.