Design Method of Seismically Isolated Structures Based on Generalized Response Spectrum Analysis

Seismic isolation is widely used in seismic areas of the world for their functions of securing both of human life and the property. While simple design methods for simple structures have been proposed by many researchers, these methods are generally limited to specific seismically isolated structural systems. Particularly in Japan, the number of challenging structural systems (e.g. a base isolation with tall buildings, mid-story isolation or roof isolation systems having substructures with dampers) where these methods cannot be applied are recently increasing. In practice, many projects require an iterative approach with time-consuming NLRHA to determine the isolation design. Therefore, this paper presents a design method for highly indeterminate seismically isolated structures utilizing generalized response spectrum analysis, which has been extended to simulate both of an elasto-plastic damper with isolator and a nonlinear oil damper. In section 2, the extension of generalized response spectrum analysis (GRSA) is described in detail. The design method of seismically isolated structures based on GRSA is proposed. In section 3, the fundamental accuracy of GRSA is verified using a series of numerical simulation of single-story isolated structure models. Moreover, the range in application of the parameter formulations of complex stiffness for complex multi shear spring element simulating elastoplastic dampers with isolator is discussed. In section 4, the design example of a tall building with base isolation based on GRSA is demonstrated. In section 5, the design example of a 9-story mid-story isolation building having substructure with dampers based on GRSA is demonstrated. In section 6, the design example of an isolated lattice dome building having substructure with dampers based on GRSA is demonstrated.