Simplified linear static analysis for base-isolated buildings with friction pendulum systems

Several methods of analysis used for the design of base-isolated buildings are proposed in many structural specifications. According to different structural codes, limited conditions of equivalent linearization of the friction pendulum system (FPS) and application scopes of simplified linear static analysis (LSA) are introduced. LSA of a reinforced concrete frame building isolated by FPS is performed and compared with fast nonlinear time-history analysis (FNA) to evaluate the suitability of the simplified method. Based on a specific spectrum used in the new Italian code, seven spectrum-compatible earthquake ground motions are selected and scaled as seismic input. To perform both linear and nonlinear analyses systematically, a program is specially developed by MATLAB in combination with a commercial software. Base displacement, story shear force, and energy dissipation are selected as response indicators. The results reveal that, as a substitute for the exact nonlinear analysis method in the preliminary design of base-isolated buildings, the LSA method yields conservative estimates in base displacement and total input energy. However, because of the uniform acceleration profile assumed over the structural height, the story shear forces are significantly underestimated by LSA.