Energy-based optimization of seismic isolation elements

Seismic isolation applications are increasing day by day in structures under earthquake hazards. The seismic isolation systems are modeled according to the building responses. Especially, the design of seismic isolation systems significantly affects the performance of the structure in critical buildings. In this study, lead core rubber seismic isolation parameters were optimized based on energy. Firstly, 200 different isolation systems were generated, with combinations of yield displacement, characteristic strength and isolation period. The generated seismic isolation systems were placed under the base floor of the sample superstructures and nonlinear time history analyses were performed. 3, 6 and 9 story moment-resisting frames are used as the superstructure models. The analyses were completed in SAP2000 using 7 different ground motions. The software integrated with SAP2000 was developed in Matlab in order to complete the large number of analyses. It has been revealed that the input energy can be used in the optimization of seismic isolation parameters by comparing the input energy with the structure responses. The seismic isolation parameters were optimized via Gray Wolf algorithm, where the input energy is used as the objective function. Additionally, a graphical method based on peak roof acceleration, isolation displacement and damping is proposed. The optimum isolation parameters calculated with the gray wolf algorithm and the graphical method were compared. The effects of the optimum isolation parameters derived from the two methodologies on structural responses have been examined in the superstructure. According to the obtained results, it was determined that energy-based methods gave satisfactory results in the optimization of seismic isolation parameters.