Developing a New Weighted Relative Performance Index to Evaluate Base Isolation Systems in the Seismic Behavior of Structures

One of the methods to prevent the direct transmission of earthquake forces from the ground to a structure is seismic isolation. The main goal of seismic isolation is to reduce the amount of acceleration and forces transferred to the structure during an earthquake. This goal is achieved by installing the structure on separating layers that possess high horizontal flexibility. In this way, when the ground beneath the structure vibrates strongly during an earthquake, minimal movement is induced in the structure. In this research, a new index has been introduced to compare the performance of base isolation systems, which can lead to the design of base isolation systems with improved performance for the structure. By utilizing the proposed index, known as the Weighted Relative Performance Index (WRPI), the performance of both the structure and the base isolation system can be evaluated. This evaluation considers the amount of strain energy absorbed in the structure and the isolator, as well as the maximum acceleration value and the displacement created in both the structure and the isolator. To evaluate the effectiveness of the proposed index and compare it to previous indices, a 6-story steel moment frame with and without base isolation system was studied. Overall, the WRPI index demonstrates better efficiency and performance than previously used indices, particularly in structures sensitive to acceleration and inter-story drifts.