Seismic Retrofitting of Nonlinear Masonry Buildings With Newly‐Added Inerter‐Based Elevators via Stochastic Optimization

In China, many existing residential buildings requiring elevator installation are masonry structures with insufficient seismic performance. To address the dual demand for elevator installation and seismic retrofitting, this study investigates an inerter‐based elevator system for mitigating the seismic responses of nonlinear masonry structures. First, the selected macro‐model (BWBN model) is validated against masonry wall tests to reproduce the hysteretic behavior of both reinforced and unreinforced masonry structures. A statistics‐based method is then employed to derive the backbone curves and calibrate the corresponding BWBN parameters. Subsequently, an analog two‐degree‐of‐freedom system is developed to represent a masonry building equipped with an inerter‐based elevator. Nonstationary ground motions are simulated using the Clough‐Penzien model, and the system responses are obtained through stochastic equivalent linearization in state‐space form. Based on the equivalent linearized earthquake‐structure‐elevator system, an optimization procedure is established to determine the tuning frequency ratio and damping ratio by minimizing displacement, acceleration, and structural energy dissipation indices. Finally, stochastic response analysis and nonlinear time history analysis are conducted, demonstrating that the inerter‐based elevator with a mass ratio of can effectively mitigate the responses of nonlinear masonry structures. Under 200 recorded ground motions, the average displacement reduction ranges from approximately 13.8% to 19.1% for the reinforced masonry structure, depending on the adopted optimization objective.