Feifei Sun

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.

The loss factor is an important index for evaluating the damping capacity of non-Newtonian viscous polymers used in viscous damping walls (VDWs). The modulus ratio method (MRM) and the tangent of the loss angle (TLA) are commonly used to calculate this parameter. However, deviations may arise when using the MRM or TLA to evaluate the damping capacity of a polymer exhibiting the power-law effect. To resolve this problem, a simplified equation for the loss factor that considers the power-law effect (SELF-PL) was proposed based on its energy definition. Then, a series of dynamic sandwich-type shear (DSTS) tests was conducted to measure the loss factor of a polymer (Oppanol-polyisobutylene B12, abbreviated as PIB-B12) for VDWs. Based on the DSTS test data, the accuracy of the SELF-PL was verified, and the error of the MRM caused by the power-law effect was investigated. Finally, an error equation for the MRM was derived to quantify its applicable range. The strain rate amplitude is found to be the most influential factor affecting a power-law material. The loss factor of PIB-B12 decreases with increasing loading frequency, while it increases with increasing strain amplitude. The relative error of the MRM exhibits a roughly linear relationship with the power-law exponent.

The viscoelastic materials used in traditional viscous damping walls (VDWs) typically exhibit high storage moduli, which tend to exacerbate the structural response of adjacent components during earthquakes. Furthermore, existing studies are mostly limited to small-strain characterization and lack investigation into the macroscopic mechanical recovery characteristics of materials under mainshock-aftershock sequences. To overcome these limitations, this study introduces silicone oil (SO) as a softener to prepare a novel viscoelastic polymer blend (PIB-B12-SO). Utilizing a customized self-stabilization dynamic sandwich-type shear (S-DSTS) device, the macroscopic dynamic mechanical behavior of the blend was systematically evaluated, focusing on its low-cycle fatigue and rest-recovery characteristics. The results indicate that the addition of SO effectively reduces the storage modulus and significantly enhances the loss factor of the blend. Notably, at a mixing ratio of 1:4 (SO: PIB-B12), the loss factor increased by 65.6% compared to pure PIB-B12. Furthermore, the introduction of SO effectively suppresses the degradation of the loss modulus under cyclic loading and promotes viscous recovery during the rest periods. The silicone oil blend modification successfully optimizes the macroscopic viscoelastic properties of PIB-B12, significantly enhancing the energy dissipation stability of the material under low-cycle fatigue and interval loading.