Seismic response analysis of base-isolated piers considering the mechanical properties and nonlinearity of HDR bearings

Abstract

High-Damping Rubber (HDR) bearings are a type of seismic isolation device in which natural rubber is mixed with carbon fillers to provide the rubber itself with high damping performance. These bearings reduce the transmission of seismic energy and enhance the seismic resistance of structures. Compared to other seismic isolation devices, HDR bearings have a simpler structure, are easier to install, and offer significant advantages in terms of maintenance and cost. However, the hysteretic behavior of HDR bearings is highly dependent on the maximum experienced strain and the hardening phenomenon, and their nonlinearity is pronounced. This study conducted experimental investigations into the actual behavior of HDR bearings based on characteristic validation test and evaluated their mechanical properties with respect to nonlinear hysteretic characteristics. From the experimental results, a model incorporating the maximum strain dependence and hardening phenomenon of HDR bearings was developed, and a new design model named the Double-Target model was proposed. The proposed hysteresis model accounts for the nonlinear hysteretic behavior of HDR bearings and can independently reproduce the responses in the positive and negative directions. Finally, the experimental results of the characteristic validation test were reproduced using the proposed hysteresis model, and seismic response analyses were conducted on the piers of an actual seismically isolated bridge to validate the model. The results confirmed that the proposed model accurately reproduces the independent hysteretic characteristics, including maximum experienced strain and hardening phenomena, as well as the characteristic validation test results. Additionally, the model enables seismic response analyses that consider the nonlinearity of HDR bearings with high precision.