A hysteretic model of lead-rubber bearings considering coupled thermal and mechanical behavior

Under the earthquake, the lead core of lead-rubber bearings (LRBs) occurs plastic deformation which causes the temperature rise of the lead core. This temperature rise results in the yield stress degradation of the lead core, which in turn reduces the heating rate of the lead core. Thus, there is a significant coupling effect between the thermal and mechanical behavior. In this study, a new hysteretic model of LRBs considering coupled thermal and mechanical behavior was proposed. Firstly, a full-scale LRB was experimentally investigated to display the thermal and mechanical behavior. The monitored temperature rise in the lead core reaches nearly 100 degrees C within 40 s. Subsequently, a finite element model for thermal analysis was developed and calibrated to obtain the bulk temperature of the lead core. A prediction formula for the bulk temperature of the lead core was modified based on discussions on previous assumptions. Finally, a new LRB model based on the Bouc-Wen model was proposed and it can capture the coupled thermal and mechanical behavior simultaneously. A case study of an isolated building was further performed to explore the differences between the new model and Bouc-Wen model. The temperature rise of the lead core reaches 139 degrees C under the rare earthquake. The differences of seismic responses indicate that compared to the new model, the traditional Bouc-Wen model may overestimate the bottom shear force of the superstructure but significantly underestimate the bearing deformation under ground motions with long durations.