Buckling Behavior of Fiber-Reinforced Elastomeric Isolators under Elevated Temperatures

During the course of their design life, base isolators may be subjected to elevated temperatures for a variety of reasons, including fire hazards. In such scenarios of elevated temperatures, the vertical load-carrying capacity of base isolators could deteriorate. Therefore, assessment of the stability of fiber-reinforced elastomeric isolators (FREIs) under the vertical loads from the superstructure while under elevated temperatures is important. In this study, the buckling behavior of FREIs is investigated under ambient and elevated temperatures. Available closed-form expressions to predict the buckling load of FREIs at ambient temperatures are extended for applications under elevated temperatures. Under elevated temperatures, the buckling load is derived by considering the thermal expansion of the FREIs and the material degradation of the elastomers with the rise in temperature. Further, nonlinear finite-element analyses are conducted to numerically evaluate the buckling behavior of a wide range of FREIs with various inherent properties. Modified Riks analysis is utilized to estimate the nonlinear buckling behavior of the FREIs. Transient heat transfer analysis within the FREIs is conducted to observe the buckling loads of the FREIs after various time instances, and the steady-state uniform elevated temperature in the FREI is found to be the worst-case condition under the considered thermal boundary conditions. Herein, only the thermal scenarios of uniform elevated temperatures at all the faces of a single FREI are explored. It is observed that the closed-form expressions for buckling load under elevated temperatures could effectively predict the buckling loads of the FREIs, providing slightly conservative values for most cases. Interestingly, the results show that the FREIs with low aspect ratios (such as 1.20) demonstrate the maximum reduction in their vertical load-carrying capacity with the rise in temperature.