The Effect of Temperature on Unbonded Fiber-Reinforced Elastomeric Isolators

Abstract

During strong ground motions, structures equipped with base isolation systems have been shown to have their seismic demand significantly reduced, mitigating adverse effects such as damage and loss of life. More recently, the fiber-reinforced elastomeric isolator (FREI) has been investigated as a relatively new type of isolator for the base isolation of structures. Constructed from alternating layers of elastomer and carbon-fiber cloth, FREI can be produced in large pads that can be cut to any desired size and shape when required. In bridges, FREI can to be used in an unbonded application (U-FREI) by placing them between the bridge deck and the piers. Experimental and numerical investigations have shown U-FREI as a viable option for the isolation of bridges. However, experimental studies have been limited to room temperature testing. In North America, climates vary drastically across the continent. Northern climates, such as those existent in Canada, are capable of reaching extremely low temperatures. Thus, base isolated bridges in these regions require isolation systems that perform adequately at cold temperatures. The studies presented in this dissertation have been completed in order to investigate the effects that low temperatures have on U-FREI used in bridge structures. An experimental program was conducted that evaluated the behaviour of U-FREI. It was found that U-FREI performed adequately under lateral displacements expected during a seismic event, and provided acceptable response under vertical and rotational testing that is typical of normal bridge operation. Using these results, a numerical model for U-FREI was then updated to account for the effects of low temperature. The model was combined with a bridge model to evaluate the seismic response of a bridge structure isolated with U-FREI subjected to low temperatures. A substantial reduction in seismic demand was achieved, even under the most severe conditions tested.