Seismic Protection of Bridge Structures Using Shape Memory Alloy-Based Isolation Devices
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This study compares the performance of two smart isolation systems that utilize superelastic shape memory alloys (SMAs) for seismic protection of isolated bridges during strong earthquakes. The first isolation system is an SMA/rubber-based (SRB) isolation system and consists of a laminated rubber bearing that decouples the superstructure from the bridge piers and an SMA device that provides additional energy dissipation and re-centering capacity. The second isolation system, named as superelastic-friction base isolator (S-FBI), combines the superelastic SMAs with a flat steel-Teflon bearing rather than a laminated rubber bearing. Seismic energy equations of a bridge structure with SMA-based isolation systems are established by absolute and relative energy balance formulations. Nonlinear time history analyses are performed in order to assess the effectiveness of the isolation systems and compare their performance. The program RspMatch2005 is employed to generate spectrum compatible ground motions that are used in dynamic time history analyses of the isolated bridge. The results indicate that SRB isolation system produces higher seismic input energy, recoverable energy and base shears as compared to the S-FBI system. Also, it is shown that combining superelastic SMAs with a sliding bearing rather than rubber bearing significantly reduce the amount of the required SMA material. ASCE 2011.
