ABSTRACT
Strong earthquakes impart substantial amounts of energy into structures and may cause the structures to deform excessively or even collapse. In order for structures to survive, they must have the capability to dissipate this input energy through either their inherent damping mechanism or inelastic deformation. This issue of energy dissipation becomes even more acute for bridge structures because most bridges, especially long-span bridges, possess very low inherent damping, usually less than 5% of critical. When these structures are subjected to strong earthquake motions, excessive deformations can occur by relying on only inherent damping and inelastic deformation. For bridges designed mainly for gravity and service loads, excessive deformation leads to severe damage or even collapse. In the instances of major bridge crossings, as was the case of the San Francisco-Oakland
Rihui Zhang
Bay Bridge during the 1989 Loma Prieta earthquake, even noncollapsing structural damage may cause very costly disruption to traffic on major transportation arteries and is simply unacceptable.
