Behaviour of Composite Bearings Used in Bridge Isolation

摘要: Vibrations produced by earthquakes are extremely dangerous; they can harm essentially the build environment, affecting normal community’s life. Bridges are especially exposed, because they present distinct properties of the structural response from that of buildings: bridges are long in one direction and are typically more flexible in the vertical direction compared to buildings and bridges are supported by flexible piers while buildings often have relatively rigid foundations. One of the most relevant tools for protecting bridges from the damaging effects of earthquakes is the use of isolation systems. A good seismic isolation is achieved by inserting flexible bearings into the bridge, between the sub-and superstructure. It shifts the vibration period of the system, permit relatively large displacements and provide good energy dissipation. Seismic vibration isolators begun to be used after the middle of last century, but the structural behaviour of bridges incorporating this systems is not well understood, in part due to the lack of adequate models that can describe the complex behaviour of the isolators. First, the paper presents theoretical models for the whole dynamically loaded structure, together with numerical simulations. Initial conditions for the design of isolation systems are defined. Next, theoretical models for two types of bearings (rubber-steel bearings with and without lead core) are developed, taking in consideration the needs and limitations above determined. Finally, considerations regarding the opportunity of using composite material bearing are presented.