DYNAMIC RESPONSE ANALYSIS OF INELASTIC BRIDGE STRUCTURES

Abstract

Bridges are essential links for transportation lifeline system. They should remain safe during and after devastating earthquakes. From earthquake point of view, bearing is a very critical part of the bridge, because the inertia force from deck is transferred to sub structure through bearings. Conventional bearings ( Rocker and Roller ) transfer most of the inertia forces-from deck to the pier. So at higher ground acceleration the structure goes in the inelastic range and thus plastic deformation occurs. Base isolation is a strategy for decoupling the substructure from inertia forces •in the deck by providing flexibility between deck and pier. A base isolation system must possess flexibility and energy absorption qualities. A lead-rubber bearing offers a good means of providing base isolation because of cheapness, high vertical stiffness, horizontal flexibility and energy absorption. At low level of ground acceleration, the lead-rubber bearing behaves as conventional bearing but at higher levels it goes in inelastic range and provides. isolation. However the rest of the structure remains elastic.