Seismic Design of Bridges for Prevention of Girder Pounding

Abstract

In design of conventional bridges the gap between bridge spans is usually only a few centimetres. For such an expansion joint poundings between adjacent bridge girders during strong earthquake shaking are usually unavoidable. Pounding often causes damages to girders. In extreme situations it may push one of the bridge decks off the support. In this work a new design philosophy using a modular expansion joint (MEJ) is introduced. So far MEJs have been used mainly to cope with large thermal expansion and contraction of long bridges. For proper design of bridges to avoid the consequence of poundings under strong earthquakes not only a minimum total gap but also the maximum opening movement of the joint are essential. In this study the simultaneous effect of varying vibration properties of adjacent bridge spans, spatially varying ground excitations and soil-structure interaction on the total closing and opening movements of a MEJ, required to eliminate possible pounding and to ensure the join in perfect working order, is estimated, and the main influence factors are discussed.