ANALYSIS MODEL OF POUNDING BETWEEN ADJACENT BRIDGE GIRDERS DURING EARTHQUAKES BASED ON COLLINEAR IMPACT BETWEEN RODS

Pounding will occur between adjacent bridge girders if the maximum relative displacement is larger than the expansion joint gap during earthquakes. Pounding may result in structural damage or even lead to collapse of superstructures. The study is aimed at establishing a reasonable analysis model of pounding between adjacent bridge girders during earthquakes. Bridge girders are modeled as elastic rods with the same cross section and collinear impact between them is expressed by a impact spring. Effects of parameters including impact spring stiffness ratio α, length ratio l₂/l₁ between adjacent bridge girders and damping ratio ξ on impact force, impact duration and energy loss are discussed on the basis of analytical solution and numerical simulation. In determining a suitable value of impact spring stiffness, the strong-motion data recorded on a concrete bridge instrumented by the California Strong Motion Instrumentation Program(CSMIP)are used. The impact spring stiffness is found to be about 0.5 times that of axial stiffness of the shorter bridge girder.