Free Vibration of Skewed Bridges

Abstract

Determination of period of vibration is an essential step in understanding the seismic behavior of bridges. In this paper, an analytical solution for the free vibration problem of slab-beam, single-span skewed bridges is derived. It is assumed that the deck acts as a rigid diaphragm, but the effects of cross-frame and elastomeric bearing stiffnesses at the ends of the span are included. Based on the ratio of elastomer to cross-frame stiffness, exact equations for determination of translational and torsional periods of vibration and their corresponding mode shapes are derived. In addition, correlation factors for estimating the translational periods of a skewed bridge from the periods of a straight bridge with the same characteristics are also given. The derived equations are compared with finite element analysis, and it is shown that they are in excellent agreement.