Abstract
Effect of energy dissipation from foundation to soils on modal damping ratio of bridge piers supported by rigid foundation was presented. An analytical model for the soilfoundation system based on an elastic wave propagation theory was used to consider the energy dissipated by radiating wave. A modal damping ratio equivalent to that caused by radiational damping was evaluated from steady-state response curve excited by harmonic motion. Numerical analyses were made for 540 cases of road bridge pier foundation. From statistical analysis on these results, the effect of radiational damping on the modal damping ratio was clarified. Simplified and practical formulae of the equivalent modal damping ratio in terms of natural period of the pier and rigid foundation systems were proposed.
