Abstract
The prediction of the fundamental period and damping ratio of bridge pier-foundation system is of importance in seismic design of bridges. An analytical approach, based on linear simple superstructure of mass and height supported by a rigid embedded foundation with mass and mass moment of inertia having two degree of freedom with swaying and rocking motions, has been described. Although the model used in this study is simple, a concept of the equivalent complex spring and the equivalent input motions of soil-foundation and pier system has been presented. This concept makes it possible to assess the dynamic soil-structure interaction effect on seismic responses of bridges and to obtain a simple procedure of predicting the fundamental period and damping ratio of continuous girder bridge pier-foundation system, in conjunction with the virtual displacement method. The validity of the proposed method is examined by the dynamic analysis of multi-degree-of-freedom system.
