Modeling of soil-pile interaction for bridge foundations under seismic loading

Traditionally, Tennessee has designed bridges for expected traffic loading, and with few exceptions has not assessed the vulnerability of its bridge structures to seismic loading. However, in recent years consideration of seismic loading has become a part of their design process,with particular attention given to bridges in westTennessee.To support this design effort, research related to the response and behavior of bridge foundations under seismic loading is presented.The purpose of this research is to assist the Tennessee Department of Transportation in their analysis of bridges subjected to seismic loading.Specifically, modeling of pile supported bridges is addressed. A survey of the current "state-of-practice" in the areas of testing and development of methods to model bridge foundations is presented.Two analytical techniques are presented to model a pile supported bridge foundation system. A model of a two-span continuous structure is analyzed with the foundation system modeled with linear elastic springs. These spring coefficients are varied to study the effect of foundation stiffness on dynamic response of the substructure. A field testing program consisting of free and forced vibration testing is suggested and expected results from such testing are integrated with a simplified single degree-of-freedom and modal analysis of the test results.