The earthquake response of bridge pile foundations to liquefaction induced lateral spread displacement demands

The earthquake response of various types of pile foundations supporting a variety of bridge structures to liquefaction induced lateral spread displacement demands is analyzed using the concepts of pile ductility and pile pinning. The soil/pile model uses the stress-strain response of reinforced concrete and steel, incorporating both the axial and lateral loads for structural elements, and p-y curves to represent interface elements to assess the pile response during earthquake induced lateral spread displacement demands.;The analysis approach is incorporated in an improved design methodology using concepts documented in the FHWA "Recommended LRFD Guidelines for the Seismic Design of Highway Bridges (2003)".;Case studies of earthquake events, during which lateral spread displacement has caused damage to the bridge pile foundations are revisited to examine the response of these piles using the methodology developed in the research.;Design examples of several bridges supported by various types of pile foundations are also presented and the pile response in terms of plastic hinge development, pile ductility ratio and pile curvature response are studied. It is shown using the methodology developed in this research that given the subsurface conditions, the liquefaction and lateral spread potential and the structural details of the piles at a given bridge site, one can reasonably assess how close the pile is to acceptable ductility levels in plastic hinge zones. The method also provides a robust approach to screen for the acceptability of existing bridge pile foundations subject to lateral spread during present day design earthquakes.