A REVIEW OF THE FRAME ANALYSIS OF PILE FOUNDATIONS AT LIQUEFIABLE SITES

In the JRA Specifications for Highway Bridges a static analysis method using rigid frame and subgrade reaction models is recommended as a verification procedure of pile foundations for the level 2 (higher) level seismic motions. This paper investigates reasonable simple methods for analyzing dynamic behaviors of pile foundations embedded into liquefiable soils, with emphasis on evaluation of input conditions assumed in the verification procedure. First, it presents the results of effective-stress analyses for overall soil-pile-structure systems, and then compares the analytical results with the results of parametric static rigid frame analyses considering ground deformations. From this investigation it is concluded that dynamic behaviors of pile foundations at liquefiable sites can be simply analyzed, by assuming that ground displacements from the effective-stress response analysis of soil layers and structural inertia forces from the acceleration spectra analysis are taken as input conditions in the static rigid frame analysis.