In this study, seismic analysis of soil-foundation interaction under a bridge pier are studied with different earthquake excitations. In 2016, August 25, a magnitude of 6.8 happened near Bagan region. Pakokku Bridge, the longest of the bridges over the Irrawaddy, is situated on 37.8 miles from the epicentre of 2016 Chauk earthquake. That is why the safety performance of long-span Bridge (Pakokku Bridge) especially for the safety of the foundation system subjected to soil-foundation interaction

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... s necessary to investigate for unexpected future seismic excitation. Firstly super structural loadings on the pile cap are estimated by using STAAD PRO V8i. And then, p-y curves are determined by Reese (1974) method for the static and National Cooperative Highway Research Program (NCHRP) for dynamic conditions. Based on the development of p-y curves, theoretical ultimate soil resistance pcr and pcd due to wedge and flow failure are determined to produce critical depth xcr. After that, finite element software ABAQUS is used for the analysis of soil-foundation interaction under a bridge pier in static condition. And then, the behaviour of soil foundation interaction under a bridge pier is carried out due to Chauk earthquake. In this study, the behaviour of soil-foundation interaction such as deflections and settlements are produced. According to the analysis results in static condition, it is found that the vertical and horizontal displacements at the pile tip are 2.28mm and 0.14mm respectively. In dynamic condition, the vertical and horizontal displacements at the pile tip are 3mm and 2.94mm are found at 0.12g. After that, maximum ground acceleration of 0.5g is 14.5mm and 2.94mm in horizontal and vertical displacement of pile tip. Maximum shear stress and strain are found out the base of the pile cap. Finally it is found that the soil-foundation interaction under a bridge pier during earthquake motions presented in this study is reliable and reasonable with the limitation of AASHTO Standard Specifications for Highway Bridges.