Development of Earthquake Response Analysis for Whole Structural System Consisting of Ground, Piles and RC Structures

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The objective of this research is to investigate experimentally and analytically the response behavior of reinforced concrete piles under ground by the static and dynamic loading tests. The model specimens of RC piles were fixed to the bottom of the soil box assuming that a real RC pile is fixed at foundations, and the soil box was filled with sand. The pile head was subjected to reversed cyclic lateral loading as seismic load. The experimental parameters were the axial force on the pile head, including the alternative axial force due to rocking behavior of footing, and the connectivity condition at the pile head. The followings are derived conclusions from the experiment and analysis.1) With the increase of the axial force on the pile head, the larger hysteresis loops were observed in the response behavior, and the equivalent damping factor also became high. Additionally, a remarkable reduction of restoring force from its maximum value after yielding of the pile was observed in the case of high axial force.2) The maximum damaged length is independent on the axial load level of the pile and dependent only on the relative stiffness between pile and surrounding soil. The response behavior of the pile with the alternative axial load is determined by the behavior under the maximum and minimum constant axial load. Therefore, the most important point is to evaluate the possible range of axial load on the pile under seismic excitation.3) In order to evaluate the seismic behavior of the whole system of concrete structures including pile foundation, the response analysis method considering the separation of pile and soil was developed, based on 3-dimensional finite element analysis. Analytical results given by the developed method have good agreement with the experimental results.