Numerical simulation on in-situ loading tests of composite foundation composed of soilbags, piles and footing

The authors have been developing a new composite foundation composed of soilbags, piles and footing, hereafter called as proposed composite foundation (PCF). PCF is characterized by laying soilbags between the pile heads and the footing. The expected effects of PCF are to reduce the bending moment of the piles and the response acceleration of the pier during earthquakes by cutting off the fixed connection between the piles and the footing. To apply PCF to practical use, it is necessary to confirm the validity of the numerical analysis model of PCF through comparison with the seismic behavior of the entire system of PCF confirmed by the previous in-situ loading tests. In this study, therefore, FEM analysis based on rational elastoplastic model was conducted to reproduce the in-situ loading tests, and the numerical model was verified by comparing the calculation results to the test results. Furthermore, since it is not always easy to conduct sophisticated elastoplastic FEM analysis in practical engineering, a simplified numerical method is proposed, and its applicability was examined by comparing to the test results and the elastoplastic FEM analysis results. The results showed that, although not all the results of the in-situ loading tests could be explained, the proposed simplified method could generally explain the test results and was useful for the practical engineering of the newly proposed PCF.