Numerical investigation of dynamic behavior of composite foundation composed of soilbags and piles by 3D elastoplastic FEM

Abstract

In this paper, a new composite foundation composed of piles and soilbags is proposed, and its mechanical behavior is investigated systematically with numerical analyses based on sophisticated models for both soils and structures. The foundation is characterized by the laying of soilbags between the pile heads and the footing on which the superstructure stands. The expected effects of the foundation are to cut off the fixed junction between the piles and the footing in order to reduce the bending moment of the piles and decrease the response acceleration of the structure. In this study, the seismic response of the proposed composite foundation is investigated numerically by a 3D elastoplastic FEM analysis, and the superiority of the proposed composite foundation over the conventional pile foundation is discussed in detail. From the analysis, it is found that both the bending moment and the response acceleration of the pier are suppressed because of the elongation of the natural period of the foundation and the increase in the hysteresis damping of the soilbags. In addition to the above-mentioned effect on the response acceleration, the bending moment of the piles is greatly reduced at the pile heads in the proposed composite foundation due to the effect of the stress dispersion of the soilbags.

Keywords

• Soilbag
• Pile
• Elastoplastic FEM
• Composite foundation
• Hysteresis damping
• Stress dispersion