Model Tests Investigation And Design Method Of The Behavior Of The Pile Group Under Eccentrically Lateral Loading

With the rapid development of the ocean economy in our country, the construction scale of offshore structures gets larger and larger in the recent years, such as bridge bents, platforms and wind turbines. The foundations for offshore structures are subjected to lateral loading of considerable magnitude, such as wind and wave action, or ship impacts. Significantly eccentric lateral loads can be transferred to the foundation piles by virtue of eccentric lateral loading, giving rise to complicated response of the structure. But the response of pile groups under eccentric lateral loads is rarely reported, and investigations are urgently needed.Large-scale model tests and theoretic study were conducted to investigate the response of lateral loaded pile groups with different eccentricities. The model tests were carried out in saturated silt, including two 3 x 3 pile groups tests at different eccentricities (e=6D and e= 1 ID), and single pile tests under lateral loading and torsionally loading, respectively. GROUP, a pile group analysis program, was used to analysis the results of model tests.The results of model tests indicated that the coupling effect existed between the lateral load and torsional load. The applied torque significantly decreased the lateral resistance of the pile group, and the lateral load slightly increased the torsional resistance of the pile group. It was found that the distribution of the shear forces, torsional resistances, and the bending moments of the individual piles are significantly different with the pile location, and the difference became larger as the eccentricity increased. Both torsional and lateral resistances of the individual piles contributed to resist the applied torque, and the contribution of lateral resistances of the individual piles to the applied torque significantly increased with applied load. And combined with the calculation of GROUP, new p-multipliers of the pile group at different eccentricities (e = 6D and e=11D) are proposed here. The enhancement factor, ratio of the average torsional stiffness of the group piles to the stiffness of single pile in the single-pile experiment, is also given here. Based on the analysis above, the calculation method of eccentrically laterally loaded pile groups is also proposed.