Behavior of a Structured Piled Beam–Slab Foundation for a Wind Turbine under Multidirectional Loads in Sand

Abstract

With wind farm development, a new type of foundation, the piled beam–slab foundation, was invented to support wind turbines on land. Although this foundation enables a lower-cost investment, its structure is complex. Wind turbine foundations are usually subject to combined vertical, horizontal, and moment loads. To investigate the coupled effects on the piled beam–slab foundation, scaled model tests were conducted. The results show that the presence of a vertical load increases the horizontal bearing capacity of the piled beam–slab foundation. The axial forces of the piles are mostly caused by the vertical load and moment acting on the foundation. The vertical load carried by the piles increases when the horizontal load acting on the foundation increases or the moment acting on the foundation decreases. Several equations are proposed to calculate the responses of the foundation under a combined load based on the responses of the foundation under a pure horizontal or moment load, which can be calculated by the traditional design method. Finite-element analysis on a prototype piled beam–slab foundation is performed to prove that the proposed equations are reasonable for actual foundations.