Abstract
A pier foundation has plenty of advantages as the foundation form for large onshore wind turbines in the terrain of the Gobi desert and collapsible loess areas. The ultimate load bearing capacity design, as an important part in the design phase of this foundation form, is not sufficiently in terms of design theory and the checking method, especially for application in collapsible loess areas. In this paper, numerical limit analysis has been employed to analyze the load bearing capacity for the scheme of selection of a pier foundation of a 100 MW wind farm in certain collapsible loess geology in Ningxia. The results were then compared with the empirical formulas, the limit equilibrium solutions and the finite element solutions to verify the accuracy of the results. It has been demonstrated that under the ultimate engineering load, the pier foundation can meet the stability requirement. In the ultimate state, whether the surrounding soil of the foundation falls in plasticity is associated with the ratio of the depth to the diameter of the foundation. The numerical limit analysis method can automatically determine the failure surface.
Highlights
IntroductionDue to advantages like rich resources, a good economic effect and low pollution, wind power has gained extensive attention worldwide
Due to advantages like rich resources, a good economic effect and low pollution, wind power has gained extensive attention worldwide.According to the forces acting on it, the conventional foundation of a wind turbine includes a gravity type foundation, a pier foundation and a pile foundation
Since the analysis mainly considered the interaction between the soil and the structure rather than the bending of the steel structure itself, the foundation was assumed to be rigid, that is, 1) a single structural element is rigid without internal strain; 2) the adjacent structural elements share the same angle of rotation and displacement at the same node coordinate without considering a plastic hinge
Summary
Due to advantages like rich resources, a good economic effect and low pollution, wind power has gained extensive attention worldwide. Based upon the conventional limit analysis theorem, the numerical limit analysis is a numerical method that utilizes finite element discretization technology to discretize the soil mass and the structure, it establishes the kinematically admissible velocity field (upper limit) and the static admissible stress field (lower limit), and applies a planning algorithm to obtain the maximum (upper limit) and minimum (lower limit) ultimate load This method has the following advantages: (1) without assumption of the failure mode, it automatically acquires the failure mechanism, the plastic zone of the soil and the stress distribution through program optimization; (2) it has the capability of dealing with complex loads and complex geometric conditions with the finite element method, and has a strict theoretical basis for limit analysis; (3) it envelops the true results by analysis of the upper and lower limits and is capable of providing the error range. The work in this paper employed the plane strain numerical limit analysis
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