Design And Research Of Grouted Connection In Offshore Wind Turbine Pile Foundation

Offshore wind power generation has becoming the focus in the field of new energy sources. Our country has a long coastline, rich in wind resources. However, our technology about offshore wind farm is still in infancy, so we lack the experience of design and construction. Structural design of wind turbine foundation is critical in construction of offshore wind farm, and the reliability of grouted connection is the necessary condition for ensuring the normal operation of offshore wind turbines. The load mechanism, finite element model and optimum structural design of grouted connection was studied in this paper use the ANSYS software, which provide scientific basis and reference for actual engineering.The main content of this paper includes:1. The load mechanism of grouted connection under axial force and bending moment was expounded, the corresponding formula about ultimate bearing capacity was put forward, and the main factors which affect carrying capacity of grouted connection were analyzed in detail. The analysis found that the carrying capacity of connection reduced quickly along with the increase of pipe diameter when without shear keys. Transfer of bending moment in connection mainly depends on compressive stress and friction force in contact surface.2. Numerical model and analytical method about grouted connection was introduced. Solid65and solid186elements were used to simulate grout and steel pipe respectively. And the contact174and target170elements were used for simulate the contact and slip between the surface of grout and steel pipe. The pile-soil interaction was simulated by p-y curve method.3. The influence of shear key about connection bearing in axial force and bending moment was researched. The method of simulating the grouted connection by ANSYS was effective and credible. When with shear keys, the axial load-bearing capacity rose notably, but the bending moment-bearing capacity changed little.4. The factor which influence mechanical behavior of grouted connection were optimized by ANSYS, mainly about the width, the height and space of shear key, grout thickness, the length of connection and so on. The best grout thickness varied with the different pipe diameters. When the length of connection was increased within a certain range, the bearing capacity of connection improved. When outside the range, the stability of the connection was likely to reduce. The study show that preferred ranges of L/DP is2.47～2.6and optimal height and width of shear key is0.02m and0.04m respectively. The optimal range of shear key space is0.3～0.5m. And height and space ratio h/s is preferably not more than0.04.5. The grouted connection structure of tripod foundation was designed, and its numerical model was analysed about the working condition under the practical load. The analysis results have indicated that the stress of steel pipe and grout were less than the yield stress of the material. There was no large area of crack in grout and the contact between grout and steel was good. So the structure was designed reasonably, and can be run safely.