Study On Stress Concentration Factors For Five-planar Y-joints Of Offshore Wind Turbine Structure

Offshore wind power is a kind of renewable clean energy.According to statistics,the wind energy resources which can be developed and utilized in China is about 1 billion kilowatts.But the offshore wind power development of our country is still in its initial stage at present.The factors including controlling the cost,improving the service life decide the prospects of the wind energy development.Support structure of offshore wind turbine are comprised of welded steel structure,which subjected to environmental loadings from wind,wave and current.Cracks could initiate and develop in high stress concentration zone under the dynamic loadings,which result in the fatigue damage.Tubular joint as an important connecting component of support structure of offshore wind turbine has an obvious and complex phenomenon of stress concentration.The expressions of stress concentration factors(SCF)are suitable for the simple joints in codes.Thus,it is of necessity to study the SCFs for multi-planar joints.In this thesis,the five-planar tubular Y-joint of offshore wind turbine support structure is studied.Using ANSYS,analysis of the SCF of the tubular joints is carried out.The contents of this research include:(1)Using twenty-nodes solid element in ANSYS,the sophisticated finite element models for the five-planar tubular Y-joint are established.(2)Referred to the test of a tubular K-joint in a reference,the FE model of the K-joint is established.Compared with the experimental results,the method of FE modelling of tubular joint with weld seam is validated.(3)Based the geometric parameters from the practical projects,the calculation cases are determined.By FE analysis,the SCF distribution along weld seam,SCF extreme value,and the effect of interaction among multi-planar joints on SCF are studied.The linear superposition method is validated to determine of SCF of five-planar tubular Y-joint under complex load combinations.Meanwhile,sensitivity analysis of geometries parameters is carried out.(4)Corresponding to the above cases,the FE models of tubular joints with three stiffened rings are establish and computed.The SCF distribution along weld seam,SCF extreme value,and sensitivity analysis of geometries parameters are performed for the joints with stiffened rings are compared.