해상 풍력 발전 Jacket 지지구조물의 X-joint weld toe 응력 집중 현상 연구

Abstract

Due to less turbulence and no land limitation, the offshore wind energy gets more attention than the onshore. Jacket structure is regarded as a suitable solution for the water depth ranging from 30 to 80 meters. Nowadays, most jacket structures for offshore wind turbines have tubular X-joints. The crack mostly initiate at the intersection of the X-joints due to high level stress by the discontinuity. Therefore, weld toe stress concentration of joint for jacket support structures affects their fatigue life. The Purpose of this study is to investigate the relation of the weld toe stress between the stress concentration factor fomulae and the extrapolation with the finite element method. The hot spot stress of the weld toe can be calculated by above two methods. The extrapolation with the FEM shows more accurate results than the former due to applying many different types of loads while it needs so much time and expense. Thus, investigation of the relation between two methods is required to calculate fatigue stress of weld toe efficiently. This study carried out by using the model based on the upwind reference jacket in the OC4 project with water depth of 50m. The wind turbine system of 5MW NREL reference model is used for load analysis under power production condition of IEC 61400-3.