Lead specialist currently working with Vattenfall in offshore wind sector. Competencies in Structural design and technology development primarily within offshore wind. Expertise in finite element analysis, design optimization and advanced fatigue analyses.
Finite Element Analysis (FE) is widely used to perform fatigue calculations for geometric singularities at welded components. The analysis methodologies are described in design codes and recommended practices such as DNV, IIW, and Eurocodes. The focus of the present study is the application of hot spot stress methodology to a weld detail located at the cope hole in a pile sleeve connection of a jacket substructure. FE analysis is used to calculate the geometric stress where the influence factor (INF) technique has been implemented to calculate the hot spot stress at the weld location. Generally, a mid-surface shell model excluding the weld is used to model the welded components in FE analysis and a stress extrapolation method is applied to calculate the hot spot stress. The extrapolation method recommended for the plate edge has been found too conservative to be applied to the cope hole type welded details. A full solid model of the cope hole detail has been used for fatigue calculation and is used as benchmark to calibrate the weld modeling techniques using shell elements for the analysis. The results confirmed the weld stiffness has a significant influence on the hot spot stress calculation at the considered cope hole. Thus the weld geometry and stiffness shall be included into the finite element model for an accurate fatigue damage calculation of such details. The calibrated results showed that the mid surface shell model can still be used if the appropriate weld stiffness is included in the finite element model.