Novel hot spot stress calculations for welded joints using 3D solid finite elements

• A traction stress-based hot spot stress calculation methodology was proposed and validated.
• Superior performance was confirmed through the extensive case studies for various structural components.
• The methodology was applied to a pontoon-column connection part of semi-submersible RIG.

This paper presents a novel numerical method through which less mesh-sensitive local stress calculations can be achieved based on the 3D solid finite element, adhering strictly to the original definition of hot spot stress. The traction stress, which is defined at 0.5t and 1.5t away from the weld toe, was calculated using either a force equivalent or work equivalent approach, both of which are based on the internal nodal forces on the imaginary cut planes. To confirm the validity of the proposed method, 5 typical welded joints widely used in ships and offshore structures were analyzed using 5 different solid element types and 4 different mesh sizes. Finally, the methodology was applied to the more complicated pontoon-column connection part of a semi-submersible RIG under a realistic wave load, and the performance of the proposed method was compared with the traditionally used surface stress extrapolation method.