Stress Concentration Factors for Butt Welds in Plated Structures

Geometric stress concentration factors for butt welds in stiffened plates have been investigated by finite element analysis. The purpose of these analyses has been to establish a data basis that can be used to develop an analytical expression for stress concentration factors (SCF) for butt welds in stiffened plates. The geometry investigated is that typical used in stiffened plates in floating production vessels and ships. The geometry is also considered to be in the relevant range for semisubmersibles. Stress concentration factors are derived at the butt weld in the midway between the longitudinal stiffeners and at butt welds in way of cope holes of the longitudinal stiffener. Based on the performed work an equation accounting for eccentricity of plates due to fabrication tolerances and difference in thickness is derived that also has been included in the DNV Recommended Practice for fatigue analysis.