A novel structural stress method and stress intensity factor solutions for fatigue analysis of high-strength bolted connections in bolted spherical joints

Both bolted connections and welded joints in construction engineering are susceptible to fatigue fracture. While the structural stress method has been relatively well-established for evaluating the fatigue behavior of welded joints, it remains unexplored for high-strength bolted connections. This paper presents a novel definition of structural stress and corresponding numerical methods for the fatigue analysis of high-strength bolted connections, based on the equilibrium equations of force and moment. The structural stress, composed of membrane and bending stresses, has shown significant insensitivity to element type and mesh size in both axisymmetric and three-dimensional solid models of bolted spherical joints. On this basis, stress intensity factor (SIF) solutions for bolt cracks based on structural stress have been proposed. This approach decomposes the SIF into membrane and bending stress components, allowing for the quantification of their individual contributions to fatigue life while also considering the effects of bolt specifications. Subsequently, the effects of bolt screwing depth and diameter on stress concentration and fatigue life were discussed. Research indicates that structural stress, which considers stress concentration and loading pattern, consolidates fatigue data across various screwing depths into a narrow range. The structural stress-based SIF considers the effects of stress concentration, bolt specification, and loading pattern, consolidating fatigue data from bolts with varying screwing depths and diameters into a narrow range, with a correlation coefficient of 0.862 and a standard deviation of 0.161. This study provides novel methods and insights for the fatigue assessment of high-strength bolts.