Comparison of Fatigue Life and Crack initiation of T-Shaped CHS and SHS Welding Structures

Abstract

In civil engineering and architecture, truss structures are commonly used in constructing offshore platform structures, bridges, and high-rise buildings. These structures typically use circular hollow sections (CHS) and square hollow sections (SHS), joined by welding. Recently, the use of T-shaped welded joints with different tube shapes has become more diverse, incorporating combinations like CHS-CHS, SHS-SHS, and CHS-SHS. Traditionally, fatigue studies have been conducted separately on these CHS-CHS, SHS-SHS, and CHS-SHS types of connections. However, this study compared the fatigue life of three different welded T-shaped structures. The T-shaped joints with three different types of connections are analyzed through the fatigue finite element method (FEM). First, welding simulations of three different T-shaped connections were performed using the 3D non-steady heat conduction method to obtain heat histories. Then, a 3D thermo-elastic analysis method was employed to calculate residual stress and welding deformation based on the thermal history. In the subsequent fatigue analysis, the fatigue life and initial crack locations of the three different T-shaped structures were determined using the FE fatigue analysis method, which incorporates residual stress and welding deformation. The fatigue FE method is based on the cyclic hysteresis constitutive equation obtained through repeated load experiments and the fatigue damage theory. Finally, the fatigue life of the three types of structures is compared using the S–N curve.