Fatigue Performance Evaluation for Circular Hollow Section T-Joints Strengthened Using Prestressed CFRP

This study examines the fatigue performance of circular hollow section (CHS) T-joints strengthened using prestressed carbon fiber–reinforced polymer (CFRP) sheets. An integrated experimental–numerical framework was developed to assess the hot-spot stresses, stress concentration factors, and fatigue life under axial loading. Six T-joints, with tension-to-tension fatigue loading applied to the brace end, were tested. Variables, including the CFRP width, number of layers, and prestress level, were considered to quantify the effects of prestressed CFRP on hot-spot stress distribution and crack initiation. A detailed finite-element model with explicit weld geometry was then developed and validated against the experimental data, enabling comprehensive parametric analyses. The results showed that the prestressed CFRP significantly reduced the hot-spot stresses, delayed crack initiation, and prolonged fatigue life, with wider CFRP strips and moderate prestressing level delivering the most effective strengthening. To address the computational demand of extensive parametric simulations, a data-driven prediction framework based on artificial neural networks was further established using simulation-derived stress data. This model provided a rapid and accurate approach to evaluate strengthening efficiency and predict the fatigue life of CFRP-strengthened CHS T-joints, offering practical guidance for engineering design.