A novel driving force parameter [formula omitted] for fatigue crack propagation in prestressed-CFRP-repaired steel structure

Abstract

A study was numerically and experimentally conducted to investigate the crack driving mechanism of steel structures strengthened with non- and prestressed CFRP (Carbon Fiber-reinforced Polymer) plates. A novel and simple crack driving force model using both ΔKeff and Kmax was established to account for the interplay of cyclic and monotonic damage by introducing a correlation factor to define their contribution. The extensive crack growth curves of tensile fatigue testing under constant amplitude loading were referred to in the literature, and finite element method (FEM) modeling was performed to calculated the stress intensity factors (SIF) of the specimens. The relationship between the correlation factor and stress ratio (R-ratio) was determined by the reverse-reasoning method through the remaining life in the experimental data. Then the fatigue tests of different steel elements, including tensile plate, I-section and RHS beam, were used to verify the prediction accuracy. These results validated the proposed method that provides much higher accurate estimation of the remaining fatigue life at a wide range of R-ratios comparing to the traditional methods, such as crack closure model and two crack driving force model.