Influencing factors and sensitivity analysis for the fatigue of FRP wire based on the progressive fatigue damage model

FRP cables can experience degradation of their mechanical properties due to repetitive loading, resulting in increasing attention being devoted to their fatigue performance. This study aims to quantify the impact of the following four influencing factors on the fatigue behavior of FRP wire: (i) the applied maximum fatigue stress, (ii) interfacial shear strength, (iii) fiber volume fraction, and (iv) the Weibull shape parameter of the fiber fatigue strength coefficient. The recently developed progressive fatigue damage model (PFDM) is employed herein, and an adaptive block-by-block strategy is proposed to improve computational performance. The influences of the four factors on fatigue characteristics of FRP wire are illustrated using Monte Carlo simulation. Subsequently, a sensitivity analysis is performed for the fatigue behavior of FRP wire based on the linear regression approach, and Standardized Regression Coefficient is derived to rank the significance of the influencing factors. The following three indicators are selected to evaluate the sensitivities: (i) the fatigue life, (ii) the minimum normalized residual stiffness, and (iii) size of the critical damage cluster. Results show that the fatigue life and minimum normalized residual stiffness of FRP wire are most sensitive to the fiber volume fraction and Weibull shape parameter, respectively. Increasing fiber volume fraction can lead to longer fatigue life but results in more stiffness degradation before failure. A higher Weibull shape parameter leads to less stiffness degradation but results in a shorter fatigue life. Reducing the sensitivity of the FRP wire to cyclic degradation is best achieved by increasing the interfacial shear strength. This study can provide guidance for evaluation and optimization of the FRP wire fatigue behavior.