An improved model for VIV fatigue life prediction of slender marine structures in time-varying flows

The objective of this study is to propose an improved model to evaluate the fatigue life of slender marine structures with high efficiency and accuracy. We establish two Weibull functions to represent the probability density function (PDF) of time-varying flow velocities and fatigue stress. Next, a modified Latin hypercube sampling method is developed to improve the efficiency by reducing the sampling number based on the characteristics of vortex-induced vibrations. In addition, we employ the response surface method to predict the dominant mode and select the truncation order. This method could make the calculation time of each stress amplitude within 0.1–4 s, which meets the requirement for efficiency. To further improve the calculation accuracy, the Strouhal number used in the wake oscillator model is considered to change with the reduced velocity by introducing a correction factor. Besides, the influence of the tension fluctuation from axial vibration on fatigue damage is taken into consideration. A good agreement is achieved in the comparison between the numerical and experimental results. Moreover, the improvement of the accuracy and the efficiency of the proposed model is validated. In the end, a parametric study is conducted to investigate the effect of flow PDF parameters on the fatigue life.