Reliability Analysis of Vortex-Induced Random Vibration

Under the action of incoming flow, bluff body structure may experience vortex-induced vibration (VIV). Because the resonant VIV can cause strong vibration, potentially leading to structural damage, this work specifically conducted reliability analysis on VIV. Given that real wind always includes fluctuating wind, a real VIV must be vortex-induced random vibration (VIRV). Based on the wake oscillator model, this paper establishes the VIRV equations for linear and/or nonlinear structures and transforms them into a stochastically excited and dissipated Hamiltonian system. By applying the stochastic averaging method of quasi-Hamiltonian systems, the averaged Itô stochastic differential equations (SDE) are derived. The conditional reliability function and the mean first passage time (MFPT) are governed by the backward Kolmogorov equation and the Pontryagin equation, respectively. The theoretical method is applied to the VIRV of a linear structure and a nonlinear structure, respectively. The reliability analysis is performed for both resonant and nonresonant cases. Some results from Monte Carlo simulation are obtained to verify the effectiveness of the analysis procedure.