Time Domain Wind Fatigue Analysis of Offshore Bridge

Abstract

Wind-induced fatigue presents a critical challenge in the design of offshore bridges, subject to dynamic and stochastic wind forces that induce complex vibrational responses and cumulative structural damage. Traditional frequency domain analysis, while computationally efficient, tends to yield conservative estimations that may lead to structural overdesign and necessitate frequent maintenance. This thesis advocates for a shift towards a time-domain approach for wind fatigue analysis on offshore bridges, aiming to enhance predictive accuracy and reduce the conservative bias in damage estimations and fatigue life assessments. Employing time-domain analysis, this research comprehensively examines the fatigue responses of offshore bridges to wind forces, offering a deep understanding of fatigue mechanisms and their implications for structural integrity and maintenance. This method excludes wave loading to isolate and assess the impact of wind loads indepth. The study commences with the generation of a stochastic wind field using TurbSim, followed by simulations of dynamic wind loads on an offshore bridge using the combined capabilities of USFOS and FATAL (Fatigue Analysis Tool). These simulations leverage detailed geometrical data and field conditions of a case-study bridge, provided under anonymity by the asset owner. The research meticulously investigates the sensitivity of the structure’s response to varying wind profiles, quantifying the resultant stress cycles to determine cumulative damage and predict fatigue life. Expected outcomes of this thesis include a refined predictive model for assessing windinduced fatigue, which could significantly enhance the design and maintenance strategies employed in offshore engineering. The findings aim to establish more accurate and reliable design parameters, promoting cost-effectiveness while upholding rigorous safety standards. Keywords: Wind-Induced Fatigue, Time-Domain Analysis, Offshore Bridges, Structural Integrity, Fatigue Life Assessment, Dynamic Loading, TurbSim, USFOS, FATAL Software, Stochastic Wind Modeling