General Method of Wind-Induced Fatigue Analysis of Slender Structures

Wind-induced fatigue is a critical issue in design of many slender structures, but suitable engineering and standards procedures are still fragmentary. On the basis of the closed form solution proposed by Repetto and Solari (2012), this PhD Thesis develops a complete and general procedure for determining the wind-induced fatigue damage of slender structures, suitable for engineering calculations and code provisions. A new generalization of the closed form solution is proposed, covering a wide range of resistance fatigue curve types, suitable for different materials and different cyclic loading conditions. The final formulation results in complete accordance with Eurocode format for wind induced Ultimate Limit State analysis. The set of required input parameters is discussed, taking into account simultaneous alongwind and crosswind structural responses due to turbulence. Simple expressions coherent with standard format are defined for both alongwind and crosswind fatigue analysis. The significance of different contributions to crosswind-induced fatigue is examined. Although engineering procedures estimate separately crosswind maximum response to gust buffeting and to critical vortex shedding conditions, there's no guarantee such assumption would provide reliable fatigue predictions. Therefore, the possibility of separating the effects of the vortex shedding in fatigue analysis is investigated, as well as the role of parameters uncertainties in response and in fatigue evaluations, suggesting new formulations of the cycle number due to VIV. Finally, some case studies are discussed validating the proposed model.