Fatigue of slender light-weight structures due to wind load

conference paper

English

One of the most important loads acting on slender light-weight structures is the effect of a wind stream. The wind action can be treated as a static or as a dynamic loading. Most of the lightweight pedestrian bridges, with a relatively narrow cross-section attacked by the wind, are loaded by a dynamic action of the wind. This kind of load exhibits a concurrent vortex shedding within the wake of the structure that can be treated as a stable oscillation having known the energy magnitude corresponding to the frequency. This phenomenon was first described by Strouhal who pointed out that the vortex shedding is describable in terms of a non-dimensional number St = Ns D/U. The importance of such number for structural design can be easily proved. Knowing the wind speed U and the aerodynamic diameter of the structure D (characteristic dimension of the structure projected on a plane normal to the wind flow), and of course the Strouhal number St of this structure, it is possible to calculate the frequency Ns of the vortex shedding and thus to know the frequency that must be avoided in order to prevent the structure from a resonant vibrations originating from the action of the wind. For the lifespan of the structure these oscillations lead to the high-cycle fatigue and thus problems with breaking of the wires in suspended cables and cracks in welds of structural connections. This article describes a method for obtaining basic input data for the fatigue analysis invoked by the action of the wind.

Wind Effects, Vortex Shedding, Strouhal Number, Fatigue, Resonance

NEVAŘIL, A.; KALA, J.

2005

1. 1. 2005

Barcelona, Španělsko

84-95999-78-1

Proc. of Int. Conf. Computational Plasticity VIII

918

921

4