Wind-induced vibrations of nonsymmetrical structures

Even high slender structures of beam type, like masts, do not always deflect in the same plane as the loading acts. The nonsymmetry of the cross-section or imperfections of the material evoke a combined response in space. Torsion can occur too: it can be coupled with the bending through the guy supports, if the forces in windward and leeward guys of the support are different. Torsional vibrations were verified on a model in a wind-tunnel and on a real mast. The new TV tower in Prague (1991) is a self-supporting one of nonsymmetrical cross-section. The vibration modes with prevailing torsion were calculated by FEM and measured in situ.