Research On The Allowable Amplitude Of Steel Bridge Tower Vortex-induced Resonance

Steel bridge towers have the characteristics of light weight, small damping, sensitivity towind and so on, are prone to vortex-induced resonance. Vortex-induced resonance of pylon isa limiting vibration, but it occurs at low wind speeds, and the amplitude is large enough toaffect the structural strength and fatigue, it can also affect the security of the constructionmachinery, construction workers and the comfort of the construction workers. It is necessaryto take measures to limit the damping amplitude of pylon vortex-induced resonance within theallowable range. Therefore studying the allowed values of vortex-induced resonanceamplitude of steel bridge towers is very significant.This paper takes the towers of Jianghai Zhida Bridge plan I, Jianghai Zhida Bridge planII and3th Nanjing Yangtze River Bridge as examples, studies the allowed values ofvortex-induced resonance amplitude of steel bridge towers and the relationship betweenallowed values and tower height, and summed up an estimate formula of the allowableamplitude about tower height. Taking the ratio of the maximum allowable stress produced bymain beam vortex-induced resonance and permissible stress of steel as a reference, assumingthe ratio of maximum allowable stress of the tower control section produced by towervortex-induced resonance and permissible stress of tower stell is equal to main beam. So viathe permissible stress of tower steel can get the allowable stress of the tower control sectionproduced by tower vortex-induced resonance. Then the allowable stress is regarded as thecontrol condition to get the allowable amplitude of bridge tower. At the same time, theallowable amplitude of main beam vertical vibration is regarded as the control condition tostudy allowable amplitude of tower along the bridge vortex-induced resonance at the finish ofthe bridge. In other words, the vertical amplitude of main beam caused by vortex-inducedresonance of tower should not exceed the allowable value.In addition，this paper also evaluated the comfort of the construction workers when theamplitude reaches the maximum allowable value. Finally, the wind tunnel test of bridge towerwas introduced in the thesis. Then test results and allowable values were compared.