Aerodynamic Performance Investigations Of A Long-Span Cable-Stayed Bridge Through Sectional Model Tests

Wind is one of the most important factors that needs due consideration inconceptualization and design stages of long span bridges. The span of modern bridges is everincreasing, leading them to be more slender and susceptible to various wind-inducedvibrations including flutter, buffeting and vortex-induced vibrations. Nowadays, wind tunnelexperiments have become a necessary ingredient in the design of long-span bridges, andsectional model tests of bridge girders are usually sufficient to capture the salientaerodynamic features of the whole bridge. In this thesis, the susceptibility of wind-inducedvibrations (especially flutter and vortex-induced vibrations) of the bridge deck of a proposedcable-stayed bridge (namely the Qinglan Cable-Stayed Bridge) is examined by wind tunneltests and some analytical skills. The thesis is developed in four chapters.Chapter1consists of an introduction of research background and synthesis of researchcontent, the engineering background for the present study is also summarized.Chapter2contains a brief introduction of three kinds of wind-induced vibrations commonlyencountered for bridge decks of long-span bridges, namely flutter, buffeting and vortex-inducedvibrations. A particular emphasis has been placed on vortex-induced vibrations and severalbridges experienced unexpected vortex-induced vibrations have been reviewed.Chapter3describes wind tunnel investigations of the proposed Qinglan cable-stayedbridge with a main span of300m. A1:50rigid section model is designed and fabricated,which duplicates the geometrical configuration of the bridge deck of Qinglan Bridge. Themodel is elastically suspended in wind tunnel by coil springs whose stiffness is determinedfollowing similarity principles. Wind tunnel tests for the original deck section shows that bothflutter and vortex-induced vibrations develops below the design wind velocity. Aerodynamicmeasures are studied to improve aerodynamic performance of the bridge deck.In Chapter4, a method used by Eurecode for predicting the amplitude of vortex-inducedvibration has been introduced and is applied to calculate the vibration amplitude of the vortex-induced vibration of the Qinglan bridge using the same parameters as in wind tunnel tests.The correlation length defined by Eurocode and Wilkinson is applied. The calculatedamplitude is compared with those from wind tunnel tests. It is found that the result calculatedwith Eurocode’s correlation length is closer to the experimental results while Wilkison’scorrelation length yields larger than experimental values.