The Research On Stability Of Local Members In Long Span Steel Trussed Arch Bridge

Because of the advantages in economy, beautifull architectural shape, larger carrying capacity and larger stiffness, the steel trussed arch bridges have great competition among the highway bridges, railway bridges and combined road and railway bridges. With the development of economy in our country, the steel trussed arch bridges will be built more and more. But under the effects of environment factors, especially the cycle load of vehicles, the local members of bridges often fatigue or crack, so the stiffness of the local members will decrease. To study the effects of truss members′stiffness varying on the whole structure stability is very important. Because of flexible tuss members with high strength and light mass, the base frequence of local member is low. There are many local members with bluff body section such as H shape and box shape. Because of low damping in these local members, the aeroelastic stability and vortex shedding are the important issues in designing of steel arched bridges.GuangZhou XinJiaoMen steel trussed arch bridge, which is under design, was studied in present thesis. Based on summarizing the stability theory and wind-induced vibration of structures, following works were investigated in present thesis. We have studied how the single web member affects the whole stability of the bridge, and found the key web member which affects the stability sharply. Research of the effects on stability of the bridge, the varying stiffness of key web member was done also. Studying how the variational stiffness and mass of the whole web members and the transverse brace work on the stability of the bridge was made from the view of design. The aeroelastic stability and vortex shedding of the local members were tested with section model wind tunnel test. A further testing research is done as the member had a great vortex-induced vibrationduring the wind tunnel test. We studied how the stiffening rib, the mass and the damping affect the vortex-induced vibration with the wind tunnel test. In the last part of this thesis, we studied the vortex-induced vibration control for case the vortex-induced vibration occurred during the wind tunnel test of member. And TMD was adopted to control the vortex-induced vibration of the local member under wind. The parameters of TMD were confirmed by the means of section model wind tunnel test. The effects of TMD on vortex-induced vibration control of local member are perfect for the needs of engineering.