Structural Design of Midspan Free-Axial-Force Connection Device of Danjiangkou Reservoir Bridge
The Danjiangkou Reservoir Bridge is a hybrid girder cable-stayed bridge featuring the pairs of earth-anchored stay cables.The bridge has two pylons that create a main span of 760 m.The longitudinal free expansion and contraction of the main girders in the side spans is restricted by the anchorage-type abutments,which makes the loading conditions of the pylons and the main girders complicated.To address this issue,a new type of free-axial-force connection device is installed at mid side-span,which consists of a small box girder,a large box girder,and a supporting system.At the service stage of the bridge,forces are transferred from the large box girder to the small box girder via the supporting system.The ends of the small box girder are equipped with a recentering device,allowing the small box girder to be fixed at one end and be able to slide at the other end,as a result,the small box girder can keep staying at the location of the design axis while improving the loading condition of the large and small box girders.The damping device installed at the midspan of the large box girder can suppress the rapid relative movement between the sections of the large box girder,thus ensuring the relative moving stability of the large and small box girders,and in turn enhancing the stability of the free-axial-force connection device.The finite element analysis demonstrate that the stress and strain of the overall device meet the code requirements.The loads acting on the large box girder are transferred to the small box girder via the supporting system,no stress concentration is observed in the connection location of the small box girder,and the small box girder exhibits ideal bending characteristics.
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