Stress Mechanism of Concrete Spine Girder of ExtraDosed CableStayed Bridges and Structure Optimization

Abstract:

Changshan Bridge is an extradosed cablestayed prestressed concrete bridge with two cable planes. Its 260m main span is the longest among the same type of bridges. In order to ensure the reliable force resistance of its main girder, a new beam type, i.e. spine beam, was proposed firstly based on the forcetransmission mechanism between the cables and girder. Furthermore, the layout scheme of the multidirectional mixed internal and external prestressing tendons was determined through optimization analysis, especially the bow prestressing tendons arranged at the bottom flange of the main girder. The stiffeners installed in the triangular side boxes rather than diaphragm were used to transfer lateral forces. The fullbridge finite element model was established for numerical analysis. The calculation results show that the stress and deflection of the full bridge are far below the specification limits under the most unfavorable condition. The shear lag of the main girder is significantly improved. The lateral force of the main girder is more uniform and reasonable.