Design and Construction of a Hybrid Suspension and Cable-Stayed Bridge with Arch Pylon

The Longcheng Bridge is a three-span hybrid suspension and cable-stayed bridge with arch pylon and with span arrangement(72+114+30) m.The arch pylon is made up of two parts of the cable pylon and the secondary pylon.The cable pylon is a steel box structure with variable cross section and the angle of intersection between the cable pylon and the secondary pylon is 60°.The main girder is also a box structure.By means of the MIDAS/Civil software,the global structure of the Bridge is analyzed and the tensile force of the main cables under the action of the structural gravity is determined to be 53 000 kN.In accordance with the initial equilibrium status,the inverse analysis is made to obtain the setting-out length and the spatial coordinate of the main cables.The anchorage for the cables are used with the three-section splay saddles,the new type of the steel anchor boxes are developed so that the cables can be anchored in a relatively great concentration force way in the narrow space.The arch pylon is assembled at the site and is installed by the vertical rotating method(pulling-up method).The suspenders on each side of the main cables are of three groups and the four suspenders in each group are simultaneously tensioned to the designed value at one time each time in order to apply load to and adjust the main cables.