Conceptual design of a new type of single-tower cable-stayed arch bridge and study of its mechanical properties

Abstract

In order to overcome the apparent characteristics as a flexible structure of a long-span single-tower cable-stayed bridge and the excessive axial force of the main girder, and to exert the advantages of cable-stayed arch cooperative system bridges, this paper proposes a new type of single-tower cable-stayed arch cooperative system bridge. On the premise of the same amount of steel, the new cooperative system bridge can have a greater stiffness than the existing cable-stayed arch cooperative system bridge with the same span. The new system bridge uses the main girder as the rigid tie bar to balance the arches’ thrusts, which enables the main girder to have a smaller axial force and makes the cable-stayed arch cooperative system bridge a thrustless structure. The proposed bridge is assembled by the following method: (a) constructing a cable-stayed bridge with a steel box girder to bear part of the dead load and to act as a construction platform firstly; (b) then installing arch structures and fixing they with the girder to bear the remaining dead load; and, (c) adding web members between the arch ribs and the girder to form a variable-height truss structure with the arch ribs as the upper chords and the girder as a lower chord to bear most of the live load at last. The underlying mechanical principles were explained, and the mechanical properties of the cooperative system bridges were calculated with the finite element method in this paper. The stiffness and axial forces in the girders are analyzed by the finite element method and compared with those of the conventional bridges. The FEA results show that the new cooperative system bridge has the truss structure’s characteristics, which shows apparent advantages of stiffness and much smaller axial force in the main girder.