Design of Half-Through Cable-Arch Bridge with 700 m Main Span

As the span of arch bridges increases, the stability problem of the arch rib is becoming severe and the huge horizontal thrust needs to be balanced with tie rods or foundation; meanwhile, large anchors of a long-span suspension bridge costs a lot. Aiming at the two problems above, a new type of bridge structure, half-through cable-arch bridge, was proposed based on mechanical properties of arches and cables. The specific structure and force mechanism of this new type bridge are elaborated. First, arch rings are added to both the main span and side span of a suspension bridge. Then, its anchors are removed and main cables are anchored to the side arch feet. Finally, by choosing appropriate parameters such as sag-to-span ratio, rise-to-span ratio and arch-axis coefficient, the tension of main cable, the thrust of main arch and the thrust of side arch can be basically equal in value under dead load, so that the structure is in a state of no thrust and thus structural mechanical properties can be improved. Taking a half-through cable-arch bridge with a 700 m main span as an example, the design of its structural layout and components are described in details and a sequence of construction steps is suggested. Finite element analysis shows that the arch and cable of half-through cable-arch bridge share the load of bridge deck; compared with the continuous arch bridge under the same conditions, the half-through cable-arch bridge can increase the strength bearing by nearly 25% and increase the stable bearing capacity nearly by 70%. In addition, the horizontal force generated by the structure is nearly zero under dead load, which lays a solid foundation for breaking through the span limit of arch bridges.