Vertical Erection-Rotation Method for Chorded Arch Bridge

This paper describes an arch bridge alternative using straight chords to replace curved arch ribs and the development of a simple, economic and accelerated erection method. The alteration of arch rib profile allows the arch ribs to be erected straight up vertically in the form of column bents on temporarily restrained horizontal hinge devices at the springing lines. In this way, the construction requires only a small workspace and the arch ribs can be built with better integrity and high stability as stand-alone structures at any stage of construction and thus eliminating the need for a high-cost temporary supporting system. After the half-leaf arch ribs are completed, temporary restraints at the base of erected column bents are removed to restore hinge mechanism and the horizontal rotation restraint is transferred to an external guying system. With controlled guying cable releasing, the erected half-leaf arch rib can slowly rotate down on its own weight to meet at the mid-span for closure and form a complete arch frame in just a few hours. The erection method provides superior advantages over the existing construction methods for arch bridges in terms of erection simplicity, overall construction speed and safety, environment impact and cost saving. It offers a viable solution for the arch bridge construction in congested urban areas with requirements of minimal traffic disruption, shorter construction time and lesser environment impact, or over a deep ravine having steep-sloped banks with limited workspace and lack of accessibility. The key elements of design and construction procedures are discussed, and a pilot project is included.