Technical Advances of Temporary Facilities for the Failure Prevention of Large-Span Cantilever Casting Construction of Mountainous Concrete Box-Type Arch Bridges

摘要

In the highways of mountainous areas, the erection of the large-span reinforced concrete box-type arch bridges using the cantilever casting method has unique advantages due to its adaptability to those environments. However, what prevents engineers from choosing this design in practice is that, the efficiency, cost, and safety problems resulting from the defects of the temporary facilities, which are due to the span increase, may immediately make the scheme less attractive. To fully consider the merits of this bridge type, new techniques of the temporary facilities are developed. A new form traveler based on the feathers of such arch rings is invented to promote erection efficacy; this new form further facilitates the technical upgrades of the buckle-anchor system monitoring-control and temporary prestressing design, which together eliminate the difficulties brought by the span increase. The inverted-type triangle traveler composed of tiled main truss structures, with the walking hook and anchor tie rod detached, is used to achieve space adaptability, light weight and modularization. The semiautomatic deviation-rectifying system, which combines the technologies of real-time data collection of the buckle pylon deviations and automatic synchronized tensioning, is developed to ensure the safety of the buckle-anchor system. The temporary short prestressed tendons are designed for control of the arch ring tensile stresses. The effectiveness of the technical upgrades has been demonstrated in the construction application of the Shatuo Bridge in Guizhou, China, which provides a promising alternative for the construction of large-span box-type arch rings of concrete arch bridges with a low cost, high efficiency, and high safety assurance.