Construction control of reinforced concrete arch bridges

Abstract

Reinforced concrete arch bridges are ideal to span over river valleys or deep ravines. However, the construction of the arch rib is very often the most crucial aspect that may influence the feasibility of the bridge. Casting concrete in situ on formwork and falsework supported directly on the valley is often out of the question. One method that is gaining popularity in recent years is to use precast concrete segments erected by the cantilever construction method with tiebacks. As the tiebacks are temporary and therefore recoverable, the method is considered to be very economical. This paper describes a method for construction control. It uses the concept of influence matrix in the adjustment of cable forces to keep the stresses in the arch rib within acceptable limits as well as to ensure that the arch rib is constructed to line and level. It is observed that the required minimum tieback forces vary during the progress of cantilever erection. Various strategies of tensioning the tiebacks have been studied, and it is found that a two-stage tensioning method gives acceptable results. The recent application of the proposed method and the results are also described.