Field evaluation of pipe-tie system in limiting the girder rotation during bridge deck construction

The bridge deck construction of often involves different types of construction equipment to accelerate the construction procedure and form a smooth deck surface. To support the construction equipment such as deck finishing machine as well as other construction loads, overhang formwork systems have to be used during bridge deck construction. In this case, the construction loads transfer through the overhang formwork system to the exterior girder, which can result in significant torsional moments acting on the exterior girder and lead to excessive rotation during the bridge deck construction. The traditional temporary rotation prevention system uses block-tie systems to resist the torsional forces in the girders; however, this system often loses its effectiveness due to the tightening issues of ties and the improper shimming of timber blocks. In this study, an innovate temporary girder bracing system, pipe-tie system, was developed and evaluated through the field bridge monitoring. Three bridges were selected and instrumented with different types of temporary rotation prevention systems. The field monitored data were collected and analyzed, and a comparation between the traditional rotation prevention system and pipe-tie system was conducted to evaluate the performance of these systems during bridge deck construction. The results indicate that the pipe-tie system is not only the most effective system to prevent the excessive exterior girder rotation, but also a reliable and cost-efficient system for bridge deck construction.