Research On Disease Treatments And Tie Bar Replacement Implementation Scheme Of The 3rd Miangyang Fujiang Bridge

Tied-arch bridge was developed rapidly in China at the end of the 20 Century.Tie bar corroded common in tied-arch bridge built early corroded as time goes on.Study shows that tie bars have only 20～30 years of service life under the influence of simple corrosion protection measures and high stress,The design life of the tie rod is defined as 20 years in the present specification.With the development of tie rod disease and the arrival of the service life,the original tie bars needs to be replaced with a new tie bar which can be replaced.Based on the third Mianyang Fujiang Bridge,main damages are analyzed and Tie bar replacement scheme was researched.(1)Based on disease development process and maintenance history of the Fujiang River Bridge,cause of disease was summarized,Treatment measures for tie bar replacement,drainage and corrosion prevention of suspender anchor,back-grouting,deck replacement and the new steel stringer was put forward.(2)Plan for tie bar increase and tie bar substitution underequal loadwas proposed based on force characteristic and tie bar structure,qualitative analysis and finite element calculation.New increase bars not conducive to the side span,connection quality of new anchorage and original structure can’t be guaranteed.The load is replaced by a single tied bar in the Tie substitution process,the structure deformation and internal force can be controlled in a low state,structural stress and appearance are consistent before and after replacement.Tie substitution scheme under equal load was finally adopted.(3)Tie substitution scheme under equal load was studied,design of the main components and construction process were completed.Based on the finite element analysis of 61 stages for the whole replacement process,results show:Structural internal force and stress change little,structure stay safe and reliable,displacement of each section of arch rib is more sensitive.The control index of arch rib displacement was put forward.The quality control measures such as the temporary support system of side span,the protection of the side arch rib,the broken cable with stress and the pouring of concrete are put forward.Tie substitution scheme with equal load has guiding significance to detail design and site construction of tie replacement for 3rd Fujiang Bridge.At the same time,can provide the reference for other flying swallow type tied arch bridge replacement.