Study On Construction Monitoring Of Suspender Replacement Of Concrete Filled Steel Tubular Arch Bridge

Concrete-filled Steel Tube is a composite structural material formed by pouring high-strength concrete into a thin-walled circular steel tube.Under normal working conditions,the interaction between two different mechanical properties materials makes the two work together.The CFST arch bridge is a new type of arch bridge structure.After the steel tubes are closed,the concrete is filled with concrete to make the two work together.The ferrule effect of the steel tube wall on the concrete improves the compressive strength and ductility of the concrete.The filled concrete increases the stability and corrosion resistance of the steel pipe wall when it is under pressure.In terms of construction,the hollow steel pipe can be used as a stiff skeleton and formwork,and the construction lifting weight is light,the progress is fast,and it is convenient for unsupported lifting or swivel constru ction.The application of the concrete-filled steel tube structure on the bridge not only fully exerts the mechanical properties of the high-strength material but also overcomes the construction problems,and promotes the rapid development of the large-span and quantity of the CFST arch bridge.For the concrete-filled steel tubular arch bridges of the bird type,the center type and the bottom type,the boom is the main force member,and the main force components of the boom are parallel wires,pier heads,a nchor cups and nuts.Under the joint action of environment and alternating load,the damage of the boom is mainly manifested in the damage of the boom sheath,the corrosion and fatigue of the steel wire,the corrosion of the anchor,the damage of the short boom,the corrosion of the tie rod and the buried pipe at the lower end.Water,etc.,the existence of these problems has a non-negligible impact on the safety of bridges.This paper relies on the construction monitoring of the boom replacement project of the Minjiang River Bridge in Nanning,Guangxi,and mainly include the following work.Firstly,a detailed construction monitoring plan is developed to analyze the safety and stability of the sling system in the boom replacement project.The entire structu re is analyzed and calculated before the boom replacement,and the structural simulation analysis and the most unfavorable state analysis of the structural stress is carried out during the boom replacement process.Reasonable design of arch rib strain sensor arrangement and arch rib and deck surface elevation measuring point layout,complete the test of the original boom cable force and the current stress state assessment and the measurement of geometric control indexes such as the main arch arch axis and bridge deck elevation.Then,the strain(stress)of the arch rib during the replacement of the boom is monitored,and the displacement of the main bridge deck,especially the position of the boom,is continuously observed when the boom is replaced,and the deformation of the arch rib during the replacement of the boom is monitored.The new sling bar force is tested after the boom is replaced.At the same time,the ambient temperature and humidity test are required.The calculation and analysis of the arch rib force,the arch rib and the deck deformation and related field test data are analyzed.After analyzing the bridge deck elevation,arch rib line type test and boom cable force test result after the replacement of the boom,the decision of the cable tensio n adjustment of the boom is made.