Construction Monitoring Research Of Concrete Filled Steel Tubular Tied Stacked Arch Bridge

The concrete-filled steel tubular tied arch bridge adopts the beam-arch combination system.This combined system can exert its own structure performance of compression and beam bending,and solve the contradiction among the material self-weight,construction difficulty and span of the arch bridge,which has found widely application in engineering.It is a kind of innovation of tie-rod arch bridge.The arch rib adopts double arch structure,which can bear more bridge deck load,make the overall structure more stable,let the structure stress more safe,and also improve the aesthetics of the arch bridge.The concrete-filled steel tubular tie rods are complicated in force.During the construction process,key problems such as arch ribs and tie beam lines,arch ribs and tie beam stress need to be solved by construction control.In the paper,construction monitoring is taken as the main content to carry out the work in combination with the engineering background of Shenyang Hub Dacheng Bridge.The research focuses on the alignment of girder and arch rib,the construction control of girder stress and arch rib stress,and the tension and monitoring of suspender cable force.It is necessary to consider the influence of the different ratio of the span to the line and the internal force of the tie beam as well as the line and the internal force of the arch rib.The major contents are as follows:(1)Simplify the mechanical model according to the mechanical characteristics of concrete-filled steel tube(CFST)truss arch,and describe the theoretical basis for calculating the stiffness of arch rib section,temperature effect and concrete shrinkage and creep.(2)The whole bridge model was established by Midas Civil software,so as to discuss the influence of the internal force and displacement of the arch rib,as well as the tie beam under the action of constant load and ZK live load with the change of the rise-span ratio of the upper arch rib,on condition that the rise-span ration of upper arch rib is changed only but the rise-span ratio of lower arch rib remains unchanged.(3)Discuss the selection of the tension time and the times of the stretch-draw.Put forward three kinds of tension schemes combined with the actual construction and design scheme.Then carry on comparative analysis to the schemes,which focuses on effects of suspender tension scheme on arch rib displacement,concrete stress of arch rib,steel pipe stress of arch rib,displacement of girder and girder stress.It provides reliable theoretical basis for the selection of suspender tension scheme in concrete construction(4)Through Midas Civil software simulation,the results of each construction stage are calculated,and the monitoring results of the bridge construction stage are analyzed by comparing the field measured data with the theoretical data.The main monitoring stages are the demolition stage of arch rib support,the completion stage of hanger rod primary tension,the unloading stage of tie beam support,the completion stage of hanger rod secondary tension and the final hanger rod cable force adjustment stage.The above stages are monitored from four aspects: arch rib alignment,arch rib stress,tie beam alignment and tie beam stress.The results show that the stress state of the arch rib and the tie beam is well in the construction process of the bridge,the alignment of the tie beam and the arch rib meets the requirements of design,the cable force value of the suspender is closer to the theoretical value after adjustment,and the error is controlled within 5%.