Study On The Tension Control Technology Of Suspender Of Long-span Concrete-filled Steel Tube Arch Bridge

Concrete-filled steel tubular arch bridge has gradually become one of the most popular bridge types among bridge designers all over the world due to its graceful shape,reasonable stress form and large span capacity.However,due to the short history of concrete-filled steel tubular arch bridge,the research on its construction control is crucial to ensure the safety of the structure in the construction process,the comfort of driving during operation and the durability of the bridge structure.As the main load-bearing member of the concrete-filled steel tubular arch bridge,the tension control technology of the suspender will directly affect the completion state and service performance of the concrete-filled steel tubular arch bridge.Based on a large-span concrete-filled steel tubular arch bridge,this paper studied the tension control technology of the long-span concrete-filled steel tubular arch bridge.In this paper,the finite element software Midas/Civil was used to establish the analysis model of the concrete-filled steel tubular arch bridge.The stress-free state method and the influence matrix method were selected to calculate the tensile force values of the optimized arch bridge suspender,and the technical route and calculation analysis of the two methods were integrated.In terms of process and control results,the two methods were comprehensively analyzed.At the same time,the three influencing factors affecting the internal force of the suspender were studied,which provided reference for the tension control of the same type of concrete-filled steel tubular arch bridge.The main conclusions of this paper were as follows:(1)After the stress-free state method is adopted to control the tension of the suspender,the control effect of internal force and stress state of arch rib and tie beam under the condition of arch bridge completion is better than that of influence matrix method.(2)Unstressed length of concrete-filled steel tubular arch bridge with suspender tensioning process control,get the optimization of the internal forces of the suspender and the suspender into a bridge internal force design values,compared to 3.4%,the maximum deviation along the bridge inverse bridge to 3.8%,the maximum deviation difference are inthe 10% range,meet the suspender design requirements,and the internal forces of the suspender uniform distribution as a whole.(3)The influence matrix method is used to adjust the internal force of the suspender in the direction of forward and reverse bridge three times.The maximum deviation decreased from 159.266 kN to 25.431 kN,and the proportion of the maximum deviation decreased from16.13% to 1.44%.The maximum deviation from 164.200 kn to 12.799 kn,the maximum deviation from 16.51% to 1.86%,the final optimization result is close to the design value of the bridge state suspender internal force.(4)The influence matrix method needs to take the design value of the internal force of the derrick in the bridge state as the target value and the initial value of the internal force of the derrick in the bridge state as the initial value for optimization.The optimization results are affected by two factors at the same time.Therefore,the influence matrix method has certain limitations in the control and adjustment of the suspension process.(5)Stress-free state method for suspender tension control process with the unstressed length of suspender,has nothing to do with the suspender of before and after the construction process,and its technical route is simple,calculation and analysis process is more easy to implement than the influence matrix method,so stress-free state method is more suitable than the influence matrix method as a large span concrete-filled steel tubular arch bridge for suspender tensioning process control technology.(6)The sensitivity analysis of the internal force of the suspender shows that selfweight of concrete has the greatest influence on the internal force of the suspender,especially the suspender at both ends of the arch bridge.For every 0.5kN/m cubed increase in the concrete bulk density,the internal force of most of the suspenders in the middle span increases by nearly 17 kN.When the temperature rises,the internal force of the suspender will increase,and it has a great influence on the internal force of the suspender at both ends of the arch bridge.The shrinkage and creep effect of concrete in the early stage has a relatively large impact on the internal force of the suspender at both ends of the arch bridge.After 600 days of completion of the bridge,the influence of concrete shrinkage and creep effect on the internal force of the suspender gradually becomes stable.