Research On Construction Optimization Design Of Superwide Steel Tube Reinforced Concrete Arch Bridge

With the development of modern society and the development and application of new technology,new method and new material,the construction of steel tube concrete rigid skeleton arch bridge has a new aspect.However,at present,there are still some aspects that need to be optimized in the construction of concrete-filled steel tubular arch bridges,there is no better and more comprehensive understanding of the key technology and its importance of concrete filled steel tubular rigid frame arch bridge,which is not of great significance in guiding the technology in practical construction projects,therefore,the key construction technology optimization of concrete filled steel tubular arch bridge needs the combination of theory and practice.So that China’s construction of such a bridge can be more scientific and economic.In this paper,based on the project of Mixigou Bridge in Wanzhou,the finite element model of the bridge is established by using the software MIDAS,this article mainly from the main arch ring arch rib hoisting control and its system calculation,concrete pouring in the tube and its external concrete pouring,and so on.The concrete research is as follows:(1)to ensure that the state of steel pipe arch is consistent with the state of theoretical calculation,a comprehensive construction control method is adopted in the construction process.The comprehensive method is to compare and analyze the measured and predicted values of arch axis,buckle,back cable tension and key section stress during construction.Through construction control,the construction and installation of the stiffening Skeleton Arch Rib embodies the orderly scientific procedure,which can minimize the influence of various factors in the process of hoisting,so as to ensure that the arch-forming state is consistent with the design theory state.(2)in the aspect of releasing the cable force after the segment of arch rib is closed,the scientific and reasonable method of "releasing the cable force step by step and step by step" is adopted,and the cable force is divided into three levels from top to bottom step by step,which ensures the smooth force of the structure and makes the cable force distribution balanced,the risk in the construction process is reduced by preventing the sudden increase of the load bearing part of the cable force.From the view of practice,the whole process of loosening cable is smooth,and the measured value is in accordance with the theoretical value.(3)concrete pouring in steel tube: in the original design and construction procedure,the top string tube was first poured into the middle part,then the bottom string tube was poured into the left and right side,and then the top string tube was poured into the left and right side Finally,the left and right lower chord were injected,and the left and right upper chord were injected again.The concrete strength reaches90% of the design strength after one chord at a time.In order to improve the construction efficiency,the original design construction procedure is optimized to a certain extent.The construction procedure is to be changed into simultaneous pouring of upper and lower chord in the middle,and then pouring left and right lower chord in the middle,at last,the left and right top chords were injected simultaneously.After two sections of chord are poured,the concrete strength reaches 90% of the design strength,and the next stage of pouring is carried out.After calculation and analysis,the new construction procedure meets the design requirements in strength,stiffness and stability,and has practical significance.(4)external concreting: the Construction Scheme of external concreting presented in this chapter is a compromise between the traditional construction scheme from the arch foot to vault and from the vault to the arch foot,it is also an optimization of this type of arch bridge,and the result is very obvious in the deflection variation law and trend of the structure.During the construction process,the interface stress of the arch foot of the main arch ring structure basically assumes the linear change,and the stress change trend of the arch top section is relatively uniform,and there is no obvious fluctuation,the corresponding key section stress in the construction process,will be more conducive to field control analysis,structure and tends to be safer.In the construction of this type of arch bridge,the influence of concrete pouring scheme on the stability of the structure is very obvious,especially in the early stage of construction,which should be paid close attention to,in the later period,the corresponding stability coefficient is basically the same.The application results of the bridge show that the construction scheme of the external concrete is reasonable and feasible,the advantages are obvious,the structural linear change is reasonable and the stress distribution is uniform.(5)through the analysis of the influence of the parameter design change of the steel tube reinforced skeleton concrete on the construction,it is concluded that the stability is better in each construction stage by increasing the unit weight of the external concrete,the influence of stress and Deflection at 1/4 Cross section is greater than that at 1/4 Cross section,and the influence of Cross section is smaller.On the premise of improving the concrete strength in the pouring pipe,the stresses and deflections of the1/4 section and the mid-span section corresponding to each construction stage and the1/4 section and the mid-span section corresponding to the concrete strength in the pouring pipe before increasing have not changed at all,the basic coincidence of Discount Diagram data shows that the change of concrete strength parameters in the pouring pipe has little effect on the construction.