The Analysis Of Effect Of Construction Procedure On Structural Behavior For Half-through Concrete-filled Steel Tube Arch Bridge

Construction of concrete-filled steel tube(CFST)arch bridge experienced hoisting steel tube,pouring core concrete and pouring externally wrapped concrete.Steel tube truss is framed,concrete-filled steel tube arch and reinforced concrete arch are formed in order.During the construction period the structural internal force is very complicated.Half-through CFST arch bridge is seldom used in practical engineering.There are relatively few studies on the construction of externally wrapped concrete.To study on the effect of different construction procedure on structural behavior,taking Guang’An Qujiang river bridge — half-through CFST arch bridge as the research object,Midas/Civil is used to build the finite element mode of the bridge.The main work is as follows:(1)Division schemes of externally wrapped concrete has an important influence on the structural force.The externally wrapped concrete of half-through arch rib is vertically divided into 2,3,4 and 6 cycles respectively.Advantages and disadvantages of these four schemes are evaluated through comparing and analyzing the stiff skeleton stress,the externally wrapped concrete stress and the arch rib alignment.(2)The causes of stress mutation at the junction of each working face are analyzed.Based on the structural stability,some suggestions,the externally wrapped concrete section should be divided uniformly when making construction plans,are put forward.(3)The the formula for calculating the vault deflection of CFST arch bridge during pouring externally wrapped concrete is derived based on the theory of influence line and superposition principle.For multi-point balanced pouring method,the different division schemes for length of the concrete face are compared and analyzed.To minimize the sum of vertical vault deformation as the goal,the pouring procedure is optimized based on the exhaustive algorithm and the optimized scheme is obtained.For the external forces balanced pouring method,the formula for adjusting arch rib alignment is derived and is verified based on analyzing Midas/Civil model.(4)Through analyzing the structure,it is shown that the original pouring sequence of transverse braces(the original design and construction plan)will cause excessive tensile stress in the externally wrapped concrete section at skewback.In thisregard,based on the influence line theory,the effect of load position on influence coefficient of the externally wrapped concrete stress at skewback is obtained.The main reson for the tensile stress in the externally wrapped concrete section at skewback are analyzed qualitatively.Based on the exhaustive algorithm,comparing the tensile stress value and the structural stability with different pouring sequence,the optimal scheme of transverse braces’ pouring sequence is obtained by analyzing qualitatively.At the same time,the results of this study have been paid attention to by the relevant units.A series of design alteration,adjusting the sequence of pouring transverse braces and increasing reinforcement in the externally wrapped concrete stress at skewback,are made for this problem.