Cantilever Construction Control Of Highway-Rail Continuous Steel Truss Bridge And Key Technology Optimization Of Closure

The advantages of the continuous steel truss girder bridge for public and railway usage include high rigidity,strong bearing capacity,broad span,simple and quick maintenance,and space savings,making it an important bridge type for modern bridge construction.However,the steel truss bridge has a long construction time for the cantilever assembly,numerous structural rods,complex structural rod forces,significant temperature influence on the rods during closure,high closure accuracy requirements,and difficulties in rectifying closure mistakes.As a result,it’s critical to research how to secure the structure’s safety throughout assembly and the effective completion of the steel truss bridge’s structural closure.This paper uses the construction of the Zhengzhou Yellow River special bridge of the Zhengji Railway as a case study,and uses the finite element software Midas Civil to simulate the entire bridge,analyze the stress and deformation of the continuous steel truss cantilever assembling to the bridge formation at each construction stage by combining simulation calculations with actual measurement data,and optimizes the construction process at the same time.The main results of this paper are as follows:(1)Establish the finite element model of the whole bridge,use the positive assembly analysis approach to examine the structure’s stress state and deformation law at each step of construction,and look for the most unfavorable stress-bearing rods.The results reveal that the cantilever assembly process,rod stress,and support reaction force are all less than the material’s permissible stress,indicating that the structure is safe in use.The main pier between the stiffened chord joints experiences the most adverse forces.(2)The influence of the construction of highway bridge panel on the displacement of the closure is analyzed,and the optimal placement combination of highway bridge panel is obtained according to the law of change of the displacement of the joint.The results reveal that after optimizing the placement of highway bridge panel,the vertical displacement of the bridge joint is obviously adjusted,which is most favorable to the bridge joint,and the rod stress and pier support reaction force meet the design requirements,and the structure is safe.(3)Based on the numerical analysis and field monitoring results,the closure temperature sensitivity of the main bridge structure is systematically analyzed.The results show that the optimum closure temperatures of the north closure and the south closure are 22℃ and 28℃,respectively.Before closure,the north bank moved 79 mm northward and the south bank moved 88 mm southward.And put forward the main bridge closure error adjustment method,closure construction method and other construction scheme,in order to guide the bridge closure construction smoothly.(4)The finite element software Midas Civil was used to simulate and analyze the structure of the main bridge after closure,and the effects of the overall temperature,partial temperature and extreme temperature on the structure were studied respectively.The results reveal that the temperature load has a great influence on the longitudinal displacement of the structure,and has little influence on the vertical and lateral displacement.Partial temperature and extreme temperature have great influence on the structural stress,and the overall temperature has little influence on the stress of the main truss,less than 1 % of the allowable stress of the material.The most unfavorable stress rod occurs between the stiffening chords at the top of the main pier,and the 382 pier support is the most unfavorable support,which provides reference for future bridge maintenance.(5)The measured nodal elevations were compared with the design elevations through construction monitoring,and the measured stresses in the rods were compared with the simulation calculations.The results reveal that the structural stress is safe and the alignment is smooth in each construction stage during cantilever construction.The construction error of each construction stage is within the allowable range of the specification,and the model is in good agreement with the measured data.The cantilever construction process is reasonable,and the continuous steel truss girder erection construction is safe and reliable.