Study Of Construction Control Technology Of Cantilever Concrete Arch Bridge With Span Of 300m

With the further increase of the arch bridge span,when the cantilever pouring method is used to construct a large-span concrete arch bridge,the long cantilever structure will bring a great burden to the anchoring system,and the arch line shape and stress during the construction process are also difficult to control.Partially cantilevered concrete arch bridges with partly rigid frameworks are used to realize the closure of the arch ring in advance,which can significantly reduce the anchorage cable force,reduce construction risks,and speed up the construction progress.Relying on the key scientific and technological research project of Chongqing Municipal Education Commission "Key Techniques for the Design and Construction of 300 m Cantilever Casting Reinforced Concrete Arch Bridge",this paper carries out the following research contents:(1)For the 300m-level concrete arch bridge constructed by the combination method of "cantilever pouring + rigid skeleton",the design and research of the arch ring structure and structural dimensions are carried out.In order to reduce the self-weight of the arch ring and enhance the stability of the top and bottom plates,research on the box girder structure with longitudinal ribs on the top and bottom plates was carried out;Under the most favorable conditions for shear resistance,the structural design of the section steel frame is carried out;through the optimization analysis of the rise-span ratio and the arch axis,a reasonable arch axis shape is obtained;the full bridge bearing capacity analysis is carried out on the basis of the trial design.(2)For the 300 m concrete arch bridge,carry out the design of the cable-stayed buckle for the arch ring construction and the research of the construction monitoring.According to the construction control objectives of different concrete arch bridges constructed by the combined method,it is proposed that the buckle cables hung on the cantilever pouring section box girder should be controlled by the arch ring section tensile stress,and the buckle cables hung on the rigid frame should be assembled with the rigid frame In the process,displacement is used as a feasible region algorithm for controlling the cable force,and the research on the construction control of the main arch circle is carried out based on this.The tensile stress of the arch ring section is controlled within 1.5MPa,and the displacement of the rigid skeleton assembly process is controlled at 4cm as the limiting condition.The construction control analysis is carried out using MIDAS/Civil finite element software,focusing on the arch ring,junction pier and steel buckle tower in the whole Conduct relevant research on stress and alignment during construction.(3)After the rigid frame is closed,the concrete tensile stress may be exceeded by pouring the entire section of the arch ring with the hanging basket.It is proposed to improve the force of the arch ring by removing part of the anchor cable and realize the redistribution of the internal force of the arch ring.In the past,determining the cable removal program required a large number of program comparisons.When the bridge span is further increased and the number of anchor cables is further increased,the workload will be significantly increased.Based on the principle of the stress balance method,this paper studies the cable removal plan for the process of pouring outsourcing concrete on the rigid framework,proposes the cable removal method,and theoretically determines the optimal cable removal program.