Design And Construction Monitoring Of 120m Steel Box Tied Pole Arch Bridge Of Luanhe River

The rationality of the suspender force of the through steel box tied arch bridge is related to the alignment and stress state of the whole bridge structure.Therefore,it is necessary to study the reasonable suspender force in the bridge and construction stage.In the process of calculation and research of through steel box tied arch bridge,it is found that the change of some parameters has a certain influence on the internal force and alignment of bridge structure.The influence of parameter change on the internal force and alignment of bridge structure is studied.In this thesis,the 120 m through steel box tied arch bridge of Luanhe River Bridge(main bridge)is taken as the background project.The finite element software is used to analyze it,and compared with the measured data of the monitoring site.On this basis,the design research is carried out.The main research contents are as follows :The existing optimization methods of suspender force of arch bridge are summarized,and the corresponding finite element model of Luanhe River Bridge(main bridge)is established.The suspender force,suspender tension sequence and initial suspender tension of the background bridge in this thesis are optimized and analyzed,and the target cable force value is finally obtained.At the same time,the construction process of the background bridge is monitored,and the measured value and the theoretical value are compared and analyzed.In view of the problems in the construction process,the influence of the beam height of the main longitudinal beam and the longitudinal slope of the bridge on the bridge structure is studied,and reasonable suggestions are put forward to provide reference for the design and construction of similar bridges in the future.Through the above research,the following conclusions can be drawn :(1)Five optimization calculation methods(i.e.rigid suspender method,rigid support continuous beam method,zero displacement method,minimum bending strain energy method and unknown load coefficient method)are used to optimize the completed suspender force of Luanhe River Bridge(main bridge)with single objective function and multi-objective function as constraints respectively.The results show that the calculation results of unknown load coefficient method with multi-objective function as constraints are better than those of other single objective function as constraints,and it is more suitable for the completed suspender force optimization of Luanhe River Bridge(main bridge).(2)Four different tensioning schemes are formulated,and the initial tension of the suspenders of the four tensioning schemes is calculated by the reverse method.Then the initial tension of each tensioning scheme is substituted into the finite element model for forward calculation.The stress changes of the main longitudinal beam and arch rib and the change of the suspender force are compared and analyzed.Finally,it is found that the tensioning scheme from the mid-span to the beam end is better than the other three tensioning schemes,which is the optimal tensioning scheme.Therefore,the tensioning sequence from the mid-span to the beam end is selected as the tensioning sequence of the bridge.(3)After obtaining the target bridge suspender force and the optimal tensioning sequence,the initial tension of the suspender is optimized by the difference iteration method and the reverse method.The calculation results of the two calculation methods are compared and analyzed.Considering the mechanical behavior of each suspender in the construction process or the construction economy,the initial tension of the suspender obtained by the difference iteration method is the most suitable.(4)During the construction of Luanhe River Bridge(main bridge),the stress,alignment and suspender force of the main longitudinal beam and arch rib were measured and compared with the theoretical data.The results show that the two data are basically consistent,and the difference meets the relevant specification requirements.In the construction process,the Luanhe River Bridge(main bridge)was designed and studied for the design ideas,construction errors and other influencing factors,and the influence formulas of the main longitudinal beam height and the longitudinal slope of the bridge on the corresponding bridge structure were fitted.The results show that under different loads,the beam height of the main longitudinal beam increases,the bending moment on the main longitudinal beam increases,the bending moment on the arch rib decreases,and the vertical deflection of the two decreases,which greatly improves the internal force distribution between the main longitudinal beam and the arch rib;under the combined action of dead load and live load,when the longitudinal slope is 1 %,the maximum stress value of the main longitudinal beam and arch rib control section is the smallest,and the bending moment value,vertical deflection and the difference of suspender cable force at symmetrical position are small.(5)Finally,the research of the full text is summarized,and the research of the full text is prospected.