Study On Key Technologies Of Construction Monitoring Of Long-span Tied Arch Bridge

This dissertation takes the project of a long-span concrete-filled steel tubular tied arch bridge over the 105 national highway as the engineering background,and makes a study of the key technical problems in construction monitoring: the accurate measurement of hanger cable force,the optimization and adjustment of the cable force in the construction stage,and the safety performance of cable-girder anchorage.Based on the analysis of domestic and foreign relevant research material of tied arch bridges,the above problems are calculated and analyzed by establishing finite element analysis model of full bridge using MIDAS and cable-girder anchorage using ABAQUS.Analysis and research are as follows:1.The background of the construction monitoring project of this dissertation is briefly outlined,and the key problems that need to be analyzed and studied are put forward.2.By introducing the theoretical basis of cable force test by vibration frequency method and combining with MATLAB software to carry out numerical analysis,a corresponding calculation formula of cable force test is derived.Using the basic principles of energy law,a practical calculation formula for cable force test of composite boundary conditions is deduced.Introducing the buckling function of the compression rod and combining the energy method,a practical calculation formula of cable force test that apply to the short cable of the tied arch bridge is obtained.3.The factors that affect the accuracy of the cable force test are analyzed and modified,and the practical calculation formula of cable force that apply to hangers of the tied arch bridge in this project is identified.The practical calculation formula of cable force test that has recognized each parameter is applied to the on-site cable force test.The comparison result shows that the revised practical calculation formula of cable force test has better accuracy.4.The principle of the influence matrix method is discussed,and the necessity of setting the initial tension of hangers is proposed.The tension scheme of using the influence matrix method to reach a reasonable bridge state through two tensions is presented.In the secondary cable adjustment,a small-scaled method of cable adjustment is further proposed,and the specific tension sequence and tensile force are analyzed and derived.Through various comparisons with the original scheme, the conclusion is that the small-scaled method of cable adjustment is more reasonable.5.Through finite element simulation,the distribution law of stress and deformation of each plate under the most unfavorable load is analyzed,and the safety performance of each plate in the anchorage zone is evaluated.The analysis shows that the maximum stress and deformation value of each plate in the anchorage zone under the most unfavorable loads is still within the normal working range,but there is serious stress concentration at the joint between the hanger lug and the lug stiffening plate.The safety factor of the lug stiffening plate is low and it is necessary to pay attention to the welding quality during installation.