A Study On The Viberation Characteristics And Cable Force Measurement Of Long Span Suspension Bridges’ Anchor Span Cables

Recently, long span suspension bridges develop fast, and this bridge type becomes the first choice of the span more than1000m. Anchorage cable force control has always been the emphasis of the construction of suspension bridges, and a reasonable and simple cable force control method with high precision to meet requirements of construction is needed. This thesis takes the construction of the Fourth Nanjing Yangtze River Bridge as its research background, and makes a detailed study on the new anchor mode of the improved backward anchor beam from theoretical calculation, controlling, measurement, and readjustment of the anchor cable force of it. The major work of this thesis is as the following:First, the theory and characteristics of cable vibration are analyzed in this thesis, the influences of boundary conditions, cable bending rigidity, sag on cable vibration are studied. The vibration of the overall system of cable and anchor beam, including the situation that an anchor beam anchors one or more cables, is researched. Detailed analysis of boundary conditions is made to find out a boundary condition closest to the actual construction. Analytical calculation and finite element of the cable is analyzed to determine the accuracy of the cable force calculation methods.Second, some common cable force measuring methods are introduced and the application of frequency method is deeply analyzed. The cable force calculation method that combines the frequency method and finite element analysis is introduced. This method with high precision is simple and easy to do, and then is adopted as the calculation method of anchor cable force in this thesis. Due to the unique anchor method of the Fourth Nanjing Yangtze River Bridge, there are adjusting planes for one or the overall anchor cable force, and these adjusting plans are also analyzed.Third, the thesis study the influence on anchor cable force caused by following factors: choice of the value of bending rigidity of the cable, anchor beam constraint, temperature effect, thickness error of anchor plate, bridcaging phenomenon, and the interaction between the vibration frequency and cable force when one anchor beam anchors multiple cables. Adjusting plans for each factor will be proposed in this thesis.From the theoretical calculation and actual measurement results of the project, it is proved in this thesis that the anchor cable force testing and calculating method adopted in the thesis has good effect, and the results of this research can be a reference of precise control of the anchor beam cable force...