Experiment Research For Cable-Girder Anchorage Structure Of Long Span Steel Cable-Stayed Bridges

With the development of long-span cable-stayed bridge, the cable-girder anchorage structure of the bridge is put forward a higher request. The cable-girder anchorage zones of cable-stayed bridges which bear giant cable forces and have complicated structure, are keys to structure design. It is very important to know the strength and fatigue property of the cable-girder anchorage structure. Several typical models of cable-girder anchorage for long-span cable-stayed bridges with steel box girder, such as anchor-box, auricular anchor plate, anchor-pipe, tensile anchor plate, are described in this thesis. Under the background of Anqing Yangtze River Bridge and Suzhou-nantong Yangtze River Bridge, full scale static load model test and fatigue test of the cable-girder anchorage zone have been carried out. Based on the model tests, large quantity of imitate calculations and theoretical analysis for the correlative problems have been done. The content of this dissertation is as follows:1. A few of tests and thesis reasech about the cable-girder anchorage structure have been described, the force transmission route, stress distribution and stress concentration under the condition of dead load to cable-girder anchorage structure have been studied, and some beneficial results are obtained.2. To study the cable-girder anchorage for long-span cable-stayed bridge, 3D nonlinear finite element models have been established by different methods. The results of model tests are compared with 3D finite element analysis. And the comparison shows the reliability of the method which solid element with nonlinear contact element simulating the state that the anchorage frame and the setting plate are not welded together but only pressed closely to each other.3. With the limitation of practical software and hardware, only the local-zone model can be adopted to analyze in 3D nonlinear analysis and model test to steel-anchor-box at the cable-girder anchorage zone for long-span cable-stayed bridge. And the results of analysis are influenced by the finite-element models' size and boundary condition. The results of model tests are compared with 3D finite element analysis. The problems of the affection of boundary conditions to the stress in the real structure and the mechanical behavior in the cable-girder anchorage are studied. 4. To counter the situation that there is no rules about fatigue loads in China highway bridge design codes, Based on the survey of the traffic conditions of some domestic urban roads and a few of national highways, consult of the feasible traffic volume forecast for Suzhou-nantong Yangtze: River Bridge and Chinese highway construction technical standard, the fatigue load has been set up firstly, then, the variety of cable force has been calculated voider different lane load. The calculation method and formula of highway bridge fatigue loads have been given. Some abroad design codes and the theory of cumulative damage for fatigue have been used in the research.5. To avoid the accessorial structure destroyed firstly in fatigue test model for the cable-girder anchorage zone of steel cable-stayed bridges. Based on a few of former fatigue test designs for the cable-girder anchorage zone, various factors affecting the fatigue life are introduced, and structural multi-objective optimum design has been described. With the background of Suzhou-nantong Yangtze River Bridge, full scale static and fatigue model test of the cable-girder anchorage zone has been carried out. The results of model tests verified correctness of its design.6. Based on the model tests and large quantity of theoretical calculations, the quantificational description of the cable force distribution has been given in the principal welding lines of the box-shaped anchorage zone. The mechanical characteristics of the main plates and the cause of stress concentration have been studied. For further optimization design, the influences of weld length , stiffening rib and diaphragm plate for the web stresses distribution are studied and compared. Some useful principles have been disscussed, and it is beneficial to the design of bridges.