拉索索力增量校验系数检定方法研究

Cable structures are more and more widely used in railway bridges, however there is no rating requirement for the cable structures in the current code for rating existing railway bridges yet. Most of the rating methods are based on were based on the adjustment factor for the cable force or frequency in the existing bridge standards or theories, while few of them are paid attention to the studies or requirements about the cable force increment adjustment factor were carried out in current literatures or specifications. In addition, further study and validation should be firmly confirmed on how to reasonably select the cable length and how to determine the finite element model for the theoretical calculation of cable force in calculating the adjustment coefficient. Based on the above, the rating method of cable force increment adjustment coefficient was proposed, and the reasonable calculation method of cable length and theoretical calculation model for cable force were determined by the comparison of case study. The cable force calculation formula under different boundary conditions was accurately derived based on the string theory and energy method, and the simplified calculation model of cable force loaded was suggested considering vibration frequency ratio, and the increment adjustment factor of cable force was derived on the basis of the simplified model. Experimental cases demonstrated that the results by the accurate methods of cable force is in good agreement with the result of finite element calculation and the simplified method. By comparing with the cable force, the cable force variation and the basic frequency, the cable length should be reasonably selected for the measured cable force calculation during the transition from the measured frequency to the cable force. The theoretical cable force can be determined according to the finite element model of overall bridge, and the vibration frequency of the cable can be determined according to the local cable model equivalent to the cable force of the finite element model of overall bridge. Compared with the adjustment coefficient of vibration frequency, cable force deviation rate and cable force adjustment factor, the increment adjustment factor of cable force can remarkably reflect the variation amplitude of the cable force and evaluate the technical status of cable structure, which can be used as the rating standard of cable structures and suitable for evaluating the medium length hangers with the bending stiffness affecting parameterμ>80.