| Concrete-Filled Steel Tubular arch bridge is one of the ideal forms for long-span arch bridge, and it's also a newly developed bridge engineering technology of our country. It can preferably solve many problems in bridge construction, for instance: material economization, simple and convenient construction, high bearing capacity etc. But with the bridge span increasing, the first technical problem we encounter is the matter of construction. Limited by the weight of erecting section, the number of the sections has to be increased, so a new question is brought forward to erection: how to ensure arch rib satisfying the precision required by design after final closure in multi-section erecting process. Because of the bearing peculiarity of the arch bridge, in case the arch rib is completely joined, the alignment of the rib can not be adjusted here from. However, the joined alignment of arch rib shall determine the stress of the completive bridge, so alignment control during rib erecting must be attached importance to in order to ensure the final arch axis tallying with the designed axis and bearing state of the arch bridge being most reasonable.Steel arch bridge structure embodies complex types and a legion of influencing factors, and in the meantime we frequently face the problems of parameter optimization in design calculation, construction process simulation and back analysis etc. Great advantage will be gained when the method of nonlinear programming is exercised. Aiming at the special cable-stay system of Zhijinghe Bridge, optimum theory is import in advancing calculation method and iterative optimization method is introduced into alignment control and cable-force calculation of erection stage. Via reasonable design variable, constraints and optimization function set up, the relationship between measure-controllable variables of the structure and control objective is established. With appliance of the idea of once-tension and precambers control, cable force optimization is separated into parts that performed in every construction stage, and alignment differences are modified and exterior loops are performed to ensure the alignment control. Using this method in simulation of arch bridge erection, after taking nonlinear effect like droop of cable etc into account, precambers and the cable forces ascertained in the first round optimization can basically meet the demand of alignment control. In order to overcome the limitations of this method that hard to refine the internal force of the arch rib as well as possibly too large precambers, taking notice of the influence on alignment and internal force of the rib by procedure differences of cable-removing before and after the closure, modified cable-removing schemes are brought forward which are analyzed and compared with each other, and then a best scheme with easier control is determined.On the other hand, stability has also been a restriction to the development of CFST arch bridge. CFST makes the arch rib lightweight and high-strength, but at one time it decreases the stiffness of the rib, causing stability problem more and more prominent. It has been indicated by experience that, in many cases, the stability of the bridge under construction is lower than that after construction, so the overall stability analysis during construction process should be affirmed and evaluated through scientific calculation. This point is particularly important in the conditions of long cantilever and construction period of Zhijinghe Bridge. Based on the static analysis, linear and nonlinear stability theories are applied. Aiming at the special bearing state of cantilever-closure phase, detailed calculation and analysis for stability of the Zhijinghe Bridge during erecting period are carried out including linear buckling analysis, geometrical, material and double nonlinear analysis. Original disfigurement, wind loading as well as the effect of non-oriented conservative loading of the cable is considered, and some practical conclusions are advanced in the end. |
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