Study On Cantilever Construction Control Of Long Span Prestressed Concrete Continuous Girder Bridges

With the rapid development of communication, prestressed concrete continuous girder bridge has grown up to one of the primary bridges with its predominance of riding comfort and long span, and cantilever construction has already became the main method in long span bridge construction. To the cantilever casting bridge, in order to ensure not only the joining accuracy of the structural and the alignment of the finished bridge, but also the final elevation meeting the design requirement after a period of operation, it is very important to forecast the deflection of superstructure at every construction stage and analysis the construction behavior based on the real-time monitoring values.Based on the construction control of Zhugenhe Bridge and according the characteristic of the cantilever construction continuous girder beam, some analysis and contrast for the construction control methods have been presented in the paper and the adaptive control approach has been selected in the construction control of Zhugenhe continuous Bridge.According to the requirement in designing and construction feature, Simulation Analysis to the construction phase have been done with Finite Element Method so as to figure out the internal force and deflection in each cantilever casting phase., and then the errors have been analyzed by comparing to the measured data during the construction, then the next time formwork elevation could be adjusted, thus the results could be applied to the construction control of Zhugenhe Bridge.Because there are many factors which make the construction state different to the design state, sensitivity analysis of parameters which will affect the alignment of the main beam has been investigated in this project. Through the calculation of the last cantilever phase as well as the whole bridge closed phase, it can be known that during the construction phase the main parameters that will affect the alignment of the beam are prestressing force, concrete volume-weight and concrete elastic modulus, and the influence of concrete creep is not apparent within short time, but the long time effects of concrete creep to the alignment of the beam can not be ignored. It is already known that for the prestressed concrete continuous beam during the cantilever casting phase, if errors appear in finished section , there is almost no way to eliminate it, then the forecast of the state of next section is of great importance. In this paper, grey control theory which can be used to estimate and forecast structure state has been described in detail and applied into the construction control of bridge. According to the results, it is proved that it is feasible to use grey theory to forecast structure state. Meanwhile, least square theory which can be used to estimate structure parameter and the way how to be applied in the bridge engineering has also been described in this paper. Applying the two theories to the construction control of Zhugenhe bridge, Combining they, adaptive control system could be formed when integrating the construction measure and structure calculate and error adjust.