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

With the rapid development of China's highway and railway, more long span bridges were needed to span great rivers and bays. PC continuous beam bridge emerged as required and has been developed fleetly in recent years. There are a few the construction methods of the PC continuous beam bridge. Among these methods, cantilever installation and cantilever casting have been used widely. This construction method results in the complex change of the internal forces and displacements in the bridge. For ensuring the quality and safety of the construction, the construction control is indispensable.Through the analysis and summary of the development of continuous beam and the developmental tendency of the construction control techniques in our country and abroad, the paper gives the study of the construction control techniques for long-span pre-stressing concrete continuous beam bridge.Based on the construction control of Niushifan 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 dissertation and the adaptive control approach has been selected in the construction control of Niushifan 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 Niushifan 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 dissertation, 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.