| There are a large number of prestresse concrete cable-stayed bridges in present China which have been completed or are being constructed.construction control is one of key technologies in its design and construction,which guarantees the security of constructing Structures and the curve of the stiffening girders so as to meet the requirement for the completed bridge.therefor it is very neeessary and valuable to research the construction control analysis of long-span P.C.cable-stayed bridges.Firstly, the control theory and methods for the cable-stayed bridges introduced briefly. and then the error of bridges construction analysized.design parameters as the main parameters must be identified, the main parameters is obtained through the parameter sensitivity analysis.on this basis,by using Kalman filter and leasting square method to predict the fllowing construction phase.Secondly,a variety of cable tension optimization theory and methods are introduced in detail. and summarizes the practical cable force optimization method which is frequently used in preliminary design stage of cable-stayed bridge. In this article, the optimizing cable force are caulculated by using rigid support continuous beam and the object to minimizing bending energy of influence matrix methods respectively, finally the reasonable finished cable force is obtained through the adjusted cable force of influence matrix methods.Finally,combined with Fujiang 4th bridge construction characteristics, the structure engineering software of MIDAS/Civil was used to set up the construction model.then adopted the backward analysis-forward iteration method to determine reasonable construction cable force,as well as the internal force and stress of tower and beam in every construction stages. in the end,the thesis research the stabilities of the most dangerous construction phase (the longest cantilever state) and finished sate.through the analysis, the different modes of instability form are obtained.
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