Analysis On The Sensitivity Of Prestressed Concrete Cable-stayed Bridge Construction Control Factors

Three parts about construction control of prestressed concrete cable-stayed bridge are included in this thesis: First,the analysis of construction sensitivity parameters for the girder alignment,cable force,girder internal force and bridge tower deviation.Second,the temperature affection for the bridge tower deviation,girder alignment and cable force.Third,the parameters identification and amendment based on BP neural network.The study background bases on a prestressed concrete cable-stayed bridge under construction,this bridge use the balanced cantilever construction method,the form of the girder is ? style,the initial force of cable is almost 60 percent of the designed force and all the cables adopt second force adjustment project.The purpose of the thesis is to study the law of sensitivity parameters influence to the construction control indicators and the corresponding construction control methods of prestressed concrete cable-stayed bridge.First,The finete element model of prestressed concrete cable-stayed bridge is set up according to the real construction stages of it by using the midas finite element calculation software.In terms of construction parameter sensitivity analysis,eight factors such as the weight of girder,concrete shrinkage and creep,the elasticity modulus of concrete,the elasticity modulus of cable,the weight of cable,the initial force of cable,the adjusted force of cable and the construction load(weight of the form traveler)are chosen.Through the calculation of whole construction stages by changing the value of those factors based on their designd value,the influence of the girder alignment,cable force,girder internal force and bridge tower deviation are studied.Then the thesis studies the law of how the weight of every single girder affects the girder alignment during the balanced cantilever construction and analyzes the limiting value of every girder which should be controled.Ather the analysis of construction sensitivity parameters finished,the thesis analyzes the temperature effects of the bridge.Study is carried out from the following parameters,such as the affection of whole rising and falling environment temperature and the temperature difference between concrete tower,girder and cable to the alignment of the concrete girder,the force of cable,the devition of tower at the state when the bridge construction is finished and the affection to the alignment of the concrete girder at cantilever construction stage,then study the methods of construction factors amendment based on the analysis results.After the whole analysis of sensitivity parameters,the normalization methods are used to identify the parameters which may remarkably affcet the calculation results of bridge behaviour,are determined by parameter sensitivity analysis and identified by neural network technology.The application of the BP neural network method in the construction control of prestressed concrete cable-stayed bridge is explored.First,by analyzing the bridge,using the nonlinear analysis system-Midas,samples of learn?train and test are obtained.Then a identification model of construction control is established based on BP neural network.A parameter identification program is designed by using Matlab programming language.At last,the results of parameters identifiction are compared with the real value of the parameters,and the BP neural network is optimized according the results.Then the construction parameters of the next construction stage is revised by using the optimized neural network which combines the construction measure data.Through the study results of this thesis,we can come to the following conclusions:First,to the construction precision,the weight of girder,the force of cable and the variation of environment temperature are the major sensitivity parameters.Although other parameters can also affect the construction but influence degree is not obvious.BP neural network has a good application in the parameters identifiction,but it need to be optimized based on the specific construction condition to get to the ideal performance.