Research On The Construction Monitoring Of Jundushan Cable-stayed Adueduct

Some cable-stayed aqueducts operating for many years faced a number of problems: cable wire corrosion and fatigue,anchor loose,concrete shrinkage and creep,bearing in settling bit,and many other issues.When the internal force or the alignment of the cable-stayed aqueduct is unreasonable,it can be improved by adjusting the cable force.The main research target of this paper is how to acquaintance the exact distribution of cable force before cable replacement and further optimize the cable force distribution and alignment through adjusting the cable force after the cable replacement.Based on the cable replacement project of Beijing Jundushan Cable-Stayed Aqueduct,this paper draws on the former research on the cable replacement project of the cable-stayed bridge to carry out the following work:(1)A method for identifying parameters of old cables through genetic algorithm is proposed.The bending stiffness and mass density of cables can not be identified by the traditional method when the cable forces are detected by the vibration frequency method because of the damage of the old cables themselves,and the genetic algorithm can effectively solve this problem.Through the genetic algorithm GA program which was written in Fortran language,the feasibility of this method is verified by comparing the tension of old cable identified by genetic algorithm and the original designed cable force,and the causes of errors in these results are also analyzed in this paper.(2)It is judged whether the structure is safe during the cable replacement.By establishing the finite element analysis model of cable-stayed aqueduct,the stress and the alignment change of the aqueduct under the most unfavorable load is extracted,the influence of aqueduct during the operation in half tank water is used to conclud that both the structural stress and the alignment change are within the safe range in the process of cable replacement.(3)The elevation data of aqueduct surface obtained by monitoring are analyzed,the cause of the error between the alignment of aqueduct surface after the replacement of cables and the theoretical alignment of the aqueduct surface which is calculated from the analysis model is given,and from which a conclusion can be drawn that the second adjustment of cable force is needed to adjust the alignment.(4)The neural network and genetic algorithm is applied to design the cable adjustment scheme.Firstly,the influence matrix method which is frequently used in the scheme design of cable adjustment is applied in this paper,since the influence matrix method has some problems in practical application,the process of searching the optimal solution by the influence matrix method is improved.Secondly,a new design method of cable adjustment scheme is proposed,which establishes the mapping relationship between the increment of the cable force and the elevation change value through neural network training,and calls the mapping relation of neural network training by genetic algorithm program to find the optimum solution.Based on the sum of squared errors between the elevation change value and the target elevation change value,and the calculated sum of squared errors between the elevation change value and the actual elevation change value in the two optimal scheme,these two design scheme are evaluate,and the feasibility of the application of neural network and genetic algorithm in the design of cable adjusting scheme is confirmed.Meanwhile,this method has the advantages of meeting the design requirements and the accuracy of the results compared with the influence matrix method,which can be used in future.