Research On Alignment Evolution And Control Method Of Long-span Track Concrete Cable-Stayed Bridge

With the vigorous development of urban rail transit,the application of long-span track bridges becomes more and more widespread.For the long-span track concrete cablestayed bridges with the characteristics of beautiful structure,large span capacity and strong adaptability,it become the main and favorable bridge type.Compared with the highway and railway bridges,the width of the track bridge is narrower with the higher requirement of the vibration and the deformation.Moreover,they also have the characteristics of large traffic volume,high operating frequency,strong load action and obvious structural response.In addition,the bridge alignment and the operational performance requirements are extremely strictly required.Therefore,the evolution and the control of the alignment for the long-span track concrete cable-stayed bridges are highly demanded,which becomes the hot and difficult issue in engineering and academia.At present,the alignment evolution of concrete cable-stayed bridges remains unclear,and there are no effective theoretical and technological supports for the alignment control of long-span track concrete cable-stayed bridges in operation stage.This paper was funded by the National Outstanding Youth Science Foundation Project.The research status and the existing problems were proposed,including the alignment evolution,the pre-arch design of cable-stayed bridge and alignment control based on operational performance analysis.Based on the existing problems,the theoretical analysis,the model experiment,the numerical simulation and the bridge verification were conducted.Based on the theory of alignment evolution and control method of track concrete cable-stayed bridge,the analysis with the material physical parameters and environmental factors were carried out.The alignment control method based on pre-arch design analysis was proposed for the alignment design stage.Furthermore,the method based on operational performance analysis was proposed for the operational stage,and the classification control limit values of the permanent deformation were obtained.In this paper,the main research contents and results are as follows:Firstly,the influencing factors of alignment of long-span concrete cable-stayed bridge were defined.The mechanism of typical influencing factors and the analysis method of their influence on the alignment of bridge structures were analyzed.It could elaborate the theoretical research on the alignment evolution analysis.According to the D’ Alembert principle and the stationary value principle of dynamic potential energy,the motion equations of the train and the bridge were established.According to the geometric displacement relationship at wheel-rail contact and wheel-rail interaction force,the motion equation by the train-bridge interaction analysis was obtained.The suitable line spectrum was used to simulate track irregularity,and the vehicle-bridge coupling vibration analysis was carried out.Based on the regulations of some operational performance evaluation indexes at home and abroad,such as vertical acceleration,transverse acceleration,Sperling index,derailment coefficient,wheel load reduction rate and wheel pair transverse force,the control limits of operational comfort and safety of long-span concrete cable-stayed bridge were clarified.And the theoretical basis of the alignment control method was built.Secondly,the material test,the large segment model test and the environmental factor test were carried out.The characteristics and the prediction mode analysis of the concrete shrinkage and creep by the environmental factors test in service of bridges were conducted.The numerical simulation analysis model was established.The structural stiffness theoretical analysis was completed,and the alignment evolution law of shrinkage and creep by different prediction models was analogized.The uniform design method was used for test sampling and the partial least squares method was used for response analysis.The R2 test was also used for model accuracy test.The evolution analysis of alignment under the confidence level of long-span track concrete cable-stayed bridge could be obtained by Monte Carlo sampling method.It clarified that the alignment evolution analysis should be partial considering the random effects of material and environmental factors and other parameters.According to the prediction model of concrete shrinkage and creep and the calculation model of multi-point elastic support structure,the calculation formulas of vertical deformation in the long-span track concrete cable-stayed bridge were deduced.Thirdly,the pre-arch design method of long-span track concrete cable-stayed bridge was proposed.The sensitivity analysis of the pre-arch design parameters was carried out,and the sensitivity characteristics of parameters were clarified.The reasonable setting of pre-camber under static and live load was analyzed.That was to say,the appropriate reduction coefficient of static loading displacement R was obtained by the analysis of vehicle-bridge coupling vibration.The setting steps of pre-arch for long-span track bridges considering the reasonable reduction of static and live loads were put forward.The alignment control method based on the design of pre-arch was proposed.Moreover,the correctness of the pre-arch design method was verified by the analysis of train comfort and the structure performance in the real engineering.Finally,the classification mode of structural stiffness envelope analysis for longspan track concrete cable-stayed bridge was put forward.By using the time-varying effect change rate index of the alignment parameters,the time-varying analysis of main girder alignment of long-span track concrete cable-stayed bridge in three-year operation period after completion was carried out.Moreover,the comparison of the alignment monitoring analysis,the numerical simulation analysis and the statistical analysis was also completed.The reliability and the accuracy of the prediction model of concrete shrinkage and creep,and the predicted results by the MC-RSM(Monte Carlo based on the response surface)uncertainty analysis method based on response surface were verified.The permanent deformation mechanism of long-span track concrete cable-stayed bridges was analyzed.The effects of the permanent deformation on the bridge structure and operation performance were also analyzed.The safety control value L/400 and the early warning control value L/500 of the maximum vertical deformation in operation stage were deduced by means of vehicle-bridge coupled vibration analysis technology.Then,the grading control limited values of permanent deformation based on operation performance analysis were proposed.That was to say,the safety control value of permanent deformation was L/400-β and the early warning control value was L/500-β,where β was the non-permanent deformation value.Thus,the rationality of the permanent deformation grading control limit based on operation performance analysis was verified by the application analysis.