Long-Span Prestressed Concrete Cable-stayed Bridge With Low Tower Construction Control Analysis

As a more competitive bridge type in bridge construction,the low-tower cable-stayed bridge has integrated the advantages of continuous rigid frame bridges and cable-stayed bridges since its birth,while at the same time abandoning the shortcomings of both,making its construction method suitable.It has its own unique characteristics,that is,during the construction of the low-tower cable-stayed bridge,there are not only the construction of the T structure without the cable area,but also the tensioning work of the cable-stayed cables with the cable area,which makes the linear control difficult in the construction process.Such as changes in the monitoring plan during the construction process,modification of influencing parameters,changes in construction period,changes in closure methods,etc.The degree of impact on the alignment is not yet clear,and how to deal with the above problems needs further research.For these reasons,this paper studies the above-mentioned difficult problems based on the existing research on the construction control of low-tower cable-stayed bridges,and combined with the problems faced in the project construction.According to the current specifications,the project engineering MIDAS finite element model is established.First,the stress,cable force and deformation of the structure under the ideal state is analysed,and the preliminary monitoring theory database is established.In view of the possible construction and target alignment changes that may occur in the monitoring process,the two types of monitoring program changes that have a greater impact on the pre-camber setting,analyze the impact of the two on the pre-camber,and propose a reasonable solution.The monitoring results encountered during the specific construction process are very different and the parameters are revised.The sensitivity analysis of the parameters of the low-tower cable-stayed bridge is carried out,in view of the problem of the extension of the construction period faced in the construction of the long-span bridge.The effect of shrinkage and creep on the cable stay of the low tower is first analyzed.The influence of the operation deflection of the tower cable-stayed bridge is studied.O n this basis,the influence of the change of the construction period of the section and the delay of the construction period on the deflection is studied;in view of the problem of closure method faced in the suspension cast structure,the influence of hanger closing and hanging basket closing on structural alignment is analyzed and put forward a solution to the height difference problem caused by the closing of the hanging basket.The research results show that the change of the construction sequence has an impact on the pre-camber of the cast beam section within 1cm,and the pre-camber of the new scheme can be directly used for the construction control of the subsequent section.The target linear change affects the pre-camber of the cast beam section and it is not appropriate to use the method of directly invoking the new pre-camber.Instead,to make the structure transition,the pre-camber of multiple segments should be adjusted from the pre-camber of the original scheme to the pre-camber of the new scheme.It can be applied during the parameter adjustment when Ridge regression analysis is used to predict the parameters,and the results are more stable than traditional regression analysis.The construction period has no significant impact on the deflection of the main girder section,but has a greater impact on the deflection and operating deflection of the bridge.It can be set up by setting reasonable pre-arch and erecting model elevations.To reduce the impact of changes in the construction period on the alignment of the bridge,the two closing methods of hanger closing and hanging basket closing will cause different pre-camber settings.If the closing method is adjusted suddenly during the construction process,the adjustment of the elevation of the section erection should be studied in time.In order to make the line shape smooth,and when using a single-sided hanging basket to close the dragon,special attention must be paid to the height difference of the closing mouth,which can be effectively solved by setting additional counterweights.