Research On Construction Monitoring Control And Closure Sequence Of Four Span Continuous Girder Bridge

Prestressed concrete continuous girder bridge is widely used because of its many advantages,but in the construction stage and operation process,there are some problems such as cracks and deflection of girder bridges.In order to ensure the safety and healthy operation of bridge construction,bridge construction monitoring is particularly important.Although there are many studies on construction control and closure schemes optimization analysis of prestressed concrete continuous girder bridges,most of them focus on odd-span continuous girder bridges,few studies on construction monitoring technology of even-span continuous girder bridges.Construction monitoring and closure characteristics of even-span continuous girder bridge are different from odd-span continuous girder bridge,there are also various problems.Therefore,it is necessary to study construction monitoring and closure scheme of even-span continuous girder bridge more deeply.In this paper,based on the(45+75+75+45)m four span continuous girder bridge of Nantong Changjiang North Road,it firstly introduces the main work contents and implementation methods of cantilever casting construction monitoring of continuous girder bridge,and at the same time introduces the data acquisition of box girder deformation and the method of formwork elevation processing.Stress test data and processing methods are analyzed in detail.The finite element analysis model of the bridge is established by using Midas/Civil software and Dr.Bridge software.The comparison of the theoretical calculation results of the two software shows that the deformation and stress calculation results of the girder bridge are consistent with each other,which guarantees the reliability and accuracy of the finite element model calculation results to a certain extent.The results of finite element model also provide a theoretical basis for bridge construction monitoring.At the same time,the method of calculating and setting the camber value of the girder bridge is introduced.By setting the camber,the erection formwork of the girder bridge is guided to ensure that the alignment of the bridge after completion meets the design requirements.On the basis of considering the age difference between the two sides of the cantilever,five different closure schemes are worked out.By using Midas/Civil software,the influence of different closure schemes on the bridge structure is analyzed from three aspects of structural stress,internal force and deflection change.At the same time,the construction cost,construction period,construction organization and other factors are taken into account to determine the optimal closure scheme.For this bridge,from the structural alignment,stress and internal force point of view,the fourth scheme is the best one.However,due to the delay of 60 days in the construction of the middle pier KA33,considering the construction period,construction organization and other aspects,the closure scheme 1 is finally determined as the best one.That is,after the cantilever section of the two side piers is completed,the side span closure is carried out before the cantilever section of the middle pier is completed,and then the middle span closure is carried out.After the completion of the bridge,the overall alignment of the main girder is gentle,the force is reasonable,which meets the design requirements.At the same time,the construction period is shortened and the economic benefit is improved.According to the proposed construction monitoring scheme,the whole process of the bridge construction monitoring is implemented.Through the construction monitoring,the main girder alignment is well controlled,the control section stress is in good agreement with the measured value,and the bridge is in a controlled and safe state.By adopting the construction monitoring and closure scheme developed in this paper,the stress and deformation of the bridge in the construction and operation stages can be guaranteed to be more reasonable,which can provide reference for the construction monitoring of similar bridges.