Study On Mechanical Characteristics And Construction Control Of Dismantled Concrete Box Girder Bridge

With the rapid development of society,some bridges built in the early stage can no longer meet the current traffic demand due to the low capacity and damage caused by long-term service,so it is necessary to demolish and renovate them.Therefore,it is of great practical significance to study and analyze the construction control and structural stress characteristics of bridge demolition.This paper takes the demolition of prestressed concrete continuous box girder bridge as the research object,and mainly carries out the following research contents:First of all,the reasons and influencing factors of bridge demolition are summarized based on the main bridge demolition project of Xuzhou 310 National Road in combination with the bridge demolition research status.Secondly,with the structure characteristics of the prestressed concrete continuous box girder bridge construction control related theory as the foundation,and combining with the demolition construction scheme of the main bridge of Xuzhou 310 National Road,and starting from the construction control of the bridge demolition,the stress、linear and stress state of the main girder and the support in the process of bridge demolition are monitored in real time.Then,the finite element software Midas Civil was used to simulate the construction process of main girder structure demolition,the field measured values of the main bridge in each construction stage are compared with the theoretical values calculated by the model.After comparative analysis,two construction stages in which the structure system of the main girder is transformed are selected: the demolition stage of the middle span closure section and the demolition stageof the side span closure section,the stress and linear changes of the main girderin these two construction stages are discussed respectively.The results show thatafter the closure section of the middle span is removed,the cantilever end of the middle span of the main girder has a large amount of downflexion,and the downflexion increases gradually with the approach to the middle span;After the c-losure section of the side span is removed,the middle span of the main girder is flexed upward and the side span is flexed downward,and the linear change value increases gradually from 0# block to the middle span direction of both sides.Finally,based on the study of the mechanical characteristics of the main girder structure,the mechanical analysis of the two side span load-bearing support structure of the main girder is further carried out,combined with the finite element model of the joint system of the main girder and support,the field measured values are compared with the theoretical calculated values.The research shows that with the change of the construction stage,the stress variation trend of steel tube pile and beam of the support structure is basically the same,and the load transfer of the support structure is normal,the strength、stiffness and stability of each row of brackets meet the requirements of carrying capacity when they are in the maximum stress state.