Deformation Prediction Method For Cantilever Construction Of Long-span Continuous Rigid Frame Bridge

The continuous rigid frame bridges has continuous main girder and consolidated pier girder.It has the advantages of large structural rigidity,smooth and comfortable driving,and it does not need to set up supports and is quick in construction.With the increasing number of large-span prestressed concrete bridges that adopt cantilever construction,the related theory of cantilever construction control of large-span continuous rigid frame bridges has received increasing attention.In order to ensure that the stress and deformation of the main girder meet the requirements of the specification during the construction of the bridge,the line type and stress control during cantilever construction is of great importance.However,the material properties(such as concrete bulk density,elastic modulus,shrinkage and creep,etc.),external environment(such as temperature,humidity,construction technology,etc.)and the uncertainty of construction observations will have a great impact on the alignment,stress and closure of the bridge.This paper aims at the characteristics of the cantilever construction of the upper structure of the long-span prestressed concrete rigid frame bridge,the alignment and stress in the cantilever construction are studied.The main research contents include:(1)By summarizing the content,methods,structural analysis methods and influencing factors of the continuous rigid frame bridge cantilever construction control technology,the on-site construction control system was established.(2)According to the construction drawings and related specifications,a(65+120+65)m continuous rigid-frame bridge finite element model was established,and the force and deflection changes of the bridge during the cantilever construction process were summarized.The effects of structural deflection and internal force,such as structural self-weight,concrete elastic modulus,prestress loss,overall temperature rise and fall of the main girder and concrete creep,are studied,and the main factors affecting the construction control of continuous rigid frame bridges are determined.(3)The manufactured sand concrete creep test used in the real bridge was carried out,and the test results were compared with the creep model recommended by the code.The CEB-FIP90 creep model was revised using the creep test data,and the creep prediction model formula of the manufactured sand concrete of the bridge was obtained.(4)The(65+120+65)m continuous rigid frame bridge construction control plan was Designed.According to the creep prediction model obtained from the experiment and the creep model of my country's current norms,Midas/Civil is used to analyze the deformation and internal force of the continuous rigid frame bridge,the results show that the calculated results of the modified creep model are more consistent with the actual values,which can improve the prediction accuracy of the bridge construction and adjust the pre-camber used for the bridge.