The Time-dependent Analysis On The Mechanical Properties Of Precast Prestressed Bridge Girders Made Continuous

As precast prestressed bridge girders made continuous has good mechanical properties and better ride quality,the kind of structure is widely used in the construction of highway.When the precast girder is erected in place,the bridge is statically determinate structure,after the joints are casted,it becomes redundant structure.With the time development,the mechanical properties,especially,the support moment keeps changing under the influence of concrete creep.The long-term mechanical behavior of the structure has been the one of the focus of engineering and researchers.This thesis surveys a large number of domestic and foreign literatures,the author know well with the state of the art in this research field.First,in this paper,the basic theory of structural analysis of this kind of bridge is introduced,and the regular pattern of the support restraint moment caused by creep and shrinkage is analyzed.A four-span bridge,as an example project,is studied using the finite element method,and the model is established by MIDAS/Civil software.The results show that the main girder deflection becomes greater under the influence of creep and shrinkage.The length of the prestressing tendon in the region of diaphragms also has a significantly influence on the structural time-dependent behavior.In this paper,a compute program is conducted using FORTRAN to analyze the time-dependent behavior of the precast prestressed bridge girders made continuous,a time-step method is used to analyze the influence of the creep and shrinkage.By adjusting the parameters,an analysis on the change of the support restraint moment is fulfilled.The study results show that the transfer time has a main influence on the support restraint moment.If transferring at early age,the camber and support restrict moment become greater.If transferring at late age,the restraint moment becomes greater and it becomes smaller after several months.