Prediction About Long-Term Deflection Of Long-Span Prestressed Concrete Continuous Rigid Frame Bridge On Highway

Recently, the continuous and excessive mid-span deflection generally occurs in large-span prestressed concrete continuous rigid frame bridges. It has already increasingly threatened the riding comfort and bridge safety. Therefore, how to overcome the problem of excessive deflection has become a subject urgent to be solved in similar engineering.Domestic and overseas related researches show that the material features randomness of concrete is the main cause of the excessive long-term mid-span deformation. This randomness results in a large difference between the actual deflection during its service stage and the one derived with a deterministic method. It is necessary to study on this problem with stochastic analysis method.Therefore, in this dissertation a research was carried out on the prediction of the long-term deflection with an engineering example of a prestressed concrete continuous rigid frame bridge. A stochastic analysis method was adopted based on the deterministic analysis. And the most influential random variables on the girder’s mid-span long-term deflection were considered during the research. The main contents of this dissertation are as follows:(1) A brief summarization of development history and research results about study on long-term deflection for long-span prestressed concrete box girder bridge was presented. Then several main domestic and overseas theoretical models of creep and shirinkage of concrete were summarized. The combination of response surface method and Monte Carlo method was applied to stochastic analysis for the long-term deflection was introduced, combined with the concrete’s creep and shirinkage mechanism and their influencing factors. This provided a simple and effective method for the following calculation analysis.(2) A deterministic simulation analysis of a certain prestressed concrete box girder bridge on highway was studied based on the related literature. Through a simulation analysis on construction control of this prestressed concrete box girder bridge, a research was carried out on the change law of internal force, deflection and stress in process.(3) In this dissertation, a computational framework derived from Bayesian theory about long-term deflection of concrete structures was proposed, in which importance sampling technology and response surface method were involved to improve the stability and efficiency of computation. The predictive uncertainty can be reduced significantly through step-by-step scheme repeated several times. Meanwhile, with different models of concrete’s creep and shrinkage considered respectively in numerical example, the applicability of the computational method can be verified.