Study On Twice Pre-stressed Continuous Beam And Its Experiment

This research is based on the previous works, funded by Communication Bureau of Guangdong province. A new structure, that is the twice pre-stressed composite structure, is used for continuous prestressed concrete beam bridges in this thesis. A lot of studies are carried out on its performance and characteristic in construction, creep and service phase, from both theoretical analysis and experimental study.The idea about the twice pre-stressed composite structure is coming from the development of ultra thin beam, combining with the problems in engineering practices and other existing pre-stressed structures'characteristics. In this thesis, the primary principles and construction technology of twice pre-stressed composite structure are introduced based on the experimental study on a two-span twice-prestressed continuous beam.Then, focusing on the construction technology of twice pre-stressed continuous beam, the structure analysis methods in this phase is introduced. The structure analysis methods during construction stage are investigated form the construction properties of twice-prestressed beam. Further more, some factors, which may affect those characteristics, are full investigated, which can provide some extent help for the design and construction.Based on the linear creep theory and deformation coordination principle, the calculation method and computing formulas about the inner force redistribution and the stress redistribution are investigated in this thesis, the validity of this method is demonstrated by comparison the calculated results with the tested results. Its effect factors are investigated by numerical examples in this thesis, which can provide reference on design and research of twice-pretressed continuous beam.An experimental bridge, located at Qingyuan city, Guangzhou province, was designed based on research project as《Research on High Strength Concrete in Ultra Thin Beam Bridge》, and two-year shrinkage and creep observation has been carried out, Finally, the whole bridge check was done and then in service. Comparison theoretical and experimental research of creep based on theory of ultra thin beam, the effect results were provided for design of ultra thin beam.At last, on the basis of the summarization, several questions are put forward for further investigations in the future.