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Study on Application of Ballstless Track Twice-prestressed Concrete Composite Beam

Author: NieMeiChun
Tutor: ShaoXuDong
School: Hunan University
Course: Bridge and Tunnel Engineering
Keywords: twice-prestressed crack load connection surface shear resistance
CLC: U213.244
Type: Master's thesis
Year: 2009
Downloads: 37
Quote: 0
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Abstract

Based on the research work made by formers, further study was performed on twice-prestressed concrete composite beam in this paper. The research carried out by this paper is part of the work "Research on basic properties of twice-prestressed concrete composite beam and its application in high-speed railway bridges" supported by the National Natural Science Foundation of China. This paper introduced the research on the basic properties of this new type structure. Shear-resistant ability of connection surface in this beam is one of the most important. Because the concrete of twice-prestressed concrete composite beam is cast in two stages, the shear-resistant ability is much lower than that of beam cast in one time. The main contents of this article are:Firstly, a test beam was fabricated with reference to normal prestressed concrete beams in high-speed railway. For the convenience of research, some simplified work has been performed. The double-line beam was changed to single-line, unsymmetrical to symmetrical with same area moment of inertia and main size unchanged. The reinforcement arrangement remained unchanged, but the ratio of reinforcement of connection surface was decided by experiment. The strand’s type and position are same as the model beam.Secondly, a study on the shear-resistant ability of connection surface in twice-prestressed concrete composite beam was made from static aspect. Some test samples were fabricated to research the shear force of connection surface. In the experiment, special attention was paid to the factors which influence the shear-resistant properties of connection surface: concrete age difference, the ratio of reinforcement and stress difference in connection surface. The test results show that the ratio of reinforcement and concrete age difference are the main factors. With reference to test data, an empirical formula was derived based on the test data from experiment. And the author discussed the scope of application of this formula. This work would help later design of this beam and provide some reference.Thirdly, the author performs study on the shear-resistant ability of connection surface in twice-prestressed concrete beam from dynamic aspect. It was found the fatigue crack of twice-prestressed concrete composite beam is same as the steel-concrete composite beam. On the condition of good quality of construction, the ratio of shear reinforcement of connection surface is one of the main factors to influence the fatigue property of twice-prestressed concrete composite beam. The crack load has much relation with the ratio of shear reinforcement. At the mean time, the difference in concrete age is also one of the important factors influencing the crack load.In all, this paper performed much work on the design of twice-prestressed concrete beam and the shear-resistant ability of connection surface from static and dynamic aspect, providing much reference and experience for later design of this structure.

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