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Analysis of Creep Effect for Concrete Continuous Beam Bridge

Author: WangWei
Tutor: LiuYanHai
School: Lanzhou Jiaotong University
Course: Bridge and Tunnel Engineering
Keywords: Concrete creep effect Prestressed concrete continuous beam bridge Stress deflection Prestress loss
CLC: U441
Type: Master's thesis
Year: 2012
Downloads: 127
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Abstract

The creep of concrete is an important inherent time-dependent characteristics, and will be accompanied by time, which will run through the construction and entire term of service of the prestressed concrete continuous beam bridge and have an effect of internal force and lin-ear. Especially for the linear effect, the creep effect will make the beam body to generate ver-tical displacement, and affect the linear and beauty of bridge, even cause inestimable conse-quences. This paper focuses on analysis of stress, camber and deflection on concrete creep effect in construction process and service period, taking the two different span DaShaping prestressed concrete cross-section box girder beam bridges of as background.The main research contents of this paper are as follows:(1) The paper explains the importance of concrete creep effects on the bridge structure by introducing the use of bridge structure and the cause of engineering accidents because of concrete creep effects. At the same time, the paper introduces the research history and achievements at this stage of concrete creep effect at home and abroad.(2) This paper does a detailed explanation on the basic concept and mechanism of con-crete creep effects and a brief overview on internal and external factors of concrete creep ef-fects. And this paper introduces the several classical computational theory and creep predic-tion models in calculating concrete creep.(3) The paper introduces finite element analysis in calculating concrete creep, at the same time, this paper gives a detailed explanation on the relationship of creep strain and stress、the displacement equation of creep effect、the basic assumptions of finite element and the finite element calculation steps of concrete creep.(4) This test takes the finite element software MIDAS/Civil as the basis of theoretical analysis to establish the model、divide the construction phase and extract contrete creep coefficient, taking the two different span DaShaping prestressed concrete beam bridges as background. At the same time, the paper simply introduces the control systems of construc-tion and rules of measuring point dispatch of linear and the stress in DaShaping Bridge.(5) This paper analyses a series of changes of linear and stress of the structure for con-crete creep effects in the construction and in the operational phase of bridge, and get the dif-ference of creep prediction results for different value of individual parameters through com-paring the "public pre-regulation" with "CEB-FIP1990".The conclusions are as follows:(1) The concrete creep analysis has got some achievements, but hasn’t got fully the law of development and trend of concrete creep effects. At present the creep factors are not fully covered by recognized creep theory, which leds to a strong theory limitation. Therefore, it is still a long way to go for us to study the concrete creep effects.(2) Based on the construction stress analysis results, beam in construction is stressed, and the theory stress values include in creep effect are greater than that not include in creep effect. The measured stress values slightly change for various factors in construction, but are in the allowable stress range.(3) This paper analyses the prestressed force losses for the creep effect based on the "public pre-regulation" and "CEB-FIP1990".The theory values of "CEB-FIP1990" are less than that of "public pre-regulation", and reach the maximum value in the three years after op-eration, and decrease until being stable. In addition, the prestressed force losses caused by creep gradually increase from pier top to both sides, and reach the maximum.(4) The effect of camber leaded by the creep effect in the construction and operation cannot be ignored, and should be valued in the calculation of camber.

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