Research On Theory Of Concrete Beam Bridge’s Damage Based On Deformation

Based on deformation, this thesis conducts research on the theory of concrete beam bridge’s damage. The theory of concrete bridge’s cracking is studied from the perspective of concrete bridge’s deformation caused by structural damage. The main contents include the following:Ⅰ. Deformation characteristics are researched under the first load, repeated load and sustained load respectively. Effects on the deformation capacity of concrete are researched when the cross section is on strain gradient. It is proposed that the expansion of micro cracks of the concrete is the internal cause of concrete damage under various circumstances. The factors occurring in strain state are proposed when establish the strength failure criterion based on the strain.Ⅱ. According to surveys of vehicle load and damage principle of fatigue equivalence, fatigue load model of vehicle which is suitable for bridges on expressways in the city is established. The fatigue cumulative damage strain of the Ministry of Transportation25m standard span prestressed concrete T-beam bridges under fatigue loading is researched according to the vehicle model. This model can provide bases for the fatigue design of bridges on the express ways, and it is of great reference value.Ⅲ. Damage strain of creep and damage degree of creep are proposed and an in-depth study of the theory of concrete creep. With the help of present research, and taking the characteristics of creep deformation and crack expansion of concrete under various sustain loads into consideration, a simplified formula of Damage strain of creep and damage degree of creep is proposed.Ⅳ. Relying on the experiment of the effects of shrinkage and creep on the continuous beam arch bridges on Beijing-Shanghai high-speed railway, research on the shrinkage of core concrete of concrete filled steel tubular and plain concrete specimen is done, and conclusion that drying shrinkage is the decisive factor of concrete shrinkage size is obtained. Damage strain of concrete in non-uniform shrinkage field and under gradient temperature is researched, and taking one-dimensional temperature field and shrinkage field as an example, a formula of concrete damage strain is conducted. The effects of concrete wet coupling are studied, and presentation on the linear coupling theory and the theory of nonlinear coupling is made.Ⅴ. An in-depth research is made on the strain forms of the concrete under various stress states, including uniaxial stress, biaxial stress and triaxial stress. According to theoretical analysis and the measured data of ultimate compressive strain of compression-based concrete, effective factors of ultimate compressive strain of compression-based concrete are researched. The relationship between strain status and relative ultimate compressive strain of concrete under damage is explored, and Matlab procedure programmed, and finally a secondary inverse proportion equation that can better reflect the relationship between strain status and relative ultimate compressive strain of concrete under damage is introduced. Refer to strain curve of concrete under uniaxial compression, the existed strength failure criterion based on strain space, and the characteristics of cracking expansion of concrete under uniaxial compression, an interface equation of concrete strength failure criterion based on strain is proposed. Taking the vice bridge of GuangdongYajisha86m+160m+86m continuous rigid frame bridge as an example, the applicability of a failure criterion based on the strength of the strain is tested.