Study Of Concrete Fatigue Characteristic

Along with the high-speed development of our country national economy, our country has been already set up numerous highways, big bridges and airports. They developed a very important function in the national economy. Concrete beams that be used in the road engineering, big bridges and high-speed roads and concrete road noodles of the airport runway are bearing fatigue load. Increscent of the car amount and airplane's declining times will aggravate these burdens necessarily, speed the progress that it breaks. These engineering whether safety, how the concrete tired life span regulation is, are important topic of modern engineering.The breakage caused by the fatigue load not only influenced but also did harms to the safety and normal use of constructions, so we discussed the effects of fatigue load on concrete. Based on the experiments, fatigue life distribution of concrete is studied using fatigue life statistics theory; the fatigue life equation is established.The study results in the paper can be concluded that the bending fatigue life of concrete can be described by two parameter Weibull distribution. I gained the relation between livability and fatigue life, and then drew the P-N curve. Compare the P-N curve of two parameter Weibull distribution with that of three parameters Weibull distribution, some differences between them are found. So we should choose the appropriate method to obtain the fatigue life of structure or component.At the raining season, or snowing in winter , concrete filled with hole water .Therefore, the research that development regulation of the concrete's crack that contains hole water have important meaning.Based on stress state in fracture surface and fracture mechanics, the fracture propagation is divided into tension-shear and compression-shear mixed cracking.Using fracture propagation engineering criterion, calculation formulae of critical internal water pressure of two kinds of failure model are obtained respectively; and its effect laws as fracture direction and lateral geo-stress coefficient are studied. Some following conclusions can be drawn:1.Under tension-shear complex model, fracture is most easily fracturing when fracture direction is parallel with direction of principal compression stress.2.Under compression-shear mixed model ,distribution law of critical internal water pressure is same as tension-shear complex model when (fs-λ) large than 0 But fracture is most easily fracturing when fracture direction are 45°or 135°angle with principal compression stress and (fs-λ) less than 0.