Reliability Analysis And Prediction Of Residual Life Of Concrete Under Combinated Action Of Load And Freeze-thaw

In recent decades of years, durability of concrete has become the hot-spot in the field of civil engineering. Moreover, because concrete structures always expose to adverse environment and applied loads, the problem of deterioration of concrete becomes more and more serious. And the freeze-thaw property of concrete should be paid more attentions. So study on durability of concrete structures under freeze-thaw condition has great value in engineering practice.Freeze-thaw cycling is an important factor affecting the durability of concrete structures. Swelling of capillary water in micro pore of concrete after freeze makes deterioration of elastic modulus, compression strength and tensile strength of concrete seriously. By now, there have not a general agreement on mechanism of freeze-thaw in concrete. In practice, coupling with load condition, sulfate attack the problem is more difficult to solve.In this paper, based on the mechanism of freeze-thaw process, several factors affecting the freeze resistance of concrete were analyzed. According to experiment data, a regression model considering the interaction of freeze-thaw and loads was established.Since the failure of concrete under freeze-thaw condition is due to the progressive damage accumulation in concrete, based on reliability theory, the paper makes a comprehensive analysis of reliability of concrete with the freeze-thaw damage model considering interaction of axial load and freeze-thaw and the exsited model considering flexural load and freeze-thaw.Because temperature grade is one of the important factors in freeze-thaw problem, the extent of damage is regarded to be the result of temperature differences in concrete. According to three-factor Weibull distribution, a method that can predict residual life of concrete under different temperature condition and condition of interaction of load and freeze-thaw was proposed.Several evaluation methods to assess the residual life of concrete structures was proposed. A typical example of concrete bridge was selected to analyze with relative calculation methods. Also, analysis relating to the effects of temperature grade and loads on reliability of concrete structures was made.