Experimental Study Of Concrete Tensile Fatigue Residual Strength In The Corrosion Condition

In practical projects, a large number of concrete structure not only bear cycle fatigue loads, but also influenced by the various environmental corrosion factors, such as the bridge structure nearby salt lake area, highway and railway in area influenced by acid rain or snow removal agent in winter, marine oil production platform and port impacted and erosioned by seawater and so on. Fatigue failure problem of concrete structure in the corrosion conditions gradually aroused wide attention of all social sectors. The corrosion fatigue of concrete structure is mainly due to the initial defects after material erode and internal injury in the process of fatigue which lead to the decline of strength,so understanding the change rule of concrete tensile fatigue residual strength has practical significance. This paper mainly research mechanical property of concrete variable cross-section specimen corroded by sodium sulfate solution and sodium chloride solution, the specimen is made considering the principle of not eccentric by tension load and easy installation.This paper made27prismoid concrete variable cross-section specimen, among which9aren’t corroded,9is put in the sodium sulfate solution whose concentration is1.5g/L and9is put in the sodium chloride solution whose concentration is3g/L. According to the differentce of the corrosion solution and the fatigue number, study the residual strength of the prismoid concrete variable cross-section specimen. In conclusion, the research work of this paper mainly include the following aspects:(1) make reasonable selection of the corrosion solution, corrode the prismoid concrete variable cross-section specimen, determine the corrosion time scientificlly and reasonably, observe the change of corroded specimens in the process of the corrosion, analysis damage form of concrete after corroded, find out the influence factors of the concrete corrosion damage under the action of different corrosion medium.(2) Do the tension fatigue residual strength test on the concreted prismoid concrete variable cross-section specimen, compare with the concrete specimen which are not corroded,research shows that it can clearly reveal the degradation of the concrete fatigue residual strength according to the method of corroding the specimen firstly and then after a certain number of fatigue load. Plotted P-R-N curve according to the experimental data, this curve can explain the characteristic of "Sudden death" of the concrete fatigue residual strength under corrosion condition.(3) The tensile secant modulus of concrete material after corrosion will reduce with the increase of the fatigue cycle index, compared with the specimen which is not corroded, it is still accord with the semi logarithmic relationship between the fatigue number and residual secant model, it exist linear relationship between square root of the concrete residual strength and residual secant modulus.(4) Through the experimental study, establish attenuation model of concrete tensile fatigue residual strength under the condition of not corroded and corroded. Defines the damage expression D based on boundary concept and damage mechanics theory, the test proved that the corrosion of sodium chloride solution influence more serious to concrete fatigue performance, plotted damage curve of concrete fatigue test after corroding by different solution, reveals the development law of concrete corrosion fatigue damage.