Study On Several Durability Problems Of Reinforced Concrete Member

Base on full analysis of research results over the world, this paper conducts three parts of study on durability of concrete: first, the influence on behavior of reinforced concrete structure with corroded steel bar in compressive area has been studied systematically; second, imitated test on the whole corrosion damage process of R.C. beam has been done; third, present an elementary idea of using complexity science thinking model to study durability of reinforced concrete.First, influences on behavior of reinforced concrete structure with corroding bar in compressive area have been researched systematically mainly by experimental means. Three tests have been conducted. The research on behavior of general R.C. beam with corroded steel bar in compressive area shows that under the combined affect of rust expansive force and compressive stress, the concrete strength will reduce with the increase of rust rate, and that leads to damage of members. The test on direct measuring the relationship of bar rust rate and concrete strength has been presented, from which an experience formula has been erected successfully. Experimental investigation on influence of non-prestressed corroding steel bar in bending prestressed R.C. members has been done, it shows that the stress of prestressed steel bar varies only a little during non-prestressed steel bar corroding. On the basis of experiment, basic assuming include section's compressive stress block has been presented, base on that, basic section analyze formulas have been found and a program PCCB has been programmed, which results are compared with experiment, then it is used to analyze the load bearing capacity and normal usage behavior after bars corroded in compressive area of bending members. Experimental and treat study show that the influence on loading capacity of normal R.C. and prestressed R.C. by bar corrosion in compressive area is not great, but it has rather remarkable affect on the serviceability of them. During the corrosion course of bars in compressive area, the stiffness of section reduces rather sharply with the increasing of rust rate, and the flexibility and compressive strain of concrete become greater. Its amount has relation with acting load. The influence on sectional curvature of bending components is the greatest one, the ultimate curvature of corroding section decrease obviously, and the sectional curvature increases rather sharply with the increase of rust rate during the process of corrosion. The anti-cracking capacity of prestressed bending R.C. components may be damage.For the convenience of engineering usage and damage evaluation of structure, this paper presents a concept of sectional damage coefficient on the foundation of experimental and treatment study. Factors on sectional damage coefficient have been analyzed to get some of important properties of it such as its curve shape of three folded linear with rust rate. Calculating methods of sectional damage coefficient have been presented. The rather easy one among them is the simplified calculating table method. Excepting reflecting the damage level, the sectional damage coefficient can be easily used to calculate section stiffness of corrosion section,flexibility of beams etc. Consequently, it has a rather good usage value. To present such a coefficient and its calculating method is one of the most important results of this paper.On the basis of the study results gotten yet, this paper presents primarily a dynamic damage check method with corroded bars in compressive area of bending components, that is to say structural damage can be evaluated by measuring the model parameters of structure in use. Theoretical formulas under simple state had been educed, including the relationship of self-vibration frequency and section damage coefficient. Because the relationship of corrosion amount and model parameters of structure has been fond through sectional damage coefficient, the corrosion amount of steel bar in concrete can also be gotten indirectly by this kind of measuring, which presents a n...