Study On Effect Of Longitudinal Reinforcement Ratio On Shear Behavior Of Restrained Beams Without Web Reinforcement When Shear-Span Ratio Is 2.5

For the reinforced concrete bend members, many factors can influence the shear strength of oblique section, furthermore the destroy mechanism is complicated, so the shear strength of oblique section is one of the unfathomed problems of reinforced concrete structure. The design codes of many countries exert statistical method, advance different formula, based on previous experiment results and research. Many countries base their design codes on the previous experiment results and researches, and establish different formulas using statistical method. But in general, to ensure the final shear failure, a very large longitudinal reinforcement ratio, usually larger than 2.8%, was chosen as a prerequisite in previous studies on shear behavior of reinforced concrete beams. It is very different from that in practice under such circumstances the longitudinal reinforcement ratio is among 1.0~1.5%. The codified design equations based on such testing data may be produce an error. This paper is a part of series of experimental study. Eight restrained beams without web reinforcements and different longitudinal reinforcement ratio were tested under static point loads, with the shear-span ratio being kept around 2.5. On this basis, the overall process of cracking development under shear and the effect of longitudinal reinforcement ratio on it was investigated. FengHong, the master of Liliren professor, has studied the effect of different longitudinal reinforcement ratio on shear behavior of restrained beams without web reinforcement when shear-span ratio is 1.5, so in this test, except the shear-span is 2.5, other parameters are the same as Fenghong's test. In this paper, on the basis of the two tests results, through comparing and analyzing, find some disciplinarian of effect of different shear-span ratio on shear behavior of restrained beams without reinforcement. In this paper, on the basis of the two tests results and through comparing and analyzing, we hope to find some disciplinarian of effect of different shear-span ratio on shear behavior of restrained beams without web reinforcement. In this experiment, the monotonic static load experiment was studied, and the extending and development of cracks,strains of the longitudinal reinforcements and deflection of the beams are carefully recorded, the correlation between the change of the strain of the reinforcements and the development of cracks of each experimented member was tried to keep track of, and by this way we hope to find out the general law of the crack development and the reinforcement stress distribution. Another, by comparison of the extending and development of cracks,final failure mode and ultimate capacity of members of different longitudinal reinforcement ratios we unveiled the law of effect of various longitudinal reinforcement ratios. The experiments showed that the change of longitudinal reinforcement has a significant impact on the development of cracks, the development of cracks of large longitudinal reinforcement ratio member is more sufficient than that the small longitudinal reinforcement ratio member. The change of the longitudinal reinforcement ratio will produce the change the failure mode, shear compressive failure will happen when the longitudinal reinforcement ratio is small and tear tensile failure will happen when the longitudinal reinforcement ratio is large; the longitudinal reinforcement ratio has a significant impact on the distribution of the reinforcement stress, members of large longitudinal reinforcement ratio will have a sufficient stress redistribution)and to some degree, the distribution of strains in reinforcements reflects the development of cracks. Different shear-span ratio obviously influence the failure mode, the strain of longitudinal reinforcement and the development of cracks. As for the ultimate shear capacity, the averaged experiment result is 22% more than the predicted results obtained from the China Design Code, GB50010—2002, and that of member of the least longitudinal reinforcement ratio is about 20% less than the predicted results obtained from the China Design Code.