Study Of Effect Of Longitudinal Reinforcement Ratio On Shear Behavior Of Restrained Beams Without Web Reinforcement When Shear-Span Ratio Is 1.5

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 bahavior of reinforced concrete baeams. It is very different from that in practice as under such circumstances the longitudinal reinforcement ratio is among 1.0~1.5%. The codified design equations based on such testing data may be unconservative. Systematic investigation for effect of longitudinal reinforcement ratio on shear behavior of RC beams is particularly rare. A majority of previous studies on the effect of longitudinal reinforcement ratio on shear behavior of reinforced concrete members concerned about beams without web reinforcements and ultimate capacity; few gave detailed recording of development of cracking and failure process of RC beams without web reinforcements.This paper is a part of series of experimental study. Eight restrained beams without web reinforcements and different longitudinal reinforcement were tested under static point loads, with the shear-span ratio being kept around 1.5. On this basis, the overall process of cracking development under shear and the effect of longitudinal reinforcement ratio on it was investigated.At first, development of various cracks carefully recorded and strains on both the rebars and the stirrups were measured in detail, together with the deflections of the beam. In such a way, correlation between the measured strain profiles of the reinforcement and the observed cracking development of each specimen was pursued. Principal factors contributing to the crcking pattern and failure mode were figured out as a result. Secondly, comparison of the tested results unveiled effect of various longitudinal reinforcement ratios on development of cracks, final failure mode, and ultimate capacity. Primary conclusions were thus drawn. Moreover, the measured ultimate shear from the tests were compared with that predicted from China Design Code of Reinforced Concrete structures, GB50010—2002, and that from the Response2000, which is based on modified compression field theory by Michael Collins, both were undertaken before the experiments.The experiments showed that different amount of longitudinal reinforcement had a significant impact on formation of different cracks. To some degree, the distribution of strains in reinforcements reflects development of cracks. As for ultimate shear capacity, the difference between the predicted results obtained from the China Design Code, GB50010—2002, and the tested results is 51%, the predicted results from the Response2000, and the tested results is 86%.