Study On Effect Of Longitudinal Reinforcement Ratio On Shear Behavior Of Restrained Beams With Web Reinforcement When Top Longitudinal Reinforcement Truncated

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 circumstance 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. Five restrained beams with web reinforcements and different longitudinal reinforcement were tested under static two-point loading, 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 cracking patten, final mode, strain distribution of rebars and ultimate capacity of RC restrained beams with web reinforcements were 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 cracking 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 the predicted shear from China Design Code of Reinforced Concrete structures, GB50010—2002. The experiments showed that the cracking process of such restrained beams in this paper can be divided into three phases,that is,formation of the fanning zones,initialization and development of splitting cracks along longitudinal reinforcement,and accelerating development of the critical cracks. Different amount of longitudinal reinforcement has a significant impact on formation of different cracks. As for ultimate shear capacity,the difference between the predicted results obtained from the China Design Code and the tested results is 61%. Ultimate shear capacity of restrained beams is increasing disciplinarian with the increasing longitudinal reinforcement ratio.