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.ChenChen ,the master of zhangchuan professor,has studied the effect of longitudinal reinforcement ratio on shear behavior of restrained beams with web reinforcement when shear-span ratio is 1.5,and the longitudinal reinforcement of his tries was disposed through the whole beam;But the top longitudinal reinforcement of beam is usually truncated in practice. Therefore,it is put forward that studies that the effect of longitudinal reinforcement ratio on shear behavior of restrained beams with web reinforcement when the top longitudinal reinforcement of beam is truncated according to the China Design Code,and comparing the results of different tests,and then wishing that that find some disciplinarian approaching the civil practice.In this paper,five restrained beams with web and different longitudinal reinforcement ,and above longitudinal reinforcement is truncated,were tested under static point loads . 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 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,and the tests results were compared with ChenChen tests results. 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. It was not founded of evident disciplinarian between the results of this test and the results of ChenChen test,and it shows that shear behavior of restrained beams with web reinforcement is not receded when the top longitudinal reinforcement of beam is truncated.