Previous researches carried out by numerous scholars have suggested that thelongitudinal steel ratio has influence on the shear strength resistance of the reinforcedconcrete members. A majority of previous studies on the effect of longitudinalreinforcement ratio on shear behavior of reinforced concrete members concerned aboutbeams without web reinforcements and ultimate capacity; few gave detailed recording ofdevelopment of cracking and failure process of RC beams with web reinforcements. This paper is a part of series of experimental study. Four simply supported beams withweb reinforcements and different amount of longitudinal reinforcement were tested understatic two-point symmetrical concentrated loading, with the shear-span ratio being keptaround 1.5. The overall development process of cracking under shear and the effect oflongitudinal reinforcement ratio on cracking, failure modes, strain distribution ofreinforcements and ultimate capacity of RC beams with web reinforcements wereinvestigated. The results of this experiment and a previous one done by Wang Wei werecombined and compared with shearing resistance strength value predicted by TheChinese Code GB50010-2002 and the shearing strength value predicted byResponse2000. At first, development of various cracks was carefully recorded and strains on boththe longitudinal reinforcements and the stirrups were measured in detail, together withdeflections of the beam. Furthermore, correlation between the measured strain profiles ofthe reinforcement and the observed cracking development of each specimen was pursued.Principal factors contributing to the cracking pattern and failure mode were figured out asa result. Secondly, comparison of the tested results unveiled effect of various longitudinalreinforcement ratios on development of cracking, final failure mode, and ultimatecapacity. Primary conclusions were thus drawn. Performance of beams under momentand shear may be different from that under pure moment or pure shear. Consequently, theshear-bending interaction relationships of specimens were investigated in this paper. The experiments showed that different amount of longitudinal reinforcement had asignificant impact on formation of different cracks. In the specimen with the webreinforcement, the flexure crack first appears at the mid span in the pure bending segment.Along with load growth, flexure-shear inclined crack or the web shear inclined crackgradually appear in the shear segment expanding to the support. Furthermore, differentlongitudinal reinforcement ratios lead to different failure modes. Along with longitudinalsteel ratio increase, in the shear span segment inclined cracks development tends toincrease. Along with longitudinal steel ratio increase, the flexure crack tends not to befully developed. The flexure crack upwards development reduces gradually. The crackwidth also gradually reduces. The corresponding position of the inclined crack inclinationangle reduces gradually. The size of the longitudinal steel reinforcement has a markedinfluence on the failure mode of the simply supported beam with web reinforcementunder the action of the concentrated load. Low longitudinal steel reinforcement will resultin bending failure. High longitudinal steel reinforcement ratio will result in shear failure.Comparing 3 beams in which shearing failure occurred, it was discovered that the actualexperiment result is higher than the shearing resistance strength value predicted by TheChinese Code GB50010-2002 by 30％. Comparing 5 beams which failed due to bendingfailure, it was discovered that the actual experiment result is higher than the bendingresistance strength value predicted by The Chinese Code GB50010-2002 by 65％.Comparing with 3 beams in which failure was due to shearing failure, it was discoveredthat the experiment actual result is higher than the shearing strength value predicted byResponse2000 by 23％. Comparing 5 beams which failed due to bending failure, it wasdiscovered that the actual experiment result is higher than the bending resistance strengthvalue predicted by the Response2000 by 15％. The interaction of flexure-shear in thespecimen in preliminary discussion indicates that the reinforced concrete beam's bearingcapacity is decided together by the bending moment and the shear force. Comparing tothe singly reinforced section beam it can be said that shear failure is more likely to occurin the doubly reinforced section beam with the symmetrical reinforcement.
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