Shear Behavior Of Reinforced Concrete Deep Flexural Beams With Web Reinforcement

The design of reinforced concrete members requires to prohibit brittle failure,but shear failure is brittle. To avoid such kind of brittle failure, it is necessary to understand shear mechanism in detail. Due to the complexity of shear behavior, most shear design code provisions are principally empirical and just based on a limited number of test data available. Are these codified equations also appropriate for memebers with parameters out of such limited set of test data? Can we obtain expected level of safety on shear design by current design methods? To answer these questions, there is imperitive to set up a databank of RC shear beams,and furthermore, to evaluate the codified methods of shear design on such a basis.With an extensive literature review, 1463 test data has been extracted and compiled into a shear database of reinforced concrete beams with web reinforcement. The author analyzed the general rules of 288 deep flexural beams and then compared the test data with China Design Code of Reinforced Concrete Structures,GB50010-2002, Canadian Design Code of Concrete Structures, CSA Standard A23.3-94 and American Design Code of Concrete Strucutres, ACI318-89. The rules are as follows:①For members only with vertical shear reinforcement, V bd is positively proportional toρ_vf_yv; for members with vertical and horizontal shear reinforcement, when the shear span ratio a / d < 1, V bd is nearly constant regardness ofρ_vf_yv; when the shear span ratio a / d≥1, V bd is as positively proportional toρ_vf_yv.②For members only with horizontal shear reinforcement, V bd is proportional toρ_h fyh; for members with vertical and horizontal shear reinforcement, when the horizontal shear reinforcementρ_h fyh is relatively small, V bd is proportional toρh fyh; when the vertical shear reinforcementρ_h fyh is large, V bd is nearly constant.③When vertical reinforcement strengthρ_vf_yv is low, shear strength increases with the increase of concrete strength; while vertical reinfrocement strengthρ_vf_yv is higher, this increasing trend of shear strength slows down.The test reults are then compared with the ultimate strength predictions obtained using ACI318-89, GB50010-2002, and Canadian codes. The deep-beam provisions in Canadian Code shows the most consistent and yet conservative predictions, giving uniform safety margin and the lowest COV, which also in some extent follows the upper rules; GB02 code's predictions are conservative, and can not provide uniform safty margin. In some cases, the GB02 code tends to be rather conservative. ACI89's variance is the biggest, and sometimes overestimate the ultimate strength.