Shear Strength and Ductility of Reinforced High Performance Concrete Beam

Durability requirements in the design of a new structure have never been a primary concern before today. The use of high performance concrete seems to be the best solution to solve this problem. However, the correct use of this material requires the application of suitable code recommendations. In this context, it is well known that an important problem of reinforced concrete structures consists in evaluating shear strength. Several experimental researches have shown that RC beams shear failure can occur prior to flexural failure, often in a brittle way. Experimental researches conducted on normal strength concrete beams are the basis of the empirical equations, proposed by different codes, to evaluate the shear strength even in high performance concrete beams. In this paper shear strength of high strength reinforced concrete beams with or without shear reinforcement and /or steel fibers is experimentally investigated. Compressive strength, shear span-depth ratio and incorporation of steel fibers were adopted as major factors. In the range of variables tested, results indicate that beams with fibers and no stirrups, show a moment response and strength comparable to the response of beams with fibers and stirrups. Fibers (with or without stirrups) increase significantly bending stiffness after first cracking; shear strength is increased too and this fact altered failure modes which turns into flexural and are characterized by an enhanced ductility. Experimental evidence shows that, stirrups may be replaced by an adequate amount of fibers without compromising the overall structural behavior.