Shear Behaviour of RC Beams without Stirrups Made of Normal Strength and High Strength Concretes

The paper describes a study in which sixteen reinforced concrete beams without transverse stirrups were tested to failure to investigate the influences of the shear-span/depth ratio (a/d), the longitudinal steel ratio (p) and the compressive strength of concrete (f'(c)) on the global behaviour in shear for beams made of normal strength concrete (NSC) as well as high strength concrete (HSC). Crack development and propagation were studied through continuous monitoring of the shear cracking using digital video recording. The test results show that the shear capacity depends more on the shear-span/depth ratio (a/d) and the longitudinal steel ratio (rho) and relatively less so on the compressive strength (f'(c)) in the case of FISC. Based on this study and on data collected from the literature, a proposition for computing the shear stength of concrete beams without stirrups is made; it covers compressive strengths in the range of 40 MPa to 104 MPa. Using the proposed shear formulae, a comparison is made between the different modelling approaches used in the major design codes concerning the contribution of concrete to the shear resistance of beams. In the light of the test results obtained in the present investigation, the applicability of these code approaches to high strength concrete is examined.