Authors
Abstract
In this paper 115 reinforced concrete (RC) beams failing in shear, obtained from the literature, are used to study the effect of the major parameters on the shear strength of normal strength concrete (NSC) and high strength concrete (HSC) beams. These parameters include the shear span/depth (a/d) ratio (between 2.0 and 4.9), concrete compressive strength fe (between 22.1 and 125.3 MPa), the longitudinal steel ratio p.. (between 0.01233 and 0.06972), stirrup shear strength p,f, (between 0.204 and 8.053 MPa) and beam size (b,d).
Following the recent ACI 318M-02 Code, all 115 beams are not "deep" (a/d≥2.0). A proposed design method is introduced in these "non-deep" beams, which shows that increasing p.f, would lead to a slower increase in shear capacity than a direct proportionality to p.fy. This stirrup effectiveness method K contrasts with the conventional code stirrup design which is based on the usual 45" truss analogy. In these code approaches, doubling (say) p.f,, would lead to twice the increase in beam capacity due to stirrups in contrast with the proposed design equations.
For all methods considered, the ratio is calculated of shear strength of beams V, TEST to the design shear resistance V. DES. The proposed design equations lead to safe design with a low coefficient of variation (COV). This COV is only 17.5 percent which is significantly less than for other methods ranging between 30.8 to 35.9 percent.
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