Shear Strength of High-Strength Concrete—ACI 318-95 versus Shear Friction


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Title: Shear Strength of High-Strength Concrete—ACI 318-95 versus Shear Friction

Author(s): R. E. Loov and L. Peng

Publication: Special Publication

Volume: 189


Appears on pages(s): 411-430

Keywords: friction; high-strength concrete; shear; stirrups

Date: 1/1/2000

The shear stress detrmined using ACI 318-95 is limited to the stress determined for 10,000 psi (69 MPa) concrete. This limit has been set because it was considred that there was not enou data to justify the extension of existing equations to higher strengths. Modification are suggested which adapt the ACI equations so thy apply to the full range of concrete strengths. The proposed equations predict the shear strength of beams more accurately than the current ACI equations. For the beams investigated, the coefficient of variation is only 2/3 of that obtained using the ACI equations. The proposed equations apply to concrte stengths as high as 18,000 psi (124 MPa). Aoart frin tgeur simplicity, the proposed equations have a number of other advantages. Unlike ACI equations 11-1 to 11-3, they correctly predict the increased strength of beams with small shear-span to depth ratios. Because the proposed equations assume the most pessimistic location of cracks, the maximum stirrup spacing requirements are satisfied sirectly so that adtitional spacing limitations appear to be extraeous. To illustrate the improvement that can be obtained using the proposed equation, published test results are compared with predicted values.