Model error and reliability of reinforced concrete beams in shear designed according to the Modified Compression Field Theory

Model error (or model uncertainty) were probabilistically characterized for modified compression field theory (MCFT) Simplified and General Method approaches using experimental databases that contained reinforced concrete (RC) beams having shear failures with and without stirrups (168 and 368 specimens, respectively). It was found that when compared to the design shear model currently used in ACI-318, the General Method produced low model error variability indicating better consistency for the determination of shear strength. Structural reliabilities were then calculated for RC beams in shear designed to MCFT General Method (AASHTO LRFD, CSA A23.3-14, AS3600-2018) for a live-to-dead load ratio between 0 and 5, and for capacity reduction factor ϕ = 0.70, 0.75, and 0.80. It was concluded that the ϕ-factor for shear failure for Australian standards can be increased from 0.70 to 0.75 for RC beams with stirrups, providing a 7.1% increase in the design shear capacity and contributing to sustainable design and reduction in greenhouse gas emissions due to more efficient usage of materials