Shear Failure of Concrete Deep I-Beams: Fid-Bau Portal

Shear Failure of Concrete Deep I-Beams

Duanmu, Xiangyong / Xu, Dong / Hu, Ke

Relatively few studies have explored the shear behavior of concrete deep I-beams. This study presents a series of 12 shear tests on concrete deep I-beams with shear span-to-height ratios ( $a_{v} / h$ ) of 1.0 and 1.5. The effects of horizontal and transverse web reinforcement on structural deformation and shear strength are compared. The findings indicate that a minimum horizontal and transverse reinforcement ratio ( $ρ_{v} = ρ_{h} = 0.28 %$ ) significantly enhances the shear capacity. Additionally, an increase in vertical reinforcement ( $ρ_{v} = 1.26 %$ ) shifts the failure mode from shear tension to web crushing. Increasing horizontal web reinforcement has little influence on shear capacity at $a_{v} / h = 1.5$ , while it significantly enhances strength at $a_{v} / h = 1.0$ . The upper limit of shear strength for deep I-beams, as specified by ACI 318-19, appears conservative; a limit of $0.225 f_{c}^{'} b_{w} d$ is recommended. The Strut-and-Tie Model (STM) used in ACI 318-19 is conservative, demonstrating an average experimental-to-predicted shear strength value, $V_{\exp} / V_{pred} = 3.24$ , with a standard deviation of 0.63. Conversely, VecTor2 exhibits an average $V_{\exp} / V_{pred}$ of 1.07, with a standard deviation of 0.10. The panel element-based model, such as Mau’s model, is proven suitable for the analysis of deep I-beams.