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Title No. 119-S102
This study developed a simplified shear strength model considering the properties of the walls: uniformly distributed web reinforcement and boundary elements. Based on an existing compression zone failure mechanism model, the concrete shear strength of a wall was defined as a function of the compression zone depth and the diagonal tension strength of concrete. For practical implementation, the proposed design equation was further simplified to transfer the effect of the compression zone to the average vertical reinforcement ratio, which is similar to the one-way shear strength equation in ACI 318-19. The permissible maximum shear strength was also developed based on the effective compressive strength of the diagonal concrete strut. For evaluation, the proposed shear strength model was applied to existing test specimens. The prediction results agreed with the tested strengths in wide ranges of wall design parameters.
Keywords: diagonal tension cracking; shear failure mode; shear strength; shear wall; web crushing.
INTRODUCTION
The recent version of ACI 3181 revised the shear strength provisions for one-way shear, considering the effects of the longitudinal reinforcement ratio and the axial load for the shear strengths of beams and columns (ACI 318-19 Section 22.5).1 Meanwhile, the shear strength equation for walls (ACI 318-19 Section 11.5.4) was revised to be the same as that for seismic provisions (ACI 318-19 Section 18.10.4). However, in contrast to the one-way shear strength equation, ACI 318-19 does not consider the effects of the longitudinal reinforcement ratio and axial load on the shear strength of walls. Further, the properties of walls differ from those of beams and columns: vertical reinforcement is distributed in the web (vertical web reinforcement), and columns or flanges are frequently used for boundary elements. Thus, to accurately predict shear strength, these wall properties need to be addressed. Further, in high-rise buildings subjected to earthquakes, the shear force is amplified by the nonlinear dynamic mode effects. This shear amplification was addressed in ACI 318-19 seismic provisions (Section 18.10.4).1 To deal with the increased shear demand, wall shear strength needs to be accurately predicted.
Several studies have investigated the effect of vertical web reinforcement on the shear strength of walls. For example, Cardenas et al.2 investigated the effect of vertical web reinforcement while considering three cases of vertical reinforcement distribution:...