Two-way shear full behavior of reinforced concrete flat slabs under membrane tensile forces

Recent reinforced concrete Flat slabs (RC) failures under two-way shear have raised a question mark on the reliability of the current understanding of the two-way shear design. Moreover, the two-way shear strength of Flat slabs subjected to membrane tensile forces is a dilemma, where design codes provision varies significantly for this case. In this study, the full behavior of flat RC slabs subjected to combined two-way shear and axial tension is investigated. The behavior in terms of load versus deformation, ultimate strength, and deformation. Firstly, an extensive review of the existing literature on the experimental testing and design models for Flat slabs under combined two-way shear and axial tensile forces was conducted. Secondly, an experimental test setup designed to apply combined two-way shear and tensile forces simultaneously on flat slabs was presented. Four flat slabs (1500 x 1500 x 150 mm) were tested under two-way shear up to failure, while subjected to different levels of membrane tensile forces. Thirdly, experimentally measured strength from current and previous studies were compared with that calculated using selected design codes and mechanical models. For flat slabs under two-way shear combined with membrane tensile forces, the following was concluded: (1) a disagreement between selected design codes, while the European design code is the closer to the experimental results; (2) The stiffness and the strength were reduced by 57% and 29% respectively which is highly dependent on the level of tension.