Application of critical shear crack theory on punching of flat slabs

This article deals with the punching capacity of a flat slab fragment supported by an internal atypically elongated column. Based on the results of this analysis and the application of Critical Shear Crack Theory, the reliability of two design models was determined. The CSCT model is a mechanical model where the shear force transferred by concrete in shear crack can be determined by accounting for the roughness and opening of a critical shear crack. The crack width is proportional to the slab rotation, which was obtained from a nonlinear program Atena and from experimental test and shear capacity was obtained by integrating the shear strength along the control perimeter. The aim of this analysis was to compare the application of CSCT in non-linear analysis and experimental test to point out the significant difference between obtained results, which shows the importance of experimental tests realization. Non-linear analyses provided unsafe results. Contrary the currently used EC2 model provided safe results when reduction of the control perimeter was applied. The best results were obtained in a combination of the CSCT model with measured rotations of the slab specimen.

Modelling of the shear resistance of self-stressed beams reinforced with FRP applying the Critical Shear Crack Theory

This paper presents a mechanical model of the shear resistance based on Critical Shear Crack Theory (CSCT) and its application for the checking of the shear ultimate state of self-stressed elements reinforced with FRP bars. The shear force, which is transmitted through the inclined crack by aggregate interlock, residual tensile strength, dowel action and inclined chord of the compression concrete, is calculated depending on the value of the inclined crack opening, determined according to the modified law “bond-slip” for FRP bars. The reliability of the proposed approach is confirmed by comparison both with the results of our own experimental investigations and with numerous research results by various authors.

Critical shear crack theory-based punching shear model for FRP-reinforced concrete slabs

Owing to their high strength-to-weight ratio, superior corrosion resistance, and convenience in manufacture, fiber-reinforced polymer (FRP) bars can be used as a good alternative to steel bars to solve the durability issue in reinforced concrete (RC) structures, especially for seawater sea-sand concrete. In this paper, a theoretical model for predicting the punching shear strength of FRP-RC slabs is developed. In this model, the punching shear strength is determined by the intersection of capacity and demanding curve of FRP-RC slabs. The capacity curve is employed based on critical shear crack theory, while the demand curve is derived with the help of a simplified tri-linear moment-curvature relationship. After the validity of the proposed model is verified with experimental data collected from the literature, the effects of concrete strength, loading area, FRP reinforcement ratio, and effective depth of concrete slabs are evaluated quantitatively.