An Experimental Method to Characterize the Shear Behaviour of Concrete Under High Confinement

• Published in: Experimental mechanics 2023-04, Vol.63 (4), p.665-680
• Main Authors: Abdul Rahman, R., Forquin, P.
• Format: Article
• Language: English
• Subjects: Axial loads; Biomedical Engineering and Bioengineering; Blast loads; Characterization and Evaluation of Materials; Compressive strength; Concrete structures; Confinement; Confining; Control; Damage prevention; Dynamical Systems; Engineering; Experimental methods; Finite element method; Lasers; Ligaments; Normal stress; Notches; Optical Devices; Optics; Photonics; Projectiles; Research methodology; Research Paper; Shear strain; Shear strength; Shear stress; Shear tests; Shearing; Solid Mechanics; Vibration
• ISSN: 0014-4851; 1741-2765
• DOI: 10.1007/s11340-023-00948-9

Background Shear behaviour of concrete under high confining pressure has not been thoroughly studied despite being widely observed in concrete structures subjected to high blast loading or projectile impact. Objective The objective of the present study is to propose an experimental method to investigate the shear behaviour of concrete under high confinement in static conditions. Methods This method is based on the Punch-Through Shear testing technique. A specimen with two cylindrical notches is first subjected to an active confinement pressure by means of a triaxial cell and an axial loading is then applied to punch through the central part of the specimen. However, in the previous PTS experiments, the inner cylindrical parts being subjected to uniaxial compression, the level of confining pressure applied in the first stage was usually limited to the sample uniaxial compression strength. In the present work, much higher compression stresses of a few hundreds of MPa are applied to the specimen in both radial and axial directions thanks to the small metallic rings used to confine the inner cylindrical parts of the specimen . A series of numerical simulation based on finite-element method is conducted in order to optimize the notches and sample dimensions. Results Experimental tests conducted on a common concrete showed that the confinement rings successfully prevented any compression damage in the central part during sample pressuring and shearing. The experiments conducted at different levels of confining pressure showed that the higher the confinement level the higher the concrete shear strength. Experiments done with a confining pressure of 100 MPa with two different ligament lengths showed that higher nominal shear stress is obtained with a smaller shear surface. Conclusion The proposed experimental technique allows reaching confining pressure up to 150 MPa (which corresponds to radial stress of 374 MPa in the ligament) and nominal shear strain of about 38% in the ligament of the concrete sample and confirms that the shear strength increases with the level of normal stress applied to the sheared surface.