Biaxial testing machine for mixed mode cracking of concrete

Cracks in concrete may open in two fundamentally different modes in plane problems; normal to the crack plane (Mode I) and sliding of the crack faces (Mode II). A general loading situation consisting of an arbitrary combination of normal and shear stresses will invoke a combination of the two fundamental opening modes, i.e. leading to mixed mode cracking. Detailed experimental knowledge of the initiation and propagation of cracks in concrete under mixed mode loading is an important prerequisite for the formulation of mixed mode fracture mechanical models. For this purpose, an extremely stiff, bi-axial testing machine with mutually independent servo-hydraulic pumps has been developed. The setup is designed with…