- Compressive Fracture
In comparison to tensile failure, compressive fracture is at least one step up in the degree of complexity. Shear, and probably also buckling instabilities close to the surface of specimens/structures subjected to compression are two additional mechanisms that cannot be neglected. The lattice model used thus far has shown excellent capability of simulating the fracture process in concrete subjected to external tension or combined tension/shear, as shown in Chapters 6 and 7. Always, it seems the cracks tend to follow the direction of the major principal stresses. When cracks are conªned to grow in a certain direction they will escape in another direction where the specimen/ structure allows for that. Shear fracture (pure mode II or mode II according to the classical fracture mechanics deªnition) may occur under some peculiar conditions that are not regularly met in ordinary (reinforced) concrete structures. In Section 7.1.2 we alluded to possible circumstances under which shear failure might occur.