Failure assessment of anchor bolts by means of nonlinear finite element analyses

Numerical simulations in structural engineering require the use of realistic material models. As far as simulations of concrete structures are concerned, material models have to account for different degradation processes within the cement matrix-aggregate composite. In uniaxial tension experiments, highly localized tensile cracks result in brittle failure. In the low-confined compression regime, a region of transition from brittle to ductile fracture exists, separating brittle softening behavior from ductile failure regimes characterized by little or no degradation of strength. In this paper, the Extended Leon Model (ELM) is considered for the description of failure of concrete. It accounts for the dependence of strength on the Lode angle. Moreover, the influence of confinement on the ductility of concrete is considered by means of a pressure-dependent ductility function. Tile fictitious crack concept which is employed for the calibration of the ELM is reformulated for application to axisymmetric problems such as failure assessment of anchor bolts. The ELM is applied to the simulation of an anchor bolt with a small embedment depth. Failure of this type of anchors is characterized by the development of a cone-shaped failure surface.