STRUT-AND-TIE MODELS AND FAILURE MECHANISMS FOR BAR DEVELOPMENT IN TENSION-TENSION-COMPRESSION NODAL ZONE

Strut-and-tie models and compatible failure mechanisms for bar development and anchorage failure in a tension-tension-compression nodal zone are presented on the basis of the classical theory of plasticity, in particular the normality rule, and the lower and upper bound theorems. The concrete is assumed as a rigid-perfectly plastic material obeying the modified Coulomb failure criteria with zero tension cut-off, and for bar/concrete interfaces, the simplest possible yield condition is assumed. The strut-and-tie models presented in this paper assume uniform compression fields, and the upper bound solutions introduce a new flexural type of failure mechanism for concrete crushing failure. The strut-and-tie models identify different failure modes related to bond strength and dependent on material strength and geometry.