Strength of Struts and Nodes in Strut-Tie Model

General approaches for determining the effective stress levels of concrete struts and for verifying the bearing capacity of nodal zones in strut-tie models are proposed. The effective stress levels of concrete struts are determined by implementing the principal stress ratios of the finite elements (used in the finite-element nonlinear analysis of a two-dimensional plain concrete) corresponding to the strut regions of the strut-tie model. Based on the obtained geometry of the struts, nodal zones are developed and their bearing capacity is verified using a finite-element nonlinear analysis with a failure criteria that incorporates the different state of stresses. To illustrate the proposed approaches, an analysis of a reinforced concrete beam tested to failure is conducted using the strut-tie model approach with the aid of interactive computer graphics program NL-STAT.