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 struttie 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.