Strength of two-dimensional nodal zones in strut-tie models

A strut-tie model approach has proven to be useful for the detailing of disturbed regions of structural concrete. This approach promotes a better understanding of force transfer mechanisms and improves the designer's ability to handle unusual circumstances. Despite the advantages of the strut-tie model approach, portions of them lack adequate definition and have not been extensively verified for use in structural analyses and designs. One of the specific areas in which further research is required is nodal zones. Before the strut-tie model approach can be practically implemented into various regions of structural concrete, a proper way of checking the strength limits of nodal zones to allow safe transfer of strut and tie forces through nodal zones must be established. In this study, a literature review of the approaches for evaluating the limits of nodal zone strength was conducted, and a consistent and general approach applicable to any type of strength verification situation of two-dimensional nodal zones was proposed. The validity of the proposed approach was examined by evaluating the ultimate strength of several nodal zones that were tested to failure.