Assessment of plastic hinge length in reinforced concrete columns

Plastic hinge properties are crucial parameters in predicting the nonlinear response of structural elements. Because of the intricate material nonlinearity, precise determination of the plastic hinge length (PHL) has encountered several obstacles. Over the last few decades, there have been various definitions and models put forth to forecast this length, nevertheless, the outcomes displayed significant disparities. Therefore, the paper introduces a comprehensive method for determining PHL using certain criteria, including rebar strain profiles, concrete cover and core peak strains, curvature profiles, and damage observations. Furthermore, a set of four full-scale reinforced concrete (RC) columns measuring 400 mm x 400mm x 3000mm and featuring varying transverse reinforcement configurations were constructed and subjected to testing under a high axial load ratio (ALR). The tested results implied that it is necessary to separate the PHLs based on different criteria. The high axial compression load led to enhancing the PHLs, which were based on rebar compressive yield strains, curvature profiles, concrete cover and core peak strains. In contrast, it has a minor effect on PHL based on tensile yield strains. In addition, the amount of transverse reinforcement had an insignificant effect on all PHLs for tested columns. Hence, a revised equation was proposed to estimate the equivalent PHLs of rectangular RC columns based on tested results and a 114-column database. The proposed equation had better accuracy compared with some other model results in the literature.