Analysis of the structural behavior of beam-column joints in reinforced concrete frames considering bending towards the reduced side of the cross section

Abstract The beam-column joints are called discontinuous regions and, therefore, could be designed by the strut and tie method. In beam-column joints where the bending plane coincides with the column's smaller dimension, the bending moments associated with the compatibility between the beam and column are typically small. However, the reduced size of the region necessitates careful reinforcement verification and detailing to prevent plastic strain and cracking. In this context, the present study sheds light on the behavior of these connection regions. In this study, the structural behavior of corner beam-column joints of reinforced concrete frames was analyzed, including the evaluation of the stress flow configuration in the concrete and the assessment of the strut and tie model. For this, numerical models in finite elements were developed, considering frames with different dimensions for the beam and the column. Situations with and without the presence of anchorage clamps were considered. Models with bending towards the column's larger cross-sectional side exhibited superior strength, highlighting the importance of column dimensions for determining beam efforts. The top reinforcement exhibited high tensile strain only in some cases of bending towards the larger side of the column cross section, and these values were not significant along the extension of the anchorage length. In all cases, the bottom reinforcement close to the support was compressed, the clamps were not requested in tension as expected and did not influence the results. It is concluded that there is an overestimation of this reinforcement by the Brazilian standard criteria, since a reduction is not considered for a negative moment in the joint. The proposed strut and tie models showed good agreement with the numerical results, suggesting that the theoretical bending moments derived from these models are conservative.