Haunch retrofit of RC beam–column joints: Linear stress field analysis and Strut‐and‐Tie method application

This paper addresses the stress field of reinforced concrete (RC) beam–column joints retrofitted with haunches. Design such solution currently assumes internal forces evaluated by so called β-factor approach, which was originally conceived targeting enhancement steel moment-resisting frames. Extension to RC is subsequent as it emerges from literature survey. The analytical model first critically rediscussed. Inconsistencies adopted structural scheme, respect actual mechanical behavior, may lie on compatibility conditions are imposed between haunch and beam (or column). In this regard, two-dimensional finite element models (FEM), using linear-elastic materials, employed study two benchmark specimens derived literature. A partial validation carried out against experimentally forces. Results show that, for haunches extended flat plates stiff diagonals, compressive diffusion affects entire region. Consequently, beam's kinematic hypothesis linear strains no longer valid. predicted joint shear demand resulted underestimated approach 50%. Since 2D FEM be not efficient many practical circumstances, an application Strut-and-Tie alternatively proposed. Finally, both limitations possible extensions proposed approaches stated transparently.