Seismic Damage and Fracture Mechanism of Reinforced Concrete Beam-Column Joints

Seismic damage of Reinforced concrete (R/C) framed structures are significantly influenced by the performance of beam column joints. Most of the critical damages are happened in R/C. beam column joints and the extent of damage depends on integrity and redundancy of structural members associated with joint connectivity. Force transfer mechanism (FTM) in R/C joint is a key issue to be addressed for good seismic performance of a joint. Fragility of R/C joints are in the form of non ductile shear failure prior to beam yielding and ductile failure after beam yielding. This localized damage in joint significantly influenced the progressive collapse of global structure. This article provides necessary information about seismic vulnerability and fracture mechanism of R/C beam column joint and relevant stress field theories based on force transfer mechanism (FTM) due to synergistic effect of both external forces and internal reaction of materials are well established for joints. The reduction of joint reinforcement possible by consider joint strength as part of complete FTM, but not under independent shear strength of steel and concrete alone. This assessment helps to provide less conservative reinforcement detailing of joint to mitigate constructability issues of fabrication and concreting in joints.