Joint strengthening by external bars on RC beam-column joints

[EN] Column strengthening is a very common practice for improving the seismic performance of reinforced concrete frame structures or repairing damage after a seismic event. Several methods are employed for column strengthening, which can improve column strength by preventing its shear, bending or compression failure. However, not all methods allow column strengthening connections between adjacent floors, thus the beam-column joint strength could be limited by the column-joint interface capacity. This work aimed to analyse two joint strengthening designs, for which an experimental campaign of eight full-scale beam-column joints strengthened with steel caging, and subjected to cyclic and gravity loads, was carried out. As access to joint panels is very complex in existing structures, joint strengthening consists of external solutions: vertical or diagonal bars and capitals connecting columns. The results showed that these techniques significantly increased beam-column joint strength and highlighted that failure can be undesirably transferred to the joint. Vertical bars prevented the bending failure of the column-joint interface, but failure occurred at the joint in this study. Diagonal bars can also prevent joint failure.The authors wish to thank the financial support provided by the Spanish Ministry of Science and Innovation and the Spanish Ministry of Economy and Competitiveness with Research Projects BIA 2008-06268 and RTI2018-099091-B-C22.Ruiz Pinilla, JG.; Cladera, A.; Pallarés Rubio, FJ.; Calderón García, PA.; Adam, JM. (2022). Joint strengthening by external bars on RC beam-column joints. Journal of Building Engineering. 45:1-14. https://doi.org/10.1016/j.jobe.2021.1034451144