Investigation of finite element retrofit of T-shaped reinforced concrete beam–column joints by external bolts

Understanding the performance of reinforced concrete (RC) structures against earthquake load to design them is imperative. One of the fundamental issues determining the performance of concrete structures against earthquake load is investigating the joint behavior and its appropriate ductility. To attain adequate ductility in beams and columns, the joint must have sufficient strength and ductility to withstand the ultimate loads of beams and columns. In many RC structures that have been exposed to severe earthquakes, joint shear failure has been observed. Shear failure of the joint can be due to the weakness of oblique reinforcements in the beam-column joint area of RC structures. The use of high-strength external bolts under axial and cyclic loading in ABAQUS finite element software has been investigated in this paper. The arrangement and the amount of post-tension of the bolts are the parameters investigated in this study. The use of external bolts to retrofit the RC beam-column joints indicates an increase in confinement and consequently improves performance at the joint area. In addition to preventing shear failure in the joint fountain, the proposed method causes a capacity increase of about 44% in post-tension specimens. Also, it increases energy absorption by about 50% in retrofitting specimens.