Design considerations for interior RC beam–column joint with additional bars

• Seismic performance of beam–column joints with strengthening details is studied.
• Enhanced seismic performance of the joints is verified from cyclic loading tests.
• Bond resistance of beam bars and joint shear capacity are quantitatively evaluated.
• Energy dissipation capacity is defined as a function of the bond resistance.
• Recommendations for seismic design and detailing of beam–column joint are given.

The seismic performance of beam–column connections and joints can be enhanced by using improved details in the joint and ensuring a strong connection behavior. However, specific provision to evaluate quantitatively the increased bar–concrete bond and shear strengths in the beam–column joint is not given in current design codes. In the present study, cyclic loading tests were performed for beam–column connections of which joint detailing was improved by placing additional 45° bent bars and 90° hooked bars. The test results showed that despite small hc/db values, by using the improved details, bond–slip of beam flexural bars and diagonal cracking were substantially decreased in the joint. To address the enhanced performance in the design of beam-column joints, the bond resistance and joint shear strength were quantitatively redefined considering the details of the additional bars. In addition, the relationship between the bond parameter and energy dissipation capacity was proposed. On the basis of the results, considerations for the seismic design and detailing of beam–column joints with additional bars were recommended.