Numerical investigation of RC exterior beam-column connection with different joint reinforcement detailing

The proper detailing of joint reinforcement plays an essential role in ensuring adequate performance of reinforced concrete frames in terms of strength and ductility. The influence of various options of joint reinforcement detailing on joint performance has been numerically investigated using the nonlinear finite element analysis software, ABAQUS. Two sets of beam-column connections of various joint reinforcement detailing with greater spacing between the stirrups at two different locations have been modeled for achieving this purpose, considering validated experimentally tested specimen as reference. This study reveals that achieving the minimum requirments of joint reinforcement ratio according to the ACI 318-19 and ACI 352R-02 codes utilizing both internal cross ties and outer stirrups with greater spacing between the stirrups rather than closely spaced outside stirrups only is more efficient in terms of joint strength and deformation capacity. This implies that the contribution of the inner cross ties considering their configuration and location in the shear strength resistance should be considered. Therefore, the joint stirrups' main role should be considered as tension ties and a crack control reinforcement that requires less steel and wider spacing for the joint details rather than the confinement of the concrete. Furthermore, it has been observed that both the joint strength and deformation capacity have been significantly improved with the use of three layers of stirrups with two closed rectangular cross ties or one polygon cross tie. However, the employment of only two layers of stirrups with two crossed rectangular cross ties located at the middle third of the joint as well as diagonal bars at the corners between the beam and column of the joint core successfully controlled the joint cracks and improved the performance of the connection.