Evaluation of structural performance for beam-column joints with high-strength materials under cyclic loading using PIV technique

Abstract

Current design codes require long bar development length and high joint hoop ratio in reinforced concrete (RC) exterior beam-column joints using high-strength materials, which reduces constructability. This study investigated the seismic behavior of RC exterior beam-column joints with insufficient joint hoops and using high-strength beam flexural bars (Grade 600 MPa) and/or high-strength concrete. Six half-scale exterior beam-column joints were tested under cyclic load reversals. The test parameters included the yield strength and diameter of beam flexural bars and the concrete strength. As an innovative measurement method, particle image velocimetry (PIV) technique was implemented to accurately measure the joint shear deformation, beam flexural deformation, plastic hinge length, surface strain fields, and crack patterns in the beam-column joint specimens. The PIV method predicted the location of beam cracks accurately. The test results showed that the use of high-strength bars increased bond-slip due to higher bond requirement, which decreased the energy dissipation capacity by 16% compared to the joint specimen using Grade 400 MPa bars. Further, the joint shear deformation and the beam crack width increased, while the plastic hinge length decreased. The combined use of high-strength concrete and high-strength bars improved the structural performance in terms of the energy dissipation capacity and initial stiffness.