High-strength concrete exterior beam-column joints with high-yield strength steel reinforcements

This paper presents the experimental and analytical investigations carried out on high-strength concrete (HSC) beam-column joints with Grade 700 longitudinal rebars in beams and columns. Five full-scale exterior RC beam-column joints with various reinforcement detailing were designed according to the special seismic provisions of ACI 318-14. The variables in test specimens include the concrete compressive strength, yield strengths of reinforcement and the axial compression levels. The test specimens were subjected to constant column axial loading and quasi-static lateral load reversals. The performance of each test assembly was examined in terms of cracking patterns, lateral loading capacity, strain profiles of the reinforcements, secant stiffness, energy dissipation capacity, and the bond performance. All specimens displayed ductile failure mode and it was concluded that the use of high-strength concrete and the applied axial compression loading could improve the bond condition of the specimens. Parametric studies were performed to study the influence of various parameters on the strength, required development lengths and energy dissipation capacity of the specimens. An explanation for the observed cracking pattern and further analytical investigations using a strut-and-tie modeling was conducted.