Reinforced Concrete Frame Connections Constructed Using High-Strength Materials

An experimental research project was developed at The University of Texas at Austin to investigate the behavior of interior slab-beam-column joints constructed with high-strength materials. Four full-scale specimens constructed using normal and high-strength steel reinforcement, and welded wire fabric reinforcing cages were used in three of the specimens. A fourth specimen was constructed using normal strength materials (f’_c = 4000 psi and Grade 60 bars). The specimens were designed according to current American Concrete Institute guidelines.

Test results indicate that the high-strength beam-column joints performed quite satisfactorilly. The performance of the normal and high-strength steel reinforcement was comparable indicating that current recommendations can be extended to include the use of Grade 75 longitudinal reinforcement and welded wire fabric (f_y up to 80 ksi) as joint reinforcement. The effect of high-strength concrete on behavior was notable, especially with respect to stiffness, cracking, and energy dissipation. Current design recommendations for joint shear strength can be used for a safe estimate of unidirectional joint shear strength of interior joints constructed with high-strength materials.