Title: Balanced Damage Concept for Beam-to-Column Connections of Special Moment Frames Using HPFRC
Author(s): Youngjae Choi and Shih-Ho Chao
Publication: Structural Journal
Appears on pages(s): 237-249
Keywords: beam-column; fiber reinforcement; high performance; special moment frames
This paper presents an experimental study on the seismic performance of reinforced concrete (RC) perimeter interior special moment frames (SMFs) that use high-performance fiber-reinforced concrete (HPFRC) in joint and beam plastic hinge regions. This research evaluates the feasibility of using both HPFRC joint and beams as major sources of energy dissipation in an effort to reduce overall damage and repair cost after earthquakes and to provide ease of construction for beam-column connections. A balanced damage concept was used so the energy dissipation was shared by the joint and beam plastic hinges, thereby preventing severe damage from occurring to the beams. This concept together with the mechanical properties provided by HPFRC, including high shear and bond strength, reduce the need of placing a large number of transverse reinforcement in the joint and beam plastic hinge regions. A full-scale HPFRC slab-beam-column (SBC) subassemblage designed with this concept was tested under large displacement reversals. This specimen used a small amount of transverse reinforcement (approximately 20% of that used in a typical RC joint) in the joint and no transverse reinforcement in the beam plastic hinge regions, thus significantly enhancing the constructability. A counterpart conventional RC specimen compliant with ACI 318-14 was tested under the same loading protocol. Both specimens showed stable hysteretic responses up to 3.5% column drift ratio without significant strength degradation, which meets the collapse prevention structural performance according to the criteria given in ACI 374. Experimental results show that the damage in the HPFRC specimen was distributed in both joint and beam ends, whereas the conventional RC specimen had severe damage concentrated in the beam plastic hinging regions. This research proves the feasibility of using ductile HPFRC joint to dissipate seismic energy, thereby balancing the damage between the joint and beams.