Large Reinforced Concrete Special Moment Frame Beams under Simulated Seismic Loading
Tea Visnjic, Grigorios Antonellis, Marios Panagiotou, and Jack P. Moehle
Appears on pages(s):
beams; cyclic; frames; reinforced concrete; reinforcement buckling; seismic
In modern construction of tall reinforced concrete special moment-resisting frames, beams with section depth reaching 1200 mm (48 in.) are not uncommon. The ACI 318-08 Code provisions for these beams could result in hoop spacing as large as 300 mm (12 in.) in the plastic hinge zone, potentially leading to inferior beam performance during earthquakes due to premature buckling of the longitudinal reinforcement. An experimental study investigated the seismic behavior of two 1220 mm (48 in.) deep special moment frame beams, one barely satisfying the ACI 318-08 hoop spacing limits and another with closer hoop spacing. The predominant failure mode of both specimens was longitudinal bar buckling; however, behavior was notably improved in the beam with reduced hoop spacing. The tests served as the basis for building code changes introduced in ACI 318-11.