Title: Special Moment Frames with High-Strength Reinforcement— Part 1: Beams
Author(s): Duy V. To and Jack P. Moehle
Publication: Structural Journal
Appears on pages(s): 239-252
Keywords: Grade 100 reinforcement; high-strength reinforcement; rotation capacity; special moment frame beams; spread of plasticity
A laboratory test research program was undertaken to characterize the performance of reinforced concrete beams with high-strength reinforcement subjected to reversed cyclic lateral loading simulating earthquake effects. The beams are representative of beams used in special moment frames. Four beams were tested in the laboratory: one with A706 Grade 60 reinforcement, one with Grade 100 reinforcement having tensile-to-yield strength ratio (T/Y) of 1.17, one with Grade 100 reinforcement with T/Y = 1.26, and one with A1035 Grade 100 reinforcement with T/Y = 1.38. In each beam, the noted reinforcement grade was used for both longitudinal and transverse reinforcement, except the beam with Grade 100 T/Y = 1.17 had transverse reinforcement of Grade 100 with T/Y = 1.26. All beams achieved rotation capacity of at least 0.045 radians. The beams with A706 Grade 60 and Grade 100 (T/Y = 1.26) reinforcement failed by buckling of longitudinal bars over several hoop spacings. The other two beams with Grade 100 reinforcement failed by fracture of longitudinal bars at the maximum moment section. Strain gauges installed on longitudinal bars indicated that beams with higher T/Y achieved greater spread of plasticity compared with beams with lower T/Y.