Evaluation of Steel Fiber Reinforcement for Punching Shear Resistance in Slab-Column Connections - Part II: Lateral Displacement Reversals

Abstract

Results from an experimental investigation aimed at evaluating the seismic behavior of steel fiber-reinforced concrete slab-column connections are presented. Two approximately half scale slab-column subassemblies were tested under combined gravity load and lateral displacement reversals to evaluate the ability of fiber reinforcement to increase the connection punching shear strength and deformation capacity. The connection of one specimen featured high-strength (2300 MPa [334 ksi]) hooked steel fibers in a 1.5% volume fraction, while the other connection was reinforced with regular strength (1100 MPa [160 ksi]) hooked steel fibers, also in a 1.5% volume fraction. The two connection subassemblies were subjected to displacement cycles of up to 5% drift in combination with gravity shear ratios as large as 5/8. While the connection with regular strength hooked fibers exhibited substantial punching shear-related damage at the end of the test, no significant damage could be observed in the connection with high-strength fibers. A combined shear stress due to direct shear and unbalanced moment of (1/3) √f' c (MPa) (4 √f' c [psi]) represented a limit below which a rotation capacity of at least 0.05 rad can be expected in connections constructed with either of the two fiber-reinforced concretes evaluated. In terms of gravity shear ratio, the data suggest that a gravity shear ratio of 1/2 is a safe upper limit for ensuring a minimum drift capacity of 4% drift.