Punching of reinforced and post-tensioned concrete slab-column connections

Data collected from shaketable tests of two, approximately 1/3-scale, two-story flat plate frames using shear reinforcement, as well as data from previous tests, were evaluated to assess the interstory drift ratios when punching failures occur for reinforced concrete and post-tensioned slab-column connections with and without shear reinforcement. The drift ratios at punching failures for the two shaketable specimens were approximately equal to values reported for quasi-static tests of isolated specimens without shear reinforcement; but substantially less than reported for quasi-static tests of connections with shear reinforcement. The review of test results indicates that the bilinear relation for lateral drift versus gravity shear ratio to assess the need for shear reinforcement at slab-column connections approved for ACI 318-05, Section 21.11, is generally conservative for typical connections of all connection types. The data also were used to assess parameters required for a simple shear-strength degrading model for slab-column. connections.