Shake table tests and analytical studies of reinforced and post -tensioned concrete flat plate frames

Use of flat plate floor systems consisting of a conventional or post-tensioned reinforced concrete slab-column system incorporating shear reinforcement within the slab-column connection region has become increasingly popular for non-participating systems in high seismic zones. However, relatively sparse experimental data are available to assess the dynamic responses and performance of such systems, particularly for post-tensioned systems. To address these gaps, shake table tests of two, approximately one-third scale, two-bay by two story flat plate frames with shear (stud-rails) reinforcement were conducted. One of the specimens consisted of a conventional reinforced concrete flat plate (RC specimen), whereas the other specimen consisted of nominally reinforced flat plate with post-tensioning reinforcement (PT specimen). The specimens were subjected to gravity loads and increasing intensity of uniaxial base acceleration histories. The shear reinforcement in the tested specimens limiting punching damage compared with tests (by others) on specimens without shear reinforcement. The post-tensioned slab-column frames performed well, verifying that this commonly used system is effective. Although slab-column punching failures occurred during the tests, lateral drift ratios of approximately 3% and 4% were achieved during testing for the RC and PT frames, respectively, with relatively little loss of lateral load capacity. The inter-story drift ratios at which punching failures occurred were evaluated. The present results on gravity stress ratios and lateral drift ratios at punching were compared to prior studies to assess the influence of test parameters on the punching shear capacity of the connections. The drift ratios at punching failures for the specimens tested were substantially less than reported for quasi-static tests of isolated connections, possibly due to loss of interface shear capacity at the slab-column connection. (Abstract shortened by UMI.).