Seismic Performance Assessment of Flat Plate Floor Systems

An investigation into the lateral load response of reinforced concrete flat plate frames utilizing stud rails for shear reinforcement at the slab - column connections was carried out. The two by two bay, two story specimens were approximately one-third scale representations of typical slab - column frames constructed in moderate-to-high seismic zones in the United States. 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 on the shake table at the Earthquake Engineering Research Center at UC Berkeley's Richmond Field Station. During testing, data were collected from 193 channels and five or six video cameras to assist in assessing the behavior of the specimens.

Although slab-column punching failures occurred during the tests, lateral drift ratios of 3% and 4% were achieved for the RC and PT frames, respectively, with relatively little loss of lateral load capacity. Analytical models including column cracking, and based on using an effective slab width model with an effective width factor a of 0.8 and 0.65 and a cracking factor fl of 1/3 and 1/2 for the RC and PT specimens, respectively, resulted in good correspondence between experimental and experimental responses for low-to-moderate levels of shaking. Base shear versus top level displacement relations for the analytical models also captured the nonlinear envelop responses for the more intense shaking levels reasonably well.

Overall, the results indicate that the slab - column frames can be designed to have sufficient drift capacity to be used as a non-participating frame, or as a primary lateral force resisting system in low-to-moderate seismic regions.