Gravity and Lateral Load-Carrying Capacities of Reinforced Concrete Flat Plate Systems

A total of five half-scale reinforced concrete slab-column frame specimens were tested under gravity loads or combined gravity and lateral loads. Each specimen represented a complete story of a two-bay by two-bay moment frame, in which a continuous flat plate system was used with nine columns assumed isolated at inflection points between floors. The tested variables were slab reinforcement ratio and loading history (monotonic versus reversed cyclic). The tests showed that consecutive punching failures at the slab-column connections induced transient drops in the applied load, but the load-carrying capacity of the entire system was recovered and maintained until the system completely collapsed. The amount of top and bottom slab bars and loading history affected the punching shear capacity as well as the gravity or lateral load-carrying capacity, stiffness, and ductility. Finally, the ACI 318-11 punching shear provisions were evaluated based on the test results and proved to be conservative for the tested continuous flat plate systems. The test results are important in that the test replicated real boundary conditions of inter-story flat plate systems and monitored the direct shear and unbalanced moment at each connection of the continuous systems.