Internal slab-column connections under monotonic and cyclic imposed rotations

Reinforced concrete flat slabs supported by slender columns are often used as gravity load resisting system for buildings in regions of moderate seismicity. Current codes of practice determine the displacement capacity of slab-column connections using empirical formulas which were calibrated against experimental studies. This article reviews and compares test configurations used in past experimental studies and presents the adopted configuration for an experimental investigation on 13 full-scale internal slab-column connections without transverse reinforcement. The objective of the test campaign was to assess the influence of the loading history (monotonic vs. reversed cyclic) for different gravity loads and reinforcement ratios. The study showed that cyclic loading led in particular for slabs subjected to low gravity loads to significant moment strength and deformation capacity reduction when compared to results obtained from monotonic loading tests. The effect of cyclic loading was more pronounced for slabs with low reinforcement content. The experimental results are compared to the predictions of ACI-318, Eurocode 2 and fib-Model Code 2010. All codes predict the moment strength on the safe side. For the deformation capacity of the cyclic tests, only ACI-318 provides estimates, which are, in average, accurate enough but unconservative for slabs subjected to high gravity loads.