Reversed lateral cyclic loading test of two flat slab specimens with punching shear stud reinforcement

An experimental campaign was conducted on the behavior of flat slab – column connections with punching shear stud reinforcement under reversed lateral cyclic loading. In this communication, the test results for two specimens are described and compared to a previously tested reference slab without shear reinforcement. The specimens had nominally identical geometry and longitudinal reinforcement, whereas the shear reinforcement differed between the two specimens only in the number of perimeters around the column (namely, three and five perimeters). Gravity load was kept constant at a value approximately equal to 55% of the Eurocode 2 nominal punching shear resistance for concentric loading without shear reinforcement for both specimens. The test setup previously developed at Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa (FCT/UNL) was used. In contrast to most test setups found in literature for these types of tests, this setup allows modelling of the flat slab with both negative and positive bending moment regions. Both specimens containing shear reinforcement sustained relatively high drift ratios, opposed to the low drift ratio attained by the reference slab without shear reinforcement. The specimen with three perimeters of studs failed in a brittle way at 4.0% lateral drift ratio. The other specimen sustained drift ratios as high as 6.0%, with a gradual loss of strength. For both specimens with shear reinforcement, the top bars at the column region yielded before the ultimate failure and the peak unbalanced moment was reached at around 3.0% drift ratio. The readings from strain gauges installed in the longitudinal and shear reinforcement revealed that diagonal cracks tended to develop through the shear studs but were effectively restricted by them.