Robustness of Reinforced Concrete Slab Structures: Lessons Learned from Two Full-Scale Tests

Within the research project ITSAFE, two full-scale structures were built, one consisting of a single-storey, two-span, 7.00 × 14.00 m2 RC frame with a solid slab and another consisting of a two-storey, 7.00 × 7.00 m2 RC frame with solid slabs. In the two-span frame, one of the central supports was first demolished using a pneumatic hammer, resulting in rather limited damage (a 14–15 cm deflection at the removed support location). However, torsional cracks appeared at the interface between a column and slab in one of the outer supports. When the second central support was removed, the structure collapsed with the failure of the support–slab connection. The same type of cracking was observed in the two-storey structure, where the column removal was dynamic, and a 22 cm deflection was measured. These experimental results question current practice in which, for internal supports, alternative load path mobilizing membrane forces in the slab are said to prevent their collapse, or in the cases of edge and corner columns, rupture line analysis is used and suggests that special reinforcement at the column–support connection is also needed to prevent the premature failure of the structure.