Experimental studies of 3D RC substructures under exterior and corner column removal scenarios

In a cast in-situ reinforced concrete (RC) beam-slab system, concurrent development of secondary mechanisms, i.e. catenary action in beams and tensile membrane action in slabs, may significantly increase load-carrying and deformation capacities of structures under missing column scenarios. Previous researches mainly focused on structural behaviour of individual RC beams, slabs or beam-slab systems, without clearly defining structural interactions among slabs, beams and columns. To obtain a better understanding of these complex interactions, a systematic study starting from RC skeletal frames and culminating in frame-slab systems is conducted under corner and exterior column removal scenarios, which are among the most critical scenarios for analysis of structural resistance towards progressive collapse. Four specimens were included in this programme, i.e. under corner column loss event, one skeletal frame (COR) and one frame-slab (S-COR) specimens were tested to failure, while one skeletal frame (EXT) and one frame-slab (S-EXT) specimens were loaded to collapse under exterior column loss scenario. In 3D beam-slab tests, it is very challenging to design a test setup with complete measurements of all support reactions due to a great number of statical indeterminacies. The novelty of the paper is to address this aspect. Through the proper test setup and instrumentation of structural behaviour of RC 3-D skeletal frames under corner and exterior column loss scenarios, interactions between the columns and beams could be elucidated. In turn, the slab contributions could be isolated and quantified through direct comparisons between skeletal frame and frame-slab specimens for both scenarios.