Experimental investigation of progressive collapse potential of ordinary and special moment-resisting reinforced concrete frames

Two one-quarter-scaled, single-story, two-bay by one-bay, reinforced concrete (RC) building frame models-one each for ordinary and special moment-resisting frames (OMRF and SMRF) conforming to ACI 318 Building Code Requirements for Structural Concrete and Commentary-were tested for progressive collapse, with the objective of studying the difference in the response of the two schemes of reinforcement detailing. The load was applied at 100 mm/s on the failed middle column with 50 mm incremental vertical displacement in each loading cycle. The tests help to develop a better understanding of how connections in the floor systems perform when subjected to large deformations, as well as large catenary and membrane forces. The mechanical behavior of the models has been discussed and analyzed using a simplified model that may be used for the assessment of progressive collapse potential of RC building frames by incorporating the catenary mechanism. The collapse load for OMRF and SMRF models estimated by plastic mechanism was 62.8 and 75.5% of the tested failure capacity, respectively. The special reinforcement detailing of RC building frames (as done in SMRF) is found to help considerably in mitigation of the progressive collapse of building frames.