Experimental study on progressive collapse-resistant behavior of reinforced concrete frame structures

A static experimental study to investigate progressive failure of a reinforced concrete frame due to the loss of a lower story column is described. A four-bay and three-story one-third scale model representing a segment of a larger planar frame structure was tested. A constant vertical load was applied to the top of the middle column by a servo-hydraulic actuator to simulate the gravity load of the upper floors and the failure of the middle column of the first story was simulated by unloading a mechanical jacking system. The frame collapse, defined in this study as the rupture of tension steel bars in the floor beams, occurred at a vertical unloading displacement of 456 mm (18 in.) that corresponds to a beam drift angle (rotation with respect to the horizontal) of 10.3 degrees. Based on the experimental observations, the mechanical behavior of the model frame is analyzed and the redistribution and transition of the load resisting mechanisms is discussed. It is concluded that the calculated capacity of the frame based on the plastic limit state was approximately 70% of the tested failure capacity if catenary effects are also included.