Dynamic Response of a RC Frame under Column Removal

Under a collapse scenario, the sudden loss of support causes a dynamic response that can amplify the internal forces in the members and lead to greater damage. This study considered a one-quarter scale, 2-bay, 2-story RC frame that was axially restrained at the beam locations. The frame was loaded with dead weights, and the support under the center column was kicked out to initiate the dynamic test. The results from four dynamic tests of a reinforced concrete frame with discontinuous reinforcement under various levels of applied load are presented. The fourth drop, with a load corresponding to 42% of the design (1.2×dead load+0.5×live load), did result in a catenary action range of response. A simple single degree of freedom (SDOF) analysis showed that there is a snap-through effect, i.e., a very fine tipping point at which the structure is pushed past the compressive arch or flexural range of response into the catenary action range of response. At this point, the loads in the structure increase significantly due to the dynamic effects.