Progressive collapse of steel moment-resisting frame subjected to loss of interior column: Experimental tests

A static push-down analysis is conducted experimentally using a 1/3 scale one-story bare steel moment frame substructure in this study. The objectives of this test include: (1) investigating the behavior of bare steel moment frame under column loss scenario; (2) validating the computational models developed for the purpose of investigating progressive collapse of steel frame structures. The contributions of collapse resisting mechanisms including flexural action and catenary action to the robustness of the system as the increase of the vertical displacement of the center column are quantified. The test results reveal that flexural action plays an important role in resisting progressive collapse along the entire loading process. However, the catenary action becomes the primary collapse resisting mechanism in the final stage of loading. Dynamic responses of the test specimen are estimated using energy-based method. It is shown the test specimen behaves elastically subjected to sudden loss of the center column and therefore progressive collapse will not occur. The dynamic increase factor is also estimated on the basis of the testing results. The analysis results suggest that catenary action has a great impact on the value of the dynamic increase factor under large deformation conditions.