Hybrid collapse test of steel columns with nonlinear frame substructuring and force redistribution

A hybrid test method that uses the nonlinear static (pushover) analysis to examine the static force-deformation response of building structures is presented. The ultimate performance of the columns at the base of steel moment-resisting-frames (MRFs) is evaluated experimentally considering force redistribution due to the failures of panel zones and beams. The test method combines static sub-structuring techniques and finite element analysis methods. The behavior of the steel MRF is simulated by the finite element analysis program ABAQUS, while the first story column is physically tested online. Three actuators are used to simulate the physical continuity between the analytical and experimental substructures by controlling the axial load, the drift angle, and the bending moment distribution along the column length. A square tubular steel column was tested as apart of a five-storey five-bay steel MRF. The frame was deformed to a roof drift equal to 12% using pushover analysis that incorporates a novel mixed force/displacement controlling algorithm. The measured storey drift for the tested column was almost 30.0%. The test system ensured realistic loading and boundary conditions to the column sub-structure, which was tested in full interaction with the MRFs until global frame collapse. The frame deformed in a collapse mechanism that involved the first two storeys.