Hybrid Simulation of Moment Frames with Deep Columns

Wide flange steel column elements have been commonly used for steel moment frames in seismic regions. To economically comply with drift limit requirements, the moment of inertia of the section is increased by choosing slender and deep sections. However, deep columns are susceptible to local buckling and subsequent axial shortening when subjected to a combination of high axial forces and cyclic lateral loads. The interaction between the shortening columns and the surrounding structural framing system can result in a redistribution of axial loads, which has not been examined in detail. Here, this interaction is studied through a hybrid simulation of a full-scale steel moment frame subassembly using advanced hybrid simulation algorithms with new capabilities developed for this test. A new mixed displacement and force control framework is implemented to capture the coupled nature of the column axial behavior during shortening. The lateral behavior of the frame is highly dependent on the moment frame with reduced beam sections considered in this study. The experimental cruciform subassemblage includes beam-to-column connections and this measured plastic hinge response is utilized through online model updating to update parameters in the nonlinear numerical beam models. Preliminary tests are presented for these ongoing experiments.