FULL-SCALE TESTING OF STEEL MOMENT FRAMES CRUCIFORM SUBASSEMBLIES TOWARDS SYSTEM-LEVEL BEHAVIOR ANALYSIS

Steel moment frames are commonly employed in seismic regions, with wide flange steel columns serving as essential elements in their design. Compliance with drift limit requirements updated after the 1994 Northridge earthquake has led to the frequent selection of deep slender columns, which maximize the moment of inertia of the section for more economical design. However, such columns are susceptible to experiencing local and global buckling and subsequent axial shortening when subjected to high axial forces and cyclic lateral loads. Extensive member level column tests have been performed in the past, with experimental data for subassembly or full frame configuration considering interaction with the frame more limited. This study presents experimental observations of a full-scale testing program of a cruciform beam-to-column subassemblage through quasistatic and hybrid simulation. Quasistatic tests followed standard AISC protocols with constant axial load applied ranging from 20% up to 40% of the yield capacity. Advanced hybrid simulations were also carried out to study the system behavior under DBE and MCE ground motions. A full nonlinear model was developed to interact with the physical substructure. Moreover, a new control framework was developed to enforce displacement compatibility with axial loads imposed in force-control mode accounting for axial shortening due to column buckling. Online model updating was also applied for the full-scale tests to improve numerical simulation of beam plastic hinge models by using the measured beam hysteresis of the reduced beam sections in the experimental substructures. Global and local responses of two quasistatic and two hybrid tests are presented, providing valuable data to improve the understanding of these systems through advanced testing techniques.