Full-Scale Beam-To-Column Subassemblage Testing for Seismic Evaluation of Deep Columns

Abstract

Steel moment frames composed of wide-flange steel members are commonly used in seismic regions, with deep and slender column sections often selected to economically satisfy drift limit requirements. The section slenderness makes the columns more susceptible to local and global buckling and subsequent axial shortening when subjected to combined high axial forces and lateral deformations. Numerous tests have been conducted on individual column members under a wide range of axial loads and loading patterns. Experimental data of subassembly or complete frame configurations providing insight into system level interaction of the column with the frame are more limited. To address this concern, a full-scale testing program was conducted on four cruciform beam-to-column subassemblage subjected to loading patterns based on cyclic quasi-static and slow hybrid simulation. Quasi-static tests followed standard AISC loading protocol with constant column axial load ranging from 20% to 40% of the yield capacity. Advanced hybrid simulations subjected the specimens to realistic earthquake loading patterns to levels consistent with design basis earthquake (DBE) and maximum considered earthquake (MCE) ground motions. A full nonlinear model of a complete 6-story frame was developed for the numerical substructure in the hybrid simulation. The observed local and global responses of two quasi-static and two hybrid tests are presented, providing valuable data towards improving the understanding of progress of damage for these systems through advanced testing techniques.