| A self-equilibrating reaction frame, specially-designed/fabricated in response to the 1994 Northridge Earthquake, was revised (to increase stroke capacity) for the cyclic testing of beam/column sub-assemblages to investigate the moment-rotation characteristics of various moment-resisting connection configurations. Specifically, the column-side response of the extended end-plate moment connection was investigated in an effort to gain better understanding of the column limit states.;Four full-scale, "standard" extended end-plate moment connection specimens were fabricated from designs based on current Load and Resistance Factor Design (LRFD) procedures and recommendations from top researchers. These experimental specimens consisted of one strong-column/weak-beam specimen---an 8-bolt, unstiffened, extended end-plate connection (tested to re-establish the revised testing apparatus and system of instrumentation); And, three weak-column/strong-beam specimens---4-bolt, stiffened, extended end-plate connections that differed only in their column stiffener configuration. The specimens were provided with varying degrees of column stiffening, including: (1) full-depth column stiffeners; (2) half-depth column stiffeners; and, (3) no column stiffeners.;The connection specimens were cycled to "failure" using a deformation history per the SAC Phase 2 Loading Protocol. Connection performance was evaluated by plotting load vs. displacement and moment vs. rotation. In addition, column rotation, beam relative-to-column rotation, and panel zone shear deformation were evaluated to assess the system performance of the sub-assemblages.;Additionally, all of the three weak-column/strong-beam specimens were investigated using 3D finite element analysis; the hybrid models consisting of solid, shell, and beam elements. All geometric aspects were accounted for, including all welds, clips, weld-access holes, etc. The models used for the analysis were nonlinear with respect to materials and geometry. The end-plate and column flange connection interface was accurately modeled using nonlinear contact surface analysis. Material model parameters were determined from material testing of samples from all components of the actual connection specimens.;In light of both the experimental and analytical results, design recommendations were made to improve the performance of the preferred column stiffening configuration---full-depth column stiffeners. Beam-side and column-side recommendations are given for the 4-bolt, stiffened, extended end-plate connection to (1) provide beam-side energy-dissipative capacity in the moment-resisting frames utilizing extended end-plate connection in the form of plastic hinge formation within the beam section; and (2) increase economy of steel design by maximizing the potential of the material through limiting the need to increase the global column wide-flange member size.;Key words. 1994 Northridge Earthquake, cyclic beam test, steel connection research, steel beam/column sub-assemblage, moment-rotation characteristics, moment-resisting connections, extended end-plate moment connection, column rotation, panel zone shear deformation/distortion, column-side response, column limit states, strong-column/weak-beam, weak-column/strong-beam, column stiffening, column stiffeners, continuity plates. |
