Seismic Behavior Of Steel Moment Connections With Single-Sided Energy Dissipating T-stubs

Steel beam-column connections have always been a key part of steel moment frames,transferring bending moment and shear force,while dissipating the earthquake energy.The 1994 Northridge Earthquake and the 1995 Kobe Earthquake,revealed that the welded steel-beam-to-column connections were not as ductile as expected.Subsequently,through numerous experimental and analytical investigations,some researchers proposed a series of types of connections to improve performance of steel moment frames,including these with weakened or strengthened connection elements.While these connections help enhance seismic performance of steel moment frames,they overall do not offer fast and convenient post-earthquake repair.This research focused on a new type of beam-to-column connection in which a buckling-restrained T-stub fuse is installed to the bottom flange of the beam.Note that the satisfactory performance of the buckling restrained T-stub fuse has been demonstrated in the Simpson Strong-Tie moment connection.Compared with the Simpson Strong-Tie moment connection and many existing types of steel moment connections,the one studied here conceptually eliminates the need to remove the reinforced concrete floor above the connection during the post-earthquake damage detection and fuse replacement process.In this paper,eleven experimental specimens were designed and tested to investigate the inelastic behavior and reparability of the connection.The test parameters included the cutting methods to develop the T-stub fuses,the shapes of the cut-outs on the T-stubs,and the different assumptions made in design of the specimens.Test results showed that the specimens properly designed can sustain the connection rotation of 0.04 rad without exhibiting the strength degradation of 20%or more.In addition to testing work,the finite element analyses of the experimental specimens were carried out in ABAQUS.The computer models were validated by the test results.Based on these models,parametric analyses were performed to investigate the influences of the coefficient of friction between the T-stub and its buckling restraining elements,the depth of the cutout in the T-stub,and widths of the gaps between the T-stub and its buckling restraining elements on performance of the connection.Further,based on the experimental results,this research proposed a simplified model for determination of the backbone response of the connection through hand calculations.The simplified model was found to be able to provide reasonable predictions for the test results.The testing described herein made use of technology and products developed and owned by Simpson Strong-Tie Company Inc.Simpson Strong-Tie Company Inc.is not affiliated with the author of this paper,and has not authorized,sponsored,or endorsed the authors of this paper in any way.This testing does not conform to the detailing requirements as set forth by Simpson Strong-Tie in AISC 358-16,Chapter 12.Therefore,the findings are those of the researchers and not Simpson Strong-Tie;nor do they reflect the performance of Simpson Strong-Tie’s proprietary Yield-Link technology when properly detailed.