Special Truss Moment Frame Component Test 7 - 2HSS8x4x1/4

Hollow structural sections (HSS) are highly efficient structural sections used in resisting compression, torsion, and bending. Their high torsional rigidity generally eliminates lateral torsional buckling; thus eliminating the need for lateral bracing in beam-type members. Consequently, the plastic rotational capacity and strength degradation rate are mainly governed by the flange local buckling and web local buckling. Prior research showed that single-HSS beam-to-column moment connections could exhibit satisfied seismic performance with small width-to-thickness ratio of the flanges. The failure was usually induced by severe flange local buckling and fracture. However the connection details by using single HSS are generally complicated. A new connection configuration consisting of double-HSS welded to column through a center gusset plate is investigated in this study. The benefits of the proposed configurations are: 1) to effectively reduce the width-to-thickness ratios (b/t) by 50% with double-HSS beam which has similar moment capacity with an equivalent single-HSS beam; 2) to provide simple and practical connection details between the beam and column. This test result showed that the proposed connection was able to sustain high member rotation before strength degradation started at 6% member drift.