Large-scale seismic testing of knee-brace-frame

Abstract

In a knee-brace-frame (KBF), one end of the brace is connected to a short knee element instead of beam-column joint. The brace provides the required lateral stiffness, whereas the ductility is obtained through shear yielding of the knee element. Large-scale dynamic testing of a KBF with shear yielding knee is described in this paper. When a two-story KBF with rolled I-sections as knee members was subjected to base excitation through pseudo-dynamic testing, inducing a shear strain of 0.1, it was found that the KBF could dissipate a large amount of energy without any pinching in the hysteretic loops or significant deterioration in strength and stiffness provided that the knees are designed to inhibit local and lateral-torsional buckling. The test results reveal that the variation of shear stress with the shear strain in the knee could be approximated by a bilinear hysteretic curve with a strain hardening slope of 0.02-0.04. The out-of-plane displacements at the knee-brace joints and vertical displacements at the knee-beam joints are found to be small.