SEISMIC RESPONSE OF BEAM-COLUMN KNEE CONNECTIONS

Four knee joints were constructed and tested. The difference between the specimens was the connection detail. For three of the test specimens, beam and column longitudinal bars were mechanically attached to a structural steel section embedded in the joint region. The fourth specimen was a typical conventionally reinforced knee joint. The type of anchors used for the test specimens would facilitate field installation. All of the test specimens exhibit lower stiffness and load-carrying capacity when the joint is opened. This difference is more pronounced for the conventionally reinforced specimens. The response of the specimens under closing moments is similar for drifts up to 2.4 percent of interstory height. The behavior is quite different under opening moments. At the interstory drift corresponding to 0.6 percent of story height, the load resisted by the conventionally reinforced specimen drops to 70 percent of that resisted by the specimens with composite details. For composite specimens, a larger portion of the total energy was dissipated through beam flexural deformation. The failure of the conventionally reinforced specimen was due to excessive damage in the joint region. The connections with composite details failed as a result of formation of "plastic hinges" in the beams, whereas excessive damage to the connection region of the conventionally reinforced specimen lead to failure.