The Disposable Knee-bracing Technique in Steel Frames

A new technique of lateral bracing of steel-framed structures has been suggested by this writer. This technique, denoted as the Disposable Knee Bracing (DKB), combines two elements—the knee element and the diagonal brace element. The diagonal brace element, whose primary function is to provide the required level of lateral stiffness to the frame, is simply connected to an inclined knee member. The knee-brace member, which is rigidly connected at the ends, is designed to be the first line of dissipation of energy during severe earthquakes without significantly decreasing the lateral stiffness or strength of the frame. This energy dissipation is achieved by the formation of flexural hinges at the ends and midspan of the knees. The knee members should yield by fully developing three plastic hinges prior to any occurrence of yielding elsewhere in the frame during severe earthquakes, so that, during more destructive after shocks the second line of defense, the frame itself, might yield. Further details of this technique are presented elsewhere.