BEHAVIOUR OF KNEE-BRACE-FRAME UNDER SEISMIC LOADINGS

Abstract

A new structural framing system, called the knee-brace-frame (KBF), with shear yielding knee is presented in this thesis for possible application in earthquake resistant design. This is a new braced framing system where one end of the brace is connected to a short knee member instead of a beam-column joint. The brace provides the required lateral stiffness whereas the ductility is obtained through shear yielding of the knee element. During severe seismic motion, the knee element acts as a ductile fuse, which yields in shear, whereby brace buckling or yielding of beams and columns is prevented. In order to study the behavior of this new system under earthquake loadings, a single storey and a two storey frames were designed, fabricated and tested using the pseudodynamic test method. The experimental results reveal that the KBF possesses the necessary stiffness, strength and ductility for seismic resistant design. A minimum displacement ductility of six for the KBF structure can be obtained, prior to the failure of the knee element when the latter is designed against lateral torsional buckling and local buckling. The experimental results were found to be in good agreement with the analytical results based on simple shear yielding beam element.