Design and seismic response of shear critical eccentrically braced frames

This paper describes a study of eccentrically braced framed structures to evaluate the response to seismic load. Attention is restricted to frames with shear critical links. Design procedures are first described and the designs of eight-storey structures for Canadian seismic zones 3 and 5 are obtained. A 16-storey structure for Zone 5 is also considered. The seismic response of these structures to a series of earthquake records is described. It was found that, for a number of ground motions corresponding to Zone 5, forces and deformations developed in the upper storeys of the frames exceeded those anticipated in the design process. The result of this is that some column and brace capacities in the uppermost storeys may be inadequate. A modification to the design process overcome this deficiency is proposed. This uses an iterative process incorporating the evaluation of dynamic response in the selection of members, and the resulting structures exhibit greatly improved behaviour.