Seismic design of columns in two-story steel concentrically braced frames with bracing members intersecting columns between floors

Abstract

A new seismic design method is proposed for the columns in two-story steel concentrically braced frames with bracing members intersecting columns between the floors. The method is intended to improve the stability of braced frame columns taking into account the interaction between the stories when the braces respond in the inelastic range. Furthermore, the proposed method aims to prevent excessive inelastic deformation in the braces intersecting columns between the floors considering the interaction between the stories, which otherwise may lead to brace fracture. The proposed design method is first presented in the framework of the North American steel design standards, followed by a design example to illustrate the method. Dynamic analyses are then performed to validate the design method and evaluate the seismic performance of the frame designed with and without the consideration of the method. The adequacy of the proposed method is assessed using further dynamic analyses when the location of the weakest braced panel is altered, oversized braces are used, and column orientation is changed. The results show that the proposed method can appropriately predict the column design forces, prevent column instability taking into consideration the interaction between inelastic brace responses in adjacent stories, thus improving the seismic response of the braced frame.