Seismic Design Of Braced FrameGusset Plate Connections

Abstract

Steel concentrically braced frames (CBFs) are stiff and strong and are an economical method to control damage during small, frequent seismic events. During severe, infrequent earthquakes, CBFs develop inelastic deformation through axial tensile yielding and post-buckling deformation of the brace. The inelastic deformation demands of the brace places severe force and deformation demands on the gusset plate connections. As such, the frame response depends on the connection response as well. To better understand the frame response of CBF systems, an analytical and experimental research study into the seismic performance of CBFs with an emphasis on better understanding the response and design of gusset plate connections is underway. The research examines the yield mechanisms and failure modes encountered in the design of gusset plate connections. To achieve a more balanced design which better distributes yielding throughout the system, a design procedure that provides economical design and good seismic performance by balancing the yield mechanisms and failure modes is proposed. Experimental research to evaluate the proposed procedures is underway. This experimental program is described, and initial test results are summarised. Complementary theoretical studies are used to establish mathematical models to estimate the connection properties and to perform parametric studies to better understand the influence of the connection on the frame response.