Influence of connection design parameters on the seismic performance of braced frames

Special concentrically braced frames (SCBFs) are commonly used lateral-load resisting systems in seismic design. In SCBFs, the braces are connected to the beams and columns by gusset plate connections, and inelastic deformation is developed through tensile yielding and inelastic post-buckling deformation of the brace. Recent experimental research has indicated that the seismic performance of SCBFs can be improved by designing the SCBF gusset plate connections with direct consideration of the seismic deformation demands and by permitting yielding in the gusset plate at select performance levels.Experimental research provides important information needed to improve SCBF behavior, but the high cost of experiments limits this benefit. To extend and better understand the experimental work, a companion analytical study was conducted. In an earlier paper, the inelastic finite element model and analysis procedure were developed and verified through detailed comparison to experimental results. In this paper, the model and analytical procedure extend the experimental results. A parametric study was conducted to examine the influence of the gusset plate and framing elements on the seismic performance of SCBFs and to calibrate and develop improved design models. The impact of the frame details, including the beam-to-column connections, the brace angles, and their inelastic deformation demands, was also explored. The results suggest that proper detailing of the connections can result in a large improvement in the frame performance.