Analytical performance simulation of special concentrically braced frames

The properties of special concentrically braced frames (SCBFs) enable them to be designed to meet performance-based seismic design (PBSD) criteria. SCBFs have large stiffness and strength to meet serviceability performance states. Life-safety and collapse-prevention PBSD limit states are controlled by inelastic postbuckling and tensile yield deformation of the brace. In SCBF construction, the braces are connected to the frame using gusset plates. Inelastic deformation of the brace places severe inelastic demands on gusset-plate connections. To improve the understanding and design of the seismic performance of SCBF connections, a coordinated analytical and experimental research study was undertaken. This paper describes the analytical component and includes a brief description of the experimental results, which were used in the development and validation of the model. The validated model was used to evaluate the inelastic performance of structural elements and to determine the frame ductility and concentration of plastic strains at potential locations of member or weld tearing or fracture. Detailed comparisons between experimental observations and computed results show that the analyses provided good correlation to actual behavior. The results were used to develop a methodology to predict tearing or cracking of key elements in the frame.