Recommendations for numerical modelling of concentrically braced steel frames with gusset plate connections subjected to earthquake ground motion

Abstract

Concentrically Braced Steel Frames (CBFs) are commonly used as an economic and effective means of resisting the lateral loading induced during earthquakes and limiting the associated displacements. Here, an integrated experimental and numerical approach is taken to investigate the performance of CBFs subjected to seismic action of varying intensity. As part of the BRACED transnational research project, shake table experiments on full-scale single-storey CBFs recorded the response of test frames employing various combinations of bracing member sizes and gusset plate connection details to simulated ground motions scaled to produce elastic response, brace buckling/yielding and ultimately brace fracture. This recorded experimental data is used to validate a numerical model developed using the OpenSees seismic response analysis software. Key experimental and numerical model responses are compared. The sensitivity of the model to variations in modelling parameters is assessed and recommendations for future numerical modelling are presented. Results indicate model performance is sensitive to the initial camber applied to the brace members, with a value of 0.8% of overall brace length observed to achieve a more accurate representation of global frame stiffness and drift response than the lower values previously recommended in literature, but an underestimate of the compression resistance of the brace.