Recommendations for Numerical Modelling of Concentrically Braced Steel Frames with Gusset Plate Connections subjected to Earthquake Ground Motion

In seismically active areas Concentrically Braced Steel Frames (CBFs) are commonly used in steel frame structures as an economic and effective means of both providing resistance to the lateral loading induced during... [ view full abstract ]

In seismically active areas Concentrically Braced Steel Frames (CBFs) are commonly used in steel frame structures as an economic and effective means of both providing resistance to 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 CBF’s subjected to seismic action of varying intensity.
As part of the BRACED transnational research project funded by the European Commission’s Seventh Framework Programme (FP7), a series of 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. These simulated ground motions were scaled to produce elastic response, brace buckling/yielding and ultimately brace fracture.
This recorded experimental data is used to validate a three-dimensional numerical model developed using the OpenSees seismic analysis software. Results from the experimental and numerical models are compared under the key criteria of frame acceleration, lateral drift and brace axial force. The sensitivity of the model to variations in structural and model parameters is assessed and recommendations for future numerical modelling are presented. Results indicate that model performance is sensitive to the initial brace eccentricity applied, with a value of 1.0% of overall brace length providing a more realistic representation of global frame stiffness and drift response than the lower values recommended in literature, but an underestimate of the compression resistance of the brace.