Behavior factor of concrete portal frames with dissipative devices based on carbon-wrapped steel tubes

The key element characterizing the seismic vulnerability of existing prefabricated RC structures, not designed for earthquake actions, are friction-based connections between structural members; mainly those between beams and columns and beams and roofing beams. The paper discusses the effectiveness of dissipative connectors made of carbon wrapped steel tubes. In particular, it presents the results of Incremental Dynamic Analyses on portal frames, aimed at evaluating behavior factor values to be used in design. A simplified formula for estimating the behavior factor is also proposed. Results of nonlinear IDAs suggest that the introduction of these dissipative devices in friction-based beam-column joints provides an effective connection between structural members and, in addition, reduces the forces transmitted to columns, improving the seismic behavior of the entire structure.