Post-tensioned steel beam-column connections with reduced length BFRP tendons

The seismic behavior of the traditional top and seat angle beam-column connection was experimentally evaluated using a half-scaled prefabricated exterior beam-column connection subassembly. Then, an ensemble of three post-tensioned beam-column connections using reduced length basalt fiber reinforced polymer (BFRP) tendons was tested with three different tendons' post-tension (PT) force levels of 15.9, 30, and 50% of the tendons' ultimate strength. Following that, another group of three additional subassemblies containing both reduced length BFRP tendons, as post-tensioning devices, and top and seat angles, as energy dissipation (ED) devices, was tested with the same three post-tension force levels used in the previously tested group. Finally, an analytical model was proposed to capture the moment-relative rotation response of the traditional top and seat angle and the connection combining both the top and seat angles and the BFRP tendons. The results showed that connections containing BFRP tendons only, with the lowest PT force level, provided the same envelope of the top and seat angle connection, and further enhancement could be achieved by increasing the PT force level. Also, the addition of the BFRP tendons to top and seat angle connection improved the connection strength, initial stiffness, post-yield stiffness, and reduced the residual drift. In addition, the proposed analytical model predicted the moment-relative response well, which ensures the reliability of the model in designing such connections.