Christopoulos et al. 2002
The authors evaluate the seismic performance of a post-tensioned energy-dissipating (PTED) connection for steel frames experimentally and analytically. High strength post-tensioned bars and energy-dissipating bars are used at connections in an attempt to provide for a ductile connection and avoid some of the fracture stiffness of welded connections, while providing self-centering capabilities for the system. Non-linear time-history dynamic analysis was performed on the analytical model. Component testing was performed on the energy-dissipating bars, as well as a test of a beam to column connection.
System Concept
This connection type is meant to dissipate energy through energy-dissipating bars and self-center through post-tensioning. Energy-dissipating bars are inserted into steel cylinders to prevent buckling, and attached to the beams and columns of the frame through welded couplers. When the beam rotates, the energy-dissipating bars deform inelastically in compression or tension, providing a mechanism for dissipating energy. Post-tensioned bars through the beam and connected to each column then self-center the structure.
Experimental Study, Results and Discussion
Component testing was conducted on the energy-dissipating bars with the goals in mind to assess the tension-compression cycles of the bar, to ensure that welded couplers were sufficient to develop the full axial strength of the bars, and to see if the confinement cylinders could prevent buckling of the energy-dissipating bars. A cyclic test was also performed on a beam to column connection for an inter-story drift of 5%.
It was found that the energy-dissipating bars were able to yield in axial tension and compression, and that they effectively dissipated energy. The post-tensioning was then able to self-center the structure. Large deformations were achieved without damaging the rest of the frame.
Analytical Study
An analytical study was undertaken to develop the relationship between moment and rotation of the PTED connection. The developed model was able to accurately predict the behavior of the connection and outlined procedures for designing post-tensioning and energy-dissipating bars for the PTED.
Reference
Christopoulos, C., Filiatrault, A., Uang, C., and Folz, B. (2002). "Posttensioned Energy-dissipating Connections for Moment-Resisting Steel Frames," Journal of Structural Engineering, 128.9, pp. 1111.