Earthquake Resistant Post-Tensioned Connections to Concrete Filled HSS Columns

Large-scale subassembly tests were conducted to investigate the behavior of an innovative post-tensioned wide flange beam-to-column moment connection for steel moment resisting frames with concrete-filled HSS columns subjected to seismic loading conditions. The connection includes top and seat angles bolted to the beam and column. Strands are placed along the length of the beam, passing through the column and post-tensioned to provide a precompression of the beam against the column. The parameters investigated in the study include the angle thickness, angle gage length, beam flange reinforcing plates, connection shim plates, and post-tensioning force. The test results demonstrate that post-tensioned connections provide excellent elastic stiffness, strength, and ductility under cyclic loading, with energy dissipation occurring primarily in the angles. The connection initial elastic stiffness is comparable to that of a fully restrained welded connection. In addition, the connection has essentially no residual deformation following several cycles of inelastic story drift. Simple design models are developed and verified by the test results for estimating the connection decompression moment and moment capacity, as well as the increase in post-tensioning strand force due to connection deformation.