Posttensioned Seismic-Resistant Connections for Steel Frames

TLDR

Steel moment‑resisting frames with posttensioned connections are built by post‑tensioning beams to columns using high‑strength strands. The authors added top and seat angles for energy dissipation, developed a fiber‑element analytical model calibrated with experimental tests, and used it for inelastic static and dynamic time‑history analyses of interior connection subassemblages and a six‑story steel MRF. The connection eliminates field welding, matches welded stiffness, self‑centers, limits damage to angles, and demonstrated adequate stiffness, strength, ductility, and superior seismic performance compared to typical welded MRFs.

Abstract

Steel moment-resisting frames (MRFs) with posttensioned connections are constructed by posttensioning beams to columns using high strength strands. Top and seat angles are added to provide energy dissipation and redundancy under seismic loading. This new type of connection has several advantages, including the following: (1) field welding is not required; (2) the connection stiffness is similar to that of a welded connection; (3) the connection is self-centering; and (4) significant damage to the MRF is confined to the angles of the connection. An analytical model based on fiber elements was developed for these connections. Experimental test results were used to calibrate the model. The model was used for inelastic static analyses of interior connection subassembages as well as dynamic time history analyses of a six-story steel MRF. A self-centering capability and adequate stiffness, strength, and ductility were observed in the results of these analyses. Time history analysis results show that the seismic performance of a posttensioned steel MRF subject to the earthquake records studied here exceeds the performance of an MRF with typical welded connections subject to the same earthquake records.