Posttensioned seismic-resistant connections for steel frames

Steel moment-resisting frames (MRFs) with posttensioned connections are con structed by post tensioning beams to columns using high strength strands. T op and seat angles are added to provide energy dissipation and redundancy u nder seismic loading. This new type of connection has several advantages, i ncluding the following: (1) field welding is not required; (2) the connecti on 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 cal ibrate the model. The model was used for inelastic static analyses of inter ior connection subassembages as well as dynamic time history analyses of a six-story steel MRF A self-centering capability and adequate stiffness, str ength, and ductility were observed in the results of these analyses. Time h istory analysis results show that the seismic performance of a posttensione d steel MRF subject to the earthquake records studied here exceeds the perf ormance of an MRF with typical welded connections subject to the same earth quake records.