Experimental Studies of Full-Scale Posttensioned Steel Connections

Six full-scale interior connection subassemblies of posttensioned wide flange beam-to-column moment connections were subjected to inelastic cyclic loading up to 4% story drift to simulate earthquake loading effects. Bolted top and seat angles are used in the connection, along with posttensioned high strength strands that run parallel to the beam. These strands compress the beam flanges against the column flange to develop the resisting moment to service loading and to provide a restoring force that returns the structure to its initial position following an earthquake. The parameters studied in these experiments were the initial posttensioning force, the number of posttensioning strands, and the length of the reinforcing plates. The experimental results demonstrate that the posttensioned connection possesses good energy dissipation and ductility. Under drift levels of 4%, the beams and columns remain elastic, while only the top and seat angles are damaged and dissipate energy. The lack of damage to the beams, columns, and the posttensioning enable the system to return to its plumb position (i.e., it self-centers). Closed-form expressions are presented to predict the connection response and the results from these expressions compare well with the experimental results.