Seismic design and behavior of post-tensioned steel connections including effects of a composite slab

Three series of six full-scale, cyclic tests on post-tensioned (PT) beam-to-column connections were conducted to evaluate the cyclic performance. Each specimen represented an interior connection with steel beams PT to a column; one specimen also incorporated a composite slab. Reduced Flange Plates (RFPs) were added at the beam-to-column interface for energy dissipation, and flange reinforcing plates were provided outside the beam flanges to minimize yielding upon decompression. This paper describes the durability of the proposed connection, the effects of web stiffeners on beam local buckling, and the interaction of a composite slab. The first test series demonstrated that as long as beam yielding could be prevented before an interstory drift of 4%, the PT connection was capable of reaching an interstory drift of 5% or experiencing the AISC seismic loads twice without beam buckling. The second test series showed that beam buckling could be prevented by utilizing web stiffeners instead of increasing the length of the flange reinforcing plate. The third test series included a matched pair of specimens, one bare steel beam and one including a composite slab. Results that emphasize the influence of the composite slab on re-centering behavior and specific comments on the slab response were presented. The presence of a composite slab corresponded to higher-achieved moments due to the tensile capacities of the metal deck flutes, wire mesh, and longitudinal reinforcement, which were placed parallel to the PT beam. However, the re-centering behavior could be maintained after fractures of the wire mesh in the proposed slab details. Estimates of beam moments considering the presence of a composite slab were presented based on the cyclic test results.