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SUMMARYThe seismic performance of post-tensioned steel connections for moment-resisting frames was examined experimentally and analytically. Cyclic tests were conducted on three full-scale subassemblies, which had two steel beams post-tensioned to a concrete-ÿlled tube (CFT) column with high-strength strands to provide recentring response. Reduced ange plates (RFPs) welded to the column and bolted to the beam ange were used to increase the dissipation of energy. Test results indicated that (1) the proposed buckling-restrained RFP could dissipate energy in axial tension and compression, (2) the subassemblies could reach an interstorey drift of 4% without strength degradation, and (3) buckling of the beam occurred towards an interstorey drift of 5%, causing a loss of the strand force, the recentring response, and the moment capacity. A general-purpose non-linear ÿnite element analysis program (ABAQUS) was used to perform a correlation study. The behaviour of the steel beam under both post-tensioning and exural loadings was compared to the test results and predictions.

SUMMARYTwo ungrouted post-tensioned, precast concrete-ÿlled tube (CFT) segmental bridge columns were tested under lateral cyclic loading to evaluate the seismic performance of the column details. The specimens included a load stub, four equal-height circular CFT segments, and a footing. Strands were placed through the column and post-tensioned to provide a precompression of the column against the footing. One specimen also contained energy-dissipating devices at the base to increase the hysteretic energy. The test results showed that (1) both specimens could develop the maximum exural strength at the design drift and achieve 6% drift with small strength degradation and residual displacement, (2) the proposed energy-dissipating device could increase energy dissipation in the hysteresis loops, and (3) the CFT segmental columns rotated not only about the base but also about the interface above the bottom segment. This study proposed and veriÿed a method to estimate the experimental exural displacement using two plastic hinges in the segmental column.

SUMMARYThis paper first presents the force-deformation relationship of a post-tensioned (PT) steel beam-to-column connection constructed with bolted web friction devices (FDs). This paper then describes the test program conducted in the National Center for Research on Earthquake Engineering, Taiwan, on four bolted FDs and four full-scale PT beam-to-column moment connection subassemblies using the FDs. Tests confirm that (1) the hysteretic behavior of four bolted FDs is very stable, (2) the friction coefficient between the steel plate and the brass shim is about 0.34, (3) the proposed force-deformation relationships reasonably predict the experimental responses of the PT connections under cyclically increasing deformations up to a beam peak rotation of 0.05 rad, and (4) the decompression moments do not degrade as beam cyclic deformations increase.

SUMMARY The design of a three‐story buckling‐restrained braced frame (BRBF) with a single‐diagonal sandwiched BRB and corner gusset was evaluated in cyclic tests of a one‐story, one‐bay BRBF subassembly and dynamic analyses of the frame subjected to earthquakes. The test focused on evaluating (1) the seismic performance of a sandwiched BRB installed in a frame, (2) the effects of free‐edge stiffeners and dual gusset configurations on the corner gusset behavior, (3) the frame and brace action forces in the corner gusset, and (4) the failure mode of the BRBF under the maximum considerable earthquake level. The subassembly frame performed well up to a drift of 2.5% with a maximum axial strain of 1.7% in the BRB. Without free‐edge stiffeners, the single corner gusset plate buckled at a significantly lower strength than that predicted by the specificationof American Institute of Steel Construction (2005). The buckling could be eliminated by using dual corner gusset plates similar in size to the single gusset plate. At low drifts, the frame action force on the corner gusset was of the same magnitude as the brace force. At high drifts, however, the frame action force significantly increased and caused weld fractures at column‐to‐gusset edges. Nonlinear time history analyses were performed on the three‐story BRBF to obtain seismic demands under both design and maximum considerable levels of earthquake loading. The analytical results confirmed that the BRB and corner gusset plate achieved peak drift under cyclic loading test. Copyright © 2011 John Wiley & Sons, Ltd.

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SUMMARYSix cyclic tests were conducted on three full-scale subassemblies to investigate the behavior of interior beam-to-column post-tensioned (PT) connections. Strands were placed along each side of the steel beam web, passing through the steel column to provide precompression between the beams and a column. Top and bottom energy-dissipating (ED) bars, passing through the column and welded to the beam, were used to increase the moment capacity and ED capacity of the connection. One of the subassemblies also had a composite concrete slab with discontinuity at the column centerline to eliminate restraint from the metal deck, reinforcement, and welded wire mesh. The objectives of this paper were to investigate the following: the durability of the connection by loading each specimen twice, the ED capacity of the ED bar, and the effects that the type of ED bar and type of composite slab have on the self-centering behavior of the connection. The experimental results showed that: (1) the connection could sustain severe inelastic cyclic loading at least twice without strength degradation, (2) the ED capacity of the bar was much larger than that dissipated by a single AISC loading protocol, and (3) a specimen with a discontinuous composite slab, which opened freely at the centerline of the column, ensured the same self-centering hysteretic behavior as the bare steel specimen. However, the decompression moment of the PT connection decreased significantly at each interstory drift, resulting in an early opening of a gap at the beam-column interface.