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

Chou, Chung‐Che; Wang, Yu-Chi; Chen, Jun-Hen

doi:10.1016/j.engstruct.2008.04.013

Cited by 44 publications

(50 citation statements)

References 6 publications

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“…This failure mode, which resulted in loss of the initial beam strand force by 13%, was never observed in prior beamto-column connection tests [10,13]. Vertical stiffeners were welded to the beam flange inner side and web to reinforce the beam compression toe, so the frame could be retested.…”

Section: Test Resultsmentioning

confidence: 88%

“…On the other hand, the post-yielding stiffness ratio and the energy dissipation factor for PT connections (Table I(c)) were within the ranges (0.1 0.150, 7 1.0) suggested by Kim [7]. Following the connection design procedure proposed by Chou et al [10], the connection moment at a drift of 4%, M 4% , reached about 0.9 M np at the column face, M R ≈ 0.3M np of which was provided by the RFPs and M ST ≈ 0.6M np of which was provided by the strands (Table I(b)):…”

Section: Introductionmentioning

confidence: 87%

“…The specified 28-day concrete strength, f cn , was 28 MPa. A572 Grade 345 (50) steel was used for the steel beams, and ASTM A416 Grade 270 strands were passed along the beam webs and anchored outside the exterior columns CL and CR ( Figure 2 ST and RFPs M d,R , which was computed based on the axial force (smaller than the yield force) in the RFPs at the onset of gap-opening and the distance between the top and bottom RFPs [10,13]. The decompression moment was larger than the moments due to dead load and live load and was slightly smaller than the moment demand M dem [3].…”

Section: Introductionmentioning

confidence: 99%

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Column restraint in post‐tensioned self‐centering moment frames

Chou

Chen

2009

Earthq Engng Struct Dyn

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SUMMARYGaps between beam-to-column interfaces in a post-tensioned (PT) self-centering frame with more than one column are constrained by columns, which causes beam compression force different from the applied PT force. This study proposes an analytical method for evaluating column bending stiffness and beam compression force by modeling column deformation according to gap-openings at all stories. The predicted compression forces in the beams are validated by a cyclic analysis of a three-story PT frame and by cyclic tests of a full-scale, two-bay by first-story PT frame, which represents a substructure of the three-story PT frame. The proposed method shows that compared with the strand tensile force, the beam compression force is increased at the 1st story but is decreased at the 2nd and 3rd stories due to column deformation compatibility. The PT frame tests show that the proposed method reasonably predicts beam compression force and strand force and that the beam compression force is 2 and 60% larger than the strand force with respect to a minor restraint and a pin-supported boundary condition, respectively, at the tops of the columns. Therefore, the earlier method using a pin-supported boundary condition at upper story columns represents an upper bound of the effect and is shown to be overly conservative for cases where a structure responds primarily in its first mode. The proposed method allows for more accurate prediction of the column restraint effects for structures that respond in a pre-determined mode shape which is more typical of low and mid-rise structures.

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Section: Test Resultsmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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Column restraint in post‐tensioned self‐centering moment frames

Chou

Chen

2009

Earthq Engng Struct Dyn

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“…For the beam under either positive bending or negative bending, the openings in the composite specimen are similar to those in the bare steel specimen. Therefore, the proposed slab details improve the self-centering behavior of a PT connection with a continuous composite slab, which provides some restraint due to longitudinal reinforcement and wire mesh across the beam-column interface [13].…”

Section: Effects Of a Composite Slabmentioning

confidence: 99%

“…This restraint increased negative bending moments on the order of 40-50% compared with the bare steel subassembly, resulting in loss of self-centering capabilities. A later study [13] showed that the self-centering behavior is maintained if deck flutes are discontinuous at the column centerline and the connection moment contributed by longitudinal reinforcement is considered in design. Since the steel wire mesh, longitudinal reinforcement, and concrete were placed across the column centerline, the slab opened at a medium-to-high story drift after the wire mesh fractured.…”

Section: Introductionmentioning

confidence: 98%

Self‐centering steel connections with steel bars and a discontinuous composite slab

Chou

Tsai

Yang

2008

Earthq Engng Struct Dyn

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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.

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Seismic design and shake table tests of a steel post-tensioned self-centering moment frame with a slab accommodating frame expansion

Chou¹,

Chen²

2011

Earthquake Engng. Struct. Dyn.

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Post-tensioned (PT) self-centering moment frames were developed as an alternative to welded momentresisting frames (MRFs). Lateral deformation of a PT frame opens gaps between beams and columns. The use of a composite slab in welded MRFs limits the opening of gaps at the beam-to-column interfaces but cannot be adopted in PT self-centering frames. In this study, a sliding slab is used to minimize restraints to the expansion of the PT frame. A composite slab is rigidly connected to the beams in a single bay of the PT frame. A sliding device is installed between the floor beams and the beams in other bays, wherever the slab is allowed to slide. Many shaking table tests were conducted on a reduced-scale, two-by-two bay one-story specimen, which comprised one PT frame and two gravitational frames (GFs). The PT frame and GFs were self-centering throughout the tests, responding in phase with only minor differences in peak drifts that were caused by the expansion of the PT frame. When the specimen was excited by the 1999 Chi-Chi earthquake with a peak ground acceleration of 1.87g, the maximum interstory drift was 7.2% and the maximum lateral force was 270 kN, equal to 2.2 times the yield force of the specimen. Buckling of the beam bottom flange was observed near the column face, and the initial post-tensioning force in the columns and beams decreased by 50 and 22%, respectively. However, the specimen remained self-centering and its residual drift was 0.01%. Figure 1. (a) PT connection and (b) flag-shaped hysteretic behavior.of an MRF with PT connections exceeds the performance of an MRF with typical welded connections [12,13].Although the newly developed PT connection provides satisfactory cyclic performance, Kim and Christopoulos [13] and Garlock et al. [14,15] raised the issue of how columns and slabs restrainted PT frame expansion. Gap opening at the beam-to-column interfaces causes an expansion of the PT frame. The column and slab restraints that oppose the frame expansion affect the compression force in the PT beam. Kim and Christopoulos [13] suggested an approximate approach to estimate the restraint, which is appropriate in cases where a more concentrated response occurs at a single floor alone and overly conservative in cases where the structure responds in its fundamental mode. For a PT frame that responds in its fundamental mode, Chou and Chen [16] proposed a method for evaluating the restraint that considered the continuity and boundary conditions of the column. The method requires a structural analysis of the column in a deformed configuration and equations that are derived from the compatibility of deformation of beams, strands, and columns.When gaps open at the beam-to-column interfaces, the concrete slab, if it does not open near the columns, restrains frame expansion, affecting the self-centering [17]. Garlock et al. [14,15] and King [10] suggested that the collector beams or bays transfer the inertial force into the PT frame and accommodate PT frame expansion. Kim and Christopoulos [13] proposed detail...

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

Cited by 44 publications

References 6 publications

Column restraint in post‐tensioned self‐centering moment frames

Column restraint in post‐tensioned self‐centering moment frames

Self‐centering steel connections with steel bars and a discontinuous composite slab

Seismic design and shake table tests of a steel post-tensioned self-centering moment frame with a slab accommodating frame expansion

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