• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.99-108
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• 2015

The partially restrained smart CFT (concrete filled tube) column-to-beam connections with top-seat split T connections show various behavior characteristics according to the changes in the diameter and tightening force of the fastener, the geometric shape of T-stub, and material properties. This paper presents results from a systematic three-dimensional nonlinear finite element study on the structural behavior of the top-seat split T connections subjected to cyclic loadings. This connection includes super-elastic shape memory alloy (SMA) T-stub and rods to obtain the re-centering capabilities as well as great energy dissipation properties of the CFT composite frame. A wide scope of additional structural behaviors explain the influences of the top-seat split T connections parameters, such as the different thickness and gage distances of split T-stub.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.15-24
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• 2013

This paper presents the results from a systematic finite element study on the bending moment resisting capacity of double web-angle connection for a CFT(concrete filled tube) composite frame subjected to cyclic loading. The three-dimensional nonlinear finite element models are constructed to investigate the rotational stiffness, bending moment capacity, and failure modes of the partially restrained composite CFT connections. A wide scope of additional structural behaviors explain the different influences of the double web-angle connections parameters, such as the different thickness of connection angles and the gage distances of high strength steel connection bar. The moment-rotation angle relationships obtained statically from the finite element analysis are compared with those from Richard's theoretical equation.

• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.191-204
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• 2014

In this paper a systematic numerical analysis is performed to obtain the bending moment resisting capacity of a top and seat angle connection, which is a type of partially restrained connection, for a CFT composite frame subjected to cyclic loading. This partially restrained composite CFT connections are fabricated using high strength steel connection bar. The three-dimensional nonlinear finite element models are constructed to investigate the rotational stiffness, bending moment capacity, and failure modes. A wide scope of additional structural behaviors explain the different influences of the top and seat angle connection's parameters, such as the different thickness of connection angles and the gage distances of the high strength steel bar. The moment-rotation angle relationships obtained from the finite element analysis are compared with those from Richard's theoretical equation.

• Journal of Korean Society of Steel Construction
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• v.29 no.6
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• pp.423-434
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• 2017

In this paper a systematic numerical analysis is performed to obtain the hysteresis behavior of partially restrained top and seat angle connections subjected to cyclic loading. This connection includes superelastic shape memory alloy (SMA) angles and rods in order to secure the recentering capacities as well as proper energy dissipation effects of a CFT composite frame. The three-dimensional nonlinear finite element models are constructed to investigate the rotational stiffness, bending moment capacity and failure modes. A wide scope of additional structural behaviors explain the different influences of the connection's parameters, such as the various thickness of connection angles and the gage distance of steel and SMA rods.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.109-117
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• 2012

This study seeks to devise a design application for a beam structure with partially restrained composite connection to a CFT column. A cost-efficient and stable component is applied by adjusting the stiffness ratio of the column connection through partially restrained composite connection. Based on a review of the structure's stability, it was confirmed that in the case of a low-rise building as a moment frame, resistance without bracing is feasible because stiffness increased by virtue of the partial restrained composite connection by composite action. In the case of a high-rise building, lateral resistance load of moment frame was approximately 10% when proper partial restrained rate was at around 60%. With considerations related to economic efficiency, the partial restriction effect of the beam component was significantly activated by the uniform load, but that of the beam activated by concentrated load was not significantly indicative. The analysis indicated that 60% partial restrained girder at the connection was the most economical in the case of uniform load. It also showed that end moments can be reduced by approximately 25%.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.579-589
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• 2003

Most beam-to-column connections are symmetrically reinforced because of the reverse action caused by earthquakes. However, in weak-earthquake regions like Korea, asymmetrically reinforced connections could be used. In particular, the connections between concrete-filled tube (CFT) column and H-shape beam could be applied using a simplified lower diaphragm. The tensile capacity or Combined Cross Diaphragm for upper reinforcing was tested using a simple tension test. Four types for lower reinforcing combined Cross, none, horizontal T-bar, and vertical plate were tested using the ANSI/AISC SSPEC 2002 loading program. Horizontal T-bar and stud bolts in vertical flat, bar transmit tensile stress from the beam's bottom flange to filled concrete. All test specimens satisfied 0.01 radian inelastic rotational requirement in ordinary moment frame of AISC seismic provision. According to the results of the parametric studies simplified lower diaphragms demonstrated outstanding strength, stiffness, and plastic deformation capacity which could lead to more sufficient seismic performance in the field.

• Journal of Korean Society of Steel Construction
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• v.26 no.1
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• pp.55-68
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• 2014

In this study, the beam-to column connections of concrete-encased-and-filled steel tube columns were tested under cyclic loading. Two specimens using steel beams and two specimens using precast concrete beams were tested. The dimension of the column cross section was $670mm{\pm}670mm$. The beam depths were 488mm and 588mm for the steel beams and 700mm for the precast concrete beams. The longitudinal bar ratios of the precast concrete beams were 1.1% and 1.5%. For the connections to the steel beams, continuity plates were used in the tube columns. For the connections to the PC beams, couplers were used for beam re-bar connections. The test results showed that except for a specimen, deformation capacities of the specimens were greater than 4% rotation angle, which is the requirement for the Special Moment Frame. Particularly, specimens using precast concrete beam showed excellent performances in the strength, deformation, and energy dissipation.