• Title/Summary/Keyword: weak-axis

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Cyclic testing of weak-axis steel moment connections

  • Lee, Kangmin;Li, Rui;Jung, Heetaek;Chen, Liuyi;Oh, Kyunghwan
    • Steel and Composite Structures
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    • v.15 no.5
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    • pp.507-518
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    • 2013
  • The seismic performance of six types of weak-axis steel moment connections was investigated through cyclic testing of six full-scale specimens. These weak-axis moment connections were the column-tree type, WUF-B type, FF-W type, WFP type, BFP-B type and DST type weak-axis connections. The testing results showed that each of these weak-axis connection types achieved excellent seismic performance, except the WFP and the WUF-B types. The WFP and WUF-B connections displayed poor seismic performance because a fracture appeared prematurely at the weld joint due to stress concentrations. The column-tree type connection showed the best seismic behavior such that the story drift ratio could reach 5%.

Cyclic performance and design recommendations of a novel weak-axis reduced beam section connection

  • Lu, Linfeng;Xu, Yinglu;Liu, Jie;Lim, James B.P.
    • Steel and Composite Structures
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    • v.27 no.3
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    • pp.337-353
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    • 2018
  • In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, a, the length of the reduced beam section, b, and the cutting depth of the reduced beam section, c, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter a is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters b and c can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

Mechanical performance of a new I-section weak-axis column bending connection

  • Lu, Linfeng;Xu, Yinglu;Lim, James B.P.
    • Steel and Composite Structures
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    • v.26 no.1
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    • pp.31-44
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    • 2018
  • This paper reports a novel steel beam-to-column connection suitable for use in the weak axis of I-section column. Monotonic and cyclic loading experimental investigations and numerical analysis of the proposed weak-axis connection were conducted, and the calculation procedure of the beam-column relative rotation angle and plastic rotation angle was developed and described in details. A comparative analysis of mechanical property and steel consumption were employed for the proposed I-section column weak-axis connection and box-section column bending connection. The result showed that no signs of fracturing were observed and the plastic hinge formed reliably in the beam section away from the skin plate under the beam end monotonic loading, and the plastic hinge formed much closer to the skin plate under the beam end cyclic loading. The fracture of welds between diaphragm and skin plate would cause an unstable hysteretic response under the column top horizontal cyclic loading. The proposed weak-axis connection system could not only simplify the design calculation progress when I-section column is adopted in frame structural design but also effectively satisfy the requirements of 'strong joint and weak member', as well as lower steel consumption.

Limiting the sway on multi-storey un-braced steel frames bending on weak axis with partial strength connections

  • Tahir, Mahmood Md.;Ngian, Poi Shek
    • Structural Engineering and Mechanics
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    • v.38 no.6
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    • pp.825-847
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    • 2011
  • This paper investigates the design using wind-moment method for semi-rigid un-braced steel frames bending on weak axis. A limiting sway method has been proposed to reduce the frame sway. Allowance for steel section optimization between moment of inertia on minor axis column and major axis beam was used in conjunction with slope-deflection analysis to derive equations for optimum design in the proposed method. A series of un-braced steel frames comprised of two, four, and six bays ranging in height of two and four storey were studied on minor axis framing. The frames were designed for minimum gravity load in conjunction with maximum wind load and vice-versa. The accuracy of the design equation was found to be in good agreement with linear elastic computer analysis up to second order analysis. The study concluded that the adoption of wind-moment method and the proposed limiting sway method for semi-rigid steel frame bending on weak axis should be restricted to low-rise frames not more than four storey.

Development of Beam-to-Column Connection Details with Horizontal Stiffeners in Weak Axis of H-shape Column (수평스티프너를 이용한 철골 기둥-보 약축접합부 상세 개발에 관한 연구)

  • Lee, Do Hyung;Ham, Jeong Tae;Kim, Sung Bae;Kim, Young Ho;Kim, Sang Seup
    • Journal of Korean Society of Steel Construction
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    • v.16 no.5 s.72
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    • pp.641-652
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    • 2004
  • The strong beam-to-column axis connections in steel structures have been studied for a long time to develop the strength and resistance of the connections. There have been very few studies, however, related to weak axis connections. Domestically, the bracket-type connection is commonly used in weak axis connections to elevate the efficiency of the constructions when the steel structures are constructed. The bracket-type connection detail has been applied moderately to weak axis connections. Therefore, the bracket-type connection in weak axis connections might be brittle and over-designed. The results of this study showed that the welding on the web of the column and the beam was unnecessary. In addition, this study confirmed that the new weak axis connection proposed in this study was superior to the previous connection in terms of strength and ductility.

Structural Performance and CO2 Reduction Evaluation of the Ultra simple Wide-shaped section Beam-to-Column Weak Axis Connection (초간편 H형강 기둥-보 약축접합부의 구조성능 및 CO2 저감량 평가)

  • Kim, Sang-Seup;Boo, Yoon-Seob
    • Journal of Korean Society of Steel Construction
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    • v.23 no.5
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    • pp.615-627
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    • 2011
  • There have been few researches on the connection technology for steel structures, so the research outputs and the outcome of the technology development are still insufficient. The bracket-type connection should be improved for efficient constructability and $CO_2$ reduction. It should be replaced by a new type of weak-axis connection that has better structural performance and less $CO_2$ emission. Since the structural performance and safety of the new type of weak-axis connection must first be verified, however, a study on $CO_2$ reduction will be conducted. Therefore, this study looked into the structural performance of the bracket-type details, standard details, and ultra-simple details. It evaluated the requirements for connection materials and $CO_2$ emission. It was found that the ultra-simple weak-axis connection has thebest structural performance and the least $CO_2$ emissions, so it is deemed capable of replacing the bracket-type weak-axis connection.

Development and Strength Evaluation of Beam-to-Column Connection Details in Weak Axis of H-shape Column (H형강 기둥의 약축에 대한 기둥-보 접합상세 개발 및 내력평가)

  • Kim, Sang Seup;Lee, Do Hyung;Ham, Jeong Tae;Kim, Kyu Suk
    • Journal of Korean Society of Steel Construction
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    • v.16 no.1 s.68
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    • pp.169-180
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    • 2004
  • One of the most influential elements is the moment resisting beam-to-column connection vis-a-vis the behavior and cost of multistory steel building frames. Majority of these connections are column flange connections attached to beam frames. This is called strong-axis connection. Another type of moment resisting connection commonly found in building frames is the web axis connection. In this type of connection, the beams are attached to the plane of the column web perpendicularly. It is called the weak-axis beam. and it tends to bend the column at its weak axis. In this study, some of the fundamental behaviors of beam-to-column connections were examined by changing the connection details as weil as comparing them with previous connection details. This study sought to develop the details in the beam-to-column connection in the weak axis for middle- and low-rise steel construction systems.

Partially restrained beam-column weak-axis moment connections of low-rise steel structures

  • Lim, Woo-Young;Lee, Dongkeun;You, Young-Chan
    • Structural Engineering and Mechanics
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    • v.76 no.5
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    • pp.663-674
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    • 2020
  • In this study, partially restrained beam-column moment joints in the weak-axis direction were examined using three large-scale specimens subject to cyclic loading in order to assess the seismic resistance of the joints of low-rise steel structures and to propose joint details based on the test results. The influence of different number of bolts on the moment joints was thoroughly investigated. It was found that the flexural capacity of the joints in the direction of weak axis was highly dependent on the number of high-tension bolts. In addition, even though the flexural connections subjected to cyclic loading was perfectly designed in accordance with current design codes, severe failure mode such as block shear failure could occur at beam flange. Therefore, to prevent excessive deformation at bolt holes under cyclic loading conditions, the holes in beam flange need to have larger bearing capacity than the required tensile force. In particular, if the thickness of the connecting plate is larger than that of the beam flange, the bearing capacity of the flange should be checked for structural safety.

Cyclic testing of weak-axis column-tree connections with formation of plastic hinge at beam splice

  • Oh, Keunyeong;Chen, Liuyi;Hong, Sungbin;Yang, Yang;Lee, Kangmin
    • Earthquakes and Structures
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    • v.8 no.5
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    • pp.1039-1054
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    • 2015
  • The purpose of this study was to evaluate the seismic performance of weak-axis column-tree type connections used in steel moment frames. These connections are composed of a shop-welded and fieldbolted steel structure and can improve welding quality. On this basis, column-tree type connections are widely used in steel moment resisting frames in Korea and Japan. In this study, splices designed with a semirigid concept regarding the seismic performance of column-tree connections were experimentally evaluated. The structures can absorb energy in an inelastic state rather than the elastic state of the structures by the capacity design method. For this reason, the plastic hinge might be located at the splice connection at the weak-axis column-tree connection by reducing the splice plate thickness. The main variable was the distance from the edge of the column flange to the beam splice. CTY series specimens having column-tree connections with splice length of 600 mm and 900 mm were designed, respectively. For comparison with two specimens with the main variable, a base specimen with a weak-axis column-tree connection was fabricated and tested. The test results of three full-scale test specimens showed that the CTY series specimens successfully developed ductile behavior without brittle fracture until 5% story drift ratio. Although the base specimen reached a 5% story drift ratio, brittle fracture was detected at the backing bar near the beam-to-column connection. Comparing the energy dissipation capacity for each specimen, the CTY series specimens dissipated more energy than the base specimen.

Cyclic response and design procedure of a weak-axis cover-plate moment connection

  • Lu, Linfeng;Xu, Yinglu;Zheng, Huixiao;Lim, James B.P.
    • Steel and Composite Structures
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    • v.26 no.3
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    • pp.329-345
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    • 2018
  • This paper systematically investigated the mechanical performance of the weak-axis cover-plate connection, including a beam end monotonic loading test and a column top cyclic loading test, and a series of parametric studies for exterior and interior joints under cyclic loading using a nonlinear finite element analysis program ABAQUS, focusing on the influences of the shape of top cover-plate, the length and thickness of the cover-plate, the thickness of the skin plate, and the steel material grade. Results showed that the strains at both edges of the beam flange were greater than the middle's, thus it is necessary to take some technical methods to ensure the construction quality of the beam flange groove weld. The plastic rotation of the exterior joint can satisfy the requirement of FEMA-267 (1995) of 0.03 rad, while only one side connection of interior joint satisfied ANSI/AISC 341-10 under the column top cyclic loading. Changing the shape or the thickness or the length of the cover-plate did not significantly affect the mechanical behaviors of frame joints no matter in exterior joints or interior joints. The length and thickness of the cover-plate recommended by FEMA 267 (1995) is also suitable to the weak-axis cover-plate joint. The minimum skin plate thickness and a design procedure for the weak-axis cover-plate connections were proposed finally.