• Title, Summary, Keyword: tubular stiffeners

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Tensile Behavior of Concrete-Filled Square Steel Tubular Column-Beam Flange Connections with Stiffeners (강관 보강형 충전 각형강관 기둥-보 플랜지 접합부의 인장거동에 관한 실험적 연구)

  • Yoo, Yeong Chan;Kang, Hyun Sik;Moon, Tae Sup
    • Journal of Korean Society of Steel Construction
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    • v.13 no.1
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    • pp.1-8
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    • 2001
  • The purpose of this study is to examine the utility of concretefilled steel tubular column to H-beam connections with tubular stiffener. As a preliminary step. a tensile experiment was undertaken to scrutinize characteristics of the structural behavior that take place between beam flanges and column with tubular stiffener. A total of 4 types of experimental settings were developed as tabular stiffeners are made up 9, 18, and 27 mm of thickness and 50 and 80 mm of height respetively Along with the overall load subsequently the degree of displacement and strain were recorded. Based on the yield line theory results of this of this study were evaluated and further critically reviewed the applicability of the strength formula. This study found that collapse mechanism was emerged on the beam flange as reinforcing tabular stiffeners Complementary studies of this sort, including numerical analyses should be undertaken in order to develope specific design critera.

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Tensile Behavior of CFT Column-to-H beam Connections with External T-shaped Stiffeners (T-스티프너 보강 콘크리트충전 각형강관 기둥-H형강 보 접합부의 인장거동)

  • Kang, Chang Hoon;Shin, Kyung Jae;Oh, Young Suk;Moon, Tae Sup
    • Journal of Korean Society of Steel Construction
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    • v.14 no.1
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    • pp.121-130
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    • 2002
  • This paper presents the tensile behavior of a Concrete-Filled Square Steel Tubular (CFT) column to H-beam welded connections. These connections were externally reinforced with T-shaped stiffeners at the junction of CFT column and beam. The tensile loading tests of eighteen tee-joint connections and finite element analysis using ANSYS were carried out. The main parameters of tests are as follows: 1) the thickness of Square Steel Tubular Column : 6 mm, 9 mm, 2) the strength ratios of tensile strength of horizontal stiffeners to tensile strength of beam flange : 70 %, 100 %, 150 %, 3) the strength ratios of shear strength of vertical stiffeners to tensile strength of beam flange : 80 %, 115 %, 160 %. The results of the tests demonstrate that overall behavior and failure modes of all the specimens are governed mainly by the horizontal stiffeners rather than the vertical stiffeners, and the vertical stiffener played only a role in transferring load introduced from beam to column.

Evaluation of Installation and Arrangement Effects of Internal Ring Stiffener for Tubular K-joints with Axially Loaded Braces (지부재에 축하중을 받는 K형 관이음부의 내부 환보강재의 설치 및 배치효과 평가)

  • Cho, Hyun-Man;Ryu, Yeon-Sun;Lim, Dong-Joo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.3
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    • pp.267-274
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    • 2011
  • The effect of internal ring stiffeners is numerically evaluated for reinforcement of tubular K-joints. Finite element analyses are performed to compute stress of un-stiffened and ring-stiffened K-joints subjected to axial loading. The influence of loading condition and geometrical parameters of ring stiffener on joint behavior is assessed to determine the installation effect of single and double ring stiffeners. The arrangement effect of ring stiffener are evaluated using quantitative analysis compared single ring with double ring stiffeners. Based on the numerical results, practical size of ring stiffener is proposed for design of tubular K-joints.

Experimental and Numerical Study on Complex Multi-planar Welded Tubular Joints in Umbrella-Type Space Trusses with Long Overhangs

  • Jiao, Jinfeng;Ma, Xiao;Lei, Honggang;Chen, Y. Frank
    • International journal of steel structures
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    • v.18 no.5
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    • pp.1525-1540
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    • 2018
  • A test rig with multi-functional purposes was specifically designed and manufactured to study the behavior of multi-planar welded tubular joints subjected to multi-planar concurrent axial loading. An experimental investigation was conducted on full-scale welded tubular joints with each consisting of one chord and eight braces under monotonic loading conditions. Two pairs or four representative specimens (two specimens for each joint type) were tested, in which each pair was reinforced with two kinds of different internal stiffeners at the intersections between the chords using welded rectangular hollow steel sections (RHSSs) and the braces using rolled circular hollow steel sections (CHSSs) and welded RHSSs. The effects of different internal stiffeners at the chord-brace intersection on the load capacity of joints under concurrent multi-planar axial compression/tension are discussed. The test results of joint strengths, failure modes, and load-stress curves are presented. Finite element analyses were performed to verify the experimental results. The study results show that the two different joint types with the internal stiffeners at the chord-brace intersection under axial compression/tension significantly increase the corresponding ultimate strength to far exceed the usual design strength. The load carrying capacity of welded tubular joints decreases with a higher degree of the manufacturing imperfection in individual braces at the tubular joints. Furthermore, the interaction effect of the concurrent axial loading applied at the welded tubular joint on member stress is apparent.

Seismic behavior of stiffened concrete-filled double-skin tubular columns

  • Shekastehband, B.;Mohammadbagheri, S.;Taromi, A.
    • Steel and Composite Structures
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    • v.27 no.5
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    • pp.577-598
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    • 2018
  • The imperfect steel-concrete interface bonding is an important deficiency of the concrete-filled double skin tubular (CFDST) columns that led to separating concrete and steel surfaces under lateral loads and triggering buckling failure of the columns. To improve this issue, it is proposed in this study to use longitudinal and transverse steel stiffeners in CFDST columns. CFDST columns with different patterns of stiffeners embedded in the interior or exterior surfaces of the inner or outer tubes were analyzed under constant axial force and reversed cyclic loading. In the finite element modeling, the confinement effects of both inner and outer tubes on the compressive strength of concrete as well as the effect of discrete crack for concrete fracture were incorporated which give a realistic prediction of the seismic behavior of CFDST columns. Lateral strength, stiffness, ductility and energy absorption are evaluated based on the hysteresis loops. The results indicated that the stiffeners had determinant role on improving pinching behavior resulting from the outer tube's local buckling and opening/closing of the major tensile crack of concrete. The lateral strength, initial stiffness and energy absorption capacity of longitudinally stiffened columns with fixed-free end condition were increased by as much as 17%, 20% and 70%, respectively. The energy dissipation was accentuated up to 107% for fixed-guided end condition. The use of transverse stiffeners at the base of columns increased energy dissipation up to 35%. Axial load ratio, hollow ratio and concrete strength affecting the initial stiffness and lateral strength, had negligible effect of the energy dissipation of the columns. It was also found that the longitudinal stiffeners and transverse stiffeners have, respectively, negative and positive effects on ductility of CFDST columns. The conclusions, drawn from this study, can in turn, lead to the suggestion of some guidelines for the design of CFDST columns.

A comparison of structural performance enhancement of horizontally and vertically stiffened tubular steel wind turbine towers

  • Hu, Yu;Yang, Jian;Baniotopoulos, Charalambos C.;Wang, Feiliang
    • Structural Engineering and Mechanics
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    • v.73 no.5
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    • pp.487-500
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    • 2020
  • Stiffeners can be utilised to enhance the strength of thin-walled wind turbine towers in engineering practise, thus, structural performance of wind turbine towers by means of different stiffening schemes should be compared to explore the optimal structural enhancement method. In this paper two alternative stiffening methods, employing horizontal or vertical stiffeners, for steel tubular wind turbine towers have been studied. In particular, two groups of three wind turbine towers of 50m, 150m and 250m in height, stiffened by horizontal rings and vertical strips respectively, were analysed by using FEM software of ABAQUS. For each height level tower, the mass of the stiffening rings is equal to that of vertical stiffeners each other. The maximum von Mises stresses and horizontal sways of these towers with vertical stiffeners is compared with the corresponding ring-stiffened towers. A linear buckling analysis is conducted to study the buckling modes and critical buckling loads of the three height levels of tower. The buckling modes and eigenvalues of the 50m, 150m and 250m vertically stiffened towers were also compared with those of the horizontally stiffened towers. The numbers and central angles of the vertical stiffeners are considered as design variables to study the effect of vertical stiffeners on the structural performance of wind turbine towers. Following an extensive parametric study, these strengthening techniques were compared with each other and it is obtained that the use of vertical stiffeners is a more efficient approach to enhance the stability and strength of intermediate and high towers than the use of horizontal rings.

Axial Strength Evaluation for Tubular X-Joints with Internal Ring Stiffener (고리형 내부 보강재를 가진 X형 관이음부의 축방향 강도 평가)

  • 조현만;류연선;김정태
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.162-169
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    • 2001
  • Tubular joints are usually reinforced using thicker can section or ring stiffeners to increase the load carrying capacity. In this paper, a numerical study has been performed for evaluation of axial strength for X-joints with internal ring stiffener, The finite element analysis software was used for nonlinear strength analysis. According to variation of ring geometries, the effect of ring stiffener for X-joints are investigated. Internal ring stiffener is found to be efficient improving ultimate strength of tubular joints. Relations of thickness of ring and axial strength are observed considering geometric parameters of ring stiffeners.

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Axial Strength Evaluation for Tubular T-Joints with Internal Ring Stiffener (환보강재를 가진 T형 관이음부의 축방향 강도 평가)

  • 조현만;류연선;김정태
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.269-276
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    • 2001
  • Tubular structures are widely used for offshore platforms and truss type structures. In this paper, nonlinear finite element analysis is used to assess the static strength of stiffened tubular T-joints subjected to compressive brace loading. This joints was modelled with and without internal ring stiffener According to variation of ring geometries, the effect of ring stiffener for T-joints are investigated. Internal ring stiffener is found to be efficient improving ultimate strength of tubular joints. Relations of ring thickness and axial strength are observed considering geometric parameters of ring stiffeners.

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A parametric investigation on the hysteretic behaviour of CFT column to steel beam connections

  • Esfandyary, R.;Razzaghi, M.S.;Eslami, A.
    • Structural Engineering and Mechanics
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    • v.55 no.1
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    • pp.205-228
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    • 2015
  • The results of a numerical investigation pertaining to the hysteretic behaviour of concrete filled steel tubular (CFT) column to I-beam connections are discussed in detail. Following the verification of the numerical results against the available experimental tests, the nonlinear finite element (FE) analysis was implemented to evaluate the effects of different parameters including the column axial load, beam lateral support, shape and arrangement of stiffeners, stiffness of T-stiffeners, and the number of shear stiffeners. Pursuing this objective, an external CFT column to beam connection, tested previously, was selected as the case-study. The lateral forces on the structure were simulated, albeit approximately, using an incremental cyclic loading reversal applied at the beam tip. The results were compared in terms of hysteretic load-displacement curves, stress distributions in connection, strength, rotation, and energy dissipation capacity. It was shown that external T-stiffeners combined with internal shear stiffeners play an important role in the hysteretic performance of CFT columns to I-beam connections.

Effect of Reinforcement Type on Ultimate Strength of Tubular X-Joints (X형 관이음부의 보강방법에 따른 극한강도 해석)

  • 조현만;류현선;김정태
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.230-237
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    • 2000
  • Tubular joints of jacket structures are usually reinforced using thicker can section, internally ring stiffeners, diaphragm, or externally gusset plates to increase load carry capacity. In this paper, the effect of reinforcement type and geometric parameters of stiffener on the ultimate strength of tubular X-joints subjected to brace compression have been studied numerically Three reinforcement methods were considered; (1)can reinforcement (2)internally ring stiffener (3)internally longitudinal diaphragm. The ANSYS software was used nonlinear strength analysis. It was found that there is significant strength enhancement for reinforced joints.

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