• Title/Summary/Keyword: cold-formed beams

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Flexural performance of cold-formed square CFST beams strengthened with internal stiffeners

  • Zand, Ahmed W. Al;Badaruzzaman, W.H. Wan;Ali, Mustafa M.;Hasan, Qahtan A.;Al-Shaikhli, Marwan S.
    • Steel and Composite Structures
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    • v.34 no.1
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    • pp.123-139
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    • 2020
  • The tube outward local buckling of Concrete-Filled Steel Tube (CFST) beam under high compression stress is still considered a critical problem, especially for steel tubes with a slender section compared to semi-compact and compact sections. In this study, the flexural performance of stiffened slender cold-formed square tube beams filled with normal concrete was investigated. Fourteen (14) simply supported CFST specimens were tested under static bending loads, stiffened with different shapes and numbers of steel stiffeners that were provided at the inner sides of the tubes. Additional finite element (FE) CFST models were developed to further investigate the influence of using internal stiffeners with varied thickness. The results of tests and FE analyses indicated that the onset of local buckling, that occurs at the top half of the stiffened CFST beam's cross-section at mid-span was substantially restricted to a smaller region. Generally, it was also observed that, due to increased steel area provided by the stiffeners, the bending capacity, flexural stiffness and energy absorption index of the stiffened beams were significantly improved. The average bending capacity and the initial flexural stiffness of the stiffened specimens for the various shapes, single stiffener situations have increased of about 25% and 39%, respectively. These improvements went up to 45% and 60%, for the double stiffeners situations. Moreover, the bending capacity and the flexural stiffness values obtained from the experimental tests and FE analyses validated well with the values computed from equations of the existing standards.

Shear behaviour of thin-walled composite cold-formed steel/PE-ECC beams

  • Ahmed M. Sheta;Xing Ma;Yan Zhuge;Mohamed A. ElGawady;Julie E. Mills;El-Sayed Abd-Elaal
    • Steel and Composite Structures
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    • v.46 no.1
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    • pp.75-92
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    • 2023
  • The novel composite cold-formed steel (CFS)/engineered cementitious composites (ECC) beams have been recently presented. The new composite section exhibited superior structural performance as a flexural member, benefiting from the lightweight thin-walled CFS sections with improved buckling and torsional properties due to the restraints provided by thinlayered ECC. This paper investigated the shear performance of the new composite CFS/ECC section. Twenty-eight simply supported beams, with a shear span-to-depth ratio of 1.0, were assembled back-to-back and tested under a 3-point loading scheme. Bare CFS, composite CFS/ECC utilising ECC with Polyethylene fibres (PE-ECC), composite CFS/MOR, and CFS/HSC utilising high-strength mortar (MOR) and high-strength concrete (HSC) as replacements for PE-ECC were compared. Different failure modes were observed in tests: shear buckling modes in bare CFS sections, contact shear buckling modes in composite CFS/MOR and CFS/HSC sections, and shear yielding or block shear rupture in composite CFS/ECC sections. As a result, composite CFS/ECC sections showed up to 96.0% improvement in shear capacities over bare CFS, 28.0% improvement over composite CFS/MOR and 13.0% over composite CFS/HSC sections, although MOR and HSC were with higher compressive strength than PE-ECC. Finally, shear strength prediction formulae are proposed for the new composite sections after considering the contributions from the CFS and ECC components.

Structural Behavior of Newly Developed Cold-Formed Steel Sections(II) - Flexural Behavior (신형상 냉간성형 단면의 구조적 거동(II) - 휨거동)

  • Song, In Seop;Kim, Gap Deuk;Kwon, Young Bong
    • Journal of Korean Society of Steel Construction
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    • v.14 no.2
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    • pp.357-364
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    • 2002
  • The study performed a series of flexural tests on Closed Cold-Formed Steel Sections for stud, joist, and roof truss. Results were compared with analytical values. Each 2.4-m long and 0.9-m wide specimen consisted of two steel beams set at 0.46 m interval. The steel beams were attached to the specimens using either plaster board or ply wood. Another specimens did not use any attachment material. Positive and negative bending tests were conducted to investigate the composite behavior, including the effects of plaster board or ply wood on the buckling behavior of steel beam. Full-scale roof truss tests were also performed to study the buckling behavior and failure mode of the truss members.

Stiffening schemes for CFS built-up I-beams with large global imperfections: Capacity and behaviour

  • Dar, M. Adil;Anbarasu M.;Dar, A.R.;Islam, Naqeeb Ul;Ghowsi, Ahmad Fayeq;Carvalho, Hermes
    • Steel and Composite Structures
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    • v.42 no.4
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    • pp.447-458
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    • 2022
  • Cold-formed steel (CFS) sections are thin-walled, therefore, more susceptible to different types of geometric imperfections. Global type of geometric imperfections has a significant impact on the load-carrying capacity of flexural members. This paper reports an experimental study that discusses the influence of global imperfections on the flexural response of CFS built-up I-beams composed of two lipped channels, with simply supported ends, under four-point loading. Global imperfections of magnitude over eight times the maximum permissible ones were induced in the specimens, leading to their distress. Using various simple stiffening schemes, the capacity and stiffness of the distressed specimens were improvised. The performance comparisons were made based on the maximum loads resisted, flexural stiffnesses offered, and failure modes experienced by the specimens. As experimental data on such distressed specimens are currently lacking in the literature, the test results of the present study will provide the necessary data needed by future researchers to numerically extend this study further, which will help in the development of necessary design guidelines for the same. The stiffening schemes significantly improved the structural efficiency of distressed specimens in terms of strength and stiffness, by over 60%. As a result, an effective and time-saving solution to such realistic structural engineering problems is given.

Efficient cross-sectional profiling of built up CFS beams for improved flexural performance

  • Dar, M. Adil;Subramanian, N.;Atif, Mir;Dar, A.R.;Anbarasu, M.;Lim, James B.P.
    • Steel and Composite Structures
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    • v.34 no.3
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    • pp.333-345
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    • 2020
  • In the past, many efficient profiles have been developed for cold-formed steel (CFS) members by judicious intermediate stiffening of the cross-sections, and they have shown improved structural performance over conventional CFS sections. Most of this research work was based on numerical modelling, thus lacking any experimental evidence of the efficiency of these sections. To fulfill this requirement, experimental studies were conducted in this study, on efficient intermediately stiffened CFS sections in flexure, which will result in easy and simple fabrication. Two series of built-up sections, open sections (OS) and box sections (BS), were fabricated and tested under four-point loading with same cross-sectional area. Test strengths, modes of failure, deformed shapes, load vs. mid-span displacements and geometric imperfections were measured and reported. The design strengths were quantified using North American Standards and Indian Standards for cold-formed steel structures. This study confirmed that efficient profiling of CFS sections can improve both the strength and stiffness performance by up to 90%. Closed sections showed better strength performance whereas open sections showed better stiffness performance.

Partial Composite Action of Gypsum-Sheathed Cold-Formed Steel Wall Stud Panels (석고보드와 결합된 강재 샛기둥 패널의 부분 합성거동)

  • Lee, Young Ki
    • Journal of Korean Society of Steel Construction
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    • v.13 no.4
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    • pp.373-380
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    • 2001
  • The problem addressed in this study is how to analytically treat the partial composite action for wall panels. An equation, derived for wood-joist floor systems, which determines deflections for beams with partial composite action is introduced. The equation is applied to the calculation of the mid-span deflection for gypsum-sheathed, cold-formed steel was stud panels. The objective of this study is to properly reflect the influence of the following factors in the calculation of mid-span deflection for the panel: connection slip, local buckling, perforations in the stud web, and effects from joints in the sheathing. Predicted deflections based on an upper bound for connection rigidity were closest to experimental deflections.

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Distortional buckling formulae for cold-formed steel rack-section members

  • Silvestre, N.;Camotim, D.
    • Steel and Composite Structures
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    • v.4 no.1
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    • pp.49-75
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    • 2004
  • The paper derives, validates and illustrates the application of GBT-based formulae to estimate distortional critical lengths and bifurcation stress resultants in cold-formed steel rack-section columns, beams and beam-columns with arbitrarily inclined mid-stiffeners and four support conditions. After a brief review of the Generalised Beam Theory (GBT) basics, the main concepts and procedures employed to obtain the formulae are addressed. Then, the GBT-based estimates are compared with exact results and, when possible, also with values yielded by formulae due to Lau and Hancock, Hancock and Teng et al. A few remarks on novel aspects of the rack-section beam-column distortional buckling behaviour, unveiled by the GBT-based approach, are also included.

Economic construction management of composite beam using the head stud shear connector with encased cold-formed steel built-up fix beam via efficient computer simulation

  • Yin, Jinzhao;Tong, Huizhi;Gholizadeh, Morteza;Zandi, Yousef;Selmi, Abdellatif;Roco-Videla, Angel;Issakhov, Alibek
    • Advances in concrete construction
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    • v.11 no.5
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    • pp.429-445
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    • 2021
  • With regard to economic efficiency, composite fix beams are widely used to pass longitudinal shear forces across the interface. The current knowledge of the composite beam load-slip activity and shear capability are restricted to data from measurements of push-off. Modelling and analysis of the composite beams based on Euro-code 4 regarding to shear, bending, and deflection under differing loads were carried out using Finite Element through an efficient computer simulation and the final loading and sections capacity based on the failure modes was analysed. In bending, the section potential was increased by an improvement of the strength in both steel and concrete, but the flexural and compressive resistance growth is very weak (3.2% 3.1% and 3.0%), while the strength of the concrete has increased respectively from 25 N/mm2 to 30, 35, and 40 N/mm2 compared to the increment of steel strength by 27% and 21% when it was raised from 275 to 355 and 460 N/mm2, respectively. It was found that the final flexural load capacity of fix beams was declined with increase in the fix beam span for both three steel strength. The shear capacity of sections was remained unchanged at constant steel strength and different length, but raised with final yield strength increment of steel sections by 29%, and 67% when it was raised from 275 N/mm2 to 355 N/mm2 and 460 N/mm2, respectively.

Seismic characterization of cold formed steel pallet racks

  • Saravanan, M.;Marimuthu, V.;Prabha, P.;Surendran, M.;Palani, G.S.
    • Earthquakes and Structures
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    • v.7 no.6
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    • pp.955-967
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    • 2014
  • Storage racks are used worldwide in industries and commercial outlets due to the advantage of lighter, faster erection and easy alteration of pallet level as required. The studies to understand the behaviour of cold formed steel pallet racks, under seismic action is one of the emerging area of research. The rack consists of perforated uprights and beams with hook-in end connector, which enables the floor height adjustments. The dynamic characteristics of these racks are not well established. This paper presents the dynamic characteristics of 3-D single bay two storey pallet rack system with hook-in end connectors, which is tested on shake table. The sweep sine test and El Centro earthquake acceleration is used to evaluate the seismic performance of the cold formed steel pallet racks. Also an attempt is made to evaluate the realistic dynamic characteristics by using STAAD Pro software. Modal analysis is performed by incorporating the effective moment of inertia of the upright, which considers the effect of presence of perforations and rotational stiffness of the beam-to-upright connection to determine the realistic fundamental frequency of pallet racks, which is required for carrying out the seismic design. Finite element model of the perforated upright section has been developed as a cantilever beam through which effective moment of inertia is evaluated. The stiffness of the hook-in connector is taken from the previous study by Prabha et al. (2010). The results from modal analysis are in good agreement with the respective experimental results.

A Study on Electric Characteristics of Plasma Electon Beam Produced by Cold Cathode. (냉음극을 이용한 plasma전자 beam의 전기적 입력특성 I)

  • 전춘생;박용관
    • 전기의세계
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    • v.27 no.3
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    • pp.36-42
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    • 1978
  • It has been investigates that electric characteristics of plasma electron beam in N$_{2}$, H$_{2}$ and Ar gas jars under various gas pressures during electron beams are formed. The results are as follows: 1)Electron beam is formed in the region of positive resistance on the characteristic curve. This phenomenon is identical in N$_{2}$, H$_{2}$ and Ar gases. 2)But in Ar gas, electron beam is formed at relatively lower gas pressure than in H$_{2}$ and N$_{2}$. 3)In pure gas either N$_{2}$, H$_{2}$ and N$_{2}$ the lower the gas pressure, the higher the voltage drop for the same electron beam current. 4)The region in which electron beam is formed is limited at a given pressure. 5)Beyond the limit mentioned above, it becomes glow discharge state and the current increases radically. 6)At a given gas pressure, electron beam voltage, that is, electrical power input increases with gap length.

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