The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform
Xiao Ling Zhao - One of the best experts on this subject based on the ideXlab platform.
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Tests and design of concrete-filled elliptical hollow section stub columns
Thin-walled Structures, 2009Co-Authors: Xiao Ling Zhao, Jeffrey A. PackerAbstract:Similar to concrete-filled tubular columns, void-filling of elliptical hollow sections (EHS) will produce increased strength, stiffness, energy absorption and fire resistance. Stub column tests on unfilled EHS were performed first. Discussions are made on the equivalent diameters in the literature for deriving the yield Slenderness Limit. An equivalent rectangular hollow sections (RHS) is proposed to derive such a Limit for EHS sections in axial compression. An experimental investigation has also been carried out on the behaviour of concrete-filled EHS stub columns. Both normal concrete and self consolidating concrete (SCC) were used in the testing program. Different loading methods were investigated; e.g., loading through steel alone, loading through concrete alone and loading through the whole cross-section. This paper is based on experimental data on carbon steel EHS with an aspect ratio of 2, which is also the only product type currently produced. The load carrying capacity is compared with that predicted using EC4 and CAN/CSA-S16. Proposed design formulae are given.
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imperfection residual stress and yield Slenderness Limit of very high strength vhs circular steel tubes
Journal of Constructional Steel Research, 2003Co-Authors: Hui Jiao, Xiao Ling ZhaoAbstract:This paper investigates the initial geometrical imperfection, residual stresses and yield Slenderness Limit of very high strength (VHS) circular steel tubes with the yield stress of 1350 MPa. The out-of-straightness is found to be about L/6800 on average, where L is the length of the stub column. The measured residual stress is found to be approximately 4% on average of the yield stress, with the outside surface in compression and the inside surface in tension. Eight stub columns were tested with the element Slenderness ratio ranging from 135 to 258. New element Slenderness Limit (ley) of 258 and non-dimensional local buckling parameter Limit of 3.1 are proposed for VHS tubes. The very large value of ley is obtained partly because of the very large yield stress used in the definition of element Slenderness and partly because of the very low residual stress in the section. Two stub columns of non-heat-treated tubes were also tested in the same manner. The results were compared with those of the VHS tubes. Both VHS tubes and non-heat-treated tubes have a similar level of geometrical imperfections. The residual stress pattern obtained for non-heat-treated tubes is very different from that of VHS tubes. 2002 Elsevier Science Ltd. All rights reserved.
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Tests on concrete filled double-skin (CHS outer and SHS inner) composite short columns under axial compression
Thin-walled Structures, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:This paper presents stub columns tests on concrete-filled double skin sandwich tubes (CFDT) constructed using cold-formed steel tubes. The annulus is filled with micro high-strength concrete having compressive cylinder strength of 64 MPa. The outer skin is made of circular hollow sections (CHS), while the inner skin is made of square hollow sections (SHS). Eight different section sizes were used for the outer skin with diameter-to-thickness ratio ranging from 19 to 55. Three section sizes were chosen for the inner skin with width-to-thickness ratio in the range of 20 to 26. The CFDT construction was found to have significant increase in strength, ductility and energy absorption over the outer jacket. A simplified formula is derived to determine the compressive capacity of CFDT and compared against the current design rules. The proposed formula was found in good agreement with experimental results. This paper also verifies the yield Slenderness Limit (λey) of 82 specified in AS 4100 for cold-formed CHS stub columns.
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Tests on concrete filled double-skin (CHS outer and SHS inner) composite short columns under axial compression
Thin-Walled Structures, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:This paper presents stub columns tests on concrete-filled double skin sandwich tubes (CFDT) constructed using cold-formed steel tubes. The annulus is filled with micro high-strength concrete having compressive cylinder strength of 64 MPa. The outer skin is made of circular hollow sections (CHS), while the inner skin is made of square hollow sections (SHS). Eight different section sizes were used for the outer skin with diameter-to-thickness ratio ranging from 19 to 55. Three section sizes were chosen for the inner skin with width-to-thickness ratio in the range of 20 to 26. The CFDT construction was found to have significant increase in strength, ductility and energy absorption over the outer jacket. A simplified formula is derived to determine the compressive capacity of CFDT and compared against the current design rules. The proposed formula was found in good agreement with experimental results. This paper also verifies the yield Slenderness Limit (λey) of 82 specified in AS 4100 for cold-formed CHS stub columns. © 2002 Elsevier Science Ltd. All rights reserved.
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Plastic Slenderness Limits for Cold-formed Circular Hollow Sections
Australian Journal of Structural Engineering, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:There are significant differences in d/t Limits recommended in various codes for circular hollow sections (CHS) under bending. This paper reviews the existing data on plastic Slenderness Limits for CHS. It describes an experimental investigation of the plastic flexural behaviour of Australian-produced cold-formed CHS. Plastic bending tests were performed on different sizes of CHS with d/t ranging from 13 to 39. The test results are compared with design rules given in various codes. A plastic Slenderness Limit ( λ{p}) is determined for cold-formed CHS. A model considering CHS ovalization is developed to predict the ultimate moment capacity of CHS subjected to pure bending.
Raphael Grzebieta - One of the best experts on this subject based on the ideXlab platform.
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Tests on concrete filled double-skin (CHS outer and SHS inner) composite short columns under axial compression
Thin-walled Structures, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:This paper presents stub columns tests on concrete-filled double skin sandwich tubes (CFDT) constructed using cold-formed steel tubes. The annulus is filled with micro high-strength concrete having compressive cylinder strength of 64 MPa. The outer skin is made of circular hollow sections (CHS), while the inner skin is made of square hollow sections (SHS). Eight different section sizes were used for the outer skin with diameter-to-thickness ratio ranging from 19 to 55. Three section sizes were chosen for the inner skin with width-to-thickness ratio in the range of 20 to 26. The CFDT construction was found to have significant increase in strength, ductility and energy absorption over the outer jacket. A simplified formula is derived to determine the compressive capacity of CFDT and compared against the current design rules. The proposed formula was found in good agreement with experimental results. This paper also verifies the yield Slenderness Limit (λey) of 82 specified in AS 4100 for cold-formed CHS stub columns.
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Tests on concrete filled double-skin (CHS outer and SHS inner) composite short columns under axial compression
Thin-Walled Structures, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:This paper presents stub columns tests on concrete-filled double skin sandwich tubes (CFDT) constructed using cold-formed steel tubes. The annulus is filled with micro high-strength concrete having compressive cylinder strength of 64 MPa. The outer skin is made of circular hollow sections (CHS), while the inner skin is made of square hollow sections (SHS). Eight different section sizes were used for the outer skin with diameter-to-thickness ratio ranging from 19 to 55. Three section sizes were chosen for the inner skin with width-to-thickness ratio in the range of 20 to 26. The CFDT construction was found to have significant increase in strength, ductility and energy absorption over the outer jacket. A simplified formula is derived to determine the compressive capacity of CFDT and compared against the current design rules. The proposed formula was found in good agreement with experimental results. This paper also verifies the yield Slenderness Limit (λey) of 82 specified in AS 4100 for cold-formed CHS stub columns. © 2002 Elsevier Science Ltd. All rights reserved.
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Plastic Slenderness Limits for Cold-formed Circular Hollow Sections
Australian Journal of Structural Engineering, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:There are significant differences in d/t Limits recommended in various codes for circular hollow sections (CHS) under bending. This paper reviews the existing data on plastic Slenderness Limits for CHS. It describes an experimental investigation of the plastic flexural behaviour of Australian-produced cold-formed CHS. Plastic bending tests were performed on different sizes of CHS with d/t ranging from 13 to 39. The test results are compared with design rules given in various codes. A plastic Slenderness Limit ( λ{p}) is determined for cold-formed CHS. A model considering CHS ovalization is developed to predict the ultimate moment capacity of CHS subjected to pure bending.
Mohamed Elchalakani - One of the best experts on this subject based on the ideXlab platform.
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Plastic and yield Slenderness Limits for circular concrete filled tubes subjected to static pure bending
Thin-walled Structures, 2016Co-Authors: Mohamed Elchalakani, Ali Karrech, Mostafa Fahmi Hassanein, Bo YangAbstract:Abstract The current Slenderness Limits in international design codes are often based on certain rotation capacities obtained from plastic bending tests of Concrete Filled Tubes (CFT). In the past, a plastic Slenderness Limit of λs=188 was obtained by the first author based on a fracture rotation Limit of the steel tube. However, such Limit may be questionable being brittle and insufficient for plastic design of CFT members, sub-assemblies and frames where adequate strain/deformation ductility is required. The main aims of this paper are to present (i) a new method to determine new ductile Slenderness Limits suitable for plastic design of structures based on the measured strains in plastic bending tests on CFT; (ii) a closed-form solution for the elastic and inelastic buckling strains of CFT under pure bending using a new simplified energy approach employing the well-known Ritz method. The critical strains obtained from such analysis were used to derive new Slenderness Limits for CFT; and (iii) finite element modelling of CFT and compare the experimental and numerical moment-rotation responses. The effect of concrete filling on the post-buckling strength of restrained tubes is quantified. The current design rules for unrestrained Circular Hollow Sections (CHS) in steel specifications are also compared with the restrained strength obtained from the tests. Two new compact and yield Slenderness Limits were derived based on the strength corresponds to the appearance of the plastic ripples during the test. The experimentally obtained and the theoretically derived Slenderness Limits are compared against the available Limits in the design codes and standards. The newly derived compact Limit of λp=79 was found in a good agreement with λp=72 specified for CFT in the ANSI/AISC 360-10 specification. However, the new yield Limit of λy=150 was found considerably lower than λy=254 for CFT specified in the ANSI/AISC 360-10.
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Tests on concrete filled double-skin (CHS outer and SHS inner) composite short columns under axial compression
Thin-walled Structures, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:This paper presents stub columns tests on concrete-filled double skin sandwich tubes (CFDT) constructed using cold-formed steel tubes. The annulus is filled with micro high-strength concrete having compressive cylinder strength of 64 MPa. The outer skin is made of circular hollow sections (CHS), while the inner skin is made of square hollow sections (SHS). Eight different section sizes were used for the outer skin with diameter-to-thickness ratio ranging from 19 to 55. Three section sizes were chosen for the inner skin with width-to-thickness ratio in the range of 20 to 26. The CFDT construction was found to have significant increase in strength, ductility and energy absorption over the outer jacket. A simplified formula is derived to determine the compressive capacity of CFDT and compared against the current design rules. The proposed formula was found in good agreement with experimental results. This paper also verifies the yield Slenderness Limit (λey) of 82 specified in AS 4100 for cold-formed CHS stub columns.
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Tests on concrete filled double-skin (CHS outer and SHS inner) composite short columns under axial compression
Thin-Walled Structures, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:This paper presents stub columns tests on concrete-filled double skin sandwich tubes (CFDT) constructed using cold-formed steel tubes. The annulus is filled with micro high-strength concrete having compressive cylinder strength of 64 MPa. The outer skin is made of circular hollow sections (CHS), while the inner skin is made of square hollow sections (SHS). Eight different section sizes were used for the outer skin with diameter-to-thickness ratio ranging from 19 to 55. Three section sizes were chosen for the inner skin with width-to-thickness ratio in the range of 20 to 26. The CFDT construction was found to have significant increase in strength, ductility and energy absorption over the outer jacket. A simplified formula is derived to determine the compressive capacity of CFDT and compared against the current design rules. The proposed formula was found in good agreement with experimental results. This paper also verifies the yield Slenderness Limit (λey) of 82 specified in AS 4100 for cold-formed CHS stub columns. © 2002 Elsevier Science Ltd. All rights reserved.
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Plastic Slenderness Limits for Cold-formed Circular Hollow Sections
Australian Journal of Structural Engineering, 2002Co-Authors: Mohamed Elchalakani, Xiao Ling Zhao, Raphael GrzebietaAbstract:There are significant differences in d/t Limits recommended in various codes for circular hollow sections (CHS) under bending. This paper reviews the existing data on plastic Slenderness Limits for CHS. It describes an experimental investigation of the plastic flexural behaviour of Australian-produced cold-formed CHS. Plastic bending tests were performed on different sizes of CHS with d/t ranging from 13 to 39. The test results are compared with design rules given in various codes. A plastic Slenderness Limit ( λ{p}) is determined for cold-formed CHS. A model considering CHS ovalization is developed to predict the ultimate moment capacity of CHS subjected to pure bending.
Thomas Beitleman - One of the best experts on this subject based on the ideXlab platform.
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Slenderness Limit for hybrid frp concrete columns
Journal of Composites for Construction, 2001Co-Authors: Amir Mirmiran, Mohsen Shahawy, Thomas BeitlemanAbstract:Due to confinement effects, concrete-filled fiber-reinforced polymer (FRP) tubes have an enhanced performance comparable to conventionally reinforced concrete members. However, the strength and ductility enhancements may result in slender sections, which may be susceptible to instability or geometric and loading imperfections. Because stiffness of FRP is less than that of steel, designers cannot directly use current specifi- cations to size compression members. Uniaxial compression tests on a total of seven hybrid columns, with Slenderness ratios up to 36, showed that strength is reduced by as much as 71% of the equivalent short column, and the axial and hoop strains are reduced by as much as 85 and 87%, respectively. These significant reductions result in underutilization of confinement in slender columns. An analytical tool with an incremental approach was developed and compared favorably with test results. A parametric study was carried out, which showed the modulus of elasticity of the tube to have a pronounced effect on the Slenderness Limit of the column. A new equation was proposed for the Slenderness Limit of hybrid columns based on a maximum of 5% strength reduc- tion.
J G Teng - One of the best experts on this subject based on the ideXlab platform.
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Slenderness Limit for short frp confined circular rc columns
Journal of Composites for Construction, 2012Co-Authors: T Jiang, J G TengAbstract:Strengthening of RC columns through lateral confinement provided by external fiber-reinforced polymer (FRP) jackets (or wraps) has become an increasingly popular technique over the past decade. Nevertheless, relevant design provisions in existing design guidelines are only concerned with the design of FRP jackets for short columns in which the Slenderness effect is negligible. Even for the safe application of the existing design provisions for short columns, there is an urgent need to define a Slenderness Limit for short FRP-confined columns. This paper proposes such a Slenderness Limit expression based on the numerical results of a comprehensive parametric study that investigates the effects of various parameters on the Slenderness Limit using a recently developed theoretical column model. An important feature of the proposed expression is that it separates the effect of FRP confinement on the Slenderness Limit from the effect of other parameters. This feature allows existing Slenderness Limit expressions for short RC columns of different forms to be readily upgraded for use in the design of FRP-confined RC columns by incorporating the part dealing with the effect of FRP confinement in the proposed expression.
