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Togay Ozbakkaloglu - One of the best experts on this subject based on the ideXlab platform.
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behavior of square and rectangular ultra high Strength concrete filled frp tubes under axial compression
Composites Part B-engineering, 2013Co-Authors: Togay OzbakkalogluAbstract:Abstract This paper presents results of an experimental program undertaken to investigate the behavior of square and rectangular ultra high-Strength concrete (UHSC)-filled fiber reinforced polymer (FRP) tubes (UHSCFFTs) under axial compression. The effects of the amount of confinement, cross-sectional aspect ratio and corner radius were investigated experimentally through the tests of 24 concrete-filled FRP tubes (CFFTs) that were manufactured using unidirectional carbon fiber sheets and UHSC with 108 MPa Average Compressive Strength. As the first experimental investigation on the axial Compressive behavior of square and rectangular UHSCFFTs, the results of the study reported in this paper allows a number of significant conclusions to be drawn. Of primary importance, test results indicate that sufficiently confined square and rectangular UHSCFFTs can exhibit highly ductile behavior. The results also indicate that confinement effectiveness of FRP tubes increases with an increase in corner radius and as sectional aspect ratio approaches unity. It is found that UHSCFFTs having tubes of low confinement effectiveness may experience significant Strength loss along the initial portions of the second branches on their stress–strain curves. Furthermore, it is observed that the behavior of UHSCFFTs at this region differs from their normal-Strength concrete counterparts and is more sensitive to the effectiveness of confining tube. The second half of the paper presents the performance assessment of the existing FRP-confined concrete models in predicting the ultimate conditions of the HSC and UHSCFFTs. The results of this assessment demonstrate that the existing models provide unconservative estimates for specimens with higher concrete Strengths. To address this, a new model that was developed on the basis of a comprehensive experimental test database and is applicable to both NSC and HSC of Strengths up to 120 MPa is proposed. The model comparisons demonstrate that the proposed model provides significantly improved predictions of the ultimate conditions of FRP-confined HSC compared to the existing models.
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axial Compressive behavior of square and rectangular high Strength concrete filled frp tubes
Journal of Composites for Construction, 2013Co-Authors: Togay OzbakkalogluAbstract:AbstractThis paper presents results of an experimental study on the behavior of square and rectangular high-Strength concrete (HSC)-filled fiber-reinforced polymer (FRP) tubes (HSCFFT) under concentric compression. The effects of the tube thickness, sectional aspect ratio, and corner radius on the axial Compressive behavior of concrete-filled FRP tubes (CFFT) were investigated experimentally through the tests of 24 CFFTs that were manufactured using unidirectional carbon fiber sheets and high-Strength concrete with 78 MPa Average Compressive Strength. As the first experimental investigation on the axial Compressive behavior of square and rectangular HSCFFTs, the results of the study reported in this paper allow a number of significant conclusions to be drawn. First and foremost, test results indicate that sufficiently confined square and rectangular HSCFFTs can exhibit highly ductile behavior. The results also indicate that confinement effectiveness of FRP tubes increases with an increase in corner radius...
Alain Bourmaud - One of the best experts on this subject based on the ideXlab platform.
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Compressive Strength of flax fibre bundles within the stem and comparison with unidirectional flax epoxy composites
Industrial Crops and Products, 2019Co-Authors: Christophe Baley, Camille Goudenhooft, Patrick Perre, Floran Pierre, Alain BourmaudAbstract:Flax (Linum usitatissimum L.) fibres are commonly used as reinforcement of composite materials. Nevertheless, literature shows that the Compressive Strength of flax-based composites is rather modest compared with materials reinforced by synthetic fibres. The present article investigates the Compressive Strength of flax fibre bundles both within the stems and in unidirectional (UD) composites. In this way, an optimised arrangement of fibre bundles inside the plant is assumed. Damage mechanisms are found to be similar in the stem and within flax-based UD materials, namely by buckling of fibre bundles, a typical failure mechanism of UD composites. Inside the stems, this phenomenon is highlighted by nanotomography, which underlines the key role of the woody core in the buckling resistance of the plant. For UD, failure can also be studied by scanning electron microscopy (SEM). The same ranges of Average Compressive Strength values are estimated for flax fibre bundles, being 206 MPa within the stem and 242 MPa within UD composites. Finally, this study highlights that, if a flax stem is an optimised natural structure, the Compressive Strength of flax fibre bundles seems to be a limiting factor for structural applications of flax-based composite materials.
Joonmo Choung - One of the best experts on this subject based on the ideXlab platform.
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assessment of residual ultimate Strength of vlcc according to damage extents and Average Compressive Strength of stiffened panel
ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014Co-Authors: Jimyung Nam, Joonmo Choung, Seyung Park, Sungwon YoonAbstract:This paper presents the prediction of residual ultimate Strength of a very large crude oil carrier considering damage extents due to collision and grounding accidents. In order to determine extents of damage, two types of probabilistic approaches are employed: deterministic approach based on regulations based on ABS [1], DNV [2], and MARPOL [3] and probabilistic approach based on IMO probability density functions (PDFs) (IMO guidelines [4]). Hull girder ultimate Strength is calculated using Smith method which is dependent on how much Average Compressive Strength of stiffened panel is accurate. For this reason, this paper uses two different methods to predict Average Compressive Strength of stiffened panel composing hull girder section: CSR formulas and nonlinear FEA. Calculated Average Compressive Strength curves using CSR formulas (IACS [5, 6]) and nonlinear FEA are imported by an in-house software UMADS. Residual ultimate moment capacities are presented for various heeling angles from 0° (sagging) to 180° (hogging) by 15° increments considering possible flooding scenarios. Three regulations and IMO guidelines yield minimum of reduction ratios of hull girder moment capacity (minimum of damage indices) approximately at heeling angles 90° (angle of horizontal moment) and 180° (angle of hogging moment), respectively, because damage area is located farthest from neutral axis.Copyright © 2014 by ASME
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Lateral pressure effect on Average Compressive Strength of stiffened panels for in-service vessels
Ships and Offshore Structures, 2012Co-Authors: Joonmo Choung, Jun-bum Park, Chang Yong SongAbstract:This paper presents the estimation of the Average Compressive Strengths of three types of stiffened panels under axial compression and lateral pressure based on simplified formulae in the CSR for tankers (common structural rules for double hull oil tankers) and nonlinear finite element analyses (FEAs). Basic scenarios are determined based on the slenderness ratios of the stiffened panels used for in-service ships. Secondary scenarios are subdivided by external pressures that are applied to finite element model by increasing 1 bar, assuming 30 m water height. The total number of FEAs for flat bar (FB)-, angle bar (AB)- and tee bar (TB)-stiffened panels is 189. FEA results show that the existence of pressure can cause a significant reduction of ultimate Strength, while CSR formulae do not take into account the effect of lateral pressure. The lateral pressure is more detrimental to the ultimate Strength of stiffened panels with a higher column slenderness ratio than those with a smaller column slenderness ra...
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Average Compressive Strengths of stiffened plates for in service vessels under lateral pressure
Journal of The Society of Naval Architects of Korea, 2011Co-Authors: Joonmo Choung, Sangik Jeon, Minseong Lee, Jimyung NamAbstract:This paper presents estimation of Average Compressive Strengths of three types of stiffened panels under lateral pressure and axial compression based on simplified formulas from CSRs and nonlinear FEAs. FEA scenarios are prepared based on the slenderness ratios of the stiffened panels used for in-service vessels. The seven step lateral pressures by 1bar increment are imposed on FE models assuming maximum 30m water height. The number of FEAs for FB-, AB-, and TB-stiffened panels is totally 189 times. FEA results show that existence of pressure can evolves significant reduction of ultimate Strengths, meanwhile CSR formulas do not take into account the lateral pressure effect. Lateral pressure acting on the stiffened panel with higher column slenderness ratio more reduces the ultimate Strengths than those with smaller column slenderness ratio. A new concept of relative Average Compressive strain energy instead of the ultimate Strength is introduced in order to rationally compare the Average Compressive Strength through complete Compressive straining regime. The differences of the ultimate Strengths between CSR formulas and FEA results are relatively small for FB- and AB-stiffened panels, but larger discrepancies of relative Average Compressive strain energies are shown.
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slenderness ratio distributions and Average Compressive Strengths of stiffened plates used for in service vessels
Journal of The Society of Naval Architects of Korea, 2010Co-Authors: Joonmo Choung, Sangik Jeon, Taebum HaAbstract:This paper deals with two contents: first, distributions of plate slenderness ratios, stiffened plate slenderness ratios, and stiffener slenderness ratios, which include dimensions and material variables of stiffened plates, of stiffened plates of large-sized in-service vessels, and, second, comparison of Compressive Strengths. The investigated vessels consist of 59 tankers, 49 bulkers, 28 product carriers, 15 container carriers, and 12 multi-purpose vessels. The tankers are ranged from handymax class to VLCC and larger than Suezmax class. The sizes of the bulkers are 20K to 200K deadweight. The maximum size of containers is less than 5000TEU class. Two parameters for normal distributions of the slenderness ratios (mean and standard deviation) are suggested and probable ranges of the slenderness ratios are also graphically presented. The ultimate Strengths of the stiffened plates are presented using the various simplified formulas and nonlinear FEAs. As well, Average Compressive Strength curves, which are necessary for the estimation of the hull girder moment capacities, are proposed. It is proved that formulas for stiffened plates in CSR overestimate slightly in overall Average strain range. Mode5 formula (plate buckling mode) in CSR show unreasonably conservative results with respect to the ultimate Strengths rather than post-ultimate Average Compressive Strengths.
Jimyung Nam - One of the best experts on this subject based on the ideXlab platform.
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assessment of residual ultimate Strength of vlcc according to damage extents and Average Compressive Strength of stiffened panel
ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014Co-Authors: Jimyung Nam, Joonmo Choung, Seyung Park, Sungwon YoonAbstract:This paper presents the prediction of residual ultimate Strength of a very large crude oil carrier considering damage extents due to collision and grounding accidents. In order to determine extents of damage, two types of probabilistic approaches are employed: deterministic approach based on regulations based on ABS [1], DNV [2], and MARPOL [3] and probabilistic approach based on IMO probability density functions (PDFs) (IMO guidelines [4]). Hull girder ultimate Strength is calculated using Smith method which is dependent on how much Average Compressive Strength of stiffened panel is accurate. For this reason, this paper uses two different methods to predict Average Compressive Strength of stiffened panel composing hull girder section: CSR formulas and nonlinear FEA. Calculated Average Compressive Strength curves using CSR formulas (IACS [5, 6]) and nonlinear FEA are imported by an in-house software UMADS. Residual ultimate moment capacities are presented for various heeling angles from 0° (sagging) to 180° (hogging) by 15° increments considering possible flooding scenarios. Three regulations and IMO guidelines yield minimum of reduction ratios of hull girder moment capacity (minimum of damage indices) approximately at heeling angles 90° (angle of horizontal moment) and 180° (angle of hogging moment), respectively, because damage area is located farthest from neutral axis.Copyright © 2014 by ASME
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Average Compressive Strengths of stiffened plates for in service vessels under lateral pressure
Journal of The Society of Naval Architects of Korea, 2011Co-Authors: Joonmo Choung, Sangik Jeon, Minseong Lee, Jimyung NamAbstract:This paper presents estimation of Average Compressive Strengths of three types of stiffened panels under lateral pressure and axial compression based on simplified formulas from CSRs and nonlinear FEAs. FEA scenarios are prepared based on the slenderness ratios of the stiffened panels used for in-service vessels. The seven step lateral pressures by 1bar increment are imposed on FE models assuming maximum 30m water height. The number of FEAs for FB-, AB-, and TB-stiffened panels is totally 189 times. FEA results show that existence of pressure can evolves significant reduction of ultimate Strengths, meanwhile CSR formulas do not take into account the lateral pressure effect. Lateral pressure acting on the stiffened panel with higher column slenderness ratio more reduces the ultimate Strengths than those with smaller column slenderness ratio. A new concept of relative Average Compressive strain energy instead of the ultimate Strength is introduced in order to rationally compare the Average Compressive Strength through complete Compressive straining regime. The differences of the ultimate Strengths between CSR formulas and FEA results are relatively small for FB- and AB-stiffened panels, but larger discrepancies of relative Average Compressive strain energies are shown.
Christophe Baley - One of the best experts on this subject based on the ideXlab platform.
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Compressive Strength of flax fibre bundles within the stem and comparison with unidirectional flax epoxy composites
Industrial Crops and Products, 2019Co-Authors: Christophe Baley, Camille Goudenhooft, Patrick Perre, Floran Pierre, Alain BourmaudAbstract:Flax (Linum usitatissimum L.) fibres are commonly used as reinforcement of composite materials. Nevertheless, literature shows that the Compressive Strength of flax-based composites is rather modest compared with materials reinforced by synthetic fibres. The present article investigates the Compressive Strength of flax fibre bundles both within the stems and in unidirectional (UD) composites. In this way, an optimised arrangement of fibre bundles inside the plant is assumed. Damage mechanisms are found to be similar in the stem and within flax-based UD materials, namely by buckling of fibre bundles, a typical failure mechanism of UD composites. Inside the stems, this phenomenon is highlighted by nanotomography, which underlines the key role of the woody core in the buckling resistance of the plant. For UD, failure can also be studied by scanning electron microscopy (SEM). The same ranges of Average Compressive Strength values are estimated for flax fibre bundles, being 206 MPa within the stem and 242 MPa within UD composites. Finally, this study highlights that, if a flax stem is an optimised natural structure, the Compressive Strength of flax fibre bundles seems to be a limiting factor for structural applications of flax-based composite materials.
