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Merih Kucukler - One of the best experts on this subject based on the ideXlab platform.

  • Design of web-tapered steel beams against lateral-torsional buckling through a Stiffness Reduction method
    Engineering Structures, 2019
    Co-Authors: Merih Kucukler, Leroy Gardner
    Abstract:

    Abstract A Stiffness Reduction method for the lateral-torsional buckling (LTB) assessment of welded web-tapered steel beams is presented in this study. The method is implemented by (i) modelling a tapered steel beam using elastic beam finite elements specifically developed to represent the elastic instability response of tapered steel members, (ii) reducing the Young’s modulus E and shear modulus G of each element through a Stiffness Reduction function considering the bending moments and cross-section properties at the middle of each element and (iii) performing an elastic Linear Buckling Analysis of the beam with reduced Stiffness, referred to as LBA-SR herein. Since the adverse influence of the development of plasticity and imperfections on the ultimate member strengths are fully accounted for through Stiffness Reduction, the presented method does not require any further global instability assessment using member design equations; thus, the proposed method is both direct and practical. Verification of the method is shown for a wide range of web-tapered steel beams using results from nonlinear shell finite element modelling.

  • Design of hot-finished tubular steel members using a Stiffness Reduction method
    Journal of Constructional Steel Research, 2019
    Co-Authors: Merih Kucukler, Leroy Gardner
    Abstract:

    Abstract A Stiffness Reduction method (SRM) for the design of hot-finished tubular steel members is presented in this paper. Stiffness Reduction functions that fully capture the adverse influence of imperfections and plasticity on member stability are developed. The proposed SRM is implemented by (i) reducing the flexural Stiffness (EI) of the member using the developed Stiffness Reduction functions, (ii) performing elastic Linear Buckling Analysis (LBA) and Geometrically Nonlinear Analysis (GNA) of the member with reduced flexural Stiffness and (iii) making cross-section strength checks and ensuring that the lowest buckling load amplifier from LBA is greater than or equal to 1.0. Owing to the full allowance for the spread of plasticity, residual stresses and geometrical imperfections through Stiffness Reduction and instability effects through LBA and GNA, the proposed approach offers an enhanced and more direct assessment of structural behaviour relative to traditional design where structural analysis is accompanied by member design equations, effective lengths and the notional load concept. The proposed method is verified against nonlinear finite element modelling for a large number of tubular steel members. Comparisons of the proposed approach against the methods recommended in the European structural steel design code EN 1993-1-1 for the design of tubular members are also provided.

  • Design of laterally restrained web-tapered steel structures through a Stiffness Reduction method
    Journal of Constructional Steel Research, 2018
    Co-Authors: Merih Kucukler, Leroy Gardner
    Abstract:

    A Stiffness Reduction method for the design of laterally restrained web-tapered steel structures fabricated through the welding of individual steel plates is presented in this paper. Stiffness Reduction functions for welded members, accounting fully for the deleterious influence of the spread of plasticity and imperfections on the structural resistance, are developed. The method is implemented through (i) dividing tapered members into prismatic segments along their lengths, (ii) reducing the flexural Stiffness of each segment by means of the developed Stiffness Reduction functions considering the first-order forces and cross-section properties of each segment, (iii) performing Geometrically Nonlinear Analysis and (iv) making cross-section strength checks. Essentially, it is proposed to replace the current typical approach to structural design of conducting a simple elastic (with nominal Stiffness) structural analysis followed by elaborate member checks with an integrated process utilising more sophisticated second-order analysis (with Stiffness Reduction) but very simple design checks. The distribution of internal forces within the structure is captured more accurately due to the allowance for imperfections, residual stresses and plasticity through Stiffness Reduction and the allowance for frame and member instability effects through the use of second-order analysis. The need for determining effective lengths and for conducting member buckling checks is also eliminated. Verification of the proposed approach against the results obtained from nonlinear shell finite element modelling is presented for various tapering geometries, slenderness values and loading conditions. Assessment of the proposed method against the European and North American steel design codes for tapered steel structures is also provided.

  • Stiffness Reduction method for the in-plane design of steel frames
    2016
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    A Stiffness Reduction method for the in-plane design of steel frames is proposed in this paper. The proposed method is performed by (i) reducing the flexural Stiffnesses of the members of a frame on the basis of the first-order forces they withstand and (ii) carrying out Geometrically Nonlinear Analysis. The ultimate capacity of the structure is defined as the point at which the ultimate strength of the most heavily loaded cross-section is reached. Ow-ing to the full consideration of the deleterious influence of the spread of plasticity and imper-fections through Stiffness Reduction, the proposed approach eliminates the need of using member design equations or modelling member out-of-straightnesses; only cross-section strength checks are required. The verification of the proposed approach against results from the nonlinear finite element modelling of a series of benchmark frames is presented. Copyright ©: SDSS'2016.

  • Development and assessment of a practical Stiffness Reduction method for the in-plane design of steel frames
    Journal of Constructional Steel Research, 2016
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    In this paper, the development and assessment of a Stiffness Reduction method for the in-plane design of steel frames is presented. The adopted Stiffness Reduction approach is implemented by reducing the flexural Stiffnesses (EI) of the members of a steel frame by considering the first-order forces they are subjected to through the Stiffness Reduction functions and performing Geometrically Nonlinear Analysis (i.e. second-order elastic analysis). Since the presented approach uses Stiffness Reduction functions that fully take into account the deleterious influence of imperfections and the spread of plasticity on the structural response and member strengths, it obviates the need of using member design equations, and only requires cross-section strength checks. The accuracy of the presented approach is illustrated for individual steel members and non-redundant and redundant benchmark steel frames from the literature. In all the considered cases, the presented method is verified against the results obtained from nonlinear finite element modelling. A comparison of the presented approach against the notional load method of the European structural steel design code EN 1993-1-1 and the direct analysis method of the US structural steel design code AISC 360-10 is also provided.

Leroy Gardner - One of the best experts on this subject based on the ideXlab platform.

  • Design of web-tapered steel beams against lateral-torsional buckling through a Stiffness Reduction method
    Engineering Structures, 2019
    Co-Authors: Merih Kucukler, Leroy Gardner
    Abstract:

    Abstract A Stiffness Reduction method for the lateral-torsional buckling (LTB) assessment of welded web-tapered steel beams is presented in this study. The method is implemented by (i) modelling a tapered steel beam using elastic beam finite elements specifically developed to represent the elastic instability response of tapered steel members, (ii) reducing the Young’s modulus E and shear modulus G of each element through a Stiffness Reduction function considering the bending moments and cross-section properties at the middle of each element and (iii) performing an elastic Linear Buckling Analysis of the beam with reduced Stiffness, referred to as LBA-SR herein. Since the adverse influence of the development of plasticity and imperfections on the ultimate member strengths are fully accounted for through Stiffness Reduction, the presented method does not require any further global instability assessment using member design equations; thus, the proposed method is both direct and practical. Verification of the method is shown for a wide range of web-tapered steel beams using results from nonlinear shell finite element modelling.

  • Design of hot-finished tubular steel members using a Stiffness Reduction method
    Journal of Constructional Steel Research, 2019
    Co-Authors: Merih Kucukler, Leroy Gardner
    Abstract:

    Abstract A Stiffness Reduction method (SRM) for the design of hot-finished tubular steel members is presented in this paper. Stiffness Reduction functions that fully capture the adverse influence of imperfections and plasticity on member stability are developed. The proposed SRM is implemented by (i) reducing the flexural Stiffness (EI) of the member using the developed Stiffness Reduction functions, (ii) performing elastic Linear Buckling Analysis (LBA) and Geometrically Nonlinear Analysis (GNA) of the member with reduced flexural Stiffness and (iii) making cross-section strength checks and ensuring that the lowest buckling load amplifier from LBA is greater than or equal to 1.0. Owing to the full allowance for the spread of plasticity, residual stresses and geometrical imperfections through Stiffness Reduction and instability effects through LBA and GNA, the proposed approach offers an enhanced and more direct assessment of structural behaviour relative to traditional design where structural analysis is accompanied by member design equations, effective lengths and the notional load concept. The proposed method is verified against nonlinear finite element modelling for a large number of tubular steel members. Comparisons of the proposed approach against the methods recommended in the European structural steel design code EN 1993-1-1 for the design of tubular members are also provided.

  • Design of laterally restrained web-tapered steel structures through a Stiffness Reduction method
    Journal of Constructional Steel Research, 2018
    Co-Authors: Merih Kucukler, Leroy Gardner
    Abstract:

    A Stiffness Reduction method for the design of laterally restrained web-tapered steel structures fabricated through the welding of individual steel plates is presented in this paper. Stiffness Reduction functions for welded members, accounting fully for the deleterious influence of the spread of plasticity and imperfections on the structural resistance, are developed. The method is implemented through (i) dividing tapered members into prismatic segments along their lengths, (ii) reducing the flexural Stiffness of each segment by means of the developed Stiffness Reduction functions considering the first-order forces and cross-section properties of each segment, (iii) performing Geometrically Nonlinear Analysis and (iv) making cross-section strength checks. Essentially, it is proposed to replace the current typical approach to structural design of conducting a simple elastic (with nominal Stiffness) structural analysis followed by elaborate member checks with an integrated process utilising more sophisticated second-order analysis (with Stiffness Reduction) but very simple design checks. The distribution of internal forces within the structure is captured more accurately due to the allowance for imperfections, residual stresses and plasticity through Stiffness Reduction and the allowance for frame and member instability effects through the use of second-order analysis. The need for determining effective lengths and for conducting member buckling checks is also eliminated. Verification of the proposed approach against the results obtained from nonlinear shell finite element modelling is presented for various tapering geometries, slenderness values and loading conditions. Assessment of the proposed method against the European and North American steel design codes for tapered steel structures is also provided.

  • Stiffness Reduction method for the in-plane design of steel frames
    2016
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    A Stiffness Reduction method for the in-plane design of steel frames is proposed in this paper. The proposed method is performed by (i) reducing the flexural Stiffnesses of the members of a frame on the basis of the first-order forces they withstand and (ii) carrying out Geometrically Nonlinear Analysis. The ultimate capacity of the structure is defined as the point at which the ultimate strength of the most heavily loaded cross-section is reached. Ow-ing to the full consideration of the deleterious influence of the spread of plasticity and imper-fections through Stiffness Reduction, the proposed approach eliminates the need of using member design equations or modelling member out-of-straightnesses; only cross-section strength checks are required. The verification of the proposed approach against results from the nonlinear finite element modelling of a series of benchmark frames is presented. Copyright ©: SDSS'2016.

  • Development and assessment of a practical Stiffness Reduction method for the in-plane design of steel frames
    Journal of Constructional Steel Research, 2016
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    In this paper, the development and assessment of a Stiffness Reduction method for the in-plane design of steel frames is presented. The adopted Stiffness Reduction approach is implemented by reducing the flexural Stiffnesses (EI) of the members of a steel frame by considering the first-order forces they are subjected to through the Stiffness Reduction functions and performing Geometrically Nonlinear Analysis (i.e. second-order elastic analysis). Since the presented approach uses Stiffness Reduction functions that fully take into account the deleterious influence of imperfections and the spread of plasticity on the structural response and member strengths, it obviates the need of using member design equations, and only requires cross-section strength checks. The accuracy of the presented approach is illustrated for individual steel members and non-redundant and redundant benchmark steel frames from the literature. In all the considered cases, the presented method is verified against the results obtained from nonlinear finite element modelling. A comparison of the presented approach against the notional load method of the European structural steel design code EN 1993-1-1 and the direct analysis method of the US structural steel design code AISC 360-10 is also provided.

Lorenzo Macorini - One of the best experts on this subject based on the ideXlab platform.

  • Stiffness Reduction method for the in-plane design of steel frames
    2016
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    A Stiffness Reduction method for the in-plane design of steel frames is proposed in this paper. The proposed method is performed by (i) reducing the flexural Stiffnesses of the members of a frame on the basis of the first-order forces they withstand and (ii) carrying out Geometrically Nonlinear Analysis. The ultimate capacity of the structure is defined as the point at which the ultimate strength of the most heavily loaded cross-section is reached. Ow-ing to the full consideration of the deleterious influence of the spread of plasticity and imper-fections through Stiffness Reduction, the proposed approach eliminates the need of using member design equations or modelling member out-of-straightnesses; only cross-section strength checks are required. The verification of the proposed approach against results from the nonlinear finite element modelling of a series of benchmark frames is presented. Copyright ©: SDSS'2016.

  • Development and assessment of a practical Stiffness Reduction method for the in-plane design of steel frames
    Journal of Constructional Steel Research, 2016
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    In this paper, the development and assessment of a Stiffness Reduction method for the in-plane design of steel frames is presented. The adopted Stiffness Reduction approach is implemented by reducing the flexural Stiffnesses (EI) of the members of a steel frame by considering the first-order forces they are subjected to through the Stiffness Reduction functions and performing Geometrically Nonlinear Analysis (i.e. second-order elastic analysis). Since the presented approach uses Stiffness Reduction functions that fully take into account the deleterious influence of imperfections and the spread of plasticity on the structural response and member strengths, it obviates the need of using member design equations, and only requires cross-section strength checks. The accuracy of the presented approach is illustrated for individual steel members and non-redundant and redundant benchmark steel frames from the literature. In all the considered cases, the presented method is verified against the results obtained from nonlinear finite element modelling. A comparison of the presented approach against the notional load method of the European structural steel design code EN 1993-1-1 and the direct analysis method of the US structural steel design code AISC 360-10 is also provided.

  • Flexural–torsional buckling assessment of steel beam-columns through a Stiffness Reduction method
    Engineering Structures, 2015
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    In this paper, a Stiffness Reduction method for the flexural–torsional buckling assessment of steel beam–columns subjected to major axis bending and axial compression is presented. The proposed method is applied by reducing the Young’s E and shear G moduli through the developed Stiffness Reduction functions and performing Linear Buckling Analysis. To account for second-order forces induced prior to buckling, the in-plane (in the plane of bending) and out-of-plane analyses of a member are separated and Stiffness Reduction for the out-of-plane instability assessment is applied on the basis of member forces determined from the in-plane analysis. Since the developed Stiffness Reduction functions fully take into account the detrimental influence of imperfections and spread of plasticity, the proposed method does not require the use of member design equations, thus leading to practical design. For the purpose of verifying this approach, the strength predictions determined through the proposed Stiffness Reduction method are compared against those obtained from nonlinear finite element modelling for a large number of regular, irregular, single and multi-span beam–columns.

  • flexural torsional buckling assessment of steel beam columns through a Stiffness Reduction method
    Engineering Structures, 2015
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    In this paper, a Stiffness Reduction method for the flexural–torsional buckling assessment of steel beam–columns subjected to major axis bending and axial compression is presented. The proposed method is applied by reducing the Young’s E and shear G moduli through the developed Stiffness Reduction functions and performing Linear Buckling Analysis. To account for second-order forces induced prior to buckling, the in-plane (in the plane of bending) and out-of-plane analyses of a member are separated and Stiffness Reduction for the out-of-plane instability assessment is applied on the basis of member forces determined from the in-plane analysis. Since the developed Stiffness Reduction functions fully take into account the detrimental influence of imperfections and spread of plasticity, the proposed method does not require the use of member design equations, thus leading to practical design. For the purpose of verifying this approach, the strength predictions determined through the proposed Stiffness Reduction method are compared against those obtained from nonlinear finite element modelling for a large number of regular, irregular, single and multi-span beam–columns.

  • lateral torsional buckling assessment of steel beams through a Stiffness Reduction method
    Journal of Constructional Steel Research, 2015
    Co-Authors: Merih Kucukler, Leroy Gardner, Lorenzo Macorini
    Abstract:

    This paper presents a Stiffness Reduction approach utilising Linear Buckling Analysis (LBA) with developed Stiffness Reduction functions for the lateral–torsional buckling (LTB) assessment of steel beams. A Stiffness Reduction expression is developed for the LTB assessment of beams subjected to uniform bending and modified for the consideration of moment gradient effects on the development of plasticity. The proposed Stiffness Reduction method considers the influence of imperfections and plasticity on the response through the Reduction of the Young's modulus E and shear modulus G and obviates the need of using LTB buckling curves in design. The accuracy and practicality of the method are illustrated for regular, irregular, single and multi-span beams. In all of the considered cases, the proposed method is verified against the results obtained through nonlinear finite element modelling.

Shen Yanfei - One of the best experts on this subject based on the ideXlab platform.

  • Flexural Stiffness Reduction for stainless steel SHS and RHS members prone to local buckling
    'Elsevier BV', 2020
    Co-Authors: Shen Yanfei, Chacón Flores, Rolando Antonio
    Abstract:

    In this paper, flexural Stiffness Reduction factor formulations, applicable to stainless steel members with compact cold-formed square and rectangular hollow section (SHS and RHS), are extended to account for local buckling effects and initial localized imperfection (ω). Local buckling effects and the influence of ω are accounted for by means of reducing the gross section resistance using a strength Reduction factor ρ. ρ, determined by the Direct Analysis Method, depending on cross-section slenderness, is adopted. For in-plane stainless steel elements with non-compact and slender sections, results determined by the extended flexural Stiffness Reduction factor coupled with Geometrically Nonlinear Analysis (GNA) are verified against those determined by Geometrically and Materially Nonlinear Analysis with Imperfections (GMNIA). It is found that GNA with the extended flexural Stiffness Reduction factor (using beam element) generally achieves the accuracy of GMNIA (using shell element). Probabilistic studies based on 3D models with random ω are carried out to evaluate the effect of uncertainty in ω on the accuracy of GNA with the extended beam-column flexural Stiffness Reduction factor.The authors acknowledge the financial support provided by the Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente an acciones accidentales de sismo y fuego”, funded from the MINECO (Spain). The authors acknowledge financial support from China Scholarship Council.Peer ReviewedPostprint (author's final draft

  • Geometrically non-linear analysis with Stiffness Reduction for the stability design of stainless steel structures: application to members and planar frames
    'Elsevier BV', 2020
    Co-Authors: Shen Yanfei, Chacón Flores, Rolando Antonio
    Abstract:

    This paper focuses on the development of beam-column flexural Stiffness Reduction factor (tMN) applicable to the in-plane stability design of stainless steel beam-columns and frames with compact cold-formed square and rectangular hollow sections. The proposed tMN accounts for the deleterious influence of material non-linearity, residual stresses and member out-of-straightness. The use of a Geometrically Non-linear Analysis (GNA) with the proposed tMN eliminates the need for member buckling strength checks and thus, only cross-sectional strength checks are required. The proposed approach, aligned to AISC standards, is aimed at facilitating greater and more efficient use of stainless steel. Two types of tMN are proposed: analytical and approximate. The analytical tMN presumes knowing the maximum internal second order moment (Mr2) within a member. It is developed by means of extending the formulations for evaluating the elastic second order effects to the inelastic range. The accuracy of the analytical tMN is verified for beam-columns and sub-assemblages. Since in practical design Mr2 is not known in advance, an approximate expression of tMN, which is more likely to be used relative to the analytical tMN, is proposed by fitting variables to the analytically determined MN. The accuracy of the approximate tMN is verified for frames with different geometrical and loading configurations. Furthermore, the proposed approach is compared against the Direct Analysis Method (DM). Results show that, compared to the DM, GNA coupled with the approximate tMN provides improved estimations, since the proposed tMN can more accurately capture Stiffness Reduction resulted from material non-linearity and well capture additional second order effects due to material non-linearityPeer ReviewedPostprint (author's final draft

  • Geometrically non-linear analysis with Stiffness Reduction for the in-plane stability design of stainless steel frames
    Universitat Politècnica de Catalunya, 2019
    Co-Authors: Shen Yanfei
    Abstract:

    In AISC 360-16, the Direct Analysis Method (DM) has been set as the primary method for the stability design of frames. DM, considering initial global sway imperfection, is essentially Geometrically Non-linear Analysis (GNA) in which tangent modulus is used. The aim of this thesis is to provide Stiffness Reduction factor formulations for using GNA coupled with tangent modulus approach for the stability design of stainless steel frames. GNA with the proposed Stiffness Reduction factor is aligned to AISC 360-16 and it is aimed at facilitating greater and more efficient use of stainless steel. In accordance with current design standards, the ultimate limit state for this method is the formation of first plastic hinge, and the adequacy of the method is confirmed through member-based resistance checks.The focus of the thesis is the development of flexural Stiffness Reduction factor formulation for the in-plane stability design of stainless steel elements and frames with cold-formed square hollow section (SHS) and rectangular hollow section (RHS). The proposed beam-column Stiffness Reduction factor (tMN) accounts for the deleterious influence of material non-linearity, residual stresses and member out-of-straightness. The use of a GNA coupled with the proposed tMN eliminates the need for member buckling strength checks and thus, only cross-sectional strength checks are required.En la normativa Americana AISC 360-16, el método de análisis directo (DM) se ha establecido como el método principal en la verificación a inestabilidad de pórticos. El DM es esencialmente un análisis no lineal por la geometría (GNA) en el que se consideran las imperfecciones globales únicamente y se utiliza el módulo tangente. El objetivo de la tesis es proporcionar una formulación de rigidez reducida utilizando un análisis no lineal por la geometría para las verificaciones a inestabilidad de pórticos de acero inoxidable. El método propuesto se alinea con el AISC 360-16 y su objetivo es facilitar el uso del acero inoxidable en pórticos. De acuerdo con las normativas actuales, la capacidad última de un pórtico se define al formarse la primera rótula plástica y la verificación se plantea en base a la resistencia de los elementos aislados. El foco de la tesis se centra en el plantramiento de factores de reducción de rigidez a flexión de elementos tubulares de acero inoxidable conformados en frío (SHS y RHS) para el caso de diseño de pórticos cargados en su plano. Se propone un factor de reducción para elementos del tipo viga-columna mn el cual tiene en cuenta los efectos de la nolinealidad del material, las tensiones residuales y la imperfección del elemento. El uso de GNA conjuntamente con tMN permite verificar los diferentes elementos del pórtico solo a resistencia sin tener hacer las comprobaciones correspondientes a pandeo

  • Geometrically non-linear analysis with Stiffness Reduction for the in-plane stability design of stainless steel frames
    Universitat Politècnica de Catalunya, 2019
    Co-Authors: Shen Yanfei
    Abstract:

    In AISC 360-16, the Direct Analysis Method (DM) has been set as the primary method for the stability design of frames. DM, considering initial global sway imperfection, is essentially Geometrically Non-linear Analysis (GNA) in which tangent modulus is used. The aim of this thesis is to provide Stiffness Reduction factor formulations for using GNA coupled with tangent modulus approach for the stability design of stainless steel frames. GNA with the proposed Stiffness Reduction factor is aligned to AISC 360-16 and it is aimed at facilitating greater and more efficient use of stainless steel. In accordance with current design standards, the ultimate limit state for this method is the formation of first plastic hinge, and the adequacy of the method is confirmed through member-based resistance checks.The focus of the thesis is the development of flexural Stiffness Reduction factor formulation for the in-plane stability design of stainless steel elements and frames with cold-formed square hollow section (SHS) and rectangular hollow section (RHS). The proposed beam-column Stiffness Reduction factor (tMN) accounts for the deleterious influence of material non-linearity, residual stresses and member out-of-straightness. The use of a GNA coupled with the proposed tMN eliminates the need for member buckling strength checks and thus, only cross-sectional strength checks are required.En la normativa Americana AISC 360-16, el método de análisis directo (DM) se ha establecido como el método principal en la verificación a inestabilidad de pórticos. El DM es esencialmente un análisis no lineal por la geometría (GNA) en el que se consideran las imperfecciones globales únicamente y se utiliza el módulo tangente. El objetivo de la tesis es proporcionar una formulación de rigidez reducida utilizando un análisis no lineal por la geometría para las verificaciones a inestabilidad de pórticos de acero inoxidable. El método propuesto se alinea con el AISC 360-16 y su objetivo es facilitar el uso del acero inoxidable en pórticos. De acuerdo con las normativas actuales, la capacidad última de un pórtico se define al formarse la primera rótula plástica y la verificación se plantea en base a la resistencia de los elementos aislados. El foco de la tesis se centra en el plantramiento de factores de reducción de rigidez a flexión de elementos tubulares de acero inoxidable conformados en frío (SHS y RHS) para el caso de diseño de pórticos cargados en su plano. Se propone un factor de reducción para elementos del tipo viga-columna mn el cual tiene en cuenta los efectos de la nolinealidad del material, las tensiones residuales y la imperfección del elemento. El uso de GNA conjuntamente con tMN permite verificar los diferentes elementos del pórtico solo a resistencia sin tener hacer las comprobaciones correspondientes a pandeo.Postprint (published version

Dietmar Drummer - One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear Material Model for Quasi-Unidirectional Woven Composite Accounting for Viscoelastic, Viscous Deformation, and Stiffness Reduction.
    Polymers, 2018
    Co-Authors: Zhanyu Zhai, Bingyan Jiang, Dietmar Drummer
    Abstract:

    To clarify the individual contribution of viscoelastic and viscous deformation to the global nonlinear response of composites, multilevel cyclic loading-unloading recovery tensile tests were carried out. The experimental results show that there is a linear relationship between the viscous strain and viscoelastic strain of composites, regardless of the off-axis angle or loading stress level. On the basis of experimental results, a coupled damage-plasticity constitutive model was proposed. In this model, the plasticity theory was adopted to assess the evolution of viscous strains. The viscoelastic strain was represented as a linear function of viscous strains. Moreover, the Weibull function of the effective stress was introduced to evaluate the damage variables in terms of Stiffness Reduction. The tensile stress-strain curves, predicted by the proposed model, showed a good agreement with experimental results.