The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
János Lógó - One of the best experts on this subject based on the ideXlab platform.
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Reliability based design of frames with limited residual Strain Energy capacity
Periodica Polytechnica Civil Engineering, 2011Co-Authors: János Lógó, Majid Movahedi Rad, Jarosław Knabel, Piotr TauzowskiAbstract:The aim of this paper is to create new type of plastic limit design procedures where the influence of the limited load carrying capacity of the beam-to-column connections of elasto-plastic steel (or composite) frames under multi-parameter static loading and probabilistically given conditions are taken into consideration. In addition to the plastic limit design to control the plastic behaviour of the structure, bound on the Complementary Strain Energy of the residual forces is also applied. If the design uncertainties (manufacturing, strength, geometrical) are taken into consideration at the computation of the Complementary Strain Energy of the residual forces the reliability based extended plastic limit design problems can be formed. Two numerical procedures are elaborated. The formulations of the problems yield to nonlinear mathematical programming which are solved by the use of sequential quadratic algorithm.
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PLASTIC BEHAVIOUR AND STABILITY CONStrainTS IN THE RELIABILITY BASED SHAKEDOWN ANALYSIS AND OPTIMAL DESIGN OF SKELETAL STRUCTURES
2011Co-Authors: M Movahedi Rad, János LógóAbstract:This paper includes description of reliability based design optimization of elasto-plastic skeletal structures under multi-parameter static loading. Presented approach is based on the assumption that the Complementary Strain Energy of the residual forces is considered as an overall measure of the plastic performance for plastic shakedown analysis and optimal design of the structure, and this measure is an uncertain quantity responsible for resistance of the structure by assuming Gaussian distribution. The problems yield to nonlinear mathematical programming which are solved by the use of bi-level sequential quadratic algorithm. Simple portal frames are optimized to illustrate the proposed approaches.
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Reliability based limit design of steel frames with limited residual Strain Energy capacity
PAMM, 2009Co-Authors: Majid Movahedi Rad, János Lógó, Jarosław Knabel, Piotr TauzowskiAbstract:The aim of this paper is to take into consideration the influence of the limited load carrying capacity of the connections on the plastic limit state of elasto-plastic steel (or composite) framed structures under multi-parameter stochastic loading and probabilistically given conditions. In addition to the plastic limit design to control the plastic behaviour of the structure, bound on the Complementary Strain Energy of the residual forces is also applied. This bound has significant effect for the load parameter. If the design uncertainties (manufacturing, strength, geometrical) are expressed by the calculation of the Complementary Strain Energy of the residual forces a reliability based extended limit design problem is formed. The formulations of the problems yield to nonlinear mathematical programming which are solved by the use of sequential quadratic algorithm. The bi-level optimization procedure governed by the reliability index calculation. c � 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Plastic Limit and Shakedown Analysis of Elasto-plastic Steel Frames with Semirigid Connections
Design Fabrication and Economy of Welded Structures, 2008Co-Authors: János Lógó, S. Kaliszky, Mohammed Hjiaj, Majid Movahredi RadAbstract:The aim of this paper is to study the influence of the semi-rigid connections on the plastic behaviour of elasto-plastic steel frames subjected to dead load and quasi-static working loads. In the presented methods the static theorem of plastic limit analysis and the static theorem of shakedown analysis are applied and to control the plastic deformation bound on the Complementary Strain Energy of residual forces is also used. The semi-rigid connections are represented by different elasto-plastic models (rigid, strong, medium, soft and pinned) which are incorporated in the elementary stiffness matrix of the beam elements. The presented methods are suitable for the construction of plastic limit and shakedown curves, respectively, which provide the plastic limit load and shakedown multipliers for different ratios of working loads and bound the safe domains against collapse and unrestricted plastic deformations, respectively. The numerical calculations show that the semi-rigid connection can influence significantly the plastic behaviour of steel structures.
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The influence of semi‐rigid connections on the shakedown of elasto‐plastic frames
PAMM, 2007Co-Authors: S. Kaliszky, János LógóAbstract:The main structural elements of steel framed multi-storey structures are the columns, the beams and their connections. The assumption has been widely applied in the past that the connections are either rigid or pinned. The actual behaviour of the connections is however somewhere between these limits, they are semi-rigid. The aim of this paper is to analyze the effect of the semi-rigid connections on the shakedown of steel structures under multi-parameter static loading. In the analysis, to control the plastic behavior of the structure, bound on the Complementary Strain Energy of the residual forces is applied. The formulation of the problem yields to nonlinear mathematical programming. The results of the numerical calculation show that the semi-rigid connections can influence significantly the magnitude of the shakedown parameter. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Kyle W. Strabala - One of the best experts on this subject based on the ideXlab platform.
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Free-edge stresses and progressive cracking in surface coatings of circular torsion bars
International Journal of Solids and Structures, 2008Co-Authors: Yuris A. Dzenis, Kyle W. StrabalaAbstract:This paper considers the explicit solutions of free-edge stresses near circumferential cracks in surface coatings of circular torsion bars and their application in determining the progressive cracking density in the coating layers. The problem was formulated within the framework of linear elastic fracture mechanics (LEFM). The free-edge stresses near crack tip and the shear stresses in the cross-section of the torsion bar were approached in explicit forms based on the variational principle of Complementary Strain Energy. Criterion for progressive cracking in the coating layer was established in sense of Strain Energy conservation, and the crack density is thereby estimated. Effects of external torque, aspect ratio, and elastic properties on the density of progressive cracking were examined numerically. The present study shows that, in the sense of inducing a given crack density, compliant coating layer with lower modulus has much higher critical torque than that of a stiffer one with the same geometries and substrate material, i.e., compliant coating layer has greater cracking tolerance. Meanwhile, the study also indicates that thicker surface coating layer is more pliant to cracking than the thinner ones. The present model can be used for analyzing the damage mechanism and cracking tolerance of surface coatings of torsion shafts and for data reduction of torsional fracture test of brittle surface coatings, etc. @2007 Elsevier Ltd. All rights reserved
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Free-edge stresses and progressive cracking in surface coatings of circular torsion bars
International Journal of Solids and Structures, 2007Co-Authors: Yuris A. Dzenis, Kyle W. StrabalaAbstract:This paper considers the explicit solutions of free-edge stresses near circumferential cracks in surface coatings of circular torsion bars and their application in determining the progressive cracking density in the coating layers. The problem was formulated within the framework of linear elastic fracture mechanics (LEFM). The free-edge stresses near crack tip and the shear stresses in the cross-section of the torsion bar were approached in explicit forms based on the variational principle of Complementary Strain Energy. Criterion for progressive cracking in the coating layer was established in sense of Strain Energy conservation, and the crack density is thereby estimated. Effects of external torque, aspect ratio, and elastic properties on the density of progressive cracking were examined numerically. The present study shows that, in the sense of inducing a given crack density, compliant coating layer with lower modulus has much higher critical torque than that of a stiffer one with the same geometries and substrate material, i.e., compliant coating layer has greater cracking tolerance. Meanwhile, the study also indicates that thicker surface coating layer is more pliant to cracking than the thinner ones. The present model can be used for analyzing the damage mechanism and cracking tolerance of surface coatings of torsion shafts and for data reduction of torsional fracture test of brittle surface coatings, etc.
S. Kaliszky - One of the best experts on this subject based on the ideXlab platform.
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Plastic Limit and Shakedown Analysis of Elasto-plastic Steel Frames with Semirigid Connections
Design Fabrication and Economy of Welded Structures, 2008Co-Authors: János Lógó, S. Kaliszky, Mohammed Hjiaj, Majid Movahredi RadAbstract:The aim of this paper is to study the influence of the semi-rigid connections on the plastic behaviour of elasto-plastic steel frames subjected to dead load and quasi-static working loads. In the presented methods the static theorem of plastic limit analysis and the static theorem of shakedown analysis are applied and to control the plastic deformation bound on the Complementary Strain Energy of residual forces is also used. The semi-rigid connections are represented by different elasto-plastic models (rigid, strong, medium, soft and pinned) which are incorporated in the elementary stiffness matrix of the beam elements. The presented methods are suitable for the construction of plastic limit and shakedown curves, respectively, which provide the plastic limit load and shakedown multipliers for different ratios of working loads and bound the safe domains against collapse and unrestricted plastic deformations, respectively. The numerical calculations show that the semi-rigid connection can influence significantly the plastic behaviour of steel structures.
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The influence of semi‐rigid connections on the shakedown of elasto‐plastic frames
PAMM, 2007Co-Authors: S. Kaliszky, János LógóAbstract:The main structural elements of steel framed multi-storey structures are the columns, the beams and their connections. The assumption has been widely applied in the past that the connections are either rigid or pinned. The actual behaviour of the connections is however somewhere between these limits, they are semi-rigid. The aim of this paper is to analyze the effect of the semi-rigid connections on the shakedown of steel structures under multi-parameter static loading. In the analysis, to control the plastic behavior of the structure, bound on the Complementary Strain Energy of the residual forces is applied. The formulation of the problem yields to nonlinear mathematical programming. The results of the numerical calculation show that the semi-rigid connections can influence significantly the magnitude of the shakedown parameter. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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A PARAMETRIC SURVEY OF THE INFLUENCE OF THE SEMI-RIGID CONNECTIONS ON THE SHAKEDOWN OF ELASTO-PLASTIC FRAMES
Periodica Polytechnica-civil Engineering, 2006Co-Authors: János Lógó, S. Kaliszky, Mohammed HjiajAbstract:In the past it was generally assumed that the connection of the beams and columns of the steel-framed multistorey structures are either rigid or pinned. In the reality, however, they are semi-rigid. This circumstance influences significantly the behaviour of the entire structure, therefore, it has to be taken into consideration in the analysis and design. In this paper a parametric study is presented to analyse the influence of the semi-rigid connections on the shakedown of elasto-plastic steel framed structures under multi-parameter static loading. To control the plastic behaviour of the structure bound on the Complementary Strain Energy of the residual forces is also applied. The semi-rigid behaviour is modelled by appropriate internal springs at the beam column-connections. The formulation of the problem yields to nonlinear mathematical programming which is solved by the use of an iterative procedure. The parametric study is illustrated by the solution of an example.
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plastic behaviour and stability conStraints in the shakedown analysis and optimal design of trusses
Structural and Multidisciplinary Optimization, 2002Co-Authors: S. Kaliszky, János LógóAbstract:A shakedown analysis and optimum shakedown design of elasto-plastic trusses under multi-parameter static loading are presented. To control the plastic behaviour of the truss, bounds on the Complementary Strain Energy of the residual forces and on the residual displacements are applied and for the bars under compression critical stresses updated during the iteration are taken into consideration. The formulation of problems is suitable for nonlinear mathematical programming which is solved by the use of an iterative procedure. The application of the method is illustrated by three test examples.
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LAYOUT AND SHAPE OPTIMIZATION OF ELASTOPLASTIC DISKS WITH BOUNDS ON DEFORMATION AND DISPLACEMENT
Mechanics of Structures and Machines, 2002Co-Authors: S. Kaliszky, János LógóAbstract:ABSTRACT A design method is presented for layout optimization of linearly elastic–perfectly plastic disks subjected to multiparameter loading. The method is based on the static theorem of shakedown analysis and on the concept of porous material, where the material distribution of the discretized structure is described by the densities of the finite elements that are considered design variables. In addition to shakedown, two further compliance conStraints are applied: bounds for the Complementary Strain Energy of the residual stresses, and for the residual displacements. By the proper choice of these bounds the plastic behavior of the disk can be controlled and in special cases the elastic and fully plastic optimal solutions can be determined. The formulation of this problem yields to nonlinear mathematical programing. The application is illustrated by numerical examples. The method can also be applied to trusses, frames, and plates. *Communicated by M. Botkin. †Presented at ICTAM2000, held in Chicago in S...
Yuris A. Dzenis - One of the best experts on this subject based on the ideXlab platform.
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Free-edge stresses and progressive cracking in surface coatings of circular torsion bars
International Journal of Solids and Structures, 2008Co-Authors: Yuris A. Dzenis, Kyle W. StrabalaAbstract:This paper considers the explicit solutions of free-edge stresses near circumferential cracks in surface coatings of circular torsion bars and their application in determining the progressive cracking density in the coating layers. The problem was formulated within the framework of linear elastic fracture mechanics (LEFM). The free-edge stresses near crack tip and the shear stresses in the cross-section of the torsion bar were approached in explicit forms based on the variational principle of Complementary Strain Energy. Criterion for progressive cracking in the coating layer was established in sense of Strain Energy conservation, and the crack density is thereby estimated. Effects of external torque, aspect ratio, and elastic properties on the density of progressive cracking were examined numerically. The present study shows that, in the sense of inducing a given crack density, compliant coating layer with lower modulus has much higher critical torque than that of a stiffer one with the same geometries and substrate material, i.e., compliant coating layer has greater cracking tolerance. Meanwhile, the study also indicates that thicker surface coating layer is more pliant to cracking than the thinner ones. The present model can be used for analyzing the damage mechanism and cracking tolerance of surface coatings of torsion shafts and for data reduction of torsional fracture test of brittle surface coatings, etc. @2007 Elsevier Ltd. All rights reserved
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Free-edge stresses and progressive cracking in surface coatings of circular torsion bars
International Journal of Solids and Structures, 2007Co-Authors: Yuris A. Dzenis, Kyle W. StrabalaAbstract:This paper considers the explicit solutions of free-edge stresses near circumferential cracks in surface coatings of circular torsion bars and their application in determining the progressive cracking density in the coating layers. The problem was formulated within the framework of linear elastic fracture mechanics (LEFM). The free-edge stresses near crack tip and the shear stresses in the cross-section of the torsion bar were approached in explicit forms based on the variational principle of Complementary Strain Energy. Criterion for progressive cracking in the coating layer was established in sense of Strain Energy conservation, and the crack density is thereby estimated. Effects of external torque, aspect ratio, and elastic properties on the density of progressive cracking were examined numerically. The present study shows that, in the sense of inducing a given crack density, compliant coating layer with lower modulus has much higher critical torque than that of a stiffer one with the same geometries and substrate material, i.e., compliant coating layer has greater cracking tolerance. Meanwhile, the study also indicates that thicker surface coating layer is more pliant to cracking than the thinner ones. The present model can be used for analyzing the damage mechanism and cracking tolerance of surface coatings of torsion shafts and for data reduction of torsional fracture test of brittle surface coatings, etc.
D. Kujawski - One of the best experts on this subject based on the ideXlab platform.
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Deviatoric Formulation of the SWT Parameter
2015Co-Authors: D. KujawskiAbstract:The Smith-Watson-Topper (SWT) parameter was originally suggested and is still widely used to account for a mean stress in fatigue life analysis. It is well recognized however, that the SWT parameter might be non-conservative for cyclic loads that involve relatively large compressive mean stresses. A new Energy interpretation of the SWT parameter is proposed. This interpretation is formulated in terms of the sum of Strain Energy density, the Complementary Strain Energy density supplemented by the Strain Energy density associated with a mean stress in the cycle. Then, a new deviatoric formulation of the SWTD parameter is proposed. Capability of the deviatoric SWTD parameter to correlate experimental data for 7075-T651Al and ASTM A723 steel under various positive and negative mean stresses is presented. At high negative mean stresses, the deviatoric SWTD parameter demonstrates a fairly good correlation where the original SWT parameter is unable to correlate the data.
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A deviatoric version of the SWT parameter
International Journal of Fatigue, 2014Co-Authors: D. KujawskiAbstract:Abstract The Smith–Watson–Topper parameter (SWT = σ max e a ) was originally suggested and is still widely used to account for the mean stress effects in fatigue life analysis. It is well recognized however, that the SWT parameter might be a non-conservative description for cyclic loads that involve relatively large compressive mean stresses that can develop in samples/components with notches after overloads. In such situations σ max tends to be small resulting in underestimating the SWT parameter. It is shown that the SWT parameter can be interpreted in terms of the sum of Strain Energy and Complementary Strain Energy densities supplemented by the Strain Energy density associated with a mean stress in the cycle. Using this Energy interpretation and its analogy with the Neuber’s rule a deviatoric version of the SWT parameter called SWT D is proposed. It is found that for positive mean stresses and moderate negative mean stresses the original SWT parameter and the proposed deviatoric SWT D parameter yield similar results. At large compressive mean stresses, the deviatoric SWT D parameter demonstrates a fairly good correlation while the original SWT parameter is unable to correlate the data. Although the proposed approach seems to be very promising, based on the limited data of this study, it should be further re-examined using more experimental data sets, in particular for multiaxial in-phase and out-of-phase loadings.