Dépouillements

Strain transfer coefficient analyses for embedded fiber bragg grating sensors in different host materials / Li, Hong-Nan in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1343-1353 Titre : Strain transfer coefficient analyses for embedded fiber bragg grating sensors in different host materials Type de document : texte imprimé Auteurs : Li, Hong-Nan, Auteur ; Zhou, Guang-Dong, Auteur ; Ren, Liang, Auteur Article en page(s) : pp. 1343-1353 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Strain  distribution  Probe  instruments  Experimentation  Young's  modulus  Parameters. Résumé : Fiber Bragg grating (FBG) sensors have attracted a considerable amount of interest for their superior characteristics. However, the FBG sensors made on bare fibers are easily damaged. For their safe use in engineering, the glass core of optical fibers is coated with softer low modulus protective coatings. A portion of the host material strain is absorbed by the protective coatings when the strain transfers from the host material to the fiber core, and hence only a segment of structural strain is sensed. By introducing the shear modulus of the host material, a novel analytical model is developed for evaluating the sensing strain of the embedded FBG sensors in composite structures based on the strain in a host material. The average strain transfer ratio is deduced to describe the percentage transferred to the optical fiber core from the host material. It is concluded that the shear modulus of the host material influences strain transmission, especially when it is much lower than the modulus of the fiber core. Then, the strain transfer ratio of an optical fiber sensor embedded in a multilayered structure is developed in a similar way. The factors that affect the efficiency of strain transfer on the optical fiber sensor are deduced and discussed in detail based on the theoretical analysis. Finally, the theoretical results are verified through laboratory experimentation with the FBG sensors. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Strain transfer coefficient analyses for embedded fiber bragg grating sensors in different host materials [texte imprimé] / Li, Hong-Nan, Auteur ; Zhou, Guang-Dong, Auteur ; Ren, Liang, Auteur . - pp. 1343-1353. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1343-1353 Mots-clés : Strain  distribution  Probe  instruments  Experimentation  Young's  modulus  Parameters. Résumé : Fiber Bragg grating (FBG) sensors have attracted a considerable amount of interest for their superior characteristics. However, the FBG sensors made on bare fibers are easily damaged. For their safe use in engineering, the glass core of optical fibers is coated with softer low modulus protective coatings. A portion of the host material strain is absorbed by the protective coatings when the strain transfers from the host material to the fiber core, and hence only a segment of structural strain is sensed. By introducing the shear modulus of the host material, a novel analytical model is developed for evaluating the sensing strain of the embedded FBG sensors in composite structures based on the strain in a host material. The average strain transfer ratio is deduced to describe the percentage transferred to the optical fiber core from the host material. It is concluded that the shear modulus of the host material influences strain transmission, especially when it is much lower than the modulus of the fiber core. Then, the strain transfer ratio of an optical fiber sensor embedded in a multilayered structure is developed in a similar way. The factors that affect the efficiency of strain transfer on the optical fiber sensor are deduced and discussed in detail based on the theoretical analysis. Finally, the theoretical results are verified through laboratory experimentation with the FBG sensors. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Composite bars of arbitrary cross section in nonlinear elastic nonuniform torsion by BEM / Sapountzakis, E. J. in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1354-1367 Titre : Composite bars of arbitrary cross section in nonlinear elastic nonuniform torsion by BEM Type de document : texte imprimé Auteurs : Sapountzakis, E. J., Auteur ; Tsipiras, V. J., Auteur Article en page(s) : pp. 1354-1367 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Bars  Torsion  Geometry  Shear  stress  Warpage  Boundaries  Cross  sections. Résumé : In this paper the elastic nonuniform torsion analysis of composite cylindrical bars of arbitrary cross section consisting of materials in contact, each of which can surround a finite number of inclusions, taking into account the effect of geometric nonlinearity is presented employing the boundary element method (BEM). All of the cross section's materials are perfectly bonded together, that is separation is not allowed. The torque-rotation relationship is computed based on the finite displacement (finite rotation) theory, that is the transverse displacement components are expressed so as to be valid for large rotations and the longitudinal normal strain includes the second-order geometric nonlinear term often described as the “Wagner strain.” The proposed formulation does not stand on the assumption of a thin-walled structure and therefore the cross section's torsional rigidity is evaluated exactly without using the so-called Saint-Venant's torsional constant. The torsional rigidity of the cross section is evaluated directly employing the primary warping function of the cross section depending on its shape. Three boundary value problems with respect to the variable along the beam axis angle of twist, to the primary and to the secondary warping functions are formulated. The first one, employing the Analog Equation Method (a BEM based method), yields a system of nonlinear equations from which the angle of twist is computed by an iterative process. The rest two problems are solved employing a pure BE method. Numerical results are presented to illustrate the method and demonstrate its efficiency and accuracy. The developed procedure retains most of the advantages of a BEM solution over a pure domain discretization method, although it requires domain discretization. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Composite bars of arbitrary cross section in nonlinear elastic nonuniform torsion by BEM [texte imprimé] / Sapountzakis, E. J., Auteur ; Tsipiras, V. J., Auteur . - pp. 1354-1367. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1354-1367 Mots-clés : Bars  Torsion  Geometry  Shear  stress  Warpage  Boundaries  Cross  sections. Résumé : In this paper the elastic nonuniform torsion analysis of composite cylindrical bars of arbitrary cross section consisting of materials in contact, each of which can surround a finite number of inclusions, taking into account the effect of geometric nonlinearity is presented employing the boundary element method (BEM). All of the cross section's materials are perfectly bonded together, that is separation is not allowed. The torque-rotation relationship is computed based on the finite displacement (finite rotation) theory, that is the transverse displacement components are expressed so as to be valid for large rotations and the longitudinal normal strain includes the second-order geometric nonlinear term often described as the “Wagner strain.” The proposed formulation does not stand on the assumption of a thin-walled structure and therefore the cross section's torsional rigidity is evaluated exactly without using the so-called Saint-Venant's torsional constant. The torsional rigidity of the cross section is evaluated directly employing the primary warping function of the cross section depending on its shape. Three boundary value problems with respect to the variable along the beam axis angle of twist, to the primary and to the secondary warping functions are formulated. The first one, employing the Analog Equation Method (a BEM based method), yields a system of nonlinear equations from which the angle of twist is computed by an iterative process. The rest two problems are solved employing a pure BE method. Numerical results are presented to illustrate the method and demonstrate its efficiency and accuracy. The developed procedure retains most of the advantages of a BEM solution over a pure domain discretization method, although it requires domain discretization. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Tensegrity structures with buckling members explain nonlinear stiffening and reversible softening of actin networks / Xu, Xian in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1368-1374 Titre : Tensegrity structures with buckling members explain nonlinear stiffening and reversible softening of actin networks Type de document : texte imprimé Auteurs : Xu, Xian, Auteur ; Luo, Yaozhi, Auteur Article en page(s) : pp. 1368-1374 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Buckling  Postbuckling  stiffening  Softening  Stress  Structural  members Résumé : In this paper, a three-member tensegrity structure is used as a conceptual model for the dendritic actin network in living cells. The pre and postbuckling behavior of the tensegrity is analyzed basing on the energy method. Analytical simulations are carried out on the tensegrity by using the experimentally obtained scales and mechanic properties of actin-filaments for the structural members of the tensegrity. The model exhibits a stress stiffening regime followed by a stress softening regime in the load-stiffness relationship, which qualitatively tallies with the experimentally observed response of actin networks. Due to the simplicity of the model, there is only a single compressed member and the structure buckles abruptly, which results a softening regime much steeper than that observed in the actin network. To take the member length variety into account, we propose a conceptual large-scale tensegrity system with various member lengths, and its behavior is approximately estimated by the mean response of a large number of three-member tensegrity cells with their member length varying in the range of filament lengths. The obtained mean response exhibits a much better fitness to the response of actin networks than those exhibited by the single tensegrity model. The findings reported in this paper indicate that the dendritic actin network may work as a complex tensegrity system, when it is subjected to a stress. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Tensegrity structures with buckling members explain nonlinear stiffening and reversible softening of actin networks [texte imprimé] / Xu, Xian, Auteur ; Luo, Yaozhi, Auteur . - pp. 1368-1374. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1368-1374 Mots-clés : Buckling  Postbuckling  stiffening  Softening  Stress  Structural  members Résumé : In this paper, a three-member tensegrity structure is used as a conceptual model for the dendritic actin network in living cells. The pre and postbuckling behavior of the tensegrity is analyzed basing on the energy method. Analytical simulations are carried out on the tensegrity by using the experimentally obtained scales and mechanic properties of actin-filaments for the structural members of the tensegrity. The model exhibits a stress stiffening regime followed by a stress softening regime in the load-stiffness relationship, which qualitatively tallies with the experimentally observed response of actin networks. Due to the simplicity of the model, there is only a single compressed member and the structure buckles abruptly, which results a softening regime much steeper than that observed in the actin network. To take the member length variety into account, we propose a conceptual large-scale tensegrity system with various member lengths, and its behavior is approximately estimated by the mean response of a large number of three-member tensegrity cells with their member length varying in the range of filament lengths. The obtained mean response exhibits a much better fitness to the response of actin networks than those exhibited by the single tensegrity model. The findings reported in this paper indicate that the dendritic actin network may work as a complex tensegrity system, when it is subjected to a stress. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Modeling the cooling of concrete by piped water / Myers, T. G. in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1375-1383 Titre : Modeling the cooling of concrete by piped water Type de document : texte imprimé Auteurs : Myers, T. G., Auteur ; Fowkes, N. D., Auteur ; Ballim, Y., Auteur Article en page(s) : pp. 1375-1383 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Concrete  Pipe  flow  Thermal  analysis  Mathematical  models  Cooling. Résumé : Piped water is used to remove hydration heat from concrete blocks during construction. In this paper we develop an approximate model for this process. The problem reduces to solving a one-dimensional heat equation in the concrete, coupled with a first order differential equation for the water temperature. Numerical results are presented and the effect of varying model parameters shown. An analytical solution is also provided for a steady-state constant heat generation model. This helps highlight the dependence on certain parameters and can therefore provide an aid in the design of cooling systems. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Modeling the cooling of concrete by piped water [texte imprimé] / Myers, T. G., Auteur ; Fowkes, N. D., Auteur ; Ballim, Y., Auteur . - pp. 1375-1383. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1375-1383 Mots-clés : Concrete  Pipe  flow  Thermal  analysis  Mathematical  models  Cooling. Résumé : Piped water is used to remove hydration heat from concrete blocks during construction. In this paper we develop an approximate model for this process. The problem reduces to solving a one-dimensional heat equation in the concrete, coupled with a first order differential equation for the water temperature. Numerical results are presented and the effect of varying model parameters shown. An analytical solution is also provided for a steady-state constant heat generation model. This helps highlight the dependence on certain parameters and can therefore provide an aid in the design of cooling systems. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Probabilistic capacity models and fragility estimates for reinforced concrete columns incorporating NDT data / Huang, Qindan in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1384-1392 Titre : Probabilistic capacity models and fragility estimates for reinforced concrete columns incorporating NDT data Type de document : texte imprimé Auteurs : Huang, Qindan, Auteur ; Gardoni, Paolo, Auteur ; Hurlebaus, Stefan, Auteur Article en page(s) : pp. 1384-1392 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Bridges  Probability  Nondestructive  tests  Concrete  columns  Reinforced  concrete. Résumé : Knowing the ability of reinforced concrete (RC) bridges to withstand future seismic demands during their life-cycle can help bridge owners make rational decisions regarding optimal allocation of resources for maintenance, repair, and/or rehabilitation of bridge systems. The accuracy of a reliability assessment can be improved by incorporating information about the current aging and deterioration conditions of a bridge. Nondestructive testing (NDT) can be used to evaluate the actual conditions of a bridge, avoiding the use of deterioration models that bring additional uncertainties in the reliability assessment. This paper develops probabilistic deformation and shear capacity models for RC bridge columns that incorporate information obtained from NDT. The proposed models can be used when the flexural stiffness decays nonuniformly over a column height. The flexural stiffness of a column is estimated based on measured acceleration responses using a system identification method and the damage index method. As an application of the proposed models, a case study assesses the fragility (the conditional probability of attaining or exceeding a specified capacity level) of the column in the Lavic Road Overcrossing for a given deformation or shear demand. This two-span concrete box-girder bridge located in Southern California was subject to the Hector Mine Earthquake in 1999. Pre- and postearthquake estimates of the univariate shear and deformation fragilities and of the bivariate shear-deformation fragility are computed and compared. Both displacement and shear capacities are found to decrease after the earthquake event. Additionally, the results show that the damage due to the Hector Mine Earthquake has a larger impact on the shear capacity than the deformation capacity, leading to a more significant increment in the shear fragility than in the deformation fragility. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Probabilistic capacity models and fragility estimates for reinforced concrete columns incorporating NDT data [texte imprimé] / Huang, Qindan, Auteur ; Gardoni, Paolo, Auteur ; Hurlebaus, Stefan, Auteur . - pp. 1384-1392. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1384-1392 Mots-clés : Bridges  Probability  Nondestructive  tests  Concrete  columns  Reinforced  concrete. Résumé : Knowing the ability of reinforced concrete (RC) bridges to withstand future seismic demands during their life-cycle can help bridge owners make rational decisions regarding optimal allocation of resources for maintenance, repair, and/or rehabilitation of bridge systems. The accuracy of a reliability assessment can be improved by incorporating information about the current aging and deterioration conditions of a bridge. Nondestructive testing (NDT) can be used to evaluate the actual conditions of a bridge, avoiding the use of deterioration models that bring additional uncertainties in the reliability assessment. This paper develops probabilistic deformation and shear capacity models for RC bridge columns that incorporate information obtained from NDT. The proposed models can be used when the flexural stiffness decays nonuniformly over a column height. The flexural stiffness of a column is estimated based on measured acceleration responses using a system identification method and the damage index method. As an application of the proposed models, a case study assesses the fragility (the conditional probability of attaining or exceeding a specified capacity level) of the column in the Lavic Road Overcrossing for a given deformation or shear demand. This two-span concrete box-girder bridge located in Southern California was subject to the Hector Mine Earthquake in 1999. Pre- and postearthquake estimates of the univariate shear and deformation fragilities and of the bivariate shear-deformation fragility are computed and compared. Both displacement and shear capacities are found to decrease after the earthquake event. Additionally, the results show that the damage due to the Hector Mine Earthquake has a larger impact on the shear capacity than the deformation capacity, leading to a more significant increment in the shear fragility than in the deformation fragility. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Performance dependent failure criterion for normal- and high-strength concretes / Folino, Paula in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1393-1409 Titre : Performance dependent failure criterion for normal- and high-strength concretes Type de document : texte imprimé Auteurs : Folino, Paula, Auteur ; Etse, Guillermo, Auteur ; Will, Adrián, Auteur Article en page(s) : pp. 1393-1409 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Concrete  High-strength  concrete  Failure  modes  Parameters. Résumé : A new approach to describe the maximum strength criterion of concretes with different strength capacities is formulated. The proposed failure criterion incorporates the so-called “performance parameter” (betaP) that controls the dependence of the maximum strength on the concrete quality. To assure the feasibility of the solution procedure for any possible set of known data, different methods are proposed to determine betaP according to the available material data. The performance dependent strength criterion presented in this work is expressed in terms of the Haigh Westergaard stress coordinates and as a function of four material parameters that fully define the compressive and tensile meridians of the failure criterion. The variation of the shear strength between these two meridians follows an earlier elliptic interpolation. The proposal includes approximating functions that define the dependence of the above mentioned four material parameters on the two fundamental mechanical properties of concrete: the uniaxial compressive strength fc[prime] and the performance parameter betaP. The capability of the proposed criterion to predict peak stresses of both normal- and high-strength concretes is verified with experimental data available in the literature corresponding to uniaxial, biaxial, and triaxial compression tests. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Performance dependent failure criterion for normal- and high-strength concretes [texte imprimé] / Folino, Paula, Auteur ; Etse, Guillermo, Auteur ; Will, Adrián, Auteur . - pp. 1393-1409. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1393-1409 Mots-clés : Concrete  High-strength  concrete  Failure  modes  Parameters. Résumé : A new approach to describe the maximum strength criterion of concretes with different strength capacities is formulated. The proposed failure criterion incorporates the so-called “performance parameter” (betaP) that controls the dependence of the maximum strength on the concrete quality. To assure the feasibility of the solution procedure for any possible set of known data, different methods are proposed to determine betaP according to the available material data. The performance dependent strength criterion presented in this work is expressed in terms of the Haigh Westergaard stress coordinates and as a function of four material parameters that fully define the compressive and tensile meridians of the failure criterion. The variation of the shear strength between these two meridians follows an earlier elliptic interpolation. The proposal includes approximating functions that define the dependence of the above mentioned four material parameters on the two fundamental mechanical properties of concrete: the uniaxial compressive strength fc[prime] and the performance parameter betaP. The capability of the proposed criterion to predict peak stresses of both normal- and high-strength concretes is verified with experimental data available in the literature corresponding to uniaxial, biaxial, and triaxial compression tests. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Tensile strength of unsaturated sand / Ning Lu in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1410-1419 Titre : Tensile strength of unsaturated sand Type de document : texte imprimé Auteurs : Ning Lu, Auteur ; Kim, Tae-Hyung, Auteur ; Sture, Stein, Auteur Article en page(s) : pp. 1410-1419 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Tensile  strength  Sand,  soil  type  Unsaturated  soil  Soil  water  Soil  suction  Effective  stress. Résumé : A theory that accurately describes tensile strength of wet sand is presented. A closed form expression for tensile strength unifies tensile strength characteristics in all three water retention regimes: pendular, funicular, and capillary. Tensile strength characteristically increases as soil water content increases in the pendular regime, reaches a peak in the funicular regime, and reduces with a continuing water content increase in the capillary regime. Three parameters are employed in the theory: internal friction angle (at low normal stress) phit, the inverse value of the air-entry pressure alpha, and the pore size spectrum parameter n. The magnitude of peak tensile strength is dominantly controlled by the alpha parameter. The saturation at which peak tensile strength occurs only depends on the pore size spectrum parameter n. The closed form expression accords well with experimental water retention and tensile strength data for different sands. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Tensile strength of unsaturated sand [texte imprimé] / Ning Lu, Auteur ; Kim, Tae-Hyung, Auteur ; Sture, Stein, Auteur . - pp. 1410-1419. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1410-1419 Mots-clés : Tensile  strength  Sand,  soil  type  Unsaturated  soil  Soil  water  Soil  suction  Effective  stress. Résumé : A theory that accurately describes tensile strength of wet sand is presented. A closed form expression for tensile strength unifies tensile strength characteristics in all three water retention regimes: pendular, funicular, and capillary. Tensile strength characteristically increases as soil water content increases in the pendular regime, reaches a peak in the funicular regime, and reduces with a continuing water content increase in the capillary regime. Three parameters are employed in the theory: internal friction angle (at low normal stress) phit, the inverse value of the air-entry pressure alpha, and the pore size spectrum parameter n. The magnitude of peak tensile strength is dominantly controlled by the alpha parameter. The saturation at which peak tensile strength occurs only depends on the pore size spectrum parameter n. The closed form expression accords well with experimental water retention and tensile strength data for different sands. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Complementary energy based formulation for torsional buckling of columns / Erkmen, R. Emre in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1420-1426 Titre : Complementary energy based formulation for torsional buckling of columns Type de document : texte imprimé Auteurs : Erkmen, R. Emre, Auteur ; Magdi Mohareb, Auteur ; Bradford, Mark A., Auteur Article en page(s) : pp. 1420-1426 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Buckling  Torsion  Convergence. Résumé : A unique formulation for the elastic torsional buckling analysis of columns is developed in this paper based on the principle of stationary complementary energy. It is well known that in displacement based numerical formulations, discretization errors lead to stiffer behavior; hence convergence from above. On the other hand, discretization errors in complementary energy based numerical formulations lead to softer behavior in linear elasticity problems, which is a desired feature from the engineering view point. However, complementary energy based formulations can only overpredict the buckling loads for the flexural buckling problems of columns unless the physical conditions are compromised. In this study a formulation based on the principle of stationary complementary energy is considered for the elastic torsional buckling analysis of columns. The complementary energy expression is obtained from the well known total potential energy functional by using Frederichs' transformation. In contrast to flexural buckling analysis of columns, it is shown that when the principle of stationary complementary energy is used, the torsional buckling loads can be underpredicted. A mathematical proof is provided to elucidate this property. The convergence behavior of the approximate solutions is illustrated through numerical examples for several columns with different boundary conditions. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Complementary energy based formulation for torsional buckling of columns [texte imprimé] / Erkmen, R. Emre, Auteur ; Magdi Mohareb, Auteur ; Bradford, Mark A., Auteur . - pp. 1420-1426. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1420-1426 Mots-clés : Buckling  Torsion  Convergence. Résumé : A unique formulation for the elastic torsional buckling analysis of columns is developed in this paper based on the principle of stationary complementary energy. It is well known that in displacement based numerical formulations, discretization errors lead to stiffer behavior; hence convergence from above. On the other hand, discretization errors in complementary energy based numerical formulations lead to softer behavior in linear elasticity problems, which is a desired feature from the engineering view point. However, complementary energy based formulations can only overpredict the buckling loads for the flexural buckling problems of columns unless the physical conditions are compromised. In this study a formulation based on the principle of stationary complementary energy is considered for the elastic torsional buckling analysis of columns. The complementary energy expression is obtained from the well known total potential energy functional by using Frederichs' transformation. In contrast to flexural buckling analysis of columns, it is shown that when the principle of stationary complementary energy is used, the torsional buckling loads can be underpredicted. A mathematical proof is provided to elucidate this property. The convergence behavior of the approximate solutions is illustrated through numerical examples for several columns with different boundary conditions. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Handling of constraints in finite-element response sensitivity analysis / Quan Gu in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1427-1438 Titre : Handling of constraints in finite-element response sensitivity analysis Type de document : texte imprimé Auteurs : Quan Gu, Auteur ; Michele Barbato, Auteur ; Conte, Joel P., Auteur Article en page(s) : pp. 1427-1438 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Finite  element  method  Constitutive  models  Constraints  Sensitivity  analysis  Soil-structure  interactions Résumé : In this paper, the direct differentiation method (DDM) for finite-element (FE) response sensitivity analysis is extended to linear and nonlinear FE models with multi-point constraints (MPCs). The analytical developments are provided for three different constraint handling methods, namely: (1) the transformation equation method; (2) the Lagrange multiplier method; and (3) the penalty function method. Two nonlinear benchmark applications are presented: (1) a two-dimensional soil-foundation-structure interaction system and (2) a three-dimensional, one-bay by one-bay, three-story reinforced concrete building with floor slabs modeled as rigid diaphragms, both subjected to seismic excitation. Time histories of response parameters and their sensitivities to material constitutive parameters are computed and discussed, with emphasis on the relative importance of these parameters in affecting the structural response. The DDM-based response sensitivity results are compared with corresponding forward finite difference analysis results, thus validating the formulation presented and its computer implementation. The developments presented in this paper close an important gap between FE response-only analysis and FE response sensitivity analysis through the DDM, extending the latter to applications requiring response sensitivities of FE models with MPCs. These applications include structural optimization, structural reliability analysis, and finite-element model updating. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Handling of constraints in finite-element response sensitivity analysis [texte imprimé] / Quan Gu, Auteur ; Michele Barbato, Auteur ; Conte, Joel P., Auteur . - pp. 1427-1438. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1427-1438 Mots-clés : Finite  element  method  Constitutive  models  Constraints  Sensitivity  analysis  Soil-structure  interactions Résumé : In this paper, the direct differentiation method (DDM) for finite-element (FE) response sensitivity analysis is extended to linear and nonlinear FE models with multi-point constraints (MPCs). The analytical developments are provided for three different constraint handling methods, namely: (1) the transformation equation method; (2) the Lagrange multiplier method; and (3) the penalty function method. Two nonlinear benchmark applications are presented: (1) a two-dimensional soil-foundation-structure interaction system and (2) a three-dimensional, one-bay by one-bay, three-story reinforced concrete building with floor slabs modeled as rigid diaphragms, both subjected to seismic excitation. Time histories of response parameters and their sensitivities to material constitutive parameters are computed and discussed, with emphasis on the relative importance of these parameters in affecting the structural response. The DDM-based response sensitivity results are compared with corresponding forward finite difference analysis results, thus validating the formulation presented and its computer implementation. The developments presented in this paper close an important gap between FE response-only analysis and FE response sensitivity analysis through the DDM, extending the latter to applications requiring response sensitivities of FE models with MPCs. These applications include structural optimization, structural reliability analysis, and finite-element model updating. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Extended polynomial dimensional decomposition for arbitrary probability distributions / Rahman, Sharif in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1439-1451 Titre : Extended polynomial dimensional decomposition for arbitrary probability distributions Type de document : texte imprimé Auteurs : Rahman, Sharif, Auteur Article en page(s) : pp. 1439-1451 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Uncertainty  principles  Stochastic  processes  Reliability  Polynomials. Résumé : This paper presents an extended polynomial dimensional decomposition method for solving stochastic problems subject to independent random input following an arbitrary probability distribution. The method involves Fourier-polynomial expansions of component functions by orthogonal polynomial bases, the Stieltjes procedure for generating the recursion coefficients of orthogonal polynomials and the Gauss quadrature rule for a specified probability measure, and dimension-reduction integration for calculating the expansion coefficients. The extension, which subsumes nonclassical orthogonal polynomials bases, generates a convergent sequence of lower-variate estimates of the probabilistic characteristics of a stochastic response. Numerical results indicate that the extended decomposition method provides accurate, convergent, and computationally efficient estimates of the tail probability of random mathematical functions or reliability of mechanical systems. The convergence of the extended method accelerates significantly when employing measure-consistent orthogonal polynomials. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Extended polynomial dimensional decomposition for arbitrary probability distributions [texte imprimé] / Rahman, Sharif, Auteur . - pp. 1439-1451. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1439-1451 Mots-clés : Uncertainty  principles  Stochastic  processes  Reliability  Polynomials. Résumé : This paper presents an extended polynomial dimensional decomposition method for solving stochastic problems subject to independent random input following an arbitrary probability distribution. The method involves Fourier-polynomial expansions of component functions by orthogonal polynomial bases, the Stieltjes procedure for generating the recursion coefficients of orthogonal polynomials and the Gauss quadrature rule for a specified probability measure, and dimension-reduction integration for calculating the expansion coefficients. The extension, which subsumes nonclassical orthogonal polynomials bases, generates a convergent sequence of lower-variate estimates of the probabilistic characteristics of a stochastic response. Numerical results indicate that the extended decomposition method provides accurate, convergent, and computationally efficient estimates of the tail probability of random mathematical functions or reliability of mechanical systems. The convergence of the extended method accelerates significantly when employing measure-consistent orthogonal polynomials. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Characteristics of shear layer structure in skimming flow over a vertical drop pool / Wei-Jung Lin in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1452-1466 Titre : Characteristics of shear layer structure in skimming flow over a vertical drop pool Type de document : texte imprimé Auteurs : Wei-Jung Lin, Auteur ; Chang Lin, Auteur ; Shih-Chun Hsieh, Auteur Article en page(s) : pp. 1452-1466 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Drop  structures  Flow  measurement  Layered  systems  Velocity Résumé : The characteristics of shear layer structure between the sliding jet and the pool for skimming flows over a vertical drop pool were investigated experimentally, using flow visualization technique and high speed particle image velocimetry. Four series of experiments having different end sill ratios (h/H=0.12, 0.43, 0.71 and 1.0, where h=end sill height and H=drop height) with various approaching flow discharges were performed to measure the detailed quantitative velocity fields of the shear layer. The mean velocities and turbulence properties were obtained by ensemble averaging the repeated measurements. From the velocity profiles, it is found that the growth of the shear layer in the downward direction as the jet slides down the pool represents the momentum exchange. Analyzing the distribution of measured velocity, the similarity profile of the mean velocity at different cross sections along the shear layer was obtained. The proposed characteristic scales provided unique similarity profiles having promising regression coefficient. The selection of these characteristic scales is also discussed. Further, the spatial variations of mean velocity profiles, turbulence intensities, in-plane turbulent kinetic energy, and Reynolds shear stress were also elucidated in detail. The imperative observation is that the Reynolds shear stress dominates the major part along the shear layer as compared to the viscous shear stress. The study also provides an insight into the flow phenomena through the velocity and turbulent characteristics. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Characteristics of shear layer structure in skimming flow over a vertical drop pool [texte imprimé] / Wei-Jung Lin, Auteur ; Chang Lin, Auteur ; Shih-Chun Hsieh, Auteur . - pp. 1452-1466. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1452-1466 Mots-clés : Drop  structures  Flow  measurement  Layered  systems  Velocity Résumé : The characteristics of shear layer structure between the sliding jet and the pool for skimming flows over a vertical drop pool were investigated experimentally, using flow visualization technique and high speed particle image velocimetry. Four series of experiments having different end sill ratios (h/H=0.12, 0.43, 0.71 and 1.0, where h=end sill height and H=drop height) with various approaching flow discharges were performed to measure the detailed quantitative velocity fields of the shear layer. The mean velocities and turbulence properties were obtained by ensemble averaging the repeated measurements. From the velocity profiles, it is found that the growth of the shear layer in the downward direction as the jet slides down the pool represents the momentum exchange. Analyzing the distribution of measured velocity, the similarity profile of the mean velocity at different cross sections along the shear layer was obtained. The proposed characteristic scales provided unique similarity profiles having promising regression coefficient. The selection of these characteristic scales is also discussed. Further, the spatial variations of mean velocity profiles, turbulence intensities, in-plane turbulent kinetic energy, and Reynolds shear stress were also elucidated in detail. The imperative observation is that the Reynolds shear stress dominates the major part along the shear layer as compared to the viscous shear stress. The study also provides an insight into the flow phenomena through the velocity and turbulent characteristics. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Plastic zone around circular holes / Leitman, M. J. in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1467-1471 Titre : Plastic zone around circular holes Type de document : texte imprimé Auteurs : Leitman, M. J., Auteur ; Villaggio, P., Auteur Année de publication : 2010 Article en page(s) : pp. 1467-1471 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Plastics  Holes  Elastoplasticity Résumé : In 1946, L. A. Galin proposed an ingenious solution to the problem of analytically determining the plastic region completely surrounding a circular hole in a thin initially elastic plate subject to tensile stress at infinity. The results of Galin's analysis are recovered by a simple collocation, provided an elliptical elastic-plastic boundary is assumed. This elementary procedure is then applied to treat the case, unresolvable by Galin's method, in which the plastic domain does not completely surround the hole. DEWEY : 620.1 ISSN : 07339399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Plastic zone around circular holes [texte imprimé] / Leitman, M. J., Auteur ; Villaggio, P., Auteur . - 2010 . - pp. 1467-1471. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1467-1471 Mots-clés : Plastics  Holes  Elastoplasticity Résumé : In 1946, L. A. Galin proposed an ingenious solution to the problem of analytically determining the plastic region completely surrounding a circular hole in a thin initially elastic plate subject to tensile stress at infinity. The results of Galin's analysis are recovered by a simple collocation, provided an elliptical elastic-plastic boundary is assumed. This elementary procedure is then applied to treat the case, unresolvable by Galin's method, in which the plastic domain does not completely surround the hole. DEWEY : 620.1 ISSN : 07339399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Optimization and multihazard structural design / Potra, Florian A. in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1472-1475 Titre : Optimization and multihazard structural design Type de document : texte imprimé Auteurs : Potra, Florian A., Auteur ; Simiu, Emil, Auteur Année de publication : 2010 Article en page(s) : pp. 1472-1475 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Earthquake  engineering  Hazards  Optimization  Solar  power  Structural  engineering  Seismic  design  Wind  loads Résumé : There is a growing interest in the development of procedures for the design of structures exposed to multiple hazards. The goal is to achieve safer and/or more economical designs than would be the case if the structures were analyzed independently for each hazard and an envelope of the demands induced by each of the hazards were used for member sizing. We describe an optimization approach to multihazard design that achieves the greatest possible economy while satisfying specified safety-related and other constraints. We then present an application to illustrate our approach. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Optimization and multihazard structural design [texte imprimé] / Potra, Florian A., Auteur ; Simiu, Emil, Auteur . - 2010 . - pp. 1472-1475. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 12 (Décembre 2009) . - pp. 1472-1475 Mots-clés : Earthquake  engineering  Hazards  Optimization  Solar  power  Structural  engineering  Seismic  design  Wind  loads Résumé : There is a growing interest in the development of procedures for the design of structures exposed to multiple hazards. The goal is to achieve safer and/or more economical designs than would be the case if the structures were analyzed independently for each hazard and an envelope of the demands induced by each of the hazards were used for member sizing. We describe an optimization approach to multihazard design that achieves the greatest possible economy while satisfying specified safety-related and other constraints. We then present an application to illustrate our approach. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

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