Dépouillements

Generalized masing approach to modeling hysteretic deteriorating behavior / S. Ali Ashrafi in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.495–505. Titre : Generalized masing approach to modeling hysteretic deteriorating behavior Type de document : texte imprimé Auteurs : S. Ali Ashrafi, Auteur ; Smyth, Andrew W., Auteur Année de publication : 2007 Article en page(s) : pp.495–505. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Hysteresis  Constitutive  models  Deterioration  Identification  Ductility  Nonlinear  response  Loading  history Résumé : The modeling of hysteretic behavior is of significant importance in several areas, including civil engineering and mechanics. This paper focuses on finding a method for modeling hysteretic behavior that is simple and efficient in terms of capturing the response and retaining the memory, if any, and at the same time is proper for use in physically meaningful modeling and identification of the system with few parameters. A distributed-element model (DEM) capable of capturing deterioration is used as a starting point, and its characteristics are studied, with a particular focus on the way memory is stored in the model. It is observed that keeping track of the response at a few of the past extremes of input displacement, called the Sequence of Dominant Alternating Extremes, is enough for representing the effect of history. The relation of this behavior to a generalized Masing model is studied. A set of rules is proposed which is a generalization of the Masing rules and can capture the deteriorating (or nondeteriorating) response of DEMs with any distribution of element yield displacement thresholds to any arbitrary loading. The presented formulation provides a framework for efficient modeling and identification of dynamic models of very different characteristics with only a few physically meaningful parameters. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2849 [...] [article] Generalized masing approach to modeling hysteretic deteriorating behavior [texte imprimé] / S. Ali Ashrafi, Auteur ; Smyth, Andrew W., Auteur . - 2007 . - pp.495–505. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.495–505. Mots-clés : Hysteresis  Constitutive  models  Deterioration  Identification  Ductility  Nonlinear  response  Loading  history Résumé : The modeling of hysteretic behavior is of significant importance in several areas, including civil engineering and mechanics. This paper focuses on finding a method for modeling hysteretic behavior that is simple and efficient in terms of capturing the response and retaining the memory, if any, and at the same time is proper for use in physically meaningful modeling and identification of the system with few parameters. A distributed-element model (DEM) capable of capturing deterioration is used as a starting point, and its characteristics are studied, with a particular focus on the way memory is stored in the model. It is observed that keeping track of the response at a few of the past extremes of input displacement, called the Sequence of Dominant Alternating Extremes, is enough for representing the effect of history. The relation of this behavior to a generalized Masing model is studied. A set of rules is proposed which is a generalization of the Masing rules and can capture the deteriorating (or nondeteriorating) response of DEMs with any distribution of element yield displacement thresholds to any arbitrary loading. The presented formulation provides a framework for efficient modeling and identification of dynamic models of very different characteristics with only a few physically meaningful parameters. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2849 [...]

Nonlinear dynamical model for hysteresis based on nonconvex potential energy / L. X. Wang in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.506–513. Titre : Nonlinear dynamical model for hysteresis based on nonconvex potential energy Type de document : texte imprimé Auteurs : L. X. Wang, Auteur ; M. Willatzen, Auteur Année de publication : 2007 Article en page(s) : pp.506–513. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Hysteresis  Bifurcations  Damping  Dynamics  models  Energy Résumé : A model for hysteretic dynamics is proposed in the current paper. Hysteresis is treated as an input–output relation for a dynamic system. The Lagrangian of the dynamic system is constructed on the basis of a nonconvex potential energy and governing equations of the system dynamics are obtained using the Lagrangian equation. Bifurcations will be induced in the nonlinear dynamics due to the nonconvexity of the potential energy. It is shown that when the coefficients are chosen appropriately, the bifurcation diagram will lead to hysteretic behavior. Both the third- and fifth-order nonlinear terms are investigated and it is shown that the fifth-order nonlinearity is able to give a perfect prediction of experimental hysteretic behaviors. Hysteretic damping force of a magneto-rheological fluid damper and polarization hysteresis in piezoelectric materials are modeled successfully using the current model. The parameter identification for the model is also presented. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2850 [...] [article] Nonlinear dynamical model for hysteresis based on nonconvex potential energy [texte imprimé] / L. X. Wang, Auteur ; M. Willatzen, Auteur . - 2007 . - pp.506–513. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.506–513. Mots-clés : Hysteresis  Bifurcations  Damping  Dynamics  models  Energy Résumé : A model for hysteretic dynamics is proposed in the current paper. Hysteresis is treated as an input–output relation for a dynamic system. The Lagrangian of the dynamic system is constructed on the basis of a nonconvex potential energy and governing equations of the system dynamics are obtained using the Lagrangian equation. Bifurcations will be induced in the nonlinear dynamics due to the nonconvexity of the potential energy. It is shown that when the coefficients are chosen appropriately, the bifurcation diagram will lead to hysteretic behavior. Both the third- and fifth-order nonlinear terms are investigated and it is shown that the fifth-order nonlinearity is able to give a perfect prediction of experimental hysteretic behaviors. Hysteretic damping force of a magneto-rheological fluid damper and polarization hysteresis in piezoelectric materials are modeled successfully using the current model. The parameter identification for the model is also presented. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2850 [...]

Dynamic fracture simulation of concrete using a virtual internal bond model / Ganesh Thiagarajan in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.514–522. Titre : Dynamic fracture simulation of concrete using a virtual internal bond model Type de document : texte imprimé Auteurs : Ganesh Thiagarajan, Auteur Année de publication : 2007 Article en page(s) : pp.514–522. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Fracture  Cracking  Finite  elements  Simulation Résumé : A multiscale virtual internal bond (VIB) model for isotropic materials has been recently proposed to describe material deformation and fracture under quasi-static and dynamic loading situations. Fracture simulation using an isotropic VIB model is made possible by incorporating a cohesive type law, inspired by atomistic-level interaction among particles into a hyperelastic framework at the continuum level. Thus, fracture is built directly into the constitutive formulation. The numerical implementation of the material model for brittle materials into a finite-element scheme and the determination of model parameters has been previously researched. In this paper, the VIB model is applied to the dynamic fracture simulation of plain concrete. The experimental study on the dynamic tensile failure of concrete by Gran et al. is used to determine the VIB model material parameters for plain concrete. Simulations and results of comparisons with the concrete–VIB model with the experimental results are presented in this paper. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2851 [...] [article] Dynamic fracture simulation of concrete using a virtual internal bond model [texte imprimé] / Ganesh Thiagarajan, Auteur . - 2007 . - pp.514–522. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.514–522. Mots-clés : Fracture  Cracking  Finite  elements  Simulation Résumé : A multiscale virtual internal bond (VIB) model for isotropic materials has been recently proposed to describe material deformation and fracture under quasi-static and dynamic loading situations. Fracture simulation using an isotropic VIB model is made possible by incorporating a cohesive type law, inspired by atomistic-level interaction among particles into a hyperelastic framework at the continuum level. Thus, fracture is built directly into the constitutive formulation. The numerical implementation of the material model for brittle materials into a finite-element scheme and the determination of model parameters has been previously researched. In this paper, the VIB model is applied to the dynamic fracture simulation of plain concrete. The experimental study on the dynamic tensile failure of concrete by Gran et al. is used to determine the VIB model material parameters for plain concrete. Simulations and results of comparisons with the concrete–VIB model with the experimental results are presented in this paper. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2851 [...]

Techniques for numerical simulations of concrete slabs for demolishing by blasting / A. Plotzitza in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.523–533. Titre : Techniques for numerical simulations of concrete slabs for demolishing by blasting Type de document : texte imprimé Auteurs : A. Plotzitza, Auteur ; T. Rabczuk, Auteur ; J. Eibl, Auteur Année de publication : 2007 Article en page(s) : pp.523–533. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Concrete  slabs  Blasting  Strain  rate  Constitutive  equations  Simulation  models  Numerical  analysis  Experimental  data Résumé : The subject of this article is the numerical simulation of concrete under explosive loading using a meshbased and a meshfree discretization technique. The presented techniques are verified by experimental data. Experimental evidence suggests that the complete stress–strain history relation must be considered as a basis for constitutive modeling if concrete is subjected to high loading rates. These dynamic phenomena cause a retardation of damage activation which must be taken into account when constitutive modeling is pursued on mesolevel instead of microlevel. By including a dynamic relaxation formulation within the framework of a general three-dimensional coupled continuum damage-plasticity law, it is shown that the solution of the wave propagation problem in materials with strain-softening becomes independent of mesh size. As the simulation of concrete under contact detonation causes severe numerical problems because of the large deformations, special numerical spatial discretization techniques have to be used. In this article we compare the results of a concrete slab under contact detonation using the finite element method code LS-DYNA with an arbitrary Lagrangian Eulerian coupling and the results obtained by a MLSPH code developed at our institute with experimental data. The same constitutive model for concrete and the same equation of state for the explosive is implemented in the two codes. The results of the different numerical simulations and the experimental data agree with each other well. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2852 [...] [article] Techniques for numerical simulations of concrete slabs for demolishing by blasting [texte imprimé] / A. Plotzitza, Auteur ; T. Rabczuk, Auteur ; J. Eibl, Auteur . - 2007 . - pp.523–533. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.523–533. Mots-clés : Concrete  slabs  Blasting  Strain  rate  Constitutive  equations  Simulation  models  Numerical  analysis  Experimental  data Résumé : The subject of this article is the numerical simulation of concrete under explosive loading using a meshbased and a meshfree discretization technique. The presented techniques are verified by experimental data. Experimental evidence suggests that the complete stress–strain history relation must be considered as a basis for constitutive modeling if concrete is subjected to high loading rates. These dynamic phenomena cause a retardation of damage activation which must be taken into account when constitutive modeling is pursued on mesolevel instead of microlevel. By including a dynamic relaxation formulation within the framework of a general three-dimensional coupled continuum damage-plasticity law, it is shown that the solution of the wave propagation problem in materials with strain-softening becomes independent of mesh size. As the simulation of concrete under contact detonation causes severe numerical problems because of the large deformations, special numerical spatial discretization techniques have to be used. In this article we compare the results of a concrete slab under contact detonation using the finite element method code LS-DYNA with an arbitrary Lagrangian Eulerian coupling and the results obtained by a MLSPH code developed at our institute with experimental data. The same constitutive model for concrete and the same equation of state for the explosive is implemented in the two codes. The results of the different numerical simulations and the experimental data agree with each other well. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2852 [...]

Early-time solution for a radial hydraulic fracture / Andrew P. Bunger in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.534–540. Titre : Early-time solution for a radial hydraulic fracture Type de document : texte imprimé Auteurs : Andrew P. Bunger, Auteur ; Emmanuel Detournay, Auteur Année de publication : 2007 Article en page(s) : pp.534–540. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Elasticity  Fracture  Mechanics  Hydraulics Résumé : The small-time asymptotic solution for a penny-shaped fluid-driven fracture is obtained semianalytically. Scaling considerations indicate that the portion of the fracture that is filled with fluid increases with time according to a power law. The problem is shown to be self-similar at the length scale of the small fluid-filled region and to depend on only the mean fluid pressure at the length scale of the fracture. This similarity solution is unusual as the two length scales of the problem—the radius of the fracture and the radius of the fluid front—evolve according to two different power laws of time. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2853 [...] [article] Early-time solution for a radial hydraulic fracture [texte imprimé] / Andrew P. Bunger, Auteur ; Emmanuel Detournay, Auteur . - 2007 . - pp.534–540. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.534–540. Mots-clés : Elasticity  Fracture  Mechanics  Hydraulics Résumé : The small-time asymptotic solution for a penny-shaped fluid-driven fracture is obtained semianalytically. Scaling considerations indicate that the portion of the fracture that is filled with fluid increases with time according to a power law. The problem is shown to be self-similar at the length scale of the small fluid-filled region and to depend on only the mean fluid pressure at the length scale of the fracture. This similarity solution is unusual as the two length scales of the problem—the radius of the fracture and the radius of the fluid front—evolve according to two different power laws of time. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2853 [...]

Enhanced, unconditionally stable, explicit pseudodynamic algorithm / Shuenn-Yih Chang in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.541–554. Titre : Enhanced, unconditionally stable, explicit pseudodynamic algorithm Type de document : texte imprimé Auteurs : Shuenn-Yih Chang, Auteur Année de publication : 2007 Article en page(s) : pp.541–554. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Comparative  studies  Errors  Algorithms  Dynamic  tests Résumé : In performing a pseudodynamic test, an explicit method is generally preferred over an implicit method since it involves no iteration procedure or extra hardware that is often needed for an implicit method. However, its integration time step is usually limited by stability. Hence, it is very promising for the pseudodynamic testing if an explicit method can have unconditional stability, which might eliminate the limitation on time step for the testing of a multiple degree of freedom system or a substructure system. Although an explicit pseudodynamic algorithm with unconditional stability has been successfully implemented and its superior characteristics have been identified, an enhanced unconditionally stable explicit pseudodynamic algorithm is further proposed. In this study, it is verified that both explicit pseudodynamic algorithms possess the same numerical characteristics in the step-by-step integration. However, the newly developed explicit pseudodynamic algorithm shows better error propagation properties when compared to that developed previously. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2854 [...] [article] Enhanced, unconditionally stable, explicit pseudodynamic algorithm [texte imprimé] / Shuenn-Yih Chang, Auteur . - 2007 . - pp.541–554. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.541–554. Mots-clés : Comparative  studies  Errors  Algorithms  Dynamic  tests Résumé : In performing a pseudodynamic test, an explicit method is generally preferred over an implicit method since it involves no iteration procedure or extra hardware that is often needed for an implicit method. However, its integration time step is usually limited by stability. Hence, it is very promising for the pseudodynamic testing if an explicit method can have unconditional stability, which might eliminate the limitation on time step for the testing of a multiple degree of freedom system or a substructure system. Although an explicit pseudodynamic algorithm with unconditional stability has been successfully implemented and its superior characteristics have been identified, an enhanced unconditionally stable explicit pseudodynamic algorithm is further proposed. In this study, it is verified that both explicit pseudodynamic algorithms possess the same numerical characteristics in the step-by-step integration. However, the newly developed explicit pseudodynamic algorithm shows better error propagation properties when compared to that developed previously. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2854 [...]

Approach for overcoming numerical inaccuracy caused by load discontinuity / Shuenn-Yih Chang in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.555–565 Titre : Approach for overcoming numerical inaccuracy caused by load discontinuity Type de document : texte imprimé Auteurs : Shuenn-Yih Chang, Auteur Année de publication : 2007 Article en page(s) : pp.555–565 Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Computation  Impulsive  Loads  Structural  dynamics  Discontinuities. Résumé : It was found that the discontinuity at the end of an impulse will lead to numerical inaccuracy as this discontinuity will result in an extra impulse and thus an extra displacement in the time history analysis. In addition, this extra impulse is proportional to the discontinuity value at the end of the impulse and the size of integration time step. To overcome this difficulty, an effective approach is proposed to reduce the extra impulse and hence the extra displacement. In fact, the novel approach proposed in this paper is to perform a single small time step immediately upon the termination of applied impulse, whereas other time steps can be conducted by using the step size determined from accuracy consideration in period. The feasibility of this approach is analytically explored. Further, analytical results are confirmed by numerical examples. Numerical studies also show that this approach can be applied to other step-by-step integration methods. It seems that to slightly complicate the programming of dynamic analysis codes is the only disadvantage of this approach. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2855 [...] [article] Approach for overcoming numerical inaccuracy caused by load discontinuity [texte imprimé] / Shuenn-Yih Chang, Auteur . - 2007 . - pp.555–565. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.555–565 Mots-clés : Computation  Impulsive  Loads  Structural  dynamics  Discontinuities. Résumé : It was found that the discontinuity at the end of an impulse will lead to numerical inaccuracy as this discontinuity will result in an extra impulse and thus an extra displacement in the time history analysis. In addition, this extra impulse is proportional to the discontinuity value at the end of the impulse and the size of integration time step. To overcome this difficulty, an effective approach is proposed to reduce the extra impulse and hence the extra displacement. In fact, the novel approach proposed in this paper is to perform a single small time step immediately upon the termination of applied impulse, whereas other time steps can be conducted by using the step size determined from accuracy consideration in period. The feasibility of this approach is analytically explored. Further, analytical results are confirmed by numerical examples. Numerical studies also show that this approach can be applied to other step-by-step integration methods. It seems that to slightly complicate the programming of dynamic analysis codes is the only disadvantage of this approach. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2855 [...]

Viscous heating of fluid dampers under small and large amplitude motions / Cameron J. Black in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.566–577. Titre : Viscous heating of fluid dampers under small and large amplitude motions : experimental studies and parametric modeling Type de document : texte imprimé Auteurs : Cameron J. Black, Auteur ; Nicos Makris, Auteur Année de publication : 2007 Article en page(s) : pp.566–577. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Damping  Heating  Monitoring  Earthquake  engineering  Parameters  Earthquake  resistant  structures Résumé : This paper summarizes the results from a comprehensive experimental program in an effort to better understand the phenomenon of viscous heating of fluid dampers under small-stroke (wind loading) and large-stroke (earthquake loading) motions. Two dampers, one with 15-kip and one with 250-kip force output at peak design velocity, have been instrumented and tested under various amplitudes and frequencies. Temperature histories at different locations along the damper casing and within the silicon fluid that undergoes the shearing action have been recorded. Experimental data under small-stroke motions of the 250-kip damper showed that a single closed-form expression derived from first principles is capable of predicting the temperature rise at different locations of the damper with fidelity. The recorded data under long-stroke motions suggest a two-parameter law of cooling that allows the estimation of the internal temperature of the silicon oil once the external temperature on the damper casing is known. The presented cooling law is an extension of Newton’s law of cooling. The study concludes that for both dampers, the same values of the model parameters provide a good approximation of the cooling behavior. The study presents a valuable formula that can be used in practice to estimate the internal fluid temperature of the damper given the external shell temperature. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2856 [...] [article] Viscous heating of fluid dampers under small and large amplitude motions : experimental studies and parametric modeling [texte imprimé] / Cameron J. Black, Auteur ; Nicos Makris, Auteur . - 2007 . - pp.566–577. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.566–577. Mots-clés : Damping  Heating  Monitoring  Earthquake  engineering  Parameters  Earthquake  resistant  structures Résumé : This paper summarizes the results from a comprehensive experimental program in an effort to better understand the phenomenon of viscous heating of fluid dampers under small-stroke (wind loading) and large-stroke (earthquake loading) motions. Two dampers, one with 15-kip and one with 250-kip force output at peak design velocity, have been instrumented and tested under various amplitudes and frequencies. Temperature histories at different locations along the damper casing and within the silicon fluid that undergoes the shearing action have been recorded. Experimental data under small-stroke motions of the 250-kip damper showed that a single closed-form expression derived from first principles is capable of predicting the temperature rise at different locations of the damper with fidelity. The recorded data under long-stroke motions suggest a two-parameter law of cooling that allows the estimation of the internal temperature of the silicon oil once the external temperature on the damper casing is known. The presented cooling law is an extension of Newton’s law of cooling. The study concludes that for both dampers, the same values of the model parameters provide a good approximation of the cooling behavior. The study presents a valuable formula that can be used in practice to estimate the internal fluid temperature of the damper given the external shell temperature. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2856 [...]

Time-dependent response of an axially loaded elastic bar in a multilayered poroelastic medium / T. Senjuntichai in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.578–587. Titre : Time-dependent response of an axially loaded elastic bar in a multilayered poroelastic medium Type de document : texte imprimé Auteurs : T. Senjuntichai, Auteur ; N. Sornpakdee, Auteur ; J. Teerawong, Auteur Année de publication : 2007 Article en page(s) : pp.578–587. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Consolidation  Layered  systems  Piles  Poroelasticity  Time  dependence Résumé : This paper considers load transfer from an axially loaded long elastic bar into a multilayered poroelastic half-space. The problem is analyzed by decomposing the bar-half-space system into an extended half-space governed by Biot’s theory of poroelasticity and a one-dimensional fictitious bar. The interaction problem is formulated in the Laplace transform domain. Vertical displacement of the bar is approximated by an exponential series with a set of arbitrary functions. The arbitrary functions are determined by using a variational method. The vertical displacement influence function of a multilayered half-space subjected to a buried uniform vertical patch load is required in the variational formulation. The required influence function is obtained by employing a previously developed exact stiffness matrix method. Time domain solutions are computed by using a numerical Laplace inversion scheme. Selected numerical results are presented to portray the influence of the bar length–radius ratio, layer configuration, poroelastic material parameters, and loading time history on the time dependent response of a bar. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2857 [...] [article] Time-dependent response of an axially loaded elastic bar in a multilayered poroelastic medium [texte imprimé] / T. Senjuntichai, Auteur ; N. Sornpakdee, Auteur ; J. Teerawong, Auteur . - 2007 . - pp.578–587. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.578–587. Mots-clés : Consolidation  Layered  systems  Piles  Poroelasticity  Time  dependence Résumé : This paper considers load transfer from an axially loaded long elastic bar into a multilayered poroelastic half-space. The problem is analyzed by decomposing the bar-half-space system into an extended half-space governed by Biot’s theory of poroelasticity and a one-dimensional fictitious bar. The interaction problem is formulated in the Laplace transform domain. Vertical displacement of the bar is approximated by an exponential series with a set of arbitrary functions. The arbitrary functions are determined by using a variational method. The vertical displacement influence function of a multilayered half-space subjected to a buried uniform vertical patch load is required in the variational formulation. The required influence function is obtained by employing a previously developed exact stiffness matrix method. Time domain solutions are computed by using a numerical Laplace inversion scheme. Selected numerical results are presented to portray the influence of the bar length–radius ratio, layer configuration, poroelastic material parameters, and loading time history on the time dependent response of a bar. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2857 [...]

Estimating joint failure probability of series structural systems / Yan-Gang Zhao in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.588–596. Titre : Estimating joint failure probability of series structural systems Type de document : texte imprimé Auteurs : Yan-Gang Zhao, Auteur ; Wei-Qiu Zhong, Auteur ; Alfredo H.-S. Ang, Auteur Année de publication : 2007 Article en page(s) : pp.588–596. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Structural  reliability  System  reliability  Joints  Failures  Integrated  systems Résumé : The failure probability of a series structural system theoretically involves multidimensional integration and is usually difficult to calculate. The search for efficient computational procedures for estimating system reliability has resulted in several approaches, including bounding techniques and efficient Monte Carlo simulations. For the narrow bound method, the joint failure probability of every pair of failure modes needs to be calculated. In the present paper, in order to improve the accuracy of the narrow bound estimation method, a computationally effective point estimation method for calculating the joint probability of every pair of failure modes is proposed and examined for series systems. Based on the computational results of several illustrative examples, it can be seen that the results by the present method are in good agreement with those obtained through integration. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2858 [...] [article] Estimating joint failure probability of series structural systems [texte imprimé] / Yan-Gang Zhao, Auteur ; Wei-Qiu Zhong, Auteur ; Alfredo H.-S. Ang, Auteur . - 2007 . - pp.588–596. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.588–596. Mots-clés : Structural  reliability  System  reliability  Joints  Failures  Integrated  systems Résumé : The failure probability of a series structural system theoretically involves multidimensional integration and is usually difficult to calculate. The search for efficient computational procedures for estimating system reliability has resulted in several approaches, including bounding techniques and efficient Monte Carlo simulations. For the narrow bound method, the joint failure probability of every pair of failure modes needs to be calculated. In the present paper, in order to improve the accuracy of the narrow bound estimation method, a computationally effective point estimation method for calculating the joint probability of every pair of failure modes is proposed and examined for series systems. Based on the computational results of several illustrative examples, it can be seen that the results by the present method are in good agreement with those obtained through integration. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2858 [...]

Vibration of annular mindlin plates with small cores / Cahyaning Tias in Journal of engineering mechanics, Vol. 133 N°5 (Mai 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.597–600. Titre : Vibration of annular mindlin plates with small cores Type de document : texte imprimé Auteurs : Cahyaning Tias, Auteur ; Wang, C. M., Auteur ; Wang, C. Y., Auteur Année de publication : 2007 Article en page(s) : pp.597–600. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Vibration  Plates  Frequency Résumé : In most publications on vibration of annular plates, the natural frequencies are only presented for inner radius as small as one-tenth of its outer radius, but there are hardly any results presented for cores smaller than this inner radius value. This is attributed to severe scaling problems upon using numerical techniques to obtain the fundamental frequency of plates when the inner radius becomes very small. This study aims to solve this class of plate vibration problem where the annular plates are thick and their core radii are much less than one-tenth of the outer radius. The analysis involved using the Mindlin plate theory so as to allow for the effects of transverse shear deformation and rotary inertia and the truncation of the terms in the Bessel functions defining the characteristic equations in order to overcome the scaling problem. Eventually, the fundamental frequency of a thick annular plate could be deduced as finite or zero when the inner radius approaches zero. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2859 [...] [article] Vibration of annular mindlin plates with small cores [texte imprimé] / Cahyaning Tias, Auteur ; Wang, C. M., Auteur ; Wang, C. Y., Auteur . - 2007 . - pp.597–600. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°5 (Mai 2007) . - pp.597–600. Mots-clés : Vibration  Plates  Frequency Résumé : In most publications on vibration of annular plates, the natural frequencies are only presented for inner radius as small as one-tenth of its outer radius, but there are hardly any results presented for cores smaller than this inner radius value. This is attributed to severe scaling problems upon using numerical techniques to obtain the fundamental frequency of plates when the inner radius becomes very small. This study aims to solve this class of plate vibration problem where the annular plates are thick and their core radii are much less than one-tenth of the outer radius. The analysis involved using the Mindlin plate theory so as to allow for the effects of transverse shear deformation and rotary inertia and the truncation of the terms in the Bessel functions defining the characteristic equations in order to overcome the scaling problem. Eventually, the fundamental frequency of a thick annular plate could be deduced as finite or zero when the inner radius approaches zero. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A5%2859 [...]

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