Guillaume Hervé - Academia.edu (original) (raw)
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Papers by Guillaume Hervé
In this work we aim to construct the most efficient solution strategy for solving highly complex ... more In this work we aim to construct the most efficient solution strategy for solving highly complex nonlinear problems, which are characterized by the presence of different scales in time and space. In particular, we address the class of problems where the space or time scales can be separated and dealt with independently in the most appropriate manner. (The latter is
Engineering Computations, 2015
Modeling reinforced concrete is an important requirement for civil engineering calculation. Parti... more Modeling reinforced concrete is an important requirement for civil engineering calculation. Particularly, engineers need to have information about both rebar and concrete. The need for modeling them separately comes obviously to allow local and global analysis of a reinforced concrete structure. This paper focuses on the validation of modeling of reinforced concrete with the CSCM material and Constrained Lagrange In Solid to tie the rebar. The interest for this method is the possibility to mesh separately concrete and rebar and to avoid overmeshing caused by the concordance between concrete and rebar nodes. This coupling is commonly used to model Eurocodode 2 compatible reinforced concrete. In order to validate the method, a comparison between analytical and numerical results is presented for simple civil engineering frames (beam and portal frame). This first study is made with a pseudo-dynamic loading. First, a four points bending test is presented for different case of steel rate ...
La TVRC, initialement proposée par Ladevèze, offre une réduction substantielle de la taille des p... more La TVRC, initialement proposée par Ladevèze, offre une réduction substantielle de la taille des problèmes à résoudre lors d’un calcul de structure en vibration moyenne fréquence. Néanmoins cette méthode, de part son approche fréquentielle, perd de son efficacité lors d’une simulation numérique nécessitant une réponse sur une large bande de fréquence. Avec l’utilisation d’approximants de Padé, l’objectif est de réduire le nombre de fréquences auxquelles la solution complète doit être calculée, et d’interpoler la solution entre ces fréquences. Cette approche est d’autant facilitée par l’expression de la dépendance en fréquence sous la forme de fonctions scalaires en facteur des matrices globales.
The purpose of this paper is to propose methods to take appropriately into account the high frequ... more The purpose of this paper is to propose methods to take appropriately into account the high frequency content of the floor response spectra in case of aircraft crash. The different methologies are compared based on an industrial example, considering signal processing and non linear elastic response spectra with dry slip constitutive equations within the standard writing form of the dynamic equations.
This work takes place in the French national civil engineering project CEOS.fr
The determination of the shaking induced by an aircraft impact on an industrial structure require... more The determination of the shaking induced by an aircraft impact on an industrial structure requires dynamic studies. The determination of the response by using classical finite element method (FEM) associated with explicit numerical schemes requires significant calculation time, especially during the transient stage. Many calculations may be required due to the possible wide range of scenarios. Moreover, the medium frequency range has to be appropriately considered and therefore the mesh has to be very fine, resulting in a refined time discretization. The purpose of our study is to develop new ways for calculating the induced vibrations in reinforced concrete structures submitted to a commercial aircraft impact (see Figure 1). The cutoff frequency for this type of loading is typically within the 50 to 100 Hz range, which would be referred to as the high frequency range [HER13]. Taking into account this type of problem and assuming that the structure is appropriately sized to withstan...
The vibrating motion induced by an airplane crash onto the reinforced concrete structure of a nuc... more The vibrating motion induced by an airplane crash onto the reinforced concrete structure of a nuclear power plant is carried out following modeling methodologies that indirectly consider that this motion is propagating like a seismic motion. In term of impact signal, the modeling of the impact is carried out assuming methodologies that have not considerably changed for several decades mainly because the signals are often considered by applying an impact force on a an area that remains quite constant over the time.
Déterminer les vibrations induites dans une structure soumise à un impact requiert une étude dyna... more Déterminer les vibrations induites dans une structure soumise à un impact requiert une étude dynamique. Si on utilise un calcul aux EF associé à une résolution temporelle explicite, on est conduit à avoir des temps de calculs extrêmement long, surtout pour décrire la phase transitoire. C'est pourquoi nous proposons d'utiliser la TVRC pour résoudre ce problème de vibration aux moyennes fréquences.
The purpose of our study consists in the research of new ways of designing reinforced concrete st... more The purpose of our study consists in the research of new ways of designing reinforced concrete structures submitted to commercial aircraft impact. We will particularly focus on the shaking resulting from such load case. The cutoff frequency for this type of loading is typically within the to range, which would be refered to as the medium frequency range [1]. The determination of the shaking induced by an aircraft impact on an industrial structure requires dynamic simulation. The response, especially during the transient stage, cannot be completely described using classical finite element method associated with explicit numerical schemes. Indeed, the medium frequency range is often ignored unless the calculation is carried out with a very refined mesh and consequently, a refined time discretization. This could lead to prohibitive computation times. The linear behaviour is not questioned outside the impact area, however, the non-linearity of the portion of the impacted structure can have a significant influence. The method consists in an initial FFT (Fast Fourier Transform) of the signal loading. The VTCR then ensures an efficient calculation of the response of the structure. The obtained signals are then processed by inverse FFT (IFFT) to reconstruct a time signal and a response spectrum. A new multiscale computational strategy, the Variational Theory of Complex Rays [2], is developed for the analysis of the vibration of structures in the medium frequency regime. Using two-scale shape functions which satisfy the dynamic equation and the constituve relation within each substructure, the VTCR can be viewed as a mean of expressing the power balance at the different interfaces between substructures in a variational form. The solution is searched as a combination of propagative and evanescent waves. Only the amplitude of these waves, which are slowly varying quantities of the solution, is discretized. This leads to a numerical model with few degrees of freedom in comparison with a Finite Element model. The aim is to develop a robust method to get mid-frequency spectra generated by an aircraft impact on a simplified structure.
In this work we address some of the present threats posed to engineering structures in placing th... more In this work we address some of the present threats posed to engineering structures in placing them under extreme loading conditions. The common ground for the problems studied herein from the viewpoint of structural integrity is their transient nature characterized by different time scales and the need to evaluate the consequence for a high level of uncertainty in quantifying the
Engineering Computations, 2005
... (4) Equation 1 is used to calculate the current force. The load-time history can thus be dete... more ... (4) Equation 1 is used to calculate the current force. The load-time history can thus be determined as follows in Figure 1. Other same methods have been developed by Bangash [2]. 2 Page 3. ... (tk)l = tpk − (tpk − tpk−1)Pk Pk + Pk−1 and (tk)r = tpk + (tpk+1 − tpk)Pk+1 Pk+1 + Pk ...
Engineering Computations, 2009
In this work we aim to construct the most efficient solution strategy for solving highly complex ... more In this work we aim to construct the most efficient solution strategy for solving highly complex nonlinear problems, which are characterized by the presence of different scales in time and space. In particular, we address the class of problems where the space or time scales can be separated and dealt with independently in the most appropriate manner. (The latter is
Engineering Computations, 2015
Modeling reinforced concrete is an important requirement for civil engineering calculation. Parti... more Modeling reinforced concrete is an important requirement for civil engineering calculation. Particularly, engineers need to have information about both rebar and concrete. The need for modeling them separately comes obviously to allow local and global analysis of a reinforced concrete structure. This paper focuses on the validation of modeling of reinforced concrete with the CSCM material and Constrained Lagrange In Solid to tie the rebar. The interest for this method is the possibility to mesh separately concrete and rebar and to avoid overmeshing caused by the concordance between concrete and rebar nodes. This coupling is commonly used to model Eurocodode 2 compatible reinforced concrete. In order to validate the method, a comparison between analytical and numerical results is presented for simple civil engineering frames (beam and portal frame). This first study is made with a pseudo-dynamic loading. First, a four points bending test is presented for different case of steel rate ...
La TVRC, initialement proposée par Ladevèze, offre une réduction substantielle de la taille des p... more La TVRC, initialement proposée par Ladevèze, offre une réduction substantielle de la taille des problèmes à résoudre lors d’un calcul de structure en vibration moyenne fréquence. Néanmoins cette méthode, de part son approche fréquentielle, perd de son efficacité lors d’une simulation numérique nécessitant une réponse sur une large bande de fréquence. Avec l’utilisation d’approximants de Padé, l’objectif est de réduire le nombre de fréquences auxquelles la solution complète doit être calculée, et d’interpoler la solution entre ces fréquences. Cette approche est d’autant facilitée par l’expression de la dépendance en fréquence sous la forme de fonctions scalaires en facteur des matrices globales.
The purpose of this paper is to propose methods to take appropriately into account the high frequ... more The purpose of this paper is to propose methods to take appropriately into account the high frequency content of the floor response spectra in case of aircraft crash. The different methologies are compared based on an industrial example, considering signal processing and non linear elastic response spectra with dry slip constitutive equations within the standard writing form of the dynamic equations.
This work takes place in the French national civil engineering project CEOS.fr
The determination of the shaking induced by an aircraft impact on an industrial structure require... more The determination of the shaking induced by an aircraft impact on an industrial structure requires dynamic studies. The determination of the response by using classical finite element method (FEM) associated with explicit numerical schemes requires significant calculation time, especially during the transient stage. Many calculations may be required due to the possible wide range of scenarios. Moreover, the medium frequency range has to be appropriately considered and therefore the mesh has to be very fine, resulting in a refined time discretization. The purpose of our study is to develop new ways for calculating the induced vibrations in reinforced concrete structures submitted to a commercial aircraft impact (see Figure 1). The cutoff frequency for this type of loading is typically within the 50 to 100 Hz range, which would be referred to as the high frequency range [HER13]. Taking into account this type of problem and assuming that the structure is appropriately sized to withstan...
The vibrating motion induced by an airplane crash onto the reinforced concrete structure of a nuc... more The vibrating motion induced by an airplane crash onto the reinforced concrete structure of a nuclear power plant is carried out following modeling methodologies that indirectly consider that this motion is propagating like a seismic motion. In term of impact signal, the modeling of the impact is carried out assuming methodologies that have not considerably changed for several decades mainly because the signals are often considered by applying an impact force on a an area that remains quite constant over the time.
Déterminer les vibrations induites dans une structure soumise à un impact requiert une étude dyna... more Déterminer les vibrations induites dans une structure soumise à un impact requiert une étude dynamique. Si on utilise un calcul aux EF associé à une résolution temporelle explicite, on est conduit à avoir des temps de calculs extrêmement long, surtout pour décrire la phase transitoire. C'est pourquoi nous proposons d'utiliser la TVRC pour résoudre ce problème de vibration aux moyennes fréquences.
The purpose of our study consists in the research of new ways of designing reinforced concrete st... more The purpose of our study consists in the research of new ways of designing reinforced concrete structures submitted to commercial aircraft impact. We will particularly focus on the shaking resulting from such load case. The cutoff frequency for this type of loading is typically within the to range, which would be refered to as the medium frequency range [1]. The determination of the shaking induced by an aircraft impact on an industrial structure requires dynamic simulation. The response, especially during the transient stage, cannot be completely described using classical finite element method associated with explicit numerical schemes. Indeed, the medium frequency range is often ignored unless the calculation is carried out with a very refined mesh and consequently, a refined time discretization. This could lead to prohibitive computation times. The linear behaviour is not questioned outside the impact area, however, the non-linearity of the portion of the impacted structure can have a significant influence. The method consists in an initial FFT (Fast Fourier Transform) of the signal loading. The VTCR then ensures an efficient calculation of the response of the structure. The obtained signals are then processed by inverse FFT (IFFT) to reconstruct a time signal and a response spectrum. A new multiscale computational strategy, the Variational Theory of Complex Rays [2], is developed for the analysis of the vibration of structures in the medium frequency regime. Using two-scale shape functions which satisfy the dynamic equation and the constituve relation within each substructure, the VTCR can be viewed as a mean of expressing the power balance at the different interfaces between substructures in a variational form. The solution is searched as a combination of propagative and evanescent waves. Only the amplitude of these waves, which are slowly varying quantities of the solution, is discretized. This leads to a numerical model with few degrees of freedom in comparison with a Finite Element model. The aim is to develop a robust method to get mid-frequency spectra generated by an aircraft impact on a simplified structure.
In this work we address some of the present threats posed to engineering structures in placing th... more In this work we address some of the present threats posed to engineering structures in placing them under extreme loading conditions. The common ground for the problems studied herein from the viewpoint of structural integrity is their transient nature characterized by different time scales and the need to evaluate the consequence for a high level of uncertainty in quantifying the
Engineering Computations, 2005
... (4) Equation 1 is used to calculate the current force. The load-time history can thus be dete... more ... (4) Equation 1 is used to calculate the current force. The load-time history can thus be determined as follows in Figure 1. Other same methods have been developed by Bangash [2]. 2 Page 3. ... (tk)l = tpk − (tpk − tpk−1)Pk Pk + Pk−1 and (tk)r = tpk + (tpk+1 − tpk)Pk+1 Pk+1 + Pk ...
Engineering Computations, 2009