The structural reliability analysis allows us to orient the maintenance operations in function of... more The structural reliability analysis allows us to orient the maintenance operations in function of the influence of parameter uncertainties. The coupling of finite element with reliability methods is the only tool allowing us to analyse real structure with complex behaviour. However, this coupling implies some numerical difficulties which decrease the use of the reliability methods. In this work, two mechanical-reliability coupling methods are proposed and applied to the cooling tower of a nuclear power plant. In the reliability study, two failure scenarios have been considered : the serviceability limit state defined by excessive cracking and the ultimate limit state defined by elastic-plastic failure of the shell. The results allow us to identify the roles of different variables on the structural integrity.
Echocardiography plays a major role in diagnosis, etiology and severity of Mitral Stenosis (MS), ... more Echocardiography plays a major role in diagnosis, etiology and severity of Mitral Stenosis (MS), analysis of valve anatomy and decision-making for intervention. This technique has also a crucial role to assess consequences of MS and follow up of patients after medical or surgical intervention. In this article we review the role of conventional echocardiography in assessment of mitral stenosis and future direction of this modality using 3D echocardiography.
Mitral regurgitation (MR) is defined as the loss of the smooth and adequate trimming closure of t... more Mitral regurgitation (MR) is defined as the loss of the smooth and adequate trimming closure of the mitral valve, which results in the reflux of blood from the left ventricle into the left atrium during systole. The functional competence of the mitral valve relies on the proper and coordinated interaction of the following structures: the mitral annulus, and leaflets, chordate tendineae, papillary muscles, left atrium and the left ventricles. This article will describe the echocardiography assessment of the mitral valve regurgitation with special emphasis on the trans-esophageal and 3D echocardiography. The echocardiography images were all original with special attention to the unique surgical view of the images.
Les aéro-réfrigérants sont des structures en béton armé soumises à différents mécanismes de vieil... more Les aéro-réfrigérants sont des structures en béton armé soumises à différents mécanismes de vieillissement. Les données du matériau, les chargements et les conditions environnementales régissant ces mécanismes sont affectés par une importante variabilité. Il est nécessaire ...
Structural and Multidisciplinary Optimization, 2004
The objective of this work is to integrate reliability analysis into topology optimization proble... more The objective of this work is to integrate reliability analysis into topology optimization problems. The new model, in which we introduce reliability constraints into a deterministic topology optimization formulation, is called Reliability-Based Topology Optimization (RBTO). Several applications show the importance of this integration. The application of the RBTO model gives a different topology relative to deterministic topology optimization. We also find that the RBTO model yields structures that are more reliable than those produced by deterministic topology optimization (for the same weight).
Reliability analyses of structural components aim at estimating the probability that the external... more Reliability analyses of structural components aim at estimating the probability that the external loading exceeds the structure resistance. In industrial cases, when finite element calculations are needed, the failure of the structure cannot be defined by an explicit function of the random variables. The present paper deals with a feasibility study of the reliability analysis of a typical natural-draught cooling tower subjected to different combined actions. A 3D finite element analysis is coupled with probabilistic methods. The mechanical deterministic model is validated by direct comparison of the corresponding results with others obtained by different finite element codes. Different coupling methods are used for the reliability analysis. Sensitivity analyses are also performed in order to evaluate the influence of the probabilistic definition of the random variables. The results emphasize a good agreement of the different methods. They allow to define the best modeling options to use in industrial frameworks by establishing a parallel between the precision of the reliability results, the accuracy of the model and the cost performances.
L'optimisation mecano-fiabiliste des structures consiste a definir le meilleur compromis entr... more L'optimisation mecano-fiabiliste des structures consiste a definir le meilleur compromis entre le cout et la fiabilite d'un dimensionnement. Le couplage entre la modelisation mecanique, l'analyse fiabiliste et les methodes d'optimisation souleve de delicats problemes de convergence et est tres consommateur en ressources de calcul par rapport a une simple analyse mecanique. Traditionnellement, la resolution du probleme d'optimisation mecano-fiabiliste est obtenue par altenance des phases de fiabilite et d'optimisation. Cette approche conduit a une grande lenteur numerique, ce qui decourage toute application pratique sur des structures reelles. Pour remedier a cette difficulte, nous proposons dans cet article une methode efficace basee sur la resolution simultanee des problemes de fiabilite et d'optimisation. Cette procedure conduit a une convergence parallele des deux problemes. Deux applications numeriques sur une poutre en profile metallique et sur un portique en beton arme montrent l'interet de l'optimisation mecano-fiabiliste et l'efficacite de l'approche proposee.
− Computer-Aided Reliable and Optimal Design (CAROD) system is an efficient tool defining the bes... more − Computer-Aided Reliable and Optimal Design (CAROD) system is an efficient tool defining the best compromise between cost and safety. Using the concurrent engineering concept, it can supply the designer with all numerical information in the design process. ...
The structural reliability analysis allows us to orient the maintenance operations in function of... more The structural reliability analysis allows us to orient the maintenance operations in function of the influence of parameter uncertainties. The coupling of finite element with reliability methods is the only tool allowing us to analyse real structure with complex behaviour. However, this coupling implies some numerical difficulties which decrease the use of the reliability methods. In this work, two mechanical-reliability coupling methods are proposed and applied to the cooling tower of a nuclear power plant. In the reliability study, two failure scenarios have been considered : the serviceability limit state defined by excessive cracking and the ultimate limit state defined by elastic-plastic failure of the shell. The results allow us to identify the roles of different variables on the structural integrity.
Echocardiography plays a major role in diagnosis, etiology and severity of Mitral Stenosis (MS), ... more Echocardiography plays a major role in diagnosis, etiology and severity of Mitral Stenosis (MS), analysis of valve anatomy and decision-making for intervention. This technique has also a crucial role to assess consequences of MS and follow up of patients after medical or surgical intervention. In this article we review the role of conventional echocardiography in assessment of mitral stenosis and future direction of this modality using 3D echocardiography.
Mitral regurgitation (MR) is defined as the loss of the smooth and adequate trimming closure of t... more Mitral regurgitation (MR) is defined as the loss of the smooth and adequate trimming closure of the mitral valve, which results in the reflux of blood from the left ventricle into the left atrium during systole. The functional competence of the mitral valve relies on the proper and coordinated interaction of the following structures: the mitral annulus, and leaflets, chordate tendineae, papillary muscles, left atrium and the left ventricles. This article will describe the echocardiography assessment of the mitral valve regurgitation with special emphasis on the trans-esophageal and 3D echocardiography. The echocardiography images were all original with special attention to the unique surgical view of the images.
Les aéro-réfrigérants sont des structures en béton armé soumises à différents mécanismes de vieil... more Les aéro-réfrigérants sont des structures en béton armé soumises à différents mécanismes de vieillissement. Les données du matériau, les chargements et les conditions environnementales régissant ces mécanismes sont affectés par une importante variabilité. Il est nécessaire ...
Structural and Multidisciplinary Optimization, 2004
The objective of this work is to integrate reliability analysis into topology optimization proble... more The objective of this work is to integrate reliability analysis into topology optimization problems. The new model, in which we introduce reliability constraints into a deterministic topology optimization formulation, is called Reliability-Based Topology Optimization (RBTO). Several applications show the importance of this integration. The application of the RBTO model gives a different topology relative to deterministic topology optimization. We also find that the RBTO model yields structures that are more reliable than those produced by deterministic topology optimization (for the same weight).
Reliability analyses of structural components aim at estimating the probability that the external... more Reliability analyses of structural components aim at estimating the probability that the external loading exceeds the structure resistance. In industrial cases, when finite element calculations are needed, the failure of the structure cannot be defined by an explicit function of the random variables. The present paper deals with a feasibility study of the reliability analysis of a typical natural-draught cooling tower subjected to different combined actions. A 3D finite element analysis is coupled with probabilistic methods. The mechanical deterministic model is validated by direct comparison of the corresponding results with others obtained by different finite element codes. Different coupling methods are used for the reliability analysis. Sensitivity analyses are also performed in order to evaluate the influence of the probabilistic definition of the random variables. The results emphasize a good agreement of the different methods. They allow to define the best modeling options to use in industrial frameworks by establishing a parallel between the precision of the reliability results, the accuracy of the model and the cost performances.
L'optimisation mecano-fiabiliste des structures consiste a definir le meilleur compromis entr... more L'optimisation mecano-fiabiliste des structures consiste a definir le meilleur compromis entre le cout et la fiabilite d'un dimensionnement. Le couplage entre la modelisation mecanique, l'analyse fiabiliste et les methodes d'optimisation souleve de delicats problemes de convergence et est tres consommateur en ressources de calcul par rapport a une simple analyse mecanique. Traditionnellement, la resolution du probleme d'optimisation mecano-fiabiliste est obtenue par altenance des phases de fiabilite et d'optimisation. Cette approche conduit a une grande lenteur numerique, ce qui decourage toute application pratique sur des structures reelles. Pour remedier a cette difficulte, nous proposons dans cet article une methode efficace basee sur la resolution simultanee des problemes de fiabilite et d'optimisation. Cette procedure conduit a une convergence parallele des deux problemes. Deux applications numeriques sur une poutre en profile metallique et sur un portique en beton arme montrent l'interet de l'optimisation mecano-fiabiliste et l'efficacite de l'approche proposee.
− Computer-Aided Reliable and Optimal Design (CAROD) system is an efficient tool defining the bes... more − Computer-Aided Reliable and Optimal Design (CAROD) system is an efficient tool defining the best compromise between cost and safety. Using the concurrent engineering concept, it can supply the designer with all numerical information in the design process. ...
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Papers by Alaa Mohamed