Effet de la durée d'impulsion et la forme sur flambage dynamique des panneaux raidis sous compression axiale

Ce papier présent le flambage dynamique des panneaux raidis est analysé numériquement grâce à une formulation incrémentale non linéaire utilisant la procédure d'intégration explicite en temps sous la logiciel Abaqus. Fixation la durée d'impulsion et l'ampleur de la déviation initiale ainsi que le rapport de la dégradation des matériaux dans la zone affectée par la chaleur, la charge de flambage dynamique a été identifié pour chaque configuration donnée. Ce processus a permis la dérivation d'un modèle de surface de réponse qui a été utilisé avec la méthode de Monte Carlo pour déterminer la fiabilité du panneau raidi en ce qui concerne l'état de flambage dynamique. Le critère de flambement Budiansky et Roth a été utilisé pour prédire l'instabilité sous une donnée modèle de charge dynamique. Différents profils y compris rectangulaire, triangulaire, double-triangulaire et demi-sinus ont été examinées. Les résultats obtenus ont montré que tant la durée d'impulsion et la forme d'impulsion ont un effet drastique sur la force de flambage. Pour la limite considérée conditions, des impulsions ayant des périodes qui sont comparables à deux fois la période de la première mode propre de vibrations ont été trouvés pour réduire la résistance à la déformation à 67% du statique flambage valeur dans le régime en plastique élastique et 44% dans le régime élastique

Fonctionnement De La Plage d’El Jadida (Côte Atlantique Marocaine) : Apport De L’étude Morphodynamique, Sédimentologique, Minéralogique Et De L’action Anthropique

The multidisciplinary study of the beach of El Jadida and its sediments reflects that its shape is asymmetrical, narrow and contrasting between SE and NW which closely affects marine and wind dynamics and functioning of this beach. As profiles of beaches and the extension of the area affected by the tides, they present an argument for the elevation of the sea level had certainly warming. In addition to the Cretaceous lime stone be drock, the Quaternary calcarenites localized only in the SE richer, even more, this place in carbonate more than elsewhere in particular in winter. El Jadida beach sediments are basically homogeneous and well classified (coarse and fine) and reflect a more or less closed environment. The rocks of the SE affect the marine dynamics in rendering the texture of coarse and slightly heterogeneous sediments especially in winter but the correct classification is on the side fine sediments. The emitting provinces of minerals fuelling El Jadida Beach, via the Oued Oum Rbia and littoral drift, are essentially Jacqueline and Sidi Said Maachou El Jadida beach is under anthropogenic pressure considerable (proliferation of buildings) that promote the reduction of the area of the beach and therefore it creates a malfunction of this and an imbalance between it and marine and wind dynamics. Where urgent intervention and sound management that apply to the protection of this beach and its environment

Les formations fluviatiles quaternaires de la plaine de Doukkala (Méséta Occidentale Marocaine). Sédimentologie et nouvelles données chronostratigraphiques

The Quaternary fluvial formations of the Doukkala plain are, until now, slightly studied. Our study has allowed to precise that the fluvial terraces of the oued "the Ourn Rbia oued", are clearly distinguished from the secondary oueds terraces by the dynamic deposit of the alluvial materials. Moreover, the mammal fossils recolted from some of these terraces allow to review the ages attributed by Gigout (1951)

L’érosion De La Falaise De Sidi Bouzid (Côte Atlantique Marocaine) : Quantification Et Évolution Spatio-Temporelle

The study of the coastal cliff "F1" of Sidi Bouzid shows that it is discontinuous, high, complex and very exposed to the marine dynamics. It is subdivided into two sectors in total, consisting of five zones. A second small cliff "F2" is visible, at the foot of F1 during the storms. These two cliffs bear witness to an oscillation of sea level during the Recent Quaternary. This work shows also a clear close relationship between the quantity and the quality of the blocks, on the one hand, and the nature of the fairly limited space on which have accumulated on the other hand. At the stratigraphic level, the cliff in the Northeast sector is characterized by alternating beds of limestone and Cretaceous Marly levels with evidence of tectonic activity. In the Southwest, Quaternary is dominated by mainly continental deposits, with caliches, overcoming the Cretaceous limestones. The block settings are variable and influenced by the height of the cliff. The degree of fragmentation of blocks during their fall affects their shape: elongated (zone V) because little fragile joints and resistance as well as thick banks of limestone or less elongated because hardness of the platform and fragile joints (zone I). Reflecting that blocks inherit, their form of the morphology, structure and lithological nature of the formations that make up. Quantitatively, the number, density and the volume of blocks are variable and proportional but important (I and V zones) of active erosion due to exposure of the cliff to the marine dynamics. However, the number and low density with the high volume of blocks (zone III) reflect indurated and lithological nature (caliches) but less rich in joints of Quaternary deposits On the indices of the blocks, they show little variation but a slight peculiarity of zone V (extended blocks). The layout of blocks shows a difference between blocks of the Northeast and the Southwest sector due to the different orientation of the cliffs but also the turn and the onslaught of the waves in zone III. This study also shows a clear decrease in the cliff and the risk that it is requiring for its protection

Backstepping nonlinear control to maximize energy capture in a variable speed wind turbine

We are considering the problem of maximum power point tracking MPPT in wind energy conversion system (WECS). The paper proposes a new control strategy to maximize the wind aerodynamic energy captured in variable speed wind turbine with a separately excited DC-Generator and transformed to the battery through a controlled DC-DC converter. The proposed strategy controls the stip speed ratio via the rotor angular speed to an optimum point at wich the power coefficient is maximal. The controller is designed using the backstepping technique. A formal analysis based on lyapunov stability is developed to describe the control system performances. In addition to closed-loop global asymptotic stability, it is proved that the controller actually meets the MPPT requirement. The above results are confirmed by simulations.

Stability analysis of embankment dam and forecast of failure scope based on point safety factor

Abstract In the context of verification of civil engineering structures stability and determination of sliding surface and safety factor, a careful analysis of several parameters was carried out to guarantee their safety against failure. To quantitatively forecast failure scope, the embankment dam located on Oued Rhiss in the province of Hocemia is chosen as the model of this study. A static stability analysis is performed by using the Slope/W software. A parametric study performed to evaluate the influence of dam's height, the height of water in the reservoir and the length of drains on the safety coefficient and pore pressures. Reliability analysis elaborated by using the Comrel application, and it allows to statistically quantifying the probability of failure by employing the Monte Carlo distribution. Results show that the dam structure has some weak zones and not strong enough as the safety factor is less than one, it is related to structure's parameters and the drainage system

Buckling analysis of rectangular plates with centered cut-out subjected to in-plane two directions under different boundary conditions

Abstract In this research, buckling behavior of rectangular plates of symmetric and antisymmetric laminated composite having centered circular hole under in-plane static loadings is analyzed with the aid of first shear deformation theory and the finite element method is used to find critical loads. The presence of hole may cause redistribution of stresses in plates with reduction of stability. The aim of the current paper is to find critical buckling load. The loads depend on many parameters like geometric aspect ratios (a/b) and (d/b), plate thickness (t), diameter of the circular hole (d), orientation of ply and boundary conditions. Numerical simulations for various boundary conditions obtained are shown in tables and graphical forms and compared with each other

Effect of pulse duration and shape on dynamic buckling of stiffened panels

Dynamic buckling of stiffened panels under axial compression loading having the form of finite duration pulse was analyzed by finite element modeling. Welding induced defects modifying the skin plate curvature were incorporated. Material degradation in the heat-affected zone was also taken into account. The Budiansky and Roth criterion was employed to predict the collapse load. Various pulse shapes were investigated. The obtained results have shown that the pulse period and profile have severe effects on the buckling strength. For the considered boundary conditions and load pulses up to 56% reduction of the strength was observed in comparison with static buckling

La Géomorphologie De La Plage De Haouzia (Littoral Atlantique Marocain) : Origine Et Mise En Place De Ses Sédiments Actuels

Geomorphological study of the range of Haouzia shows that the latter is more or less homogeneous but influenced by the mouth of the Oued Oum Rbia to the No. Spatio-temporal variation and the heterogeneity and beach profiles are related to the morphology of the beach and the coastal dynamics. Its sediments enrich carbonate because they feed Cretaceous land upstream of the mouth and the Quaternary calcarenites outcropping in the submerged area of the beach. Heavy minerals come from land metamorphic (Boulaouane) and magmatic (Sidi Saïd Maachou) through the Oued Oum Rbia and then taken over by the littoral drift. The weight content of heavy minerals is a good indicator of the direction of the transfer (no SW) of these minerals and sediment. The relative heterogeneity of sediments is favoured by the mouth of the Oued Oum Rbia allowing mixing of continental and marine sediments. It is all the more pronounced to the SW (breaking the waves) and winter (storms). Sediment (coarse and fine) are generally ranked especially in part SW (quiet environment despite the onslaught of the waves) and dune (sorting by the wind). Haouzia beach is under anthropogenic pressure to order, essentially, tourist who is behind the deforestation of the forest of Hameed and therefore the destabilization of the environment (including the beach). Urgent action is needed to protect this beach playing an important socio-economic role in the region

Use of collective expertise as a tool to reinforce food safety management in Africa

The Erasmus+ project (2017-2020) entitled Societal Challenges and Governance of African Universities: the case of ALIments in Morocco, the Democratic Republic of the Congo and Senegal (DAfrAli) seeks to strengthen the governance capacity of African Higher Education Institutions to mobilize their resources in order to respond to major societal challenges in relation to external stakeholders. A work package consisted of organizing three workshops to use Collective Expertise as a tool for the identification of societal risks, in the area of food safety. These three workshops were conducted in Morocco, in Senegal and in Democratic Republic of Congo. The exercise was performed by country academics with the contribution of the European project partners. Collective Expertise gave results that demonstrated that, with a careful and diversified selection of experts, this methodology can have a deep importance to list the food hazards in a country. The results obtained can induce changes in university curricula, showed the social impacts of food safety, unveiled research needs and training needs for different agents in the food sector and above all the impact in food policy in a country. The collective expertise approach of the determination of hazards also permitted to discuss possible organization models for food risk management in the 3 countries