This work presents a numerical analysis of the dynamic behavior of reinforcements of liquefiable loose sand by flexible columns (stone columns) and Mixed Module Columns (CMM). In this study, the numerical simulation was carried out in 3D difference element analysis. Using a Finn model for dynamic Pore-Pressure Generation and the foundation subjected to the variable-amplitude harmonic ground motion of the Boumerdes earthquake (2003). When the height of the rigid part of the CMM has 50% of the column, the behavior of the improvement soil is the same by stone columns under the foundation, also the increase in the rigid part decreases the settlement. Overall, the high recorded accelerations by CMM indicate the largely preservation of the foundation stiffness

It is a challenging task to detect the hidden cracks in multilayer riveted structures in a nondestructive manner. This paper puts forward an eddy current nondestructive method for crack detection in such structures based on the electric conductivity of the rivets. Specifically, an eddy current sensor was designed with a ferrite core coil to evaluate the surface and inner defects of different layers. The magnetic phenomena during the detection process was simulated based on the magnetic potential and the scalar electrical potential, and the magnetic potential vector was solved by finite-element method. The proposed method was compared with the eddy current detection method without considering rivet conductivity through an experiment on a three-layer riveted aluminum structure. The length and position of each defect on each layer were changed in the experiment. The results show that the proposed method achieved better accuracy than the contrastive method, and its sensitivity depends on two issues: the position of the defect relative to the separation of the layers and the length of the defect relative to the length of the rivet head. The research results are of great significance for nondestructive testing of multilayer riveted structures in many fields.

Eddy Current Nondestructive Testing Calibration for Cracks Detection in Aircraft Based Riveted Multilayer Structures

Shrink/Swell soil displacements are the source of additional loadings on expansive soil buried structures such as pipelines. One of the most important factors, which control the swelling values, is the initial soil suction. Using finite element analysis, this paper aims to estimate the effect of the initial soil suction on the loadings provoked by the consequences of a rainfall. An infiltration of 2mm/day intensity and which lasts for 30 days (1 months) on the pipeline buried within the clayey soil, with taking into account the unsaturated behavior of the soil of the Aine-Tine area (Mila, Algeria) is considered. Five initial values of soil suction (from -50kPa to -800kPa) with double increment are used. The obtained results confirm that, the higher the initial soil suction, the higher are the effects, whether on the pipeline internal axial forces or on the soil heave.

Dans ce travail, nous présentons une étude numérique de la convection naturelle dans une enceinte rectangulaire verticale sans ou avec chicane. Les équations qui régissent ce phénomène ont été résolues par une approche numérique, basée sur la méthode des volumes finis en utilisant le code Fluent et le mailleur Gambit. Un premier travail de validation a été mené en comparant notre travail avec ceuxd’autres auteurs. Par la suite, on a fait varier le fluide de travail, la longueur et la position de chicane. L’influence de ces paramètres sur les champs de température, la densité de flux de chaleur et le nombre de Nusselt a été ainsi considérée et les conditions optimales quimaximalisent les transferts de chaleur déterminée

Cette communication présente des analyses numériques d’une excavation, dont l'objectif est d'évaluer les performances de trois modèles de sol constitutifs, à savoir le modèle de MohrCoulomb (modèle MC), le modèle hypoplastique avancé de von Wolffersdorff (modèle HP) et le modèle hypoplastique de von Wolffersdorff amélioré tenant compte de la faible raideur de la déformation (modèle HPS), pour simuler la performance du système de soutènement pour l'excavation de 20 m de profondeur de la fosse M1 adjacente à la station principale «Hauptbahnhof» à Berlin. La fosse M1 a été excavée sous l'eau et soutenue par une paroi moulée ancrée avec une seule rangée de tirants d’ancrages précontraints.Les résultats montrent que le modèle HPS est bien capable de retracer le comportement observé de la paroi moulée dans toutes les étapes de la construction.

In the present study, ultra-thin layer ZnS is inserted in the structure of standard solar cell between CdS buffer layer and CZTS absorber layer to represent the Second Phase (SP) often forms on the top of CZTS. The impact of this layer on the performance of CZTS solar cells is illustrated by the diverse results obtained by simulation using SCAPS-1D. The formation of ZnS on the CZTS surface has harmful effects on the solar cells parameters where the conversion efficiency (η) decreases by 2%. When varying thickness of ZnS SP of 2% to 20% corresponding of the total absorber layer the efficiency decreases by about 0.65%. The ZnS SP can deteriorate the photovoltaic power conversion efficiency from 10.2% to levels of 8.8%, depending on the material buffer layer and the thickness of ZnS SP. Using the ZnS as buffer layer mitigates harmful effects of the ZnS secondary phase forms on the top of CZTS absorber layer.

During the last decade, the construction sector in Algeria has been in constant development with higher demands for urban lands. This has resulted in placing building foundations in closer proximities with potential impact on the bearing capacity and settlements. Moreover, there have been limited investigations on the interference and overlapping effects on the ultimate bearing capacity of closely placed footings. This work explains the numerical investigation of the interference effect of juxtaposed strip footings based on a bilayer granular soil. A numerical model, based on the finite element method, was developed using Plaxis Package. The influence of spacing between foundations, friction angle, Young's modulus and thickness of the first layer on the efficiency factor ξγ were examined. The obtained results show clearly that the efficiency factor depends significantly on the thickness and strength of the first layer.

A numerical simulation is presented to study loose sand improved by stone column (SC) to reduce potential of liquefaction by the drainage effect by this column. The proposed simulation aims to design a unit cell which is consisted of a column and its surrounding soil; it is modeled in 3D under a gravity load and is subjected dynamically to a sinusoidal load. A Finn model is considered for the sand to analyze the evolution of the excess pore water pressure (EPWP), and the column is modeled by the Mohr–Coulomb yield criterion. Parametric studies are included geometrically the effect of the diameter of the stone column and dynamically the effect of dynamic criterions of Finn model and the frequency content of the dynamic load. The numerical simulation of the unit cell gives interesting results in the dynamic behavior of a loose sand reinforced by stone column, and it is suggested for designing the mitigation of liquefaction of loose sand improved under the effect of gravity.