Fadi Hage Chehade

Numerical/analytical methods to evaluate the mechanical behavior of interlock composites

It is seen that 2.5D interlocks are particular reinforcements for high advanced applications (i.e., spatial and aeronautics fields) that are believed to have a high structural potential. This kind of reinforcement entails to consider the composite as a structure because interlocks are built by crossing the warp yarns with the weft (or fill) yarns in the three directions. In this article, a new numerical and analytical model is proposed. To evaluate the mechanical behavior, one may obtain numerically, the anisotropic elastic engineering constants from a finite element model (FEM). This technique of virtual testing consists of modeling the composite at the meso-scale to obtain a macro-scale response with a stress—strain analysis. At the moment, numerical simulations of such materials mainly involve geometrical models and automated tetrahedral meshes that make it difficult to cope with the orthotropic behavior of yarns materials. We thus propose a new meshing methodology to build an elementary volume made of tetrahedra for the isotropic matrix and of mapped hexaedra for the transversely isotropic yarns in order to achieve the FE discretization. A new analytical model is also been proposed, based on a geometrical modeling of the yarns using sinusoidal function and on homogenization at the macrolevel based on both iso-strain and iso-stress assumptions. This model allows the estimation of stiffness matrix of the composite in terms of the properties of its constituents and the geometry of the fabric. Two 2.5D interlock composites from the ‘layer—layer’ family are studied where the nine engineering constants are evaluated. The FEM and the analytical model show a good agreement with each other and with available in-plane Young’s modulus and Poisson’s ratio experimental results.

Evaluation of Longitudinal and Transversal Young’s Moduli for Unidirectional Composite Material with Long Fibers

This work represents a comparative study of available analytical micromechanical models used to evaluate the elastic properties of unidirectional (UD) composite material with long fibers (where the ratio Length/Diameter of the fibers is considered to be infinite). The objective of this work is to find the appropriate model, to be used with different volume fractions of fibers, to determine the micromechanical elastic properties. This study is carried out due to the importance of using the suitable micromechanical model, when modeling bi-dimensional and tridimensional composite materials. The models are divided into two different categories: rheological, and inclusion models. The UD composite material represents a transversely isotropic material composed of two phases: the reinforcement phase and the matrix phase. Isotropic fibers (e.g. glass fibers) or anisotropic fibers (e.g. carbon fibers) represent the reinforcement phase while an isotropic material (e.g. epoxy) represents the matrix phase. In this study only longitudinal and transversal Young’s moduli are discussed. Analytical and Finite element modeling is made for a carbon fiber/epoxy UD composite. The obtained analytical results are compared to those obtained numerically and to the available experimental data. The analytical results are evaluated for different values of fiber volume fraction Vf ranging from 0 to 1.

Interaction Deep Excavation – Adjacent Structure: Numerical Two and Three Dimensional Modeling

Urban development often requires the construction of deep excavations near to buildings or other structures. We have to study complex material structure interactions where we should take into consideration several particularities. In this paper, we perform a numerical modeling with the finite element method, using PLAXIS software, of the interaction deep excavation-diaphragm wall-soil-structure in the case of non linear soil behavior. We focus our study on a comparison of the results given respectively by two and three dimensional modelings. This allows us to give some recommendations concerning the validity of twodimensional study. We perform a parametric study according to the initial loading on the structure and the struts number.

FIELD STUDY OF REAL-TIME WATER QUALITY CONTROL

The objective of a drinking water network is to provide a good quality of water to users. Accidental or intentional contamination can degrade the water quality and consequently threats the consumer’s health. Generally, the water quality is monitored using traditional methods, based on manual sampling, which can take several days. Early warning of water contamination can be achieved using smart technology. This paper presents a field study of the use of this technology in real-time monitoring of the water quality. The field study is conducted at the Campus of the University of Lille in the North of France within the European Project “SmartWater4Europe” (http://www.sw4eu.com). Two sensors are installed in the campus: S::CAN and EventLab which measure several water quality parameters such as TOC (Total Organic Carbon), turbidity, refractive index, etc. This paper presents analysis of these parameters as well as the influence of hydraulic parameters on the water quality. It presents also an event detection system, which is developed using CANARY software. A sensitivity study is presented to determine the appropriate parameters in order to reduce false alarms and to determine the probability of possible event.

Smart technology for water quality control: Feedback about use of water quality sensors

Water distribution networks can be subjected to accidental contamination or malicious attacks which could cause serious perturbations in the water quality. Such critical events threat the human health. Water utilities are concerned by the control of water quality. However, the traditional methods frequently used, are based on laboratory analyses and take several days. To prevent earlier water quality degradation, a real-time monitoring is required. The implementation of the smart technology in the distribution networks ensures a rapid detection of abnormalities. Since the use of this technology is recent, it requires a field application to evaluate its feasibility. This paper presents a field study of the use of this technology in a project conducted at the campus of the University of Lille within the European project “SmartWater4Europe”. The campus is equipped with two types of sensors: S: :CAN and EventLab. S::CAN measures multiple parameters such as turbidity and free chlorine, while EventLab measures the variation of the refractive index. We present in this paper the feedback of these smart devices, the analysis of water quality signals and finally a comparison with laboratory tests.

Smart system for urban sewage: Feedback on the use of smart sensors

This paper presents the use of smart sensors for monitoring both the stormwater and wastewater networks of the Scientific campus of the University of Lille in the North of France. This campus stands for a town of around 25 000 users. For each network, the paper presents the monitoring system, analysis of the recorded data and how this analysis resulted in enhancing our understanding of the network functioning as well as its improvement.

Moving element method: A critical review

The paper proposes a preliminary study that aims to investigate the efficiency of the moving element method MEM which is largely used in the literature when solving high-speed moving load problems. Among other, the train/track interaction problem is considered as the main cause of the environmental perturbations that are less and less tolerated by inhabitants. The target is to find a reliable response of the train/track system that can be used to determine the critical position of measuring sensors (optimization study) which are mounted during experimental campaigns.

Numerical Analysis of Slopes Stability and Shallow Foundations Behavior at Crest under Real Seismic Loading - Reinforcement Effect

The aim of this paper is to analyze the slopes stability under seismic loading using a global numerical dynamic approach. This approach allows important parameters that are generally ignored by traditional engineering methods such as the soil deformability, the dynamic amplification, non linear soil behavior, the spatial and temporal variability of the seismic loading and the reinforcement element… The present study is conducted by using measures recorded during real earthquakes (Turkey, 1999) & (Lebanon, 2008). Elastoplastic soil behavior analysis leads to monitor the evolution of the slope state after an earthquake and to clarify the most probable failure circles. A parametric study according to the reinforcement length, position, inclination and the number of elements has been studied in order to define the optimal reinforcement scheme for slopes under seismic loading. This study contains also the stability analysis of an existing foundation near the slope’s crest. It will focus on the reinforcement in order to give recommendation for the most appropriate scheme that minimize the settlement of the foundation due to earthquake effect.

Relationship between the Compressive and Tensile Strength of Recycled Concrete

Concrete recycling consists of crushing the concrete provided by demolishing the old constructions, and of using the resulted small pieces as aggregates in the new concrete compositions. The resulted aggregates are called recycled aggregates and the new mix of concrete containing a percentage of recycled aggregates is called recycled concrete. Our previous researches have indicated the optimal percentages of recycled aggregates to be used for different cases of recycled concrete related to the original aggregates nature. All results have shown that the concrete compressive strength is significantly reduced when using recycled aggregates. In order to obtain realistic values of compressive strength, some tests have been carried out by adding water-reducer plasticizer and a specified additional quantity of cement. The results have shown that for a limited range of plasticizer percentage, and a fixed value of additional cement, the compressive strength has reached reasonable value. This paper treats of the effect of using recycled aggregates on the tensile strength of concrete, where concrete results from the special composition defined by our previous work. The aim is to determine the relationship between the compressive and tensile strength of recycled concrete.