Calculation of Critical Load for Pure Distortional Buckling of Lipped Channel Columns

This paper presents a method that allows calculating the elastic critical stress for the distortional buckling mode, based on the buckling mode classification of typical lipped channel columns. In our case, Cold-Formed Steel Lipped Channel Columns are subjected to compression. Moreover, in order to consolidate the important findings of this work, a comparative study was carried out to assess the reliability of various distortional buckling models that are provided by different design Standards. It was found that the American and Australian approaches, given in the codes of practice, are closer to the Finite Strip Method than to the European method. An analytical solution was proposed for the determination of the distortional buckling stress on the basis of a statistical method; it corresponds to lipped channel sections with a flange width to web width ratio b/h ranging from 0.1 to 1, and a lip width to web width ratio c/h between 0 and 0.5. After comparison with the results given by the finite strip method for pure distortional buckling, it turned out that the proposed approach provides a reasonable prediction for the elastic distortional buckling stress for lipped channel sections subjected to compression. In fact, this method gives better results than the American approach

Evaluation of the effect of parameters affecting biological and physicochemical phosphate removal from wastewaters in a Multi-Soil-Layering system

 L’évacuation des eaux usées est un problème qui s’aggrave dans certaines zones rurales marocaines. Des rejets de phosphore et d’azote élevés peuvent entraîner l’eutrophisation des eaux réceptrices. Le processus biologique est l’alternative la plus adaptée aux besoins de ces zones, comme le système des filtres imbriqués (FI). Le procédé d’épuration des eaux usées en milieu rural par FI, un système innovant utilisé pour la première fois au Maroc, a été étudié en modélisant les relations entre un ensemble de facteurs environnementaux et le phosphore total éliminé, sur la base de 153 échantillonnages. Trois modèles pilotes de FI,  construites dans trois boîtes en plastique de 36 cm x 30 cm × 65 cm , ont été alimentés en continu par des eaux usées domestiques, avec un taux de charge hydraulique (HLR) de 250, 500 et 1000 l / m2/ jour. Cette étude a pour but d’étudier et de quantifier l’effet des paramètres affectant l’élimination biologique et physico-chimique du phosphore des eaux usées dans ce système, à l’aide de réseaux neuronaux (NN) et d’analyses de régression multiple (ARM). Les résultats montrent l’influence de la charge hydraulique (HLR), du potentiel hydrogène (pH), de la charge de phosphore (PL), du nitrite (NO2--N), de l’oxygène dissous (OD), de la demande biochimique d’oxygène (DBO5) et du nitrate (NO3--N) dans l’élimination du phosphore avec une contribution de 36, 16, 15, 12, 9, 7 et 6 % respectivement. Mots clés: Analyse de régression multiple, filtres imbriqués, les réseaux de neurones, Phosphore.Wastewater disposal is a serious problem in Moroccan rural area. Discharged with high levels of phosphorus and nitrogen can result in eutrophication of receiving waters. Biological processes are the most adapted alternative to the needs of these areas, such as the Multi-Soil-Layering (MSL) system. The process of rural wastewater treatment by MSL, which is an innovative system used for the first time in Morocco, was studied by modelling the relationships between a set of environmental factors and total phosphorus removed, based upon 153 sampling. Three MSL pilot plants, constructed in three 36 cm × 30 cm × 65 cm plastic boxes, were continuously fed with domestic wastewater, with different hydraulic loading rate (HLR) of 250, 500 and 1000 l/m2/day. This study was to investigate and quantify the effect of parameters affecting biological and physico-chemical phosphate removal from wastewaters in this system, using neural networks (NNs) and multiple regression analysis (MRA). The results show the influence of the hydraulic loading rate (HLR), Hydrogen potential (pH), phosphorus load (PL), nitrite (NO2--N), Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD5), and the Nitrate-nitrogen (NO3–-N) in the phosphorus removal with a contribution of 36, 16, 15, 12, 9, 7 and 6 % respectively. Keywords: Multiple regression analysis, multi-soil-layering, neural networks, phosphorus removal

Evaluation of the effect of parameters affecting biological and physicochemical phosphate removal from wastewaters in a Multi-Soil-Layering system

 L’évacuation des eaux usées est un problème qui s’aggrave dans certaines zones rurales marocaines. Des rejets de phosphore et d’azote élevés peuvent entraîner l’eutrophisation des eaux réceptrices. Le processus biologique est l’alternative la plus adaptée aux besoins de ces zones, comme le système des filtres imbriqués (FI). Le procédé d’épuration des eaux usées en milieu rural par FI, un système innovant utilisé pour la première fois au Maroc, a été étudié en modélisant les relations entre un ensemble de facteurs environnementaux et le phosphore total éliminé, sur la base de 153 échantillonnages. Trois modèles pilotes de FI,  construites dans trois boîtes en plastique de 36 cm x 30 cm × 65 cm , ont été alimentés en continu par des eaux usées domestiques, avec un taux de charge hydraulique (HLR) de 250, 500 et 1000 l / m2/ jour. Cette étude a pour but d’étudier et de quantifier l’effet des paramètres affectant l’élimination biologique et physico-chimique du phosphore des eaux usées dans ce système, à l’aide de réseaux neuronaux (NN) et d’analyses de régression multiple (ARM). Les résultats montrent l’influence de la charge hydraulique (HLR), du potentiel hydrogène (pH), de la charge de phosphore (PL), du nitrite (NO2--N), de l’oxygène dissous (OD), de la demande biochimique d’oxygène (DBO5) et du nitrate (NO3--N) dans l’élimination du phosphore avec une contribution de 36, 16, 15, 12, 9, 7 et 6 % respectivement. Mots clés: Analyse de régression multiple, filtres imbriqués, les réseaux de neurones, Phosphore.Wastewater disposal is a serious problem in Moroccan rural area. Discharged with high levels of phosphorus and nitrogen can result in eutrophication of receiving waters. Biological processes are the most adapted alternative to the needs of these areas, such as the Multi-Soil-Layering (MSL) system. The process of rural wastewater treatment by MSL, which is an innovative system used for the first time in Morocco, was studied by modelling the relationships between a set of environmental factors and total phosphorus removed, based upon 153 sampling. Three MSL pilot plants, constructed in three 36 cm × 30 cm × 65 cm plastic boxes, were continuously fed with domestic wastewater, with different hydraulic loading rate (HLR) of 250, 500 and 1000 l/m2/day. This study was to investigate and quantify the effect of parameters affecting biological and physico-chemical phosphate removal from wastewaters in this system, using neural networks (NNs) and multiple regression analysis (MRA). The results show the influence of the hydraulic loading rate (HLR), Hydrogen potential (pH), phosphorus load (PL), nitrite (NO2--N), Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD5), and the Nitrate-nitrogen (NO3–-N) in the phosphorus removal with a contribution of 36, 16, 15, 12, 9, 7 and 6 % respectively. Keywords: Multiple regression analysis, multi-soil-layering, neural networks, phosphorus removal

Effets de l’endommagement sur le comportement Vibratoire des matériaux sandwichs endommagés

Les effets d’un endommagement progressif sur le comportement vibratoire d’un matériau sandwich sont analysés en terme de fréquence et d’amortissement. L’analyse expérimentale et par éléments finis est menée dans le cas de flexion de poutres. Les caractéristiques dynamiques obtenues expérimentalement et numériquement sont en bon accord et permettent de proposer des indicateurs d’endommagement fiables et sensibles

The impact of urban form on urban heat island variation in a Mediterranean cities

Učinak urbanih toplinskih otoka (UTO) povećao se s urbanizacijom i klimatskim promjenama, što je dovelo do još veće izraženosti nepovoljnih učinaka toga problema, osobito u gradovima sa sušnom klimom. Cilj ove studije jest razumjeti utjecaj urbanih oblika na stvaranje urbanih toplinskih otoka istraživanjem sedam lokacija u sklopu studije slučaja u sjevernome Alžiru, odnosno u gradu Mostaganemu koji se nalazi na obali Mediterana. Za prikupljanje toplinskih podataka s odabranih lokacija (od S1 do S7) korištena je meteorološka postaja uz infracrveni termometar. Situacija S1 modelirana je i simulirana softverom ENVI-MET za procjenu učinka UTO-a na otvorenom prostoru omeđenom građevinama. Zatim su simulacijski podaci potvrđeni podacima prikupljenima u stvarnom vremenu na konkretnoj lokaciji. Nakon toga evidentirano je i modelirano ukupno sedam konfiguracija urbanih oblika na istome mjestu (S1) te je potom kreirana simulacija koja odražava njihove pojedinačne utjecaje. Rezultati simulacije uspoređeni su s obzirom na temperaturu zraka, brzinu vjetra i temperaturu površine tla te je utjecaj različitih urbanih oblika pridonio učinku UTO-a na tome omeđenom području. Uočeno je to da su poluzatvorene konfiguracije urbanih oblika koje su bile zaštićene od izravnoga Sunčeva zračenja zabilježile najniže temperature zraka i tla, dok je temperaturna razlika na lokaciji u najtoplijim satima dana bila veća za 2°C.The Urban Heat Island (UHI) effect has increased with the increase in urbanisation and climate change, especially in cities with arid climates. This study aims to understand the influence of urban forms on creating UHIs by assessing seven sites in a case study in Mostaganem city, which is located on the Mediterranean coast in northern Algeria. A weather station and an infrared thermometer were used to collect the thermal data from the selected sites (S1 to S7). Site S1 was modelled and simulated using ENVI-met software to evaluate the UHI effect on the open area bounded by the surrounding buildings. The simulation data was then validated by the real time data collected from the actual site. Thereafter, seven common urban form configurations were identified and modelled around the same site (S1), and simulated for their individual impacts, one by one. The simulation results were compared in terms of air temperature, wind speed, and ground surface temperature, not to mention that the influence of the different urban forms contributed to the UHI effect in the bounded area. Semi-enclosed configurations of the urban forms that were protected from direct solar radiation recorded the lowest air and ground temperatures, while the difference between temperatures on the site rose to 2 °C in the hottest hours of the day

Analyse expérimentale et par éléments finis de la réponse dynamique d’une structure en matériaux composites

Nous avons étudié les réponses en fréquence de trois structures en matériaux composites: stratifiés, stratifiés avec couche viscoélastique et sandwich. Les propriétés des matériaux en fonction de la fréquence ont été identifiées en confrontant l’analyse expérimentale et calcul par éléments finis. La modélisation a été menée en tenant compte de la dépendance en fréquence des propriétés mécaniques des matériaux. Un bon accord entre les résultats expérimentaux et de la modélisation a été obtenu

Etude expérimentale et modélisation du comportement dynamique des composites stratifiés et sandwichs

Ce travail présente une analyse du comportement dynamique des composites stratifiés et sandwichs. Une étude détaillée est d'abord menée pour caractériser le comportement mécanique en statique et en fatigue de ces matériaux. Ensuite une analyse approfondie est mise en place pour identifier l'amortissement et les propriétés dynamiques des différents matériauX. Les résultats expérimentaux sont comparés à ceux obtenus par une modélisation combinée à une analyse par éléments finis basée sur la théorie des stratifiés avec cisaillement transverse. Une étude paramétrique est mene e sur les matériaux sandwichs, permettant de mettre en évidence comment il est possible d'optimiser l'amortissement de ces matériaux en faisant varier divers paramètres. Enfin la modélisation est appliquée à l'analyse de l'amortissement d'une structure de géométrie simple constituée de différents matériaux. Les réponses en fréquence obtenues à partir de la modélisation sont comparées à celles obtenu par l'analyse expérimentale.The object of this work is to investigate the dynamic behaviour of the laminate and sandwich composites. First, an extensive study is implemented so as to derive the mechanical behaviour in static and fatigue tests of these materials. Experimental investigation of the damping of the different materials is developed using beam test specimens and an impulse technique. Modelling of the damping of a structure constituted of these different materials is implemented considering ftnite element analysis based on the laminate theory taking into account the transverse shear effects. Modelling applied to the experimental results allows us to derive the damping parameters of the materials and constituents. Next, modelling is applied to the analysis of the damping of a simple shape structure constituted of the different materials. The results deduced from modelling are compared with the experimental results for the frequency response of the structure.LE MANS-BU Sciences (721812109) / SudocSudocFranceF

Study of Local and Distortional Stability of Thin-Walled Structures

Thin-walled structures have an increasingly large and growing field of application in the engineering sector, the goal behind using this type of structure is efficiency in terms of resistance and cost, however the stability of its components (the thin walls) remains the first aspect of the behavior, and a primordial factor in the design process. The hot rolled sections are known by a consequent post-buckling reserve, cold-formed steel sections which are thin-walled elements also benefit, in this case, it seems essential to take into account the favorable effects of this reserve in to the verification procedure of the resistance with respect to the three modes of failures of this type of structure. The design method that takes into account this reserve of resistance is inevitably the effective width method. The direct strength method has been developed to improve the speed and efficiency of the design of thin-walled profiles. The latter mainly uses the buckling loads (for Local, Distortional and Global mode) obtained from a numerical analysis and the resistance curves calibrated experimentally to predict the ultimate load of the profile. Among those, the behavior of a set of Cshaped profiles (highly industrialized) is studied, this type of section is assumed to be very prone to modes of local and distortional instability. The outcome of this investigation revealed very relevant conclusions both scientifically and practically

Study of Local and Distortional Stability of Thin-Walled Structures

Thin-walled structures have an increasingly large and growing field of application in the engineering sector, the goal behind using this type of structure is efficiency in terms of resistance and cost, however the stability of its components (the thin walls) remains the first aspect of the behavior, and a primordial factor in the design process. The hot rolled sections are known by a consequent post-buckling reserve, cold-formed steel sections which are thin-walled elements also benefit, in this case, it seems essential to take into account the favorable effects of this reserve in to the verification procedure of the resistance with respect to the three modes of failures of this type of structure. The design method that takes into account this reserve of resistance is inevitably the effective width method. The direct strength method has been developed to improve the speed and efficiency of the design of thin-walled profiles. The latter mainly uses the buckling loads (for Local, Distortional and Global mode) obtained from a numerical analysis and the resistance curves calibrated experimentally to predict the ultimate load of the profile. Among those, the behavior of a set of Cshaped profiles (highly industrialized) is studied, this type of section is assumed to be very prone to modes of local and distortional instability. The outcome of this investigation revealed very relevant conclusions both scientifically and practically

Effect of Fatigue Testing and Aquatic Environment on the Tensile Properties of Glass and Kevlar Fibers Reinforced Epoxy Composites

International audienceThis paper presents the experimental results of the influence of water ageing after mechanical fatigue on glassfiber composites, compared with Kevlar-fiber composites. The tested specimens were subjected to fatigue during various numbers of cycles (100 to 50000). After that, they were immersed into tap water and simulated seawater for different periods (4, 20 and 40 days). Next, the tensile tests were made on the unaged and aged samples in order to determine the evolution of the strength and stiffness under local interactions of the water absorption and fatigue.The obtained results showed that tensile characteristics were clearly affected by the immersion treatment and fatigue loading. In fact, the residual stiffness and residual strength decreased when the immersion time and cycle number of fatigue increased, indicating that the studied composites have experienced some forms of mechanical damage