Journal of Materials and Engineering Structures
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Contribution to probabilistic modeling of soil geo-mechanical properties for structural reliability analysis of buried pipes and foundations
Get PDFCette présente étude synthétise une approche numérique permettant d’optimiser la conception des systèmes de fondation et des conduites souterraines sur la base de la combinaison entre le comportement élastoplastique du sol et la modélisation probabiliste de ses caractéristiques géo-mécaniques. Ce travail permet aussi de quantifier l’influence de la variabilité spatiale de ces propriétés géo-mécaniques sur la fiabilité mécanique et structurelle des infrastructures ancrées à faible profondeur dans le sol. Les simulations présentées sont basées sur la prise en compte simultanée de l’aspect élastoplastique du sol et la variabilité spatiale de ses propriétés géo-mécaniques. Les résultats montrent que l’analyse probabiliste de variabilité spatiale des propriétés du sol dans la modélisation numérique, présente une influence considérable sur les réponses des infrastructures d’autant plus, si l’ouvrage en question possède une longueur relativement importante.Cette présente étude synthétise une approche numérique permettant d’optimiser la conception des systèmes de fondation et des conduites souterraines sur la base de la combinaison entre le comportement élastoplastique du sol et la modélisation probabiliste de ses caractéristiques géo-mécaniques. Ce travail permet aussi de quantifier l’influence de la variabilité spatiale de ces propriétés géo-mécaniques sur la fiabilité mécanique et structurelle des infrastructures ancrées à faible profondeur dans le sol. Les simulations présentées sont basées sur la prise en compte simultanée de l’aspect élastoplastique du sol et la variabilité spatiale de ses propriétés géo-mécaniques. Les résultats montrent que l’analyse probabiliste de variabilité spatiale des propriétés du sol dans la modélisation numérique, présente une influence considérable sur les réponses des infrastructures d’autant plus, si l’ouvrage en question possède une longueur relativement importante.This present study synthesizes a numerical approach to optimize foundation systems design and underground pipes based on the combination of elastoplastic soil behavior and probabilistic modeling of its geo-mechanical characteristics. Also, this work allows quantifying the effects of soil spatial variability on the mechanical and structural reliability of civil engineering infrastructures anchored at shallow depths in the ground. The illustrated simulations are based on simultaneous combination of the elastoplastic soil behavior and its spatial variability. The obtained results show that the probabilistic analysis of the spatial variability of soil properties into structure numerical modeling has a significant effect on the structural responses of civil engineering infrastructures, mainly if the structure length is relatively significant
Parametric study with FE model of cold-formed plain lipped C-section in shear, and combined bending and shear
Get PDFThe study focuses on the finite element (FE) modelling of cold formed plain lipped C-section in shear, and combined bending and shear, which was developed using ANSYS. Hence, a parametric study on plain C-section was conducted to investigate the applicability of the direct strength method (DSM). In addition, DSM capacity curves were constructed to find out the limitations of DSM. It is found that the DSM equations for nominal shear capacity with tension field action (TFA) gives the capacity that is acceptable when full tension field action is developed while the nominal DSM moment capacity at local buckling outlines conservative results. However, the study also reveals that the DSM nominal shear capacity without tension field action provides lower capacity than the real peak capacity and therefore, it concludes that this method is more conservative
Strengthening of Self-Consolidating High Strength RC Dapped Ends with CFRP Fabrics
Get PDFIn this work, an experimental study has been conducted to investigate the behavior of self-consolidating high strength reinforced concrete dapped end beams upgraded with CFRP composites. A series of 14-specimens have been tested, each of with length of 1500 mm, total depth of 400mm and width of 200mm. Two values of shear slenderness ratio (a/d) namely (1.5 and 1.0) are adopted. Two specimens have been considered as a reference beams (with full Design reinforcement), four were deficiently reinforced in either hanger or the extended disturbed zone, and the other eight beams have been upgraded with a variety of arrangements by CFRP fabric. This work aims to observe the effects of deficiently reinforced disturbed zones on the resistance and overall behavior of such elements. Also, the extent of strength recovery using CFRP sheeting. It is observed that reducing the hanger reinforcements by a half, results in a drop of capacity by (13%) regardless of values of (a/d). Furthermore, it is noticed that adopting the inclined arrangement of CFRP sheets with (450) yielded the best results if compared with other arrangements. An enhancement in failure load was about (23%) for (a/d=1.0)
Preloading of harbor's quay walls to improve marine subsoil capacity
Get PDFPreloading is an improvement technique for compressible soils, and has been applied at DjenDjen port in Jijel province, Algeria, as part of its development and expansion. In addition, this treatment to eliminate the risk of wharf caissons instability. Decent number of research and development works of the preloading process in different countries by several authors have been cited, with the aim of justifying our research and results. The objectives are to understand and apprehend the coastal soil preloading method and its application in terms of the sensitivity of the intervening factors on its achievements, and their effect on the behavior of the soil and the marine structure during and after its implementation. Furthermore, a numerical simulation of the real test of the method of treatment is carried out, by the plaxis 2D code in finite elements, also respecting the actual construction phasing of this structure, in order to compare the calculation results with in-situ measurements to validate the numerical models and to check the stability of the harbor structure. A matrix of consolidation process during pre compression is proposed
Etude expérimentale de la réparation des structures d'aéronefs par collage des patchs à base d’époxy et fibre de verre
Get PDFLes matériaux composites présentent une faiblesse aux chocs et aux impacts causés par différents projectiles (Foreign Object damage, oiseaux, foudres …. etc.). Des études ont été effectuées par plusieurs chercheurs afin de minimiser les conséquences de ces défauts, qui mènent souvent à prendre des solutions de réparations temporaires ou permanente. Ces dernières sont mises sous forme de procédures dans un manuel appelé SRM (Structure Réparation Manuel). La présente étude englobe un travail expérimental réalisé à l’université de Boumerdes en collaboration avec la compagnie aérienne AIR ALGERIE. Elle a pour objectif d'investiguer des cas de réparation des structures d'avions. Ces réparations sont appliquées aux défauts survenus sur les matériaux composites de la structure d'avion de type « Impact Faible Energie » en utilisant la méthode patch de composite à matrice époxy : EPOCASTA50-1, la résine est sans dilution renforcée par des tissus de fibres de verre de même type que celui du fuselage d'avion. Ensuite, l’efficacité de ces réparations est vérifiée par l’étude du comportement en traction classique par application d’une contrainte de l’ordre de 80% de contrainte max, en mode de relaxation. Pour la caractérisation à l'état endommagé et la validation de nos résultats, on a utilisé la méthode de contrôle non destructif CND à base d’ultrasons, cette vérification s’effectue sur des éprouvettes élaborées dans les mêmes conditions que les plaques de réparation fixées sur le fuselage d'avion.The composite materials present weakness to shocks and impact, studies are carried out in order to minimize the consequences of these defects, solutions are adopted for temporary or permanent. solutions are adopted for temporary or permanent repairs. These repairs are applied to the defects present on the composite materials of the "Low Energy Impact" type aircraft structure using the Epoxy matrix composite patch method: EPOCASTA50-1, a non-diluted resin reinforced with glass of the same type as that of the aircraft fuselage. The effectiveness of these repairs is verified using the study of conventional tensile behavior. For the characterization of the damaged state and validation of the results, non-destructive NDT control is carried out on specimens developed under the same conditions as repair plates attached to the fuselage plane.Les matériaux composites présentent une faiblesse aux chocs et aux impacts, des études ont été effectuées par plusieurs chercheurs afin de minimiser les conséquences de ces défauts, qui mènent souvent à des réparations temporaires ou permanentes. La présente étude a pour objectif d'investiguer des cas de réparation des structures d'avions. Ces réparations sont appliquées aux défauts survenus sur les matériaux composites de la structure d'avion de type « Impact Faible Energie » en utilisant la méthode patch de composite à matrice époxy : EPOCASTA50-1, la résine est sans dilution renforcée par des tissus de fibres de verre de même type que celui du fuselage d'avion. L’efficacité de ces réparations est vérifiée par l’étude du comportement en traction classique. Pour la caractérisation à l'état endommagé et la validation des résultats, la méthode de contrôle non destructif CND a été utilisée sur des éprouvettes élaborées dans les mêmes conditions que les plaques de réparation fixées sur le fuselage d'avion
Investigation on the glass fiber reinforced geopolymer concrete made of M-sand
Get PDFThis research work investigates the effect of utilization of glass fibers in geopolymer concrete made of Manufactured sand (M-sand) over its fresh and hardened properties and understand the influence of fibers over reducing the brittleness of the matrix. Geopolymer concrete synthesized in this study is Fly ash- GGBS blend type with optimum molarity cured under heat condition. Fresh property of the fiber reinforced geopolymer concrete was accessed using compaction factor test. Mechanical properties such as compressive strength, split tensile strength, flexural strength, impact strength, ductility factor, first crack toughness, failure crack toughness and ultimate failure toughness were measuredand their results are analyzed and discussed in this work. Later, SEM analysis was carried out over the optimum fiber reinforced geopolymer concrete samples to understand the bonding and the effectiveness of the fiber reinforced geopolymer concrete made of M-sand. Incorporation of glass fiber s proved to be more beneficial and yielded a hybrid concrete with increased strength properties. The performance of fiber s could be measured precisely in increasing the ductility and impact strength. Scanning Electron Microscopy (SEM) analysis showed better bonding between the fiber s and the matrix. This study unleashes an enormous scope for the practical implication of fiber reinforced geopolymer concrete as a building material
Designing of a new seismic base isolation system
Get PDFThe design of a new base isolation system is proposed in this research with the objective that the system does not transmit any force to the structure under horizontal loading. The structure must remain operational and steady. Before investigating the dynamics problem of the base isolation system, the isolator components of the model can be solved analytically using different approaches. In order to calculate the deformation of any element of the isolator due to a compressive vertical load, the analysis focuses on the primary instability region to determine all deformations parameters which can lead to frictions coefficients. This region is located at the interaction contact point between the elements. The design is based on the contact point developed by different approaches. In the present study, the mathematical analysis methods by using formulations can calculate the different dimensions and deformations of the elements of the system and which are verified using ANSYS finite element analysis. After ensuring the adequate dimensions of the different parts of the isolator system from the analysis, the system can be applied on the structure. This technique can reduce significantly the displacements and accelerations at the underground level with a new seismic isolation system, which it is an uncoupled system between the structure and the underground
Replacement of Sand with Bauxite Mining Waste in Concrete Production
Get PDFThe use of natural sand as fine aggregate in concrete is becoming problematic due to scarcity and pressure on mining of the resource. Alternate sources such as the use of industrial waste as replacement of natural sand in concrete are gaining popularity as a sustainable construction material. The aim of this study is to examine the possibility of using bauxite mining waste as a fine aggregate replacement for concrete production. The quantities of sand replaced with bauxite mining waste used are 0, 25, 50, 75 and 100%. Cube, cylinder and beam specimens were molded and cured for 7, 14, 21 and 28 days, and tested for density, compressive strength, tensile splitting strength and flexural strength. The study found that there was a slight increase in density of bauxite mining waste produced concrete over the control as the quantity of bauxite residue increased. The study further revealed a significant increase in compressive, tensile splitting and flexural strengths of the concrete produced with bauxite residue as compared with the control, with an increase between 60.3 and 65.5%. Additionally, a good correlation was established between the bauxite contents and the density of concrete produced with bauxite mining waste, recording R2 values between 0.9749 and 0.9896. The 100% bauxite residue replacement of sand obtained the highest strength properties in the concrete. The study, therefore, concludes that it is feasible to use bauxite mining waste as a fine aggregate replacement in concrete production. It is recommended that further studies should be conducted on the durability and chemical properties of concrete produced with bauxite mining waste as the current study only focused on the strength properties
LTTP Data Analysis: Factors Affecting Pavement Roughness for the State of California
Get PDFThe contributions of pavement structure and features, rehabilitation techniques, climatic conditions, traffic levels, layer materials and properties, pavement distress, and other factors causing changes in pavement smoothness are not well documented. As a result, it becomes difficult to select the appropriate pavement structure, design features and rehabilitation strategies to ensure pavement smoothness. This study focuses on analysing the available LTPP data for asphalt pavements in California by investigating the correlation between the pavement roughness and the effect of pavement temperature, precipitation, fatigue, age of pavement, rutting, and the average annual daily truck traffic. IRI has been identified as the factor characterizing pavement smoothness. Results indicated that when diving pavement sections between three different groups according to the annual precipitation for pavement section in the State of California, the IRIchange can be predicted with 93.5% accuracy for sections with less than 200mm of annual precipitation, 85.9% accuracy for sections with annual precipitation between 200mm and 90mm, and 90.1% for sections with annual precipitation higher than 900mm
Mechanical Behaviour of Corrugated Laminates
Get PDFThe present research work intends to perform a wide set of structural analyses upon corrugated composite laminated panels and based on these analyses, to assess their mechanical response in correspondence to the constructive solutions, which may range from the composite materials selection to the geometrical features and other modelling parameters. To improve the mechanical performance of those panels one may consider enhancing their geometrical characteristics, their corrugation shape configuration and the materials used to build them. In this latter case, when considering materials selection, laminated composites may also constitute an important alternative. In any case it is considered necessary to assess the impact that each of these parameters may have in the static and in the free vibration behaviour of the structures, in a comprehensive and detailed way. To achieve the main objective of this research work, a comprehensive and diversified set of case studies is considered in order to characterize the influence that each of the modelling, material and geometrical parameters and characteristics may have in the mechanical response of a corrugated panel. This study allowed concluding that for the wide set of design parameters considered, the fibre orientation and corrugation parameters are the ones responsible for the majority of the significantly improved performances