Université Mouloud Mammeri de Tizi Ouzou (UMMTO): Research Review of Sciences and Technologies
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Structural Behaviour of Steel Fiber Reinforced Concrete Composite under Blast Loading
Get PDFFibre-reinforced concrete with its higher ductility and enhanced flexural behaviour shows better performance under blast and impact loading than conventional reinforced concrete. During impulsive loadings such as blast and impact, the structural response is to absorb large amounts of energy within a short period. This article proposes the structural responses of steel Fibre reinforced concrete composite under dynamic loading for varying percentages of steel fibres. The experimental results quantitatively indicate improvement in the performance of fiber impregnated concrete. A mathematical correlation based on empirical relations is presented as a basis function for evaluation of Fiber reinforced concrete subjected to blast/ dynamic loading. The experiments on a rectangular specimen of size 400 mm × 400 mm × 50 mm with 125gm ANFO which is equivalent to 100 gm TNT charge placed at different standoff distances, give insight of enhanced FRC behaviour. The article presents failure modes, and quantifies the elastic behaviour of FRC subjected to blast loading
Reinforcement of concrete using Glass Fiber Reinforced Polymer
Get PDFThe use of composite materials such as fiber reinforced polymers in strengthening and repairing of structural elements, particularly those made of reinforced concrete, is widely spreading. Among the fiber reinforced polymers (FRP) used for concrete strengthening, GFRP because they are more ductile and cheaper than carbon fibers and can be considered as an alternative solution to repair and strengthen concrete elements. The GFRP enhance significantly the ductility and strength of concrete by forming perfect adhesive bond between the wrapping material and concrete. Present study mainly emphasizes on effectiveness of external GFRP strengthening for concrete beams and columns. Total five circular concrete columns of 320 mm in height and 160 mm in diameter, and 30 concrete rectangular beams with a section of 40 mmx40 mm and 160 mm in length. Two columns were control and the rest three columns were strengthened with three types of GFRP. For beams, fifteen of them was control and the others were strengthened by GFRP with U-shape. All the test specimens were loaded to fail in axial compression and strain for columns, and under three-point bending for beams. The test results clearly demonstrated that compared with the ordinary concrete, the axial load carrying capacity and flexural strength increase for the reinforced concrete no matter the kind of the GFRP used even if it was in different storage condition
Study the effect of intermediate and closer stiffener on the behaviour of the cold - formed steel lipped channel section under axial compression
Get PDFCold-Formed steel built-up columns are commonly used as compression member in the industrial roof and long span bridge structures to carry larger load. To improve the strength and stiffness of the cold-formed section, the built-up column with additional stiffeners and lacings are used. This paper reports the results of experimental tests conducted on built-up cold-formed columns, composed with the combination of intermediate and closer stiffeners with pin-ended condition under axial compression. Totally twelve columns with or without intermediate and closer stiffeners were tested to failure. The experimental results aim to quantify the effect of cross-section, intermediate and closer stiffener on the overall performance, including strength, strain and failure modes for the built-up column. The Finite element model was developed by ANSYS software and the model is validated with the experimental results. The built-up column strength predicated by recommended design equations of American Iron and Steel Institute (AISI) exhibited good agreement with the ultimate load of built-up columns obtained both by experimental and numerical. Based on this study a recommendation is proposed to DSM for the CFS built -up columns with intermediate and closer stiffeners
Le trauma ou la déconstruction des espaces possibles d’entente entre Soi et l’Autre dans sentiments irradiés de Djamel Mati
Get PDFCet article décrit le processus d’une possibilité de guérison d’un personnage traumatisé par la perte de sa femme lors des essais nucléaires de l’armée française à Reggan. Asphyxié par un passé douloureux, il entend se rendre à Paris pour dire toute la vérité et exprimer les conséquences psychologiques d’une expérience choquante. L’un des mécanismes qui consiste à aspirer à la résilience est l’écriture. C’est par ce procédé qu’il s’imagine obtenir la reconnaissance de la partie belligérante des crimes commis. En attendant, les lettres adressées à son ami resté en Algérie deviennent un espace exutoire où il exprime sa douleur. C’est dans celles-ci qu’il déverse toute sa colère. Lors du colloque, il explique à la partie opposante que le pardon doit émaner du bourreau pour envisager un espace possible d’entente entre Soi et l’Autre. Pour expliquer ce processus, nous nous référons à quelques réflexions de Paul Ricœur, de Roland Barthes, de Patrik Sultan et de Vladimir Jankélévitch
تأثيرالآراء النحوية لبن عطية بقرينة السياق في تفسيره للقران الكريم
No full textتناول هذا البحث قرينة السياق ثيرها وتا في راء آ ال النحوية للمفسر ابن عطية الواردة في تفسيره المحرر الوجيز، وخلص البحث إلى اعتبار السياق من القرائن صيلة ال في البحث اللغوي العربي ك ثرت استعانة المفسرين بها على بيان غوامض معاني يات آ ال وكان لبن عطية ثر تا واضح بهذه القرينةفي مختلف رائه آ ا النحوية
Refinement of an inverse analysis procedure for estimating tensile constitutive law of UHPC
Get PDFAs regard to cementitious composite materials added a certain dosage of fiber, estimation of tensile constitutive law through inverse analysis methods is no longer extraordinary. However, development or improvement to achieve an effective method for estimating such a tensile behavior of fiber reinforced concrete (FRC) or Ultra high-performance concrete (UHPC) is still an interesting topic to researchers. In this respect, the paper presents a development of inverse analysis method developed by Lopez to obtain the stress-strain behavior of UHPC from the four-point bending test. By applying optimization algorithm into the iterative procedure of method, an improvement could be obtained for the inverse analysis with a high degree of automation in calculation. A post-process treatment for inverse analysis results is also proposed to bring a finer agreement between the tensile behavior curve obtained by the inverse analysis and result curve of uniaxial tensile test (UTT). The effectivity of process is shown through a comparison between the result obtained by the proposed method and the result in Lopez’s public paper
Analysis of a Prestressed Sleeper for Railway Turnout under the Effect Static Load with a Unilateral Contact Model and Support Stiffness of Existing Railway Bed of a Railway Section in Vietnam
Get PDFIn the process of analyzing prestressed sleepers for turnout on elastic foundations with large lengths, authors around the world often use the one-stiffness model of Winkler or the two-stiffness model of the Filonenko-Borodich and Pasternak. Railway bed stiffness is assumed to be a constant value from the design to the end of the operating process. In this study, the authors use a one-stiffness model to simulate the interaction between the prestressed sleepers for turnout and the railway bed, which helps to describe the contact and non-contact between the prestressed sleepers of turnout and the railway bed, the phenomenon that the many traditional models do not implement yet. In addition, the railway bed stiffness included in the analysis is obtained by testing at the field of a railway section in operation in Vietnam. The authors use the finite element method and combine it with the Newton iteration method. Accordingly, the analysis results of prestressed sleepers for turnout will be more consistent with actual behavior. We need to check the actual stiffness of the foundation before it is included in the analysis because the actual stiffness of the foundation gives more accurate results during analysis
Study to process abnormal data for GNSS monitoring system of a long-span cable-stayed bridge in Vietnam
Get PDFGlobal Positioning System (GPS) or currently upgraded to Global Navigation Satellite System (GNSS) has been applied in many SHM systems of the super-structures, especially in the long-span bridges. A GNSS system has the ability in monitoring the global deformation of a long-span cable-stayed bridge at the millimeter level of accuracy in real-time. However, the GNSS monitoring dataset acquired from a SHM system includes various noise data such as abnormal data, missing data, and so on. This paper studies de-noising methods to detect and replace the abnormal data of a GPS monitoring dataset acquired from a real cable-stayed bridge in Vietnam. Firstly, a GPS monitoring dataset of an actual long-span cable-stayed bridge was acquired to study processing abnormal data. A scenario of abnormal data was created in a time-series GPS data, and then the Hampel identifier method was applied to detect and replace the abnormal data. The replacing data were then assessed for precision and reliability by using correlation analysis and RMSE criterion. Finally, a long-term GNSS monitoring dataset processed the abnormal data automatically. The results show, that abnormal data in GPS monitoring data can be detected and replaced with high accuracy and reliability
Influence of thermal activation of natural pozzolan on the mechanical behavior of cement pastes
Get PDFThis experimental work focused on the thermal activation of natural pozzolan (NP) from the town of Beni-Saf, in order to improveits reactivity. The present study consists of using natural pozzolan as partial replacement of ordinary Portland cement, with 10 to 40% by weight of cement. Various curing temperatures were used to assess the influence of thermal treatment on the mechanical properties of the pozzolan pastes. For this purpose, three curing modes were chosen, namely the normal curing at the temperature T = (20 ± 2) °C, taken as a reference, the curing at 40 °C, and another one at 60 °C. The experimental results obtained showed that the 40% natural pozzolan paste, which was stored at 40 °C, exhibited much better strengths than those of ordinary cement (CEM I), which was kept at room temperature. This finding leads us to consider that the replacement rate of 40% of NP, stored at the temperature of 40 °C, constitutes the best conditions for preparing an efficient eco-material. Natural pozzolan pastes thermally treated at 60°C gives better mechanical strengths with larger amounts of natural pozzolan
Effect of real fire and cooling systems on concrete properties
Get PDFThe impact of real fire and cooled in different environments (air and water) on ordinary strength concrete enclosing marble mining waste as coarse aggregate is discussed. The compressive strength was investigated. The experimental results reveal that, the use of different cooling regimes had significant effect on the property of concrete mixes. Thermal shock caused by the rapid cooling (immediately immersed in water after fire) showed more loss in compressive strength as compared to that of air cooling. From the experimental results it was observed that, at various temperature and cooling regimes the concrete made with marble aggregate exhibited improved performance as related to control mix. The siliceous aggregate undergo phase transformations after 573°C but the marble aggregate are stable up to 600°C. The type of cooling affects the properties of the concrete it was found from the results of this study