Journal of Materials and Engineering Structures
Not a member yet
316 research outputs found
Sort by
Ripening of the AlSi9Cu3ZnMg alloy - mechanical and microstructural characterisation
Full text linkRecovered aluminium has poor mechanical properties, to improve them considerably, three main factors have been considered. The first is to add four very low-density elements to the recovered aluminium, including 9% silicon, 3% copper and some traces of zinc and magnesium less than 1% (≤ 1% Zinc, ≤ 1% Mg), which produces the non-standardized casting alloy AlSi9Cu3ZnMg. Then, in order to obtain a fine microstructure, a gravity die-casting is carried out in the as-cast state noted: F. Finally, to further increase the strength of the F-state and essentially obtain high elasticity stresses, high rigidity modulus with low deformations, the AlSi9Cu3ZnMg alloy composed of 60% scrap and 40% new ingots, is subjected to structural hardening by varying the ripening time for 24 hours in increments of 2 hours, thus giving rise to precipitates of various kinds which impede the dislocations sliding.The results thus obtained show that the cured state for 12 hours (M12h) is a good compromise between good strength and maximum ductility.
Seismic study of shallow circular tunnel in Red River sand (Vietnam)
Full text linkAttention should be paid to tunnels' seismic behaviour since many of them have been damaged by earthquakes. The paper presented a seismic study of a shallow circular tunnel by physical modelling on shaking table test. A small scale tunnel model of the Hanoi pilot metro line's underground segment was placed in the middle of a rigid soil container and buried in Red River sand (Vietnam). The table was vibrated along the soil container's long wall, with a simulated seismic wave created from the 1788 Tolmezzo (Italia) accelerogram. Five testing campaigns were executed, and the model's acceleration data were studied. The uni-directional vibration created by the shaking table caused the three-directional vibration of the physical model. The Fast Fourier Transform (FFT) frequency spectrum analyses were performed. The vibration characteristics of the model (i.e., frequency graph's structure, maximal acceleration, dominant frequency, strong-motion duration) in three orthogonal directions under the artificial earthquake action were compared. The obtained results proved the complicated seismic impacts on a shallow tunnel
Experimental Study of Using Paper Production Industry Waste as Soil Stabilizer for Road Construction in Vietnam
Full text linkThe solution of using organic and inorganic chemical agents to strengthen loading capacity of soil for base, subbase or surface layers in unpaved road pavement has been applied for a long time in the world. In Vietnam, the method has been applied with conventional such as lime, cement, fly ash, or bitumen. Since the years of 2000s, the new soil stabilizers have been introduced to Vietnam. However, the price of the imported admixtures is still the barrier for practical applications. DBS-06 is a domestic lignosulfonate soil stabilizer synthesized from the paper industry waste, which was collected from the HoaBinh paper factory located in Ky Son District, HoaBinh Province. The study program was conducted to investigate the main mechanical properties of the soil specimens stabilized by DBS-06intending for used in road construction. The test results showed that the soil treated with DBS-06 was significantly improved the strength of compression, split tensile and elastic modulus, the three critical indicators representing forload bearing capacity of the material, in both normal and water saturated conditions
Thermo mechanical characteristics of Sisal fibre reinforced composites after treatment with potassium permanganate and stearic acid
Full text linkThis paper presents an experimental study of epoxy and sisal fibre composites with and without potassium permanganate and stearic acid treatment. A compression moulding technique was used to develop the composites. Differential Scanning Calorimetry (DSC), tensile and flexural tests, and scanning electron microscopy were used to investigate the thermal and mechanical behaviour of these composites. SEM images of sisal fibres revealed improvements in the fibre's surface topography further to the surface stearic acid treatment process. X-ray diffraction (XRD) analysis reveals that sisal fibre is crystalline in nature. When sisal fibre was treated with streaic acid, the tensile strength increased to 43.45 MPa. Potassium permanganate-treated fibre reinforced composites demonstrated high potential flexural strength. SEM analysis revealed that stearic acid-treated fibre improved interfacial adhesion between the fibres and matrix
Study on the Use of Construction and Demolition Waste for Road Base or Subbase Pavement Construction in Hanoi
Full text linkReuse or recycling of construction and demolition waste (CDW) has become an inevitable trend in the world. Currently, the amount of CDW generated in Hanoi is estimated at more than 4,000 tons per day, of which only about 30% has been controlled and recycled. The CDW comes from many different sources such as construction, repair, renovation, demolition of houses, residential buildings, public buildings, transportation infrastructure works, etc... The CDW commonly comprises soil, bricks, mortar and concrete, and has been reused in many applications around the world. In Vietnam, there are also some research programs set up for reutilizing the material, however, has not been concretely applied in practice. In order to consider the applicability of CDW in road construction, an experimental program was conducted using CDW as the aggregate for the cement treated grain material base layer in road pavement structure. The weight ratios of cement used in the mixture were 4%, 5%, 6%, 7% and 8%. The test results showed that the main mechanical properties of compressive strength, split tensile strength and elastic modulus of the mixture, increased proportionally with the cement content in the mixture
Effect of shear deformations due to bending and warping on the buckling resistances of thin-walled steel beams
Full text linkThe present paper successfully develops a closed form solution based on a shear deformation theory for elastic lateral-torsional buckling analyses of simply supported thin-walled steel beams. The theory captures the shear effects caused by transverse bending, lateral bending and warping deformations. The closed form solution is successfully validated against 3 dimensional finite element analyses conducted in commercial software. Through various comparisons between the buckling resistances based on a non-shear deformation theory and the buckling resistances based on the present shear deformation theory, the present study finds that (i) the effect of shear deformations on the buckling resistances decreases when the beam span increases, (ii) the effect of shear deformations on the buckling resistance is sensitive with the change of the flange width, and (iii) the effect of shear deformations in general is also influenced by the change of the section depth, and the flange and web thicknesses
Determining factors affecting road users’ acceptability level of waiting time at signalized intersections
Full text linkTraffic lights are installed to reduce crucial conflicts at high-traffic volume intersections. However, waiting time, a critical factor related to the delay and level of service, cannot be avoided at these intersections. In addition, the long waiting time may lead to road users’ impatience. Consequentially, it can motivate them to violate red lights. Therefore, designers should provide an appropriate cycle length and waiting time that meets the road users’ acceptability level. This paper tends to determine factors affecting road users’ acceptability level of waiting time in Hanoi by applying an ordered probit model using questionnaire data. The results demonstrate that the most significant factors include gender, occupation, transportation mode, commuting time/frequency, and traffic law understanding. Specifically, males, people whose occupation is business, who have commuting time in peak hours, who have commuting frequency more than three times per week, and motorcycle riders are sensitive and have less patience with the delay. By contrast, people who understand the traffic law may be more patient to wait at long cycle-length signalized intersection
Model Updating for Large-Scale Railway Bridge Using Grey Wolf Algorithm and Genetic Alghorithms
Full text linkThis paper proposes a novel hybrid algorithm to deal with an inverse problem of a large-scale truss bridge. Grey Wolf Optimization (GWO) Algorithm is a well-known and widely applied metaheuristic algorithm. Nevertheless, GWO has two major drawbacks. First, this algorithm depends crucially on the positions of the leading Wolf. If the position of the leaderis far from the best solution, the obtained results are poor. On the other hand, GWO does not own capacities to improve the quality of new generations if elements are trapped into local minima. To remedy the shortcomings of GWO, we propose a hybrid algorithm combining GWO with Genetic Algorithm (GA), termed HGWO-GA. This proposed method contains two key features (1) based on crossover and mutation capacities, GA is first utilized to generate the high-quality elements (2) after that, the optimization capacity of GWO is employed to seek the optimal solutions. To assess the effectiveness of the proposed approach, a large-scale truss bridge is employed for model updating. The obtained results show that HGWO-GA not only provides a good agreement between numerical and experimental results but also outperforms traditional GWO in terms of accuracy
Study the effect of intermediate and closer stiffener on the behaviour of the cold - formed steel lipped channel section under axial compression
Full text linkCold-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
La Vase Calcinée des Barrages autant qu’addition substituable partiellement au ciment : comportement vis-à-vis de l’Attaque de l’Acide Chloridrique
Full text linkThe dam’s calcined mud in Algeria were proposed by several researchers for its use as an addition partially substitutable for cement, that is beneficial in various fields (technical, economical and environmental), the objective of this work is to evaluate the behavior of this mud towards hydrochloric acid attack, to concretize this objective one control mortar and three mortars mixtures containing modified cement by replacing cement CEMI by the calcined mud with different mass proportion of 10%, 20% and 30%, compressive strength test until the age of 180 days have been elaborated at first time, after that the four mortars were immersed in solutions of hydrochloric acid with two types of concentrations 2% and 5% during 15 weeks (105 days), the results show that the mortars based on mud resist better than the control mortar with tan advantage for 10% replacement with the calcined mud than the other mortars.La vase calcinée des barrages en Algérie a été proposée par plusieurs chercheurs pour son utilisation autant qu’addition substituable partiellement au ciment, ce qui est bénéfique dans de multiples domaines (techniques, économique et environnemental), l’objectif de ce travail vise à évaluer le comportement des mortiers à base de cette vase vis-à-vis l’attaque de l’acide chlorhydrique, pour concrétiser cet objectif une formulation de mortier témoin et trois autres à base de ciment modifié avec des taux de substitution massique de ciment CEMI par la vase calcinée issue des sédiments de dragage du barrage Chorfa de 10%, 20% et 30%, des essais de résistance à la compression jusqu'à l’âge de 180 jours ont été élaborés en premier lieu, ensuite les quatre mortiers ont été immergés dans des solutions d’acide chlorhydrique avec deux concentrations différentes 2% et 5% durant 15 semaines (105 jours), les résultats ont montré que les mortiers à base de vase résistent mieux à l’acide chlorhydrique par rapport au mortier témoin avec un avantage pour la formulation contenant 10% de vase calcinée par rapport aux autres mortiers