Journal of Materials and Engineering Structures
Not a member yet
316 research outputs found
Sort by
Physico-mechanical characterization and durability of stabilized compressed earth bricks in the region of Timimoun in southwestern Algeria
Full text linkThis study primarily aims to determine the physico-mechanical properties and durability of compressed stabilized earth blocks (CSEBs) made from a mixture of clay and crushed sand that meet the recommendations of the French Standard NF P13-901. The first part of this study consists of first identifying the raw materials. An experimental study was then carried out with three compositions of compressed earth bricks of dimensions (29 × 14 × 9 cm3) which were prepared by adding 4%, 6% and 8% of slaked lime. These bricks were prepared using the manually-operated Auram 3000 Earth Block Press to study the effects of slaked lime addition on the physical and mechanical characteristics as well as on the durability of these bricks. In addition, the durability was studied and analyzed in two different curing modes. The experimental study showed that it is possible to use stabilized compressed earth bricks as a building material for an optimal mixture of clay with 70% of crushed and stabilized sand, with a percentage addition of 4%, 6% and 8% of slaked lime
Structural behavior of beam column joint retrofitted using carbon fiber reinforced polymer
Full text linkBeam column joints are one of the most critical components of reinforced concrete (RC) structures since it is subjected to large forces during severe ground shaking. The present study comprises four exterior beam-column joint specimens having different reinforcement arrangements detailed as per IS 13920: 1993, tested under reversed cyclic loading up_to failure. The test was force-controlled and the specimen was loaded by increasing the load level during each cycle. The load was applied forward cyclic and reverse cyclic and deflection, were measured from every 5kN by using a linear variable digital transducer (LVDT) with the digital arrangement. The deflection was measured at the loading point and at the centre of the beam. Damaged specimens were repaired and retrofitted with carbon fibre reinforced polymer (CFRP) to prevent shear damage and strength deterioration and to achieve a more ductile response. Retrofitted specimens were subjected to similar cyclic loading. Results for displacement were obtained. Hysteresis behaviour of non-retrofitted and retrofitted specimens were studied with respect to ultimate load, maximum displacement, energy dissipation capacity, stiffness degradation and general failure pattern. The comparisons showed that CFRP sheets improved the shear resistance of the joint and increased its energy dissipation capacity. Retrofitting makes the joint so strong that failure is directed towards the beams as it helps the structure in energy dissipation through plastic hinge formation in the beam
Effect of elevated temperature on the hydration heat and mechanical properties of blended cements mortars
Full text linkThis paper presents an experimental investigation for testing the effect of elevated temperature on the hydration heat and mechanical properties of blended cement mortars. Two tests on mortars were made. The first set of mortars is tested of mechanical properties at various temperatures of 20, 35 and 50°C and the second test consists to determine the hydration heat by a semi-adiabatic calorimeter at isothermal temperature of 20, 35 and 50°C during seven days. The new empirical equation has been proposed to estimate the compressive strength depending on the hydration heat for blended cement preserved in constant temperature at early. The results founded from this relationship illustrate a good accuracy with the experimental ones and reflect the best choice to be used to predict the compressive strength depending on the heat of hydration at early age (7 days)
Effet du metakaolin sur les propriétés des mortiers a base de chaux aérienne
Full text linkThe aim of this work is to elaborate lime mortars with a hydraulic character, compatible and similar with the materials of the old building. Different compositions were prepared with a volume: aggregate ratio of 1: 3. In order to improve the fluidity of the mixtures, a superplasticizer -Médaflow 30- has been incorporated. A physico-mechanical characterization of the mortar samples was carried out at different hardening ages. The results obtained showed that the incorporation of metakaolin to mortar samples, even at low dosage, causes considerable variations in the values of the mechanical strengths (flexural and compressive strength) and the physical properties particularly the absorption of water.Le but de ce travail est l’élaboration des mortiers de chaux à caractère hydraulique, compatible et similaire avec les matériaux de l’ancien bâti. Différentes compositions ont été élaborées avec un rapport volumique liant : agrégat de 1 : 3. Des mélanges de mortiers contenant 10 à 50% de métakaolin par substitution à la chaux aérienne ont été préparés. Afin d’améliorer la fluidité des mélanges, un superplastifiant -Médaflow 30- a été incorporé. Une caractérisation physico-mécanique des échantillons de mortiers élaborés a été effectuée à différentes échéances de durcissement. Les résultats obtenus ont montré que l’incorporation du métakaolin aux échantillons de mortiers de chaux, même à faible dosage, provoque des variations considérables dans les valeurs des résistances mécaniques (résistance à la flexion et à la compression) et les propriétés physiques particulièrement l’absorption d’eau.Les mortiers de restauration doivent avoir une composition similaire aux matériaux anciens. Pour assurer cette compatibilité, le liant de chaux aérienne peut être utilisé avec un composant hydraulique actif¶. Le but de ce travail est l’élaboration des mortiers de chaux à caractère hydraulique, compatible avec les matériaux de l’ancien bâti. Différentes compositions ont été élaborées avec un rapport volumique liant: agrégat de 1: 3. Des mélanges de mortiers contenant 10, 20, 30, 40 et 50% de métakaolin par substitution à la chaux aérienne ont été préparés. Afin d’améliorer la fluidité des mélanges, un superplastifiant -Médaflow 30- a été incorporé. Une caractérisation physico-mécanique des échantillons de mortiers élaborés a été effectuée à différentes échéances de durcissement. Les résultats obtenus ont montré que la valeur maximale de la résistance à la flexion et à la compression à 28 jours a été enregistrée par la composition contenant 10% de métakaolin et 2% d’adjuvant. Enfin, on peut conclure que l’incorporation du métakaolin aux échantillons de mortiers de chaux, même à faible dosage, provoque des variations considérables dans les valeurs des résistances mécaniques (résistance à la flexion et à la compression) et les propriétés physiques particulièrement l’absorption d’eau
Editorial
No full textThe year 2020 has been a difficult one for most of us; the coronavirus pandemic has not only affected our health and sanity, but has also had a lasting impact on our lives. Now as we enter the year 2021, the Journal of Materials and Engineering Structures (JMES) would like to wish you all a very happy and prosperous New Year. We appreciate the contributions and support from around the world to develop and improve JMES publications. We have received the complete trust and gratitude of the authors in the research communities; we promise to do the best we can not only to maintain the scientific excellence of JMES, but also to continue work to improve the best publication practices.This special issue of Journal of Materials and Engineering Structures (JMES) includes manuscripts of some of the presentations at the third International Conference on Sustainability in Civil Engineering (ICSCE 2020), held during 26-27 November, 2020 at Hanoi, Vietnam. We believe that all the papers published in this special issue will be an opportunity for researchers to present recent works on Sustainability in Civil Engineering field.
Physico- mechanical and micostructural effects of water/cement ratio on the mortars upon heating
Full text linkThis experimental work studies the effect of the W/C ratio on the mechanical properties of the mortars subjected to the high temperatures. Fours mortars were made according to EN196-1standard. A typical mortar mix with W/C = 0.5 and three others mortars with W/C= 0.3; W/C= 0.4 and W/C= 0.6. They were exposed to a slow heating in a muffle furnace until the target temperature (100, 200,300,400,500,600,700 and 800°C) with a step of 2°C.min-1 and cooling to room temperature took place in the closed and disconnected oven (approximately -0.3°C/min). After thermal stress, mortars with high W/C ratio (0.5 and 0.6) show a decrease in compressive strength much greater than those with low W/C ratio (0.3 and 0.4). The flexural strength of different mortars has a similar shape to those of the compressive strength. The weight loss and water absorption results are consistent with the mechanical behavior. The SEM tests were carried out on samples of unheated control cement and cements heated to 400°, 500° and 800°C. The SEM observations explain the mechanical strength. At upper temperature (800°C), the material is too much damaged and measurements become difficult
A hybrid heuristic optimization algorithm PSOGSA coupled with a hybrid objective function using ECOMAC and frequency in damage detection
Full text linkPresence of damage leads to variation in modal properties of observed structures. The majority of studies use the changes in natural frequencies for damage detection. The reason is that the frequencies are often easily measurable with high accuracy by using reasonable sensors. However, frequencies are more sensitive to environmental effects, such as temperature, in comparison with mode shapes. Besides, defects in symmetric structures can cause the same changes in frequency. In contrast, mode shapes are more sensitive to local damage because they own local information and are independent of symmetric characteristics. These make mode shapes have dominant advantages in detecting nonlinear and multiple damage. ECOMAC is an index derived from mode shapes. It is a fact that these indices are not always possible to detect faults successfully in structures. Therefore, in this paper, a hybrid optimization algorithm, particle swarm optimization – gravitational search algorithm, namely PSOGSA, is used to improve the accuracy of infect detection using a hybrid objective function combined ECOMAC and frequency based on the inverse problem. Numerical studies of a two-span continuous beam, a simply supported truss, and a free-free beam, are utilized to verify the effectiveness and reliability of the proposal. From the obtained results, the proposed approach shows high potential in damage identification for different structures
Nonlinear Vibration Analysis of Thermo-Magneto-Mechanical Piezoelectric Nanobeam Embedded in Multi-Layer Elastic Media based on Nonlocal Elasticity Theory
Full text linkThe present article focuses on the investigations of electromechanical thermo-magnetic coupled effects on the nonlinear vibration of single-walled carbon nanobeam embedded in Winkler, Pasternak, quadratic and cubic nonlinear elastic media for simply supported and clamped boundary conditions are investigated. From the parametric studies, it is shown that the frequency of the nanobeam increases at low temperature but decreases at the high temperatures. The nonlocal parameter decreases the frequencies of the piezoelectric nanobeam. An increase in the quadratic nonlinear elastic medium stiffness causes a decrease in the first mode of the nanobeam with clamped-clamped supports and an increase in all modes of the simply supported nanobeam at both low and high temperature. When the magnetic force, cubic nonlinear elastic medium stiffness, and amplitude increase, there is an increase in all mode frequency of the nanobeam. A decrease in Winkler and Pasternak elastic media constants and increase in the nonlinear parameters of elastic medium results in an increase in the frequency ratio. The frequency ratio increases as the values of the dimensionless nonlocal, quadratic and cubic elastic medium stiffness parameters increase. However, the frequency ratio decreases as the values of the temperature change, magnetic force, Winkler and Pasternak layer stiffness parameters increase. An increase in the temperature change at high temperature reduces the frequency ratio but at low or room temperature, increase in temperature change, increases the frequency ratio of the structure nanotube. This work will greatly benefit in the design and applications of nanobeams in thermal and magnetic environments
A Study of Cr/CrN and Cr/CrN/CrAlN Multilayer Coatings for Permanent Mold Castings of Aluminum Alloys: Wear and Soldering Tendency
Full text linkPhysical vapor deposition (PVD) coatings namely Cr/CrN, Cr/ CrN / CrAlN multilayers (period of μ = 4 with a Cr bonding layer 138 nm thick), have been synthesized on a quenched and tempered X38CrMoV8 steel to test their ability to avoid soldering during casting of aluminum alloys. Wear tests, optical profilemetry observations and demolding stress tests were carried out. Intermetallic compounds were formed and aluminum cast alloy soldering layer was found on surfaces of all tested pins, which were observed and quantified by SEM/EDS. Cr/CrN multilayers have been found to exhibit the best performance among all materials and coatings considered here. The results showed low friction coefficient of Cr/ CrN multilayers and the amounts of intermetallic compounds were lower than those formed on Cr/CrN/CrAlN ones
P-Y Curves for Single Piles in Sand from the Standard Penetration Test (SPT)
Full text linkIt is nowadays recognized the P-Y curves-based methods are the most commonly used methods for the analysis and design of pile foundations under lateral loads. Such methods have the advantage to account for the non-homogeneity of soil properties and the non-linear pile/soil interface behavior as well.The paper aims at presenting a practical method to define a hyperbolic function describing the P-Y curves along the pile whose parameters, namely the initial reaction modulus and the limit lateral soil resistance, are correlated with the SPT N-value. The study is based on an extensive interpretation of several full-scale pile loading tests; the test piles being fully instrumented by strain gauges to derive the bending moment profiles along the pile. Finally, the predictive capability of the proposed method was demonstrated by comparing the predicted load-deflection curves by the software SPULL to the experimental ones obtained from lateral loading tests on simply instrumented full-scale piles