Journal of Materials and Engineering Structures
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Material Design for Concrete Using Low-Quality Recycled Aggregate
Get PDFSince the 19th century, concrete has been a fundamental construction material. It is the most popular manmade material in the world because of its more reliable workability, greater durability, and lower cost compared with other construction materials. However, because of its durability, demolishing or renovating old structures generates a huge amount of concrete waste, which, if not properly treated or reused, can adversely affect the environment. Therefore, the development of concrete-recycling technology is a necessary and pressing requirement for all the countries. This study concerns material design with concrete using low-quality recycled aggregates prepared via an aggregate replacement method. To evaluate the quality of the aggregates in recycled aggregate concrete, experiments were conducted using specimen groups characterized by various mix proportions. Accordingly, when low-quality recycled aggregate is used, by employing the relative quality index method for material design, the manufacturing of recycled aggregate concrete with required performance could be achieved
Upgrading of Deficient Disturbed Regions in Precast RC beams with Near Surface Mounted (NSM) Steel Bars
Get PDFAn experimental study has been conducted to explore the response of self-compacting RC drop in- beams retrofitted with NSM steel bars under short-term static loading. Eleven specimens have been tested in this program, each of (200x400x1600 mm) dimensions with two values of (a/d), namely (1.0 and 1.5). Two of these beams have been considered as reference beams (efficiently reinforced). Three beams with reduced reinforcement, two with deficient main nib steel, while the third with reduced steel in hanger. The rest have been upgraded with different arrangements to retire the expected drop in strength. It was found that reduction of nib reinforcements to the half, results in decreasing load failure of about (11% 5%) for (a/d) values of (1 and 1.5) respectively. Also, it is observed that retrofitting the nib region with horizontal NSM steel bars led to increase the failure load capacity by about (28.7%) for (a/d) =1. While, the enhancement in strength for specimen with (a/d) =1.5 was about (24%). The increase in the strength capacity for upgraded hanger regions vertical and inclined bars for a/d (1) was about (21.4% and 14.2%) respectively
Comparative study between the effect of carbon "C" and the effect of nitrogen "N" on the hardness and corrosion resistance of pure titanium "Ti"
Get PDFDans ce travail, nous avons étudié l’effet du carbone et de l’azote sur la dureté et les propriétés électrochimiques de titane Ti6Al4V. Des couches minces de nitrure de titane (TiN) et de carbure de titane (TiC) ont été déposé par pulvérisation cathodique radio fréquence (RF) afin d’investiguer leurs résistances à la corrosion par rapport au titane pure. Des couches un peu plus épaisses ont été déposé par la même méthode et dans les mêmes conditions sont destinées aux tests de la microdureté Vickers. Nos échantillons ont été caractérisés par les techniques DRX, Raman et FTIR. Les tests anti corrosion dans la solution biologique simulée montrent que le TiN est le dépôt le plus résistant à la corrosion avec un courant de corrosion Icorr, TiN = 0.184 μA/cm², tandis que les essais de la dureté révèlent que le TiC est le plus dur avec une dureté HV = 426 kgf.mm-2.Dans ce travail, nous avons étudié l’effet du carbone et de l’azote sur la dureté et les propriétés électrochimiques de titane Ti6Al4V. Des couches minces de nitrure de titane (TiN) et de carbure de titane (TiC) ont été déposé par pulvérisation cathodique radio fréquence (RF) afin d’investiguer leurs résistances à la corrosion par rapport au titane pure. Des couches un peu plus épaisses ont été déposé par la même méthode et dans les mêmes conditions sont destinées aux tests de la microdureté Vickers. Nos échantillons ont été caractérisés par les techniques DRX, Raman et FTIR. Les tests anti corrosion dans la solution biologique simulée montrent que le TiN est le dépôt le plus résistant à la corrosion avec un courant de corrosion Icorr, TiN = 0.184 μA/cm², tandis que les essais de la dureté révèlent que le TiC est le plus dur avec une dureté HV = 426 kgf.mm-2.In this work, we investigated the effect of carbon and nitrogen on the hardness and electrochemical properties of titanium Ti6Al4V. Thin films of titanium nitride (TiN) and titanium carbide (TiC) were deposited by radio frequency (RF) sputtering to investigate their corrosion resistance compared to pure titanium. Slightly thicker layers were deposited by the same method and under the same conditions are intended for the Vickers microhardness tests. Our samples were characterized by DRX, Raman and FTIR techniques. Anti-corrosion tests in the simulated biological fluid show that TiN is the most corrosion resistant deposit with a corrosion current density Icorr, TiN = 0.184 μA/cm², while hardness tests reveal that TiC is the most hard with a hardness HV = 426 kgf.mm-2
Pervious concrete: a state-of-the-art review
Get PDFPervious concrete is a special type of concrete, achieved by either minimizing or excluding the sand from the normal concrete mix. In recent years, the practice of pervious concrete as a pavement material in small volume roads and parking lots has added much significance due to its constructive and eco-friendly characteristics. It is used to lessen the problem of local flooding in municipal areas and is significant tool to lessen the burden of municipal drainage system. This paper reviews the various properties, factors controlling the performance of pervious concrete, clogging mechanism and de-clogging techniques and lastly the factors that enhance the life span and properties of durability of pervious concrete are discussed. Durability tests of pervious concrete like, permeability, surface abrasion, freeze thaw and thermal conductivity are discussed. Furthermore, controlling factors such as water to cement ratio, aggregates, admixtures, compaction and curing are also discussed in this review. There occurs an expensive range for future research to recognize the better material that will make it a favorable ecological roadway material for high speed and high-volume traffic in coming times
Effect of Environment with Heavy Industrial Pollution on the Selection of Concrete Mix for Building Structures
Get PDFThis study proposes durable concrete mix design suitable for use in superstructures of an industrial plant of a cement company located in an area marked by heavy industrial pollution. Concentration of pollutants in the environment was recorded by undertaking ambient air quality monitoring along with an assessment of corrosivity of soil and ground water present at the site. Type of reinforcement, concreting procedures and protection methods were determined for reinforced concrete that was intended to be used in conjunction with steel structures. Experimental results indicated that soil and groundwater constituted no risk for the substructure. However, air was highly polluted and deemed to be severely corrosive due to the presence of chloride and sulfate salts, SO2 and CO2 in concentrations recorded several times higher than at a comparable industrial area. A concrete mix design suitable for observed conditions was recommended. Additionally, it was suggested that concrete reinforced with black steel bars should be completely coated while that using FBE coated steel bars should be coated up to a height of 1.5m from the grade level for protection against ingress of salt and water
Experimental Behavior and Analysis of Hybrid Low-High Strength Reinforced Concrete Columns
Get PDFIn this paper, the behavior of hybrid short columns made from low strength reinforced concrete core and an outer skin made from high strength concrete was studied. For this purpose, laboratory tests were carried out on ten small-scale column specimens. For bonding, the outer skin portion to the main column epoxy resin was used. Results revealed that bonding low strength concrete core with high strength outer skin was successful and able to produce a hybrid section. For the same section area, load capacity increased by 28% to 80% depending on the compressive strength of the provided outer skin, for concentrically loaded columns. In general, the behavior of eccentrically loaded hybrid specimens was good, indicating that the process of making hybrid columns according to the technique presented in this paper is successful and can be used in practice
Experimental Research on Properties of Polymer Concrete Used for Repairing Portland Cement Concrete Pavement of Airport
Get PDFPolymer concrete (PC) is a popular construction material used for repair, thin over-lays for floors and bridge decks, and other specialized fields such as precast components, machine construction. The material has many desirable properties such as fast curing, high compressive and flexural strength, high bonding to substrate, resistance to chemical agents. This study focuses on investigation properties of polymer concrete applying in repairing works of Portland cement concrete (PCC) pavement of airport by experiments. The research results in both laboratory and field tests showed that the material has advanced properties and meet very well the requirements from practice. This result has been proposed to apply polymer concrete for treatment of surface distresses of Portland cement concrete pavement of airports in Vietnam
Reliability based robust design optimization based on sensitivity and elasticity factors analysis
Get PDFIn this paper, a Reliability Based Robust Design Optimization (RBRDO) based on sensitivity and elasticity factors analysis is presented. In the first step, a reliability assessment is performed using the First-and Second Order Reliability Method (FORM)/ (SORM), and Monte Carlo Simulation. Furthermore, FORM method is used for reliability elasticity factors assessment, which can be carried out to determine the most influential parameters, these factors can be help to reduce the size of design variables vector in RBRDO process. The main objective of the RBRDO is to improve both reliability and design of a cylindrical gear pair under uncertainties. This approach is achieved by integration of two objectives which minimize the variance and mean values of performance function. To solve this problem a decoupled approach of Sequential Optimization and Reliability Assessment (SORA) method is implemented. The results obtained shown that a desired reliability with a robust design is progressively achieved
Contribution à la Proposition d’une Nouvelle Approche de Calcul Sismique des Structures en Interaction avec le Sol (N2-ISS)
Get PDFThe purpose of this article is to contribute to the study of the seismic behavior of structures interacting with the ground and to offer new tools for the treatment of relevant problems, oriented towards the new seismic design philosophy of structures: the design performance-based design. The issue is part of the proposal for simplified models to address a complicated problem such as soil-structure interaction (ISS). The nonlinear behavior of the structure is determined by a capacitive approach based on the seismic performance such as the N2 method proposed by Peter Fajfar. In its original version, this method considers that the structure is fixed at its base, neglecting the ISS. Our contribution will be to make some modifications to this approach to introduce the effect of the soil on the nonlinear response.The purpose of this article is to contribute to the study of the seismic behavior of structures interacting with the ground and to offer new tools for the treatment of relevant problems, oriented towards the new seismic design philosophy of structures: the design performance-based design. The issue is part of the proposal for simplified models to address a complicated problem such as soil-structure interaction (ISS). The nonlinear behavior of the structure is determined by a capacitive approach based on the seismic performance such as the N2 method proposed by Peter Fajfar. In its original version, this method considers that the structure is fixed at its base, neglecting the ISS. Our contribution will be to make some modifications to this approach to introduce the effect of the soil on the nonlinear responseL’objectif de cet article est de contribuer à l’étude du comportement sismique des structures en interaction avec le sol et d’offrir de nouveaux outils pour le traitement de problèmes pertinents, orientés vers la nouvelle philosophie de conception parasismique des structures : la conception basée sur la performance (performance-based design). La problématique s’inscrit dans le cadre de proposition de modèles simplifiés afin d’aborder un problème compliqué tel que l’interaction sol-structure (ISS). Le comportement non linéaire de la structure est déterminé par une approche capacitive basée sur la performance sismique telle que la méthode N2 proposée par P. Fajfar. Dans sa version originale, cette méthode considère que la structure est encastrée à sa base, négligeant ainsi l’ISS. Notre contribution sera d’apporter quelques modifications à cette approche pour introduire l’effet du sol sur la réponse non linéaire
Comparison between DRF for displacement and acceleration spectra with uncertain damping for EC8
Get PDFThe damping force exerted by a structure during an earthquake differs significantly from that specified in the design process. This introduces uncertainties in the design process of structures under earthquake loads. Accordingly, it is desirable to consider not only the effect of randomness of the seismic load but also the uncertainties in the structural parameters. This paper investigates the effect of uncertainties inherent in the damping ratio on the use of damping reduction factor (DRF) for the evaluation of high damping response spectra for linear structures with viscous damping. The DRFs are evaluated from both acceleration and displacement response spectra. Effects of period of vibration, level of damping ratio, soil class and uncertainties level of damping on the DRFs are evaluated and discussed. A numerical analysis implies that the maximum relative error estimated between the deterministic DRF and the DRF considering uncertainties in damping is about 14%. This implies that the damping uncertainty with = 20% leads to an error in DRF of Cv=13 % which is a significant error in estimating the structure response