Journal of Materials and Engineering Structures
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Rheological and mechanical performance evaluation of high performance mortar based natural pozzolan
Get PDFThis paper presents an experimental study on the rheological and mechanical properties of High Performance Mortar (HPM) based on natural pozzolan (NP). The specific surface BET of NP was 370 m²/kg used with different contents by weight of cement (5, 10, 15 and 20%). Two (w/b) water-binder ratios (0.35and 0.40) were used, the dosage of Superplasticizer (Sp) was kept constant (0.32 by weight of cement). The experimental results show that rheological properties of HPM increased with increasing NP content when w/b kept constant, but the increasing of (w/b) ratio led to decrease of both yield stress and plastic viscosity of mixtures.The mechanical characteristics were improved with increasing NP content when w/b kept constant, but the increasing of (w/b) ratio led to decrease of both compressive strength. The optimal percentage substitution was 15% of NP, reducing CO2 emission by 20% for each cubic meter of mortar production
Effects of steel corrosion to BFRP Strengthened columns under eccentric loading
Get PDFThe experiment consists of twenty-four mid-scale rectangular RC columns (200x200x800mm) strengthening by BFRP sheets and research variables include: BFRP layer (0, 1, and 3 layers); eccentricity (25mm and 75mm); and 4 levels of steel corrosion. The results reveal that SEL (ratio of ultimate load of strengthened member to that of corresponding controlled member) is direct proportion with steel corrosion while SEV (ratio of ultimate vertical displacement of strengthened member to that of corresponding controlled member) is inverse proportion with steel corrosion; SEL slightly increases with the increase of BFRP layer and eccentricity; but SEV decreases noticeably with the increase of BFRP layer and eccentricity. In addition,the interaction between FRP sheets, stirrups, and longitudinal reinforcement in steel degraded BFRP strengthened columns is very strong.However, column design basing on current design manuals and codes as ACI 440.2R and CNR DT 200R1 has not mentioned this affect. Thus, the load capacity prediction of column being strengthened by BFRP sheets should include levels of steel corrosion for reality, reasonable, and integral of the design
Experimental Study of Physical, Fresh-State and Strength Parameters of Concrete incorporating Wood Waste Ash as a Cementitious Material
Get PDFThe increasing demand and production of cement have caused a huge environmental burden and thus researchers are involved in discovering waste materials having cementitious properties to reduce the production and usage of cement in order to contribute towards the development of a sustainable environment. The present study, therefore, sought to quantify the influence of wood waste ash (WWA) as a cementitious resource on the fresh-state, physical, and strength parameters of concrete. The water absorption, workability, density, compression strength, tensile strength, and flexural strength of concrete was checked at various replacement levels i.e. 0%, 5%, 10%, 15%, and 20% by weight fraction of cement. The density and water absorption were checked on the 28th day of curing while the strength parameters were tested at 7, 28, 56, and 90 days of curing period. The water absorption, density, and workability of concrete reduced with an increase in wood waste ash content while the strength values were increased up to 10% replacement level. Hence, this study suggests that 10% WWA can be used instead of cement for concrete structures
Behavior of monolithic prestressed concrete slab track at highway-railway grade crossings
Get PDFHighway-railway grade crossings are an important part of the transportation system. It allows two types of vehicles to operate in the same areas. Researchers have previously studied the grade crossings, but research on the monolithic prestressed concrete slab (PSCS) track at grade crossings for 1,000mm gauge is limited. At present, there are many types of grade crossing structures that are using in Vietnam. However, these structures still have many disadvantages in the operation process. A new structure type of grade crossing for PSCS is proposed to apply for the 1,000 mm gauge to overcome the main disadvantages of existing structural types. This paper presents test production and experimental measurements to analyze the behavior of PSCS. Test samples of monolithic PSCS were produced in factory. Measurement experiments were conducted in the laboratory. The results of the manufacturing and testing process presented in this paper show that this structure completely meets the criteria of stability and durability under the effect of test loads
The effect of metal corrosion on the structural reliability of the Pre-Engineered steel frame
Get PDFNowadays, Pre-Engineered steel buildings are widely used in the field of the industrial construction. However, design standards often only care about the safety (or reliability) at the start time but not concerned about the deterioration of reliability during used under the metal corrosive of environment. Meanwhile, reliability and durability of steel structure depend heavily on metal corrosion of environmental, this is uncertainty parameters. In this research presents the effect of the safety of Pre-Engineered steel frames considering metal corrosion. The metal corrosion modeling used to propose by M.E. Komp. Reliability of the structure is evaluated using Monte Carlo simulation method and Finite Element Method (FEM). This computer program is written by using the MATLAB programming language. The results numbers are reliability and durability behaviors under corrosion are determined for exposure about from 10 - 50 years. Effects of input parameters are also investigated
Mechanical instability of saturated soils sampled in the Oran coast, Algeria.
Get PDFLa liquéfaction est un risque naturel important associé aux séismes. Certains de ses effets dévastateurs incluent le basculement et le naufrage des bâtiments et des ponts, ainsi que la destruction des pipelines. L'ingénierie géotechnique conventionnelle suppose que la liquéfaction se produit via une pression interstitielle élevée. Nous montrons, en utilisant des simulations et des expériences, un autre mécanisme de liquéfaction dans des sols sableux saturés, sans pression de fluide interstitielle élevée. L’objectif de ce travail, est de suivre et de caractériser le déplacement vertical d'un intrus sur une masse de sol saturée lors d'expériences en laboratoire. A partir des résultats, Il a été démontré que la liquéfaction a un impact direct sur le déplacement vertical de l’intrus. On peut en conclure que le mouvement de l'intrus dépend essentiellement de l'accélération imposée et de la densité relative du sol. La liquéfaction est un risque naturel important associé aux séismes. Certains de ses effets dévastateurs incluent le basculement et le naufrage des bâtiments et des ponts, ainsi que la destruction des pipelines. L'ingénierie géotechnique conventionnelle suppose que la liquéfaction se produit via une pression interstitielle élevée. Nous montrons, en utilisant des simulations et des expériences, un autre mécanisme de liquéfaction dans des sols sableux saturés, sans pression de fluide interstitielle élevée. L’objectif de ce travail, est de suivre et de caractériser le déplacement vertical d'un intrus sur une masse de sol saturée lors d'expériences en laboratoire. A partir des résultats, Il a été démontré que la liquéfaction a un impact direct sur le déplacement vertical de l’intrus. On peut en conclure que le mouvement de l'intrus dépend essentiellement de l'accélération imposée et de la densité relative du sol.Soil liquefaction is a significant natural hazard associated with earthquakes. Some of its devastating effects include tilting and sinking of buildings and bridges, and destruction of pipelines. Conventional geotechnical engineering assumes liquefaction occurs via elevated pore pressure. We show, using simulations and experiments, another mechanism for liquefaction in saturated sandy soils, without high pore fluid pressure. In this work, the objective is to follow and characterize the vertical displacement of an intruder on a saturated mass of soil in laboratory experiments. The liquefaction is shown to have a direct impact on the vertical displacement of intruders. It can be concluded that the movement of the intruder depends essentially on the imposed acceleration and the relative density of soil
Effect of surface treatment of recycled concrete aggregate by cement -silica fume slurry on compressive strength of concrete
Get PDFRecycled concrete aggregate (RCA) used as an alternative to natural aggregate (NA) contains weak adhered mortar. The adhered mortar adversely affects the properties of RCA, and compressive strength of concrete with RCA. Therefore, a treatment method by coating surface of RCA with cement-silica fume slurry (CSS) at concentrations of 20, 40, and 60% was done to evaluate its effects on crushing value and water absorption of RCA, and compressive strength of concrete with treated RCA. The replacements of natural coarse aggregate by RCA for concrete production were 0, 25, and 50% by volume. Compressive strength of the concrete having a constant water-to-cement ratio of 0.35 was tested at ages of 3, 7, 28, and 56 days. Results showed that crushing value and water absorption of the treated RCA were more improved when compared with those of the untreated RCA due to new products formed from cement hydration and pozzolanic reactions on its surface detected by using scanning electron microscope. The surface treatment with CSS at concentration of 60% was the most effective method when compared with that with CSS at concentrations of 20 and 40%. The higher the concentration of CSS, the higher the compressive strength of concrete with the treated RCA. The treatment of RCA led to a significant improvement of compressive strength of the concrete at later ages (i.e., at 28 and 56 days) when compared with the concrete using untreated RCA
Damage detection in structural health monitoring using combination of deep neural networks
Get PDFStructural Health Monitoring is a process of continuous evaluation of infrastructure status. In order to be able to detect the damage status, data collected from sensors have to be processed to identify the difference between the damaged and the undamaged states. In recent years, convolution neural network has been applied to detect the structural damage and with positive results. This paper proposes a new method of damage detection using combination of deep neural networks. The method uses a convolution neural network to extract deep features in time series and Long Short Term Memory network to find a statistically significant correlation of each lagged features in time series data. These two types of features are combined to increase discrimination ability compared to deep features only. Finally, the fully connected layer will be used to classify the time series into normal and damaged states. The accuracy of damaged detection was tested on a benchmark dataset from Los Alamos National Laboratory and the result shows that hybrid features provided a highly accurate damage identification
Research on Design Method of Long-life Asphalt Pavement
Get PDFIn recent years, the problem of early damage of asphalt pavement has been basically solved, and the service performance has been improved, but there are still some deficiencies in design life and service life. This paper investigates the long-life asphalt pavement structure, analyzes the design method of asphalt mixture, and summarizes the pavement design theory and related software. The long-life asphalt pavement with semi-rigid base, flexible base and combined base structure has been designed by four method, including typical load, Per-Road, D50-2006 and D50-2017. Four methods were compared by designing long-life pavements with semi-rigid base and flexible base. The results show that the proposed asphalt pavement structure can meet the requirements of Per-Road, typical load design and D50-2006. However, D50-2017 has higher requirements for the bending and tensile fatigue life of the base layer and requires a thicker base layer. When d50-2017 is used to design flexible base pavement, the fatigue life of asphalt layer should be the main control index, and the fatigue life of sub base course should be the main control index in other pavement de-sign. It remains to be seen whether the proposed highway structure can achieve the design goal of long-life asphalt pavement
Expanding the Use of Fly Ash as an Admixture in Concrete in Vietnam
Get PDFTo bolster the drive for economic and social development in Vietnam, 31 coal-fired power plants were constructed to meet the demand for electricity. According to a survey by the Ministry of Natural Resources and Environment, approximately 20.5 million tons of coal ash will be generated in 2020. A part of the generated coal ash was recycled as landfill; however, the rest lies unused or discarded, causing serious environmental pollution. Since fly ash (FA) forms a major component of coal ash, it is necessary to establish methods for the safe, continuous, and effective use of FA. This study compared the Vietnamese National Standards with the Japanese Industrial Standards from the perspective of using FA as an admixture in concrete. Japanese FA was used in the experiments. Consequently, by using suitable amounts of chemical admixtures and adjusting the ratio of FA as a cement replacement and as a fine aggregate replacement, structural concrete can be manufactured, and the required quality can be assured