Journal of Materials and Engineering Structures
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316 research outputs found
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Analysis of the inelastic lateral - torsional buckling resistances of steel truss members with global and local imperfections
Full text linkThe local and global imperfections of I-shaped steel beams are known to significantly impact the load-carrying capacity of the structure. This is particularly critical for structures subjected to heavy loads, where these factors must be meticulously controlled to prevent potential failures. Therefore, the objective of this project is to describe a numerical analysis that was conducted to evaluate the influence that initial global and local flaws have on the inelastic buckling resistances of steel truss members that are used in steel bridges. These numerical studies are based on Abaqus, and they have been validated quite well against the data that are now available. After that, the numerical models are utilized in order to assess the inelastic buckling resistances of the system, taking into consideration four distinct sorts of initial global and local imperfections which are feasible. The numerical results are compared to the standard evaluations, which are also examined and evaluated. In addition, parametric investigations of the impact of the thicknesses of the web and flange on the inelastic buckling resistances are carried out as part of the current research. The strengthening techniques assessed in this research can serve as a foundation for engineers to implement in actual steel beam structures
Behaviour of arched hybrid sustainable precast deep beams including green Concrete
Full text linkIn recent years, the use of waste construction materials in the production of sustainable and cost-effective structural members such as deep beams has become more interesting. In the present work, a new sustainable model of a hybrid deep beam has been proposed and compared with the Horizontally hybrid model. Nine specimens have been tested experimentally under mid-span static loading up to failure. The arch region of the proposed model is made of steel fiber concrete (SFC), while other regions are made of concrete with recycled coarse aggregate (RCA) with three ratios of replacement (0%, 50%, and 100%). The specimens are grouped in three sets, each with three specimens representing the conventional model, the proposed model (ARC1), and the modified model (ARC2). The response has been studied in terms of cracking load, failure load, crack width, cracking pattern, and toughness. Results revealed that the proposed model ARC1 enhanced capacity by 6.7%, 6.8%, and 9.4% compared to the conventional hybrid model for the three value of RCA. While for the model ARC2 capacity improved by 13.5%, 19.6%, and 19.1. Regarding the toughness, enhancements of 12.5%, 18.7%, and 32.9% were obtained for the model ARC1 compared to the traditional hybrid model. While for model ARC2, it is enhanced by 25.2%, 51.1%, and 62.1% respectively. The proposed hybrid models may contribute in reduction the cost of construction and reduce the environmental effects of the waste of construction materials
Fresh and Mechanical Properties of Lightweight Aggregate Concrete with Scrap Steel Fiber Reinforcement and Bagasse Ash
Full text linkA sustainable concrete solution was developed by partially replacing aggregates and cement with lightweight plastic aggregates (LWPA) and bagasse ash, respectively. Three types of mixes were studied: (i) concrete with 10-30% cement replaced by bagasse ash (BA), (ii) Bagasse ash concrete mix with scrap steel fiber, and (iii) Bagasse ash concrete with scrap fiber and 10-50% lightweight aggregate. The addition of bagasse ash positively influenced the fresh properties of concrete. However, workability decreased by 56% with the incorporation of scrap fibers and lightweight aggregate compared to the control mix. Slump values reduced in concrete mixes containing plastic aggregate (PA) due to mortar accumulation in voids within the hollow aggregate, significantly diminishing workability. The density of concrete decreased with bagasse ash and lightweight aggregate inclusion, aiding in reducing structural dead weight. However, the strength decreased notably with 30% replacement using hollow lightweight plastic aggregate. Voids in concrete specimens increased with LWPA percentage. Observations from fresh and hardened concrete tests suggest that plastic aggregate, bagasse ash, and scrap fiber can effectively replace up to 20% of gravel aggregate
Study on the Stiffness of Rail Support for Some Lines of Urban Railway in Vietnam
Full text linkTrack stiffness significantly affects how forces are transferred from the train to the substructure. Vietnam is currently in the process of constructing and operating three urban railway lines (URL). This research focuses on analyzing the stiffness of the rail support system and examining the forces exerted on these supports in relation to their stiffness properties. To achieve this, the study employs analytical methods, finite element method (FEM), and simulation techniques for structural analysis. The results reveal that the forces transmitted to the rail bearings are 26,117 N, 24,332 N, and 24,570 N, corresponding to axle loads of 16 tons/axle, 14 tons/axle, and 14.5 tons/axle, respectively. Furthermore, the reduction ratios of train loads transferred to the substructure are 67.35%, 65.24%, and 66.11%. These values are associated with bearing stiffness values of 23.1x106 N/mm, 30.8x106 N/mm, and 27.5x106 N/mm, respectively. Proper determination of rail support stiffness is crucial for efficient railway operations and maintenance. Accurate stiffness values ensure better load distribution across the infrastructure. This prevents excessive stress on specific structural components. In addition, optimizing stiffness helps minimize maintenance costs and prolongs infrastructure lifespan
Application of recycled aggregate in sprayed mortar and shotcrete
Full text linkNew uses for concrete waste should be investigated to counter the expected increase in its production due to upcoming construction projects. The developed method should be a high-value recycling method that improves resource diversion and environmental preservation. This study was aimed at expanding concrete waste recycling by investigating the feasibility of using low-quality recycled aggregate from demolished office buildings for sprayed mortar and shotcrete, intended for slope protection and cross-section repair, respectively. Additionally, demolished wood chips were incorporated into the sprayed mortar. The study explored mix proportion base mortar and concrete before spraying (prior to adding the quick-setting admixture); confirmed application conditions; and evaluated fresh properties, spraying conditions, and various performances, including compressive strength, static modulus of elasticity, and accelerated carbonation depth using core specimens. Results confirmed that, with appropriate design considerations for performance degradation, low-quality recycled aggregate could meet the required performance criteria as materials for sprayed mortar and/or shotcrete
Predicting shear capacity of Recycled Aggregate Concrete beams using Artificial Neural Network
Full text linkThis study investigates the application of an Artificial Neural Network (ANNs) utilizing a Multi-Layer Perceptron (MLP) architecture to predict the shear capacity of Recycled Aggregate Concrete (RAC) beams. The ANNs model was trained using the Levenberg-Marquardt algorithm with a comprehensive dataset comprising 232 experimental shear tests, reflecting a wide range of variables relevant to RAC beam performance. The model's predictions were compared to those derived from established design standards, including ACI 318-14 and Eurocode 2, to evaluate its performance. Various statistical criteria were employed to assess the model’s accuracy and reliability in predicting shear strength, including metrics that measure goodness of fit, error rates, and predictive consistency. This research highlights the growing potential of machine learning techniques in civil engineering, particularly for enhancing the precision of shear strength predictions for RAC beams. The findings suggest that the ANN model offers a valuable alternative to traditional prediction methods, with the potential to improve accuracy and address some of the limitations inherent in conventional design standards
Determination of Equivalent Temperature for Asphalt Pavement Design in Vietnam
Full text linkTemperature is a critical factor influencing asphalt pavement performance and its service life. Current pavement design practices in Vietnam, however, rely on fixed temperature values, disregarding regional climatic variations. To address this limitation, this study introduces a revised concept of "equivalent temperature", which is a representative temperature value that accounts for daily temperature fluctuations over a 20-year period. The objective is to enhance the accuracy and durability of pavement design by determining region-specific equivalent temperatures. Utilizing temperature data from 127 weather stations spanning 20 years, a gridded temperature map of Vietnam is constructed. The Shell method is employed to calculate Weighted Mean Annual Pavement Temperatures (WMAPTs) for each station. Results reveal significant spatial variability in WMAPTs across the country, ranging from 30°C to 41°C. These findings underscore the inadequacy of a singular design temperature for Vietnam's diverse climate. The calculated WMAPTs offer a valuable dataset for estimating asphalt moduli and informing future pavement design and research efforts, ultimately contributing to improved pavement performance and extended pavement service life in Vietnam
Production and Strength Evaluation of Sandcrete Hollow Blocks Using Fine sand and Crushed Periwinkle shell
Full text linkWalls are fundamental in building construction, with sandcrete blocks being the most common unit in Nigeria. Sandcrete blocks are made of natural sand, water, and cement. Due to rising material costs, importation issues, and sub-standard materials that do not meet quality specifications in terms of strength, durability, or composition, there is a need to find cost-effective alternatives. This research explores using Crushed Periwinkle Shell (CPWS) to partially replace fine sand. A 1:12 mix ratio was chosen for its cost-effectiveness and suitability for non-load bearing applications. This mix was tested with 0%, 10%, 20%, 30%, 40%, and 50% CPWS, maintaining a constant water-cement ratio of 0.5. Ninety blocks (450mm x 225mm x 150mm) were molded and cured for 28 days. The compressive strength of seventy-two blocks was evaluated at 7, 14, 21, and 28 days. Blocks with 40% and 50% CPWS had high compressive strength values of 2.55 N/mm² and 2.67 N/mm² at 28 days, within the Nigeria Industrial Standard (NIS) range of 2.5-3.4 N/mm². These results suggest CPWS is suitable for partial sand replacement. Additionally, eighteen blocks were tested for water absorption at 14, 21, and 28 days, showing increased absorption with higher CPWS content but decreasing with curing time
Development of P-Y curves for single piles based on full-scale lateral load tests and the cone penetration test (CPT) in clayey soils
Full text linkIt is nowadays recognized that the load-transfer P-Y curves methods offer a powerful framework of analysis of the pile response under lateral loading. The aim of this paper is to present a new formulation the P-Y curves to analyze the response of a single pile embedded in clayey soil, on the basis of the CPT test data. The methodology of work consists of analyzing 8 lateral loading tests on fully instrumented piles driven into a homogeneous saturated clayey soil. The P-Y curves were formulated by the PARECT (parabola-rectangle) function, and successful correlation of their parameters, namely the lateral reaction modulus and the lateral soil resistance, with the cone resistance as well as with the lateral pile/soil stiffness ratio was made. After a comparison with the existing P-Y curves methods, a methodology of analysis by the proposed P-Y curves for piles in normally consolidated to slightly over-consolidated clays was suggested. Moreover, a pile classification according to the pile/soil stiffness ratio was suggested, and the concept of the critical deflection corresponding to the threshold of domain of large deflections of piles was introduced. Validation process was launched by applying this methodology to a centrifuged scale model of a single bored pipe pile in a saturated slightly over consolidated clay. Direct comparison of the load-deflection curves showed an excellent prediction of the small deflections up to about 2% of the pile diameter. Beyond this value, the boundary conditions at the pile tip have an influence on the results, but showed a relatively pessimistic prediction
Determination of Substructure and Sub-ballast Layer Thickness of High-Speed Railway
Full text linkThe thickness of trackbed layers plays a crucial role in distributing train loads to ensure that stresses on the sub-ballast and substructure remain within acceptable limits. Vietnam is currently studying the construction of a high-speed railway (HSR) on the North-South axis, with two scenarios involving train axle loads of either 17 tons/axle or 22.5 tons/axle. This study focuses on determining the appropriate thickness for the sub-ballast and substructure layers to accommodate these axle loads. Using analytical methods, calculations were performed to determine optimal trackbed thickness. The results indicate that for an axle load of 17 tons, the substructure thickness should be approximately 1.75 m, while the sub-ballast layer should be around 0.27 m. In contrast, for axle load of 22.5 tons, the substructure thickness increases to about 1.94 m, and the sub-ballast layer thickness grows to approximately 0.36 m. These variations highlight the impact of axle load on trackbed design. The substructure layer's thickness is particularly important as it directly influences stress distribution throughout the trackbed. A well-designed trackbed ensures the structural integrity of the railway system, sufficient load-bearing capacity, and cost-effective construction. Proper determination of layer thickness is essential to balance performance, durability, and economic feasibility in high-speed railway infrastructure projects. This research provides a foundation for optimizing trackbed designs in Vietnam's high-speed railway scenarios, contributing to safer and more efficient railway operations