Université Mouloud Mammeri de Tizi Ouzou (UMMTO): Research Review of Sciences and Technologies
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2222 research outputs found
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Dolphin Structures Health Monitoring: A Case Study in Hai Phong, Vietnam
No full textThe safety and durability of port structures are essential for ensuring uninterrupted maritime operations, particularly for dolphins used in berthing and mooring. This paper focuses on assessing a deteriorated dolphin structure in Hai Phong province, Vietnam, aiming to evaluate its current technical condition and structural integrity. The study adopts a multi-stage methodology combining visual inspection, dynamic response measurement, and numerical analysis. Field surveys documented extensive cracking, spalling, and material degradation in the pile system and cap, indicating significant structural damage. Vibration monitoring was conducted using accelerometers to record dynamic responses under vessel impact, and the results were analyzed through frequency-domain techniques. A finite element model was developed to simulate structural behavior and to compare calculated natural frequencies with field measurements. The findings revealed a significant reduction in load-bearing capacity, classifying the dolphin as severely degraded under international standards. The study demonstrates the effectiveness of integrating on-site inspection, vibration testing, and numerical modelling to provide a comprehensive evaluation framework for port structure health assessment
Optimizing FRCM Retrofitting Through FEM: Effects of Matrix Thickness, Mesh Size, and Textile Geometry
No full textIn Heritage constructions preservation, compatibility with existing materials, long-term durability, and structural performance are critically required. In this respect, the strengthening or repair of masonry panels using inorganic-based composite systems such as Fabric-Reinforced Cementitious Matrix (FRCM) has become an effective and increasingly adopted strategy. While experimental studies have widely demonstrated their capacity to enhance in-plane resistance and deformation capacity, the comprehensive assessment of damage processes within the strengthened system remains limited. Accordingly, this study presents a validated numerical investigation of the nonlinear shear response of masonry systems, including descriptions of the experimental models and the corresponding adopted material laws. Parametric analyses were conducted to assess the influence of the matrix thickness, textile mesh size, and their configuration on the ultimate shear capacity and the corresponding failure mode. Results in terms of shear stress and damage distribution indicate that the mechanical compatibility between the matrix and the fabric is crucial for providing an optimal retrofitting design
Evaluation of dynamic responses of concrete gravity dam considering dam-reservoir-foundation interaction with inclined absorptive reservoir bottom
No full textThe present paper shows the dynamic responses of concrete gravity dam considering inclined reservoir bed. Responses of gravity dam influenced by the adjacent reservoir and soil foundation. Interaction between dam, reservoir and foundation can give the authentic idea about the responses of the gravity dam subjected to dynamic excitation. Hydrodynamic pressure originated at the face of the gravity dam due to dynamic force. Bottom absorption and geometrical profile of the reservoir influence the behavior of the reservoir along with the adjacent gravity dam. In the present study, dam-reservoir-foundation system has been analyzed by direct coupling approach due to harmonic excitation including the fluid-structure and soil-structure interaction simultaneously. Reservoir bottom is considered as inclined and absorptive. Geometry of the dam, reservoir and foundation are discretized using finite element technique. Suitable non-reflective boundary conditions are applied along the truncated surface of the reservoir and soil foundation. Dynamic analysis of the dam, reservoir and foundation coupled system has been performed by applying Newmarks’ technic. Responses of the reservoir, dam and foundation have been observed for different inclination of reservoir bottom
Temperature-wind interactions and implications for civil engineering in the Congolese tropics
Full text linkTemperature has a strong influence on wind modelling, acting on pressure gradients and convective movements, which directly affect the loads on structures. In Central Africa, this climatic interaction must be taken into account to ensure the stability and durability of structures. This study analyzes the correlation between maximum temperatures and maximum wind speeds in several Congolese localities, based on data from meteorological stations. The approach combines descriptive statistics, visualizations (whisker boxes, histograms), simple linear regressions as well as the examination of possible transformations to optimize the quality of the fit, and residual analysis. The results show considerable regional variability: some cities (e.g. Pointe-Noire) show significant correlations, while others (Dolisie, Makoua) reveal weak or inverse relationships. These differences can be explained by geographical or microclimatic factors. The low coefficients of determination highlight the limitations of linear models, underlining the interest of non-linear or artificial intelligence-based methods to improve wind speed prediction. In terms of civil engineering, these results call for the design of infrastructures adapted to increasing climatic hazards
Influence of Fine Aggregates and Specimen Geometry on Mortar Compressive Strength
Full text linkThe characterisation and comparison of mortars prepared with different standardised sands are essential to ensure the equivalence of results obtained under distinct national and international testing standards. The performance of mortars is heavily dependent on the physical and mechanical properties of the sand used as fine aggregates, such as particle size distribution, grain geometry, and water absorption. This study compared the standardised sand from Brazil (IPT), European sand (EN), and local sand from Porto União (Brazil), aiming to assess differences in their physical and chemical properties, their effects on mortar consistency and compressive strength, and the influence of specimen geometry (prismatic and cylindrical) on strength outcomes. The fine aggregates were characterised using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and other tests for organic matter content, humidity, and water absorption. Results showed no significant differences in aggregate morphology, except for minor variations in sphericity. Chemical composition was comparable across samples, though absorption rates were higher for European sands. Mortar consistency was also affected, with European mortars showing significant differences compared to others, and statistical distinctions between the mortars using Porto União sand and IPT sand. Specimen geometry had no significant influence on compressive strength. This research underscores the importance of understanding fine aggregate characteristics in optimising mortar performance
Experimental and Numerical Characterization of Springback in V-Bending of AISI 304L Stainless Steel Enhanced by Machine Learning Prediction
No full textAccurate prediction of springback is a major challenge in sheet metal forming due to the material's ductility, strain hardening, and deformation-induced martensitic transformation. In this study, an integrated methodology is proposed, combining experimental measurements, finite element analysis, and machine learning to investigate springback in the V-bending of 1.5 mm thick AISI 304L austenitic stainless steel sheets. V-bending tests conducted at angles from 30° to 90° revealed springback percentages ranging between 20.30% and 37.33%. Subsequently, numerical simulations performed with ABAQUS/Explicit and calibrated using mechanical properties derived from tensile test results showed a good correlation with experimental data (MAE = 9.31%). To address the limitation of the number of physical samples, a data augmentation strategy based on values derived from literature was implemented, generating a training set of 200 synthetic data points. Seven regression models were evaluated via bootstrap validation, identifying degree-2 polynomial regression as the optimal model, with a mean absolute error of 2.98° ± 0.06° and a coefficient of determination (R²) of 0.985. The statistical validity of the model was confirmed by residual analysis demonstrating normality via the Shapiro-Wilk test (p = 0.644). A validated compensation table was generated for the direct calibration of industrial tools, demonstrating that even with a limited number of experimental data points, data-driven models can offer a reliable methodology for optimizing predictive manufacturing processes in sheet metal forming
Thermal Characterization of Stoichiometrically Varied Epoxy Networks under Elevated Heating Rates via Differential Scanning Calorimetry
No full textThis study presents a differential scanning calorimetry (DSC) investigation of epoxy thermosets formulated with varying stoichiometric resin-to-hardener ratios (1:1, 2:1, and 3:1) subjected to non-isothermal heating conditions. The influence of high heating rates of 15 oC/min for the epoxy-hardener ratio 1:1, 2:1 and 3:1 on the thermal transitions, residual cure behavior, and thermal stability was analyzed. The results demonstrate that deviations from stoichiometric balance significantly alter the thermal response of the cured networks. The 1:1 system exhibited a more uniform and complete cure with higher thermal stability, while excess amine 2:1 and excess epoxy 3:1 formulation exhibited prominent post-curing exotherms and thermodynamic instability. The glass transition occurred between 54.36 oC and 53.65oC for the ratios 2:1 and 3:1. The 1:1 ratio, among the tested stoichiometries, approximates this behavior under the applied high heating rate. Both 2:1 and 3:1 ratio demonstrated deficiencies in thermal parameters, confirming their suboptimal thermal and structural performance due to stoichiometric imbalance
Improving the essential characteristics of Lake Chad diatomaceous earth for the ecological construction.
Full text linkIn the Lake Chad region, diatomaceous earth is the type of soil that is easily accessible, but its use for construction presents challenges due to its specific characteristics. This study aims to characterize the physico-chemical and mechanical properties of these soils after adaptive treatment, consisting to add a small amount of lime. The X-ray diffraction reveals a composition of 73% quartz, 2.3% kyanite, 21% carbon and 1.58% of other minerals. The measured pH is 8.3, indicating this diatomite soil can be stabilize. Stabilized and Compressed Earth Blocks (SCEBs) were molded using six formulations (0% of lime added, 2%, 4%, 6%, 8% and 10%) and cured in three groups (groups of 7, 14 days and 30 days). The measure of their compressive strength denotes the SCEBs without lime, after 30 days of curing, show strength of 2 MPa and the SCEBs with 10% of lime exhibit a high compressive strength of 4.27 MPa, according to several standards of Compressed Earth Blocks. Thus, the addition of lime allow for the production of quality SCEB for construction. Regarding thermal properties, experiments on SCEBs show that thermal conductivity decrease with the addition of lime, from 0.194 W/m.°C to 0.370W/m.°K, and remain widely above 0.065 W/m.°K which is good value for thermal insulation. Finally, above 4% of lime, the mass loss (0.24%) is negligible
A Data-Driven Approach for Estimation and Multi-Objective Optimization of Concrete Mix Design
No full textThe study focuses on establishing the optimum concrete mix of ratios through a comprehensive analysis of experimental results. For this purpose, 62 numbers of concrete mixtures have been considered by varying the level of key ingredients- cement, water, fine aggregate and coarse aggregate. Using experimental data, Genetic Expression Programming (GEP) has been used to develop predictive equations for compressive strength and slump with cement, water, and coarse aggregates and fine aggregates as inputs. These equations are useful to estimate compressive strength and workability of concrete for particular ingredients. Moreover, mathematical multi objective optimization has been conducted by Genetic Algorithm (GA) using these equations as basic functions and optimum content of cement, water, fine aggregate and coarse aggregate have been determined for obtaining maximum compressive strength, maximum slump at lowest cost. Further, multi objective optimizations of different grades of concrete with slump and cost separately have also been carried out to determine these ingredients. Thus, by implementing the present results a more accurate number of mixed proportions with desired compressive strength, and slump can be obtained at minimum cost
Numerical Modeling of Coupled Thermo-Mechanical Bending Response in Functionally Graded Material Sandwich Beams
No full textThis study presents a novel comprehensive numerical investigation of the mechanical and thermo-mechanical behavior of FGM beams using Nonlinear Finite Element Analysis (NLFEA) implemented under ABAQUS. The studied beam is a rectangular-type sandwich beam with a polymer (PVC) foam core and polypropylene (PP) facings. Numerical FEM were firstly validated using experimental data from the literature and secondly extended to investigate additional loading and thermal conditions. The main objective is to assess the influence of the material gradient index (p) and the number of layers used for material discretization on stress distribution, stiffness, and ductility. Results in terms load-capacity curves and deformation patterns indicate that the gradient index strongly affects the overall beam response. While, the beam layers’ layout influences the stress redistribution along the thickness, with finer discretization producing smoother transitions. Comparing purely mechanical and thermo-mechanical loading, it is observed that thermal gradients introduce additional stresses due to differential expansion, altering the global stress field and interacting with the material gradation