The Journal of Engineering and Exact Sciences

Impact of Curing Periods on the Evaluation of Thermal, Mechanical Properties, and Energy Consumption of Concrete Buildings

Abdallah Talhaoui — 2024-05-01

This study examines the impact of the curing period on the thermal and mechanical properties of concrete and its subsequent effect on building energy consumption. The research methodology is divided into two parts: experimental and simulation. In the experimental section, concrete specimens were created using regular concrete with a dosage of cement of 350 Kg/m³, and curing periods were varied (without curing, 3, 7, 14, 21, and 28 days) to assess thermal conductivity, density, ultrasonic pulse velocity, and compressive strength at 28 days. The results indicated that compressive strength increased by 71% between uncured and 28-day cured specimens, ultrasound propagation speed increased by 15%, and thermal conductivity increased by 31% with longer curing periods. A simulation using TRNSYS software estimated the energy consumption of a reference building with varying concrete properties based on the curing period. The simulated building consisted of three rooms, a hall, and a kitchen, with double exterior walls of 25 cm thickness and interior walls of 10 cm thickness. The findings revealed that longer curing periods contributed to increased energy consumption in the building. This study provides valuable insights into the relationship between curing periods, concrete properties, and their effect on the energy efficiency of concrete buildings.

Development and evaluation of a new bioadsorbent from Amazonian tucuma (Astrocaryum aculeatum) waste

Tamyris Thaise Costa de Souza — 2024-06-17

Adsorption is a technique frequently used in the treatment of contaminated water. The agro-industrial waste used to obtain bioadsorbents has been studied as an alternative with low operational costs and a positive impact on the environment. This manuscript evaluated the efficiency of tucumã peel (common waste from the Amazon region) as an adsorbent for methylene blue. The removal efficiency, adsorption capacity, and process kinetics were evaluated in the adsorption process developed. Adsorption tests achieved dye removal efficiencies of 74% to 91%. The best fit to the experimental data was obtained to pseudo-second order kinetic model and the Freundlich isotherm. Thus, waste tucumã peel can be used as a low-cost biocompatible adsorbent to remove of methylene blue dye.

Study of the Workability of Self-Compacting Concrete (SCC) Using Experimental Methods and Artificial Neural Networks (ANN)

Amar Mezidi — 2024-05-24

The self-compacting concrete (SCC) flows under its weight and does not require external vibration for compaction. However, its formulation requires careful calculation of its constituents. Three methods are considered: the first is an empirical method represented by an approach based on mortar optimization, a solution proposed by Japanese researchers who originally introduced the concept of self-compacting concrete; the second is a graphical method by Dreux-Gorisse used for ordinary concrete, which optimizes the composition of the aggregate skeleton by selecting fractions without additives and superplasticizers; and the third is a statistical method that we developed using an approach based on Artificial Neural Networks (ANN) built from a database from previous research projects. The objective is to characterize workability through an ANN model and compare it with experimental methods. Therefore, we focused on the slump flow, L-box, and sieve stability segregation tests.

Influence of Concrete Compressive Strength on L-Shaped Shear Wall Performance in Buildings within High-Seismicity Zones

Salem Merabti — 2024-05-13

Reinforced concrete mid-rise structures are supported by shear walls to withstand lateral forces resulting from earthquakes. In this context, the presence of openings in these walls is essential both functionally and aesthetically. This study employed L-shaped shear walls with varying vertical opening ratios, ranging from 15% to 50%, and compressive strengths ranging from 20MPa to 40MPa in a ten-story building. The study results demonstrate the significant role played by openings and the compressive strength of concrete in reinforced concrete walls to ensure buildings withstand earthquake forces. In this regard, we have developed reference models that adhere to seismic design principles and utilize optimized dimensions for openings based on the compressive strength of the concrete.

Shallow tunneling's impact on surface settlements

Mohamed Djenane — 2024-05-13

The research described in this paper deals with the impact of shallow tunneling on surface settlements in urban areas. The study focuses on carrying out a numerical analysis and a parametric geotechnical study to investigate the effects of tunnel excavation on the surface ground, particularly with regard to distortion and potential damage to structures above the tunnel. To carry out the study, the researcher used a finite element method (FEM) software package called Plaxis. This software is commonly used for geotechnical analysis and allows simulating and analyzing the subsurface conditions in Algiers underground in the context of excavating a shallow tunnel. The New Austrian Tunnelling Method (NATM) excavation method was chosen for the study. The results of the numerical analysis are presented in terms of displacements. The results indicate that ground flow has a significant influence on ground movement, probably contributing to surface settlement. However, the effect of tunnel excavation on the lowering of the water table and Young's modulus (a measure of soil stiffness) is relatively small in comparison. The research provides valuable information on the potential impacts of shallow tunneling in urban areas and the factors that play a crucial role in determining the extent of ground movement and surface settlement. By using numerical analysis and conducting a parametric geotechnical study, and gives valuable insights into the potential impacts of shallow tunnelling in urban areas and the factors that play a crucial role in determining the extent of ground movements and surface settlements. By using numerical analysis and conducting a geotechnical parametric study, and contributes to a better understanding of the behavior of the ground during tunnelling operations in Algiers. The findings can be helpful in designing future tunnelling projects to mitigate potential risks to structures and infrastructure located above the tunnels.

Numerical modeling of RC column reinforced by new strategy using fiberglass tape and cloth

Aissa Boumedjane — 2024-05-13

This paper presents the results of finite element analysis (FE) to study the axial compression behavior of reinforced concrete columns wrapped with tapes and fiberglass cloths according to different techniques using ABAQUS software. In the beginning, columns are modeled as 3D solid elements with a concrete damage plasticity model (CDPM), as the columns in this study are considered to be low compressive strength reinforced concrete and the rebar as 3D mesh elements. And once assembled, the specimen is wrapped with tape and cloth in the form of three-dimensional shell elements. Then, in order to analyze the behavior of the ultimate loads, the deformation of the confinement material, and the distribution of deformations in the concrete, the controlled displacement method used to apply the uniaxial compression loads to the specimen. Finally, a new mixed confinement model between partial confinement and complete has been proposed using a database of the results of a numerical simulation for confined concrete by fiberglass tapes and cloths. And it was found that the confinement strategy proposed in this study is very effective for the behavior of the reinforced concrete column, as the stress decreases significantly with the expansion and widening of the confinement stiffness of concrete in the plastic phase which improves the axial stress resistance.

Incompressible Schrödinger Flow with Heat-Transfer: An Introduction to the Analysis of Isotropic Fluid Dynamics in Sobolev Spaces for an Immersed Arbitrary Isothermal Geometry

Rômulo Damasclin Chaves dos Santos — 2024-02-06

This research investigates the intricate interplay of incompressible Schrödinger flow, heat-transfer, and the presence of an immersed isothermal body. The mathematical framework encompasses the Schrödinger equation for incompressible fluids, the heat transfer equation, and introduces a term that represents the thermal influence of an immersed isothermal geometry. Emphasizing the modeling and analysis of isotropic fluid dynamics, the study seeks to unravel the subtle relationship between the principles of quantum mechanics and the classical behavior of fluids. The initial discoveries produce an important theorem that leads the name of the authors, allowing new and valuable insights into the effects of the isothermal body immersed in a fluid medium. As a result, it was found that the term temperature source offers a unique perspective at the intersection of quantum mechanics and fluid dynamics.

Application of the hypoplastic model for validating direct shear tests to investigate the impact of fines on the behavior of chlef sand

Benali Nougar — 2024-05-27

This study was carried out to describe the mechanical behavior of different materials in terms of shear strength, cohesion and friction. For this purpose, an experimental shear tests were carried out. The soils used for the preparation of the samples were the Chlef sand, Chlef silt and M’zilla clay and a mixture composed of 50% of silt and 50% of clay. The soils were prepared by mixing Chlef sand with fines content of silt, clay or clay silt ranging from 0, 10, 20, 30 and 40%. The tests were conducted on sand samples prepared at a relative density of 20% representing a loose state and subjected to three normal stresses of 100, 200 and 400 kPa. All the tests were conducted at constant displacement rate of 1.00 mm/min. From the obtained results, it can be seen that the clean sand showed the highest shear strength at a small strains. At large strains, sands with 30% clay rather than 30% clay silt showed the highest shear strengths respectively. More contracted sands have the greatest increased maximum shear strengths. The sand with clayey silt, at a fine content of 20%, develops the most increased cohesion, among the other silty-clayey sands, together with the most reduced shear strength in elastic behavior. The sand with 40% of silt content develops a greater internal friction angle, however, the other silty sands, showed reduced shear strength, at the same behavior. To validate these findings, numerical simulations were performed on sand-silt mixtures using the hypoplastic model. The results indicated that the hypoplastic model accurately predicts the shear behavior of sand-silt mixtures in direct shear test, providing realistic insights into the effects of fines on the mechanical properties of the soil.

Keywords: Sand, Silt, Clay, Fines Content, Shear Strength, Friction, Cohesion.

Investigation of the Effects of Buildup Factors on Electromagnetic Radiation Dose

Ayomide Matthew Adefisoye — 2024-06-05

The buildup factor is an important element in radiation protection and shielding. It is also an essential component of the equation for dose calculation. In this study, dose conversion factors were calculated for outside exposures from gamma-rays. The calculations were established on the point-kernel integration method where two expressions for buildup factor were tested; (a) Taylor’s buildup factor and (b) Linear buildup factor. Dose calculations were performed for the two buildup factors expressions at energy range of 0.01MeV – 10.00MeV. The calculations yielded two results for the Dose conversion factor, which are at variance within the range 0.01-3.00MeV and > 5.00MeV. However, there is apparent agreement between the two results for energy range 3.00-5.00MeV. The result for the Taylor’s build-up factor correlates closely with the earlier results obtained from experimental and theoretical approaches. It has therefore been revealed that the choice of buildup factor used in dose calculation affects the output of the calculation.

Use of Paper Ash and Lime as a Sustainable Stabilized Materials for Lateritic Soil

Adekunle Isaac Omole — 2024-05-10

This research investigates the effectiveness of paper ash and lime for stabilizing lateritic soils in road construction applications. We assessed varying concentrations of paper ash and lime (0%, 3%, 6%, and 9%) to evaluate their effectiveness for soil stabilization. Initial analyses, including grain size distribution through wet sieving, specific gravity, moisture content, and Atterberg limits, were conducted to classify the soil. Following this, strength and compaction tests utilized standard proctor compactive energy, a method well-suited for field application. The findings indicated a general reduction in Atterberg limits (liquid limit, plastic limit, and plasticity index), an increase in maximum dry density (MDD), and a decrease in optimum moisture content (OMC) with increased concentrations of paper ash and lime. A thorough analysis of the results, along with a comparison to established standards, demonstrated significant improvements in soil properties. Specifically, the study found that 6% paper ash provided optimal stabilization, while 9% lime was effective as a stabilizing agent. These materials are suitable for use in the construction of subgrades and subbases for roads, aligning with AASHTO standards.

Influence of Empirical and Dynamic Periods on the Seismic Responses of Reinforced Concrete Buildings Braced by L-Shaped Shear Walls

Mohamed Khelladi — 2024-05-24

The Algerian Seismic Regulation of 1999, version 2003 (RPA99/v2003), presents ambiguities and a lack of thorough explanations in certain articles, which has led to a diversity of readings and interpretations among various stakeholders in the field, particularly the control offices. This situation has caused significant disagreements, especially during the approval of civil engineering files, thus resulting in a negative impact on project progress. To ensure adequate seismic protection of civil engineering structures, this work aims to unify the interpretations of certain passages of the regulation, with a particular emphasis on verifying the fundamental period of the structure, the shear forces at the base, and inter-story displacements using seismic calculation methods prescribed by the RPA. The comparative study demonstrates that no correlation between the period determined by the equivalent static method and that calculated by the spectral modal analysis method has been observed. This justifies the conclusion that adjusting between the empirical period and the dynamic period is not necessary.

Prioritizing Bridges for Seismic Resilience Enhancement: A Case Study of Algeria

Mohammed Abdellaoui — 2024-05-24

Algeria is located in an active seismic zone, making its bridges vulnerable to damage, especially older ones. Due to the importance of bridges in terms of safety, social, and economic factors, competent authorities must prepare for disasters, particularly earthquakes, by enhancing bridge resilience. However, due to the large number of bridges and lack of funding, it is not feasible to improve all bridges at once. This article proposes a model to determine priorities for enhancing bridge resilience to earthquakes based on expert opinions in three main steps. Step 1: Identification of key criteria, where design phase, bridge health, seismic zone, bridge importance, availability of alternative roads, and disaster insurance are defined as key criteria. Step 2: Calculation of criteria weights using the analytic hierarchy process (AHP) and integration of expert opinions using the Euclidean distance-based aggregation method (EDBAM). Step 3: Calculation of the priority index after evaluating criteria categories. The model was applied to six bridges, and their ranking was established based on the priority index. The model has proven its accuracy and ability to assist decision-makers in identifying priority bridges.

Comparative analysis of harmonic sensitivity for stator fault diagnosis in induction motors

Allal Abderrahim — 2024-01-30

Induction motors play a vital role in various industrial applications due to their commendable efficiency and reliability. However, their susceptibility to faults, especially in challenging industrial environments, highlights the need for vigilant fault detection to prevent unforeseen downtimes and reduce subsequent repair costs. Early fault diagnosis is crucial in this context. A systematic approach to diagnosing faults in asynchronous motors involves the application of signal processing techniques, particularly utilizing the Fast Fourier Transform (FFT). The FFT, as a mathematical tool, enables a comprehensive analysis of signals, facilitating the identification and isolation of their frequency components. Monitoring the frequency components within a motor's signal provides a means to determine the existence and severity of faults. FFT analysis allows for the monitoring of four distinct categories of harmonics: time harmonics (TH), rotor slot harmonics (RSH), rotor bar fault harmonics (RBFH), and eccentricity fault harmonics (EFH). Each type of harmonic offers valuable insights into specific fault categories. Empirical evidence, drawn from experimental results, emphasizes the heightened sensitivity of rotor slot harmonics (RSH) in detecting stator faults. Continuous monitoring of the RSH frequency component enables the prompt detection and localization of stator faults, along with an assessment of their severity. Additionally, this diagnostic methodology proves effective in identifying micro short-circuits between stator coils, allowing for a proactive strategy in predictive maintenance. This proactive approach enables anticipatory part replacement before degradation progresses to the point of causing comprehensive failure in the production chain. The combination of FFT-based signal processing and harmonic analysis establishes a robust framework for the early detection and localization of faults in asynchronous motors within industrial settings. This contributes to enhanced operational reliability and efficiency, ultimately ensuring smoother industrial processes.