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2007 research outputs found
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Finite Element Analysis on Shear Responses of Reinforced Concrete Beams Strengthened with ETS-FRP Bars
No full textThis study conducts a numerical analysis on the shear performance of reinforced concrete beams retrofitted with fiber-reinforced polymer (FRP) bars with embedded through-section (ETS) technique. The study uses 3D nonlinear finite element method (FEM) and evaluates the shear features of ETS-FRP-strengthened beams in failure modes, shear capacity, stiffness, and ductility. The FE analyses consider the effects of key design parameters, including transverse steel stiffness (Eswρsw), ETS-FRP bar stiffness (Efρf), compressive strength of concrete (f’c), beam geometry, and the values of shear span-to-effective depth (a/d) ratio. Consequently, ETS-strengthened beams with higher concrete strength (f’c) or greater total rigidity of ETS and transverse reinforcement (Efρf + Eswρsw) showed notable improvements in stiffness and load-carrying capacity, with average increases exceeding 20%. The enhancement in shear strength from increased shear reinforcement stiffness is less pronounced in specimens with high concrete strength than in those with lower strength. ETS-strengthened beams with T-shaped sections exhibit more effective performance and safer failure modes. An enhancement in the a/d ratio reduces the stress in ETS bars but results in more ductile failures. This study also proposes a new analytical formulation for determining the maximum shear resistance of ETS-intervened beams, accounting for all failure modes. The model achieved an average predicted-to-tested shear maximum force ratio of 0.93 along with a coefficient of variation of 26%, demonstrating improved accuracy compared to existing models
Self-Cleaning Cement Material with Bismuth Titanate Photocatalytic Additive
No full textNowadays, mortars are building materials with various properties that can be achieved through the careful selection of components and the introduction of different modifying additives. An additive based on the TiO₂–Bi₂O₃ oxide system can be considered a modifying component with photocatalytic and biocidal properties capable of decomposing organic pollutants, viruses, bacteria, and fungal spores. The purpose of the work was to obtain cement compositions containing the additive, study their physical and mechanical properties, evaluate their photocatalytic activity in accordance with the UNI 11259-2016 standard, and assess their resistance to mold fouling. In this study, samples of cement–sand plaster with the TiO₂–Bi₂O₃ additive synthesized via citrate-based technology at 1.7 and 5.0 wt.% were prepared, and their physical, mechanical, photocatalytic, and biocidal properties were examined. As a result, the authors identified photocatalytic activity in both the UV and visible spectra, achieving 69% after 26 hours of UV irradiation. The samples demonstrated 100% resistance to mold fouling. The compressive strength of the modified samples increased by 32.0–39.0%; bending strength by 33–38.0%; and adhesion strength to the base by 60–70%. The cost calculation also confirmed the feasibility of introducing the additive at 1.7 wt.% into the cement composition. The resulting cement material formula can be recommended for designing fungi-resistant, self-cleaning plasters
Strength Characteristics and Material Design of Recycled Flexible Pavement Materials
No full textThis study develops a strength-based mix-design framework for rehabilitating flexible pavements using reclaimed asphalt pavement (RAP) blended with crushed rock (CR) and cement. Objectives were to quantify 7-day unconfined compressive strength (UCS) as a function of mixture variables and to provide field-ready proportioning equations. Methods comprised laboratory testing of RAP–CR blends (RAP = 0–100%) with 2–5% cement, Modified Proctor compaction, and 7-day UCS; regression related UCS to a modified parameter (w/c)(1−k·AS), where asphalt content (AS) is obtained from AS = 0.04·RAP. Findings show that increasing RAP lowers dry density (2.31→2.11 g/cm³) and raises optimum moisture (5.03→7.17%). The 7-day prediction is qᵤ,7 = 23.44/[(w/c)(1−0.22·AS)]0.677 (R² = 0.863). A worked example (4-cm asphalt over a 20-cm base; 20-cm milling) gives RAP = 20%, AS = 0.80, recommended w/c = 1.31, and cement = 4.03% at OMC = 5.28% and dry density = 2.276 g/cm³, satisfying 1.72 MPa (17.5 kg/cm²) at 7 days. Novelty/Improvement: the framework consolidates RAP content and binder effects into a single modified w/c parameter, enabling rapid, transparent proportioning for construction control. Broader impacts include reduced demand for virgin aggregate and haul-off of demolition debris, fewer truck movements and landfill burdens, and potential life-cycle cost savings in network-level rehabilitation
Influence of Resistance Spot Welding Parameters on Cold-Formed Steel Properties and Failure Modes
No full textLightweight steel structural systems such as built-up beams and trusses are efficient and easy to handle, but the joining technique between thin-walled cold-formed steel elements requires improved solutions. Conventional welding technologies are not suitable for connecting thin sheets due to several inconveniences. The study presents a novel technological approach to connect lightweight steel beams made of corrugated galvanised sheets for webs and back-to-back lipped channel profiles for flanges connected by spot welding, as resistance spot welding (RSW) is widely used in various industrial sectors, such as automotive. This study investigates the influence of RSW parameters on the microstructural properties of spot-welded low-carbon galvanised steel sheets, as well as on their mechanical properties. Two grades of base material were used with thicknesses in the range of 0.8 - 2 mm. RSW joints were manufactured using an automated welding source, and their microstructural characteristics were evaluated by optical and electron microscopy to emphasise the importance of using optimal welding regimes to reduce weld failure. Mechanical properties were evaluated using Vickers microhardness measurements and nanoindentation. Tensile tests were carried out to assess the force-displacement curves and identify the failure mode. The results of the study show that RSW is a promising method for fabricating lightweight steel structural systems when the current, time, and interelectrode forces of RSW are carefully selected
Structural Assessment and Rehabilitation of an Existing Hydraulic Masonry Structure Supporting Railway
No full textOld hydraulic masonry structures are essential components of global road and rail infrastructures. Over decades of operation, these structures have experienced inevitable deterioration, necessitating evaluations of their structural conditions through comprehensive assessment and rehabilitation programs to ensure compliance with contemporary safety standards. This study focuses on a specific regulator as a case example to implement a rehabilitation strategy aimed at restoring its structural integrity after 190 years of continuous service. From 2015 to 2021, an extensive program was conducted to assess the condition of the construction materials. This program included mechanical and physical testing, as well as Finite Element Analysis (FEA), to identify areas of high stress and to analyze the distribution of stress throughout the structure. The findings revealed that the structure fails to meet current Egyptian standards, thereby underscoring the critical need for a strengthening program. Subsequently, a rehabilitation intervention was developed, which involved reinforcing the intrados of the arches and piers with a slender reinforced concrete jacket. These reinforcements were integrated with the existing structure using steel shear bar connectors. Following the rehabilitation, a re-evaluation of the analysis of the modified structure using FEA software confirmed compliance with Egyptian specifications. The proposed rehabilitation strategy offers a viable solution to the challenges associated with the examined masonry arch bridge. Doi: 10.28991/CEJ-2025-011-02-012 Full Text: PD
Development of Oscillating Water Column Breakwater Model
No full textIntegrating coastal protection functions and wave energy conversion makes the OWC breakwater an environmentally friendly and material-efficient innovation compared to conventional breakwaters. This research aims to determine the wave runup height on the Sloped side of the OWC breakwater model and its internal pressure. Utilizing theoretical approaches, a 1:20 scale laboratory model, dimensional analysis, and parameter relationships, the study investigates the effects of wave interaction, model geometry, and water depth. The analysis reveals a positive correlation between the combined parameter value (𔜓) and relative pressure (P/Ïghs), highlighting the consistent influence of these parameters on pressure behavior. Results show that a lower slope angle increases pressure, while variations in inlet opening sizes (hs) significantly affect wave runup (Ru/Hi) and run-down (Rd/Hi). Larger inlet openings generally reduce the wave runup effect, though the magnitude of this impact depends on the slope angle. The optimal configuration for the OWC breakwater model is identified as an inlet opening size between 5 cm with a slope angle of 45° to 60°, providing relatively higher pressure while maintaining stability. This combination improves the system's efficiency in absorbing and using wave energy. Doi: 10.28991/CEJ-2025-011-04-02 Full Text: PD
Examining the Compressive Behavior of SFRC and SCC Using Finite Element and Experimental Methods
No full textThe compressive behavior of various kinds of concrete, including plain concrete, steel fiber-reinforced concrete (SFRC), and self-compacting concrete (SCC), was investigated experimentally in this paper and simulated using finite element analysis through ABAQUS software. Thirty specimens were cast and tested with two concrete compressive strengths (20 and 30 MPa). Steel fibers were added at volume fractions of (0, 0.4, and 0.75)%, while SIKA-VISCOCRETE-5930 IQ was incorporated at (0.8 and 1.8)% by weight of cement. The results showed that the compressive strength of the tested specimens increased with the increase of fibers and SIKA-VISCOCRETE-5930 IQ dosages. The FEA results exhibited a good agreement with those from the experimental work in terms of the stress-strain relationships for plain, SFRC, and SCC. A Student's t-test was performed on both experimental and FE analysis outcomes, and the difference among them was found to be statistically insignificant. The accuracy of numerical modeling in predicting concrete behavior under compression is supported by the findings of this study, and the effectiveness of steel fibers and SIKA-VISCOCRETE-5930 IQ in developing the compressive strength of concrete is also highlighted. Doi: 10.28991/CEJ-2025-011-03-017 Full Text: PD
Examining the Erosion Resistance of Cement-Bentonite Barriers: Effects of Confining Pressure and GGBS Content
No full textThis study investigates the erosion resistance of cement-bentonite (CB) barriers, focusing on the role of varying levels of Ground Granulated Blast Furnace Slag (GGBS) content and confining pressure, crucial for infrastructure such as dams and levees. Employing a bespoke modified triaxial erosion testing setup, the research assesses how different confining pressures, GGBS proportions, and curing periods impact the erosion resistance of CB materials under varying stress conditions. Results demonstrate that increasing GGBS proportions enhances erosion resistance by improving the CB matrix microstructure, while higher confining pressures generally increase resistance. However, combinations of high confining pressure and erosive force can lead to barrier material failure, with buckling failure occurring at elevated pressures (100 kPa and above), highlighting a trade-off between enhancing erosion resistance and maintaining structural stability. Extended curing periods allow for material strength development, enhancing stability, yet delayed erosion phases at higher confining pressures and longer curing durations suggest gradual crack formation, potentially leading to hydraulic fracturing. This underscores the need for meticulous design considerations regarding load conditions due to significant failure modes such as buckling. The findings emphasize that the strategic combination of GGBS content, confining pressure, and curing period is crucial in optimizing barrier performance, highlighting the importance of selecting optimal material formulations and operational parameters to maximize erosion resistance and ensure the longevity and safety of civil engineering structures
Sustainable Interlocking Blocks Containing Sugarcane Bagasse Ash: Structural Integrity, Cost Efficiency, and Environmental Benefits
No full textThis study aimed to evaluate the potential use of sugarcane bagasse ash (SCBA) as a partial replacement for Portland cement in interlocking blocks to enhance sustainability, reduce costs, and mitigate environmental impacts. The research objectives included assessing the compressive strength, water absorption, durability, microstructural characteristics, cost-effectiveness, and carbon footprint of SCBA-modified interlocking blocks. Experiments followed established standards, using various SCBA replacement levels (5–30%), with performance evaluated through mechanical testing, SEM analysis, cost assessment, and life cycle carbon footprint calculation. The findings demonstrated that interlocking blocks with 20% SCBA substitution maintained structural integrity, achieving a compressive strength of over 7 MPa, with acceptable water absorption and excellent durability. Cost analysis showed savings of up to 7.53%, while environmental assessment revealed carbon emission reductions of 17.99%. Microstructural analysis confirmed the presence of calcium silicate hydrate, supporting strength development. The study also introduced the SCOPEC framework (Selection of materials, Composition and mix optimization, Operational performance, Production consistency, Economic feasibility, and Carbon reduction), offering practical guidance for SCBA utilization in sustainable block production. This research contributes a novel, scalable solution to reduce cement consumption, enhance resource efficiency, and promote eco-friendly construction materials for affordable housing projects. Doi: 10.28991/CEJ-2025-011-05-024 Full Text: PD
Predictive Modeling of CSH Formation in Cement Materials Based on SEM and EDS Analysis
No full textCalcium silicate hydrate (CSH) formation is a fundamental process required to enhance the density, strength, and durability of cementitious materials. However, there is a gap in the research on the structural, physical, and chemical transformations of CSH. The objectives of this study are to develop a predictive model of CSH formation in cementitious materials and evaluate the effects of gelatin powder (GP), silica fume (MS), ground coffee (SCG), and peanut shell (PS) on CSH formation. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) apply to the study of the composite cementitious materials. A multiple linear regression model is proposed to predict the changes of key elements, which improved the qualitative and quantitative understanding of the hydration mechanisms. The results show that GP significantly accelerates CSH formation by increasing the calcium and oxygen contents, while MS enhances pozzolanic activity by increasing the availability of silicon, resulting in structural densification. SCG contributes to the increase of carbon and oxygen by acting as a filler, while PS has minimal effect on hydration or crystallization. A regression model relating cement mix design proportions and CSH shows strong correlations between admixtures and chemical changes, particularly for calcium (R²=0.988) and silica (R²=0.985). To fill the existing research gaps, this study goes beyond previous studies, which primarily focused on individual aspects of CSH formation without considering the convergence of structural and chemical analysis