2031 research outputs found
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Piles Pullout Enhancement Subjected to Inclined Loads
Get PDFThis study focuses on the experimental and numerical analysis of pullout resistance for a single pile subjected to inclined loads in sandy soil, both before and after improvement with asphalt enhancement. The sandy soil, characterized by low cohesion, poses significant challenges for foundation stability under vertical and inclined loading conditions. Pullout tests were conducted experimentally at angles of 0°, 30°, 45°, 60°, and 90° for both vertical and horizontal components of inclined loads using a custom-designed testing setup. Cutback asphalt was introduced as an improvement agent. The experimental results revealed a significant reduction in displacement up to 62% and an improvement in pullout resistance for the asphalt-treated soil up to 55% and 72% for vertical and horizontal load directions, respectively. PLAXIS software was validated through numerical modeling, which confirmed the improved load-displacement behavior and stress distribution. The asphalt enhancement demonstrated an improvement in pullout resistance, underscoring its effectiveness in creating a cohesive soil matrix that enhances load transmission and reduces void ratios. This research provides valuable insights into the load’s inclination and improvement with angle variations; the pullout capacity enhanced significantly with the inclination angle with vertical due to the formation of a bigger failure zone, thus offering practical solutions for improving the performance of pile-supported foundations in weak sandy soils under challenging inclined load conditions
Assessing the Effects of Freeze-Thaw Cycles and Traffic Load on Pavement Resilience
Get PDFThis study examines the impact of freeze-thaw cycles on the performance of flexible pavements, focusing on a specific road in Morocco. The primary objectives are assessing pavement resilience under varying climatic conditions and investigating the combined effects of freeze-thaw cycles, traffic speed (ranging from V1 to V4), and temperature fluctuations (from T1 min to T2 max) on pavement durability and structural integrity. The methodology involves comprehensive data collection on traffic loads, local climate conditions, and soil characteristics. These data inform the pavement design process, helping determine the optimal thickness and selection of materials to withstand environmental stresses. The study also examines the effects of freeze-thaw cycles, assessing frost-resistant materials and comparing frost indices to enhance durability. Advanced modeling techniques simulate pavement performance under real-world conditions, optimizing resilience. The methodology investigates the interaction between traffic speed and pavement behavior, focusing on strain (εz), displacement (Uz), and stress (σz). The findings reveal a significant correlation between freeze-thaw cycles and pavement deterioration, with strain and displacement increasing as traffic speed decreases while stress intensifies with higher traffic speeds. This research provides valuable insights into the effects of traffic speed on flexible pavements, contributing to more effective maintenance strategies and design solutions for durable, weather-resilient roadways. Doi: 10.28991/CEJ-2025-011-04-024 Full Text: PD
Examining the Erosion Resistance of Cement-Bentonite Barriers: Effects of Confining Pressure and GGBS Content
Get PDFThis 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
Axial Compression Behavior of Concrete-Encased CFST Columns
No full textComposite construction known as concrete-encased CFST is an outer covering of concrete surrounding a steel tube filled with concrete. It is employed as a structural member in multi-story buildings, large structures, bridges, and underground subway systems. Most of the literature deals with steel tubes filled with core concrete or concrete-encased steel tubes filled with core concrete with main reinforcement, but in the present study, CFST is used as conventional reinforcement. Therefore, five concrete-encased CFST columns and one normal reinforced concrete column were loaded axially. Variables were effects of CFST, percentage of steel tubes, outer concrete compressive strength, compressive strength of steel tube concrete, and ratio of unfilled steel tubes. The experimental test result of the reference concrete-encased CFST ultimate axial compression strength showed 65.1% strength of a conventional column. An increase in the ratio of CFST from 6.8% to 10.2% enhanced ultimate axial compression by 19.2% compared to the reference concrete-encased CFST column. Furthermore, a rise in the outer compression strength of the outer concrete from 15 MPa to 20 MPa resulted in an increase of 14.94% in ultimate axially compression loads. An increase of concrete compression strength within the steel tubes from 35 MPa to 45 MPa resulted in a slight increase of 0.62% in the ultimate load. The 16.8% reduction in the ultimate load, however, was due to the presence of a hollow steel tube inside the concrete-filled CFST. The validated finite element model was therefore employed to examine the effect of different parameters that affect the concrete column using a parametric study
Rehabilitation of Partially Corrosion-Damaged Post-Tensioned Concrete Structures Using Carbon Fiber Reinforced Polymer
No full textThis study provides a comprehensive assessment of the deterioration and rehabilitation of post-tensioned (PT) concrete structures affected by chloride-induced corrosion. Through a detailed case study in the United Arab Emirates, the research identifies moisture ingress and inadequate waterproofing as primary contributors to corrosion in PT tendons and ducts, significantly compromising structural integrity. A rigorous evaluation using nondestructive and semi-destructive testing techniques was conducted to quantify damage and determine the extent of degradation. The results revealed severe corrosion in critical structural elements, necessitating targeted intervention to restore performance and durability. To address these challenges, an integrated rehabilitation strategy was developed, incorporating structural repairs, strengthening through carbon fiber-reinforced polymer (CFRP), and advanced waterproofing techniques. The adopted approach involved enlarging load-bearing components and applying CFRP to enhance flexural strength while minimizing aesthetic alterations. Experimental findings demonstrated that CFRP reinforcement increased slab flexural strength by 30% and reduced crack widths by 23%, effectively mitigating corrosion-related deterioration and extending service life. Furthermore, micro-concrete was utilized in all enlargement locations in compliance with ACI standards, ensuring long-term durability. The proposed rehabilitation framework offers a sustainable solution for extending the service life of PT structures exposed to aggressive environmental conditions. By addressing both immediate structural deficiencies and underlying degradation mechanisms, the strategy enhances resilience and reduces future maintenance requirements. The integration of CFRP strengthening, epoxy crack injection, and advanced waterproofing measures significantly improves corrosion resistance and structural longevity
Structural and Soil Deformations in Non-Invert and Circular Tunnels: A Centrifuge and Numerical Analysis
No full textNon-invert tunnels are often chosen to reduce initial construction costs compared to circular tunnels, but they frequently require expensive maintenance. Despite their widespread use, limited research has quantified the differences in material requirements (steel and concrete) between these two designs. This study compares the internal forces and material demands of circular and non-invert tunnels using centrifuge model tests and numerical analysis. A combined approach using 40g centrifuge testing and parametric analysis in OPTUM G2 assesses bending moments, lining shear forces, and shear stress distributions. Three tunnel diameters (9 m, 12 m, and 16 m) are analyzed across depth ratios (H/D = 10, 7, 5, and 1), covering eight reinforced concrete lining designs. Results show that circular tunnels have more uniform stress distributions in the lining and surrounding soil, leading to lower bending moments and shear forces. In contrast, non-invert tunnels exhibit stress concentrations near the lower fulcrum corners and spring line. Due to their uniform stress distribution, circular tunnels become more material-efficient than non-invert at greater depths and larger diameters, reducing steel use by up to 36% despite requiring up to 19% more concrete. Non-invert tunnels, however, use less material at shallow depths, saving up to 14% in steel and 23% in concrete
Influence of Blast Furnace Slag on Concrete: Mechanical Strength and Microstructural Characterization
No full textThis study aims to quantitatively assess the effect of granulated blast furnace slag (GGBFS) as a partial replacement for Portland cement on the mechanical and microstructural performance of concrete with a design compressive strength of 280 kg/cm². A comprehensive experimental program was conducted to evaluate compressive strength, indirect tensile strength, flexural strength, and modulus of elasticity at curing ages of 7, 14, and 28 days, in accordance with ASTM standards. Microstructural characterization included Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM/EDS), and X-ray Diffraction (XRD). The results demonstrated that incorporating GGBFS, particularly at 16% and 20% replacement levels, led to significant improvements in compressive strength and stiffness at 28 days, while early-age tensile strength reductions were mitigated over time due to the latent pozzolanic activity of the slag. Microstructural analyses revealed a denser cementitious matrix, enhanced chemical stability, and the formation of new crystalline phases. Statistical analyses (ANOVA and Kruskal–Wallis) confirmed significant effects on flexural strength and elastic modulus. These findings underscore the potential of GGBFS to improve concrete performance and promote sustainability by valorizing industrial by-products and reducing CO₂ emissions. This work provides a robust experimental and analytical basis for optimizing GGBFS incorporation in durable, performance-enhanced concretes
Inelastic Response of Fixed and Flexible Foundation of Structure Under Seismic Excitations Generated Deterministically
Get PDFResearchers performed inelastic dynamic analysis on simulated ground motion while accounting for foundation flexibility in the specific area of Yogyakarta. The closest fault source to the building site is the Opak Fault, situated 2.1 kilometers from the structure. The closeness to the fault source, which suggests an exceedingly high earthquake magnitude, prompted the use of deterministic analysis. Deterministic analysis used five Ground Motion Prediction Equations (GMPEs): Campbell-Bozorgnia (2006), Sadigh et al. (1997), Ciao-Youngs (2008), Zhao et al. (2006), and Kanno et al. (2006), while the flexibility of the foundation was evaluated using the formula proposed by Novak (1989). The analysis results show that the vibration period that occurs on the flexible support is 2.8 seconds, while on the fixed support it is 2.4 seconds. Deflections and drift ratios in structures with fixed support and high-frequency content are greater, but in beam curvature the results show the opposite, namely, low-frequency content produces larger curvature values. The damage index on the fixed support and high-frequency content is greater than the others. Not much research has looked into the results of inelastic response analysis that includes hysteretic loop outputs and damage indices, making this a new area of study
Effects of Carbon Nanotubes on Asphalt Binder Rheology and Wearing Course Mixes
Get PDFThis study explores the influence of Carbon Nanotubes (CNTs) on the rheological and mechanical performance of asphalt binders and mixtures, with the objective of determining an optimal CNT content for enhanced pavement durability. CNTs were incorporated into asphalt binders at concentrations ranging from 0.5% to 2.0% by weight, and the modified binders were subjected to a comprehensive testing program. Rheological behavior was assessed using Rotational Viscosity (RV), Dynamic Shear Rheometer (DSR), Multiple Stress Creep Recovery (MSCR), and Bending Beam Rheometer (BBR) tests. Mechanical properties were evaluated through Marshall stability and Wheel Tracking tests, while microstructural characteristics were analyzed using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The results demonstrated that CNT modification enhanced binder viscosity, high-temperature stiffness, and rutting resistance, with optimal performance observed at 1.5% CNT content. At this dosage, rutting depth was reduced from 15.0 mm to 6.2 mm, and Marshall stability increased from 11.7 kN to 17.4 kN. Additionally, tensile strength peaked at 1290 kPa, and moisture resistance (TSR > 86%) was significantly improved. However, higher CNT concentrations (>1.5%) resulted in particle agglomeration, adversely affecting workability and fatigue resistance. The findings identify 1.5% CNT as the optimal dosage, offering a balanced enhancement in performance without compromising binder flexibility
Fracture Toughness of Fibrous Concrete Incorporated with Treated Recycled Aggregates
No full textThis paper examines the effect of recycled concrete aggregate (RCA) on the behavior of concrete, particularly when combined with different fiber mesh and treatment techniques. Recycled concrete aggregate was treated using two treatment methods. Method 1 used a mix of cement, silica fume, and water, while Method 2 combined cement, silica fume, water, sand, and superplasticizer. Two types of fiber, glass and polypropylene (plastic) fiber mesh, were placed across the expected crack path to study their effect on crack resistance. A total of 24 prisms were cast and tested. Tests measured slump, absorption, unit weight, compressive strength, and fracture toughness. The findings indicate that using recycled concrete aggregate decreases strength and workability compared to normal aggregate. Treated recycled aggregate enhanced the strength, especially in Method 2, which provided compressive strength even higher than normal aggregate. However, fracture toughness decreased due to the sudden formation of cracks. Interestingly, concrete made with untreated recycled concrete aggregate and glass fiber exhibited better crack resistance and fracture toughness. This study compares RCA treated using two different methods and reinforced with two types of fiber mesh, showing that minor changes in the mix design can enhance the behavior of concrete made with RAC