Search Results (1,706)

This study presents an analytical investigation and a parametric evaluation of the structural behavior and seismic performance of highly corroded reinforced concrete (RC) columns, based on previously conducted experimental studies by the authors. In the analytical phase, moment–curvature relationships were obtained by considering the deterioration of the mechanical properties of both concrete and reinforcing steel due to corrosion in RC column specimens. By linking the sectional moment–curvature response with the element-level behavior observed in the experimental program, the plastic hinge lengths and rotational capacities of the corroded RC columns were determined. Subsequently, a parametric study was carried out using the analytical framework developed in the first phase on a set of 48 RC column models. In this investigation, axial load ratio, concrete compressive strength, corrosion level, section type, and concrete cover depth were considered as key parameters. The results of the combined experimental and analytical investigations demonstrate that the adopted section analysis approach successfully captures the nonlinear flexural behavior observed in the corroded specimens and provides a reliable basis for evaluating the structural performance and for supporting the assessment of seismic performance of deteriorated RC columns. Full article

Twelve reinforced concrete (RC) railway platform canopies were designed for zones with different seismic fortification intensities (SFIs) in accordance with the Code for Seismic Design of Buildings (2024 Edition) GB/T 50011-2010. Numerical models were created in OpenSees for each structure under three conditions: no corrosion, 5% corrosion loss of reinforcement, and 15% corrosion loss of reinforcement, using the Modified Ibarra–Medina–Krawinkler (ModIMK) hysteretic model. Through IDA, seismic collapse fragility was assessed in accordance with the requirements of the Standard for Anti-collapse Design of Building Structures T/CECS 392-2021. The results are: (1) Double-column canopies strongly resist deterioration from reinforcement corrosion. Each structure with different SFIs meets the code’s collapse probability limit under all three corrosion levels when subjected to the maximum considered earthquake (MCE) and the extreme considered earthquake (ECE, an earthquake larger than MCE). (2) When subjected to MCE, Single-column canopies with different SFIs also meet the code’s collapse probability limit under the three corrosion levels. (3) When subjected to ECE, the collapse probability of single-column canopies with 5% corrosion increases compared to uncorroded structures at SFIs ranging from 6 to 8; for SFIs 8.5 and 9, the collapse probability decreases. The structure with SFI 8.5 has the highest risk and does not comply with the code. (4) When subjected to ECE, the collapse probability of the single-column canopy with 15% corrosion increases significantly compared to uncorroded structures at all SFIs. Structures with SFIs ranging from 7.5 to 9 fail to meet code requirements. This paper systematically investigates the collapse fragility of platform canopies with different seismic fortification intensities in China, examining three corrosion states: no corrosion, 5% corrosion, and 15% corrosion. It provides important guidance for the rational design of platform canopies and for analyzing the impact of corrosion levels on their collapse behavior. Full article

Corrosion of reinforcing steel is a key cause of deterioration in reinforced concrete (RC) structures exposed to coastal environments with chloride presence. The loss of reinforcing steel cross-sectional area, cracking of the concrete cover, and reduction in confinement progressively decrease both strength and ductility of structural elements. This study provides a reproducible, open-access dataset, compiling input parameters and numerical results of the cyclic behaviour of isolated RC columns and RC frames, specifically addressing their nonlinear cyclic response under moderate corrosion (η < 25%), as well as in the non-corroded (baseline) conditions, generated through conventional nonlinear modelling. In terms of modelling, the methodology applies fibre-section modelling for columns and concentrated plastic hinges for beams. Furthermore, the corrosion effects are incorporated by reducing the steel area and ultimate strain, while also accounting for the decrease in compressive strength of the cracked concrete cover. Therefore, the cyclic response is represented by a Pivot-type hysteretic model. It is worth noting that the dataset provides model input information, such as material stress–strain relationships and backbone curves reflecting corrosion-induced deterioration. It also includes structural outputs, such as force–displacement relationships, and envelopes of quasi-static hysteretic cycles for the analyzed columns and frames. Overall, the dataset facilitates the calibration and validation of numerical models for RC structures affected by corrosion. In conclusion, the contribution enhances the reliability of computational simulations and supports the development of predictive tools for structural performance under degradation scenarios. Full article

The long-term durability of adhesive anchors in aggressive environments is a critical concern for infrastructure safety, with steel corrosion being one of the most detrimental phenomena. While glass fiber-reinforced polymer (GFRP) anchors offer corrosion-resistant alternatives to steel anchors in harsh marine environments, the bond performance at the anchorage interface progressively deteriorates under wetting–drying (WD) cycles, which may compromise long-term anchorage integrity. However, the bond characteristics of GFRP anchors under WD exposure, particularly the development of predictive models, remain insufficiently understood. This paper presents an experimental investigation into the impact of WD cycles on the bond of GFRP adhesive anchors in concrete. Twenty-four specimens were tested under pull-out loads, considering two key variables: bonded length (40 mm and 80 mm, corresponding to 5 and 10 times the bar diameter) and number of WD cycles (0, 30, 60, and 90). Artificial seawater was prepared via ASTM D1141-98 to simulate marine exposure conditions. The results revealed that both bond strength and bond stiffness decreased significantly with increasing WD cycles, while the failure mode progressively shifted from the bar–adhesive interface to the adhesive–concrete interface. Based on the experimental data, a cycle-dependent bond strength model was developed to predict the bond degradation of the anchor–concrete interface after WD exposure. Requiring only the undegraded concrete strength, the proposed model effectively captures the coupled effects of WD cycles and bonded length on bond strength degradation, presenting a practical tool for the durability design and service life evaluation of GFRP anchorage systems in coastal and marine environments. Full article

In this work, the tribological and corrosion behavior of commercially pure titanium—Ti-Gr2 with coatings obtained by mechanized contactless local electrospark deposition (LESD) with low pulse energy and a rotating electrode of TiB₂-TiAl reinforced with ZrO₂ and NbC nanoparticles was investigated. The current research is driven by the need for improved corrosion and abrasion resistance of titanium surfaces in automotive components, shipbuilding, aerospace, petrochemical and many other industrial and domestic areas. This work is a continuation of our previous study, in which the dependences of the relief, roughness, thickness, microhardness, composition and structure of the coatings obtained with this electrode on the electrical parameters of the LESD mode were studied and analyzed. In this work, the influence of the pulse parameters of the LESD process (respectively, roughness, thickness, composition and structure of the coatings) on the tribological and corrosion characteristics of the coatings has been investigated and the possibility of simultaneous protection of titanium surfaces from wear and corrosion has been demonstrated. Coatings containing nanocrystalline and amorphous-like structures have been formed, with synthesized new compounds and phases, and with increased hardness up to 13 GPa, low roughness Ra = 1.5–3 μm, thickness 8–20 μm and minimal structural defects. By comparing the potentiodynamic polarization curves, polarization resistance, electrochemical impedance and tribological characteristics of the coated surfaces, it has been established that their corrosion resistance increases by more than 1–2 orders of magnitude and their wear resistance during friction increases by 4–5 times compared to those of the substrate. Appropriate values of the electrical parameters of the LESD mode are presented, which allow obtaining uniform coatings with reduced roughness and structural defects, with predictable thickness, roughness and hardness, and with maximized corrosion and abrasive wear resistance to allow for uniform coatings with reduced roughness and structural defects, with predictable thickness, roughness and hardness, and with maximized corrosion and abrasive wear resistance. Full article

Reinforced concrete structures must balance immediate structural performance with long-term durability against environmental degradation, particularly carbonation-induced corrosion. While traditional cast-in-place concrete covers serve as the primary barrier, their substitution with prefabricated permanent formworks made of fiber-reinforced cementitious composites often fails to provide the necessary protective qualities required for aggressive environments. This study evaluates the durability and mechanical behavior of sisal-fiber-reinforced cementitious composites specifically engineered for use as permanent formwork. Short sisal fibers, treated by hornification to enhance dimensional stability and fiber–matrix adhesion, were incorporated at dosages of 2%, 4%, and 6% by weight. The experimental program included tests for water absorption, ultrasonic pulse velocity, axial compression, three-point flexural strength, and accelerated carbonation. The results indicated that composites with 2% and 4% of fibers exhibited reduced water absorption, sorptivity, compressive strength, and modulus of elasticity compared to the reference cement matrix. Residual stress values further demonstrated that the composites maintain significant post-cracking strength and stress transfer capacity, confirming their viability for structural elements. Although sisal-fiber-reinforced cementitious composites exhibit higher porosity and water absorption than conventional concrete used as reinforcement cover, they show sufficient resistance to carbonation to ensure a service life exceeding 50 years for reinforced concrete elements. Full article

Glass fiber reinforced polymer (GFRP) composites produced by pultrusion are increasingly used in structural applications due to their advantages such as corrosion resistance, high strength-to-weight ratio, and lightness. However, the extensive use of fibers in the longitudinal direction causes imbalance in the cross-section, leading to web crippling behavior in profiles subjected to transverse vertical forces. In this study, the influence of temperature and hole diameter on the web crippling performance of pultruded GFRP U-section profiles was investigated experimentally and analytically. The specimens were perforated with circular holes with diameters of 32–50–70 mm (diameter/Height ratio d/H = 0.23–0.36–0.50) at the web center and exposed to high temperatures of 200–250–300 °C, respectively, along with room temperature. The experiments were conducted under ITF (interior-two-flange) and ETF (end-two-flange) loading conditions. According to the results obtained, ITF configurations exhibited approximately twice the load-carrying capacity compared to ETF configurations. Due to the effect of high temperature, the web–crushing capacity showed a significant decrease of up to 44% on average in all samples when the temperature was increased from 24 °C to 300 °C. Increasing the hole diameter (and consequently the d/H ratio) led to a gradual decrease in capacity ranging from 15.7% to 56.2%; in particular, it was demonstrated that the ETF loading configuration is more sensitive to the hole than the ITF. As a result of the study, an empirical equation considering the effects of temperature and hole size was proposed, and the model’s predictions were compared with experimental results. Although the model successfully captured the general trend, the average absolute error rate in the predictions ranged between 12% and 14%, indicating improvement but not achieving ideal prediction accuracy. Full article

Carbon dots (CDs) have demonstrated promising application prospects in the field of corrosion protection due to their small size, excellent dispersibility, abundant and tunable surface functional groups, low cost, environmental friendliness, and unique fluorescence properties. However, existing reviews have predominantly focused on the synthesis and photoluminescence properties of CDs, lacking systematic integration and in-depth mechanistic analysis of their diverse applications in corrosion protection. This review systematically summarizes the recent research progress and underlying mechanisms of CDs in five key areas: corrosion inhibitors, anticorrosive coatings, photogenerated cathodic protection, chloride binding, and corrosion monitoring. As corrosion inhibitors, CDs form compact protective films on metal surfaces through synergistic physical and chemical adsorption. In anticorrosive coatings, CDs not only enhance the physical barrier effect but also impart intelligent functionalities such as self-healing and corrosion monitoring. In the field of photogenerated cathodic protection, CDs broaden the light absorption range of semiconductors and facilitate the separation of photogenerated carriers. As chloride binding promoters, CDs promote the formation of cement hydration products, thereby improving the durability of reinforced concrete structures. As sensing platforms, CDs enable early visual detection of corrosion through their specific fluorescence response to ions such as Fe³⁺. Despite significant progress, challenges remain in scalable preparation, practical application performance in complex environments, and multifunctional integration. This review systematically outlines the research advancements of CDs in corrosion protection, providing a practical reference for subsequent studies and engineering applications. Future research should focus on scalable synthesis, machine learning-assisted design, and the development of integrated multifunctional protection systems to promote the practical application of CDs in the field of corrosion protection. Full article

Additive manufacturing of concrete offers reduced waste, faster construction, and design freedom, yet effective reinforcement integration remains a major challenge due to weak interlayer bonding and anisotropy. Most prior studies focus on vertical reinforcement, short fibers, or metallic systems, achieving modest flexural improvements (15–60%). This study evaluates horizontal continuous reinforcement using glass fiber mesh and two carbon fiber meshes (ARMO-mesh 200/200 and 500/500) integrated during 3D printing. The methods include extrusion-based printing of small (four-layer) and beam-like (eight-layer) specimens, both printed and cast, followed by three-point flexural and compression tests at 7 and 28 days under vertical and horizontal loading. The results show that ARMO-mesh 500/500 significantly enhances flexural strength—up to 100% over unreinforced controls (e.g., 24.4 kNm vs. 12.2 kNm in small specimens at 28 days) and ~60% over ARMO-mesh 200/200, while glass mesh provides only marginal gains (~12%). Carbon meshes also improve post-cracking toughness and apparent interlayer cohesion. A pronounced size effect reduces nominal strength in larger specimens. These findings demonstrate that wide-format porous carbon meshes offer a scalable, corrosion-resistant solution for load-bearing 3D-printed concrete elements, advancing automated digital construction. Full article

To achieve the same service life of glass fiber reinforced polymer (GFRP) connectors and precast concrete sandwich panels, ensuring the structural stability and safety of the walls during long-term service, it is necessary to research the durability of GFRP connectors. In accordance with the ACI 440.3R-12 test method, an accelerated aging study was conducted by immersing 90 GFRP connectors in a simulated concrete pore solution at temperatures of 40 °C, 60 °C, and 80 °C for durations of 3.65, 18, 36.5, 92, and 183 days. This investigation aimed to analyze the effects of temperature and exposure time on the shear strength of the GFRP connectors. Scanning Electron Microscopy (SEM) was employed to analyze the micro-morphology of the specimens before and after exposure. The SEM observations revealed that after 183 days at 40 °C, the fiber-matrix interface remained relatively intact without significant debonding. However, at 60 °C, noticeable degradation occurred, characterized by corrosion of fibers and evident debonding from the surrounding matrix. At 80 °C, the GFRP specimens were severely damaged, precluding the extraction of viable samples for SEM analysis. The results further indicated that the most rapid decline in the shear strength occurred within the initial 3.65 days of exposure, with reductions of 8.62%, 10.12%, and 10.77% at 40 °C, 60 °C, and 80 °C, respectively. The degradation rate subsequently decelerated with prolonged exposure. After 183 days, the residual shear strength retention rates decreased by 21.03% and 26.89% at 40 °C and 60 °C, respectively. This behavior is primarily attributed to a high moisture absorption rate driven by a significant humidity gradient between the surface and the interior, leading to rapid swelling and plasticization of the vinyl ester resin matrix, which consequently reduced the stiffness and strength of the GFRP connectors. Finally, a predictive model for the time-dependent shear strength of GFRP connectors under various temperature conditions was developed based on Fick’s law. Full article

Carbon fiber reinforced polymer (CFRP) composites are widely used in many engineering applications such as aerospace, automotive, and defense industries due to their superior properties such as high specific strength, stiffness, and corrosion resistance. However, these materials require drilling, especially during assembly processes. Damage mechanisms arising during this process, such as delamination, high thrust force, and torque, negatively affect structural integrity and production quality. This study proposes a data-driven, multi-objective optimization approach to solve problems encountered during drilling in multi-walled carbon nanotube (MWCNT)-reinforced CFRP nanocomposites. The study considers the MWCNT reinforcement ratio, cutting speed, and feed rate as process parameters and examines their effects on thrust force, torque, and delamination factor. Second-degree polynomial regression-based prediction models were created using the experimental data obtained, and these models were included in the multi-objective optimization process. During the optimization phase, thrust force and torque values were simultaneously minimized, while the delamination factor was kept below the statistically determined constraint of F_d ≤ 1.054. Pareto-optimal solution sets were obtained using NSGA-II and MOPSO meta-heuristic algorithms in the solution process. The results indicate that suitable combinations of drilling parameters can be identified through Pareto-based optimization, allowing significant reductions in thrust force and torque while maintaining the delamination factor below the specified limit. The study presents a reliable optimization approach for the more efficient machining of CFRP nanocomposites. Full article

This study investigated the correlation between mechanical strengthening and electrochemical corrosion behavior in 18Ni300 maraging steel fabricated via laser powder bed fusion (LPBF). To evaluate the impact of post-processing, specimens were analyzed under four conditions: solution treated (S), solution peened (SP), solution aged (SA), and solution aged peened (SAP). The aging treatment (490 °C for 6 h) effectively enhanced the corrosion resistance by homogenizing the martensitic matrix and promoting the formation of a stable passive film, resulting in the lowest corrosion current density ($i_{corr}$ of 1.716 × 10⁻⁶ A/cm²). In contrast, the application of shot peening after aging (SAP) significantly degraded the corrosion resistance, characterized by the most negative corrosion potential ($E_{corr}$ of −0.374 V and a 2.4 times increase in $i_{corr}$ compared to the SA condition. Quantitative analysis revealed that the 1250 MPa of compressive residual stress induced by peening increased the thermodynamic instability of the surface through extreme lattice distortion, thereby lowering the activation energy for anodic dissolution. Furthermore, the increased surface roughness (60.68 µm) expanded the effective electrochemical reaction area, acting as a kinetic accelerator for corrosion. The results demonstrate that while the SA process provides an optimal balance between microstructural stability and corrosion resistance, additional shot peening (SAP) imposes a significant corrosion penalty despite its mechanical benefits. This study concludes that for 18Ni300 maraging steel, the trade-off between mechanical reinforcement and electrochemical stability must be carefully managed, emphasizing the need for surface stabilization when high-intensity peening is applied in corrosive environments. Full article

Fiber-reinforced polymer (FRP) reinforcement has emerged as an important alternative to conventional steel due to its high corrosion resistance and long-term durability. However, studies on the behavior of FRP-reinforced concrete deep beams under shear-dominated conditions remain limited. In this study, the structural behavior of reinforced concrete deep beams strengthened with GFRP and CFRP bars was numerically investigated using the ABAQUS finite element software. A parametric analysis was conducted to evaluate the effects of shear span-to-depth ratio (a/d), concrete compressive strength, tensile reinforcement ratio, and reinforcement type. The results indicate that reducing the a/d ratio from 1.4 to 1.12 increased the maximum load capacity by 37.6% for GFRP beams and 10.0% for CFRP beams, reflecting enhanced arch action. Increasing concrete strength from 25 MPa to 40 MPa led to capacity increases of 64.5% (GFRP) and 41.7% (CFRP), confirming its dominant role. Increasing the reinforcement ratio improved capacity by 6–9% in GFRP systems and over 15% in CFRP systems. CFRP-reinforced beams exhibited 20–55% higher load capacity, while GFRP beams showed greater ultimate displacement (13–18 mm vs. 8–12 mm). Overall, CFRP provides superior strength, whereas GFRP offers enhanced ductility, supporting performance-based design. Full article

Wind turbine blades are exposed to multiple coupled stressors requiring protective coatings with ultra-low volatile organic compound (VOC) content, thick-film capability, and long-term durability. This review critically evaluates waterborne polyurethane (WPU) coatings as a sustainable solution, benchmarking five synthesis routes—prepolymer emulsification, acetone process, melt dispersion, ketimine/ketazine chemistry, and self-emulsification—with prepolymer emulsification identified as the most industrially mature method. Key modification strategies are systematically compared, including nano-reinforcement, surface energy control, self-healing chemistries, and bio-based approaches. Based on a synthesis of laboratory, wind-tunnel, and field studies, three critical bottlenecks—thick-film formation, nanofiller dispersion, and long-term weatherability—are identified. To address these, a layered coating architecture is proposed, integrating a low-surface-energy topcoat, a lamellar-barrier mid-coat, and a post-crosslinked primer. This framework aims to guide the industrial deployment of WPU thick-film blade coatings in offshore and other extreme environments. Full article

This study presents two independently optimised Extreme Gradient Boosting (XGBoost) regression models, one for predicting corrosion current density ($i_{corr}$) and one for predicting corrosion potential ($E_{corr}$) parameters of carbon steel rebar embedded in mortar and immersed in simulated pore solution. An experimental dataset consisting of 216 measurements was curated from a systematic potentiodynamic scan study covering six chloride contamination levels, two carbonation states (non-carbonated and carbonated), four moisture conditions for mortar (65%, 85%, 95% relative humidity, and submerged), and three conditioning durations for simulated pore solution (36 h, 72 h and 20 days). Hyperparameters of the XGBoost models were optimised using a Bayesian optimisation framework with the Tree-structured Parzen Estimator (TPE) sampler over 300 trials. Model performance was assessed using 5-fold cross-validation and a random 80:20 train–test split. The optimised models achieved cross-validation $R^2$ scores of 0.936 and 0.953 for $i_{corr}$ and $E_{corr}$, respectively. On the hold-out test set, $R^2$ values of 0.933 and 0.945 were obtained with test RMSE values of 0.2 log₁₀(µA/cm²) and 41.9 mV, respectively. The contribution of each input feature to model predictions was quantified and visualised using the SHapley Additive exPlanations (SHAP) methodology. SHAP analysis reveals that chloride content has the highest impact on $i_{corr}$, followed by carbonation state and the low-humidity condition, while for $E_{corr}$, chloride content and the Submerged condition have the greatest impact. An interactive web application was developed using Streamlit, enabling researchers and practitioners to obtain corrosion parameter predictions. The findings provide data-driven insights into the relative importance of environmental factors governing rebar corrosion, with direct implications for the development of accurate corrosion prediction models for reinforced concrete service life assessment. Full article