Search Results (246)

The deterioration of steel reinforcement through corrosion triggers cracking and loss of concrete cover, ultimately weakening the structure’s strength and ductility. In practical design and assessment, it is vital to precisely quantify the shear capacity of corroded reinforced concrete beams (CRCBs). In this paper, machine learning (ML) models are developed to predict the shear capacity of CRCBs, including kernel ridge regression (KRR), K-nearest neighbors (KNN), decision trees (DT), random forest (RF), gradient-boosted regression trees (GBRT), and extreme gradient boosting (XGBoost). A total of 408 data entries on the shear strength of CRCBs under different corrosion conditions were collected to establish an extensive database. The reliability of the proposed ML models is examined by contrasting their outputs with the experimental data. The XGBoost model demonstrated superior predictive capability, achieving an R² value of 0.994 and outperforming all other tested models, including RF, GBRT, and DT. The Shapley Additive Explanations (SHAP) algorithm is adopted to reveal the contribution of each input feature to the predicted shear capacity of CRCBs. The interpretive SHAP results show that the ultimate shear capacity of CRCBs is most influenced by beam depth (h), with the shear span-to-depth ratio (λ) and concrete compressive strength ($f_{cl,150}$) being the subsequent key contributors. A comparative assessment between the XGBoost model and traditional analytical models was carried out to estimate the shear strength of CRCBs. Results demonstrate that the XGBoost model delivers enhanced predictive accuracy and improved performance. A parametric investigation examined its robustness under variations in geometry and material properties, while a user-friendly interface was created to support its practical use. Full article

The bond strength of corroded reinforced concrete (CRC) structures is critical for structural safety and long-term durability. However, the corrosion-induced bond degradation process is influenced by multiple, coupled factors and exhibits complex, nonlinear behavior, making it difficult for traditional theoretical models to provide accurate predictions. To address this challenge, this study proposes a novel, unified prediction framework based on machine learning techniques. A total of 391 experimental datasets were collected and compiled, covering key parameters including bond strength, reinforcing bar diameter, yield strength, concrete cover thickness, concrete compressive strength, mass loss rate due to corrosion, and the presence of stirrups. Support Vector Machine (SVM) and Extreme Gradient Boosting (XGBoost) algorithms were employed to develop predictive models for bond strength. Model training and testing were performed using 10-fold cross-validation. Furthermore, the SHapley Additive exPlanations (SHAP) approach was introduced to enhance model interpretability and quantitatively assess the influence of each input feature, revealing that mass loss rate and bar diameter are the dominant factors. This study effectively bridges the research gap between high-precision black-box algorithms and the need for physical interpretability in engineering. The results demonstrate that (1) the proposed XGBoost model significantly outperforms traditional empirical formulations, achieving a high coefficient of determination (R² = 0.893) and a much lower coefficient of variation (25.85%) on the testing set, and (2) the SHAP analysis reveals that the machine learning predictions are highly consistent with established physical mechanisms, successfully capturing the negative impact of splitting tensile stresses caused by rust expansion and the positive confinement effect of stirrups. Overall, the proposed models demonstrate superior accuracy, robustness, and generalization capability, providing an effective tool and theoretical basis for evaluating bond behavior and designing durable CRC structures with broad engineering applicability. Full article

Steel reinforcement corrosion induced by chloride ingress in coastal environments is the dominant factor leading to the durability degradation of concrete structures. In this study, Ordinary Portland Cement (OPC) concrete beams and Portland Pozzolana Cement (PPC) concrete beams were used as test specimens, subjected to sustained loads to induce cracks, and exposed to accelerated reinforcement corrosion through 10 wet–dry cycles using a 3% NaCl solution. Testing methods including half-cell potential, corrosion current, and acoustic emission signals were employed to quantify the likelihood and progression of reinforcement corrosion. The results show that the half-cell potential of the loaded PPC beams remained below −350 mV, with a corrosion current density exceeding 0.5 μA/cm², indicating a significantly higher corrosion risk than that of the OPC beams; under unloaded conditions, the half-cell potential of the PPC beams remained consistently above −200 mV, with a corrosion current density below 0.2 μA/cm², exhibiting superior corrosion resistance. The event counts in the acoustic emission tests additionally revealed the progression of chloride ions gradually penetrating and corroding the steel reinforcement. Although PPC beams exhibit lower early-stage crack resistance under loading conditions and are prone to forming more cracks, their advantage in resisting chloride ingress becomes significant after appropriate mitigation measures are implemented to reduce early crack formation, making them remain a preferred material for reinforced concrete members in coastal environments. Full article

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

Tunnels excavated in non-coal oil- and gas-bearing strata may experience the seepage and intermittent ingress of an oil–gas–water mixture during construction, creating aggressive corrosive conditions that can compromise the integrity of primary support and the safety margin of the final lining. However, the coupled degradation mechanism of primary support and its cascading effect on lining safety under such conditions remain poorly understood. Based on the Huaying Mountain Tunnel project, this study investigates the corrosion-driven damage evolution of primary support and its implications for the structural safety of the secondary lining under wet–dry cycling exposure. Accelerated wet–dry cycling tests were performed on concrete specimens using an on-site crude-oil–formation-water mixture collected during tunnelling, with exposure levels ranging from 0 to 120 cycles. Laboratory observations were then combined with inverse identification of degradation-dependent material parameters to establish a corrosion-informed mechanical description, which was implemented in numerical simulations for structural response assessment. Results show a staged evolution of mechanical properties, with an initial increase followed by progressive deterioration. After 120 cycles, compressive strength, tensile strength, and elastic modulus decreased by approximately 18.9%, 23.1%, and 17.4%, respectively. Degradation is more pronounced in the corroded zone, with tensile capacity and stiffness deteriorating earlier than compressive resistance. Numerical results indicate that corrosion leads to significant stress redistribution and damage development. The sidewall tensile stress reaches 2.80 MPa after 120 cycles, exceeding the post-corrosion capacity, while the safety factor drops below the code threshold at 90 cycles. The overall safety probability decreases from 1.0 to 0.4, accompanied by a degradation in safety grade from Level I to Level IV. These findings provide a quantitative basis for deterioration assessment, safety verification, and maintenance planning for tunnels subjected to oil–gas corrosive environments. 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

To address the shortage of natural aggregates and freshwater, and promote the recycling of construction and demolition waste and localized construction materials for marine engineering, this study explores the electrochemical corrosion characteristics and deterioration mechanism of steel bars in recycled concrete aggregate (RCA)–seawater sea-sand concrete (SSC) concrete. Using RCA replacement rates (0%, 50%, 100%) as the core variable, specimens were prepared. Vacuum water saturation, open-circuit potential (OCP) monitoring, Tafel polarization scanning and electrochemical impedance spectroscopy (EIS) were adopted to study steel corrosion evolution within 180 days. The results show that RCA incorporation accelerates OCP negative drift and reduces passivation film stability, with more severe corrosion at higher replacement rates: the RCA100 group showed obvious corrosion after 60 days, while the RCA50 and RCA0 groups initiated corrosion at 90 days (RCA50 corroded faster). The surface mortar and internal microcracks of RCA enhance the water absorption and ion permeability of concrete, which, coupled with chloride ions, accelerates steel corrosion. This study clarifies the correlation between RCA replacement rate and corrosion parameters, providing data support for mix ratio optimization and marine engineering applications. Full article

This study systematically investigates the influence of steel fibers on the mechanical properties of cement concrete. End-hook, shear, and milling type steel fibers were selected, with comparisons made to copper-plated and corroded steel fibers. The effects of fiber type, aspect ratio (40–60), and volume content (0.5–1.5%) on the compressive, flexural, and splitting tensile properties of concrete were analyzed. A multi-objective mechanical performance prediction model was established using a combined macro- and micro-scale testing approach, integrated with response surface methodology (RSM) and I-optimal design. The results indicate that steel fibers can significantly enhance the overall mechanical properties of concrete. Among the types tested, the end-hook fiber exhibited the best performance in compressive and splitting tensile strength, and the 28-day compressive strength increased by 41% compared with plain concrete, while the milling fiber showed the greatest improvement in flexural strength, and the value reached up to 72%. Furthermore, the failure mode observations indicated that steel fiber incorporation fundamentally altered the fracture behavior of concrete, transitioning it from brittle fracture to quasi-ductile behavior with post-crack load-carrying capacity, particularly for end-hook and milling fiber types. An optimal parameter window for the fiber reinforcement effect was identified, with the best comprehensive performance achieved at an aspect ratio of 50–60 and a fiber content of 0.5–1.0%. The enhancement effect of copper-plated and corroded steel fibers was limited due to reduced interfacial bonding performance. The developed model demonstrates high prediction accuracy, providing a theoretical and experimental basis for the engineering application of fiber-reinforced concrete. Full article

Reinforced concrete (RC) structures in marine environments face severe durability challenges due to chloride-induced corrosion. This study investigates the corrosion mechanism and degradation of axial compressive performance in RC columns under the combined effects of sustained loading and corrosion, taking the permanent–temporary integrated RC columns of the Pinglu Canal project as an example. The experimental variables included different sustained load levels and degrees of corrosion. Twelve rectangular RC columns were designed and tested. A specialized setup was developed to simultaneously apply sustained load and induce corrosion to the columns, while monitoring their creep deformation. The columns were subjected to accelerated electrochemical corrosion in a 5% NaCl solution, concurrently under sustained loads of 0, 0.3, and 0.6 times their designed axial compressive capacity, with exposure durations of 0, 30, 60, and 120 days, respectively. The study examined the effects of sustained load level and corrosion degree on the failure mode, concrete creep deformation, and load–displacement curves of the corroded RC columns. The results indicated that sustained loading shortened the duration of concrete expansion deformation and reduced its peak value. Furthermore, the expansion deformation of concrete delayed the creep of corroded columns by 25 to 35 days; after the expansion recovery, the creep rate increased significantly. For corroded columns without sustained loading, the ultimate bearing capacity decreased by 32.0% to 47.8%, with degradations in both stiffness and ductility. The application of sustained loading alleviated the degradation in the ultimate bearing capacity and stiffness of the corroded columns but exacerbated the degradation of their ductility. Finally, considering the effects of concrete expansion deformation and steel corrosion, a predictive model for the creep of RC columns under the coupled action of sustained loading and corrosion was proposed, aiming to provide a theoretical basis for the durability design and maintenance of RC structures in the Pinglu Canal project. Full article

Reinforcement corrosion is one of the primary deterioration mechanisms affecting the long-term seismic performance of reinforced concrete (RC) structures. Although the effects of corrosion on individual RC members have been widely investigated, its influence on the cyclic behavior of RC frame systems has received limited attention. This study numerically investigates the seismic response of a single-bay reinforced concrete frame subjected to cyclic lateral loading under various corrosion scenarios. A three-dimensional nonlinear finite element model was developed in ABAQUS, incorporating corrosion-induced effects such as reinforcement cross-sectional loss, degradation of mechanical properties, bond strength deterioration, and concrete softening. The corrosion propagation rate and exposure duration were considered as key parameters, and different corrosion scenarios were comparatively evaluated. The numerical model was validated using an experimentally tested non-corroded reinforced concrete frame subjected to cyclic loading. The results demonstrate that reinforcement corrosion leads to significant degradation in the seismic performance of RC frames. Depending on corrosion severity, reductions of up to approximately 25% in lateral load capacity and up to 27% in both initial stiffness and energy dissipation capacity were observed. The findings further indicate that stiffness- and energy-based performance indicators are more sensitive to corrosion damage than strength-based indicators. The study highlights the importance of explicitly accounting for corrosion effects in the seismic performance assessment of reinforced concrete frame systems and provides a practical numerical framework for evaluating corrosion-induced performance degradation. Full article

Offshore reinforced concrete (RC) structures, such as bridges and high-piled wharves, are frequently subjected to the coupled action of steel corrosion and ship collision loads. However, existing studies lack systematic quantification and in-depth revelation of the synergistic degradation mechanism under this coupling effect, resulting in an insufficient scientific basis for engineering design and reinforcement. To address this gap, this study established a refined three-dimensional numerical model of drop hammer-reinforced concrete beams based on ABAQUS, comprehensively considering the strain rate effects of steel and concrete, steel–concrete bond–slip behavior, and the trilinear constitutive model of corroded steel. After validating the model’s reliability against experimental data from the existing literature, parametric simulations were conducted to investigate the coupled effects of different corrosion rates and drop heights (0.25–1.5 m). Key findings include: (1) corrosion reduces the peak impact force by 9.7–58.9% and increases the maximum mid-span displacement by 6.6–35.7%, with this effect amplified by higher drop heights; (2) shear performance degradation (16.14–35.19%) is significantly more severe than flexural performance degradation (13.28–28.93%), confirming that shear performance is more sensitive to corrosion; (3) corrosion causes cracks to propagate from a localized distribution to a global distribution, while higher drop heights accelerate structural evolution toward brittle failure; (4) the synergistic degradation law of “corrosion exacerbates impact damage, and impact amplifies corrosion defects” is revealed. By quantifying the corrosion–impact coupling effect, this study advances research in the field and provides critical technical support for damage assessment and service life prediction for offshore RC structures. In engineering practice, it is recommended that offshore structures in high-corrosion environments prioritize shear resistance enhancement and adopt targeted protective measures for high-impact-risk areas to mitigate the risk of brittle failure. Full article

Grouted sleeve connections (GSCs) are widely used in precast concrete (PC) bridge piers due to their convenience in construction and reliable structural performance. Corrosion-induced damage significantly compromises the seismic integrity of PC bridge piers with GSCs, making effective rehabilitation urgent. However, there is a scarcity of research addressing this specific retrofit need. To bridge this gap, this work systematically investigates the efficacy of ultra-high-performance concrete (UHPC) encasement in retrofitting the quasi-static seismic resilience of corroded GSC piers. Numerical analyses were conducted using OpenSEES, in which the GSCs were equivalently modeled by determining their yield strength and cross-sectional area. Three corrosion ratios of the GSCs (20%, 40%, and 60%) were considered. The effects of UHPC compressive strength (100 MPa, 120 MPa, 150 MPa) and different retrofit heights on the quasi-static seismic performance of the bridge piers were systematically investigated. The results reveal that corrosion of the GSCs markedly compromises the quasi-static seismic behavior of PC bridge piers, notably reducing both the bearing capacity and energy dissipation capacity. Retrofitting with UHPC shells effectively enhances the yield force, peak force, yield stiffness, and energy dissipation capacity of the piers. These improvements become more substantial with higher UHPC strength and greater retrofit height. Overall, the results underscore the significant detrimental effect of sleeve corrosion on quasi-static seismic performance and confirm UHPC retrofitting as a viable and effective mitigation approach. Full article

Stray current-induced corrosion poses a significant risk to the durability of reinforced concrete (RC) structures in electrified transit systems. This study addresses a critical knowledge gap by experimentally and analytically investigating the compression behaviors of circular RC columns under the combined effects of stray currents, chloride intrusion, and sustained service loads. The experimental program involved testing columns constructed with normal strength concrete (NSC) and moderate strength concrete (MSC) under accelerated corrosion induced by electrical potentials of 9 V and 18 V in a 3.5% NaCl solution. A key variable was the application of a sustained axial load, equal to 60% of the ultimate capacity, to simulate realistic service conditions. The findings revealed a severe deterioration in structural performance due to the synergistic effect of mechanical loading and corrosion. NSC columns subjected to 18 V potential and sustained axial loading exhibited a decrease in ultimate load-carrying capacity of up to 46% and a ductility reduction of approximately 69% compared to reference specimens. This damage was significantly more severe than in unloaded or lower-voltage (9 V) scenarios. Furthermore, MSC specimens demonstrated a strength loss of approximately 29% under similar aggressive conditions. An analytical confinement model, adjusted to account for corrosion by reducing the reinforcement cross-section and introducing a semi-empirical parameter α to represent localized pitting, showed strong agreement with the experimental stress–strain curves. The validated model provides a practical tool for assessing the residual capacity of corroded elements, addressing a crucial need in the maintenance of electrified transportation infrastructure. Full article

Based on ongoing experimental research, the present manuscript presents the effect of the slippage of a steel reinforcing bar due to corrosion on the chord rotation and deformation of corroded Reinforced Concrete members. The experimental results recorded that the increase in the corrosion level of the steel led to bond strength loss and relative slip between the steel and concrete, which was increased from 1.5 mm in non-corroded conditions to 3.5 mm even at low corrosion levels, up to a 5% steel mass loss. This slippage of corroded reinforcing bars from the anchorage leads to a proportional increase in terms of chord rotation due to pull out resulting in an additional increase in the displacement of the column’s top. In conclusion, the present study highlights the great importance of the contribution of the resulting slippage of a steel reinforcing bar due to corrosion in the calculation of the limit chord rotation (column–beam), a term which is of major importance in the assessment of the structural integrity of old RC structures, which was introduced as an adequacy requirement by both Eurocode 8-3 and the Greek Code of Structural Interventions (KAN.EPE). Full article

The structural vulnerability of RC structures during major seismic events raises several concerns regarding structural design and behaviour. Additionally, corrosion’s impact on steel and concrete, including a reduction in ductility, confinement and strength, can compromise structural performance, especially for reversal loading. This work investigates the combined effect of corrosion and seismic actions on the structural performance of RC structures. Numerical models of RC structures with 0%, 5%, 10%, 15% and 20% corrosion were proposed. The effect of corrosion in the numerical models was calibrated based on experimental studies carried out on corroded RC elements. Afterwards, we considered the scenario of corrosion in all peripheral structural elements of 5- and 10-storey MRF structures in three distinct conditions. To enforce vertical irregularity, we have imposed vertical irregularity at the ground level in each structure. An adaptive pushover analysis was performed to assess the effect of corrosion and vertical irregularity on the seismic response. The results demonstrate that, for the levels of 5% and 10% corrosion, uniform corrosion produces a deleterious impact on structural responses in 10- and 5-storey MRF structures, respectively, regardless of the level of irregularity of the elevation. However, the irregularity generates a higher impact in the seismic response than the uniformly distributed corrosion in height. The combined effect of those parameters must be considered in seismic codes for new and existing buildings in order to maintain safe performance levels. Full article