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Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A method is proposed for calculating a reinforced concrete flexible foundation on a soil base in an aggressive environment under rheological deformation conditions, taking into account corrosion damage, reflecting its real operation under the combined influence of force and non-force influences based on the modern phenomenological theory of deformation of an elastic creeping body. The possibility of considering the processes of long-term deformation of rein-forced concrete under a changing mode of action of an external load based on the method of integral estimates is shown. It is shown that environmental damage to reinforced concrete structures can affect the strength of the material, change the calculation schemes, redistribute efforts in the sections of the structure and also lead to other consequences that reduce the design life of buildings. An example of the calculation of a reinforced concrete flexible foundation of a residential building on a soil base is given, taking into account the friction forces along its sole at various periods of service life and the presence of corrosion damage.

The possibility of using computational methods to take into account the service life, nonlinearity and rheology of deformation of the materials used and potential corrosion damage of various reinforced concrete structural elements already at the design stage, which will allow to determine cross-sectional dimensions and assign the required grades of concrete and reinforcement, is studied. The considered process of long-term deformation of reinforced concrete under varying external load conditions is based on the integral estimation method of deformation resistance, which relies on the use of integral deformation modulus. A method for calculating a reinforced concrete frame on a soil base in aggressive environment under the conditions of rheological deformation has been developed, which reflects the real operation of structural elements under the combined influence of force and non-force factors based on the modern phenomenological theory of deformation of an elastic creeping body. Long-term operation of a reinforced concrete frame on a soil base, taking into account corrosion damage, is evaluated. An example calculation of a reinforced concrete frame of a building on a soil base is given for various operation periods and the presence of corrosion damage. It is shown that damage due to exposure of reinforced concrete structures can affect the strength of the material, change the calculation models, redistribute stresses in the cross-sections of the structure and also lead to other consequences that reduce the design life of buildings.

This study investigates sweet corrosion mitigation methods focusing on the efficacy of inhibitors. Specifically, it examines the performance of two types of inhibitors: water-soluble and oil-soluble. Utilising a Rotating Cylinder Electrode (RCE) setup, turbulence is induced in saline solutions to assess the impact of inhibitors on the corrosion of carbon steel. Scanning Electron Microscopy (SEM) is employed to analyse corrosion degradation patterns and material damage mechanisms. Given the prevalent use of inhibitor injection in the oil sector, it is crucial to evaluate and compare the effectiveness of various inhibitors to recommend optimal options and further studies. The findings contribute to advancing corrosion mitigation strategies, providing insights into the performance of inhibitors in flow environments and aiding in the development of more effective corrosion control measures for carbon steel structures. The inhibitors under study are sourced from local oil company vendors. With a projected duration of six months and a total budget of KD 9850, this investigation aims to provide valuable insights into corrosion mitigation strategies. [ABSTRACT FROM AUTHOR]

The main directions of development of the theory of structural safety of buildings and structures have been formulated. A hierarchical approach to the assessment of structural safety of objects under corrosion damage from structural materials to structural system is proposed. Peculiarities of corrosion damageability of concrete of reinforced concrete structures are determined, mechanisms of force and corrosion effects and their influence on progressive destruction of structural systems of exploited buildings are analyzed.

Corrosion of steel rebar in reinforced concrete (RC) constructions is an issue of great concern toward ensuring the integrity of civil structures, and thus, detection of the on-set of corrosion process, if any, will tremendously help in taking timely and effective measures. To address this issue, the current work aims to evaluate the potential of using different nonlinear ultrasonic (NLU) methods to detect corrosion through analysis of the signal characteristics from both time and frequency domain. Three NLU parameters (from time and frequency domain response) are studied by using an indirect type of measurement obtained from RC specimens undergoing accelerated corrosion process. Signal subtraction method (SSM)-based time domain nonlinear parameter and sideband peak count (SPC)-based frequency domain nonlinear parameter are found to be effective in detecting the specific damage stages during the corrosion process. There exists a significant shift in the cumulative nonlinear parameter curve arrived based on SSM when the mass loss is around 14 g, corresponding to the time at which the first surface crack of about 0.2 mm width appeared. Cumulative nonlinear parameter curve arrived based on SPC, shows a drastic shift when the mass loss is only 2 g, i.e., at the time when microcrack initiates inside concrete. To provide a complete monitoring solution, the complementary abilities of both time and frequency domain NLUs are used for the first time to formulate a damage index that can effectively monitor the progression of damage caused by corrosion from the beginning of the process until the point of failure. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Corrosion-induced concrete cracking is a significant stage of structural deterioration in prestressed concrete (PC) structures. Most current research predominantly focuses on the corrosion of prestressed steel strands, while paying limited attention to the study of non-prestressed reinforcement corrosion. In this study, an integrated material-structural numerical approach was developed to simulate corroded PC beams, considering corrosion products migration in pores and cracks. The cracking patterns and prestress losses obtained from the simulation results agreed well with experimental observations. Subsequently, using the proposed numerical approach, the interaction mechanism of the prestress level and reinforcement corrosion was investigated. The simulation results indicated that corrosion of longitudinal reinforcement leads to cross-sectional damage, causing the redistribution of stress across the section and increasing long-term deformation, ultimately resulting in prestress losses. Meanwhile, stirrup corrosion leads to an initial increase in prestress due to expansion forces when the degree of corrosion is not so high, but finally it will also lead to a degradation of mechanical performance. [ABSTRACT FROM AUTHOR]

This paper investigates the efficacy of ultra-high-performance concrete (UHPC) jacketing as an option for seismic retrofit (repair or strengthening) of structural components that have been damaged by reinforcement corrosion. Previous work has illustrated that UHPC cover fully mitigates corrosion in the absence of service cracks and significantly reduces the corrosion rate in the case of preexisting cracks. In the present experimental study, cover replacement by UHPC is used to repair and strengthen corroded columns. Six lap-spliced columns designed based on pre-1970s design standards were constructed and subjected to artificial corrosion. Parameters of the investigation were: a) the aspect ratio of the specimens; b) the bar size (to account for the effect of bar diameter loss on bond); and c) the condition of the specimen (repair or strengthening after damage due to application of simulated seismic load to assess the effectiveness of retrofitting corroded components, even after having endured earthquake damage). The results show that thin UHPC jackets replacing conventional concrete cover suffice to impart a significant increase in strength and ductility of the columns. The jackets also endow the corroded and unconfined lap splices with significant force and deformation development capacity, thus alleviating a source of excessive column flexibility in existing construction. [ABSTRACT FROM AUTHOR]

Monitoring corrosion in aircraft structures through nondestructive testing is crucial for maintaining long-term aircraft serviceability. Corrosion monitoring is particularly challenging when corrosion damage is situated on internal surfaces of multilayer aircraft structures. The eddy current method is one of the most promising techniques for detecting and measuring such subsurface corrosion damage without direct contact or disassembly. However, due to their low sensitivity traditional eddy current probes with coaxial coils are not well suited for detecting corrosion damages of the local type, such as pitting or corrosion pits, in multilayer aircraft structures. This study tested the use of low-frequency eddy current probes of the double-differential type, characterized by 8 and 10 mm operational diameters, in detecting and measuring hidden corrosion damages of this local type. Such corrosion damages were simulated by means of flat-bottomed drilled holes of differing diameters and depths (or different diameters and residual thicknesses of the inspected sheet in the damaged area). The signals from the eddy current probes were evaluated in the complex plane using a universal eddy current flaw detector. The correlations between the amplitude and phase of the eddy current signal and depth of location of the local corrosion damages were analyzed. Results indicate that it is possible to estimate the residual thickness of the skin in locally corroded areas by measuring the eddy current signal phase, independently of the local corrosion damage diameter (size), providing useful information for residual service life determination. [ABSTRACT FROM AUTHOR]

Titanium alloys with high strength and good corrosion resistance have become one of the critical bearing structural materials in marine engineering. But in service, corrosion fatigue would occur under the synergetic action of cyclic external load and corrosion environment, threatening the safety of components. In this study, compared with low-cycle fatigue in laboratory air, the low-cycle corrosion fatigue deformation mechanism and fracture characteristic of the Ti-6Al-4V-0.55Fe alloy were investigated in 3.5% NaCl corrosion solution under selected stress amplitudes. The results showed that under low stress amplitude, corrosion fatigue was determined by fatigue damage and corrosion damage, causing a reduction in fatigue life. The local stress concentration caused by corrosion pits and dislocations pile-up accelerated the initiation of fatigue cracks, and other corrosion behavior including crevice corrosion promoted fatigue crack propagation; the corrosion solution increased the surface damage. While under high stress amplitude, due to the short contact time between the sample and solution and higher applied stress, the fatigue life is determined by fatigue damage caused by multiple slips. [ABSTRACT FROM AUTHOR]

In regions characterized by the challenging combination of brine corrosion in the salt lakes and river sand with alkali silica reaction (ASR) activity in areas of the Northwest, high-performance concrete (HPC) formulated with high-volume composite mineral admixtures as ASR suppression measures has been preferred for civil engineering structures in the region. This study investigates the splitting tensile strength, corrosion products, microscopic structure characteristics, and mesoscopic mechanical mechanisms of splitting failure of such HPC under 10-year corrosion from salt lake brine. The relationship between mechanical properties and corrosion damage, as well as the characteristics of internal crack propagation paths and failure mechanisms of HPC under splitting load, are explored. The findings reveal that as the alkali content within HPC rises, corrosion damage intensifies, resulting in a reduction in splitting tensile strength. Moreover, a linear association between mechanical properties and corrosion damage is observed. Microscopic structural analysis and numerical simulation of the splitting failure process of HPC elucidate that while the substantial presence of mineral admixtures effectively suppresses the ASR risk associated with alkali-reactive aggregates in concrete, uneven ASR gel products persist. These discontinuous micro-fine interface cracks induced by the gel products and the cracks induced by the gel products around the selective alkali-active aggregate particles distributed in the local area are the initiation sources of mortar cracks in HPC splitting failure. In terms of the overall failure state observed during the concrete splitting process, mortar cracks manifest two distinct extension paths: along the coarse aggregate interface and directly through the aggregates themselves. Notably, a greater proportion of coarse aggregates are directly penetrated by mortar cracks, as opposed to the number of interface failures bypassing coarse aggregates. More importantly, the above work establishes a theoretical reference in three dimensions: macroscopic, mesoscopic, and microscopic, for studying concrete corrosion damage in complex environments such as salt lake brine corrosion and ASR inhibition. [ABSTRACT FROM AUTHOR]

In order to investigate the impacts of corrosion damage on the seismic performance of recycled aggregate concrete (RAC) columns, the hysteretic behavior of the corroded RAC columns was studied through quasistatic tests and numerical analyses. The main parameters included different corrosion ratios, axial load ratios (ALR), and stirrup ratios. The results revealed that there were no significant differences in the carrying and deformation capacities of the corroded RAC column compared with the corroded NAC column. Under electrochemical chloride erosion conditions, the corrosion ratios of stirrups were on average 44.6% higher than those of longitudinal bars, and the crack widths of columns with different corrosion ratios varied little, ranging from 0.1 to 0.5 mm. Under a relatively low corrosion ratio (within 10%), the corrosion had a minor impact on the horizontal carrying capacity, but the deformation capacity of the corroded columns decreased with increasing corrosion ratio and ALR. The coupling effect of a high ALR and a high corrosion ratio could exacerbate the detrimental impact of corrosion, and special attention should be given to columns with an ALR exceeding 0.3 and a corrosion ratio exceeding 10%. In addition, the seismic performance of the corroded structure could be effectively simulated through the finite element model based on the modified corrosion model of the materials. [ABSTRACT FROM AUTHOR]

During long-term operation, oil and gas pipelines are often subjected to corrosion caused by complex environmental factors, which can lead to serious safety incidents. Therefore, accurately assessing the extent of corrosion damage and predicting the remaining life of pipelines has become a critical issue in the safety management of oil and gas pipelines. This paper aims to propose a high-precision corrosion rate prediction model and, based on this model, provide an accurate evaluation of the pipeline’s remaining life to enhance the operational safety and reliability of oil and gas pipelines. First, the MFO-LSSVM model is employed to precisely predict the corrosion rate of oil and gas pipelines. This model combines the Moth-Flame Optimization (MFO) algorithm and Least Squares Support Vector Machine (LSSVM), which significantly improves the prediction accuracy under complex environmental conditions. Building on this, a combination of Long Short-Term Memory (LSTM) and Deep Neural Networks (DNN) is used to predict the remaining life of the pipelines, capturing the time-dependent and nonlinear characteristics of the corrosion rate. Experimental results demonstrate that the MFO-LSSVM model achieves outstanding accuracy in corrosion rate prediction, with a root mean square error (RMSE) of 0.0023 and a mean absolute error (MAE) of 0.17%. For the remaining life prediction, the LSTM-DNN model shows a mean square error (MSE) of 0.0004 and a coefficient of determination (R2) of 0.9999, significantly outperforming other individual models and closely aligning with the actual values. This multi-stage prediction framework effectively enhances the model’s robustness and accuracy in complex environments. The innovation of this study lies in the development of a multi-stage prediction framework combining the MFO-LSSVM and LSTM-DNN models. The MFO-LSSVM model provides highly accurate corrosion rate predictions, while the LSTM-DNN model captures the time-evolution and nonlinear effects, leading to improved precision in corrosion damage assessment and remaining life prediction. This approach effectively overcomes the limitations of traditional models in complex environments and offers both theoretical support and practical value for the safety management of oil and gas pipelines.

Dry Dock No. 1 of Shanghai Shipyard has been in disrepair after the relocation of the shipyard. The composite-steel-sheet-pile dock walls have been corroded to a certain extent, and the under-drained system behind the wall failed. In order to explore the bearing performance of the corroded composite steel sheet pile dock wall during the recent docking of ancient ships and the subsequent construction of the museum, numerical models of the dock and steel sheet pile dock wall were established, and their displacements, internal forces, and local stresses in the corroded area were obtained. It is concluded that the composite steel sheet pile is temporarily in the strength safety state, and can withstand the load generated by the ancient ship docking in the short term. When the depth of rust pits reaches 4.6 mm, it will be difficult for steel sheet piles to meet the bearing capacity requirements. It is suggested that steel sheet piles should be reinforced and repaired within 7 years after rust detection, and the rust prevention system should be re-established to ensure the safety of the dock structure during subsequent engineering construction.

In regions characterized by the challenging combination of brine corrosion in the salt lakes and river sand with alkali silica reaction (ASR) activity in areas of the Northwest, high-performance concrete (HPC) formulated with high-volume composite mineral admixtures as ASR suppression measures has been preferred for civil engineering structures in the region. This study investigates the splitting tensile strength, corrosion products, microscopic structure characteristics, and mesoscopic mechanical mechanisms of splitting failure of such HPC under 10-year corrosion from salt lake brine. The relationship between mechanical properties and corrosion damage, as well as the characteristics of internal crack propagation paths and failure mechanisms of HPC under splitting load, are explored. The findings reveal that as the alkali content within HPC rises, corrosion damage intensifies, resulting in a reduction in splitting tensile strength. Moreover, a linear association between mechanical properties and corrosion damage is observed. Microscopic structural analysis and numerical simulation of the splitting failure process of HPC elucidate that while the substantial presence of mineral admixtures effectively suppresses the ASR risk associated with alkali-reactive aggregates in concrete, uneven ASR gel products persist. These discontinuous micro-fine interface cracks induced by the gel products and the cracks induced by the gel products around the selective alkali-active aggregate particles distributed in the local area are the initiation sources of mortar cracks in HPC splitting failure. In terms of the overall failure state observed during the concrete splitting process, mortar cracks manifest two distinct extension paths: along the coarse aggregate interface and directly through the aggregates themselves. Notably, a greater proportion of coarse aggregates are directly penetrated by mortar cracks, as opposed to the number of interface failures bypassing coarse aggregates. More importantly, the above work establishes a theoretical reference in three dimensions: macroscopic, mesoscopic, and microscopic, for studying concrete corrosion damage in complex environments such as salt lake brine corrosion and ASR inhibition.

Titanium alloys with high strength and good corrosion resistance have become one of the critical bearing structural materials in marine engineering. But in service, corrosion fatigue would occur under the synergetic action of cyclic external load and corrosion environment, threatening the safety of components. In this study, compared with low-cycle fatigue in laboratory air, the low-cycle corrosion fatigue deformation mechanism and fracture characteristic of the Ti-6Al-4V-0.55Fe alloy were investigated in 3.5% NaCl corrosion solution under selected stress amplitudes. The results showed that under low stress amplitude, corrosion fatigue was determined by fatigue damage and corrosion damage, causing a reduction in fatigue life. The local stress concentration caused by corrosion pits and dislocations pile-up accelerated the initiation of fatigue cracks, and other corrosion behavior including crevice corrosion promoted fatigue crack propagation; the corrosion solution increased the surface damage. While under high stress amplitude, due to the short contact time between the sample and solution and higher applied stress, the fatigue life is determined by fatigue damage caused by multiple slips.

In order to investigate the gradual change law of vibration characteristics of steel truss structures under the influence of fatigue loading and uniform corrosion, this study combines the nonlinear cumulative fatigue damage rule, corrosion depth theory, and structural residual performance theory to establish a multi-level gradually changing performance transfer model. The relationship between structural performance and damage behavior is revealed, and a numerical analysis method for the gradual change phenomenon of vibration characteristics of steel truss structures is provided. A two-dimensional finite element analysis framework for gradual changes in vibration characteristics in steel truss structures has been developed and analyzed for a steel truss girder bridge. The results show that the correlation terms of vibration characteristics gradually decay with the increase of operation time, and the degree of decay is related to the severity of fatigue damage or corrosion damage, with the overall trend exhibiting a three-stage change.

The problems of non-equilibrium and nonlinear processes in the evaluation of reinforced concrete structural systems robustness potential in ultimate states are considered. The definition of concept of “robustness exposition” is given for a quantitative assessment of the robustness potential. A calculation model based on the generalization of the well-known classical relationship between the current relative deficit change rate of the reinforced concrete stress-strain state with respect to each fixed time value is proposed to describe in time non-equilibrium processes of structural materials force resistance depending on the mode and level of loading. On the basis of the linear creep theory, aging materials, an algorithm was developed to determine the measure of creep, corrosion-damaged concrete and reinforced concrete and to determine the parameter “robustness exposition” of a reinforced concrete statically indeterminate structural system, taking into account non-equilibrium and nonlinear processes of its deformation in time. An example of a single-span rigidly clamped reinforced concrete beam calculating the robustness potential from the position of a special limiting state criterion is considered.

This paper addresses the evaluation of the effects of corrosion on the performance of ageing steel industrial infrastructures. A novel probabilistic risk assessment method is presented with respect to a case study of a real petrochemical structure located in an atmospheric environment with high severity of corrosion. The results of damage assessment derived from refined fragility analyses revealed that long-term corrosion mass reduction can increase the probability of damage to the structure by an average of 40%. Furthermore, the risk analysis demonstrated that the annual failure rate of the corroded structure is at most 2.80 times that of the uncorroded counterpart. The vulnerability analysis showed that the difference in annual repair costs between corroded and uncorroded cases gradually increased as the severity of ground motion raised. Moreover, the results of comprehensive and refined nonlinear analyses indicated that the corroded structure after 50 and 100 years can increase the likelihood of causing corrosion repair costs in the first year by about 40 and 60 times, respectively. The evaluation of the ratio of construction to maintenance and retrofitting was also carried out; it was based on innovative retrofitting measures with the use of Carbon Fibre Reinforced Polymers for steel structures. The findings illustrated in the present numerical study can help owners and insurance companies to predict more reliably maintenance and repair costs, thus they can provide an efficient roadmap for industrial asset management. [ABSTRACT FROM AUTHOR]

A fragment of a pipe from a chromium-manganese steel of type 12Kh15G9ND (AISI 201) is studied after 1.5 years of operation in an apartment building. The chemical composition of the steel is determined. The Vickers hardness of straight and curvilinear parts of the pipe is measured. The temperatures Ms and Md of martensitic transformations are computed. The macrostructure and the microstructure of the steel are studied. Places of through corrosion damage and causes of their formation in hot water supply (HWS) pipes are analyzed. A method of scratch testing is suggested for assessing the surface condition. The adhesive properties of the coating are estimated. It is inferred that steel 12Kh15G9ND is suitable for service in HWS systems and that total replacement of the chromium-nickel steel in pipelines by a chromium-manganese corrosion-resistant one requires further study. [ABSTRACT FROM AUTHOR]

This paper presents the problem of assessing degradation process of a selected railway steel bridge in the final period of its operation. Changes in the technical condition of the analysed steel railway bridge in time on the basis of special inspections carried out in 2009–2014 are investigated. The methodology for conducting steel railway bridge assessment in an engineering approach is being presented taking into account conclusions and results from the subsequent special inspections. Moreover, the results of fatigue analysis and assessment of the steel railway bridge, which was put in service in 1933 are discussed. In order to conduct the fatigue analysis and assessment, the deflection of the structure under moving load is measured, as well as the geometry of the structural elements in the support zone is verified. The impact of rolling stock, in particular heavy freight transport, on the bridge degradation process is indicated. It is found that dynamic effects induced by the freight rolling stock reveal a big influence on the rate of fatigue damage process of the bridge. Additionally, the degradation of the considered railway bridge due to the effect of track misalignment is taken into account. Furthermore, the impact of corrosion damage and fatigue on the distribution of stresses in the bridge structure is also discussed. [ABSTRACT FROM AUTHOR]

A methodology for reliability analysis of reinforced concrete (RC) beams strengthened with ultra high-performance fibre reinforced concrete (UHPFRC) tensile layers is presented. The proposed methodology includes stochastic stress-block analysis of a section, assuming a perfect bond between the RC beam and the UHPFRC layer. Annual reliability analysis of the RC beam before and after the strengthening operation is conducted. Deterioration induced by chloride corrosion is incorporated into the analysis via a chloride induced corrosion model based on Fick’s law of diffusion and described stochastically to account for the epistemic uncertainty in the time to corrosion initiation and rate of corrosion. A plot for determining the required thickness of the UHPFRC tensile layer to upgrade to the required reliability level is also given, considering the time from construction to when the strengthening operation is conducted. The proposed approach is easy to apply for routine practice.

Fire and corrosion change the bond behavior and bearing capacity of marine concrete structures, and the multi-hazard coupling mechanism is unclear. Therefore, this paper aims to establish the relationship between the flexural capacity and bond performance of corroded beams by flexural and sustained load pullout tests. Furthermore, this study verifies the accuracy of corroded beams moment calculation equation considering the bond behavior. The sustained load pullout and flexural tests are performed under varying corrosion degrees. The test results indicate that the reinforcement slip and mid-span deflection of beams increase with increasing high temperature. Heating to 800 ℃ results in a slip of 2.2 mm, and the damage degree rises with increased temperature and corrosion degree. The damaged bond strength of corroded specimens with different temperatures, embedded lengths, and rebar diameters is subsequently calculated. The influence coefficient of corrosion and temperature on bond strength is determined using the damage principle, and the influence coefficient of bond performance on the moment-bearing capacity is also calculated. The bond strength calculation formula is obtained based on the nonlinear superposition principle, and a moment-bearing formula considering bond performance under fire is formulated. Finally, using the finite element method, five concrete beams under fire is simulated, and establish a nonlinear spring to reflect the bond-slip relationship, achieving a simulated deflection check for corroded beams under coupling action between fire and fatigue load. The finite element verification results of corroded beams under fire, using the unified bond-slip model, are in close agreement with the experimental results. • The interfacial damage regular of marine concrete structures was studied under multi-hazard conditions. • The moment bearing capacity considering the bond action is calculated under the multi-coupling action. • A finite element analysis method for susceptible damage beam is established. [ABSTRACT FROM AUTHOR]

One of the most famous high-rise structures in the world, the Moscow Radio Tower, was built in 1919-1922. Over more than a century of operation, corrosion damage formed in the elements, which brought the tower to an emergency state. Today the tower is located in a dense urban development, any abnormal situation with the structures poses a danger to the surrounding buildings. Due to the structural features of the structure, restoration works can be executed only when its elements are unloaded by suspending the radio tower on an additional support structure. In order to ensure safety during the works, it is necessary to guarantee the transmission of the force from the weight of the radio tower along the axis of the inclined struts. For this purpose, a special beam and its connection nodes to the columns were developed and tested. The nodes were used in the course of emergency works, which consist in providing partial support of the radio tower on a specially erected support tower, which eliminates the danger of tower collapse, but does not reduce the emergency condition of the structure. Urgent measures are required to bring the supporting structures of the tower to a serviceable technical condition.

Based on analytical and experimental data, the durability properties of reinforced concrete and reinforcement necessary for modeling degradation and calculating the durability of reinforced concrete elements under various types of corrosion damage are substantiated. A probabilistic model has been developed for predicting and assessing the durability and reliability of reinforced concrete elements, taking into account the statistical variability of design parameters and the kinetics of degradation processes during long periods of operation. An analysis of the method for calculating and predicting the durability of reinforced concrete elements based on deterministic probabilistic models of degradation of structural elements operating under aggressive environmental influences has been carried out. The necessary assessment of the stress-strain state of reinforced concrete structures under conditions of long-term operation in aggressive environments as a result of corrosion damage is given, and their residual life is studied, taking into account the reduction in the cross-sectional area of concrete and reinforcement

The application of artificial neural network approaches has been successful in solving complex civil engineering problems, such as damage detection and structural member capacity prediction. Within the context of the present study, corrosion has become the main factor limiting the safety and load-carrying capacity of aging steel bridge girders. Corrosion damage is often most severe near girder ends in simple-span bridges due to deck joint leakage and the pooling of water and de-icing salts. In addition to empirical methods, Finite Element (FE) analysis is typically used to evaluate the residual bearing capacity of corroded steel girders. However, it is prohibitively challenging and time-consuming to create an accurate FE model of a corroded girder due to the irregular nature of corrosion damage. Resultantly, corrosion damage is often reduced to uniform section loss, which leads to unreliable estimates of a girder’s residual bearing capacity. Researchers have proposed methodologies for modeling irregular corrosion damage, but these approaches require a high level of expertise. A comprehensive method is therefore required to efficiently estimate the residual bearing capacity of a corroded steel girder. This paper proposes the use of neural networks to predict the residual bearing capacity of corroded steel plate models as a first step in estimating the residual bearing capacity of an in-service girder. Neural networks are constructed and trained on a database built from FE analysis performed on steel plate models with realistic representations of corrosion damage. This study assesses the ability of neural networks to estimate the compressive capacity of corroded steel plates since plate girders are one of the most prevalent girder forms in steel bridges. Three types of neural networks are trained to predict the compressive capacity of corroded plate models, including a multilayer perceptron (MLP), a convolutional neural network (CNN), and a hybrid MLP-CNN model. The average mean absolute percentage errors (MAPE) for the three models are 20.65%, 11.46%, and 9.64%, respectively. The results of this study demonstrate the potential of using neural networks to predict the compressive capacity of corroded plates efficiently and accurately, which could facilitate proactive maintenance decision-making for aging bridges.

Among other fields, climate change has a great influence on metal corrosion that reduces the durability and reliability of steel structures. A time-dependent reliability analysis includes time-dependent climate scenarios and deterioration processes as well as random variables, material properties, and dimensions. The extent of corrosion damage is calculated by tracking the evolution of the corrosion process using Monte Carlo simulations. The current paper presents a time-dependent reliability assessment of a continuous I-shaped steel beam, considering the corrosion effects of climate change in Vietnam. The results showed that the safety probability of a continuous steel beam considering metal corrosion from the pristine to 100 years reduces from 96.77% to 63.08%. These findings can be used to assess and provide a cost-technical analysis of climate adaptation measures. [ABSTRACT FROM AUTHOR]

Abstract—The possibility of determining the degree of corrosion damages of various types by the eddy current control method using a laid-on probe is considered. A two-frequency method is proposed for separate control of the degree and type of corrosion damages. A method for selecting frequencies for monitoring is described. The developed method of estimating the degree of corrosion damage is experimentally tested. [ABSTRACT FROM AUTHOR]

A methodology for reliability analysis of reinforced concrete (RC) beams strengthened with ultra high-performance fibre reinforced concrete (UHPFRC) tensile layers is presented. The proposed methodology includes stochastic stress-block analysis of a section, assuming a perfect bond between the RC beam and the UHPFRC layer. Annual reliability analysis of the RC beam before and after the strengthening operation is conducted. Deterioration induced by chloride corrosion is incorporated into the analysis via a chloride induced corrosion model based on Fick's law of diffusion and described stochastically to account for the epistemic uncertainty in the time to corrosion initiation and rate of corrosion. A plot for determining the required thickness of the UHPFRC tensile layer to upgrade to the required reliability level is also given, considering the time from construction to when the strengthening operation is conducted. The proposed approach is easy to apply for routine practice. [ABSTRACT FROM AUTHOR]

• Unveiled the scattering phenomenon resulting from the intricate interaction between a bounded ultrasonic beam and a thin-walled shell submerged in fluid. • Showcased exceptional sensitivity in assessing damage in thin-walled shells using the scattering method. • Successfully identified inner-wall corrosion damage in thin-walled structures through precise experimental measurements. • Presented a reliable tool for monitoring the structural integrity of thin-walled components. This paper introduces an ultrasonic detection methodology specifically designed to assess damage in thin-walled cylindrical shells, which crucially relies on the interaction between a bounded ultrasonic beam and a thin-walled cylindrical shell immersed in fluid, considering both water-filled and air-filled cavities. Initially, we derive the scattered sound field expression for a bounded ultrasonic beam obliquely striking the shell. Subsequently, through finite element simulations and experimental verification, we observe that when the incident bounded beam is emitted at the critical angles defined in this study, early damage significantly enhances the received sound pressure amplitude detected by a symmetrically positioned receiver. Notably, a mere 5 % decrease in the shell's elastic modulus leads to a notable 233.69 % increase in the area under the amplitude-frequency curve of the received sound pressure for water-filled cavities and a remarkable 642.85 % surge in area for air-filled cavities. Experimental data further validates the sensitivity of this method towards varying corrosion damage states. This approach combines the reliability of linear ultrasonic methods with the enhanced sensitivity of nonlinear ultrasonic techniques, offering a significant advancement over traditional ultrasonic detection methods for inspecting cylindrical shells. The proposed assessment method holds immense potential in providing novel insights for inspecting cylindrical shells in practical applications. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the seismic performances of circular hollow section (CHS) T-joints with different regions of corrosion damage. A total of seven CHS T-joint specimens with various corrosion degrees were applied to conduct the quasi-static tests of brace axial cyclic loading, and the effects of corrosion damage on the hysteresis behavior and failure mode were discussed. Experimental results indicated the brace corrosion only had a slight influence on the seismic performance of CHS joints, while the corrosion difference on two sides of the brace might cause an additional bending moment and damage accumulation to accelerate the plastic collapse of the connection zone. Compared with the corrosion on the brace, the resistance of CHS joints was more susceptible to the corrosion located in the chord wall, resulting in the axial cyclic carrying capacity and stiffness of CHS joints significantly decreasing with the increase of chord corrosion level. However, the increasing corrosion on the chord would affect the final fracture behavior and fracture position, so the total energy dissipation and deformation of CHS joints presented a complicated and nonlinear degradation trend. In addition, corrosion damage simultaneously had an impact on reducing the bending capacity of the chord, and this phenomenon not only caused the differences between the degradation rates of axial tensile and compressive strength of CHS joints but also affected the failure mechanism and local deformation of CHS joints under the brace axial cyclic loading. [Display omitted] • Seismic performances of corroded CHS T-joints under brace cyclic axial load were investigated. • A method calculating the external corrosion depth of steel tubes was proposed to analyze the corrosion levels. • The effect mechanism of different regional corrosion on failure mode and hysteresis curve of CHS T-joints were analyzed. • The feasibility of the existing equations predicting the carrying capacity of corroded CHS T-joints was discussed. [ABSTRACT FROM AUTHOR]

An experimental program was conducted to develop a methodology to evaluate the floor condition of the aboveground storage tanks (ASTs). The proposed methodology applies image analysis to the data captured during acoustic emission (AE) monitoring conducted to assess corrosion activity on the AST floor. AE characteristics and source localization were dynamically monitored during normal AST operation. Based on geometric features of the corrosion-related AE activity map on the AST floor, a box count method was used to determine fractal dimension. The remaining thickness of the AST floor is determined relative to its thickness at fabrication as a function of AE activity intensity, which in-turn is used to estimate the total floor material loss due to corrosion. The results showed that fractal dimension values of the corroded AST floor fit well to corresponding values of material loss and therefore each can be used in conjunction with AE parameters to generate a corrosion risk index. The study provides a new approach for AE data analysis to establishing a cost-effective maintenance strategy for AST owners based on risk probability to conduct operation shut down and repairs on time before hazardous situations. [ABSTRACT FROM AUTHOR]

This research explored the corrosion effect of NaCl solution on the surface quality of AZ31 magnesium alloy. Cubic-shaped specimens were immersed in standard 3.5% NaCl solution for 1, 2, 3, and 4 hours. The size of corrosion pits, fatigue crack propagation area, and surface topology were characterized. Fatigue tests were carried out on pre-corroded AZ31 specimens under different stress amplitudes. The correlation between the corrosion time and the virtual crack size was obtained. The virtual crack size is a new parameter that can relate the corrosion to the fatigue life. A new model was proposed to map the surface topology on the virtual crack size of pre-corroded AZ31 magnesium alloy. The fatigue life of 1-4-hour pre-corroded AZ31 specimens could be predicted accurately by this new model. The Levenberg-Marquardt and curve-fitting methods were used to obtain the constant parameters. The relative error between the crack size corresponding to the immersion time and the virtual crack size calculated by the proposed model was less than 1%. [ABSTRACT FROM AUTHOR]