Search

Digital data management for maintenance in offshore wind farms The DiMoWind‐Inspect research project explored the essential requirements for implementing digital methods in the maintenance of offshore wind turbines. Currently, data from all stages of the turbines' lifecycles are underutilized, leading to suboptimal maintenance actions being taken in terms of location, timing, and cost. A consistent structuring of previously often unstructured construction and maintenance data developed in the project enables their cross‐disciplinary, user‐specific availability. To accomplish this, the principles of the Reference Designation System for Power Plants RDS‐PP are applied. In this way, additional information, such as maintenance measures or defects, can be structured alongside components. The components of the structures are directly linked with information from inspections and other maintenance activities, following the Building Information Modeling approach. This allows for processing operational information about the condition of the structure and providing it for relevant calculations and assessments. As a use case, a two‐stage concept is presented, utilizing maintenance information to assess the fatigue life of a corrosion‐damaged structural detail in the support structure of an offshore wind turbine. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica 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.)

Fatigue damage represents a key failure mode in ship structures. Such damage typically begins at vulnerable points in the structure, like welded joints, stress concentration areas, and cracks. Cyclic loading, particularly from waves, encountered by ships during their operational life is a major cause of fatigue damage, which is the main focus of this study. There are various methods to address different sea state conditions, though they can sometimes be approximate. This paper aims to review the most commonly used methods to highlight their strengths and weaknesses and to provide essential background knowledge for developing reliable theoretical and numerical models for predicting the fatigue life of ship structures exposed to various sea states over their lifetime. The primary theoretical approaches discussed include energy spectral methods in both time and frequency domains, which are used to quantify wave-related energy and amplitude characteristics and evaluate wave loads for predicting the fatigue life of structures and welded joints. The discussion also covers the determination of cyclic stress in specific structural details of the hull girder and welded joints to identify the relevant maximum stress range for subsequent fatigue studies conducted using finite element analysis. [ABSTRACT FROM AUTHOR]

Riveted railway bridges with already long structural lives can still be commonly found in service in Europe. In light of their peculiarities, they are often prone to fatigue damage; nevertheless, very few prescriptions regarding fatigue assessment of these structures can be found in current European provisions. Within this framework, the present paper illustrates the advanced fatigue assessment of an Italian riveted railway bridge selected as a case study. For this purpose, multi-scale finite element modelling of the bridge was developed, and the most critical details were assessed through application of the advanced strain energy density (SED) method. The obtained outcomes were compared both with other studies in the literature and prescriptions from the current and upcoming versions of EN1993-1-9. [ABSTRACT FROM AUTHOR]

Purpose: Cancer-related fatigue (CRF) is challenging to diagnose and manage due to a lack of consensus on its definition and assessment. The objective of this scoping review is to summarize how CRF has been defined and assessed in adult patients with cancer worldwide. Methods: Four databases (PubMed, Embase, CINAHL Plus, PsycNet) were searched to identify eligible original research articles published in English over a 10-year span (2010–2020); CRF was required to be a primary outcome and described as a dimensional construct. Each review phase was piloted: title and abstract screening, full-text screening, and data extraction. Then, two independent reviewers participated in each review phase, and discrepancies were resolved by a third party. Results: 2923 articles were screened, and 150 were included. Only 68% of articles provided a definition for CRF, of which 90% described CRF as a multidimensional construct, and 41% were identical to the National Comprehensive Cancer Network definition. Studies were primarily conducted in the United States (19%) and the majority employed longitudinal (67%), quantitative (93%), and observational (57%) study designs with sample sizes ≥ 100 people (57%). Participant age and race were often not reported (31% and 82%, respectively). The most common cancer diagnosis and treatment were breast cancer (79%) and chemotherapy (80%; n = 86), respectively. CRF measures were predominantly multidimensional (97%, n = 139), with the Multidimensional Fatigue Inventory (MFI-20) (26%) as the most common CRF measure and “Physical” (76%) as the most common CRF dimension. Conclusion: This review confirms the need for a universally agreed-upon definition and standardized assessment battery for CRF. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) system provides valuable information for the fatigue assessment of existing rail-cum-road bridges. This paper aims to develop an effective fatigue assessment approach for the rail-cum-road bridge, Jiujiang Yangtze River Bridge, by utilising the SHM data, focusing on dynamic modal analysis, finite element model updating and fatigue assessment. First, the traffic load spectrum and modal characteristics of the bridge are investigated from the SHM data. A three-dimensional finite element model is constructed and then updated by using the measured modal data through the proposed regularised model updating method. Then, the updated numerical model is verified with the measured dynamic response data, which can be utilised for calculating stress response at critical structural components of the rail-cum-road bridge. Finally, an improved Corten-Dolan’s model is proposed to analyse the fatigue damage and structural reliability of the critical structural components of the bridge, taking into account the combined effects of train and highway vehicle loads. The results demonstrate that the proposed fatigue assessment method provides more reliable results for the rail-cum-road bridge by considering the combined effect of multi-level traffic loads and the non-linear fatigue damage accumulation. It is concluded that the short H-shaped suspender is identified as the most vulnerable structural member of the rail-cum-road bridge, and the remaining fatigue service life of the typical components of the bridge should meet the design requirement.

Fatigue damage represents a key failure mode in ship structures. Such damage typically begins at vulnerable points in the structure, like welded joints, stress concentration areas, and cracks. Cyclic loading, particularly from waves, encountered by ships during their operational life is a major cause of fatigue damage, which is the main focus of this study. There are various methods to address different sea state conditions, though they can sometimes be approximate. This paper aims to review the most commonly used methods to highlight their strengths and weaknesses and to provide essential background knowledge for developing reliable theoretical and numerical models for predicting the fatigue life of ship structures exposed to various sea states over their lifetime. The primary theoretical approaches discussed include energy spectral methods in both time and frequency domains, which are used to quantify wave-related energy and amplitude characteristics and evaluate wave loads for predicting the fatigue life of structures and welded joints. The discussion also covers the determination of cyclic stress in specific structural details of the hull girder and welded joints to identify the relevant maximum stress range for subsequent fatigue studies conducted using finite element analysis.

Muscle fatigue is a significant factor that affects the quality of performance during exercise. However, there is currently insufficient evidence of a thorough systematic review that describes the tools used to quantify fatigue in exercise performances. The purpose of this study was to provide a summary of the validity and reliability of the questionnaire scales used to assess fatigue and their potential applications. This review paper is based on a systematic search of the literature published between 2017 and 2023. The search was conducted in PubMed, Science Direct, and Google Scholar databases. The quality of the selected studies was scored using a Quality assessment checklist. Fifteen articles were included and all graded with strong quality. To measure how much fatigue felt in an exercise context, different subjective scales were used in each study. The Rating of Perceived Exertion (RPE) and Borg Scales are the most frequently used for the measurement of fatigue in exercise. All the scales had significant correlations with other instruments used to compare the effect of fatigue in each study. RPE was the best choice to assess physical fatigue since it has the highest correlation towards fatigue, and it is more simplified compared to the Borg Scale. [ABSTRACT FROM AUTHOR]

Riveted railway bridges with already long structural lives can still be commonly found in service in Europe. In light of their peculiarities, they are often prone to fatigue damage; nevertheless, very few prescriptions regarding fatigue assessment of these structures can be found in current European provisions. Within this framework, the present paper illustrates the advanced fatigue assessment of an Italian riveted railway bridge selected as a case study. For this purpose, multi-scale finite element modelling of the bridge was developed, and the most critical details were assessed through application of the advanced strain energy density (SED) method. The obtained outcomes were compared both with other studies in the literature and prescriptions from the current and upcoming versions of EN1993-1-9.

Sand waves are commonly formed on the sandy seabed of the continental shelf and characterized by their regular wave-like shape. When a submarine pipeline is laid on this type of seabed, it often experiences free spans due to the unevenness of the seabed. These free spans are particularly vulnerable to vortex-induced vibration (VIV) and the resulting fatigue damage, which have been identified as the primary causes of pipeline failures in offshore oil and gas exploration. This study examines the VIV and fatigue damage of free spans in a submarine pipeline in the Lufeng oilfield, which is located in a large area of sand waves. The assessment conditions encompass the as-laid empty state, the flooded state, and the operational state. Additionally, both the minimum and maximum lay tension are taken into account during the evaluation of VIV and fatigue. The VIV onset screening conducted revealed a considerable number of pipeline free spans exceeding the VIV onset span lengths under both temporary and operating conditions for the non-trench seabed. Furthermore, the analyses indicate that the pipeline does not meet the criteria for VIV fatigue on a non-trenched seabed. Consequently, a proposed solution of implementing a 1 m trench rectification measure for the seabed is recommended. The results demonstrate that this measure effectively mitigates the occurrence of VIV and subsequently reduces fatigue damage across all conditions. [ABSTRACT FROM AUTHOR]

Tunnel passing at high speed produces aerodynamic load on railway trains, which may bring about fatigue failure on the car body, and damages passenger comfort due to interior penetration of the alternating wave. In this work, the air suction experiment approaches were developed. It performs excellently through internal and external loading utilizing valve controlling strategies. It is validated with an in-transit vehicle test when the train runs through 3 different tunnel lengths. The relative deviation between simulation and vehicle tests goes no more than 5.0%. Research outcome indicates that the proposed method provides an important experiment means for passenger comfort and car-body fatigue behavior research. [ABSTRACT FROM AUTHOR]

Fatigue calculations of steel bridges are particularly vulnerable to inaccuracies in stress assessment. Their accurate evaluation ensures structural safety and can contribute to extending the remaining service life of many structures. The following study deals with the incorporation of measured data into fatigue assessment based on FE calculations using the trains operating on site. The bridge under study was equipped with a large number of strain gauges to capture the global and local effects of train passages. In addition, some strain gauges were placed on both rails to determine train speeds and axle forces. A detailed finite element model of the bridge was created and the strains caused by selected detected trains were blindly compared with measured values. Although a fairly good agreement was obtained for most strain gauges without the need for model updating, some sensors did not comply with the measured values. In order to achieve better agreement, a model update was performed. The authors concluded with a comparison of the original and updated models and the determined operating trains with regard to the fatigue calculations and discussed the added value. [ABSTRACT FROM AUTHOR]

This study proposes a novel approach to monitor the fatigue levels of construction rebar benders by measuring chemical biomarkers using sweat sensors. Fatigue resulting from dehydration and energy depletion can severely endanger the safety and health of construction workers. Sodium, lactate, glucose, and sweat rate were chosen as detectable biomarkers in this study, as their concentrations can indicate hydration status, energy consumption, and electrolyte balance, making them suitable for fatigue monitoring. The results were used to construct a fatigue model using supervised machine learning approaches. Construction rebar experiments were conducted while the sweat-based biosensors were applied to rebar workers to evaluate their fatigue with five different classifiers, demonstrating accuracy rates ranging from 71.43% to 96.43%. The results suggested that sweat-based biomarkers offer a noninvasive and accessible fatigue monitoring alternative. This can potentially help alleviate fatigue-related adverse ill effects like dehydration or cramping by enabling instant fluid or nutrient supply recommendations during construction manual tasks. It also provides valuable insights into the physiological effects of rebar work. Besides, this study presents a valuable model for predicting workers' fatigue levels, which could be applied in the construction industry to improve workers' safety and productivity. Furthermore, the study highlights the importance of maintaining appropriate hydration, nutrition, and electrolyte balance during physically demanding tasks like construction manual work. The study demonstrates that sweat biomarkers, including sweat rate, sodium, lactate, and glucose, can be utilized to assess fatigue among construction rebar workers. Sweat biosensors offer advantages of small size and non-invasiveness, making them suitable for a wide range of scenarios in both the construction industry and sports fields. Moreover, sweat rate and sodium levels can indicate hydration status, and their measurements can be used to recommend immediate fluid intake. Also, lactate and glucose are essential resources that sustain the body, and their measurements can suggest appropriate nutritional intake. These instant recommendations can alleviate the adverse effects of fatigue, consequently reducing fatigue levels. Thus, it is a promising methodology for enhancing the health and safety of the construction industry. In addition, the results of the study will be shared with construction companies, allowing them to introspect fatigue development and chalk out further interventions and policies to manage fatigue effectively. [ABSTRACT FROM AUTHOR]

Traffic loads have an important impact on long-term performance of buried urban pipelines due to generation of cyclic stress and fatigue damage. As a key task for pipeline fatigue assessment, the investigation of traffic-induced pipe stress and fatigue load spectrums is always a big challenge. Focusing on the metal pipelines buried under urban intersection, an integrated framework is proposed for fatigue assessment of the pipelines under traffic loads using video monitoring data acquired by the widespread surveillance cameras in cities. The computer vision algorithms and a quarter vehicle model are first employed to identify traffic loads. Analytical pipe-soil models are then developed to calculate pipeline stress and establish the traffic-induced fatigue load spectrums of buried pipelines, based on which the Monte-Carlo simulations are finally conducted to evaluate cumulative fatigue damage and fatigue reliability. A case study on a DN500 steel pipeline buried under an urban intersection demonstrates and validates the fatigue assessment procedure. The results can provide a basis for decision support regarding maintenance and replacement of urban pipelines. [ABSTRACT FROM AUTHOR]

Fatigue is a leading cause of structural failure; however, monitoring and prediction of damage accumulation remains an open problem, particularly in complex environments where maintaining sensing equipment is challenging. As a result, there is a growing interest in virtual loads monitoring, or inferential sensing, particularly for predicting strain in areas of interest using machine learning methods. This paper pursues a probabilistic approach, relying on a Gaussian process (GP) regression, to produce both strain predictions and a predictive distribution of the accumulated fatigue damage in a given time period. Here, the fatigue distribution is achieved via propagation of successive draws from the posterior GP through a rainflow count. The establishment of such a distribution crucially accounts for uncertainty in the predictive model and will form a valuable element in any probabilistic risk assessment. For demonstration of the method, distributions for predicted fatigue damage in an aircraft wing are produced across 84 flights. The distributions provide a robust measure of predicted damage accumulation and model uncertainty. [ABSTRACT FROM AUTHOR]

The fatigue safety of cable-girder anchorage structures in cable-stayed bridges under long-term service has attracted much attention. For bridges located in seasonally cold regions, the effect of low-temperature environments should be considered when evaluating fatigue performance. Using the Heilongjiang Bridge in China as a case study, a room-temperature fatigue test with a numerical simulation that considers the low-temperature effect on both load effect and fatigue resistance was proposed. A fatigue test with increased testing load amplitude was performed on a 1:3.75 ratio specimen. After 3.2 million loading cycles and using an acoustic emission technique, no fatigue crack was observed in the anchorage structure. The extended finite element method was then adopted to analyze the anchorage zone's fatigue crack initiation position and propagation path. Finally, based on the fatigue characteristics of bridge steel, the fatigue resistance to the crack propagation of the vulnerable area was evaluated under three different service conditions. The results show that the fatigue performance of the anchorage zone at low temperatures is sufficient. Moreover, this paper provides a more widely applicable and cost-effective approach for the fatigue evaluation of steel bridges. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe 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.)

Situation awareness (SA) is the ability to recognize and understand the current state of the environment and predict state changes in the near future. The level of SA is an important basis for determining whether the operator's state is competent for the current complex task. Taking a simulated flight task as an example, the study aims to explore the influence of the mental fatigue state induced by the cumulative effect of time on the level of SA in a complex operating environment. In this study, the data of fatigue self-assessment, electrocardiogram, and eye physiological of ten participants were collected in the simulated flight tasks, and the SA scores of the participants' perception, understanding and prediction levels were evaluated using probe technology. The experimental results show that the scores of perception level of SA was basically not affected by the mental fatigue state caused by the accumulation effect, while the understanding level and prediction level both showed a decline in scores. The results of the study are of reference value for further exploring the multilevel SA level changes under the time accumulation effect in complex tasks and developing reliable human‒machine intelligence systems. [ABSTRACT FROM AUTHOR]

The use of 7000 aluminum alloys has an important role in future lightweight structures in the field of mobility due to the low density and high strength. However, these alloys can only be fusion welded to a limited extent because welding defects can rarely be prevented. For this reason, investigations are carried out to identify the most suitable welding parameters for two processes: laser beam and magnetic pulse welding. Herein, laser beam welding is successfully used to manufacture a roll‐formed and longitudinally welded pipe made of AA7075 and joined by magnetic pulse welding with a 3D‐printed lug‐tube made of AlSi10Mg. The fatigue strength of these pipe joints and of laser beam welded butt joint specimens is determined using load‐controlled fatigue tests. For the characterization of the specimens, cross sections are prepared and examined metallographically, which reflect the local weld seam geometry in the joining area. A fatigue assessment is made using linear‐elastic approaches. The reference radius concept is applied to map the influence of geometric notches on the fatigue strength, assuming linear‐elastic stress–strain behavior. It is shown that the recommended notch stress fatigue class FAT 178 (von Mises stress) can be applied for a safe and reliable fatigue assessment. [ABSTRACT FROM AUTHOR]

The endurance limit of structural mechanical components is affected by the residual stress state, which depends strongly on the manufacturing process. In general, compressive residual stresses tend to result in an increased fatigue strength. Post-manufacturing processes such as shot peening or vibratory finishing may achieve such a compressive residual stress state. But within complex components, manufacturing-process-based imperfections severely limit the fatigue strength. Thus, the interactions of imperfections, residual stress state and material strength are key aspects in fatigue design. In this work, cast steel and aluminium alloys are investigated, each of them in vibratory finished and polished surface condition. A layer-based fatigue assessment concept is extended towards stable effective mean stress state considering the elastic–plastic material behaviour. Murakami's concept was applied to incorporate the effect of hardness change and residual stress state. Residual stress relaxation is determined by elastic–plastic simulations invoking a combined hardening model. If the effective stress ratio within the local layer-based fatigue strength is evaluated as critical distance value, a sound calculation of fatigue strength can be achieved. Summing up, the layer-based fatigue strength design is extended and features an enhanced understanding of the effective stabilized mean stress state during cyclic loading. [ABSTRACT FROM AUTHOR]

Petrochemical equipment is subjected to frequent discontinuous operation and underwent alternate loads, leading to fatigue failure of metal structure. Due to the fact that petrochemical equipment operates in a harsh environment, it's necessary to assess the fatigue state of metal materials to ensure production safety. The residual stress of metal materials is closely related to the fatigue evolution. Physical model is unable to express the possibility of the evolution of residual stress. Data-driven model requires large-scale data to optimize the model and may not conform to the laws of physical evolution. Therefore, this paper proposes a probabilistic model integrating physical model and Gaussian Process Flow (GPF) for fatigue assessment of metal structure of petrochemical equipment under scarce data. Firstly, different evolutionary trajectories with stochastic parameters are obtained by applying stochastic differential equation (SDE). The uncertainty of SDE is assessed by Gaussian process (GP). Then, from the perspective of a particle filter, the physical model is combined to develop a fusion-driven model to infer the importance of the residual analysis. An example of an irreplaceable metal material in petrochemical equipment is studied to demonstrate the effectiveness of this model. The model proposed could provide a promising solution for preventing fatigue failure at petrochemical processing facilities. [ABSTRACT FROM AUTHOR]

Objectives. Smartphone-based gait assessment provides a novel method to evaluate fatigue. This study aimed to examine self-reported fatigue and gait parameters recorded using a smartphone before and after an 8-h work day in bank workers, and identify the relationship between self-reported fatigue and gait parameters. Methods. One hundred bank workers (aged 20–45 years) were tested before and after an 8-h work day using a reaction time test, self-reported fatigue scale and gait test. Spearman correlation coefficient analysis and partial least squares regression were used to identify the relationship between self-reported fatigue and gait parameters. Results. Reaction time and self-reported fatigue increased significantly after work. Gait parameters (step frequency, minimum acceleration, acceleration root mean square, step regularity and step counts) decreased; step time and step time variability increased significantly (p < 0.05). We found a significant correlation between changes (Δ) for Δwork engagement and Δstep frequency (r = −0.20, p < 0.05), Δwork engagement and Δstep time (r = 0.21, p < 0.05), and Δwork tasks and Δstep symmetry (r = −0.20, p < 0.05). Conclusion. This study suggests that step frequency, step time and step symmetry measured using a smartphone have the potential to be used as predictors of work fatigue. [ABSTRACT FROM AUTHOR]

The research on the fatigue of front-line employees in coal mines is conducive to the realization of coal mine safety production and is of great significance to reduce unsafe accidents. In order to explore the effect of different shift systems on the fatigue of front-line employees in coal mines, a fatigue assessment model based on EEG signals was constructed by tracking investigation and EEG signal acquisition of 25 employees in different shift systems in Hongliulin Coal Mine. The effects of “three eight-hour shifts” and “four six-hour shifts” on the fatigue of front-line employees in coal mines are analyzed from the characteristics of fatigue. The results show that the shift system based on the “three eight-hour shifts” has a more serious impact on the fatigue of front-line employees. The workload of employees under the “four six-hour shifts” shift system is relatively small, which is more conducive to fatigue recovery and reduces the probability of unsafe accidents. It is suggested that on the premise of reasonable down-hole time required by law, combined with the current situation of coal mine capacity and cost consumption,reasonably formulate the shift system and gradually implement the “four six-hour shifts” shift system. It can not only ensure the physical and mental health of front-line employees, but also match the means of production and productivity to achieve the purpose of coal mine safety production.

Managing the fatigue of construction workers is crucial to productivity, quality of work, and accident risk reduction. However, the current practice for assessing fatigue is limited when applied to construction sites. This study proposed a framework to objectively and subjectively evaluate construction workers' fatigue in real-time using an ecological momentary assessment (EMA) application and smartwatch data. Fatigue data were collected from 100 construction workers over three days. The results revealed that objective fatigue factors (heart rate and physical activity) were easily affected by the characteristics of the construction field (i.e., starting early, changing and demanding schedules, and overworking hours), whereas subjective fatigue steadily increased with working time. Most workers were aware of physical fatigue at the end of work for the day, when the EMA scores were the highest in a day. However, objective and subjective fatigue did not completely concur throughout the work period. Our findings are expected to improve the management of construction site health and safety with priority given to construction workers. The proposed framework, which utilizes EMA and wearable devices as a fatigue assessment method, reflects the comprehensive aspect of work-related fatigue. [ABSTRACT FROM AUTHOR]

While the LCF behavior of austenitic steels used in nuclear power plants is already well investigated, the VHCF regime has not been characterized in detail so far. For this, fatigue tests on the metastable austenitic steel AISI 347/1.4550 were performed with a servo‐hydraulic testing system at test frequencies up to 980 Hz and with an ultrasonic fatigue testing system at a test frequency of 20,000 Hz. To compare these test results to the ASME standard fatigue curve (total strain amplitude vs. load cycles to failure), a fictitious‐elastic and an elastically plastic assessment method was used. The elaborated elastic–plastic assessment method generates good results, while a purely elastic assessment in the VHCF regime, commonly used in literature, leads to significantly nonconservative results. Moreover, phase transformation from metastable austenite into stable α′‐martensite can take place, and no specimen failure occurs in the VHCF regime. Consequently, for this material, a real endurance limit exists. Highlights: AISI 347 shows a significant plastic strain component in the VHCF regime.Elastic–plastic FE‐analysis describe cyclic material behavior in the VHCF regime accurately.An elastic–plastic based calculation method was elaborated to be able to assess fatigue lifetime.Results of the assessment method show a good accordance to experimental tests and the ASME code fatigue curve. [ABSTRACT FROM AUTHOR]

To predict the service life of welded joints, the seam welds of samples (cross joint, K‐seam, sheet thickness 15 mm and a laser‐welded butt joint, sheet thickness 6 mm, both made of steel quality S 355) are recorded using a 3D scanner. The data obtained in this way is processed and transferred to a finite element method program. The meshing of the weld seams is very detailed. A finite‐element‐method stress calculation is then carried out. The real samples are tested in a fatigue test up to the point of cracking. The results from calculation and test are then compared. A possible crack location can be predicted very well using the finite element method results. The cracks in the real test are always in the area of very high or often the absolute highest calculated stresses. A prediction of the service life in the fatigue test is possible with a certain scatter – close to the usual scatter for welded joints. Based on the results of 19 samples, a fatigue class for local stress (based on the real geometry) of FAT 300 can be preliminary estimated for the cross‐joint specimens. Definition according to the specifications of the International Institute of Welding (FAT at 2 mio. cycles, survival probability 97.7 %). [ABSTRACT FROM AUTHOR]

In order to study the vehicle impact effect on the fatigue assessment for steel bridge decks, the segmental finite element model is built of a continuous steel box girder bridge, and 7-day Weigh-in-Motion(WIM) data of Lianyungang-to-Horgos Expressway is selected to carry out fatigue assessment of typical details. The influence law of impact factors on the fatigue assessment result is analyzed, and the applicability of impact factors in different current specifications is studied. Research results show that the vehicle impact effect has a significant influence on the fatigue assessment results of steel bridge decks. Obvious differences exist in impact effects of different details, the impact effect of rib-to-deck detail is the largest, and the rib-to-rib detail is the smallest. The bridge deck pavement condition has great influence on the impact effect of steel bridge deck, fatigue assessment result of “worse” pavement condition is 3. 30-3. 91 times of “excellent” pavement condition. The vehicle impact effect should be fully considered when the fatigue assessment is performed, and reasonable impact factors should be adopted according to pavement conditions and detail types. [ABSTRACT FROM AUTHOR]

The conveyor belt is by its structure a textile composite. As a load-supporting element of the conveyor, the belt withstands variable loads during its operations. In order to investigate the influence of the level and variability of loading on the life of the belt, tests were carried out on specimens in laboratory conditions. A testing device was specially designed and made for these tests that enabled precise control and monitoring of the loading as well as number of loading cycles up to fracture. This research provides an overview of the influence of fatigue loading on the fatigue life of the belt. The methodology of the conducted research is explained with a description of important technical parameters of the testing device. A physical experiment and a corresponding numerical simulation using the FEM method were carried out with multiple loading levels of belt specimens. Based on the obtained results, appropriate conclusions were made; at loads less than 70% of the breaking strength, the lifetime of the belt is very long. Attention was drawn to additional influences that could not be covered by the experiment and possible directions for further research were indicated. [ABSTRACT FROM AUTHOR]

This study proposes a method for evaluating the fatigue life of tied-arch bridge suspenders by considering the effects of random cyclic traffic loads and environmental erosion. To obtain cumulative fatigue load effects under traffic loadings, a multi-axle single-cell cellular automaton (MSCA) was used to analyze random traffic–bridge-coupled dynamics. Changes in stress amplitude caused by suspender sectional corrosion damage and degradation of suspender S–N curves owing to environmental corrosion were then used to update the relationship between load effect and resistance to obtain the fatigue limit states of the suspenders. To evaluate the dynamic performance and fatigue lives of typical suspenders, a case study involving a basket-type tied-arch bridge was conducted. The results indicated that, under the loading of a typical truck, structural vibration displacement was insignificant but suspender stress was very prominent, especially on the short suspenders. Parametric analysis of the vehicle–bridge interaction revealed that road surface roughness, vehicle weight, and traffic volume significantly affected the dynamic response of the bridge. Under random traffic loads, the shortest suspender experienced the most damage and had a fatigue life significantly shorter than those of the other suspenders. Ignoring corrosion, the shortest suspender fatigue life was 57.8 years; with fatigue corrosion accounted for, however, the shortest suspender experienced fatigue failure owing to cumulative damage after 30 years of service. [ABSTRACT FROM AUTHOR]

Introduction: Primary immunodeficiencies (PIDs) are clinically heterogeneous disorders caused by abnormalities in the immune system. However, PIDs are genetically determined and may occur at any age from early childhood to elderly age. Due to chronic patterns, the risk of malignancy and organ damage in patients with PIDs may affect any aspect of life, including sleep patterns. To our knowledge, the prevalence of insomnia and subjective sleep quality have not been investigated in patients with PIDs. Therefore, this pilot study was conducted to investigate sleep quality, the prevalence of sleep disturbances, and fatigue in adult patients with PIDs in Poland. Methods: All participants were surveyed using the Athens Insomnia Scale, Pittsburgh Sleep Quality Index, Fatigue Severity Scale, and a questionnaire concerning general health and demographic data. We included 92 participants: 48 women (52.2%) and 44 men (47.8%). Results: Participants' mean age was 41.9 ± 13.9 years. The mean sleep duration was 7.0 ± 1.5 hours, and the mean sleep latency was 41.2 ± 53.1 minutes. Additionally, 44.6% of patients (n=41) had symptoms of insomnia and 44.6% (n=42) had poor sleep quality. Less than one-fourth (n=22; 23.9%) of the patients reported the use of sleeping pills; moreover, clinically significant fatigue was reported in 52.2% (n=48). Discussion: Our investigation provides insight into the problem of sleep disturbances in patients with PIDs. Data have demonstrated that sleeping disorders with concomitant fatigue are common in patients with PID. Further studies are needed to determine the determinants of poor sleep quality in this specific group of patients. [ABSTRACT FROM AUTHOR]

The paper focuses on experimental and numerical fatigue assessment procedures to evaluate the influence of multi-axial stress state caused by high centrifugal forces superimposed with bending loads due to blade vibrations on the lifetime of end stage blades from steam turbines. The experimental investigations on original-sized end stage blades were carried out on a test rig specially developed for high forces and multicomponent force application. This was based on detailed numerical simulations by the MPA University of Stuttgart. During the fractographic postexaminations of the tested blades using magnetic particle inspection, light and scanning electron microscopes, two competing damage mechanisms were identified that occurred at different locations. Numerical investigations by means of elastic-plastic finite element analyses were carried out to estimate the local stress conditions acting in the blade root. The local stresses and strains were postprocessed using the critical plane approach and advanced multi-axial fatigue damage parameters. Due to the high stress gradients at the edge of contact, over-conservative predictions may result if their effects are not taken into account. Based on the critical plane method in conjunction with fatigue damage parameters, an approach taking the stress gradient into consideration was developed to predict the fatigue life of the end stage blades. The approach is verified by the component tests on original-sized blades. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xinyang Normal University Natural Science Edition is the property of Journal of Xinyang Normal University Editorial Office 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.)

The purpose of this study is to evaluate the fatigue life of heat exchangers used for Liquefied Natural Gas (LNG) and to ensure its structural safety, the alternating stress of brazing structures under cryogenic conditions was analyzed with a Finite Element Model (FEM). Stress concentrations occurred at the brazed joint with a maximum alternating stress amplitude of 153.45 MPa. The fatigue life of brazed structures during the continuous cool-down and heat-up conditions was evaluated based on the ASME standard and the maximum alternating stress amplitude. Meanwhile, structure parameters have been analyzed for their influence on fatigue life. There are four main structure factors to influence the life cycle: the brazing seam, the fin thickness, the fin distance, and the fin height. The life cycle will decrease with increasing the fin distance, fin height, and brazing seam thickness, and it will increase with increasing the fin thickness. In addition, in order to predict fatigue life, a calculating model has been established based on the main factors. Finally, the fatigue life of brazing structures was also tested by experiment, and the microstructure was also analyzed for the fatigue fracture surface. It is clear that brittle fractures along the brazing seam and ductile fractures at the fin roots should be the primary failure modes. The study provides a base for LNG aluminum heat exchanger design, manufacture, and safe operation. [ABSTRACT FROM AUTHOR]

The fatigue problem of hangers is fatal for the safety of the whole bridge structure. The objective of this study is to present a strain monitoring-based method to assess the fatigue performance of stiff hangers in highway arch bridges and predict their remaining life. A vehicle–bridge interaction system was constructed to analyze the dynamic behavior in the area close to the key welding line where the hanger was connected to the deck slab. Then, the empirical mode decomposition (EMD) algorithm and rain-flow counting algorithm were used in signal preprocessing and statistical analysis of field monitoring data. Finally, the fatigue life was assessed according to the standards in the Chinese Code for the Design of Steel Structures, as well as the Eurocode 3 and AASHTO codes. Differences were found in the fatigue behavior of hangers, and the shortest hanger was shown to surfer more serious fatigue damage. The influence of vehicle volume growth and low-stress amplitude on the fatigue performance was also discussed. [ABSTRACT FROM AUTHOR]

An innovative composite deck system has recently been proposed for improved structural performance. To study the fatigue behavior of a steel-concrete composite bridge deck, we took a newly-constructed rail-cum-road steel truss bridge as a case study. The transverse stress history of the bridge deck near the main truss under the action of a standard fatigue vehicle was calculated using finite element analysis. Due to the fact that fatigue provision remains unavailable in the governing code of highway concrete bridges in China, a preliminary fatigue evaluation was conducted according to the fib Model Code. The results indicate that flexural failure of the bridge deck in the transverse negative bending moment region is the controlling fatigue failure mode. The fatigue life associated with the fatigue fracture of steel reinforcement is 56 years. However, while the top surface of the bridge deck concrete near the truss cracks after just six years, the bridge deck performs with fatigue cracks during most of its design service life. Although fatigue capacity is acceptable under design situations, overloading or understrength may increase its risk of failure. The method presented in this work can be applied to similar bridges for preliminary fatigue assessment. [ABSTRACT FROM AUTHOR]

Existing railway bridges are fundamental assets to expand the capacity of the railway network towards an eco-friendly transport for people and goods. As one of the main sources of structural degradation, fatigue represents a major concern for infrastructure managers, requiring the development of assessment methods that allow for reduced conservatism and increased reliability. Despite the multiscale problem, the implementation of local fatigue methods to large structures can be achieved efficiently when framed within a multiphase global-local assessment. This paper presents an innovative approach for hierarchical modelling based on a three-scale concept applied to riveted connections, which are significant in aging bridges. A structural system that presented failure during operation is investigated, allowing to confront the numerical results against observable damage, which provides a rare opportunity to parametrically understand the roots of fatigue. Numerical models properly validated by experimental results allowed computing fatigue lives that align with real damage, demonstrating the accuracy of the assessment process. Multiscale modelling tools are provided in an engineering framework to extend the fatigue life of existing riveted railway bridges. • A multiphase three-scale concept for fatigue assessment is fully characterised. • A novel hierarchical modelling for riveted details is tested, but generalizable. • A critical and real case study is analysed, showing the advantages of the proposal. • Both global and local fatigue methods are studied, resulting in critical conclusions. • Unique opportunity to compare numerical predictions with real fatigue damage. [ABSTRACT FROM AUTHOR]

The use of unequal-thickness butt-welded joints is widespread in bridge engineering, material savings mean a decrease in cost, which can lead to lower overall costs and significant benefits Because of their unique structures and propensity for stress concentration and weld defects, it is crucial to investigate their fatigue performance. In this study, 15 sets of unequal-thickness butt-welded joints based on Q420qFNH were subjected to fatigue tests. ABAQUS modelling and a stress-extraction process utilising distance iterations were employed in this study. The key findings demonstrated that the fatigue performance of these weathering steel butt joints was superior, and the stress variation at these joints exhibited greater complexity and resulted in a more pronounced multi-crack fusion effect. Additionally, an attempt was made to evaluate the fatigue behaviour of other welded joints and unequal-thickness butt-welded joints using the same approach as that presented herein. The fatigue evaluation method based on nominal stress yielded a significant scatter of 1:T s = 4.21. Iterations were conducted based on the scattering at various critical distances. The results indicate that based on the theory of critical distance, the scatter of 1:T s = 2.304 is lower than the scatter of 1:T s = 2.502 associated with the notch stress method. These findings suggest that employing this method for fatigue assessment yields favourable outcomes across diverse welded joints. • Fatigue tests of Q420qFNH weathering steel in the unequal-thickness butt-welded joint was carried out. • The fatigue failures of Q420qFNH weathering steel in the unequal-thickness butt-welded joint were investigated. • The theory of critical distance-based assessment method was adopted to estimate the fatigue resistance. [ABSTRACT FROM AUTHOR]

Sand waves are commonly formed on the sandy seabed of the continental shelf and characterized by their regular wave-like shape. When a submarine pipeline is laid on this type of seabed, it often experiences free spans due to the unevenness of the seabed. These free spans are particularly vulnerable to vortex-induced vibration (VIV) and the resulting fatigue damage, which have been identified as the primary causes of pipeline failures in offshore oil and gas exploration. This study examines the VIV and fatigue damage of free spans in a submarine pipeline in the Lufeng oilfield, which is located in a large area of sand waves. The assessment conditions encompass the as-laid empty state, the flooded state, and the operational state. Additionally, both the minimum and maximum lay tension are taken into account during the evaluation of VIV and fatigue. The VIV onset screening conducted revealed a considerable number of pipeline free spans exceeding the VIV onset span lengths under both temporary and operating conditions for the non-trench seabed. Furthermore, the analyses indicate that the pipeline does not meet the criteria for VIV fatigue on a non-trenched seabed. Consequently, a proposed solution of implementing a 1 m trench rectification measure for the seabed is recommended. The results demonstrate that this measure effectively mitigates the occurrence of VIV and subsequently reduces fatigue damage across all conditions.