Fatigue Vulnerability Research Articles

Fatigue assessment of bridges using interacting filtering approach with sub-structured predictor model based on current health

Fatigue estimation for critical structures necessitates comprehensive monitoring, which, in turn, requires dense instrumentation and models that heavily rely on computational resource models that heavily rely on computational resources. However, the fatigue vulnerability of different segments within the infrastructure can be considered to adopt a cost-effective substructure-based monitoring approach, minimizing the need for extensive instrumentation or complex models. However, estimating or instrumenting the substructure boundary adds to the complexity. In addition, conventional fatigue estimation approaches often assume constant structural health, disregarding the unknown current health status of aging structures. To overcome this limitation, a novel substructure-based fatigue life estimation approach is developed, incorporating an interacting ensemble-particle filter that considers the current health status while remaining robust against boundary forces. Numerical experiments validate the proposed approach on a simulated reinforced concrete box girder bridge, utilizing a 3D beam model that accounts for dynamic interaction with vehicles. A parametric analysis investigates the relationships between fatigue damage and factors such as surface roughness, vehicle speed, vehicle weight, and vehicle category, aiming to identify dominant stimuli. The results demonstrate an accurate estimation of health parameters and remaining useful life (RUL). Furthermore, a novel decomposed approach for RUL estimation is developed, enabling the mapping of traffic information to fatigue damage without requiring costly simulations. A case study highlights the practical applicability of the approach, focusing on a reinforced concrete box girder bridge in Himachal Pradesh, India.

Optimizing Rural Pavements with SBS-Modified Asphalt Binders and Petroleum Resin

This study addresses the imperative for enhancing asphalt mixtures tailored for rural pavements, focusing on optimizing RAP mixtures with styrene–butadiene–styrene (SBS)-modified asphalt binders incorporating petroleum resin and oil. Through systematic investigation, the study examines the impact of varying RAP content (25% and 50%) and two SBS-modified asphalt binder types (Type 1 and Type 2) on mechanical properties and sustainability. Laboratory tests reveal that the mix of 25% RAP + 75% Type 1 exhibits exceptional flexibility, evidenced by a high ductility value of 880 mm at 25 °C, enhancing pavement resilience. Conversely, the 50% RAP + 50% Type 2 mixture displays vulnerability to fatigue cracking, while 25% RAP + 75% Type 1 demonstrates superior resistance, with a fatigue vulnerability value of 1524 kPa. The Hamburg Wheel Tracking test highlights the influence of RAP content on rut depth, with the mix of 50% RAP + 50% Type 1 achieving the lowest rutting at 3.9 mm. Overlay test results show the mix of 25% RAP + 75% Type 2’s resilience, with the lowest load reduction at 64.5%, while the mix of 50% RAP + 50% Type 1 exhibits substantial load reduction at 82.1%. Field tests unveil differences in pavement bearing capacities, with the mix of 25% RAP + 75% Type 2 demonstrating a remarkable elastic modulus of 58.5 MPa, indicating heightened bearing capacity. The investigation underscores the significant role of SBS-modified asphalt binders with incorporated petroleum resin and oil in enhancing fatigue resistance for sustainable rural pavements.

Postural balance disorders in sarcopenia based on surface electromyography

BackgroundSarcopenia is an intrinsic factor that leads to balance disorders and falls in older adults. However, the characterization of sarcopenia-related postural balance deficits remains unclear. AimsThis study aimed to explore the balance performance and postural control strategy in older adults with sarcopenia during static stance tasks using force platforms and surface electromyography. MethodsOlder adults with right-sided dominance were recruited, including 27 adults with sarcopenia and 27 healthy counterparts. Postural sway was measured with eyes open/closed on rigid/compliant surfaces. The time- and frequency-domain indexes of bilateral lower extremity muscle activity were simultaneously recorded. ResultsThe postural sway and activity of multiple lower extremity muscles in the sarcopenia group were increased (P < 0.05). The amplitude contribution ratio of the right tibialis anterior muscle (larger in sarcopenia), co-contraction ratio of right ankle dorsiflexion (smaller in sarcopenia), and mean power frequency and median frequency of the left gluteus maximus muscle (smaller in sarcopenia) had main effects of grouping (P < 0.001, η2p = 0.06–0.10). All of them had discrimination for sarcopenia (area under the curve = 0.639–0.657, P < 0.001) and were correlated with balance function measurement in sarcopenia (|rs| = 0.22–0.44, P < 0.05). ConclusionThe results of this study suggest that older adults with sarcopenia have decreased balance function and increased cost of electrophysiology. They were found to prefer the postural strategy of dominant ankle dorsiflexion and demonstrated overactivity of the dominant tibialis anterior muscles and fatigue vulnerability of the nondominant gluteus maximus. Improvements in these postural features may have balance benefits.

Fatigue performance and optimal design of corrugated steel–concrete composite bridge deck

Orthotropic steel bridge deck (OSD) has been widely used in long and medium span bridges. However, traditional OSD with U-ribs is prone to fatigue cracking at the deck-to-rib welded joint. Corrugated steel–concrete composite bridge deck (CSCCBD) composed of corrugated steel plate, concrete layer and perforated plate shear connectors was proposed recently to improve the fatigue performance of the bridge deck. In this paper, comparing of the fatigue performance of OSD and CSCCBD was conducted through finite element (FE) analysis. The results showed that the stress amplitude of deck-to-rib welded joint of CSCCBD was reduced by more than 90 % compared with OSD. The fatigue problem of deck-to-rib welded joints can be solved fundamentally. It is further studied that distribution of fatigue vulnerability details of CSCCBD. The most unfavorable fatigue vulnerability details are located around the diaphragm-to-rib weld. The fatigue life of CSCCBD was evaluated based on the linear cumulative damage theory. Consequently, the effect of diaphragm cut-out on the fatigue performance of CSCCBD was studied. It was found that the diaphragm without cut-out can effectively reduce the stress amplitude caused by vehicles, and increase the earliest fatigue cracking life of details around the diaphragm-to-rib weld from 2.16 years to 43.4 years compared with OSD. Finally, the section form of CSCCBD without cut-out was optimized by response surface method (RSM). It was proved that RSM was adequate for the optimization design of CSCCBD.

Fatigue vulnerability of sea cage to storm wave loads

Fatigue vulnerability of sea cage to storm wave loads

Differential effects of modafinil on performance of low-performing and high-performing individuals during total sleep deprivation

BackgroundIndividual responses to the effects of inadequate sleep have been well documented; some people are more vulnerable to the effects of sleep loss than others. Fatigue-vulnerable individuals generally require access to effective fatigue countermeasures; however, the question arises as to whether these fatigue-vulnerable individuals receive the same benefits shown in group efficacy data. The present study administered modafinil to individuals to determine its differential effects on performance of best and worst performers during sleep deprivation. MethodsA sample of 22 men, age 21–40 yrs., was tested on 2 separate occasions during which they were kept awake for 36 h. During one period they received 200 mg modafinil; during the other they received placebo. Participants were tested on a variety of tasks while rested and at 5-hr intervals across the continuous wakefulness period. Performance for each cognitive task and subjective measure of fatigue from the placebo period was used to group individuals into high (HP) or low performance (LP) groups to indicate fatigue vulnerability for each task. ResultsResults indicated that on the MTS task, the HP group performed the same throughout the testing period, regardless of whether they received modafinil or not. However, the LP group significantly improved after receiving modafinil compared to placebo. Performance on the PVT showed the HP group had a small decrease in the number of lapses after receiving modafinil compared to placebo, whereas the LP group had a large decrease in lapses after receiving modafinil compared to placebo. Performance on the RDM showed no difference between groups, regardless of drug condition. Groups did not differ after receiving modafinil on subjective fatigue measured by the POMS. ConclusionsDepending on the task, HP individuals did not benefit substantially when administered modafinil compared to placebo. However, the LP individuals improved after receiving modafinil compared to placebo.

Compassion Fatigue and Compassion Satisfaction Among Multisite Multisystem Nurses.

Compassion fatigue is a phenomenon that might affect nurses of all specialties. Compassion fatigue occurrence could be profound and costly. The immediate impact could be disruption of the unit culture. This study investigated the prevalence and individual-level factors associated with compassion fatigue among nurses. An upsurge in patients' complexity today may leave nurses stressed with increasing practice demands and vulnerable to compassion fatigue. If ignored, compassion fatigue may compromise nurses' health and care outcomes. A sample of 1174 nurses from 2 large Southern California health care organizations completed an online survey measuring compassion fatigue, burnout, and compassion satisfaction. Overall, participants scored moderate to average (23-41) on compassion satisfaction, burnout, and compassion satisfaction. Experienced and working nights nurses experienced higher compassion satisfaction levels. Higher compassion fatigue means were associated with new graduates = 29.5, BSN nurses = 27.2, ICU nurses = 27.4, and working 12-hour shift nurses = 26.9, suggesting higher compassion fatigue vulnerability. Nurse leaders and managers can apply this baseline evidence to create tailored programs for specific nursing specialties and inexperienced nurses to tackle compassion fatigue and reduce related unit disorder. Seasoned nurses' perspective can be of value in enhancing those efforts.

레일 체결장치 텐션클램프의 거동

Abstract In a situation in which importance of rail fastening system is growing with increasing the construction of concrete track, an accident of tension clamp(the component of rail fastening system) breaking has been recently occurred. This results from various factors such as field condition, operating agency, running condition, traffic frequency and so on. Thus, the study for the behavior of tension clamp is required. In this paper, an experiment and finite element analysis(FEA) have been performed to analyse the mechanical behavior of tension clamp. The stressand displacement of tension clamp have been analyzed as the clamping force through a laboratory test, and they werecompared with FEA results. Furthermore, the stress and displacement of the tension clamp are derived from train loadcondition applying the verified model, and the fatigue vulnerability of the tension clamp is identified through stressanalysis. Keywords : Concrete Track, Finite Element Analysis(FEA), Mechanical Behavior, Rail Fastening system, Tension Clamp

Predicting Complex Spatial Working Memory Fatigue Vulnerability Based on Individual Differences in fMRI Images

The effects of mental and physical fatigue can significantly impact how we interact with our daily environment. Furthermore, these effects exhibit a high level of variance across individuals. Advances in technologies such as functional magnetic resonance imaging (fMRI) are offering new opportunities to characterize the effects of sleep deprivation on individuals. In this paper, we investigate the use of advanced fMRI modalities in resting wakefulness as correlated with performance on a spatial working memory task after sleep deprivation. Findings show that fatigue vulnerability to performance decrements on complex spatial working memory tasks in healthy participants can be predicted by fMRI images taken during resting wakefulness.

Damage Assessment of Steel Bridge Members by Fatigue Vulnerability Considering Corrosion and Traffic Variation with Time

The fatigue vulnerability estimation method including the effects induced by the corrosion rate and the traffic variation with time has been proposed to evaluate the reduction of fatigue strength in steel bridge members. A fatigue limit state function considering corrosion and traffic variation is established to determine whether the steel bridge members have been damaged by both corrosion and fatigue or not. Monte-Carlo simulation is used for reliability analysis which provides the data used to obtain fatigue vulnerability curves. The results show that the damage accumulation induced by fatigue in steel bridges could be assessed by fatigue vulnerability curve considering influences of corrosion and traffic variation.

Are Individual Differences in Fatigue Vulnerability Related to Baseline Differences in Cortical Activation?

Recent evidence suggests that underlying patterns of cortical activation may partially account for individual differences in susceptibility to the effects of sleep deprivation. Here, functional magnetic resonance imaging (fMRI) was used to examine the activation of military pilots whose sleep-deprivation vulnerability previously was quantified. A Sternberg Working Memory Task (SWMT; S. Sternberg, 1966) was completed alternately with a control task during a 13-min blood oxygen level-dependent fMRI scan. Examination of the activated voxels in response to SWMT indicated that, as a group, the pilots were more similar to fatigue-resistant nonpilots than to fatigue-vulnerable nonpilots. Within the pilots, cortical activation was significantly related to fatigue vulnerability on simulator-flight performance. These preliminary data suggest that baseline fMRI scan activation during a working memory task may correlate with fatigue susceptibility.

Evaluation of load cycles generated on a fixed tine working in soil

Principles for specifying representative tine service load histories and the range of histories likely to be encountered are stated. Apparatus for collecting load histories was built and field experiments were carried out on many, various sites. Load histories were collected and corresponding fatigue lives were estimated by computer. Statistical analysis showed that soil cone index and estimated fatigue life were linked, and that increasing landspeed reduced estimated life. Load history simulations were built from population descriptors for soils with and without stones and shown to have similar fatigue vulnerability to real histories.

Evaluation of load cycles generated on a fixed tine working in soil

Principles for specifying representative tine service load histories and the range of histories likely to be encountered are stated. Apparatus for collecting load histories was built and field experiments were carried out on many, various sites. Load histories were collected and corresponding fatigue lives were estimated by computer. Statistical analysis showed that soil cone index and estimated fatigue life were linked, and that increasing landspeed reduced estimated life. Load history simulations were built from population descriptors for soils with and without stones and shown to have similar fatigue vulnerability to real histories.