This study investigates propagation of mode I crack in B70 pre-stressed concrete sleepers by fracture mechanics approach. A new experimental analysis is done for notched B70 pre-stressed concrete sleepers with Replica test and image analysis. A scanning electron microscope test (SEM) and an image analysis are applied for the Replica test in order to determine crack length and crack mouth openin...

this study investigates propagation of mode i crack in b70 pre-stressed concrete sleepers by fracture mechanics approach. a new experimental analysis is done for notched b70 pre-stressed concrete sleepers with replica test and image analysis. a scanning electron microscope test (sem) and an image analysis are applied for the replica test in order to determine crack length and crack mouth openin...

Initial cracks occur in high strength concrete sleepers for various reasons, such as shrinkage and wrong curing and long lifetime of over 50 years of sleepers. These cracks may lead to complete failure of the structure. In order to more accurately design the sleepers, fracture mechanics (not strength of materials) should be incorporated. In order to achieve this purpose, it is important to fore...

initial cracks occur in high strength concrete sleepers for various reasons, such as shrinkage and wrong curing and long lifetime of over 50 years of sleepers. these cracks may lead to complete failure of the structure. in order to more accurately design the sleepers, fracture mechanics (not strength of materials) should be incorporated. in order to achieve this purpose, it is important to fore...

The load generated during train operation is transmitted to sleepers through rails, and then from trackbeds. As one of the important components track structure, are very service-life safety railways. running speed will produce different frequencies on rails. To explore response under cyclical loads, this research used discrete element method simulate rails sleepers, realizes loading by applying...

An improved spatial vehicle–track–bridge interaction system considering the unsupported track is proposed using virtual work principle. When fails to be supported due defects under track, corresponding bridge–rail connection coupled matrix should removed. Using dynamic model, a novel numerical analysis of unilateral and bilateral sleepers in bridge subgrade carried out. The results indicate tha...

The dynamic response of a railway track has been investigated by analytical or numerical models. When rail supports (sleepers) foundation contain defects, the damage reduces stiffness and becomes non-uniform. This paper presents new model to calculate responses on non-uniform foundation. In this model, is considered as an infinite beam resting equidistant subjected moving forces. sleepers are s...

We compared good sleepers with minimally and highly distressed poor sleepers on three measures of daytime functioning: self-reported fatigue, sleepiness, and cognitive inefficiency. In two samples (194 older adults, 136 college students), we tested the hypotheses that (1) poor sleepers experience more problems with daytime functioning than good sleepers, (2) highly distressed poor sleepers repo...

BACKGROUND It is not clear whether cognitive decline progresses more quickly in long sleepers than in short sleepers or than in participants with usual sleep duration. We assessed cognitive decline as a function of self-reported sleep duration in a prospective population-based cohort (NEDICES). METHODS Participants were evaluated at baseline and 3 years later. Baseline demographic variables w...

Neurophysiological processes underlying auditory memory and attention are impaired in habitually short sleepers. The aim of this study was to use dynamic causal modeling (DCM) to study the mechanisms of these impairments in short sleepers. Eight normal sleepers (total sleep time (TST)=7-8h) and nine habitual short sleepers (TST ≤ 6 h) participated. The time in bed was increased from habitual (≤...