Behavior of Confined Concrete using Prestressing Skew Bars

This paper presents the results of an experimental study on the biaxial compression behavior of concrete prism confined using pre-stressed bars. The pre-stressed bars could provide passive confinement stress, that preventing the lateral strain of the prism from increasing leading to an increase in both the initial modulus of elasticity and prism compressive strength. The confined concrete had a higher compressive strength that was directly proportional to the confinement bar pressing force and lower ductility than the plain prisms. The concrete initial modulus of elasticity is directly proportioned to the confinement lateral pressure of the prestressing bar and inversely proportion with the spacing between prestressing bars. It was simple to find out that the best pre-stressing stress was 10 N/mm2, also the compressive strength of the confined concrete with pre-stressed skew bars was greater than the compressive strength of the unconfined concrete by more 3.3 times.

Mental Health, Learning Behaviour and Perceived Fatigue Among University Students During the COVID-19 Outbreak: a Cross-sectional Multicentric Study in the UAE

BackgroundThe rapid shift to online education due to COVID-19 quarantine challenged students’ ability to accept pure online learning without negative consequences for their physical, emotional and mental health. Some educational institutions introduced new strategies to reduce the psychosocial burden associated with online learning during home confinement. Thus, The primary aims were to determine the consequences of COVID-19 for the psychological well-being and fatigue levels of higher education students and to explore the effects of a new academic assessment approach in reducing home confinement stress.Method A cross-sectional online survey was conducted among students of 7 disciplines in all 16 higher colleges of technology in the United Arab Emirates (UAE). The Mental Well-being and Learning Behaviours Scale and the modified Copenhagen Burnout Inventory were used to evaluate students’ psychological well-being and fatigue levels. A t-test and ANOVA were performed to determine the differences in perceived psychological well-being and fatigue associated with students’ characteristics. Second, multiple linear regression models performed to identify the independent predictors of fatigue level. ResultsOne thousand four hundred students participated. The majority were female (78.5%) and aged from 21-25 years (58.1%). Around 14% of respondents were married with children. Nearly 40% were satisfied with the new assessment approach introduced during the COVID pandemic and 45.5% perceived it as having reduced their home confinement stress. The mean psychological distress score of 3.00 (SD ± 0.71) indicates a moderate impact of COVID-19 on psychological well-being. Students’ psychological distress was positively correlated with fatigue level (0.256, p<0.001) and negatively correlated with the perceived impact of the new assessment approach on student lifestyle (-0.133), physical health (-0.149) and coping with stress (-0.125). Male students experienced significantly lower fatigue and better psychological well-being than female students.ConclusionThe study reveals that new assessment approaches which emerged during home confinement reduced students’ perception of stress and of impaired lifestyle. However, students still had a considerable burden of psychological distress, requiring further preventive measures to maintain their psychological well-being during future outbreak events. Educational institutions should consider additional strategies to improve students’ preparedness for online teaching, which could help maintain their psychological well-being.

Research of the Behavior of Clay Materials with Double Porosity

This contribution presents results from a series of compression and undrained triaxial tests to study the mechanical behavior of dump clay from the north of Bohemia. The use of these materials as a foundation for construction can’t be achieved without the adoption of some precautions. This comes from embankment, formed by digging the ground (altered claystone), up to the level of coal mining which is in a sub horizontal stratigraphic layer. A potential static liquefaction behavior was observed in undrained tests for high confinement stress. A structural collapse was noticed with the results obtained in the triaxial test. This collapse is characterized by an unexpected large decrease in deviator and mean effective stress. The soils formed have strength properties that are potentially dangerous. These concepts can improve the use of these kinds of soils in geotechnical engineering work. It continues and expands the results obtained in previous research, especially the future problematic use of these materials as the foundation soil for line or building structures.

Sociodemographic Characteristics and Stress of People from Spain Confined by COVID-19

This study responds to the need to explore the individual characteristics that may help us to understand the levels of stress involved in the significant COVID-19-related restrictions to people’s daily lives. In order to understand levels of stress and stress control during the COVID-19 confinement, 1269 people from Spain (17.5% men) aged between 18 and 70 completed the Perceived Stress Scale (PSS-14). The results indicated that people aged under 40, and especially those under 25, women, and those on low incomes reported higher rates of confinement stress. The nature of where people live, and their working situation during confinement also contributed to people’s stress response, although with lower levels of impact. In this context, our study suggests that the levels of stress in those who combine remote working with in situ working were lower than those who had other working conditions. Our study contributes significant information to understanding the effects of confinement, and its results may be used to inform intervention tools and programs.

EFFECT OF PRE-SLAUGHTER CONFINEMENT STRESS ON PHYSICOCHEMICAL PARAMETERS OF CHICKEN MEAT

The effect of pre-slaughter lairage stress on biogenic amines, pH, and color with the CIELab system (where three variables L*, a*, b* are estimated: L* for lightness, a* defines redness, and b* defines yellowness) in chicken breast meat was investigated. Before slaughtering, 25 broilers were selected and divided into five groups according to lairage holding time (30 min or 3 h), day/night schedule (daylight or nighttime) and control (no lairage). After slaughtering, breasts (M. Pectoralis major) were removed, stored for 9 days at 4 °C, and analyzed every 3 days. The results showed a pH decrease during nighttime holding. Also, a three-hour pre-slaughter holding (daytime or night) resulted in high biogenic amine concentration, increase in lightness (L*), and reduction in redness (a*) during storage. Cadaverine concentration showed a rapid increase from day 6 onward. The time and schedule of chicken lairage is a pre-slaughter stress factor that affects meat quality. Based on these observations, it is recommended to slaughter chickens immediately on arrival at the processing plants.