Comportement en flexion de poutres tubulaires rectangulaires (en polymère renforcé de fibres) en béton armé et post-contraintes : études expérimentale et analytique

Abstract : Corrosion damage is recognized as a crucial factor for existing concrete bridge girders and corresponding consequences are significant. A promising solution has recently been proposed using posttensioned (PT) concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) to effectively improve the performance of new concrete structures. Despite this system demonstrated benefits in terms of improving structural behavior, there still is a lack of research, including the functional reliability of posttensioned rectangular CFFT members. Moreover, there are no code provisions for the flexural design of PT rectangular CFFT members. To achieve their broad-based implementation in civil infrastructures, understanding of their flexural behavior is essential. This study presents the results of a comprehensive test program that was aimed at investigating the flexural behavior of rectangular CFFT beams posttensioned with unbonded steel tendons to address the knowledge research gaps in this field. The tests intend to simulate a number of design parameters, which are mainly governed by flexural loading. Fifteen full-size beams with internal steel bars were tested, including thirteen PT CFFTs and two PT concrete beams along with one non-PT CFFT from the literature for comparison. The investigated parameters are i) GFRP tube thickness ranged from 6.0 mm to 12.3 mm; ii) Tube fiber structural laminate; iii) Tube confinement versus steel stirrups; iv) Number of prestressing tendons and level of prestressing; v) Concrete compressive strength [(normal and high strength concrete (NSC and HSC)]; vi) Total reinforcement index; vii) Attaching a thin Carbon FRP-laminated embedded in tension flange and its ratio; and viii) Loading scheme (static and cyclic). Moreover, an analytical study was conducted to develop a model to predict the ultimate strength of prestressed CFFT members. The model is based on strain compatibility and force equilibrium, which account for the material constitutive relationships for FRP tube laminates, steel strands, and non-linearity of concrete. The accuracy of the proposed model is also verified against the experimental results. Finally, a new design equation, as an extension to AASHTO (2012) equation, is also established based on a regression analysis of the test results to predict the ultimate flexural capacity of the tested beams, which significantly impacts the design practice of such members. The experimental results demonstrated the feasibility and construction of rectangular CFFTs posttensioned with steel tendons. The test results indicated that rectangular CFFT beams prestressed with unbonded steel strands could effectively replace conventional members made from traditional materials or identical rectangular CFFT without prestressing, in terms of similar or better structural performance. The flexural behavior of the tested PT CFFT beams is highly depended on the FRP tube confinement, laminate, thickness, and attaching a thin Carbon FRP-laminated embedded in tension flange, and to a much less extent, on the magnitude of the prestress level, the number of strands, concrete strength, and loading scheme. Furthermore, it was found that neglecting concrete confinement in the proposed model highly underestimates the flexural strength. The promising results of this study can provide the impetus for constructing a new sustainable and high-performance hybrid structural rectangular PT CFFT elements.Les dommages des infrastructures en béton dus à la corrosion représentent un facteur crucial pour les poutres de pont en béton et les conséquences associées à ces dommages sont très importantes. Malgré les avantages évidents de ce système en termes d'amélioration du comportement structural et de durabilité, il y a encore un grand manque de données expérimentales et de modélisation, y compris la faisabilité fonctionnelle des éléments tubes en polymère renforcé de fibres (PRF) et remplis de béton (TPRB) rectangulaires PC. De plus, il n'y a pas de normes pour la conception en flexion de ces éléments. Pour parvenir à la mise à l’échelle et à l’introduction de ces éléments TPRB dans les infrastructures civiles, la compréhension et la modélisation de leur comportement en flexion est indispensable. Étant la toute première étude expérimentale sur le sujet, cette étude présente les résultats d'un programme expérimental visant à étudier le comportement en flexion des poutres TPRB rectangulaires PC (avec des tendons en acier post-tensionnés) pour combler la lacune de recherche susmentionnée. Le programme expérimental vise à simuler un certain nombre de paramètres de conception des TPRB-PC. Treize poutres (à échelle réelle, incorporant des barres d’armature en acier) dont douze TPRB rectangulaires PC, deux poutres en béton armé conventionnel et PC et une poutre TPRB sans post-tension (pour comparaison) ont été testées. Les principaux paramètres étudiés sont : (i) l'épaisseur du tube GFRP variant de 6,0 mm à 12,3 mm; (ii) l’orientation et l’empilement des couches des fibres dans les tubes ; (iii) le confinement par des tubes par rapport aux étriers en acier dans les poutres conventionnelles; (iv) le nombre de tendons et le niveau de précontrainte ; (v) la résistance à la compression du béton [béton normal (BO) et béton à haute résistance (BHP)] ; (vi) l'indice de renforcement total; (vii) l’effet de l’intégration d’une fine lamelle de carbone en PRF dans une la zone tendue du tube en PRF; et (viii) type de chargement (statique et cyclique). De plus, une étude analytique a été menée afin de développer un modèle permettant de prédire la force ultime des éléments TPRB-PC. Le modèle est basé sur la compatibilité des contraintes et l'équilibre des forces, qui tiennent compte des relations constitutives des matériaux (laminés de tubes FRP, tondons d'acier, et la non-linéarité du béton). La précision du modèle proposé est également vérifiée par rapport aux résultats expérimentaux. Enfin, une nouvelle équation de conception, en tant qu'extension de l'équation de l'AASHTO (2012), est également établie (sur la base d'une analyse de régression des résultats expérimentaux) pour prédire la capacité de flexion ultime des poutres TPRB-PC testées, ce qui pourra avoir un impact significatif sur la pratique de conception des éléments TPRB-PC. Les résultats expérimentaux ont démontré la faisabilité des éléments TPRB PC avec des tendons d'acier. Les résultats ont ainsi indiqué que les poutres TPRB PC peuvent effectivement remplacer les éléments conventionnels fabriqués à partir de matériaux traditionnels ainsi que les TPRB sans pré ou post-tension, tout en démontrant des performances structurales nettement supérieures. Le comportement en flexion des poutres TPRB -PC testées dépend fortement du confinement des tubes en PRF, de la séquence d’enroulement et de l’orientation des fibres, de l'épaisseur et de l’intégration d'une mince couche de laminé en PRF de carbone et, dans une moindre mesure, de l'ampleur du niveau de post-tension, du nombre de torons, de la résistance du béton et du type de chargement. En outre, il a été constaté que le fait de négliger l’effet de confinement du béton dans le modèle proposé sous-estime fortement la résistance en flexion. Les résultats prometteurs de cette étude peuvent promouvoir la construction des structures hybrides (faites à partie des TPRB rectangulaires PC) plus durables et plus performantes

Production of Neutralinos Via H0 Propagator From Electron –Positron Annihilation

The cross-sections ?,  in electron (e-) positron (e+) collision, are calculated over range of center of mass energy S for the proces

STR-937: BEHAVIOUR OF FRP-REINFORCED CFFT COLUMNS UNDER AXIAL COMPRESSION LOADING

This paper presents the test results of an experimental study aimed at investigating the axial behaviour of CFFT columns internally reinforced with steel and FRP bars. A total of eight reinforced concrete (RC) and concrete-filled FRP tube (CFFT) columns were constructed and tested until failure. All columns had 1900-mm in height and 213-mm in diameter. The test parameters were: (1) internal reinforcement type (steel, glass FRP (GFRP), or carbon FRP (CFRP) bars) and amount, (2) GFRP tube thicknesses, and (3) nature of axial loading type (i.e. monotonic and cyclic). The experimental results revealed that the CFFT columns reinforced with GFRP bars exhibited similar responses compared to their counterparts reinforced with steel bars with no significant difference in terms of ultimate axial strength and strain capacities. Providing the GFRP tubes of the CFFT columns significantly enhanced the strength and strain capacities and attributed to change the mode of failure from axially dominated material failure (for the control columns) to instability failure (for the CFFT columns). Furthermore, the envelop curve of the CFFT reinforced column tested under axial cyclic loading is almost identical to the axial stress-strain curve of the same specimen tested under axial monotonic loading. However, the ultimate axial and hoop rupture strain was slightly larger for the specimen subjected to axial cyclic loading. Finally, using FRP bars instead of conventional steel bars in the CFFT columns can provide a step forward to develop a promising totally corrosion-free new structural system

Factors Affecting Nursing Performance in Caring Patients with Cerebral Stroke during First Golden Hours

Context: Stroke is associated with high mortality, morbidity and creates a significant and enduring impact on patients, their families, and the wider society.Aim: assess the nurses' performance for patients with cerebral stroke during the first golden hours through assessing nurses' level of knowledge regarding cerebral stroke and their nursing management during first golden hours, assessing the level of nurses' practices for patients with cerebral stroke during the first golden hours and assess factors that affect nurses' performance in the management of patients with cerebral stroke during first golden hours. Methods: A descriptive exploratory study design was used to achieve the aim of this study. The study recruited a convenient sample of 80 nurses. Data was collected from Intensive Care Units at Ain Shams University and specialized hospitals affiliated with Ain Shams University in Egypt. Two tools were used for data collection: Nurses' self-administered questionnaire and nurses’ performance observational checklist. Results: This study revealed that 63.75% had an unsatisfactory level of knowledge, 68.8% had inadequate performance, and there were human and non-human resource factors, both affect negatively on nurses' performance in the management of patients with cerebral stroke.Conclusion: The study concluded that there was an unsatisfactory score of nurses' knowledge and practice, and there were human and non-human resource factors that negatively affect nurses' performance. Based on these findings, the study recommended periodic education programs be developed for nurses about managing patients with cerebral stroke during the first golden hours, and prospectively follow-up studies are needed to develop and refine interventions

Production of Neutralinos as Adark Matter via Z0 Boson Propagator

The cross-section, in electron (e-) positron (e+) collision, are calculated over range of center of mass energy S  for the process.Please find more in the PDF version

Classification Arabic Twitter User’s Insights Using Rough Set Theory

Nowadays, people using social media from around the world to share their daily affairs. Arabic twitter for example is a platform where users read, reply, post which known ‘tweets’. Users trading their opinions on different trends that are not equal in important and differed based on their power and interest. Tweets can provide rich information to make decision. The main objective of this paper is to present a framework for making a valuable decision through analyzing social users' insights based on their proximity to a particular trend with highlights their power in this trend. Tweets are exceedingly unstructured that makes it difficult to analyze. Nevertheless, our proposed model differs from previous research in this field it gathered the use of supervised and unsupervised machine learning algorithms. The process of performing this work as follows: classifying users based on the degree of their closeness/interest utilizing Mendelow’s power/interest matrix, rough set theory to eliminate the features that may be found in user profiles to find minimal sets of data. The proposed model applied two attribute reduction algorithms on our dataset to determine the optimal number of reducts for improving decision making from the user replies. In addition to, unsupervised machine learning to group their replies into subcategories such as positive, negative, or neutral. The experimental evaluation shows that Johnson algorithm has reduced the user attributes by 71% than genetic algorithm that utilized in a classification model

Emergence of Colistin-resistant Pseudomonas aeruginasa in Sohag University Hospitals, Egypt

Background:  Pseudomonas aeruginosa (P. aeruginosa) is a globally recognized cause of healthcare-associated infections (HAIs), the recent increase of the MDR and XDR P.  aeruginosa strains encouraged the use polymyxins as a treatment option, and thus the emergence of colistin-resistant strain is an alarming problem. Objectives: This study aimed to trace the emergence of colistin-resistance in P.  aeruginosa strains associated with HAIs in Sohag University Hospitals, to identify the genetic basis of colistin-resistance in these isolates. Methods: P. aeruginosa strains were isolated and identified phenotypically and genotypically, antibiotic susceptibility of the isolates was tested by disc-diffusion method. The MIC of colistin was measured by E test in colistin resistant isolates. Conventional PCR was used to detect plasmid genes responsible for colistin resistance among the isolates. Results: Seventy-six(76%) of P. aeruginosa isolates were resistant to colistin, the highest percentage of colistin resistant strains were isolated from patients admitted to General Surgery Department that was (50%), no colistin resistant strains were isolated from patients admitted to Vascular Surgery Department. Colistin-resistant isolates exhibited the highest resistance to polymyxin B, norfloxacin, ofloxacin and gatifloxacin by a percentage of (100%). mcr-1gene was detected in (44.4%) of colistin-resistant isolates and mcr-2 gene in (16.6%). Sensitivity of E-test in comparison with PCR was (100%) and specificity was (86.36%). Conclusion: The emergence of colistin resistance in P. aeruginosa in our health care setting is an alarming issue that needs strict adherence to the infection control guidelines specially plasmid mediated resistance as it usually associated with MDR and XDR patterns

Tertiary Trauma Survey: Nurses Performance and Polytrauma Patients’ Outcomes

Context: Tertiary Trauma Survey is an important tool for detecting missed injury, and some trauma units have created their protocol for tertiary trauma surveys to decrease the incidence of missed injuries in trauma patients.Aim: This study aims to assess nurses' performance regarding tertiary Survey and Poly-trauma patients' outcomes.Methods: Descriptive exploratory design was utilized to achieve the aim of the study. A convenient sample of all available nurses (50 nurses) working in the intensive care unit at the emergency hospital affiliated to Ain Shams University Hospitals. A purposeful sample composed of (50) adult patients diagnosed as polytrauma patients was recruited from the same units. Data was obtained through three main tools; Self-administered questionnaire for nurses, nurses practice observational checklist and clinical outcome record for patients. Results: Nurses had an unsatisfactory level of knowledge and practice regarding the tertiary trauma survey (44%&32%, respectively). There was a highly statistically significant positive correlation between the total level of knowledge and practice. There was a difference between injury severity score and laboratory, hemodynamic status, physical assessment, and radiological findings of poly-trauma patients on admission and after 24 hours. Conclusion: Less than half and less than one-third of the nurses under study had an unsatisfactory level of knowledge and practice, respectively, regarding the tertiary trauma survey. There was a highly statistically significant positive correlation between the total level of knowledge and total level practice. Polytrauma patients' outcomes revealed a statistically significant difference between injury severity score, hemodynamic status, physical assessment, and radiological findings in polytrauma patients on admission and after 24 hours. Recommendations: Further research is needed to follow the patients' outcomes and missed injuries. Replication of the current study on a larger probability sample is recommended to achieve generalization of the result. Tailored Training courses are needed for nurses to improve unsatisfactory knowledge and practices regarding tertiary trauma survey- integrated studies with the emergency medical team to communicate patients' outcome research findings

Amélioration psychoacoustique du filtrage de Wiener : quelques approches récentes et une nouvelle méthode

*Bruit musical, distorsion, filtre deWiener, psychoacoustique, signal de parol

Assessment of The Nurse Interns' Medication Administration Safety Performance

Contents: Medication administration is an integral part of delivering quality nursing care. The nurse intern should follow the specific guidelines to enhance their medication administration safety.Aim: The study aims to assess the nurse intern's medication administration safety performance.Methods: The study was conducted at Ain Shams University Hospitals using the descriptive design on 90 nurse interns by using three tools, namely, the medication administration knowledge questionnaire, the observational checklist for nurse interns' safety performance, and the Medication Administration safety Attitude Rating Scale. Results: Findings of the study revealed that the minority of nurse interns (4.3%) had satisfactory total knowledge, 39% had adequate total practice, and around two-thirds of them (62.6%) had a positive attitude.Conclusion: It is concluded that the nurse interns had unsatisfactory knowledge of the medication administration safety, and their related practices are mostly inadequate, although the attitude tends to be high. The study recommended that nurse internship programs emphasize medication administration safety knowledge and practice, focusing on identified gaps and deficiencies. Further research is proposed to assess the effect of training strategies on the nurse intern's medication administration safety