Shear contribution of fiber-reinforced lightweight concrete (FRLWC) reinforced with basalt fiber reinforced Polymer (BFRP) bars

Cette étude porte sur le comportement au cisaillement des poutres en béton léger fibré et renforcées par des barres de polymère renforcé de fibres de basalte (PRFB). Dix poutres (150x250x2400 mm) coulées avec du béton fibré ou non-fibré ont été testées en flexion. Deux poutres ont été coulées sans fibres (poutres contrôles) tandis que les huit autres poutres ont été coulées avec du béton contenant des différents types et pourcentages de fibres. Les paramètres étudiés comprenaient le type de fibres ajoutés au béton (fibres de basalte, de polypropylène et d’acier), la fraction volumique des fibres (0, 0,5 et 1,0%) et les taux de renforcement des barres de PRFB (0,95 et 1,37%). Une comparaison entre les résultats expérimentaux et les modèles analytiques actuellement disponibles dans la littérature a été réalisée pour évaluer l'applicabilité de tels modèles pour prévoir la capacité des poutres testées en cisaillement. Les résultats de la présente étude indiquent que la géométrie des fibres joue un rôle important dans l'augmentation du nombre de fissures que celles observées dans les poutres contrôles. L'ajout de fibres a entraîné une défaillance plus ductile et le taux d'ouverture des fissures était retardé. La largeur de la fissure a diminué avec l'augmentation des ratios de renforcement longitudinal et des fractions volumiques des fibres. L'augmentation du taux de renforcement longitudinal a entraîné une rigidité plus élevée et a diminué les flèches à tous les stades du chargement. Les poutres coulées avec 1% de fibres de basalte, de polypropylène et d'acier ont montré une augmentation dans leurs capacités de cisaillement par rapport aux poutres contrôles d'environ 11, 16 et 63%, respectivement. Le type de fibres affectait de manière significative le gain dans les capacités de cisaillement des poutres, ce qui était attribué aux différentes propriétés physiques et mécaniques des fibres utilisées, telles que leurs dimensions, leurs géométries, et leurs mécanismes de liaison avec le béton. Les poutres coulées avec des fibres en acier à 0,5% présentaient des capacités de cisaillement plus élevées que celles coulées avec des fibres de basalte et de polypropylène de 23 et 16% respectivement, alors que les poutres coulées avec des fibres en acier à 1% de volume présentaient un gain de 47 et 41%, respectivement, dans leurs capacités. Les capacités de cisaillement prévues selon les équations de la norme CSA-S806-12 étaient conservatrices avec un rapport moyen Vprév/Vexp de 0,80 (écart type, ÉT = 0,12) pour les poutres sans fibres. Les modèles établis par Shin (1994) et Gopinath (2016) ont fourni de bonnes prévisions quant aux capacités de cisaillement des poutres en béton renforcé de fibres de basalte avec des ratios moyens Vprév/Vexp de 1,34 (ÉT = 0,09) et de 1,35 (ÉT = 0,07), respectivement. De même, le modèle de Shin (1994) a bien prédit les capacités de cisaillement des poutres en béton armé de fibres de polypropylène avec un rapport Vprév/Vexp de 1,34 (ÉT = 0,18). Les modèles de Gopinath (2016), Ashour A (1992) et Shin (1994) ont prédit les capacités de cisaillement des poutres en béton armé de fibres d'acier assez raisonnablement avec des ratio Vprév/Vexp de 1,01 (ÉT = 0,06), 1,07 (ÉT = 0,01) et 1,20 (ÉT = 0,08), respectivement. Un nouveau modèle a été proposé pour prédire les capacités de cisaillement des poutres en béton léger fibré renforcées par des barres longitudinales PRFB. Le modèle proposé prédit bien les capacités de cisaillement des poutres en béton léger (avec des fibres de basalte) avec un rapport Vprév/Vexp de 1,01 (ÉT = 0,05) et celles des poutres en béton léger (avec des fibres de polypropylène) avec un rapport Vprév/Vexp de 0,99 (ÉT = 0,06). Le facteur de liaison et la matrice de liaison d'interface utilisés étaient respectivement 0,75 et 4,18 MPa. En même temps, le modèle proposé prédit bien les capacités de cisaillement des poutres coulées avec des fibres d’acier avec un rapport Vprév/Vexp de 0,9 (ÉT = 0,00) quand le facteur de liaison et la matrice de liaison d'interface utilisés étaient respectivement 1,0 et 6,8 MPa.This study reports on the shear behavior of fiber-reinforced lightweight concrete (FRLWC) beams reinforced with basalt fiber-reinforced polymer (BFRP) bars. Ten beams (150x250x2400 mm) cast with concrete with and without fibers were tested under fourpoint loading configuration until failure occurred. Two beams were cast without fibers and acted as control while the other eight beams were cast with different types and percentages of fiber. The investigated parameters included the fiber type (basalt, polypropylene, and steel fibers), the fibers volume fraction (0, 0.5, and 1.0%), and the beams’ reinforcement ratios (0.95 and 1.37%). Comparison between the experimental results and the analytical models currently available in the literature was performed to assess the applicability of such models for LWC reinforced with BFRP bars. Based on the outcome of the current study, the geometry of fibers played an important role in increasing the number of cracks than those observed in the control beams. The addition of fibers led to a more ductile failure and the rate of crack opening was delayed. Crack width decreased with the increase of the longitudinal reinforcement ratios and the fibers’ volume fractions. Increasing the reinforcement ratio resulted in higher stiffness and decreased its deflection at all stages of loading. Beams cast with 1% of basalt, polypropylene, and steel fibers showed an increase in their shear capacities in compared to control beams about 11, 16, and 63%, respectively. The type of fibers significantly affected the gain in the shear capacities of the beams, which can be attributed to the different physical and mechanical properties of the fibers used such as aspect ratios, lengths, geometries, densities, and their bonding mechanisms. Beams cast with 0.5% steel fibers exhibited higher shear capacities than those cast with basalt and polypropylene fibers by 23 and 16%, respectively, whereas the beams cast with 1% steel fibers showed a gain by 47 and 41%, respectively. The predicted shear capacities according to CSA-S806-12 code provisions were conservative with an average ratio Vpred /Vexp of 0.80 (standard deviation, SD = 0.12) for beams without fibers. Good predictions for the shear capacities of the basalt-fiber reinforced concrete beams (BLWC) were provided by the models derived by Shin (1994) and Gopinath (2016) in which the ratios Vpred /Vexp were 1.34 (SD = 0.09) and 1.35 (SD = 0.07), respectively. Also, the model of Shin (1994) predicted well the shear capacities of the polypropylene-fiber reinforced concrete beams (PLWC) with a Vpred /Vexp ratio of 1.34 and SD of 0.18. The models of Gopinath (2016), Ashour A (1992), and Shin (1994) predicted the shear capacities of steel-fiber reinforced concrete beams (SLWC) fairly reasonable with a Vpred /Vexp ratio of 1.01 (SD = 0.06), 1.07 (SD = 0.01) and 1.20 (SD = 0.08), respectively. A new model was proposed to predict the shear capacities of FRWLC beams reinforced with BFRP longitudinal bars. The proposed model predicted well the shear capacities of BLWC beams with a Vpred /Vexp ratio of 1.01 (SD = 0.05) and those of PLWC beams with a Vpred /Vexp ratio of 0.99 (SD = 0.06). The bond factor and the interface bond matrix used were 0.75 and 4.18 MPa, respectively. The proposed model also predicted well the shear capacities of beams cast with SLWC with a Vpred /Vexp ratio of 0.9 when the bond factor and the interface bond matrix were taken equal to 1.00 and 6.8 MPa, respectively

The Spectrum of Glomerulonephritis in Adults in Madinah Munawarah Region

To evaluate the patterns of glomerular diseases in the Madinah region in Saudi Arabia we reviewed 85 biopsies from native kidneys of adult patients presenting with clinical and or biological features suggestive of glomerular disease. Only light microscopy was used to evaluate these biopsies. There were 62 males and 23 females with age ranging from 12 to 80 years (mean 28 <u> &#x002B;</u> 13.4 years). The main clinical presenting features were nephrotic syndrome in 68 patients (80&#x0025;), renal insufficiency in 31 (36.5&#x0025;), hypertension in 25 (24&#x0025;) and/or hematuria in 19 (22.4&#x0025;). Histopathology revealed minimal change disease in 25 patients (29&#x0025;), mesangioproliferative glomerulonephritis (GN) in 13 (15.3&#x0025;), focal segmental glomerulosclerosis in 13 (15.3&#x0025;), membranoproliferative GN in seven (8.2&#x0025;), membranous GN in three (3.5&#x0025;), diffuse proliferative GN in five (5.9&#x0025;), crescentic GN in four (4.7&#x0025;), lupus nephritis in 13 (15.3&#x0025;), and amyloidosis in two (2.4&#x0025;). In conclusion, Minimal change disease was the most common type of primary GN in our patients. The mean age for this group was 27.2 (range 13-43 years). Lupus nephritis was the commonest secondary GN in the Madinah region

Are patients aware of potential risks of weight reduction surgery? An internet based survey

Background/Aim: Obesity has become a global health care problem. In Saudi Arabia, up to 75% of adults are reportedly overweight. Morbid obesity has been associated with an increased risk of many comorbidities and mortality. Bariatric surgery is currently considered the most effective treatment option for morbid obesity. However, there are many concerns regarding the short and long-term complications of weight reduction surgery. It is unclear whether the general population is adequately aware of these risks. Therefore, we aimed to assess awareness of the general population of bariatric surgery complications. Although effective, bariatric surgery has been associated with many acute complications, reported in a range of 0.3% to 8% of operations. Patients and Methods: We performed a cross-sectional study between July and August of 2017 in Jeddah, Saudi Arabia. We used a 26-item, Arabic, electronically distributed questionnaire, to examine public awareness of the acute complications of bariatric surgery. Hypothesis testing was used to examine associations. Results: In total, 624 questionnaires were completed electronically. Mean age of participants was 25 (±13.2) and 66% were females. Of the surveyed population, 64% reported being aware of acute complications of bariatric surgery. Participants who had previously undergone a bariatric operation had a higher degree of awareness when compared to those who had not undergone a bariatric operation before (80.4% vs. 61.3%, P < 0.001). Females had higher awareness compared to males (70.8% vs. 52.1%, P < 0.001). Awareness of complications was not statistically different when stratified by level of education (P = 0.131) but occupation predicted awareness (P = 0.007). Conclusion: Two-thirds of the general population appears to be aware of the potential acute complications associated with bariatric surgery. Furthermore, awareness seems to be higher in females, individuals who had previously undergone weight reduction surgery, and health care workers

Threatened Prunus arabica in an ancient volcanic protected area of Saudi Arabia: Floristic diversity and plant associations

Prunus arabica (Oliv.) Meikle is an endangered shrub with a restricted distribution, which inhabits banks of flood flow channels in small sites of ancient volcanic activity dominated by black basaltic boulders within the Harrat Al-Harrah protectorate, Northern Saudi Arabia. It is with limited information about its ecology and hence, the present study is focusing on its phytosociological behavior and ecological features. The multi-methodological approach comprised species description, vegetation sampling and soil composition of 9 study sites at Harrat Al-Harrah protectorate. The application of TWINSPAN, DCA and CCA multivariate analyses led to identify 3 vegetation groups (VGI: Pulicaria undulata-Prunus arabica, VGII: Prunus arabica–Artemisia seiberi, VGIII: Artemisia seiberi-Achillea fragrantissima) associated with the distribution of P. arabica. The environmental variables that affect P. arabica and its main ecological features had been estimated and discussed. The present study concludes that the main reasons for its threatened and endangerment are seemingly due to overgrazing, poor rainfall, drought, shifting and destruction of its suitable habitat area. Keywords: Autecology, Endangered plant, Floristic diversity, Harrat Al-Harra

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population