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Nuclear and gas turbine power plants, computer chips, and other devices and industries are running hotter than ever for longer than ever. With no apparent end to the trend, the potential arises for a phenomenon known as thermotransport to cause undesirable changes in these high temperature materials. The diffuse-interface method known as the phase-field model is a useful tool in the simulation and prediction of thermotransport driven microstructure evolution in materials. The objective of this work is to develop a phase-field model using practical and empirical properties of thermodynamics and kinetics for simulating the interdiffusion behavior and microstructural evolution of single and multiphase binary alloy system under composition and/or temperature gradients. Simulations are carried out using thermodynamics and kinetics of real systems, such as the U-Zr solid metallic fuel, with emphasis on the temperature dependencies of the kinetics governing diffusional interactions in single-phase systems and microstructural evolution in the presence of multiple driving forces in multi-phase systems. A phase field model is developed describing thermotransport in the γ phase of the U-Zr alloy, a candidate for advanced metallic nuclear fuels. The model is derived using thermodynamics extracted from the CALPHAD database and temperature dependent kinetic parameters associated with thermotransport from the literature. Emphasis is placed upon the importance of the heat of transport, Q*, and atomic mobility, β. Temperature dependencies of each term are estimated from empirical data obtained directly from the literature, coupled with the textbook phenomenological formulae of each parameter. A solution is obtained via a finite volume approach with the aid of the FiPy® partial differential equation solver. Results of the simulations are described based on individual flux contributions from the gradients of both composition and temperature, and are found to be remarkably similar to experimental results from the literature. iv In an additional effort the thermotransport behavior of a binary two-phase alloy is modeled, for the first time, via the phase-field method for a two-phase (γ + β) U-Zr system. The model is similarly built upon CALPHAD thermodynamics describing the γ and β phases of the U-Zr system and thermotransport parameters for the γ phase from literature. A parametric investigation of how the heats of transport for U and Zr in the β phase affect the redistribution is performed, and the interplay between system kinetics and thermodynamics are examined. Importantly, a strict control over the microstructure that is placed into the temperature gradient ( ) is used to eliminate the randomness associated with microstructural evolution from an initially unstable state, allowing an examination of exactly how the β phase thermotransport parameters affect the redistribution behavior of the system. Results are compared to a control scenario in which the system evolves only in the presence of thermodynamic driving forces, and the kinetic parameters that are associated with thermotransport are negligible. In contrast to the single-phase simulations, in the presence of a large thermodynamic drive for phase transformation and stability, the constituent redistribution caused by the thermotransport effect is comparatively smaller.

An investigation on the application of hybrid glass fibre reinforced polymer (GFRP) and steel bars bars as longitudinal reinforcement for simple and continuous concrete beams is presented. Three simply and eleven multi-spans continuous reinforced concrete beams were constructed and tested to failure. Nine continuous and two simply supported beams were reinforced with a hybrid combination of both GFRP and steel re-bars at mid spans and internal support regions. In addition, two continuous concrete beams reinforced with either GFRP or steel bars and one simply supported beam reinforced with GFRP bars were tested as control beams. The beams were classified into two groups according to the reinforcement configurations. All specimens tested were 200 mm in width and 300 mm in depth. The continuous beams comprised of two equal spans, each of 2600 mm, while the simply supported beams had a span of 2600 mm. Unlike GFRP reinforced concrete beams, the hybrid and steel reinforced concrete beams failed in a favourable ductile manner and demonstrated narrow cracks and smaller deflections compared to the GFRP-reinforced control beam. The lower stiffness and higher deflection of GFRP reinforced concrete beams can be controlled and improved by the use of steel reinforcement in combination with GFRP re-bars. However, the ratio of GFRP to steel reinforcement is a key factor to ensure sufficient ductility and stiffness beyond the first cracking stage. The experimental results showed that the extent of moment redistribution in hybrid reinforced continuous beams depends mainly on the amount of hybrid reinforcement ratio in critical sections. Similar area of steel and GFRP bars in critical sections leads to limited moment redistribution whereas different amount of steel and FRP bars in critical sections leads to a remarkable moment redistribution. Design guidelines and formulas have been validated against experimental results of hybrid GFRP/steel reinforced concrete beams tested. The Yoon’s equation reasonably predicted the deflections of the hybrid beams tested whereas Qu’s model which is based on ACI 440.1R-15 underestimated the deflections of hybrid beams tested at all stage of loading after cracking. The ACI 440.2R-08 and Pang et al., (2015) equations reasonably predicted the sagging failure moment in most continuous hybrid reinforced concrete beams, whereas they underestimated the hogging flexural strength at failure of most hybrid continuous beams. On the other hand, the formulas proposed by Yinghao et al., (2013) was very conservative in predicting the failure moment at the critical sagging and hogging sections. On the analytical side, a numerical technique consisting of sectional analyses has been developed to predict the moment–curvature relationship and moment capacity of hybrid FRP/ steel reinforced concrete members. The numerical technique has been validated against the experimental test results obtained from the current research and those reported in the literature. In addition, a two-dimensional nonlinear finite element model was proposed using ABAQUS package. The proposed model was validated against the experimental results of the beams tested in the present research. / Higher Education Institute in the Libyan Government

yes / The main purpose of this paper is to assess moment redistribution in continuous concrete beams reinforced with fibre reinforced polymer (FRP) bars. A numerical technique based on equilibrium of forces and full compatibility of strains has been developed to evaluate the moment–curvature relationships and moment capacities of FRP and steel reinforced concrete sections. Moment redistribution has then been assessed by comparing elastic and experimental moments at failure, and moment capacity at critical sections of continuous FRP reinforced concrete beams reported on the literature. The curvature of under reinforced FRP sections was large at FRP rupture but failure was sudden, that would not allow any moment redistribution. On the other hand, FRP over reinforced sections experienced higher curvature at failure than steel over reinforced sections owing to the lower FRP modulus of elasticity. Although the experimental and elastic bending moment distributions at failure are significantly different for many beams tested elsewhere, in particular CFRP reinforced concrete beams, the experimental bending moment over the middle support at failure was far lower than the corresponding moment capacity owing to the de-bonding of FRP bars from concrete in the middle support region. Furthermore, the hogging moment redistribution over the middle support is always larger than that at mid-span by around 66%. It was also shown that the load capacity prediction of continuous FRP reinforced concrete beams using the de-bonding moment at the middle support section was the closest to the experimental failure load.

Yes / This paper presents test results of six full scale reinforced concrete continuous T beams. One beam was reinforced with glass fibre reinforced polymer (GFRP) bars while the other five beams were reinforced with a different combination of GFRP and steel bars. The ratio of GFRP to steel reinforcement at both mid-span and middle-support sections was the main parameter investigated. The results showed that adding steel reinforcement to GFRP reinforced concrete T-beams improves the flexural stiffness, ductility and serviceability in terms of crack width and deflection control. However, the moment redistribution at failure was limited because of the early yielding of steel reinforcement at a beam section that does not reach its moment capacity and could still carry more loads due to the presence of FRP reinforcement. The experimental results were compared with the ultimate moment prediction of ACI 440.2R-17, and with the existing theoretical equations for deflection prediction. It was found that the ACI 440.2R-17 reasonably estimated the moment capacity of both mid-span and middle support sections. Conversely, the available theoretical deflection models underestimated the deflection of hybrid reinforced concrete T-beams at all load stages.

Yes / The current paper aimed at investigating the flexural performance of five large-scale continuous concrete beams reinforced by both steel bars and glass fibre reinforced polymer (GFRP). All the studied specimens had the same geometrical dimensions, with 200mm width, 300mm depth, and two identical spans of 2600mm. The quantity of longitudinal steel reinforcement, GFRP reinforcement, and hybrid reinforcement ratio at the top and bottom layers of beams were the key parameters explored in this study. The experimental findings indicated that using the hybrid reinforcement of steel and GFRP in multi-span continuous concrete beams exhibited a ductile behaviour. However, the hybrid ratio of steel bars/GFRP is critical for restricting the extent of moment redistribution ratios. Moreover, using the same hybrid reinforcement ratios at sagging and hogging regions led to a limited moment redistribution. On the other hand, the hybrid beams strengthened by various hybrid ratios in the critical sections of the tested beams demonstrated a remarkable moment redistribution up to 43%. The test results were compared with the available theoretical model and equations for predicting the beams’ moment capacity. It was found that the ACI.440.2R-08 reasonably predicted the flexural capacity of tested beams whereas the Yinghao and Yong equation underestimated the flexural capacity in the hogging sections. It was also shown that using the collapse mechanism with plastic hinges at sagging and hogging sections yielded good predictions for the loading capacity of hybrid reinforced concrete continuous beams.

L'anesthésie générale est associée à une altération significative de la thermorégulation normale. L'augmentation de température cutanée avec pré-réchauffement réduit la redistribution durant l'anesthésie. Les principaux objectifs étaient: 1) étudier l'efficacité de stratégies de pré-réchauffement pendant l'anesthésie; 2) comparer l'efficacité du réchauffement actif au réchauffement passif et 3) évaluer l'efficacité du pré-réchauffement pour prévenir l'hypothermie après prémédication intramusculaire. Dans une étude prospective, croisée de 17 rats adultes, trois stratégies de préchauffage ont été évaluées : PW1% (augmentation température de 1%), PW40 (augmentation à 40°C) et NW (pas de réchauffement). Le pré-réchauffement a efficacement retardé l'atteinte du seuil d’hypothermie (7.1 minutes pour le groupe NW vs 12.4 minutes et 19.3 minutes pour PW1% et PW40, respectivement). Ces temps étaient significativement différents entre groupes: PW1% vs PW40 (p = 0.0044 (95% CI -12 à -2.2), PW40 vs NW (p < 0.0001 (95%CI 8.1 à 16.0) et PW1% vs NW (p = 0.003, 95%CI 1.8 à 8.7). Dans une étude prospective, randomisée, croisée et expérimentale sur 8 rats, le réchauffement actif (coussin chauffant) a été comparé au réchauffement passif (couverture) après pré-réchauffement (augmentation température centrale de 1%). La température a été maintenue plus adéquatement dans le groupe actif pendant (P = 0,008 [95%CI 3,2 à 20,4]) et après l'anesthésie (P = 0,002 [95%CI 4,2 à 17,7]). Dans une étude prospective, randomisée, croisée, une sédation intramusculaire (kétamine-midazolam-hydromorphone) a été administrée à 8 rats suivi d’une période de 14 minutes en cage non chauffée ou boîte chauffée. Une période d’anesthésie de 30 minutes avec soutien thermique a suivi. Au début du réveil, les rats chauffés avaient une température plus élevée (2/8 rats hypothermiques vs 6/8 rats non chauffés (P < 0.0001)) / General anesthesia is associated with a significant alteration of normal thermoregulation. Increasing skin temperature with pre-warming reduces heat redistribution during anesthesia. The main objectives were: 1) to study the effectiveness of prewarming strategies during anesthesia; 2) to compare the effectiveness of active versus passive warming; and 3) to evaluate the effectiveness of prewarming in preventing hypothermia after intramuscular premedication. In a prospective, crossover study of 17 adult rats, three prewarming strategies were evaluated: PW1% (1% temperature increase), PW40 (increase to 40°C), and NW (no warming). Pre-warming effectively delayed reaching hypothermia threshold (7.1 minutes for the NW group, compared to 12.4 minutes and 19.3 minutes for the PW1% and PW40 groups, respectively). These times were significantly different between groups: PW1% vs PW40 (p = 0.0044 (95%CI -12 to -2.2), PW40 vs NW (p < 0.0001 (95%CI 8.1 to 16.0) and PW1% vs NW (p = 0.003, 95%CI 1.8 to 8.7). In a prospective, randomized, crossover, experimental study of 8 rats, active warming (heating pad) was compared with passive warming (blanket) after pre-warming (1% core temperature increase). Temperature was more adequately maintained in the active group during (P = 0.008 [95%CI 3.2 to 20.4]) and after anesthesia (P = 0.002 [95%CI 4.2 to 17.7]). In a prospective, randomized, crossover study, intramuscular sedation (ketamine-midazolam-hydromorphone) was administered to 8 rats followed by a 14-minute period in an unheated cage or heated box. A 30-minute period of anesthesia with thermal support followed. At the onset of awakening, heated rats had a higher temperature (2/8 hypothermic rats vs 6/8 unheated rats (P < 0.0001))