AbstractThis paper discusses the lateral load behavior of two, 0.40-scale, hybrid, precast concrete shear wall test specimens and the behavior of a third precast specimen designed to emulate ...monolithic cast-in-place RC shear walls. The walls had identical overall geometry and were constructed by placing rectangular precast panels across horizontal joints. The hybrid walls used mild steel bars Grade 400 (U.S. Grade 60) and high-strength unbonded posttensioning (PT) strands for lateral resistance, whereas the emulative wall used only mild steel bars. The mild steel bars crossing the base joint were designed to yield and provide energy dissipation, with the PT steel in the hybrid walls reducing the residual displacements of the structure. The mild steel bars at the base of the emulative wall and one of the hybrid walls used Type II mechanical splices, while the other hybrid wall used continuous bars grouted into the foundation. Because of the lack of PT steel, the emulative wall developed a large residual uplift at the base joint, resulting in excessive horizontal slip and strength degradation. The behavior of the hybrid wall with Type II splices was also limited, which occurred because of the pullout of the mild steel bars. In contrast, the hybrid wall with continuous mild steel bars showed superior restoring, energy dissipation, and ductile behavior over larger lateral displacements. The results show the potential for the use of precast walls in seismic regions, while also revealing important detailing considerations.
Recent discussion has focused on questions related to the repeal and replacement of portions of the Affordable Care Act (ACA). However, issues central to the future of health and health care in the ...United States transcend the ACA provisions receiving the greatest attention. Initiatives directed to certain strategic and infrastructure priorities are vital to achieve better health at lower cost.
To review the most salient health challenges and opportunities facing the United States, to identify practical and achievable priorities essential to health progress, and to present policy initiatives critical to the nation's health and fiscal integrity.
Qualitative synthesis of 19 National Academy of Medicine-commissioned white papers, with supplemental review and analysis of publicly available data and published research findings.
The US health system faces major challenges. Health care costs remain high at $3.2 trillion spent annually, of which an estimated 30% is related to waste, inefficiencies, and excessive prices; health disparities are persistent and worsening; and the health and financial burdens of chronic illness and disability are straining families and communities. Concurrently, promising opportunities and knowledge to achieve change exist. Across the 19 discussion papers examined, 8 crosscutting policy directions were identified as vital to the nation's health and fiscal future, including 4 action priorities and 4 essential infrastructure needs. The action priorities-pay for value, empower people, activate communities, and connect care-recurred across the articles as direct and strategic opportunities to advance a more efficient, equitable, and patient- and community-focused health system. The essential infrastructure needs-measure what matters most, modernize skills, accelerate real-world evidence, and advance science-were the most commonly cited foundational elements to ensure progress.
The action priorities and essential infrastructure needs represent major opportunities to improve health outcomes and increase efficiency and value in the health system. As the new US administration and Congress chart the future of health and health care for the United States, and as health leaders across the country contemplate future directions for their programs and initiatives, their leadership and strategic investment in these priorities will be essential for achieving significant progress.
•Regional variability in RCA and RAC properties was investigated across a wide range.•Strength of RAC decreased 16.6% at 50% replacement and 26.4% at 100% replacement.•Stiffness of RAC decreased ...26.4% at 50% replacement and 34.4% at 100% replacement.•RCA absorption and deleterious material were primary strength/stiffness predictors.•Coarse aggregate gradation impacted RAC similarly to impacts noted for NA concrete.
By crushing old concrete to make recycled concrete aggregates (RCA) for use in new concrete, the overall environmental impacts of concrete are reduced. However, a better understanding of the use of RCA in new concrete is necessary before adoption in structural concrete applications can be widely realized. In particular, the strength, stiffness (Modulus of Elasticity), workability, and durability of concrete using RCA can be different than concrete that uses natural aggregate (NA). Variability in RCA properties from source to source also must be addressed if guidelines for RCA use are to be adopted. This paper describes properties of RCA and recycled aggregate concrete (RAC) with materials from four distinct areas of the United States (Northeast, South, Midwest and Southwest regions), making this study the most geographically varied study of RCA known. Variability in aggregate properties and the relationships between them are addressed within the paper. Equations allowing concrete mix designers to predict strength and stiffness of mixes are shown to be applicable across a much broader range of RCA properties than previously known. Similarly to concrete with natural aggregates, the strength and stiffness of RAC is shown to be impacted by the gradation of the coarse aggregates – smaller aggregates make stronger, stiffer concrete.
This paper presents the measured behavior from the testing of a 0.4-scale “hybrid” precast concrete wall specimen under reversed-cyclic lateral loading and provides an assessment of the seismic ...design and analysis of the wall by using the experimental results. The hybrid precast wall system investigated in the paper utilizes a combination of mild (i.e., Grade 400) steel and high-strength unbonded posttensioning (PT) steel for lateral resistance across horizontal joints. A seismic design procedure that conforms to ACI 318 and ACI ITG-5.2 was used for the design of the test specimen based on ACI ITG-5.1. The behavior of the specimen was measured with conventional data acquisition techniques and also full-field digital image correlation of the base panel and the critical joint between the base panel and the foundation, providing unprecedented information on the wall performance. The paper compares these measurements with the design and analytical predictions, focusing specifically on the applied lateral load and displacement, energy dissipation, behavior of the steel reinforcement, and behavior along the horizontal joints. The test specimen was not able to reach the expected ultimate drift level owing to a combination of poor unconfined concrete strength and poor placement of the confinement reinforcement at the toes. However, the performance of the wall up to the failure point was consistent with the predicted behavior based on both the design procedure and the analytical models.
Until recently, when anthrax triggered a concern about preparedness in the public health infrastructure, U.S. health policy and health spending had been dominated by a focus on payment for medical ...treatment. The fact that many of the conditions driving the need for treatment are preventable ought to draw attention to policy opportunities for promoting health. Following a brief review of the determinants of population health-genetic predispositions, social circumstances, environmental conditions, behavioral patterns, and medical care-this paper explores some of the factors inhibiting policy attention and resource commitment to the nonmedical determinants of population health and suggests approaches for sharpening the public policy focus to encourage disease prevention and health promotion.
Background In this Position Statement, the International Society of Sports Nutrition (ISSN) provides an objective and critical review of the literature pertinent to nutritional considerations for ...training and racing in single-stage ultra-marathon. Recommendations for Training. i) Ultra-marathon runners should aim to meet the caloric demands of training by following an individualized and periodized strategy, comprising a varied, food-first approach; ii) Athletes should plan and implement their nutrition strategy with sufficient time to permit adaptations that enhance fat oxidative capacity; iii) The evidence overwhelmingly supports the inclusion of a moderate-to-high carbohydrate diet (i.e., ~ 60% of energy intake, 5-8 g·kg
·d
) to mitigate the negative effects of chronic, training-induced glycogen depletion; iv) Limiting carbohydrate intake before selected low-intensity sessions, and/or moderating daily carbohydrate intake, may enhance mitochondrial function and fat oxidative capacity. Nevertheless, this approach may compromise performance during high-intensity efforts; v) Protein intakes of ~ 1.6 g·kg
·d
are necessary to maintain lean mass and support recovery from training, but amounts up to 2.5 g.kg
·d
may be warranted during demanding training when calorie requirements are greater; Recommendations for Racing. vi) To attenuate caloric deficits, runners should aim to consume 150-400 Kcal·h
(carbohydrate, 30-50 g·h
; protein, 5-10 g·h
) from a variety of calorie-dense foods. Consideration must be given to food palatability, individual tolerance, and the increased preference for savory foods in longer races; vii) Fluid volumes of 450-750 mL·h
(~ 150-250 mL every 20 min) are recommended during racing. To minimize the likelihood of hyponatraemia, electrolytes (mainly sodium) may be needed in concentrations greater than that provided by most commercial products (i.e., > 575 mg·L
sodium). Fluid and electrolyte requirements will be elevated when running in hot and/or humid conditions; viii) Evidence supports progressive gut-training and/or low-FODMAP diets (fermentable oligosaccharide, disaccharide, monosaccharide and polyol) to alleviate symptoms of gastrointestinal distress during racing; ix) The evidence in support of ketogenic diets and/or ketone esters to improve ultra-marathon performance is lacking, with further research warranted; x) Evidence supports the strategic use of caffeine to sustain performance in the latter stages of racing, particularly when sleep deprivation may compromise athlete safety.
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