Saudi Cultural Missions Theses & Dissertations
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Item Restricted EFFECTS OF HIGH-STRENGTH REINFORCEMENT ON SHEAR-FRICTION WITH DIFFERENT INTERFACE CONDITIONS AND CONCRETE STRENGTHS(Purdue University Graduate School, 2023-10-13) Alimran, Ahmed Abdulhameed; Williams, ChristopherReinforced concrete elements are vulnerable to sliding against each other when shear forces are transmitted between them. Shear-friction is the mechanism by which shear is transferred between concrete surfaces. It develops by aggregate interlock between the concrete interfaces while reinforcement crossing the shear interface or normal force due to external loads contributes to the shear resistance. Current design provisions used in the United States (ACI 318-19, AASHTO LRFD (2020), and the PCI Design Handbook (2017)) include design expression for shear-friction capacity. However, the value of the reinforcement yield strength input into the expressions is limited to a maximum of 60 ksi. Furthermore, the concrete strength is not incorporated into the primary design expressions. These limits cause the potential contribution of high-strength reinforcement and high-strength concrete in shear-friction applications from being considered. Therefore, a research program was developed to investigate the possibility of improving current shear-friction design practice and addressing these current limits. Specifically, an experimental program was conducted to evaluate the influence of high-strength reinforcement and high-strength concrete on shear-friction strength. In addition, a statistical analysis was performed using a comprehensive shear-frication database comprised of past tests available in the literature. The experimental program consisted of two phases. Phase I included 24 push-off specimens to study the influence of the yield strength of the interface reinforcement (Grade 60 and Grade 100) and the number and size of interface reinforcing bars (6-No.4 and 4-No. 5 bars) with three different interface conditions (rough, smooth, and shear-key). Phase II included 20 push-off specimens with rough interfaces to investigate the influence of the yield strength of the interface reinforcement (Grade 60 and Grade 100) and concrete strength (target strengths of 4000 psi and 8000 psi). The influence of these two variables was observed over a range of reinforcement ratios (ρ = 0.55%, 0.83%, 1.11%, and 1.38%). The test results showed that the overall shear-friction strength was the greatest for rough interface specimens, followed by specimens detailed with shear keys. The smooth interface specimens had the lowest strengths. The results of both phases of the experimental program indicated that the use of high-strength reinforcement did not improve shear-friction capacity. Furthermore, the results from the Phase II tests showed that increasing the concrete compressive strength led to increased shear-friction capacity. The test results from the experimental program were analyzed and compared with current design provisions, which demonstrated room for improvement of current design practice. Following the experimental program, a comprehensive shear-friction database was analyzed, and multilinear regression was used to create a model to predict shear-friction strength. Factors were then applied to the model to provide acceptable design expressions for shear-friction strength (less than 5% unconservative estimates). The database was used to evaluate the factored model and current design provisions. The research outcomes, especially the expressions for shear-friction strength that were developed and that include consideration of the concrete compression strength, along with the shear-friction tests demonstrating the lack of strength gain with the use of Grade 100 reinforcement, provide valuable information for the concrete community to help direct efforts toward improving current shear-friction design practice.18 0Item Restricted Comprehensive assessment of myocardial ischaemia: from vessel to patient.(Saudi Digital Library, 2023-10-12) Albaraikan, Abdulaziz Mohammed; Gunn, JulianChronic coronary syndrome (CCS) is accompanied by angina and limitation to the patient’s life. The significance of coronary blood flow reduction is currently best assessed by fractional flow reserve (FFR) as a guide to intervention. The beneficial effect of percutaneous coronary intervention (PCI) in these patients has been challenged, and therefore fresh evaluation of the changes in response to PCI is needed. Using real-world data from 40 patients, detailed examination of coronary anatomy and physiology, using FFR and computational fluid dynamics (CFD) to assess absolute coronary flow, was conducted. Patients not undergoing PCI due to FFR negative lesions comprised the ‘control’ group. A novel method to assess the myocardial ischemic burden and address the global flow reduction named ‘cumulative FFR’ (FFRCUM) was developed. Fitness trackers monitored everyday physical activity, and six-minute walk tests were performed, before and three months after the procedure. Questionnaires were used to evaluate the change as reported by the patients. I found a clear and significant physiological improvement following PCI in FFR, hyperaemic stenosis resistance (HSR), microvascular resistance (MVR), absolute flow (which increased 80%) and FFRcum (which increased from 0.72 to 0.83). The change in FFRcum was a predictor of the change in quality of life at follow up. Improvement in spontaneous and observed physical activity, which was highly variable between patients, was minimal, with similar findings in PCI and ‘control' patients. This was also observed with questionnaires in all domains except angina frequency. Taken together, this work shows that physiological improvement (FFR and FFRcum), and absolute flow restoration, are achieved with FFR-guided PCI. However, that does not necessarily result in measured improvement in everyday physical activity, or self-reported general health status, but it does result in improved angina status, at three months. Overall, these findings indicate that physiological improvements in myocardial perfusion produced by PCI tend not to lead to a major change in objective measures of activity or wellbeing in everyday life, but are worth pursuing in terms of angina, specifically14 0