10 research outputs found
Study on mechanical properties and strength relation between cube and cylinder specimens of steel fiber reinforced concrete
Experimental investigation of the behaviour of spiral steel fibre reinforced concrete beams subjected to drop-weight impact loads
Concrete is a brittle material with much lower strength in tension as compared to that in compression. Adding fibres into concrete mix has been intensively investigated to increase the ductility, the crack control and energy absorption capabilities. A new type of steel fibre with spiral shape has been proposed recently. It has been demonstrated by laboratory tests that the spiral-shaped fibres have larger displacement capacity and provide better bonding into the concrete mix compared to other types of fibres such as hooked-end, deformed and corrugated fibres. The present study carries out drop-weight impact tests to study the structural responses of concrete beams reinforced with different types of steel fibres. Plain concrete and concrete reinforced by the commonly used hooked-end steel fibres and the proposed spiral-shaped steel fibres were tested. Two volume fractions, i.e. 0.5 and 1.0 %, of fibres were used to prepare steel fibre reinforced concrete (SFRC) specimens. Ø100–200 mm cylindrical specimens were also prepared and tested to determine the static properties of the concretes. Centre-point flexural tests were conducted on 100 × 100 × 350 mm beams with span length of 300 mm under drop-weight impact loads.The static tests were carried out using hydraulic testing machine and the impact tests were conducted using an instrumented drop-weight testing system. A 15.2 kg hard steel was used as the drop-weight impactor. Two drop heights, namely 0.5 and 1.0 m, were adopted in performing the repeated impact tests. The high-speed camera, fast-response load cells and laser linear variable differential transformers were used to record the failure processes, forces and displacements of the tested specimens under impact loads. The force–displacement relations and the corresponding energy absorption capabilities of the SFRC beams were obtained, compared and discussed. The advantage and effectiveness of the spiral-shaped steel fibres in increasing the performance of SFRC beam elements under impact loads are examined
Shear Tests for Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) Beams with Shear Reinforcement
Oridonin exerts anticancer effect on osteosarcoma by activating PPAR-γ and inhibiting Nrf2 pathway
Surface functionalization and biomolecule immobilization using plasma-generated free radicals on polypropylene
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Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study
We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care