Estudo da influência da forma dos detritos nas cavidades de erosão junto de pilares de pontes através do FLOW-3D

Frequentemente as pontes possuem fundações inseridas no leito dos rios constituído por material aluvionar. Em consequência, ficam sujeitas aos processos erosivos que se desenvolvem junto destas, aspeto que se agrava durante a ocorrência de cheias, por um lado, devido ao aumento de caudais e por outro, devido ao aumento dos detritos transportados pelo escoamento, que se acumulam junto aos elementos estruturais das pontes. Os detritos, maioritariamente materiais lenhosos flutuantes, podem levar à obstrução parcial dos seus vãos ou à acumulação juntos aos seus pilares e apresentam consequências em termos de redução de capacidade de vazão e de alteração da morfologia das cavidades de erosão, respetivamente. A dimensão, a forma e a localização dos detritos são características que devem ser consideradas na previsão da profundidade das cavidades de erosão. O presente estudo, dando valor ao avanço que as tecnologias proporcionam através da modelação numérica, pretende contribuir para alargar o conhecimento sobre a influência que os detritos têm na profundidade das cavidades de erosão junto de pilares cilíndricos, para escoamentos sem transporte sólido generalizado, recorrendo para o efeito ao programa FLOW-3D. Neste âmbito, foi realizada a modelação numérica do canal hidráulico existente no Laboratório de Hidráulica Fluvial e das Estruturas da Universidade da Beira Interior. A primeira fase do trabalho teve como objetivo calibrar o modelo computacional com o modelo experimental e validar os resultados obtidos pela simulação numérica; a segunda fase visou analisar o impacto causado pelos detritos nas cavidades de erosão. Para isso, foram realizadas 5 simulações: a primeira para um pilar isolado, sem a presença de detritos, e as seguintes com a presença de detritos nas suas formas mais comuns, triangular e retangular. Os resultados obtidos através do FLOW-3D permitiram constatar que os detritos simulados com a caixa retangular flutuante origina maior profundidade máxima da cavidade de erosão e que os detritos simulados com a caixa triangular no fundo foi a que apresentou menor profundidade máxima da cavidade de erosão, tal como verificado em ensaios experimentais. No entanto, os resultados obtidos através do FLOW-3D são significativamente inferiores aos obtidos experimentalmente, ~ 30 %.Frequently the bridges have foundations inserted in riverbeds constituted by alluvial material. As a consequence, they are subject to the erosive processes that take place next to them, aspect that is aggravated during the occurrence of floods, on one hand, due to the increase of the flow and on the other, due to the increase of the debris carried by the flow, that accumulate together of the bridge structural elements. The debris, mainly floating woody materials, can lead to the partial obstruction of their spans or accumulation near their bridge piers and have consequences in terms of reduction of flow capacity and alteration of the morphology of scour hole, respectively. The dimensions, shape and location of the debris are characteristics that must be considered when predicting the scour hole depth. The present study, giving value to the advances that the technologies provide through numerical modelling, intends to contribute to extend the knowledge about the influence that the debris has on the scour depth near cylindrical piers, under clear-water flow conditions, using the FLOW-3D program. In this context, the numerical modelling of the hydraulic channel existing in the Fluvial Hydraulics and Structures Laboratory of the University of Beira Interior was carried out. The first phase of the work had as objective to calibrate the computational with the experimental model and to validate the results obtained by the numerical simulation; the second phase aimed to analyse the impact caused by the debris in the scour cavities. For this, 5 simulations were performed: the first for an isolated pier, without the presence of debris, and the following with the presence of debris in its most common forms, triangular and rectangular. The results obtained through FLOW-3D showed that the debris simulated with the floating rectangular box causes a greater maximum scour depth and the debris simulated with the triangular box in the bottom was the one that presented smaller scour depth, as verified in experimental tests. However, the results obtained through FLOW-3D are significantly lower than those obtained experimentally, 30 %

Flow-3D Modelling of the Debris Effect on Maximum Scour Hole Depth at Bridge Piers

Bridge foundations are frequently inserted in riverbeds constituted by alluvial material, being, therefore, subjected to scouring processes. Such phenomenon is aggravated during flood events due to the increase of water flow or due to the increase of the debris carried by the flow that can pile up along the bridge structural elements. The debris can partially obstruct bridge spans and accumulate near bridge piers and abutments, which will have consequences in terms of reduction of flow capacity and an increment of the maximum scour depth. The dimensions, shape and its location are characteristics that must be considered when predicting the scour depth. The present study aims at analyzing the effect of the debris on the maximum clear-water scour depth at cylindrical piers inserted in uniform sand, non-ripple forming sand, fully-developed turbulent flows in wide rectangular channel, using computational fluid dynamics software, Flow-3D. For this purpose, debris with a triangular and rectangular shape, floating and on the sand bed, were tested, using the k-ε RNG turbulence model and the numerical results were compared with those obtained experimentally. It was possible to verify that the floating debris gives greater scour hole depth and the debris on sand bed behave as scour countermeasure reducing the scour hole depth. Also, rectangular shaped debris seems to cause more scour near the structures than the triangular shaped ones, which also seemed beneficial to the scour hole, by reducing it. However, the results obtained computationally are significantly lower than those obtained experimentally.info:eu-repo/semantics/publishedVersio

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research