Behaviour of frictional joints in steel arch yielding supports

The loading capacity and ability of steel arch supports to accept deformations from the surrounding rock mass is influenced significantly by the function of the connections and in particular, the tightening of the bolts. This contribution deals with computer modelling of the yielding bolt connections for different torques to determine the load-bearing capacity of the connections. Another parameter that affects the loading capacity significantly is the value of the friction coefficient of the contacts between the elements of the joints. The authors investigated both the behaviour and conditions of the individual parts for three values of tightening moment and the relation between the value of screw tightening and load-bearing capacity of the connections for different friction coefficients. ANSYS software and the finite element method were used for the computer modelling. The solution is nonlinear because of the bi-linear material properties of steel and the large deformations. The geometry of the computer model was created from designs of all four parts of the structure. The calculation also defines the weakest part of the joint’s structure based on stress analysis. The load was divided into two loading steps: the pre-tensioning of connecting bolts and the deformation loading corresponding to 50-mm slip of one support. The full Newton-Raphson method was chosen for the solution. The calculations were carried out on a computer at the Supercomputing Centre VSB-Technical University of Ostrava.Nośność stalowych podpór łukowych i ich zdolność do przenoszenia odkształceh spowodowa-nych przez sąsiadujące warstwy skalne w dużej mierze uwarunkowana jest przez działanie polączeh, w szczególności przez silę dokręcenia srub. Praca niniejsza zajmuje się modelowaniem komputerowym podatnych polączeh śrubowych dla róznych momentów skręcających w celu określenia wielkości obcią-żeh przenoszonych przez polączenią Innym parametrem w znacznym stopniu warunkującym nośnosc jest wartość wspólczynnika tarcia na polączeniach pomiędzy komponentami zlączy. Autorzy zbadali zachowanie i warunki pracy poszczególnych elementów dla trzech wartości momentu dokręcającego, a także zbadali związek pomiędzy stopniem dokręcenia śruby a nośnością całego polączenia dla róznych wartości wspólczynnika tarcią W modelowaniu komputerowym wykorzystano oprogramowanie ANSYS oraz metodę elementów skohczonych. Rozwiązanie problemu jest nieliniowe ze względu na bi-liniowe właściwości materiałowe stali i z uwagi na wielkosc odkształceń. Geometric modelu komputerowego stworzono na podstawie projektów wszystkich czterech elementów konstrukcji. Obliczenia pozwalają także na zidentyfikowanie najsłabszego elementu w polączeniu w oparciu o analizę wytrzymałościową. Obciązenie przykładane podzielono na dwa etapy: wstępne napręzenie śrub i obciązenie odkształcające odpowiadające 50-mm przesunięciu jednej z podpór. W rozwiązaniu wykorzystano pełną metodę New-tona-Raphsoną Obliczenia przeprowadzono na komputerze w centrum obliczeniowym Supercomputing Centre na Uniwersytecie Technicznym w Ostravie.Web of Science59379278

Simulation of laboratory tests of steel arch support

The total load-bearing capacity of steel arch yielding roadways supports is among their most important characteristics. These values can be obtained in two ways: experimental measurements in a specialized laboratory or computer modelling by FEM. Experimental measurements are significantly more expensive and more time-consuming. However, for proper tuning, a computer model is very valuable and can provide the necessary verification by experiment. In the cooperating workplaces of GIG Katowice, VSB-Technical University of Ostrava and the Institute of Geonics ASCR this verification was successful. The present article discusses the conditions and results of this verification for static problems. The output is a tuned computer model, which may be used for other calculations to obtain the load-bearing capacity of other types of steel arch supports. Changes in other parameters such as the material properties of steel, size torques, friction coefficient values etc. can be determined relatively quickly by changing the properties of the investigated steel arch supports.Najważniejszymi parametrami wytrzymałościowymi stalowych, podatnych odrzwi obudowy wyrobisk korytarzowych jest ich maksymalna i robocza nośność. Wartości tych nośności mogą być określane dwoma sposobami: do świadczalnie, w specjalistycznym laboratorium badawczym lub za pomocą modelowania komputerowego metodą elementów skończonych (MES). Badania laboratoryjne odrzwi są drogie i czasochłonne, jednak dla kalibracji i weryfikacji modelu numerycznego wyniki tych badań są niezbędne. Weryfikację tą, zakończoną sukcesem, przeprowadzono we współpracy Głównego Instytutu Górnictwa w Katowicach, Technicznego Uniwersytetu VSB w Ostrawie oraz Instytutu Geoniki ASCR w Ostrawie. Niniejszy artykuł przedstawia przebieg procesu kalibracji modelu numerycznego odrzwi w warunkach obciążeń statycznych. W efekcie tych działań uzyskano model komputerowy odrzwi odwzorowujący ich pracę w stanowisku badawczym. Opracowany model może być wykorzystywany do obliczania nośności innych typów odrzwi. Zmiany parametrów odrzwi wpływających na ich nośność, takich jak własności mechaniczne stali, wielkość momentu dokręcenia nakrętek śrub strzemion, współczynnik tarcia itp. mogą być zmieniane w modelu stosunkowo szybko.Web of Science62117616

The Effects of Subchronic Exposure to Terbuthylazine on Early Developmental Stages of Common Carp

The aim of this study was to assess the impact of terbuthylazine in surface waters on fish under experimental conditions. Subchronic toxic effects on embryos and larvae of common carp (Cyprinus carpio) were investigated during a 30-day toxicity test. The exposure to terbuthylazin showed no effect on mortality, but significant differences (P < 0.0001) were revealed on weight and growth parameters at concentrations of 520 and 820 μg/L. The inhibition of specific growth rate at concentrations of 520 and 820 μg/L was 14% compared to the control group. No significant negative effects on total body length and body weight were observed at lower concentrations (0.9 and 160 μg/L). The concentrations 520 and 820 μg/L were associated with a delay in development compared to other experimental groups and controls. On the basis of weight and growth rate evaluation and determination of developmental stages, the No Observed Effect Concentration (NOEC) of terbuthylazine was estimated at 160 μg/L and the Lowest Observed Effect Concentration (LOEC) was 520 μg/L. According to these results, the reported environmental concentration of terbuthylazine in Czech rivers does not impact growth, development, morphology, or histology of carp embryos and larvae

Comparison of Terbutryn Acute Toxicity to Danio rerio and Poecilia reticulata

Abstract The aim of the present study was to determine and compare acute toxicity of terbutryn in Danio rerio and Poecilia reticulata, and in two different developmental stages of D. rerio -embryonic and juvenile. Acute toxicity tests were performed according to OECD methodology. The LC50 values were assessed by probit analysis using EKO-TOX 5.2 programme. The 96hLC50 terbutryn mean value of 5 tests was 2.85 ± 0

Evaluation of breast stiffness pathology based on breast compression during mammography: Proposal for novel breast stiffness scale classification

Breast cancer is diagnosed through a patient's Breast Self-Examination (BSE), Clinical Breast Examination (CBE), or para-clinical methods. False negativity of PCM in breast cancer diagnostics leads to a persisting problem associated with breast tumors diagnosed only in advanced stages. As the tumor volume/size at which it becomes invasive is not clear, BSE and CBE play an exceedingly important role in the early diagnosis of breast cancer. The quality and effectiveness of BSE and CBE depend on several factors, among which breast stiffness is the most important one. In this study, the authors present four methods for evaluating breast stiffness pathology during mammography examination based on the outputs obtained during the breast compression process, id est, without exposing the patient to X-Ray radiation. Based on the subjective assessment of breast stiffness by experienced medical examiners, a novel breast stiffness classification was designed, and the best method of its objective measurement was calibrated to fit the scale. Hence, this study provides an objective tool for the identification of patients who, being unable to perform valid BSE, could benefit from an increased frequency of mammography screening. Dum vivimus servimus. © 2022 HCFMUSPMinisterstvo Školství, Mládeže a Tělovýchovy, MŠMT: SP2021/66; Ostravská Univerzita v Ostrav

Evaluation of breast stiffness pathology based on breast compression during mammography: Proposal for novel breast stiffness scale classification

Breast cancer is diagnosed through a patient's Breast Self-Examination (BSE), Clinical Breast Examination (CBE), or para-clinical methods. False negativity of PCM in breast cancer diagnostics leads to a persisting problem associ-ated with breast tumors diagnosed only in advanced stages. As the tumor volume/size at which it becomes inva-sive is not clear, BSE and CBE play an exceedingly important role in the early diagnosis of breast cancer. The quality and effectiveness of BSE and CBE depend on several factors, among which breast stiffness is the most important one. In this study, the authors present four methods for evaluating breast stiffness pathology during mammography examination based on the outputs obtained during the breast compression process, id est, without exposing the patient to X-Ray radiation. Based on the subjective assessment of breast stiffness by experienced medical examiners, a novel breast stiffness classification was designed, and the best method of its objective mea-surement was calibrated to fit the scale. Hence, this study provides an objective tool for the identification of patients who, being unable to perform valid BSE, could benefit from an increased frequency of mammography screening. Dum vivimus servimus.Web of Science77art. no. 10010