17 research outputs found
Passiver Erddruck unter stoßartiger Belastung
No full textKnowing the passive earth resistance under shock-type loads is extremely important to assure that the ultimate and serviceability limit states are not exceeded in the case of accidental actions due to collision of vehicles with structures. Previous papers that provide a calculation model validated by tests are not known. The research started with the static passive earth resistance mobilization in order to develop and validate a mathematical model, which was later extended for the dynamic case, by adding the inertial forces. The model was transposed in a calculation program and was validated on small scale physical models.
The applicability of the model can be extended to any type of vertical plane structures, which are in contact with the retained soil, and for which a horizontal displacement is expected, and which can be assimilated by a plane strain state. As an alternative, the physical tests were also analyzed by the finite element method, using the PLAXIS 2D software. The results obtained for the dynamic case offer a safe approximation and they are presented within the paper.
Finally, several selected practical examples of applying the mathematical model developed by the author are presented. The examples consist of passive earth pressure calculations, in case several common transportation vehicles collide with retaining walls. Furthermore, a simplified preliminary analysis is recommended as exemplified in chapter 6.8, in order to identify the design cases in which the dynamic response may lead to the system’s loss of stability.
As a main result of the research, for practical cases the design engineer may use the values of the ultimate static passive displacement and resistance given by any standard, literature reference or model as input in the mathematical model developed by the author in order to calculate the horizontal parallel displacement of a planar full-scale structure subjected to any shock-type load. For a simplified preliminary approach, the use of the charts represented in the figures 6-24 and 6-25 is recommended. For more complex cases or need for accurate results in special cases, further research is required as outlined in the proposed development possibilities.Die Kenntnis des passiven Erddruckes unter Stoßbelastungen ist äußerst wichtig, um sicherzustellen, dass die Grenzzustände der Standsicherheit und Gebrauchstauglichkeit bei außergewöhnlichen Einwirkungen aufgrund einer Kollision von Fahrzeugen mit Bauwerken nicht überschritten werden. Frühere Arbeiten, die ein durch Versuche validiertes Berechnungsmodell bereitstellen, sind dem Autor nicht bekannt.
Die Forschung begann mit der statischen Mobilisierung des passiven Erdwiderstands, um ein mathematisches Modell zu entwickeln und zu validieren, das später für den dynamischen Fall durch Hinzufügen der Trägheitskräfte erweitert wurde. Das Modell wurde in ein Berechnungsprogramm umgesetzt und anhand von kleinen Modellversuchen validiert. Die Anwendbarkeit des Modells kann auf jede Art von vertikalen ebenen Tragwerken ausgedehnt werden, die mit dem gestützten Boden in Kontakt stehen und für die eine horizontale Verschiebung erwartet wird und die durch einen ebenen Verformungszustand assimiliert werden können. Alternativ wurden die physikalischen Tests auch mit der Finite-Elemente-Methode unter Verwendung der PLAXIS 2D-Software analysiert. Die für den dynamischen Fall erhaltenen Ergebnisse bieten eine sichere Annäherung und werden in der Arbeit dargestellt.
Abschließend werden einige ausgewählte praktische Beispiele für die Anwendung des vom Autor entwickelten mathematischen Modells dargestellt. Die Beispiele bestehen aus passiven Erddruckberechnungen für den Fall, dass mehrere gängige Transportfahrzeuge mit Stützmauern kollidieren.
Darüber hinaus wird eine vereinfachte Analyse empfohlen, wie im Kapitel 6.8 veranschaulicht, um die Entwurfsfälle zu identifizieren, in denen das dynamische Verhalten zum Verlust der Standsicherheit des Systems führen kann. Als Hauptergebnis der Forschung kann der Planungsingenieur für praktische Fälle die Werte der statischen passiven Grenzverschiebung und des Erdwiderstands verwenden, die in Normen, Regelwerken, Literatur oder einem Modell als Eingabe in das vom Autor entwickelte mathematische Modell angegeben werden, um die horizontale parallele Verschiebung eines ebenen Tragwerks zu berechnen, die einer Stoßbelastung ausgesetzt ist. Für einen vereinfachten praktischen Ansatz wird die Verwendung der in den Abbildungen 6-24 und 6-25 dargestellten Diagramme empfohlen. Für komplexere Fälle oder die Notwendigkeit genauer Ergebnisse in besonderen Fällen sind weitere Untersuchungen erforderlich, wie in den vorgeschlagenen Entwicklungsmöglichkeiten dargelegt
Pre-operative planning for reverse shoulder arthroplasty in low-resource centres : a modified Delphi study in South Africa
No full textDATA AVAILABILITY STATEMENT :
The datasets used and analyzed during the current study are avail-
able from the corresponding author on reasonable request.BACKGROUND : Pre-operative planning for reverse shoulder arthroplasty (RSA) poses challenges, particularly when dealing with glenoid bone loss. This modified Delphi study aimed to assess expert consensus on RSA planning processes and rationale, specifically targeting low-resourced institutions. Our objective was to offer pre-operative decision-making algorithms tailored for surgeons practising in resource-constrained hospitals with limited access to computed tomography (CT) scans. METHODS : A working group generated statements on pre-operative imaging and glenoid of glenoid morphology and intra-operative decision-making. The study was conducted in three stages, with virtual consensus meetings in between. Stages 2 and 3 consisted only of closed questions/statements. The statements with over 70% were considered consensus achieved and those with less than 10% were considered disagreement consensus achieved. RESULTS : Twelve shoulder surgeons participated, with 67% having over five years of experience in shoulder arthroplasty. In the absence of glenoid bone loss, the sole use of plain radiographs for pre-operative planning reached consensus and is recommended by these groups, while 100% advise using CT scans when bone loss is present. Most surgeons (70%) recommend using patient-specific instrumentation (PSI) in cases of structural bone loss. Most of the statements on intra-operative decision-making related to component placement and enhancing stability failed to reach consensus. CONCLUSION : While consensus was achieved on most aspects of pre-operative imaging and planning, technical aspects of surgery lacked consensus. Planning for patients with structural glenoid bone loss necessitates CT scans and planning tools.http://www.sicot-j.orghj2024Orthopaedic SurgerySDG-03:Good heatlh and well-bein
A narrative review of treatment strategies for major glenoid defects during primary reverse shoulder arthroplasty, with a focus on the use of structural bone graft
No full textStructural glenoid defects are common during primary reverse shoulder arthroplasty (RSA) and are often associated with poor outcomes.
The lack of pre-operative imaging protocols for determining the depth and degree of glenoid wear hinders our ability to accurately plan and correct these defects.
Although bone grafting has been reported to be effective in reducing glenoid wear during RSA, there is limited information on when to utilise it and how to prepare the graft.
We conducted this review to assess the evidence for the management of glenoid defects, with an emphasis on bone grafts to treat structural glenoid bone loss in primary RSA patients
Distal Biceps Tendinopathy: Conservative Treatment
No full textBackground Non-traumatic distal biceps tendinopathy related to overuse, has not been previously reported in the literature. We describe the symptoms and signs, a novel injection technique onto the bicipital tuberosity of the radius and outcomes of this treatment. Materials and Methods We retrospectively reviewed the clinical notes of 20 patients (24 elbows), in whom the diagnosis of distal biceps tendinopathy was made. Twenty-two of 24 elbows were treated with one or more cortisone injections. The patients were followed up via a telephonic questionnaire. Results Average duration of follow-up was 3 years and 4 months. Eighteen elbows returned to full function. Five elbows (four patients) had partial resolution of symptoms, and one had no relief. In these six elbows, symptoms had been ongoing for ≥ 8 months prior to injection. Conclusion Distal biceps tendinopathy is often misdiagnosed. The majority of cases respond well to steroid injections without the risk of rupture or neurological injury. Resolution of pain with restoration to previous function is more likely when symptoms have been present for less than 8 months. </jats:sec
Factors that determine the unusually low reduction potential of cytochrome c550 in cyanobacterial photosystem II
No full textA study of a protein that shuttles electrons during plant photosynthesis. The electrons are eventually taken away from water and in the process, oxygen is produced. --author-supplied descriptio
High-frequency EPR study of a new mononuclear manganese(III) complex: [(terpy)Mn(N3)3] (terpy = 2,2\u27:6\u27,2\u27\u27-Terpyridine)
No full textA study of another mimic of the enzyme that is responsible for the evolution of oxygen gas during photosynthesis. This paper concentrates on the structure of the molecule. --author-supplied descriptio
Pre-operative planning for reverse shoulder arthroplasty in low-resource centres: A modified Delphi study in South Africa
No full textBackground: Pre-operative planning for reverse shoulder arthroplasty (RSA) poses challenges, particularly when dealing with glenoid bone loss. This modified Delphi study aimed to assess expert consensus on RSA planning processes and rationale, specifically targeting low-resourced institutions. Our objective was to offer pre-operative decision-making algorithms tailored for surgeons practising in resource-constrained hospitals with limited access to computed tomography (CT) scans. Methods: A working group generated statements on pre-operative imaging and glenoid of glenoid morphology and intra-operative decision-making. The study was conducted in three stages, with virtual consensus meetings in between. Stages 2 and 3 consisted only of closed questions/statements. The statements with over 70% were considered consensus achieved and those with less than 10% were considered disagreement consensus achieved. Results: Twelve shoulder surgeons participated, with 67% having over five years of experience in shoulder arthroplasty. In the absence of glenoid bone loss, the sole use of plain radiographs for pre-operative planning reached consensus and is recommended by these groups, while 100% advise using CT scans when bone loss is present. Most surgeons (70%) recommend using patient-specific instrumentation (PSI) in cases of structural bone loss. Most of the statements on intra-operative decision-making related to component placement and enhancing stability failed to reach consensus. Conclusion: While consensus was achieved on most aspects of pre-operative imaging and planning, technical aspects of surgery lacked consensus. Planning for patients with structural glenoid bone loss necessitates CT scans and planning tools
Characterization of the O2-Evolving reaction catalyzed by [(terpy)(H2O)MnIII(O)2MnIV(OH2)(terpy)](NO3)3 (terpy = 2,2\u27:6,2\u27\u27-Terpyridine)
No full textA study of a mimic of the enzyme that is responsible for the evolution of oxygen gas during photosynthesis. The mimic does indeed make oxygen from water and in this paper we describe the details of the reaction through a variety of means. (author-supplied description
