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Ultimate Load Capacity Of Optimally Designed Cellular BeamsErdal, Ferhat 01 February 2011 (has links) (PDF)
Cellular beams became increasingly popular as an efficient structural form in
steel construction since their introduction. Their sophisticated design and
profiling process provides greater flexibility in beam proportioning for
strength, depth, size and location of circular holes. The purpose of
manufacturing these beams is to increase overall beam depth, the moment of
inertia and section modulus, which results in greater strength and rigidity.
Cellular beams are used as primary or secondary floor beams in order to
achieve long spans and service integration. They are also used as roof beams
beyond the range of portal-frame construction, and are the perfect solution for
curved roof applications, combining weight savings with a low-cost
manufacturing process.
The purpose of the current research is to study optimum design, ultimate load
capacity under applied load and finite element analysis of non-composite
cellular beams. The first part of the research program focuses on the optimum
design of steel cellular beams using one of the stochastic search methods called
&ldquo / harmony search algorithm&rdquo / . The minimum weight is taken as the design
objective while the design constraints are implemented from the Steel
Construction Institute. Design constraints include the displacement limitations,
overall beam flexural capacity, beam shear capacity, overall beam buckling
strength, web post flexure and buckling, vierendeel bending of upper and lower
tees and local buckling of compression flange. The design methods adopted in
this publication are consistent with BS5950. In the second part of the research,
which is the experimental work, twelve non-composite cellular beams are
tested to determine the ultimate load carrying capacities of these beams under
using a hydraulic plug to apply point load. The tested cellular beam specimens
have been designed by using harmony search algorithm. Finally, finite element
analysis program is used to perform elastic buckling analysis and predict
critical loads of all steel cellular beams. Finite element analysis results are then
compared with experimental test results for each tested cellular beam.
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Safety Management Systems (SMS) for aircraft manufacturers and maintainers?Gibbons, Blake January 2014 (has links)
There is much dialogue in the global aviation industry about Safety Management Systems (SMS) and how it should be integrated across all domains of the industry including aircraft design, production, flight operations, overhaul and maintenance, suppliers, service providers, airports, and so forth (Johnson, 2012).
Regulators have made significant progress in recent years to implement ICAO’s SMS into airlines, albeit as a required or recommended practice. More recently the regulators are seeking to implement SMS into the aircraft manufacturing and aircraft maintenance domains.
This research reviewed regulatory publications from multiple countries to assess the technical makeup of SMS, and understand what regulators are requiring, or recommending, and when. It was found that global regulators accept the ICAO published definition of SMS, but different regulators have varying approaches regarding implementation. However, they are consistent in initially targeting airlines for SMS implementation. SMS comments range from “The best thing since sliced bread” to “Worst thing since the creation of the FAA; I don’t need anyone telling me what’s safe when I already know it; waste of time and money”.
This investigation experimented with field tests to connect the engineering, production and airline domains into one ICAO SMS model. Results indicate that because the different domains are risk-specific, the application of one safety risk management model to all domains is not viable. The SMS model applies to airlines because airlines’ primary risk is about operational safety. Aircraft production and maintenance is about production risk – therefore the risk model must be centric to process risk. Field test 3 tailored the ICAO SMS risk architecture to assess and mitigate process risk as applicable to the aircraft manufacturing and maintenance. Although the SMS architecture was usable, the content and focus was significantly adjusted to be production process-risk centric, to the point where the term “SMS’ was deemed out of place. The resulting model was therefore named Production Risk Management System (PRMS).
Following the emergence of PRMS from field tests, this investigation reviewed industry, research and regulatory arguments for and against SMS in the airline industry, and correlated those arguments with the benefits and non-benefits of PRMS for the manufacturing and aircraft maintenance domains.
The researcher advocates PRMS as a viable model that meets ICAO SMS-like architecture for aircraft production and maintenance. Methods were identified for developing and implementing PRMS, and for evaluating its ROI. If and when “SMS” is truly mandated in these domains, the researcher proposes PRMS as a viable model that should be considered. Furthermore, the researcher proposes that PRMS can be an effective production risk management system that can enhance the organization’s existing QMS, regardless of “SMS” regulations.
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Performance evaluation of RC flexural elements strengthened by advanced compositesAndreou, Eftychia January 2002 (has links)
The flexural performance of composite systems made of reinforced concrete, Fibre Reinforced Polymers (FRPs) and adhesives was studied during the current research. The experimental investigation was principally concentrated on the potential use of Kevlar® 49 (aramid fibre) for RC beam strengthening. The main aims of research have been; (a) to investigate the relative merits of using Aramids in comparison to other FRPs, (b) strength optimisation of systems to prevent excessive losses of ductility, (c) to examine the failure mode and crack patterns, together with salient strength factors at ultimate limit state and (d) to carry out analytical modelling using a commercial FE package. The experimental investigation comprised of testing 55 simply supported RC beams of either 1.5m or 2.6m length. In addition to the parametric studies included in points (a)-(d) above (to assess the section characteristics), further experimentation was conducted to investigate the beam performance by varying the factors of; (e) beam shear span, (f) FRP anchorage length, (g) concrete surface preparation, (h) FRP end-anchoring, (i) beam precracking, (j) introduction of air-voids within the bond line of FRP/concrete, (k) influence of cyclic loading and, (1) exposure to aggressive environment. The results from current tests confirm elements of reports from other researchers (by thorough review of literature) that all FRPs have great potential for flexural strengthening of RC members. This is valid even in cases where additional environmental degradation and/or cracking (due to serviceability loads), had taken place. Aramid fibres were found to result in favourable outcomes concerning both strength and ductility enhancements. It was determined, both from experiments and non-linear modelling, that the amount of FRP fibre content is an important factor in every strengthening application. Experimentation showed that depending on the existing condition of the structure (concrete strength, internal reinforcement ratio, section dimensions, degradation level and load configuration), there seems to be a unique level of optimum fibre content. The FRP levels in excess of the optimum were seen to lead to premature brittle tearing-off failure modes. It was also found that to prevent premature beam failure (due to incompatibility of stress at concrete and FRP interface), a maximum possible anchorage length should be considered in order to deliver an optimum section performance. The results from the analytical modelling indicated a most satisfactory agreement with the experimental data after the initial mechanical properties were calibrated. It was found that actual representation of material properties (e.g. steel constitutive law) are of great significance, for an accurate modelling of RC element loaded behaviour. The bond developed between the FRP and concrete is one of the key parameters for achieving good performance of the systems. It was determined that concrete surface preparation and priming is beneficial, while the introduction of air-voids due to poor workmanship can reduce the section load bearing capabilities. Cyclic loading on FRP strengthened sections was found to curtail the full rotational capacity utilisation of the beam. However, even the above mentioned curtailed behaviour was more advantageous than cyclically loaded beam performance without FRP strengthening.
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Modélisation d’essais de choc sur dispositifs de retenue de véhicules : Application aux dispositifs mixtes acier-bois / Vehicle restraint system crash test modelling : Application to steel-wood structuresGoubel, Clément 13 December 2012 (has links)
En France, un tiers des personnes tuées sur la route le sont lors d’un accident sur un obstaclefixe. Dans 90% des cas, ces accidents surviennent après une perte de contrôle du véhicule.Les dispositifs de retenue de véhicule ont pour but de maintenir les véhicules en perdition surla chaussée en limitant la sévérité de l’impact.Ces dispositifs doivent subir des essais de chocs normatifs afin de pouvoir être installés sur lebord des routes européennes et d’évaluer leurs performances en termes de sévérité et dedéflexion.Les tolérances existantes sur les paramètres d’essai (véhicule, masse du véhicule, vitesse,angle et point d’impact …) et les incertitudes sur les caractéristiques mécaniques desmatériaux constituant le dispositif ont un effet sur les performances de ce dispositifs etdoivent être prises en compte lors des calculsLes dispositifs mixtes (acier-bois) présentent une difficulté supplémentaire en raison del’hétérogénéité du matériau et de sa sensibilité aux variables d’environnement telles que latempérature et l’humidité.Afin de prendre en compte cette variabilité et d’évaluer son impact sur les performances d’undispositif, des essais dynamiques sur des échantillons de structure ont été réalisés et modélisésnumériquement.Enfin, un modèle complet d’un dispositif de retenue de véhicule a été effectué et corrélé surun essai de choc réel à l’aide d’une méthode prenant en compte la variation de paramètresphysiques liés à l’apparition des modes de ruine de la structure. Une fois corrélé, le modèle aété utilisé afin d’évaluer l’incidence de la modification des caractéristiques mécaniques dubois liée aux variations des conditions environnementales. / In France, one third of the people dying on the roads are killed after impacting against ahazard. In 90% of the reported cases, these accidents result from loss of control. VehicleRestraint Systems (VRS) are specially designed to restrain an errant vehicle and to limitimpact severity.Before being installed on the roadsides, these devices have to be crash-tested according tostandards in order to evaluate their safety and deflexion performances.Tolerances exist on impact parameters (vehicle, vehicle mass, impact speed, impact angle,impact point …) and material’s mechanical characteristic uncertainties have an effect towardsdevice performances and have to be taken into account during numerical simulations.Steel-wood structures present an additional numerical challenge due to wood heterogeneityand its sensibility to environment variables such as temperature and moisture content.In order to assess the effect of this variability toward safety performances, three point bendingdynamic experiments on structural samples are performed and modelled.Finally, a complete model of a vehicle restraint system is built and validated according to realcrash test results thanks to a parametric method. This method takes into account the variabilityof the parameters associated to the failure modes of the structure. Once validated the model isused to assess the effect of wood mechanical properties modifications due to environmentvariable variations.
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Progressive failure analyses of concrete buttress dams : Influence of crack propagation on the structural dam safety / Analys av brottförlopp hos betonglamelldammar : Inverkan av sprickpropagering på dammsäkerhetenFu, Chaoran, Hafliðason, Bjartmar January 2015 (has links)
Concrete buttress dams are the most common type of concrete dams for hydropower production in Sweden. Cracks have been observed in some of the them. However, only limited research has been made concerning the influence of these cracks on the structural dam safety. In conventional analytical stability calculations, a concrete dam is assumed to be a rigid body when its safety is verified. However, when cracks have been identified in a dam structure, the stability may be influenced and hence the information of cracks may need to be included in the stability calculations. The main aim of this project is to study how existing cracks and further propagation of these cracks, influence the structural dam safety. Another important topic was to study suitable methods to analyse a concrete dam to failure. In addition, a case study is performed in order to capture the real failure mode of a concrete buttress dam. The case study that has been studied is based on a previous project presented by Malm and Ansell (2011), where existing cracks were identified in a 40m high monolith, as a result from seasonal temperature variations. Two similar models are analysed where one model is defined with an irregular rock-concrete interface, and the other with a horizontal interface. Analyses have been performed on both an uncracked concrete dam but also for the case where information regarding existing cracks, from the previous project, have been included in order to evaluate the influence of cracks on the dam safety. The finite element method has been used as the main analysis tool, through the use of the commercially available software package Abaqus. The finite element models included nonlinear material behaviour and a loading approach for successively increasing forces called overloading, when performing progressive failure analyses. The results show that existing cracks and propagation of these resulted, in this case, in an increased structural safety of the studied dam. Furthermore, an internal failure mode is captured. The irregular rock-concrete interface has a favourable effect on a sliding failure and an unfavourable effect on an overturning failure, compared to the case with the horizontal interface. Based on the results, the structural safety and the failure mode of concrete buttress dams are influenced by existing cracks. Although an increased safety is obtained in this study, the results do not necessarily apply for other monoliths of similar type. It is thus important that existing cracks are considered in stability analyses of concrete buttress dams. / Lamelldammar är den vanligaste typen av betongdammar för vattenkraft produktion i Sverige. I vissa av dessa har sprickbildning observerats. Begränsad forskning har gjorts på hur dessa sprickor påverkar dammens säkerhet. I de vedertagna analytiska stabilitetsberäkningarna antas att betongdammar agerar som en stel kropp när man verifierar dess säkerhet. Befintliga sprickor i en damm kropp kan dock påverka dess stabilitet och kan därför behöva beaktas i stabilitetsberäkningarna. Huvudsyftet med detta projekt är att studera hur befintliga sprickor och dess propageringen påverkar dammsäkerheten. Ett annat viktigt syfte är att studera lämpliga metoder för att analysera en betongdamm till brott. Dessutom, genomförs en fallstudie i syfte att analysera ett verkligt brottförlopp av en lamelldamm. Fallstudien som utförs i detta projekt, baseras på ett tidigare projekt utfört av Malm and Ansell (2011), där befintliga sprickor identifierades i en monolit på 40m som ett resultat av temperaturvariationer. Två modeller med snarlik geometri har analyserats, där den ena är definierad med en med oregelbunden kontaktyta mellan berg och betong och den andra med en horisontell kontaktyta. Analyserna har utförts på dels en osprucken damm men även där information om befintliga sprickor från det tidigare projektet beaktas, i syfte att jämföra inverkan av sprickor på dammsäkerheten. Finita element metoden har använts som verktyg vid dessa analyser, genom det kommersiellt använda programmet Abaqus. De finita element modellerna inkluderar icke-linjära material egenskaper hos betong och armering samt baseras på en metod för successiv belastning, som kallas 'overloading', vid analys av brottförloppet. Resultatet visar att befintliga sprickor och propageringen av dessa i detta fall kan leda till ökad säkerhet hos den studerade dammen jämfört mot fallet utan beaktande av sprickbildning. Utöver detta fångas även ett inre brottmod. Den oregelbundna kontaktytan mellan betongen och berget har en gynnsam effekt vid ett glidbrott men en ogynnsam inverkan vid ett stjälpningsbrott, i jämförelse med fallet med en horisontell kontaktyta. Baserat på dessa resultat så påverkas dammens säkerhet och brottetförloppet hos lamelldammen utav befintliga sprickor. Även om en ökad säkerhet fås i denna studie är det inte säkert att detta stämmer för andra monoliter av samma slag. Dock är det viktigt att hänsyn tas till befintliga sprickor i stabilitets analyser av lamelldammar.
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Applying System-Theoretic Accident Model and Processes (STAMP) to Hazard AnalysisSong, Yao 04 1900 (has links)
<p>Although traditional hazard analysis techniques, such as failure modes and effect analysis (FMEA), and fault tree analysis (FTA) have been used for a long time, they are not well-suited to handling modern systems with complex software, human-machine interactions, and decision-making procedures. This is mainly because traditional hazard analysis techniques rely on a direct cause-effect chain and have no unified guidance to lead the hazard analysis. The Systems Theoretic Accident Model and Process (STAMP) is based on systems theory to try to find out as much as possible about the factors involved in a hazard, and with providing clear guidance as to the control structure leading to the hazard.</p> <p>The Darlington Nuclear Power Generating Station was the first nuclear plant in the world in which the safety shutdown systems are computer controlled. Although FTA and FMEA have already been applied to these shutdown systems, Ontario power generation felt that it is still useful to try recent advances to evaluate whether they can improve on the previous hazard analysis.</p> <p>This thesis introduces the two most common traditional techniques of hazard analysis, FTA and FMEA, as well as two systemic techniques, STPA (which is a hazard analysis method associated with STAMP), and the Functional Resonance Accident Model (FRAM). The thesis also explains why we chose STPA to apply to the Darlington Shutdown System case, and provides an example of the application as well as an evaluation of its use compared with FMEA and FTA.</p> / Master of Applied Science (MASc)
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Podnikatelský záměr pro založení firmy / Business Plan for Establishment of the CompanyKoukal, David January 2016 (has links)
This thesis defines the theoretical basis essential for building a business plan and simultaneously encompasses the building of a real business plan, which will be focused on the creation of a new company - KK-TECH s.r.o., which will offer complex cleaning services. The key aspect of the thesis is market analysis, which the company will enter, and a marketing and financial plan. I will use primarily data, which have been obtained while studying, and also data, which have been obtained thanks to working in said field.
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A Holistic Framework for Analyzing the Reliability of IoT DevicesManca, Leonardo January 2023 (has links)
In the rapidly evolving landscape of the Internet of Things (IoT), ensuring consistency and reliability becomes a top priority for a seamless user experience. In many instances, reliability is assessed through Quality of Service (QoS) metrics, sidelining traditional reliability metrics that thrive on time-dependent failure rates. The lack of a comprehensive framework that fully integrates all layers of an IoT system adds to the complexity. This gap makes it difficult to pinpoint specific areas that need improvement and to conduct a thorough assessment of the system’s reliability. This project addresses this intricate challenge, which holds significant relevance for industry professionals but remains unresolved. The project introduced an IoT architecture spanning the Power, Device, Edge, Application, and Cloud Layers. Within each layer, potential failure points were identified, and the reliability was analysed deploying time-based failure rates with an exponential distribution. Reliability Block Diagrams (RBDs) were employed to map the intricate inter-dependencies, though the framework’s adaptive nature allows for other system reliability methodologies. One of the primary outcomes of this research is the development of a new framework tailored for evaluating the reliability of various IoT system components. This framework yields insights into both system reliability and availability over time, serving as a pivotal tool for stakeholders such as device manufacturers, system integrators, network providers, and research institutions. The results show how the framework emerges as a pivotal starting point for IoT system reliability evaluation. Before this thesis, the feasibility of such a framework was uncertain, with concerns about its potential bias – being either too pessimistic or optimistic. Yet, the tangible results from this work affirm its capability to provide a balanced and reasonable reliability estimation, given the intricacies of IoT devices. This paves the way for subsequent research, enabling a deeper dive into targeted enhancements and fostering a nuanced understanding of IoT reliability. / I det snabbt föränderliga IoT-landskapet (Internet of Things) är det av högsta prioritet att säkerställa konsekvens och tillförlitlighet för en sömlös användarupplevelse. I många fall bedöms tillförlitligheten med hjälp av QoSmått (Quality of Service), vilket innebär att traditionella tillförlitlighetsmått som bygger på tidsberoende felfrekvenser åsidosätts. Avsaknaden av ett heltäckande ramverk som integrerar alla lager i ett IoT-system bidrar till komplexiteten. Denna brist gör det svårt att identifiera specifika områden som behöver förbättras och att göra en grundlig bedömning av systemets tillförlitlighet. Detta projekt tar itu med denna komplicerade utmaning, som har stor relevans för branschfolk men som fortfarande inte har lösts. Projektet introducerade en IoT-arkitektur som spänner över kraft-, enhets-, Edge-, applikationsoch molnlagren. Inom varje lager identifierades potentiella felpunkter och tillförlitligheten analyserades med hjälp av tidsbaserade felfrekvenser med en exponentiell fördelning. Tillförlitlighetsblockdiagram (RBD) användes för att kartlägga de komplicerade ömsesidiga beroendena, även om ramverkets adaptiva natur möjliggör andra metoder för systemtillförlitlighet. Ett av de främsta resultaten av denna forskning är utvecklingen av ett nytt ramverk som är skräddarsytt för att utvärdera tillförlitligheten hos olika IoT-systemkomponenter. Detta ramverk ger insikter om både systemets tillförlitlighet och tillgänglighet över tid, och fungerar som ett viktigt verktyg för intressenter som tillverkare av enheter, systemintegratörer, nätverksleverantörer och forskningsinstitutioner. Resultaten visar hur ramverket framstår som en viktig utgångspunkt för utvärdering av IoT-systemens tillförlitlighet. Före den här avhandlingen var det osäkert om ett sådant ramverk var genomförbart, med farhågor om dess potentiella partiskhet - att vara antingen för pessimistisk eller optimistisk. De konkreta resultaten från detta arbete bekräftar dock ramverkets förmåga att ge en balanserad och rimlig uppskattning av tillförlitligheten, med tanke på IoT-enheternas komplexitet. Detta banar väg för efterföljande forskning, vilket möjliggör en djupare analys av riktade förbättringar och främjar en nyanserad förståelse av IoT-tillförlitlighet.
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Quality Assuring of Stator Winding Production : Using electrical tests to quality assure the process steps of a series stator winding productionSayed Hamad, Tarek January 2021 (has links)
The demands for sustainable transportation have made battery electric vehicles an increasingly popular subject in the world of both businesses and engineering. This thesis has been made in collaboration with Scania, which is currently investigating the possibility of manufacturing stators and rotors in-house in a series production line. For Scania, the topic of quality assurance is of great importance as Scania wants to ensure their trucks and buses fulfil the quality requirements of both customers and society. The goal of the thesis is to provide Scania with a set of guidelines for what quality assurance steps to perform in a series stator winding production, and where in the production they should be placed. The investigated stator winding type is a continuous hairpin winding, and the investigated quality assurance steps are solely electrical tests used to ensure the safety, functionality, and quality of the stator windings. A process-failure modes and effects analysis were conducted to identify the risks associated with each production step. The results indicates where the quality assurance steps should be taken. Further analysis, based on the provided background of electrical tests, also provides an answer to what electrical tests to perform as quality assurance steps. The result of the thesis is a concept, presented in a flow chart diagram, which indicates what electrical tests to perform and where the tests should be performed in the stator winding production chain. / De krav som sätts på hållbar transport har gjort batteridrivna elektriska fordon ett alltmer populärt ämne i världens företag och ingenjörskonst. Denna avhandling har gjort i samarbete med Scania, som i nuläget utreder möjligheterna för att tillverka statorer och rotorer in- house i en serie produktionslinje. För Scania är ämnet kvalitetssäkring (QA) ett viktigt ämne, för att Scania vill säkerställa att deras lastbilar och bussar lever upp till de kvalitetskrav som både kunder och samhället ger. Avhandlingens mål är därför att förse Scania med en uppsättning av riktlinjer för vilka QA steg som ska utföras i en serie statorlindningsproduktion, och var i produktionen de ska placeras. Den statorlindningstypen i fokus är en kontinuerlig hårnålslindning, och att de kvalitetssäkringar som undersöks är enbart elektriska test som säkrar säkerhet, funktionalitet samt kvalitén av statorlindningarna. En P-FMEA har utförts som en risk och felläges analys i syfte att identifiera de risker som är associerat med varje produktionssteg. Resultatet pekar på var QA steg ska utföras någonstans. Fortsatt analys, baserat på den givna bakgrunden av elektriska test, ger även ett svar på vilka elektriska test som ska utföras som QA steg. Avhandlingens resultat är ett koncept, presenterat i ett flödesdiagram, som visar vilka elektriska test som ska utföras samt var dessa tests ska utföras i statorlindningsproduktionen.
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