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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

LEFM based analysis of the effect of tensile residual macrostress on fatigue crack propagation

Prawoto, Yunan, January 2000 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 182-188). Also available on the Internet.
12

Vertical extension to the Hong Kong Polytechnic University /

Chong, Chi-leung, Richard. January 1997 (has links)
Thesis (M. Arch.)--University of Hong Kong, 1997. / Includes special study report entitled: Light-weight structures and construction methodology for vertical extension. Includes bibliographical references.
13

Multikriterielle Simulation und Optimierung im Leichtbau

Kroll, Lothar, Ulke-Winter, Lars 10 July 2015 (has links) (PDF)
Das Hauptanliegen des Bundesexellenzclusters MERGE: Technologiefusion für multifunktionale Leichtbaustrukturen ist die Verwendung von prozesstauglichen Technologien zur resourceneffizienten Herstellung von Leichtbaustrukturen in Mischbauweise. In der Interactive Domain (IRD): Modelling, Integrative Simulation and Optimization des Cluster of Excellence „MERGE“ werden ganzheitliche und durchgängige Simulationsketten entwickelt, um das Werkstoffverhalten von unterschiedlichen Materialgruppen unter Berücksichtigung prozessbedingter und belastungsspezifischer Restriktionen aufeinander abzustimmen. Die Bauteileigenschaften und Randbedingungen bei der Herstellung der Hybridbauteile hängen dabei, neben den verwendeten Materialkombinationen (Kunststoffe, Faserverbunde, Metalle), in starkem Maße von den zugrundeliegenden Fertigungsprozessen ab. Insbesondere die multikriterielle Optimierung -- von der Herstellung bis zum belasteten Bauteil -- benötigt eine Vielzahl an aufwändigen Simulationen die ein effizientes Datenmanagement sowie verteilten Berechnungsumgebungen erfordern. / The main objective of the Cluster of Excellence “MERGE”: Merge Technologies for Multifunctional Lightweight Structures is the use of process technologies suitable for resource-efficient production of lightweight structures in composite design. In the Interactive Research Domain (IRD): Modelling, Simulation and Optimization of Cluster of Excellence "MERGE" holistic and integrated simulation chains are designed to match the material behavior of different groups of materials under consideration of process-related and load specific restrictions. The component properties and constraints in the production of hybrid components depend in addition to the used material combinations (fiber reinforced plastics and metals) largely on the underlying production process. In particular, the multicriteria optimization - from manufacturing process until the loaded lightweight structure -- requires a large number of complex simulations which require an efficient data management and distributed computing environments.
14

Vertical extension to the Hong Kong Polytechnic University

Chong, Chi-leung, Richard. January 1997 (has links)
Thesis (M.Arch.)--University of Hong Kong, 1997. / Includes special study report entitled : Light-weight structures and construction methodology for vertical extension. Includes bibliographical references. Also available in print.
15

LEFM based analysis of the effect of tensile residual macrostress on fatigue crack propagation /

Prawoto, Yunan, January 2000 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 182-188). Also available on the Internet.
16

Problematiska områden vid vertikal förtätning - och hur de kan avhjälpas med hjälp av lättbyggnadselement / Problematic areas of vertical densification - and which of these areas can be remedied using lightweight elements

Wiborg, Theres, Sundén, Malin January 2018 (has links)
För att få plats med alla nya bostäder behöver städer växa. Många städer har ökat i area vilkethar lett till att grönmark försvunnit och att behovet av transporter ökat. Ett annat sätt att lösastädernas tillväxt är att förtäta dessa. Förtätning innebär att den mark som redan är bebyggdexploateras ytterligare. Detta kan göras på flera olika vis. Befintliga byggnader kan rivas föratt ge plats åt bättre planerade, eller högre byggnader. Befintliga byggnader kan byggas tilleller byggas på. Ett annat sätt att förtäta är att ändra användandet av gamla byggnader frånexempelvis lagerlokaler till bostäder, eller riva hela områden av gamla byggnader för attåteruppbygga dessa med tätare och högre bebyggelse.Detta examensarbetet fokuseras på vertikala förtätningen som innebär att stadens befintligasilhuett förhöjs. Befintliga byggnader byggs på på höjden, källare och vindar inreds tillbostäder eller befintliga byggnader rivs och ersätts med nya högre byggnader. Precis som vidall typ av förtätning uppkommer vissa problem vid vertikal förtätning. Syftet med dennarapport är att definiera problemen vid vertikal förtätning samt hur dessa problem undviksgenom att använda lättbyggnadselement.Dagsljuskraven som finns i BBR styr när nya byggnader skall projekteras. En viss tillgång tilldagsljus skall finnas i alla rum där man vistas mer än tillfälligt. När nya högre byggnaderuppförs ändras tillgången på dagsljus för intilliggande byggnader och områden vilket kan blimycket problematiskt då det inte finns regelverk som styr detta.Vidare innebär högre hus att ljudet från staden kommer studsa och spridas annorlunda äninnan. Flera människor och funktioner på samma ställe, vilket blir en naturlig förlängning aven förtätning, gör också att bullernivåerna ökar.Vertikal förtätning av städerna medför nya utmaningar även vad gäller brandskyddet. När husbyggs på inryms inte bara fler människor utan ibland även nya verksamheter, vilket leder tillatt nya krav rörande brandsäkerheten måste tillgodoses. Att bygga på nya våningar på redanbefintliga byggnader ger större brandtekniska utmaningar än om ett nytt hus byggs på marken.De fastigheter som skall byggas på uppfördes ofta när andra brandkrav gällde, varför ävendessa måste anpassas för att möta de nya brandskyddskraven.Även tillgängligheten i byggnader är en viktig aspekt att ha i beaktning när påbyggnationerskall göras. Om en byggnad överstiger tre våningar krävs att hiss finns för att rullstolsburnaskall ha tillgång till byggnaden. Dessa regler gäller både vid uppförande av nya byggnader,likväl som vid ändring av befintliga byggnader. De nya våningsplanen måste uppfyllasamtliga krav som ställs i BBR avseende tillgänglighet.Ett problem som blir uppenbart när ytterligare våningar ska byggas ovanpå redan befintligahus är hur den befintliga byggnaden skall klara att bära upp de nya våningarna. Därför måstealltid en rigorös utredning av detta göras innan en påbyggnad påbörjas. För att minskabelastningen på befintlig byggnation kan påbyggnad göras med hjälp av lättbyggnadselement.Rörande de olika problemområden som framkommit kan ses att det egentligen endast är ihänseendet statik de olika påbyggnadsmetoderna skiljer sig nämnvärt åt. I de flesta områdenses ingen större skillnad alls. / In order to accommodate all new homes, cities need to grow. Many cities have increased inarea, which has led to the disappearance of parks and fields and increased the need fortransport. Another way to solve urban growth is to densify them. Densifying means that theland already built is further exploited. This can be done in several different ways. Existingbuildings can be demolished to accommodate better planned or higher buildings. Existingbuildings can be increased in both horizontal and vertical measures. Another way to densify isto change the use of old buildings from, for example, warehouses to homes, or demolishentire areas of old buildings to rebuild them with denser and higher settlements.This report is focused on the vertical densification means that the city's existing silhouette isenhanced. Existing buildings are built on at the heights, basement and attics are furnished tohomes or existing buildings torn and replaced with new higher buildings. As with any type ofdensification, some problems occur in vertical densification. The purpose of this report is todefine the problems of vertical densification and how to avoid these problems by usinglightweight elements.The daylight requirements contained in BBR must be taken under consideration when newbuildings are to be planned. There are supposed to be a certain amount of daylight in allrooms in an apartment where you stay more than temporary. When new higher buildings arebuilt, the availability of daylight for adjacent buildings and areas changes, which can be veryproblematic as there are no regulations that control this. Moreover, higher houses mean thatthe noise from the city will bounce and spread differently than before. Several people andfunctions in the same place, which will be a natural extension of a densification, will alsoincrease noise levels.Vertical densification of cities poses new challenges even regarding the fire protection. Whenhouses are built higher, not only more people but sometimes even other businesses is situatedinto the building which often entails new requirements regarding fire safety must be met.Building on new floors on existing buildings gives greater fire-tech challenges than if a newhouse is being built on the ground. The properties to be built on were often imposed whenother fire requirements applied, so even these must be adapted to meet the new fire protectionrequirements.The accessibility of buildings is also an important aspect to be taken under considerationwhen constructions are to be made. If a building exceeds three floors, a lift is required forwheelchair users to have access to the building. These rules apply to the construction of newbuildings as well as to the alteration of existing buildings. The new floor plan must meet allrequirements set by BBR regarding accessibility.One problem that becomes apparent when additional floors are to be built on top of existinghouses is how the existing building will be able to carry the new floors. Therefore, a rigorousinvestigation of this must always be done before a build-up is commenced. In order to reducethe load on existing construction, construction can be made using lightweight constructionelements. Regarding the various problem areas that emerged can be seen that it is only in theproblem regarding how the existing building is supposed to carry the extra weight where thedifferent methods of building differ greatly. In most areas no, big difference is seen at all.
17

Anforderungen an eine Methode zum leichtbaugerechten Konstruieren

Posner, Benedikt, Keller, Alexander, Binz, Hansgeorg, Roth, Daniel 26 September 2017 (has links) (PDF)
Leichtbau beabsichtigt, die Funktion des Produkts bei gleichbleibendem Gewicht zu steigern (Wiedemann 2007). Leichtbaugerechtes Konstruieren verbessert die Funktionserfüllung bei konstantem Gewicht oder senkt das Gewicht bei gleicher Funktionserfüllung. Da auf Produkte neben der Erdbeschleunigung auch noch weitere Beschleunigungen und damit Kräfte wirken, ist nicht das Gewicht, sondern vielmehr die Masse neben der Funktion die entscheidende Eigenschaft, die im Leichtbau optimiert werden soll. Um folglich Produkte leichtbaugerecht zu konstruieren, müssen diese sowohl funktions- als auch massegerecht konstruiert werden. Die funktions- und massegerechte Konstruktion von Produkten kann den Energieverbrauch eines Produkts, wie z. B. den Kraftstoffverbrauch eines Fahrzeugs, reduzieren und damit dessen ökonomische und ökologische Eigenschaften verbessern (Ponn & Lindemann 2011). Zusätzlich zur Massenreduzierung kann eine verbesserte Massenverteilung die physische Belastung des Produktnutzers reduzieren, indem Kräfte und Momente, die durch die Masse auf den Nutzer ausgeübt werden, minimiert werden. Außerdem kann eine bessere Massenverteilung weitere dynamische Produkteigenschaften verbessern, z. B. höhere erreichbare Kurvengeschwindigkeiten eines Kraftfahrzeugs. Die Massen- und Trägheitsmomentreduzierung kann außerdem höhere Beschleunigungen ermöglichen (Ponn & Lindemann 2011). Zu einem ganzheitlichen leichtbau- und damit funktions- und massegerechten Konstruieren gehört folglich die Betrachtung der Masse, der Massenverteilung und des Trägheitsmoments.
18

Anforderungen an eine Methode zum leichtbaugerechten Konstruieren

Posner, Benedikt, Keller, Alexander, Binz, Hansgeorg, Roth, Daniel January 2012 (has links)
Leichtbau beabsichtigt, die Funktion des Produkts bei gleichbleibendem Gewicht zu steigern (Wiedemann 2007). Leichtbaugerechtes Konstruieren verbessert die Funktionserfüllung bei konstantem Gewicht oder senkt das Gewicht bei gleicher Funktionserfüllung. Da auf Produkte neben der Erdbeschleunigung auch noch weitere Beschleunigungen und damit Kräfte wirken, ist nicht das Gewicht, sondern vielmehr die Masse neben der Funktion die entscheidende Eigenschaft, die im Leichtbau optimiert werden soll. Um folglich Produkte leichtbaugerecht zu konstruieren, müssen diese sowohl funktions- als auch massegerecht konstruiert werden. Die funktions- und massegerechte Konstruktion von Produkten kann den Energieverbrauch eines Produkts, wie z. B. den Kraftstoffverbrauch eines Fahrzeugs, reduzieren und damit dessen ökonomische und ökologische Eigenschaften verbessern (Ponn & Lindemann 2011). Zusätzlich zur Massenreduzierung kann eine verbesserte Massenverteilung die physische Belastung des Produktnutzers reduzieren, indem Kräfte und Momente, die durch die Masse auf den Nutzer ausgeübt werden, minimiert werden. Außerdem kann eine bessere Massenverteilung weitere dynamische Produkteigenschaften verbessern, z. B. höhere erreichbare Kurvengeschwindigkeiten eines Kraftfahrzeugs. Die Massen- und Trägheitsmomentreduzierung kann außerdem höhere Beschleunigungen ermöglichen (Ponn & Lindemann 2011). Zu einem ganzheitlichen leichtbau- und damit funktions- und massegerechten Konstruieren gehört folglich die Betrachtung der Masse, der Massenverteilung und des Trägheitsmoments.
19

En jämförelsestudie mellan olika ljudisoleringsmaterial i träbjälklag ur ett miljöperspektiv / Comparative research between different sound insulation materials in timber floors from an environmental perspective

Anwia Shlimon, Atrn, Al Jazar, Ahmed January 2019 (has links)
Purpose: The building industry has a big environmental impact. The timber construction can reduce the impact of the industry because timber is an environmentally friendly material. One of the biggest problems with lightweight construction is sound insulation. The aim of this report is to study two floor construction with different sound insulation materials from an environmental perspective. The materials that will be studied in this report are sand and macadam. The aim of the report is to create a clear comparison between these floor layers and to suggest an improvement proposal. Method: The methods that have been used in the report are literature studies, life-cycle assessment, document analysis and interview. The LCA, document analysis and literature studies are the starting point, based on these methods, the first two questions in this paper will be answered. Using the interview was able to conduct information for the last question. Findings: This study has shown that sand has a less environmental impact than what macadam has. The improvement proposal that has been suggested in this study is using sawdust with sand as sound insulations layer. Decreasing the amount of sand in floors can have a positive effect on the environment. Implications: As a conclusion of this paper, it is proven that sand as a sound insulation material is more favorable for the environment than the macadam. The reason is caused by the process of extracting macadam. The process is more complicated and more energy demanding. Another conclusion is that reducing the amount of sand and replacing the missing amount with sawdust can reduce the environmental impact and increase the sound insulation ability. A recommendation for similar papers more abilities could be included in the analysis to provide a more including and fair result. Limitations: This paper is limited to investigate sound insulation materials combined with CLT-slabs exclusively. The methods which have been used provided relevant data to help this paper create conclusions. The goal was to create an all-around answer so that the result could be applicable in other analysis. Keywords: LCA, sand, macadam, lightweight construction, impact sound insulation, environment.
20

A Unit Cell Approach for Lightweight Structure and Compliant Mechanism

Wang, Hongqing Vincent 28 November 2005 (has links)
Cellular structures are present from the atomic level all the way up to patterns found in human skeleton. They are prevailing structures in the nature and known for their excellent mechanical, thermal, and acoustic properties. Two typical types of cellular structures, lightweight structures and compliant mechanisms, are investigated. Lightweight structures are rigid and designed to reduce weight, while increasing strength and stiffness. Compliant mechanisms are designed to transform motions and forces. Most available artificial lightweight structures are patterns of primitives. However, the performance of lightweight structures can be enhanced by using adaptive cellular structures with conformal strut orientations and sizes, like the trabeculae in femoral bone. Bending, torsion, and nonlinear behaviors of compliant mechanisms have not been sufficiently studied. In order to design adaptive cellular structures, a new unit cell, the unit truss is proposed. The unit truss approach facilitates the design of adaptive cellular structures for enhanced mechanical properties via geometric modeling, finite element analysis, shape optimization, and additive fabrication. Four research questions, which address representation, structural analysis, design synthesis, and manufacturing respectively, are raised and answered. Unit truss enables representation and mechanics analysis for adaptive cellular structures. A synthesis method using engineering optimization algorithms is developed to systematically design adaptive cellular structure. Two examples, graded cellular structure for prosthesis and compliant mechanism for morphing wings, are studied to test the unit truss approach.

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