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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.
91

Optimalizace složení dřevoplastových kompozitů s ohledem na jejich využití ve stavebnictví / The optimization of the wood polymer composite composition regarding its utilization in building structures

Benešová, Anna January 2017 (has links)
Wood-polymer composite is a relatively new type of material that combines shattered wood mass and a thermoplastic polymer. This material is utilized especially as an alternative to hard wood in the area of non-bearing exterior elements, as it reaches better properties in terms of the basic durability and low maintenance. Raw material composition and processing of the composite enable to provide a significant modification with further matters leading to an improvement of the end-product properties. Research and development in this field focuses predominantly on the utilization of such modifying additives that either enhance the resistance to weathering or are of the recycled nature, as a significant part of the raw material mixture comprises the constituent obtained from non-renewable resources. The aim of the thesis is the evaluation of the influence of the wood-polymer composite modification separately at two levels. First of them is the modification to matrix by using a recycled polymer, the second one comprises the modification of the wood flour with a secondary spherical filler. Both types of modified composites have been assessed in terms pf the prime characteristics and the resistance to adverse ambient.
92

Betongfyllda HSQ-balkar : Ett alternativ till traditionellt brandskydd / Concrete filled HSQ-beams : An alternative to traditional fire protection

Samuelsson, Alexander, Gårdefors, Peter January 2018 (has links)
Den brandskyddsmetod av bjälklagsbalkar som används mest idag är brandskyddsfärg och brandskyddsskivor. Dessa metoder kräver ett extra arbetsmoment efter att balken är monterad. Genom att fylla balken med betong samtidigt som hålbjälklagskarvarna fylls och på så sätt integrera brandskyddet i balken kan ett extra arbetsmoment undvikas. Byggnadstekniska Byrån har märkt ett intresse från beställare att i ett tidigt skede få in brandskyddet i projekteringen.  Målet är att undersöka om betong, ingjuten i en HSQ-balk kan få balken att uppfylla de brandskyddskrav som idag ställs enligt Boverkets byggregler. Målet är även att ta reda på om det är kostnadseffektivt jämfört med brandskyddsfärg.  Referensobjektet som används är en skola på tre våningar och balken som undersöks är den som tar upp de största lasterna i projektet. Balken ska enligt Boverkets byggregler klara av en standardbrand i 60 min. Temperaturanalysen av balktvärsnitten har gjorts i Ansys Aim 18.2 och dimensioneringsmetoder av balken sker enligt Eurokoder.  Balken som idag finns på plats skulle inte i oskyddat tillstånd klara av en standardbrand i 60min. De utförda beräkningarna visar att balken i samverkan med betong och armering i tvärsnittet skulle klara momenten och tvärkrafterna i referensobjektet. Fenomen så som spjälkning av betong, dess inverkan på betongens hållfasthet samt armeringens vidhäftning har inte kunnat tas i beaktning. Därför rekommenderas att balkens underfläns dimensioneras upp från 20mm till 30mm och enbart betraktar den ingjutna betongen som kylande medium.
93

Stanovení požární odolnosti konstrukcí / Determination of fire resistance of structures

Jindra, Daniel January 2019 (has links)
Possibilities of modeling non-linear behavior of concrete within standard room temperatures and increased fire-load values using FEM software ANSYS are studied. Temperature dependences of material models are considered. Fire resistance of reinforced concrete and concrete-steel composite construction is analyzed. Fire loads are defined in accordance with relevant standards. Non-linear structural transient analyses are calculated after temperatures were determined by transient thermal analyses. Results obtained from analyses of simple reinforced concrete structure are compared with approach of isotherm 500 °C method.
94

Návrh železobetonového objektu s ohledem na požadavky požární odolnosti / Design of reinforced concrete structure with respect to fire resistance requirements

Pivodová, Alena January 2019 (has links)
The diploma thesis deals with an analysis of internal forces of B4 reinforced construction of an office building. Analysis takes into account interaction with subsoil and when designing structural parts of the building, different requirements for fire resistance of a structure are taken into account. A Dlubal RFEM 5.17 program was used for finite element analysis, and model functionality verification was performer by using a summation of moments method. The thesis deals with the design and assessment of a point-supported slab, column, inner and external walls.
95

Stavebně technický průzkum objektu poškozeného požárem / Architectural and technical inspection of building damaged by fire

Rozsypalová, Iva January 2015 (has links)
Diploma thesis summarizes knowlegde related to the behavior of structures and material in the fire, focusing mainly on concrete and reinforced concrete structures. It deals with the design and implementation of diagnostic work of Building no. 103 in complex Svit Zlín affected by a large fire. There are presented evaluation of laboratory experiments of samples and static analysis.
96

Investigation of Polyhedral Oligomeric Silsesquioxanes for improved fire retardancy of hybrid epoxy-based polymer systems / Etude des Polyhedral Oligomeric Silsesquioxanes (POSS) pour l'amélioration de la tenue au feu de systèmes polymères hybrides époxy

Laik, Suzanne 12 December 2014 (has links)
Les matériaux composites à matrice polymère thermodurcissable interviennent dans de nombreux domaines d’application, parmi lesquels le secteur des transports. Ils présentent toutefois une faible tenue au feu qui limite leur utilisation pour des raisons évidentes de sécurité. De par les restrictions de plus en plus exigeantes de la Commission Européenne (REACH), il existe un réel besoin de se tourner vers des solutions alternatives. Des études récentes ont prouvé l’intérêt des Silsesquioxanes Oligomériques Polyhédriques (POSS) comme agents ignifuges, et particulièrement les POSS portant des ligands phenyl. L’objectif de ce travail a été d’étudier comment la tenue au feu de réseaux hybrides époxy-amine pouvait être améliorée par l’ajout de POSS dans ces matériaux. En faisant varier la nature des comonomères époxydes et amines, ainsi que la structure des POSS sélectionnés, des éléments de réponse ont pu être apportés à la question : existe-t-il une relation structure-propriété en ce qui concerne le comportement au feu des réseaux époxydes ? Des POSS fonctionnels et inertes ont été choisis pour cette étude, et une attention particulière a été portée sur le trisilanolphenyl POSS (POSSOH), pour lequel différents procédés de dispersion ont été mis en œuvre. Il a été montré que l’état de dispersion des POSS était significativement influencé par le type de ligands de ces POSS, mais également par le type de prépolymère époxyde utilisé. En particulier, des structures complexes, jamais observées, ont été découvertes dans les réseaux hybrides basés sur la Tétraglycidyl(diaminodiphenyl) méthane (TGDDM). Des études cinétiques visant à comprendre les interactions développées par les POSS au sein des réseaux ont été menées. Un fort pouvoir catalytique de l’association POSSOH avec un composé à base d’aluminium sur les réactions de réticulation a notamment été mis en évidence. D’autre part, les propriétés thermomécaniques des réseaux finals n’ont pas été modifiées de manière significative par l’ajout de POSS. Finalement, une amélioration remarquable de la tenue au feu a été obtenue dans certains cas, notamment par l’ajout de POSSOH en combinaison avec le composé métallique. La tenue au feu des réseaux à base de TGDDM a été identifiée comme étant liée à un mécanisme d’intumescence. / Thermoset polymer composite materials are used in a number of application domains, amongst which the transports sector, but they suffer from poor fire resistance which limits their use for obvious safety and security issues. With the increasingly demanding restrictions from the European Commission, there is a real need to seek for alternative solutions. Recent studies have found the Polyhedral Oligomeric Silsesquioxane (POSS) compounds interesting as fire retardant agents, particularly the POSS bearing phenyl ligands. The present work aimed at investigating how the fire retardancy of hybrid epoxy networks can be improved by incorporating Polyhedral Oligomeric Silsesquioxanes (POSS). In this study, the nature of the epoxy-amine comonomers was varied, as well as the POSS structure. An inert POSS and two multifunctional POSS were selected in order to generate various morphologies. The aim was to answer the question: does a structure-property relationship exist as concerns the fire behaviour of epoxy networks? Particular attention was dedicated to systems containing the trisilanolphenyl POSS (POSSOH) for which different processes of dispersion were implemented. The POSS dispersion state was shown to be greatly influenced by the type of POSS ligands, but also by the epoxy prepolymer nature in the case of the versatile POSSOH. In particular, intricate, never-observed morphologies were discovered in the networks based on Tetraglycidyl(diaminodiphenyl) methane (TGDDM) and containing POSSOH. The study of functional POSS-involving interactions and epoxy-amine kinetics in the model systems revealed the high catalytic power of the combined presence of POSSOH and an aluminium-based catalyst in the model epoxy networks, as well as the occurrence of homopolymerisation. The thermo-mechanical properties were not significantly modified by the addition of POSS. Finally, spectacular improvements in fire retardancy were obtained in some cases, in particular when the POSSOH and the Al-based catalyst were introduced in combination. The fire protection mechanism was attributed to intumescence in the TGDDM-based networks. The addition of POSSOH and the Al-catalyst was found to be efficient in all the epoxy-amine network types, which could not be clearly related to the POSSOH structures but was rather attributed to a chemical synergistic effect.
97

STUDIUM CHOVÁNÍ CEMENTOVÝCH KOMPOZITŮ PŘI PŮSOBENÍ VYSOKÝCH TEPLOT / BEHAVIOUR OF CEMENTITIOUS COMPOSITES EXPOSED TO HIGH TEMPERATURES

Nováková, Iveta Unknown Date (has links)
Fire resistance is becoming increasingly important along with the development of new concrete types with high strength and dense structure with reduced porosity. Such concrete types are susceptible to fire spalling and extensive crack formation. At the moment, there are a limited number of methods for enhancement of fire resistance of existing structures, which could be applied in underground structures with restricted space and limited air exchange, such as tunnels, underground garages or nuclear powerplants. This work is focused on the development of two methods, and both are dealing with porous structure modification. The first method is intentional heat treatment (IHT) method, suitable for the enhancement of fire resistance of existing structures. The second method emphasized the design of air-entrained concrete (AeA-FiResCrete) with the use of “new generation” air-entraining agents suitable for enhancement of fire resistance of newly designed concrete. Testing of compressive strength, porous structure modification was completed by the analysis of “moisture clog,” which contributes to explosive spalling and extensive cracking. The efficiency of developing methods was verified during large-scale testing according to modified ISO834 (m-ISO) curve. No extensive crack formation or explosive spalling was observed during the exposure period during the large-scale testing of slabs with the applied IHT method. The total thickness of the IHT method with configuration IHT200/2, composed of IHT zone and IHT transition zone, penetrated to the depth of 25,5 to 43,0 mm depending upon various concrete types. Moisture clog in AeA-FiResCrete was more significant than in the case of slabs with applied IHT method, and it could be concluded that the IHT method enhances fire resistance of concrete exposed to elevated temperatures without influencing its compressive strength and durability. Results from AeA-FiResCrete testing showed only a slight improvement of its fire resistance.

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