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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

Structural Behaviour of Lapped Cold-Formed Steel Z-Shaped Purlin Connections with Vertical Slotted Holes

Liu, Jingnan January 2014 (has links)
Lapped joints of cold-formed steel (CFS) Z-shaped purlins are extensively used in metal building roof systems. The research that has been carried out so far for these lapped connections is primarily focused on connections with round holes. However, the lapped connections with vertical slotted holes are extensively used in current construction practice to simplify the erection of continuous Z-shaped roof purlins. There is no design guideline or recommendation available for CFS Z-purlin lapped connections with vertical slotted holes. Presented in this paper are the results of an experimental study and analysis of the structural behaviour of lapped CFS Z-shaped purlin connections with vertical slotted holes. 42 flexural tests were performed on lapped CFS Z-shaped purlins with vertical slotted connections with different lap lengths, purlin depths, thicknesses and spans. The flexural strength and deflection of each specimen were measured. The characteristics of moment resistance and flexure stiffness of the lapped purlins were computed. The test results show that the lapped purlins with vertical slotted holes may be more flexible than the lapped purlins with round holes or continuous purlins without lapped joint. Thus, the slotted connections may need greater lap lengths to achieve full stiffness of continuous purlins. The results also indicate that the characteristics of moment resistance and flexural stiffness in the slotted connections are dependent on the ratio of lap length to purlin depth, the ratio of lap length to purlin thickness, the ratio of purlin depth to purlin thickness, and the ratio of lap length to span. Based on the results, design recommendations for evaluating the moment resistance and flexural stiffness of lapped slotted connections were proposed.
12

A influência da não-linearidade física do concreto armado na rigidez à flexão e na capacidade de rotação plástica. / The influence of physical non-linearity of the reinforced concrete on flexural rigidity and on plastic rotation capacity.

Roberto Buchaim 18 July 2001 (has links)
O presente trabalho é uma contribuição para o esclarecimento e a quantificação das influências na deformabilidade e na capacidade portante de elementos unidimensionais de concreto armado em solicitação plana, decorrentes da não-linearidade física dos materiais concreto e aço, bem como da fissuração e do enrijecimento da armadura tracionada, também na sua fase plástica. Para aplicações práticas determinam-se a rigidez à flexão e a capacidade de rotação plástica dos elementos estruturais, o que permite limitar com mais precisão e coerência a demanda de rotação plástica obtida na análise. De início, descrevem-se os comportamentos não-lineares do concreto e do aço, aplicando-se conceitos da Mecânica da Fratura, bem como a atuação conjunta destes materiais, sob os aspectos de aderência e de fissuração. O núcleo deste trabalho concentra-se na obtenção do diagrama momento-curvatura e dos seus pontos principais, e na subseqüente determinação da capacidade de rotação plástica dos mencionados elementos. Consideram-se as seções geradas a partir da seção duplo T assimétrico, com várias camadas de armadura, sujeitas à flexão composta normal. Com dados deste diagrama e através do modelo da viga equivalente simétrica, posteriormente estendido à viga equivalente assimétrica e às vigas contínuas de pórticos planos, determina-se a capacidade de rotação plástica, considerando-se nesta suas múltiplas influências. Por fim, comparam-se os resultados teóricos e experimentais da capacidade de rotação plástica, e resumem-se as principais conclusões encontradas e os pontos que exigem subseqüente desenvolvimento. / The present study is a contribution to the enlightenment and evaluation of the influences on deformability and load carrying capacity of one-dimensional elements of reinforced concrete subject to in-plane loading, arisen from the constitutive non-linearity of concrete and steel, as well as from the concrete cracking and the tension stiffening of the reinforcement, prior and after yielding. For practical applications, the flexural rigidity and the plastic rotation capacity of structural elements are determined, which makes it possible to limit, more precisely and coherently, the plastic rotation demand coming from the analysis. Firstly, the non-linear behaviors of concrete and steel are described, applying concepts of Fracture Mechanics, and then the joint action of both materials concerning bond and cracking is studied. The core of this study lies on obtaining the bending moment-curvature diagram, specially its main points, and on the subsequent determination of the plastic rotation capacity of the aforementioned elements. The cross-sections generated from an asymmetric double T cross-section are considered, with several layers of reinforcement, acted upon simple or combined bending about one principal axis. With data based on this diagram and through the model of equivalent symmetric beam, later extended to equivalent asymmetric beam and to continuous beams of plane frames, the plastic rotation capacity is determined, considering its multiple influences. Finally, theoretical and experimental results of plastic rotation capacity are compared, and the main conclusions and points in need of subsequent development are summarized.
13

Cortical Bone Mechanics Technology and Quasi-static Mechanical Testing Sensitivity to Bone Collagen Degradation

Custer, Erica M. January 2019 (has links)
No description available.
14

Beteende hos laminerade glasbalkar med och utan sprickor / Behaviour of laminated glass beams with and without cracks

Basim, Weaam, Abdul Khader, Nour, Rehsid, Vijan January 2020 (has links)
Det blir allt vanligare att använda laminerat glas som ett konstruktionsmaterial. Men glas är ett känsligt och genomskinligt material som kan ge en obehaglig känsla om det spricker. Särskilt om det handlar sig om en glaskonstruktion som ska hålla en stor del av en byggnad. En glaskonstruktion bör upplevas trygg att vistas i. Idag är det svårt att ersätta bärande konstruktionsdelar med glas i Sverige  eftersom det inte finns några särskilda dimensioneringsregler för glas. I det här examensarbetet genomförs en undersökning om hur laminerat glas böjer sig när det utsätts för belastning och varierande temperaturer under en kort tid. Det studeras hur tjockleken på mellanskiktet påverkar spänningen samt skjuvstyvheten i glasen. För att få relevanta jämförelser studeras även beteendet hos en osprucken och en sprucken laminerad balk. Med hjälp av litteraturstudier och teoretiska beräkningar har beteendet hos laminerade glasbalkar med olika förutsättningar undersökts. Resultatet visar att belastningar som verkar på en laminerad balk under en kort tid leder till ett varierande beteende och deformationer beroende på temperatur, skjuvstyvhet och tjocklek hos laminatet. Det upptäcktes ett gränsvärde vid temperaturen 50 °C där en förändring sker i sambandet mellan laminatets tjocklek, temperatur och nedböjningen. Beteendet och deformationen hos en laminerad balk varierar också beroende på om balken är sprucken eller inte. / It is becoming increasingly common to use laminated glass as a construction material. But glass is a sensitive and translucent material that can give an unpleasant feeling if it cracks. Especially if it is a glass structure that will hold a large part of a building. A glass structure should be considered safe to stay in. Today, it is difficult to replace supporting structural parts with glass in Sweden due to the lack of design rules. In this thesis, a study is conducted on how laminated glass bends when exposed to mechanical loads and varying temperatures for a short time. It is studied how the thickness of the middle layer plays a role, how the tension and the shear stiffness vary in the glass. In order to obtain relevant comparisons, the behavior of an unbroken and a cracked laminated beam is also studied. With the help of literature studies and theoretical calculations, the behavior of laminated beams under different conditions was examined. The results show that loads that act on a laminated beam for a short time lead to varying behavior and deformations depending on temperature, shear stiffness and interlayer thickness. A limit value was detected at the temperature of 50 °C where a change in the relation between interlayer thickness, temperature and deformation occurs. The behavior and deformation of a laminated beam also varies whether the laminate is cracked or not cracked.
15

Cortical Bone Mechanics Technology (CBMT) and Dual X-Ray Absorptiometry (DXA) Sensitivity to Bone Collagen Degradation in Human Ulna Bone

Warnock, Sarah M. January 2019 (has links)
No description available.
16

Validation of Mechanical Response Tissue Analysis by Three-Point Mechanical Bending of Artificial Human Ulnas

Arnold, Patricia A. 03 June 2013 (has links)
No description available.
17

Comparison of Cortical Porosity, Diameter, and Stiffness as Predictors of Ulna Bending Strength

Hausfeld, Gabrielle Christine 30 April 2015 (has links)
No description available.
18

Posouzení vlivu nového hlubinného základu na konstrukci primárního kolektorového tunelu / The impact assessment of a new deep foundation for the structure of the primary service tunnel

Lipka, Miroslav January 2012 (has links)
The purpose of the diploma thesis is assess the impact of piles on primary collector lining. Using a mathematical model has been calculated interaction between pile ond collector lining. The main task is to decide the length dependence of the pile deformations and internal forces that are the concrete lining of the collector.
19

Undersökning av mekaniska egenskaper hos sandwichelement av core-materialet Greenwood och ytskikt av papp : Styvhet, bärförmåga samt elementens beteenden vid belastning för olika tjocklekar på ytskikten / Examination of mechanical properties of sandwich panels made of the core-material Greenwood and surface layers of paperboard : Stiffness, ultimate capacity and structural behavior for different surface layer thicknesses

Nilsson, Maxim January 2023 (has links)
Byggbranschens utsläpp av växthusgaser utgör en stor andel av Sveriges totala utsläpp. För att minska de byggrelaterade utsläppen är det på många fronter som byggbranschen behöver förändras och effektiviseras. De senaste åren har en succesiv ökning av byggandet i trä skett vilket är gynnsamt då trä alternativet är mer klimatvänligt än stål och betong. De tuffa klimatmålen vi nu står framför innebär dock att mer behöver göras än att endast öka andelen träbyggnader. Pappersmassaindustrin är lätt att bortse ifrån, då den hittills inte varit relevant för byggbranschen och för att återanvändning är relativt framträdande inom den branschen. Ifrån sågverken som sönderdelar trästockar till virke fraktas flis som blir över till pappersbruk. Av flisen görs sedan bland annat diverse pappförpackningar som går att återvinna. Problemet är att dessa förpackningar endast går att återvinna ett visst antal gånger innan fibrerna blir obrukbara och istället används som biobränsle. Om byggmaterial skulle gå att producera baserat på dessa fibrer, skulle detta innebära en mer långlivad användning av dem. Ett byggmaterial som uppfunnits, gjort på fibrer från pappersmassabruk är core-materialet ”Greenwood”. Eftersom materialet är nytt och egenskaperna till stor del är okända krävs det att diverse studier görs som undersöker materialets olika egenskaper som är relevanta för en eventuell tillämpning inom byggbranschen. Denna studie avser att undersöka skjuvstyvhet, böjstyvhet och bärförmåga hos sandwichelement uppbyggda av core-materialet Greenwood och ytskikt av papp. Detta genom att först  dynamiskt och statiskt testa de ingående materialens egenskaper, följt av böjprovning av nio sandwichbalkar med varierande tjocklek på ytskikten. Samtliga balkar testades även dynamiskt. Core-materialet Greenwood som ingick i sandwichelementen var endast den begränsande faktorn en gång av tio böjprov. När core-materialets skjuvstyvhet togs fram både dynamiskt och statiskt och när den omvandlades till en skjuvmodul visade det sig att Greenwood har en mer än dubbelt så stor styvhet som EPS-cellplast vid liknande densitet. Detta är intressant då denna cellplast ofta agerar som ett core-material i sandwichelement ute i byggbranschen. Testerna visar även på att balkarna har en relativt liten spridning vilket innebär att resultaten har god tillförlitlighet. Slutligen, kan det konstateras att dessa sandwichelement uppvisar sega egenskaper med en viss kvarvarande lastkapacitet även efter brott. Samtliga nämnda egenskaper ovan talar för en viss potential för tillämpning av dessa sandwichelement inom byggbranschen. Fortsatta studier av fukt- och krypegenskaper vid långtidsbelastning rekommenderas, vilket är viktigt för användning inom byggandet. De omfattande resultaten från föreliggande studie utgör dock ett bra underlag för fortsatta undersökningar och värdering av möjliga tillämpningar. / The construction industry`s greenhouse emissions, makes up for a large portion of Sweden’s total emissions. In order to reduce construction related emissions, a fair amount of fronts within the construction industry needs to be changed and streamlined. In the last couple of years, there has been a successive increase in the number of structures that are built from wood amongst other things, which is beneficial because the wood alternative is more climate friendly than steel and concrete. The current tough climate goals entails that more has to be done than just increasing the amount of wood constructions. The pulp industry is easy to write off because so far, it has not been relevant to the construction industry and because recycling is relatively prominent within that industry. From the sawmills that dismember wooden logs to lumber, leftover wood chips are transported to paper mills. Among other things, different cardboard packages that can be recycled are then made from those wood chips. The problem with these packages is that they can only be recycled a certain number of times before the fibers become unusable and instead, are used as biofuel. If building materials were to be able to be produced with these fibers, that would be a more long-lived use of them. A building material, recently invented, made of fiber from paper mills is the core-material “Greenwood”. Because the material is new and its properties for the most part are unknown, this requires that various studies are conducted that examines the different properties the material possesses that are relevant for a contingent enforcement within the construction industry. This study intends to examine the shear rigidity, flexural rigidity and maximum capacity for sandwich panels made from the core-material Greenwood and faces of paperboard. This was achieved by first dynamically and statically test the properties of the two different materials, followed by flexure testing nine sandwich beams with varying face thicknesses. Every beam was also tested dynamically. The core-material Greenwood which was a part of the sandwich panels, was only the limiting factor 1 time out of 10 flexure tests. When the shear rigidity of the core-material was calculated both statically and dynamically and when it was converted to a shear modulus it was shown that Greenwood has a rigidity of more than double that of EPS cellular plastic at similar density. This is interesting because this type of cellular plastic often acts as a core-material in sandwich structures found in the construction industry. The tests also show that the beams have a relatively small spread which means that the results have good reliability. Finally, it can be concluded that these  sandwich panels exhibit ductile properties with a certain lasting load capacity even after ultimate load has been reached. Every property mentioned above indicates that there is a certain potential for applicability of these sandwich panels within the construction industry. Continued studies of moisture properties and creep properties during long-term loading is recommended, which is important for a possible use within construction. The extensive results from this study constitutes a good basis for continued research and assessment of possible applications.

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