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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.
1

Förstärkning av betongkonstruktioner med kolfiber med avseende på olika brottstyper / Strengthening of concrete with carbon fibers for different types of failure

Larsson, Niklas, Terner, Erik January 2015 (has links)
The purpose of this report is to simplify the process of designing carbon fiber strengthening for existing concrete constructions, specifically beams. The intention has been to establish a flow chart containing information on the necessary testing and calculations for the design, to as far degree it is possible satisfy the requirements stipulated by Swedish and by extension, European authorities.To do this the report will examine a parking garage situated underground by Akademiska Sjukhuset, Uppsala. The parking garage was built in the mid-seventies, and has in recent years been subjected to a greater load than designed for by the construction of a road on top of it. FEM-Design has been used to obtain the internalforces of the beams and thereby determine whether they are in need of strengthening or not and thereafter design the strengthening according to Täljsten (2006) with some corrections from Täljsten (2011) due to new regulations.The result of this report is that the flow chart used is viable to design carbon fiber strengthening, atleast with the conditions met in our reference project.The conclusion drawn after working with this report is that there is a need for a clear standard for carbon fiber strengthening , preferably a standard that can be used throughout Europe.
2

Interaktion mellan axiell normalkraft och böjmoment enligt Eurokod 3:Dimensionering av stålkonstruktioner : En undersökning kring hur samtidig normalkraft och böjmoment hanteras enligt normerna, dess användbarhet samt skillnader

Forsberg, Gustav, Lundin, Felicia January 2024 (has links)
Below in the report, the various methods available to calculate the interaction formulas for bending moment and normal force in steel columns are examined. The standards compared are SS-EN 1993-1-1:2005 Annex A, SS-EN 1993-1-1:2005 Annex B, SS-EN 1993-1-1:2022, CEN/TS 1993-1- 101:2022 and Fpr EN 1993-1-3:2023. When calculating and comparing, the results show that the methods are similar to each other as below: SS-EN 1993-1-1:2005 Annex A and CEN/TS 1993-1-101:2022 SS-EN 1993-1-1:2005 Annex B and SS-EN 1993-1-1:2022 In Fpr EN 1993-1-3:2023 - General rules - Supplementary rules for cold-formed members and sheeting, a method is given that can also be used for hot-rolled and welded cross-sections, this method has similarities with the one previously used in BSK07. The result shows that the method gives quick results, but which gives a utilization rate about 10 percentage points higher than the other methods for this calculation case. Hence, the group finds it difficult to justify the use of this method with regard to the material consumption compared to other methods. In the case of a welded cross-section with the same moment of inertia in the rigid direction as a hot-formed steel profile HEA180, the result shows a greater spread of utilization rates between the methods. The result shows that the similarities between the methods follow the same pattern as above. The group has identified the reduction factor regarding lateral torsional buckling and its calculation process is what generates differences between the methods. To gain insight into how user-friendly the different calculation methods are, the group has used calculation data from a course in steel construction certification where the course participants are asked to calculate the utilization rate of a column in a hall building and provide comments on the relevant regulations. The group has also done its own survey where the participants would choose one of the four regulations above and perform similar calculations, grade the usability and give short comments on their thoughts on the calculations. Furthermore, the calculations have also been compared with analysis in FEM design, where we can also see that the analysis carried out using SS-EN 1993-1-1:2005 Annex A corresponded with the calculations using the SS-EN 1993-1-1 methods: 2005 Annex A and CEN/TS 1993-1-101:2022. The analysis carried out using SS-EN 1993-1-1:2005 Appendix B as a basis also corresponded with the calculations using the methods SS-EN 1993-1-1:2005 Appendix B and SS-EN 1993-1-1:2022. It can be seen in the surveys that the methods are complicated and that those who participated in the study get different results depending on the choices made and that the equations are complex and require many calculations, which increases the risk of errors. The comments from the surveys show that the participants' opinion generally agrees with the group's own conclusions regarding the difficulities and choices regarding the calculations. With regard to the calculations and comparisons between the methods, the group finds it difficult to justify the choice of a particular calculation method as they are very similar but at the same time have their shortcomings. The group believes that one should carry out more thorough investigations that take into account more load cases, end conditions and cross-sectional shapes if one intends to hopefully find an optimal method.
3

Skillnaden i det dorsala böjmomentet vid MTP, utan rullsula och med två olika styvheter på rullsulan

Kassberg, Fanny, Antonsson, Johan January 2019 (has links)
Bakgrund: Rullsulor används för att kompensera för ledstelhet, förbättra avveckling av steget, minska höga tryck plantart och minska böjningen vid tålederna.  Det finns dock få studier som undersöker om rullsulan verkligen minskar ledrörlighet i framfoten. Det saknas även information för betydelsen av rullsulans styvhet för böjmomentet av framfoten, vid avvecklingen av steget.   Metod: Fem friska kvinnor (n=5) gick med tre olika par skor, två par var modifierade med en likadan rullsula med olika styvheter och ett par utan rullsula. Fem upprepade mätningar för de tre olika skorna samlades in för alla deltagare. Det dorsala böjmomentet analyserades med sensorsulan (VebitoSCIENCE) som ersatte skons innersula.   Resultat: Det dorsala böjmomentet minskade för samtliga deltagare med en rullsula. Signifikant minskning av det dorsala böjmomentet vid MTP 1, för alla deltagare, när den styva rullsulan jämfördes med utan rullsula (94,4 – 20,1 Nmm) och mellan styv och flexibel rullsula för deltagare 1,2, 4 & 5 (68 – 22,2 Nmm).   Konklusion: Det dorsala böjmomentet minskade signifikant för MTP1 och MTP5 när en rullsula användes av friska kvinnor. Studien har också visat att en styv rullsula har en betydelse för att uppnå ett minskat dorsalt böjmoment vid MTP. / Background: Rocker soles are used to compensate for joint stiffness, reduce high plantar pressure and reduce the bending of the toe joints. Despite this, few studies have investigated if the rocker shoe really reduce the joint movement at the forefoot. There is also a lack of information regarding the importance of the rocker shoes stiffness for the bending moment of the forefoot, at the third rocker.   Method: Five healthy women (n=5) walked with three different pairs of shoes, two pairs were modified with the same rocker shape with different stiffness and one pair without a rocker. Five repeated measurements for the three different shoes were collected for all the participants. The dorsal bending moment was analyzed with a sensor sole (VebitoSCIENCE) that replaced the shoes insole.   Result: The dorsal bending moment was reduced for all participants with a rocker shoe. Significant reduction of the dorsal bending moment at MTP1, for all participants, when the stiff rocker was compared to the shoe without rocker (94,4 – 20,1 Nmm) and between the stiff and flexible rocker for participants 1,2,4 and 5 (68 -22,2 Nmm).   Conclusion: The dorsal bending moment was significantly reduced for MTP 1 and MTP 5 when a rocker shoe was used by healthy women, the study has also shown that the stiffness has an importance in order to achieve a reduction of the dorsal bending moment at MTP.
4

Håltagning i limträbalkar : Påverkan och dimensioneringsförändringar

Sundqvist, Ludvig, Söderstedt, Samuel January 2021 (has links)
Approximately one fifth of Sweden’s total emissions of greenhouse gases originate from the construction and real estate sector. In order to minimize the climate footprint in the construction industries, the endeavor is to use as environmentally friendly and sustainable processes and materials as possible. Thus has wooden structures had a recent upsurge where generally more buildings are constructed by wooden materials.  Glulam is often used where the requirements regarding a materials strength is high. Glulam beams are a suitable option as loadbearing constructions in framing of joists. Piercing is frequently required in framing of joists as a result of needed space for ventilation ducts and drain pipes. There is no formally accepted method in Eurocode where piercing is treated. Thus WSP has an interest in what extent piercing of glulam beams is possible.   The purpose of this study is to increase the knowledge regarding the impact that piercing has on a beams load bearing capacity. To examine the impact, three beams of different dimensions are considered where piercing is made in three different placements on the respective beams.  Firstly manual calculations are made by the standards in the Glulam handbook. The results from the method are then checked regarding bending and shear stress. The purpose of the calculations is to determine the maximum hole size and the holes impact on the load bearing capacity for each beam. The methods follows several geometric requirements presented in the Glulam handbook. Similar calculations was also made in Statcon Post&Beams. Statcon is a dimension tool for constructors. A verification of the results from the calculations made by hand was also made.  Lastly the results are presented and analysis is made. Some of the conclusions made were that both calculation methods indicated that piercing should be made as centered as possibly on the beam. The geometrical requirements are a limiting factor since the maximum hole size were restricted on 22 of the 29 beams, even though the calculations proved that bigger holes were possible.
5

Kolfiberförstärkning av betongkonstruktioner med avseende på böjningoch tvärkraft : En hypotetiskt plattrambro modellerad i Brigade Standard och en T-balk / CFRP strengthening of concrete constructions in bending and shear : A hypothetical frame bridge modelled in Brigade Standard and a T-beam

Dagdony, Masara, Rashid, Toba January 2017 (has links)
Samhället ändras konstant men detta innebär inte bara en förändring för människorna i samhället utan också att nya krav ställs på konstruktionen som brukas av människorna. Många byggnadskonstruktioner kan därmed behöva en förstärkning efter en viss tid. Behovet av en förstärkning kan bero på flera orsaker exempelvis ändrat nyttjande. Det är mer fördelaktigt med en förstärkning av konstruktionen än att den rivs ner och byts ut för att klara av dagens krav. Syftet med detta examensarbete är att undersöka förstärkning av betongkonstruktioner med hjälp av kolfiberkomposit. I rapporten presenteras beräkningar som gjordes för att undersöka tillökningen i böjoch tvärkraftskapacitet efter en utförd förstärkning. Parallellt med beräkningarna kontrollerades och utvecklades befintliga mallar som finns för denna metod. För att kunna uppnå syftet undersöktes två hypotetiska betongkonstruktioner. Ena konstruktionen är en plattramsbro som modellerades i FEM programmet Brigade Standard. Beräkningar på plattramsbron gjordes med avseende på böjande moment. Den andra konstruktionen som undersöktes är en T-balk som är en del utav ett bjälklag. På T-balken granskades tvärkraftskapaciteten innan och efter en utförd förstärkning med kolfiber. I resultatet redovisas mängden kolfiber som erfordras för att uppnå önskad kapacitet hos konstruktionerna. I resultatet redogörs också kapaciteten som uppnås efter kolfiberförstärkningen. / The society changes constantly, but this does not only affect the inhabitants of the society, but also that new demands are made on the construction used by the people. Many constructions may therefore require reinforcement after a certain amount of time. The need for reinforcement may be due many different reasons for example to altered use, corrosion to internal reinforcement or may be due to design errors, accidents or new standards. It is more beneficial to reinforce the structure than to tear it down and replace it to meet current requirements. The purpose of this thesis is to investigate carbon fiber reinforced polymer, CFRP, as a method to strengthen concrete structures. The report presents calculations that were made to investigate the increase in bending and shear capacity after a performed reinforcement. Alongside the calculations, existing templates for this method were checked and developed. In order to achieve the purpose, two hypothetical concrete structures were investigated. One design is a frame bridge modeled in the FEM program Brigade Standard. Calculations on the frame bridge were made with respect to bending. The other construction that was investigated is a T-beam. On the Tbeam, shear capacity was examined before and after reinforced carbon fiber reinforcement. The result present the amount of carbon fiber required to achieve the desired capacity of the structures. The result also describes the capacity achieved after carbon fiber reinforcement.

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