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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

FE-Analysis of stress variation during diamond cutting of prestressed concrete sleepers

Skoog, Adam, Mohamad Alahmad, Yaseen January 2015 (has links)
The manufacturing process ‘long line method’ has shown many advantages when producing prestressed concrete sleepers, such as rapid production and low cost. However, there have been certain difficulties when cutting the 100 m long concrete blocks into sleepers. The sleepers tend to crack when the diamond cutting blade cuts through the last strands. Moreover, the shape and size of the cracks varies from one sleeper to another. Although these cracks may not affect the load carrying capacity, they will not be aesthetically pleasing. No earlier studies within the area have been found, i.e. diamond cutting of prestressed concrete blocks. As a result, there have been certain difficulties when approaching the problem. Finite element analysis has been proven to be a useful tool when analyzing stress variation. Throughout this project, the cutting simulation has been analyzed using the finite element analysis software ABAQUS. To summarize, stress variation has been examined during different cutting depths. The results from the FE model shows that no critical values were reached in the areas expected to have cracks. The true cause of the problem could not be specified. Therefore, further studies are needed yet this thesis could be a good foundation.
2

Analýza akusticko-vibračních parametrů kolejového roštu / The analysis of acoustic and dynamic parameters of the track skeleton

Ratislavová, Eva January 2013 (has links)
This diploma thesis is focused on experimental measurement and acoustic and dynamic behavior analysis of railway construction with the Y – steel sleepers and their comparison with concrete sleepers. The measurements were taken in situ, in suitable sections of a railway line. These sections meet the requirements of regional railway tracks in the Czech Republic. Monitored parameters were obtained by measuring a response of testing trains and were analyzed using frequency and time analysis. Based on these evaluations, comparisons of particular constructions and their recommendations for practice were made.
3

Detaljstudie av tryckbrott i betongsliprar : Samband mellan tryckprovsresultat och val av dimensioneringsmetod / Detail study of compression failure in concrete sleepers : Correlation between pressure test results and choice of design method

Bülow Angeling, Jenny, Wikell, Sebastian January 2016 (has links)
En jämförelse av Abetongs beräkningsunderlag och statistik från tryckprov visar att sliprarna klarar mycket mer belastning än vad beräkningarna visar. I den här studien har en utvärdering av använda beräkningsmetoder gjorts, samt en jämförelse mellan olika dimensioneringsprinciper för att komma så nära resultaten vid tryckprov som möjligt. Beräkningar med förenklat tryckblock och idealiserad-rektangulär parabolisk arbetskurva visade att det senare alternativet gav ett något högre värde på sliprarnas momentkapacitet, men förändringen förklarade inte varför den verkliga momentkapaciteten är så mycket högre än den framräknade. Den faktor som enligt den här undersökningen påverkar betongens tryckhållfasthet och i sin tur ger en större momentkapacitet än vad tidigare beräkningar visar är förhindrad tvärutvidgning. Studien visar att hänsyn till förhindrad tvärutvidgning bör tas med i beräkningar på betongsliprars hållfasthet. Detta medför att det finns utrymme att minska betongklass på Abetongs slipermodell A26 från C58/70 till C50/60. / A comparison of the calculation data from Abetong and statistics from pressure tests shows that the sleepers can handle more load than the calculations show. In this study, an evaluation of used calculation methods has been made and a comparison between different principles of dimensioning to get as close to the result from the pressure tests as possible. Calculations with rectangular stress distribution and idealized parabola-rectangle diagram showed that the second alternative gave a bit higher value on the sleeper bending moment capacity, but the difference did not explain why the real bending moment capacity is so much higher than the calculated one. According to this study confined concrete gave a larger capacity than the previous calculations. With regards to that effect the compressive strength of the concrete almost doubled, which together with an increased critical strain gave a bending moment capacity very close the one obtained from the pressure tests. This study concludes that the confined concrete effect should be considered when calculating the concrete strength. This also means that there is a possibility to reduce the concrete strength of Abetong’s sleeper model A26 from C58/70 to C50/60.
4

Rekonstrukce železniční stanice Milevsko / Upgrading of Milevsko Railway Station

Křemen, Tomáš January 2015 (has links)
The aim of the diploma thesis is the reconstruction of Milevsko railway station. The platforms with access persons with reduced mobility are designed in this station. The rail substructure and station drainage system design was necessary to do within the reconstruction. New assembly of a switches and crossing is the part of reconstruction design as well.
5

Studie rekonstrukce železniční stanice Prostějov hl.n. / Upgrading of Prostějov hl.n. Railway Station

Raif, Lukáš January 2014 (has links)
The aim of the diploma thesis is the reconstruction of Prostějov hl. n. railway station. The platforms with access persons with reduced mobility are designed in this station. The rail substructure and station drainage system design was necessary to do within the reconstruction. New assembly of a switches and crossing is the part of reconstruction design as well.

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