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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.
51

Potential for electric vehicle smart charging station expansion at Fyrisskolan

Atterby, Alfred, Bluj, Jakub, Sjögren, Elias January 2018 (has links)
The purpose of this bachelor thesis is to investigate the potential for electric vehicle charging at the high school Fyrisskolan, located in central Uppsala. The idea relies on charging electric vehicles (EV:s) outside of the hours of peak power consumption of the school which in this report is assumed to be solved by a suitable smart charger. In this project, various stochastic models are built to simulate solar energy production and school energy consumption using data collected from various sources. This generated data along with  driving distances and EV:s energy consumptions are used to calculate the available energy for EV charging. The available energy is then used to distinguish a minimal, mean and maximal amount of cars that could potentially be charged outside Fyrisskolan for each chosen month. The data collected is taken from December, March and June. Calculations and simulations are done in MATLAB. Results show that with available energy outside the peak energy consumption hours, there is a possibility to charge around 104 EV:s in one work day. The main conclusion is that there is not only a big potential to expand the charging of EV:s outside the school by installing smart charging stations in a technical view, but also a desire from employees at the school and neighbours living near it, to charge their future electric vehicles.
52

Some experimental fracture mechanics studies in mode I of concrete and wood

Daerga, Per-Anders January 1992 (has links)
Godkänd; 1992; 20080407 (ysko)
53

Lämplighet för skumbitumenstabilisering i det svenska vägnätet

Molin, Emanuel January 2018 (has links)
No description available.
54

Funding public school infrastructure: An overview of selected impacts and reconceptualization of state aid, with insights from three representative Kansas school districts

Adams, Kellen James January 1900 (has links)
Doctor of Education / Department of Educational Leadership / David C. Thompson / The present study, Funding public school infrastructure: an overview of selected impacts and reconceptualization of state aid, with insights from three representative Kansas school districts sought to provide insights and new possibilities regarding public school infrastructure in the state of Kansas. The study was conducted in three separate, yet interconnected phases. Phase One provided for an in-depth literature review of past school finance formulae, litigation, and other important historical contexts at both a national level and more specifically within Kansas. Phase Two then sought to provide for an in-depth statistical analysis using common exploratory statistics of the three proposed funding alternatives to the bond and interest state aid formula. Finally, Phase Three provided for a practical application and lived experienced of the proposed alternatives through interviews with three selected school district representatives. Collectively, these three phases provided for a wealth of applicable and otherwise highly considerable solutions to the current funding mechanisms for capital infrastructure in the state of Kansas. The population for this study included all 286 school districts in the state of Kansas. The data used for the three proposed alternatives was provided by the Kansas State Department of Education and is from the 2015 audited fiscal year reports. The three selected school districts that were chosen for deeper discussion and analysis were USD 446-Independence, USD 490-El Dorado, and USD 491-Eudora. Results from the study revealed a wealth of insights that are both plausible and considerable for policymakers and legislators. Alternative one, which proposed applying general fund principles to the bond and interest fund would provide for the most assistance to school districts, but represented a straight cost increase to the state. Alternative two, which replaced property value measures (assessed valuation) with income-based measures (median household income) was cost neutral to the state, with both winners and losers. The final alternative provided for a complete policy shift away from mill levies tied only to districts that had incurred debt and moved towards a mandatory and uniform mill rate across all districts, while also creating a surplus pool from which districts could draw for capital infrastructure spending. The final alternative was again cost neutral to the state with a number of winners and losers, but provided for a means to an end that neither of the other two alternatives provided – an avenue for school districts to obtain capital infrastructure funding that would not require a majority vote by district patrons. The present study provided both an analysis of the current state of affairs, as well as a challenge to abandon current policy structures and begin to rethink how bricks and mortar within the state of Kansas are funded. The growing backlog of deferred maintenance, as well as the conclusion that the accident of residence will affect a child’s educational experience served as the necessary precursors and motivation for the recommendations and conclusions that were provided as a result of this study.
55

Temperature stresses in massive concrete structures : viscoelastic models and laboratory tests

Emborg, Mats January 1985 (has links)
<p>Godkänd; 1985; 20080404 (ysko)</p>
56

Risk allocation in public private partnership infrastructure projects

Zittlau, Werner Gustav 06 December 2011 (has links)
M.Comm. / The creation of infrastructure services and products has traditionally been the responsibility of the government, but this has changed with the private sector becoming more involved through public private partnerships. This change has been driven by the need for better value for money to the end user and the private sector's ability to achieve higher efficiencies. The extent to which value for money will be achieved will be largely dependent on the correct risk allocation between the parties involved. An optimum risk allocation will ensure that the risk. Pricing is kept to a minimum and thus achieve a cost effective product or service.
57

Plastic Shrinkage Cracking in Concrete

Sayahi, Faez January 2016 (has links)
Early-age (up to 24 hours after casting) cracking may become problematic in any concrete structure. It can damage the aesthetics of the concrete member and decrease the durability and serviceability by facilitating the ingress of harmful material. Moreover, these cracks may expand gradually during the member’s service-life due to long-term shrinkage and/or loading. Early-age cracking is caused by two driving forces: 1) plastic shrinkage cracking which is a physical phenomenon and occurs due to rapid and excessive loss of moisture, mainly in form of evaporation, 2) chemical reactions between cement and water which causes autogenous shrinkage. In this PhD project only the former is investigated. Rapid evaporation from the surface of fresh concrete causes negative pressure in the pore system. This pressure, known as capillary pressure, pulls the solid particles together and decreases the inter-particle distances, causing the whole concrete element to shrink. If this shrinkage is hindered in any way, cracking may commence. The phenomenon occurs shortly after casting the concrete, while it is still in the plastic stage (up to around 8 hours after placement), and is mainly observed in concrete elements with high surface to volume ratio such as slabs and pavements. Many parameters may affect the probability of plastic shrinkage cracking. Among others, effect of water/cement ratio, fines, admixtures, geometry of the element, ambient conditions (i.e. temperature, relative humidity, wind velocity and solar radiation), etc. has been investigated in previous studies. In this PhD project at Luleå University of Technology (LTU), in addition to studying the influence of various parameters, effort is made to reach a better and more comprehensive understanding about the cracking governing mechanism. Evaporation, capillary pressure development and hydration rate are particularly investigated in order to define their relationship. This project started with intensive literature study which is summarized in Papers I and II. Then, the main objective was set upon which series of experiments were defined. The utilized methods, material, investigated parameters and results are presented in Papers III and IV. It has been so far observed that evaporation is not the only driving force behind the plastic shrinkage cracking. Instead a correlation between evaporation, rate of capillary pressure development and the duration of dormant period governs the phenomenon. According to the results, if rapid evaporation is accompanied by faster capillary pressure development in the pore system and slower hydration, risk of plastic shrinkage cracking increases significantly.
58

Carbon fibre reinforced polymers for strengthening of structural elements

Carolin, Anders January 2003 (has links)
There is a large need for strengthening of concrete structures all around the world. There can be many reasons for strengthening, increased loads, design and construction faults, change of structural system, and so on. The need exists for both strengthening in flexure as well as in shear. Plate bonding with Carbon Fibre Reinforced Polymers, CFRPs has shown to be a competitive method for upgrading existing structures load bearing capacity. When applying composites for increased shear capacity, special concerns need to be taken for design with truss model. A limitation factor of approximately 0.6 must be used due to linear elastic behaviour. When limitation on maximum strain in concrete is applies, the allowable strain in the composite will be even lower due to anisotropy and divergence in fibre and principal strain direction. By bonding CFRP to a structure in sawn grooves some advantages compared to traditional plate bonding may be achieved. It is also found that a structure may be strengthened with live loads during strengthening process. CFRP plate bonding may further be used for strengthening for increased buckling load bearing capacity for steel members subjected to compression and a design proposal is presented. Suggestions for further research are identified and presented. / Godkänd; 2003; 20061106 (haneit)
59

Evaluation of the Load Carrying Capacity of a Steel Truss Railway Bridge : Testing, Theory and Evaluation

Häggström, Jens January 2016 (has links)
A good deal of resources has been invested in building and maintaining existing infrastructure.Many structures are now becoming old and do not meet the requirements of an increasingtraffic load, or are reaching the end of their lifecycle. It is not possible or sustainable to replaceall those structures that have been judged to be obsolete or nearly obsolete. However, in manycases, their specified load carrying capacities are understated, so there is an urgent need toobtain more robust knowledge of their true status. In the design of new structures, a numberof assumptions relating to loading and structural behaviour have to be made, a number that canbe reduced by finding out more about the actual behaviour of the structure. This licentiate thesis describes the structural behaviour of existing unballasted open steel trussrailway bridges in general and methods for assessment in particular, with the aim of keepingthese structures in service for longer. An extensive program, divided into three phases of experimental studies, was carried out toincrease the understanding of existing unballasted steel truss railway bridges. Phase I consisted of instrumentation and monitoring of a 60 year-old railway bridge (ÅbyBridge) while it was still in service. A description of the object and the monitoring in thisphase of measurements is presented in Chapter 3 with some results and analysis in Chapter 4.Some of the findings from Phase I are described in Paper A, from which it was concluded thatthe stringer beams were subjected to large stresses originating from torsion and out-of-planebending. These effects are not normally considered yet may have significant consequences inrelation to fatigue. In Phase II, the former bridge over the Åby River was replaced and put beside the railwaytracks, where the instrumentation from Phase I was extended. The bridge was statically testedin 18 pre-defined load series before reaching failure. Phase II is described in Chapter 3 andsummarized in Paper B. It was found that the bridge could withstand loading corresponding tofour times the highest permitted axle-loading, or twice the design load for new bridges, beforeexhibiting an obvious non-linear behaviour with regard to vertical displacement in the midspan.The peak load was achieved at loading approximately 50% higher than the initial nonlinearbehaviour, where lateral buckling of the top chord limited the structure from carryingmore load. The failure can be concluded as being redundant without brittle failure of any ofthe connections. In Phase III, a different bridge was fitted with instrumentation and monitored while subjectedto live loading: the bridge over the river Rautasjokk. The Rautasjokk Bridge was constructedfive years later than the Åby Bridge, using the same drawings thus making it theoreticallyidentical in terms of geometry and material. It is situated along the “Ore line”, meaning that itis subjected to higher loads compared to the Åby Bridge which was located along the “Mainline”. The program for measurements originated from a code-based assessment which ruled thebridge unsafe to use with regard to fatigue of the stringers due to the gusset plates welded tothe top flange of the stringers. Paper C describes the measurement of local fatigue strains (hotspot)and comparison with nominal strains. In that paper, it was concluded that the hot-spotapproach was only favourable for one out of three studied positions, with regard to fatiguelifespan. This thesis ends with conclusions and suggestions for further research.
60

Tensile fracture of ice : test methods and fracture mechanics analysis

Stehn, Lars January 1993 (has links)
This thesis is concerned with several aspects of fracture of both brackish (low salinity) sea ice and freshwater ice. The tests and analyses are confined to tensile, or in fracture mechanics language, Mode I, fracture. A large part of this thesis is dedicated to demonstrate that Linear Elastic Fracture Mechanics (LEFM) can be applicable on ice by laboratory and in-situ tests of defined specimens. All interpretations are made using the dicipline of LEFM.First, the development of a field test equipment called FIFT ( a Field Instrument for Fracture toughness Tests on ice) is described. The FIFT is used in both field and laboratory fracture toughness tests on brackish sea ice from the Gulf of Bothnia to describe porosity effects on the apparent fracture toughness, KQ, and estimate crack velocities. An appropriate speciment size, in terms of notch sensitivity, is then provided valid for grain sizes ranging from 1.6 to nearly 100 mm.An augmented use of the FIFT is then described where fracture toughness tests are performed on S1 type freshwater ice to investigate if similarities exist in the local KI fields for three different fracture geometries. The results indicate that, under comparable conditions, KQ is similar for all of the geometries. However, the type of specimen, has a marked influence on the character of the fracture surface.Then, the influence of structural anisotropy on the fracture toughness of S1 ice is investigated by fabricating and testing three different fracture geometries from a single ice core. This approach is suitable for both field and, as in this work, laboratory studies. There is a wide scatter in the KQ values. Possible explanations to the results are discussed in terms of the microstructural influences and specimen size effects.Finally, crack growth resistance measurements on large grained S1 ice is conducted. A new fracture geometry is used which is found to be extremely favorable of promoting stable, stick-slip, crack growth over a large portion of the uncracked ligament. Now a complete characterization of the fracture resistance curve is therefore possible, A negative fracture resistance KR-curve is evaluated for the S1 ice at -16°C. / Godkänd; 1993; 20070426 (ysko)

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