Reinforced concrete frame corners (that is, knee joints) subjected to closing moments plays an important role of transmitting stress between the two adjoining members. Being categorized as geometric discontinuity regions (D-regions), knee joints cannot be correctly analyzed and designed using traditional sectional analysis procedures. Instead, the strut-and-tie method is particularly suitable for such joints. Although strut-and-tie models provide the means to represent the distribution of stresses within a closing knee joint, questions arise when a curved-bar node is used to model the bar bend of the longitudinal reinforcement at the outer corner. The code-specified design expressions for curved-bar nodes have not been experimentally verified; therefore, the accuracy and conservativeness of the expressions remain unknown. This research project is aimed to provide insights to the proper application of the strut-and-tie method, through the concept of curved-bar nodes, to knee joints under closing moments.<br><br>An experimental program consisting of 24 specimens was conducted to investigate the effect of curved-bar nodes on knee joints under closing moments. An evaluation of the code-specified design expressions was included. The results demonstrate that the minimum code-specified bend radius is appropriate. The current requirements related to bond along the bar bend and clear side cover are shown to be conservative. Based on the test results, a procedure for constructing proper strut-and-tie models for closing knee joints is proposed and verified using an evaluation database consisting of 116 knee joint tests from the literature. Compared to other strength predictive methods and the code-specified strut-and-tie method, the proposed strut-and-tie method mitigates unconservativeness and delivers improved accuracy.<br>In addition to the experimental program and the proposed procedure, non-linear finite element analysis (FEA) using the software ATENA-3D was employed to conduct a parametric analysis as a supplement to the experimental data. Seventy-two numerical models were analyzed to further evaluate the code-specified expressions and the proposed strut-and-tie method. The FEA results are in a good agreement with the experimental observations and corroborate the conclusions from the experimental program regarding current code requirements. Moreover, the parametric analysis further supports the application of the proposed strut-and-tie methodology to knee joints under closing moments.

Falls continue to be a major problem in the residential construction industry and account for a large number of injuries and fatalities each year (US Department of Labor, 2012).  The effects of a fall are catastrophic to the workers and their families as well as the construction company and surrounding community.  Prevention of these incidents has been the primary focus of organizations such as the Occupational Safety and Health Administration (OSHA).  To reduce the number of falls on residential construction sites, OSHA has put forth several standards that require the use of fall protection.  Although guidelines have been provided, there have been concerns and complaints regarding the standards as well as methods and materials that should be used. The goal of this research was to measure the behavior of a five truss roof system with various anchor points and bracing configurations loaded by a horizontal force.  A lab built roof system was used to test three different anchor types with three forms of temporary bracing.  The materials and methodology used in this testing were based on common materials and practices currently used in the residential construction industry. The results of this research show that anchors must engage multiple trusses to spread the applied load throughout the roof system.  Several forms of temporary bracing such as lateral, diagonal, and sway bracing, are also required to strengthen the roof system allowing it to withstand an applied load. / Master of Science

Bakgrund: Helamning rekommenderas de första sex månaderna och har många hälsomässiga fördelar för både moder och barn. Svårigheter vid amning kan kopplas till tidiga amningsstopp och kort tungband kan vara en orsak till dessa amningssvårigheter. Syfte: Syftet är att belysa mödrars erfarenheter av amningssvårigheter relaterat till kort tungband och av tungbandsklipp. Metod: Kvalitativ studie med induktiv ansats baserades på semistrukturerade intervjuer med tio informanter via video- eller telefonsamtal, strategiskt utvalda utifrån inklusions- och exklusionskriterier. Materialet analyserades med en tematisk innehållsanalys. Resultat: Mödrarnas erfarenheter av amningssvårigheter relaterat till kort tungband och tungbandsklipp kan visa sig som både fysiska eller psykiska symtom så som smärtande bröstvårtor och ångest. Flera av mödrarna upplevde att deras amningssvårigheter inte blev hörda eller uppmärksammade av vårdpersonalen samt att de upplevde ett bristande stöd. Flera upplevde också att det fanns en kunskapsbrist beträffande kort tungband inom vården och ett fåtal av mödrarna visste inte vad kort tungband var eller vad det innebar. Flera av mödrarna upplevde även att informationen kring själva tungbandsklippet var bristfällig samt vad de kunde vänta sig för resultat efteråt. Slutsats: Mödrar och barn med amningssvårigheter relaterat till kort tungband och tungbandsklipp får olika bemötande, bedömningar och åtgärder beroende på vilken kunskap som den vårdkontakt de möter besitter. Det finns ett behov av att arbeta fram en nationell handlingsplan för kort tungband hos barn för att alla ska få tillgång till samma vård. / Background: Exclusive breastfeeding is recommended the first six months of life and has many health benefits for both mother and child. Difficulties during breastfeeding can be associated with early breastfeeding cessation and tongue-tie can be one of the causes leading to breastfeeding difficulties.  Aim: The aim was to elucidate mothers’ experiences of breastfeeding difficulties in relation to tongue-tie and frenotomy.  Method: A qualitative inductive study based on semi-structured interviews with 10 informants via video- or telephone calls was conducted. Purposive sampling with inclusion- and exclusion criteria was chosen. Data was analyzed using a thematic content analysis.  Result: Mothers’ experiences of breastfeeding difficulties in relation to tongue-tie and frenotomy appear as both physical and psychological symptoms such as nipple pain and anxiety. Many of the mothers expressed that their difficulties were not heard or acknowledged by the health care staff and they also experienced a lack of support. Many of the mothers also experienced a lack of knowledge in the health care system regarding tongue-tie and a few of the mothers did not know what tongue-tie was or what it meant. Several of the mothers also experienced a lack of information regarding the frenotomy and what result they may expect afterwards.  Conclusion: Mothers and children with breastfeeding difficulties in relation to tongue-tie and frenotomy are treated and assessed differently depending on the knowledge of the health care staff. There is a need to develop a national careplan for children with tongue-tie so that all children have the same access to equal care

I det här examensarbetet har olika modelleringsantagandens påverkan på plattbroars och lådbalkbroars dynamiska egenskaper vid modellering av 3D-skalmodeller i FEM studerats. Delar av en bro som kan tänkas behöva någon typ av koppling har analyserats, liksom de kopplingar som är passande för sammanlänkningen av dessa delar. Studien har haft fokus på hur broarnas egenfrekvenser påverkas och hur broarna svarar på passage av höghastighetståg med avseende på accelerations- och förskjutningsamplituder för de olika modelleringsantagandena. De delar av en bro som studerats är kantbalk-konsol, konsol-broplatta, broplatta-stöd, lådbalk-broplatta och lastinföringspunkter-broplatta. Dessa delar har modellerats på olika sätt där till exempel förenklingar i modelleringen jämförts med modeller som är mer lika verkligheten. Resultatet visar att vid tågpassage ger vissa förenklingar från fall till fall responser som kan anses vara mer på den konservativa sidan. I övrigt är dock skillnaderna i respons sammantaget inte så stora. Resultatet visar också på att olika inställningar på kopplingar inte har så stor betydelse på studerade broars egenfrekvenser.

<p> The Fe-C-Mn phase diagram has been calculated from thermodynamic data. Experimentally determined tie-lines are in good agreement with the calculated diagram. </p> <p> It has been shown that the assumption that the austenite-ferrite interface is in a local equilibrium condition during the late stages of the transformation in highly supersaturated alloys and at all times in alloys in an area of low supersaturation is justified. The approximate solution to the diffusion equations correctly predicts the experimentally determined manganese concentration profiles. </p> <p> Hillert's concept of paraequilibrium has been examined and explicitly defined. The concentration given by a paraequilibrium calculation correctly predicts the experimentally observed growth rates of Kinsman and Aaronson (1967) for very highly supersaturated alloys. </p> <p> A convolution technique for use in the interpretation of strongly localized concentration changes determined by electron beam microanalysis has been developed. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.

Many buildings today primarily serve the purpose of being envelopes that separate theindoor climate from the outdoors, for a large open area. Examples of these buildings arehall buildings of different sorts. In climates where the snow load often exceeds the deadload, like in Sweden, it can be hard to construct a budget-friendly yet strong roof structurefor these halls, especially if a span above 40 m is required. One solution that has gained popularity is the tie rod truss. Oftentimes it is not a real truss,but rather a beam that is equipped with one or more tie rods and one or more compressionstruts. The struts, which connect to the tie rods that run from one end of the roof to theother, support the main beam. This way, the tie rods can decrease the moment load on thebeams by carrying a tensile force. However, this results in an increased compressive loadon the beams. The large compressive forces in conjunction with the often slender beamsections can lead to instability out of the truss plane, and ultimately collapse. This is whathappened to the sports hall Tarfalahallen in 2020 in Kiruna, Sweden. The tie rod truss is an important structure; it is relatively cheap, saves material and is strongin the truss plane. But the instability problems can deter its use. The aim of this study istherefore to explore the different factors that could influence the stability of the structureand to what extent, by studying critical loads and the utilization of all structural elements. The study was performed by analyzing a finite element model of a real tie rod truss thattoday exists in a sports hall in Sweden. The analyses were done for different values of many parameters. The results were then extracted and processed such that the critical load and the utilization were plotted against the tested parameter values. The analysis and results processing were performed in an automated process that the author created himself. The results show that the stability of the model is strongly influenced by (1) the rigidity ofthe joints between beams and struts, (2) the rigidity of the joints between beams and roofing material and (3) the vertical position of potential stabilization systems that actperpendicularly to the truss plane. Pretension of the tie rods had a large effect on themaximum utilization and how it varies along the beams. Any potential reinforcement measure must be cost-effective, and therefore should addressthe three influential properties above. One suggestion is to add sideway bracing as close tothe joints between the struts and beams as possible. / Det finns många hus idag som byggs i syfte att vara klimatskal för en stor, öppen yta. Exempel på sådana hus är hallbyggnader av olika slag. I länder som Sverige, där snölasten många gånger är större än egentyngden, kan ett billigt men hållfast tak vara svårt att konstruera för dessa hallar, särskilt om spännvidder över 40 m krävs. En lösning som blivit populär är den underspända takstolen. I princip är det ett par balkar som skarvats så att de bildar en sadeltakstol eller en lång rak balk (pulpettakstol), och som stöttas av mellanstöd och stållinor (dragband) som löper från den ena balkänden till den andra via mellanstöden. Stållinorna kan då avlasta balkarna från momentbelastning genom att bära en dragkraft. Men samtidigt ökar tryckkraften i balkarna. De stora tryckkrafterna, i samband med att balktvärsnitten ofta görs väldigt slanka, kan leda till instabilitet ut ur takstolsplanet och därmed kollaps. Detta skedde i Tarfalahallen i Kiruna år 2020. Den underspända takstolen är en viktig konstruktion eftersom den är relativt billig,materialbesparande och väldigt hållfast i takstolsplanet. Men instabilitetsfenomenen kanförhindra fortsatt användning av konstruktionen. Därför undersöks i detta arbete vilka faktorer som kan påverka instabiliteten och i vilken grad, genom att studera kritiska laster och utnyttjandegrader. Studien utfördes genom att analysera en finita elementmodell av en verklig underspändtakstol som idag finns i en svensk gymnastikhall. Analyserna gjordes för olika värden på ett stort antal parametrar. Utdata från finita elementprogrammet extraherades därefter och bearbetades så att utnyttjandegraden i alla ingående bärverkselement beräknades. Sedan plottades dessa resultat mot de olika parametervärdena som testats. Analyserna och påföljande bearbetning utfördes i en automatiserad process som författaren själv skapade. Resultaten visar att modellens stabilitet är starkt beroende av (1) styvheten i förbindelsenmellan balk och mellanstöd, (2) styvheten i förbindelsen mellan balk och sekundärbärverkoch (3) det vertikala läget av eventuella stabiliseringssystem som verkar vinkelrätt mottakstolsplanet. Förspänning av stållinorna hade en betydlig inverkan på den maximalautnyttjandegraden och hur denna varierar längs balkarna. Eventuella förstärkningsåtgärder måste vara kostnadseffektiva, och därmed måste dessagälla de tre egenskaperna ovan. En åtgärd som föreslås sidostagning så nära stöttornasinfästningar som det går.

yes / There are very few, if any, available experimental investigations on aggregate interlock capacity along diagonal cracks in lightweight concrete deep beams. As a result, the shear design provisions including the modification factor of ACI 318-08 and EC 2 for lightweight concrete continuous deep beams are generally developed and validated using normal weight simple deep beam specimens. This paper presents the testing of 12 continuous beams made of all-lightweight, sand-lightweight and normal weight concrete having maximum aggregate sizes of 4, 8, 13 and 19 mm. The load capacities of beams tested are compared with the predictions of strut-and-tie models recommended in ACI 318-08 and EC 2 provisions including the modification factor for lightweight concrete. The beam load capacity increased with the increase of maximum aggregate size, though the aggregate interlock contribution to the load capacity of lightweight concrete deep beams was less than that of normal weight concrete deep beams. It was also shown that the lightweight concrete modification factor in EC 2 is generally unconservative, while that in ACI 318-08 is conservative for all-lightweight concrete but turns to be unconservative for sand-lightweight concrete with a maximum aggregate size above 13 mm. The conservatism of the strut-and-tie models specified in ACI 318-08 and EC 2 decreased with the decrease of maximum aggregate size, and was less in lightweight concrete deep beams than in normal weight concrete deep beams.

This study proposes various methods to harvest the mechanical energy present in railcar suspensions and railroad tracks to generate electricity that is suitable for onboard or trackside electronics, using electromagnetic generators. Compact electromagnetic energy harvesters that can be installed onboard railcars or wayside on railroad tracks are designed, fabricated, and tested. The designs integrate a mechanical motion rectifier (MMR) with embedded one-way clutches in the bevel gears in order to convert the bi-directional mechanical energy that commonly exists in the form of vibrations into a unidirectional rotation of the generator. The ball screw mechanism is configured such that it has reduced backlash and thus can more efficiently harvest energy from low-amplitude vibrations. Two prototype harvesters are fabricated and tested extensively in the laboratory using a suspension dynamometer and in the field onboard a railcar and on a test track. A power management system with an energy storage circuit has also been developed for this onboard harvester. The laboratory evaluation indicate that the harvesters are capable of harvesting power with sufficient current and voltage for successfully powering light electronics or charging a low demand battery pack. The harvested power varies widely from a few to tens of Watts, depending on the resistive load across the harvester and the amplitude and frequency of the mechanical motion. The laboratory test results are verified through field testing. One harvester is tested onboard a freight railcar, placing it across the wedge suspension, to use the small amount of relative displacement at the wedge suspension to harvest energy. A second harvester is placed on a test track to use the vertical motion that occurs due to passing wheels for wayside energy harvesting. Both onboard and wayside tests confirm the laboratory test results in terms of the success of the design concept in providing low-power electrical power. The harvester design is further integrated into a conventional railroad tie for ease of field installation and for improving the efficiency of harvesting the mechanical energy at the rail. The integrated design, referred to as the "smart tie," not only protects the energy harvester, the wiring harness, and supporting electronics from the maintenance-of-the-way equipment, but also positions the harvester in a mechanically advantageous position that can maximize the track-induced motion, and hence the harvested power. Although for testing purposes, the smart tie uses a modified composite tie, it can be integrated into other track tie arrangements that are used for revenue service track, including concrete and wooden ties. A prototype smart tie is fabricated for laboratory testing, and the results nearly surpass the results obtained earlier from the wayside harvester. The smart tie is currently being considered for revenue service field testing over an extended length of time, potentially at a railroad mega site or similarly suitable location. / Doctor of Philosophy / This dissertation proposes three different electromagnetic energy harvesters for harvesting railroad track and railcar suspension vibration energy. The concept is similar to what you may have seen in self-powering flashlights that are often advertised in late-night TV commercials. You shake the flashlight vigorously, which moves an energy harvester devoice and, Voila, the light bulb comes on. The device design in this study uses the mechanical energy that is present in a vehicle or at a railroad track to harvest the mechanical energy that is naturally present in the form of electrical energy, which can then be used for powering electronic devices and sensors of various kinds. Such sensors and electronics would help with improving the operational efficiency of railroads. The energy harvesters can be installed onboard a railcar or at the track. In either case, the movement of the train creates a small amount of vibration energy that is turned into electrical power. When onboard a train the power can be used for sensors, GPS, and similar devices to allow the operator to better monitor the condition and location of the train. Note that most railcars, especially the freight railcars, do not have any onboard electrical power. Similarly, the energy harvester can be installed at the track to convert the small amount of up and down motion that happens with the passing of each wheel into energy that could be used for integration of sensors that make the track "smarter." This means that the sensors can potentially alert the engineers who are responsible for monitoring the track of an existing or impending problem with the track. Both the railcar and track integration of the energy harvester that is designed, fabricated, and tested during this study are exciting concepts that can improve the rail industry in the U.S. This document includes the details of designing efficient energy harvesters, specifically for rail applications. A prototype of the energy harvester is fabricated and tested extensively in the lab and in the field, albeit to a more limited extent. The test results were quite successful, which is why I am telling you about them! Both the laboratory and field test results show that the device holds significant promise for rail applications.

Yes / The potentially broad application area in engineering design using Genetic Al- gorithm (GA) has been widely adopted by many researchers due to its high consistency and accuracy. Presented here is the initial design of a wideband non-dispersive wire bow-tie antenna using GA for breast cancer detection applications. The ultimate goal of this design is to achieve minimal late-time ringing but at higher frequencies such as that located from 4 to 8 GHz, in which is desire to penetrate human tissue for near field imaging. Resistively loading method to reduce minimal ringing caused by the antenna internal reflections is implemented and discussed when the antenna is located in free space and surrounded by lossy medium. Results with optimised antenna geometry and di®erent number of resistive loads are presented and compared with and without existence of scatterers.