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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

KVANTIFIKACE A ZVYŠOVÁNÍ PŘESNOSTI MĚŘENÍ PRŮHYBU MOSTŮ / Quantification and improvement in bridge precision measurement deflection

Hvozdenský, Petr January 2008 (has links)
This thesis deal with improvement in bridge precision measurment deflection for Mostní a silniční Ltd. Its goal is through analysis of process of measurment and factor location, which have fundamental influence on measurment precision. First, theoretic part, represents the company, formulates problems and goals of thesis, history of bridges, world disasters, sort of bridges measurments, bridges evaluation and questions of giant transportation. In second, practical part, problems with measurment and its evaluation are described. Results are evaluated and corrective measures and recommendation are proposed in the final part.
52

Statnamic Lateral Load Testing and Analysis of a Drilled Shaft in Liquefied Sand

Bowles, Seth I. 02 December 2005 (has links) (PDF)
Three progressively larger statnamic lateral load tests were performed on a 2.59 m diameter drilled shaft foundation after the surrounding soil was liquefied using down-hole explosive charges. An attempt to develop p-y curves from strain data along the pile was made. Due to low quality and lack of strain data, p-y curves along the test shaft could not be reliably determined. Therefore, the statnamic load tests were analyzed using a ten degree-of-freedom model of the pile-soil system to determine the equivalent static load-deflection curve for each test. The equivalent static load-deflection curves had shapes very similar to that obtained from static load tests performed previously at the site. The computed damping ratio was 30%, which is within the range of values derived from the log decrement method. The computer program LPILE was then used to compute the load-deflection curves in comparison with the response from the field load tests. Analyses were performed using a variety of p-y curve shapes proposed for liquefied sand. The best agreement was obtained using the concave upward curve shapes proposed by Rollins et al. (2005) with a p-multiplier of approximately 8 to account for the increased pile diameter. P-y curves based on the undrained strength approach and the p-multiplier approach with values of 0.1 to 0.3 did not match the measured load-deflection curve over the full range of deflections. These approaches typically overestimated resistance at small deflections and underestimated the resistance at large deflections indicating that the p-y curve shapes were inappropriate. When the liquefied sand was assumed to have no resistance, the computed deflection significantly overestimated the deflections from the field tests.
53

Estimation of remaining service life of flexible pavements from surface deflections

Gedafa, Daba Shabara January 1900 (has links)
Doctor of Philosophy / Department of Civil Engineering / Mustaque A. Hossain / Remaining service life (RSL) has been defined as the anticipated number of years that a pavement will be functionally and structurally acceptable with only routine maintenance. The Kansas Department of Transportation (KDOT) has a comprehensive pavement management system, network optimization system (NOS), which uses the RSL concept. In support of NOS, annual condition surveys are conducted on the state highway system. Currently KDOT uses an empirical equation to compute RSL of flexible pavements based on surface condition and deflection from the last sensor of a falling-weight deflectometer (FWD). Due to limited resources and large size, annual network-level structural data collection at the same rate as the project level is impractical. A rolling-wheel deflectometer (RWD), which measures surface deflections at highway speed, is an alternate and fast method of pavement-deflection testing for network-level data collection. Thus, a model that can calculate RSL in terms of FWD first sensor/center deflection (the only deflection measured by RWD) is desired for NOS. In this study, RWD deflection data was collected under an 18-kip axle load at highway speed on non-Interstate highways in northeast Kansas in July 2006. FWD deflection data, collected with a Dynatest 8000 FWD on the KDOT network from 1998 to 2006, were reduced to mile-long data to match the condition survey data collected annually for NOS. Normalized and temperature-corrected FWD and RWD center deflections and corresponding effective structural numbers (SNeff) were compared. A nonlinear regression procedure in Statistical Analysis Software (SAS) and Solver in Microsoft Excel were used to develop the models in this study. Results showed that FWD and RWD center deflections and corresponding SNeff are statistically similar. Temperature-correction factors have significant influence on these variables. FWD data analysis on the study sections showed that average structural condition of pavements of the KDOT non-Interstate network did not change significantly over the last four years. Thus, network-level deflection data can be collected at four-year intervals when there is no major structural improvement. Results also showed that sigmoimal relationship exists between RSL and center deflection. Sigmoidal RSL models have very good fits and can be used to predict RSL based on center deflection from FWD or RWD. Sigmoidal equivalent fatigue crack-models have also shown good fits, but with some scatter that can be attributed to the nature and quality of the data used to develop these models. Predicted and observed equivalent transverse-crack values do not match very well, though the difference in magnitude is insignificant for all practical purposes.
54

Deflection gap study for cold‐formed steel curtain wall systems

Monroy, Barbara L. January 1900 (has links)
Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / Cold‐formed steel has become a preferred building material for wall framing in many different types of structures. One of its main uses has been as non‐structural members in curtain wall assemblies of structural steel framed buildings. In an exterior wall application, the main purpose of the curtain wall is to transfer out of plane loads to the steel frame while not supporting any superimposed gravity loads. Therefore, when the curtain wall is in the plane of the structural steel frame, the vertical deflection of the spandrel beam directly above the wall must be known to provide the appropriate deflection gap between the beam and the curtain wall so that gravity loads are not transferred to the wall. Common practice is to size the gap for the deflection from 100% of the live load. In some cases, the deflection gap may be significant, and since this gap must also be provided in the exterior cladding of the wall, it creates a design issue for the architect. This report presents the results of an investigation into the feasibility of reducing the size of the deflection gap when the wall is located directly under the spandrel beam. In this study, analytical models were developed for common design situations of curtain walls constructed of cold‐formed steel studs in structural steel framed buildings. This study investigates two common stud heights combined with different floor live loads. Taking into account that wall studs have some available axial compressive strength, a procedure was developed to determine an appropriate reduction for the gap. Using an iterative process a relationship is made between the axial compressive strength of the stud and the amount of axial load the stud can support to establish a factor which gives the percentage the live load gap for 100% live load can be safely reduced by.
55

Theoretical investigation of dielectrophoresis and electrophoresis as techniques for silver deflections

Mokgalapa, Naphtali Malesela 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The primary circuit components of very high temperature reactors (VHTRs) experience various unwanted fission products such as Kr, Xe, I, Cs, Sr, and Ag. These particle are generated during normal operation of the reactor from abaration, cracks and/or deffects are transported by the helium coolant. The main candidate that has been identified as a cause for concern and the focus of research to minimizing radioactive contamination of the reactor coolant circuit is silver. This is because the design of the coated particles limits the release of fission products into the coolant except for silver(Ag110m). Ag110m is a long lived metallic fission product formed inside the nuclear reactor core and is the only known element released out of the coated particles into the coolant at any temperature above 1150 ◦C when the reactor starts to heat up. The release occurs on intact coated particles, failed particles and also from defective particles. The amount of released silver is initially small and occurs as the pebble heats up and this is strongly dependent on the temperature of the core. It is therefore able to reach the surface of the reactor core and enter into the Helium coolant flowing throughout the reactor. Thus Ag110m will be circulated through the reactor circuit until it reaches the cooler sides of the main power system (MPS) where it will start to plate out. The presence of this radioactive silver in the primary circuit components may result in unwanted maintenance problems from a radiation hazard point of view. The development of a method to remove particles from the helium stream is therefore needed. In this work, two theoretical deflection models used to deflect the silver particles are proposed, namely the stochastic and the deterministic deflection models. The latter describes the deflection of microparticles in a helium medium. It uses the dielectrophoresis (DEP) technique to investigate the deflection of a silver µm moving in a helium medium with the bulk velocity of 0.021 ms−1 and subjected to a dielectrophoretic force only deflect an amount of 0.52039 nm and 4.49882 nm in the x - and z -directions on average. The former (stochastic deflection model) describes the deflection of ions and polarized particles by using probability theory, namely kinetic theory of gases. This model showed that the mean free time that the particle spends while deflected by a uniform electric field is short so much that there is not enough time for a silver particle to be appreciably deflected between collisions. For example, when an electric field of 100kV/m was applied on a single silver ion for a time of 0.1 µs, the deflection distance obtained was 33.38 mm for a free time of 0.189285 ns and under pressure and temperature conditions of 1 bar and 20◦ C. The Brownian motion was then compared to the effects of a nonuniform electric field in polarizing and deflecting an atom. This is done by comparing the Brownian motion and the polarizibility of an atom using nonuniform electric fields. It is found that the silver speed produced from Brownian motion (79.563 ms−1) is far larger than that produced from the polarizibility of an atom (4.69455×106 nms−1). The deterministic and stochastic deflection models using nonuniform electric fields proved that the dielectrophoresis technique is negligibly small in deflecting particles and cannot be used to deflect silver particles as required in a VHTR. / AFRIKAANSE OPSOMMING: Die primˆere siklus komponente van baie ho temperatuur reaktore (VHTRs) word bloodgestel aan verskeie ongewenste fisie produkte soos Kr, Xe, I, Cs, Sr, en Ag. Hierdie deeltjies word gegenereer gedurende normale werking van die reaktor van abarasie, krake en / of defekte word vervoer deur die helium verkoelingsmiddel. Die belangrikste kandidaat wat gedentifiseer is as ’n rede vir kommer en die fokus van navorsing op die minimalisering van radioaktiewe besoedeling van die reaktor verkoelingsmiddel siklus is silwer. Die rede hiervoor is die ontwerp van die omhulsel wat die vrylating van die fisie produkte in die koelmiddel behalwe vir silwer (Ag110m) beperk. Ag110m is ’n metaal fisie-produk met ’n lang leeftyd wat gevorm word binne-in die kern van die reaktor en is sover bekend die enigste element wat vrygestel word deur die bedekte deeltjies in die verkoelingsmiddel by enige temperatuur bo 1150 ◦C wanneer die reaktor begin verhit. Die vrystelling kom voor by ongeskonde brandstofomhulse, nie funksionele deeltjies en ook van gebrekkige deeltjies. Die bedrag van vrygestel silwer is aanvanklik klein en kom voor as die brandstofelemente verhit en heirdie vrystelling is sterk afhanklik van die temperatuur van die kern. Dit is dus in staat om die oppervlak van die reaktor kern te bereik en betree die Helium verkoelingsmiddel vloeistelsel en beweeg regdeur die reaktor. Dus sirkuleer die Ag110m deur die reaktor kring totdat dit die koeler kante van die MPS bereik waar dit sal begin uitplatteer. Die teenwoordigheid van hierdie radioaktiewe silwer in die primˆere stroombaan komponente kan lei tot ongewenste onderhoud probleme van ’n straling gevaar oogpunt. Die ontwikkeling van ’n metode om deeltjies te verwyder uit die helium stroom is dus nodig. In hierdie werk word van twee teoretiese defleksie modelle gebruik gemaak om die silwer partikels se defleksie te beskryf, naamlik die stogastiese en die deterministiese defleksie modelle. Laasgenoemde beskryf die defleksie van mikro grootte partikel in ’n helium medium. Dit maak gebruik van die dielektroflorosensie (DEP) tegniek om ondersoek in te stel na die defleksie van ’n silwer deeltjie met ’n radius van 3 μm. Dit is vanaf hierdie model waargeneemdat ’n silwer mikrodeeltjie met ’n radius van 3 m in ’n helium medium beweeg met die snelheid van 0,021 ms−1 en onderworpe is aan ’n dielektroforetiese krag dit net met ’n gemiddelde van 0,52039 nm en 4,49882 nm in die x - en z -rigtings deflekteer. Die voormalige (stogastiese defleksie model) beskryf die defleksie van ione en gepolariseerde partikels deur gebruik te maak van waarskynlikheidsteorie, naamlik die kinetiese teorie van gasse. Hierdie model toon dat die gemiddelde vrye tyd wat die deeltjie spandeer terwyl dit gedeflekteer word deur ’n uniforme elektriese veld sovel korter is dat daar nie genoeg tyd is vir ’n silwer deeltjie is om aansienlik tussen botsings gedeflekteer kan word nie. Byvoorbeeld, wanneer ’n elektriese veld van 100kV/m toegepas word op ’n enkele silwer ioon vir ’n tyd van 0.1 μs, die defleksie afstand van 33,38 mm verkry word vir ’n vrye tyd van 0.189285 ns en onder druk en temperatuur voorwaardes van 1 bar en 20 ◦C. Die Brown-beweging was dan vergeleke met die uitkoms van n univorme elektriese veld wat n polariserende atoom deflekteer. Dit word gedoen deur die vergelykings van die Brown-beweging en die polariseerbaarheid van ’n atoom met behulp van nie-uniform elektriese veld te gebruik. Daar word gevind dat as die silwer spoed van Brown se beweging (79,563 ms−1) veel groter is as di van die polariseerbare atoom (4,69455 × 10−6 nms−1). Die deterministiese en stogastiese defleksie modelle deur gebruik te maak van nonuniform elektriese velde bewys dat dielectrophoresis tegniek is weglaatbaar klein in defleksie van deeltjies en kan dus nie gebruik word om silwer partikels te buig soos wat in ’n VHTR vereis word nie.
56

Exploring the Scalability and Performance of Networks-on-Chip with Deflection Routing in 3D Many-core Architecture

Weldezion, Awet Yemane January 2016 (has links)
Three-Dimensional (3D) integration of circuits based on die and wafer stacking using through-silicon-via is a critical technology in enabling "more-than-Moore", i.e. functional integration of devices beyond pure scaling ("more Moore"). In particular, the scaling from multi-core to many-core architecture is an excellent candidate for such integration. 3D systems design follows is a challenging and a complex design process involving integration of heterogeneous technologies. It is also expensive to prototype because the 3D industrial ecosystem is not yet complete and ready for low-cost mass production. Networks-on-Chip (NoCs) efficiently facilitates the communication of massively integrated cores on 3D many-core architecture. In this thesis scalability and performance issues of NoCs are explored in terms of architecture, organization and functionality of many-core systems. First, we evaluate on-chip network performance in massively integrated many-core architecture when network size grows. We propose link and channel models to analyze the network traffic and hence the performance. We develop a NoC simulation framework to evaluate the performance of a deflection routing network as the architecture scales up to 1000 cores. We propose and perform comparative analysis of 3D processor-memory model configurations in scalable many-core architectures. Second, we investigate how the deflection routing NoCs can be designed to maximize the benefit of the fast TSVs through clock pumping techniques. We propose multi-rate models for inter-layer communication. We quantify the performance benefit through cycle-accurate simulations for various configurations of 3D architectures. Finally, the complexity of massively integrated many-core architecture by itself brings a multitude of design challenges such as high-cost of prototyping, increasing complexity of the technology, irregularity of the communication network, and lack of reliable simulation models. We formulate a zero-load average distance model that accurately predicts the performance of deflection routing networks in the absence of data flow by capturing the average distance of a packet with spatial and temporal probability distributions of traffic. The thesis research goals are to explore the design space of vertical integration for many-core applications, and to provide solutions to 3D technology challenges through architectural innovations. We believe the research findings presented in the thesis work contribute in addressing few of the many challenges to the field of combined research in many-core architectural design and 3D integration technology. / <p>QC 20151221</p>
57

Box Beam / Box Beam

Lai, Jackie, Huynh, Johnny January 2016 (has links)
This report covers the product development process of a C-profile forming a box beam for use in storage systems. The company Brännehylte Lagersystem AB is in need of a new box beam that in pair can handle a maximum load of 4000 kg (four pallets x 1000 kg). At present the company has only one beam capable of a maximum load of 4x800 kg and wants to expand its product range and develop as a company and compete with others in the storage systems market. The first step began with acquiring information on the different beams and how they behave under stress. Then began a combination of brainstorming and brainwriting to generate a number of concepts of how a C-profile could possibly look like. After screening of the different concepts using Gut-feeling method three most appropriate concepts were left and were pitted against each other in a Pugh Matrix to get the best possible C-profile for further development. Calculations and tests were done on the selected concept with a combination of elementary cases and SolidWorks. For the beam to be approved it must meet the EU standard for storage racks. The calculated beam resulted in a working beam in theory, which in turn must be produced to confirm that the theory is true. Because a prototype must be produced in order to confirm the results, then the work cannot be proven in practical example and only be proven in theory.
58

Numerical Computation of Transient Response of 2D Wedge Impact

Koyyapu, Naresh Kumar 16 December 2016 (has links)
The diverse applications of advanced marine craft ascribed to their high speed and technological advancements has led to the use of stronger and lighter metals in such crafts. High speed, in effect also increases slamming loads as higher speed increases frequency of wave encounter while operating in waves. The present study is limited to wedge impact models. Fundamentally, the study is thus about two-dimensional (2D) wedge impact in water. In an attempt to predict the structural response to impact hydrodynamic force, a beam element based finite element (FE) computer program is written and the results of the code are presented in the thesis. A computational tool is developed to predict the transient elastic response of a 2D wedge under impact force using two different numerical methods. Both explicit and implicit numerical schemes have also been studied in order to apply to the present work. Explicit forth order Runge-Kutta (RK4) method and implicit Newmark-b (NB) method have been used in the present work. Coupling effects between excitation and response are ignored in the present numerical computations. Both the numerical schemes are validated using simple static solution and also modal expansion technique.
59

Elektronenstrahlschmelzen – ein pulverbettbasiertes additives Fertigungsverfahren

Klöden, Burghardt, Kirchner, Alexander, Weißgärber, Thomas, Kieback, Bernd, Schöne, Christine, Stelzer, Ralph, Süß, Michael 10 December 2016 (has links) (PDF)
Aus der Einleitung: "Das selektive Elektronenstrahlschmelzen (engl. Electron Beam Melting (EBM®)) ist ein pulverbettbasiertes additives Fertigungsverfahren, mit dessen Hilfe metallische Bauteile schichtweise hergestellt werden können. Der schematische Aufbau einer entsprechenden Anlage ist in Abbildung 4 dargestellt. Dabei erfolgt die Strahlerzeugung im Bereich 1 (die Kathode besteht entweder aus Wolfram oder bei den neuesten Systemen aus einkristallinem LaB6). Die Strahlablenkung durch ein elektromagnetisches Linsensystem erfolgt im Bereich 2. Der Bereich 3 ist die eigentliche Baukammer, in der sich unter anderem die Vorratsbehälter für das Pulver, das Rakelsystem sowie die Komponenten des Bauraums (Käfig mit Hitzeschild, Bauplattform mit Startplatte) befinden. ..."
60

Flexural behaviour of continuously supported FRP reinforced concrete beams

Habeeb, M. N. January 2011 (has links)
This thesis has investigated the application of CFRP and GFRP bars as longitudinal reinforcement for continuously supported concrete beams. Two series of simply and continuously supported CFRP and GFRP reinforced concrete beams were tested in flexure. In addition, a continuously supported steel reinforced concrete beam was tested for comparison purposes. The FRP reinforced concrete continuous beams were reinforced in a way to accomplish three possible reinforcement combinations at the top and bottom layers of such continuous beams. The experimental results revealed that over-reinforcing the bottom layer of either the simply or continuously supported FRP beams is a key factor in controlling the width and propagation of cracks, enhancing the load capacity, and reducing the deflection of such beams. However, continuous concrete beams reinforced with CFRP bars exhibited a remarkable wide crack over the middle support that significantly influenced their behaviour. The ACI 440.1R-06 equations have been validated against experimental results of beams tested. Comparisons between experimental results and those obtained from simplified methods proposed by the ACI 440 Committee show that ACI 440.1R-06 equations can reasonably predict the load capacity and deflection of the simply and continuously supported GFRP reinforced concrete beams tested. However, The potential capabilities of these equations for predicting the load capacity and deflection of continuous CFRP reinforced concrete beams have, however, been adversely affected by the de-bonding of top CFRP bars from concrete. An analytical technique, which presents an iterative procedure based on satisfying force equilibrium and deformation compatibility conditions, has been introduced in this research. This technique developed a computer program to investigate flexural behaviour in particular the flexural strength and deflection of simple and continuously supported FRP reinforced concrete beams. The analytical modelling program has been compared against different prediction methods, namely ACI 440, the bilinear method, mean moment inertia method and Benmokrane's method. This comparison revealed the reliability of this programme in producing more enhanced results in predicting the behaviour of the FRP reinforced beams more than the above stated methods.

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