Дисертації з теми "Curved joints"
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1
Wells, Zane B. "Performance of Post-Tensioned Curved-Strand Connections in Transverse Joints of Precast Bridge Decks." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1222.
Анотація:
Accelerated Bridge Construction (ABC) techniques have resulted in innovative options that save time and money during the construction of bridges. One such group of techniques that has generated considerable interest is the usage of individual precast concrete members. Utilizing precast concrete decks allows for offsite curing, thus eliminating long delays due to formwork and concrete curing time. These precast concrete decks have inherent joints between the individual panels. These joints are locations for potential leakage, which can lead to corrosion or inadequate long-term performance. Post-tensioning the precast deck panels helps to eliminate leakage; however, conventional longitudinal post-tensioning systems require complete deck replacement in the event of a single faulty deck panel. A proposed post-tensioned, curved-strand connection allows for a single panel to be replaced. The capacity of the proposed curved-strand connection was investigated in order to compare its behavior to other systems that are currently in use. Tests were performed in composite negative bending, beam shear, and positive bending. The curved strand connection was found to behave similarly to the standard post-tensioning system in positive bending and shear. The curved-strand connection was found to be comparable to a standard post-tensioning system. The ultimate capacity of the curved-strand connection in negative bending was found to be 97% of the standard post-tensioning. Pre-stress losses were measured and predicted for the service life of the connection and were found to be 6% at the 75- year service life of a bridge.
2
Salam, Claro Diego. "Wave-based numerical approaches for non-destructive testing of structural assemblies involving straight waveguides and curved joints." Electronic Thesis or Diss., Bourges, INSA Centre Val de Loire, 2024. http://www.theses.fr/2024ISAB0003.
Анотація:
Cette thèse étudie la détection et la localisation des défauts dans les assemblages de guides d'ondes, en explorant l'interaction entre les ondes se propageant dans des assemblages de guides d'ondes droits contenant des jonctions coudées et des défauts. A cet effet, la méthode Wave Finite Element (WFE) est utilisée. Des expériences numériques valident la robustesse et la précision de la méthode WFE à partir de comparaisons avec des solutions analytiques et éléments finis, en se concentrant particulièrement sur les courbes de dispersion et les réponses forcées. En élargissant l'étude aux assemblages comportant des éléments de couplage, tels que des joints et des défauts, l'étude met en évidence l'efficacité de la méthode WFE dans des scénarios impliquant de tels assemblages. Une nouvelle stratégie utilisant un formalisme en matrices de diffusion est proposée pour la localisation des défauts, qui met l'accent sur les structures contenant des jonctions coudées. L'approche repose sur le calcul du temps de vol de paquets d'ondes transmis ou réfléchis au niveau d'un élément de couplage. La stratégie est validée par des simulations numériques, démontrant la précision de la localisation des défauts pour divers scénarios, notamment des poutres 2D en contraintes planes et des tuyaux avec une jonction coudée et un défaut. Les structures élasto-acoustiques sont également traitées. Une stratégie de réduction basée sur la méthode de Craig-Brampton avec des vecteurs d'enrichissement est proposée pour améliorer le coût de calcul de la modélisation des éléments de couplage. L'analyse des coefficients de transmission et de réflexion en puissance des ondes dans des structures présentant des défauts et des jonctions met en évidence la pertinence du mode de torsion dans les contrôles non destructifs par ondes guidées dans ce type de système. Ces travaux de recherche contribuent non seulement à la compréhension de la propagation des ondes dans les assemblages de guides d'ondes, mais proposent également des stratégies pratiques pour une détection et une localisation précise des défauts, avec des applications potentielles dans divers contextes d'ingénierieThis thesis investigates defect detection and localization within waveguide assemblies, exploring the interaction between waves in straight waveguides with curved joints and defects. For this purpose, the Wave Finite Element (WFE) method is used. Numerical experiments validate the robustness and accuracy of the WFE method through comparisons with analytical and Finite Element solutions, particularly focusing on dispersion curves and forced responses. Extending the investigation to assemblies with coupling elements, such as joints and defects, the study highlights the efficiency of the WFE method in scenarios involving waveguides.A novel strategy is proposed within the scattering matrix formalism for defect localization, with a specific emphasis on structures containing curved joints. The approach relies on computing the time of flight of narrow wavepackets transmitted or reflected at a coupling element. The strategy is validated through numerical simulations, showcasing precision in defect localization for diverse scenarios, including 2D plane-stress beams and pipes, with a curved joint and a defect.Elasto-acoustic structures are also treated. A reduction strategy based on Craig-Brampton reduction with enrichment vectors is proposed for computational efficiency to model coupling elements. Analysis of power transmission and reflection of waves in structures with defects and joints highlights the significance of the torsional mode in guided wave-based non-destructive testing in this type of system.This research work contributes not only to the understanding of wave propagation in waveguide assemblies but also offers practical strategies for accurate defect detection and localization, with potential applications in diverse engineering contexts
3
Madireddy, Sandeep Reddy. "Finite Element Modeling of Transverse Post-Tensioned Joints in Accelerated Bridge Construction." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1302.
Анотація:
The Accelerated bridge construction (ABC) techniques are gaining popularity among the departments of transportation (DOTs) due to their reductions of on-site construction time and traffic delays. One ABC technique that utilizes precast deck panels has demonstrated some advantages over normal cast-in-place construction, but has also demonstrated some serviceability issues such as cracks and water leakage to the transverse joints. Some of these problems are addressed by applying longitudinal prestressing. This thesis evaluates the service and ultimate capacities in both flexure and shear, of the finite element models of the post-tensioned system currently used by Utah Department of Transportation (UDOT) and a proposed curved-bolt system to confirm the experimental results. The panels were built and tested under negative moment in order to investigate a known problem, namely, tension in the deck concrete. Shear tests were performed on specimens with geometry designed to investigate the effects of high shear across the joint. The curved-bolt connection not only provides the necessary compressive stress across the transverse joint but also makes future replacement of a single deck panel possible without replacing the entire deck. Load-deflection, shear-deflection curves were obtained using the experimental tests and were used to compare with the values obtained from finite element analysis. In flexure, the ultimate load predicted by the finite element model was lower than the experimental ultimate load by 1% for the post-tensioned connection and 3% for the curved-bolt connection. The shear models predicted the ultimate shear reached, within 5% of the experimental values. The cracking pattern also matched closely. The yield and cracking moment of the curved-bolt connection predicted by the finite element model were lower by 13% and 2%, respectively, compared to the post-tensioned connection in flexure.
4
Kalpathy, Venkiteswaran Venkatasubramanian. "Development of a Design Framework for Compliant Mechanisms using Pseudo-Rigid-Body Models." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1482232749828813.
5
Coates, Cameron Wayne. "New concepts for strength enhancement of co-cured composite single lap joints." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12937.
6
Chmielowiec, Mark 1955. "MOMENT ROTATION CURVES FOR PARTIALLY RESTRAINED STEEL CONNECTIONS." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276452.
Анотація:
Tension and Compression force deformation data from laboratory tests of angle segments are used to generate moment rotation curves for the following bolted partially restrained connections: (1) top and seat angle, (2) double web angle, and (3) top and seat angle with double web angles. The force deformation and moment rotation curves are analytically described by a four parameter formula which provides the basis for the analytical connection model. These connection models consist of rigid bars and nonlinear springs representing the angle segments in either tension or compression. Design curves giving the four parameters of the moment rotation curves are generated for the double web angle connection. These parameters are primarily a function of the angle thickness, gage length of the angle legs in flexture, and the number of bolts in the connection. Comparisons of derived moment rotation curves are made with published results of full scale tests.
7
Cao, Caihua. "Damage and Failure Analysis of Co-Cured Fiber-Reinforced Composite Joints." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5298.
Анотація:
Joints represent a design challenge, especially for composite structures. Among the available joining methods, co-curing is an efficient way to integrate parts for some applications. Coates and Armanios have proposed a Single Nested Overlap (SNO) co-cured joint configuration, obtained from a single lap joint through the overlap/interleafing of the adjoining top/bottom adherend plies, respectively. Through a comparative investigation, they have demonstrated joint strength and fatigue life improvements over the single lap joint counterparts for unidirectional and quasi-isotropic adherend lay-ups. This research extends the comparative investigation of Coates and Armanios by focusing upon characterizing and differentiating the damage initiation and progression mechanisms under quasi-static loading. Six specimen configurations are manufactured and tested. It is confirmed that single nested overlap joints show 29.2% and 27.4% average improvement in strength over single lap counterparts for zero-degree unidirectional and quasi-isotropic lay-ups, respectively.
Several nondestructive evaluation techniques are used to observe and analyze damage initiation, damage progression and failure modes of the studied specimens and to monitor their mechanical response. Using X-ray Radiography and Optical Microscopy techniques during quasi-static loading, a physical characterization of damage and failure mechanisms is obtained. The acoustic emission data acquired during monotonic loading could reveal the overall picture of AE activities produced by the damage initiation, development and accumulation mechanisms within the specimen via parametric analysis. Further AE analysis by a selected supervised clustering method is carried out and shown successful in differentiating and clustering the AE data. Correlation with physical observations from other techniques suggests that the resulting clusters may be associated to specific damage modes and failure mechanisms.
8
Abul-Hamayel, Ismat A. A. 1960. "MOMENT ROTATION CURVES FOR TOP AND SEAT CONNECTIONS (STATIC LOADING, TENSION)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/291311.
9
Iliopoulou, Marina. "Discrete analogues of Kakeya problems." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8068.
Анотація:
This thesis investigates two problems that are discrete analogues of two harmonic analytic problems which lie in the heart of research in the field. More specifically, we consider discrete analogues of the maximal Kakeya operator conjecture and of the recently solved endpoint multilinear Kakeya problem, by effectively shrinking the tubes involved in these problems to lines, thus giving rise to the problems of counting joints and multijoints with multiplicities. In fact, we effectively show that, in R3, what we expect to hold due to the maximal Kakeya operator conjecture, as well as what we know in the continuous case due to the endpoint multilinear Kakeya theorem by Guth, still hold in the discrete case. In particular, let L be a collection of L lines in R3 and J the set of joints formed by L, that is, the set of points each of which lies in at least three non-coplanar lines of L. It is known that |J| = O(L3/2) ( first proved by Guth and Katz). For each joint x ∈ J, let the multiplicity N(x) of x be the number of triples of non-coplanar lines through x. We prove here that X x2J N(x)1=2 = O(L3=2); while we also extend this result to real algebraic curves in R3 of uniformly bounded degree, as well as to curves in R3 parametrized by real univariate polynomials of uniformly bounded degree. The multijoints problem is a variant of the joints problem, involving three finite collections of lines in R3; a multijoint formed by them is a point that lies in (at least) three non-coplanar lines, one from each collection. We finally present some results regarding the joints problem in different field settings and higher dimensions.
10
Tan, Xinyuan. "Co-cured composite joint strength investigation based on behavior characterization of [0/±θ/90]s family". Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26578.
Анотація:
Joints provide a path for transfer of load and are important components in an assembly of structures, particularly in translating joint strength improvements directly to significant cost savings. This cost savings is more evident in composite joints since manufacturing of more complex single piece components results in a reduction of both part count and labor. An improvement in joint strength for co-cured composite joints through minimized free-edge delamination was investigated for quasi-isotropic [0/±45/90]s lay-up based on the quantitative assessments of the quasi-static and fatigue strength and qualitative understanding of the fatigue damage initiation and propagation for the [0/±θ/90]s family of co-cured composite joints. A previously proposed co-cured joint concept, the Single Nested Overlap (SNO) joint, was compared against a Straight Laminate (SL) and a single lap joint. The SL represents a "perfect" joint and serves as an upper bound whereas the single lap joint represents the simplest generic joint and is the base design for the SNO joint concept. Three categorized failure types, which represented predominant failure modes in the SL, single lap and SNO joints, along with two different fatigue strength indicators were used for quasi-static and fatigue strength comparison. With fatigue run-out defined at 1 x 106 cycles, the fatigue damage initiation and propagation at high loadings was monitored with an Infrared Thermoelastic Stress Analysis (IR-TSA) technique, while a damage type comparison was used at low loadings. Quasi-static Acoustic Emission (AE) counts were observed to be Fatigue Limit (FL) predictors for [0/±θ/90]s SL and SNO joints. The validity of these FL predictors were also assessed in the damage type comparison.
11
Ullah, Irfan. "Caracterização da subsuperfície rasa através da curva da razão espectral H/V e da inversão conjunta das curvas de dispersão e elipticidade." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/14/14132/tde-04062018-101840/.
Анотація:
A destruição causada por um terremoto depende de muitos fatores, como características e profundidade da fonte, magnitude, distância epicentral e da configuração geológica da área. A destruição causada devido à configuração geológica da área é denominada como efeito local. A modelagem do efeito local implica na determinação do tempo e nível de vibração e do efeito de amplificação do deslocamento. As propriedades elásticas dos materiais geológicos (velocidade das ondas de compressão e de cisalhamento, densidade, espessura da camada de solo, etc.) podem ser obtidas por diversos métodos geofísicos. O conhecimento dessas propriedades elásticas ajuda a melhor projetar as infraestruturas e reduzir as chances de danos. Este procedimento é denominado de microzoneamento. Os parâmetros mais importantes para realizar o microzoneamento são as espessuras dos sedimentos que recobrem o embasamento e o perfil das velocidades das ondas S (cisalhamento). Esses dois parâmetros são adequadamente caracterizados pelo uso de várias técnicas geofísicas como perfilagens em furos de sondagem, reflexão e refração sísmica. Esses métodos geofísicos trazem algumas restrições como a necessidade da execução de um furo, emprego de fontes sísmicas artificiais que muitas vezes são dispendiosas e por vezes de uso restrito em áreas urbanas, além de muitas vezes estarem limitadas a investigações de apenas algumas dezenas de metros. Os métodos que substituíram esses métodos geofísicos convencionais nas últimas décadas são a análise do ruído sísmico produzido por fontes naturais e culturais. Este ruído sísmico ambiental pode ser registrado com menor custo e esforço e com boa cobertura lateral. Várias técnicas que se utilizam do ruído sísmico podem ser empregadas, no entanto, aquela que obteve maior atenção nos últimos anos é a técnica da razão do espectro horizontal sobre o espectro vertical da onda de superfície (H/V). A curva da razão espectral H/V é uma ferramenta rápida, fácil e de baixo custo para a caracterização da subsuperfície rasa. Existem vários estudos realizados sobre o tema que tentaram cobrir todos os aspectos e problemas associados ao método. Aqui neste estudo são aprofundados alguns aspectos ainda não avaliados em detalhe. Diferentes procedimentos para a modelagem e as associações entre os fenômenos físicos envolvidos e as características da curva H/V são discutidos e os resultados numéricos desses estudos são comparados com informações extraídas de perfis de sondagens de um dos locais estudados. O pico e a forma da curva H / V são modelados para encontrar o desvio na frequência de pico a partir da frequência de ressonância da onda de cisalhamento considerando diferentes campos de onda em torno do pico, assim como sua relação com a forma dominante da curva. A frequência de pico das curvas H/V é utilizada para estimar a relação entre a frequência a espessura através de análise de regressão. O estudo mostra que a curva de dispersão obtida a partir de um ensaio MASW pode ser usada para estimar a velocidade da onda S a um metro de profundidade e sua tendência de aumento com a profundidade. Esses valores podem ser usados para estimar a relação frequência-espessura para uma área. Esses resultados são comparados com a relação frequência-espessura derivada experimentalmente para a mesma área. A sensibilidade da forma da curva H/V à estrutura de velocidade do meio é analisada através de duas técnicas de modelagem (elipticidade da onda Rayleigh e campo difuso baseado na curva H/V). Diferentes partes da curva H/V são invertidas visando avaliar qual a parte da curva H/V contém as informações mais importantes sobre a estrutura subterrânea. As lições aprendidas dessas análises são aplicadas a três dados experimentais de locais distintos. As ondas Love podem contaminar o resultado da curva H/V. Duas técnicas diferentes para remover o efeito das ondas amorosas são discutidas. Em seguida, são discutidos os resultados da inversão conjunta das curvas de dispersão e da curva H/V após remoção do efeito da onda Love, ou seja, a curva de elipticidade. Alguns aspectos novos da técnica H/V são discutidos no final.The destruction caused by an earthquake at a site depends on many factors like source characteristics such as magnitude, epicentral distance from the site, depth of the source, and on the geological setting of the area. The destruction caused due to the geological setting of an area is termed as site effect. To model the site effect of an area is to determine the shaking level longevity and its displacement amplification. The elastic properties (shear and compressional wave velocities, density, thickness of soil layer, etc.) of the site are required to find out by employing various geophysical procedures. The knowledge of these elastic properties help in better designing the infrastructure, which reduces the chances of destruction caused by a local geological setting due to an earthquake occurrence. This procedure is widely termed as microzonation. The most important parameters for the microzonation are the thickness of soft sediments over the seismic bedrock and its shear wave velocity profile. These two parameters are properly characterized by employing various geophysical techniques like borehole measurement, seismic reflection and seismic refraction. The conventional geophysical methods bring some hindrance to the picture such as, the drilling of a borehole and artificial seismic sources deployment for the reflection and refraction survey, which are both expensive and time consuming, difficult or even in some case impossible to implement in urbanized environment, the investigation is depth limited to few tens of meter. The methods which replaced this conventional geophysical method from the last decades or so is the analysis of Earth vibration caused by the seismic noise which is produced by both natural and cultural sources. This ambient seismic noise can be recorded with less cost and effort with good lateral coverage. Various seismic noise techniques are employed for this job; however, the one which got the most attention in recent years is the horizontal over vertical spectral ratio (H/V) technique. The H/V spectral ratio curve is a fast easy and cheap tool for the near-subsurface characterization. There are various study performed on the topic which has tried to cover almost all the aspects and problems associated with the method. Here in this study, we try to detail the aspects of this technique, which are not been evaluated fully. The different modelling procedures presented to model and physically link the H/V curve with some physical phenomenon will be discussed and its numerical result with the experimental H/V curve will be compared for a borehole test site. The peak and the shape of the H/V curve will be modelled to find its peak frequency deviation from the shear wave resonance frequency by considering different wave-field around the peak. Similarly, the shape dominancy of the H/V curve linkage will be find out. The peak frequency of the H/V curve is used to estimate the thickness-frequency relation by regression analysis. Here we will show that the dispersion curve obtained from multi-channel analysis of surface waves (MASW) can be used to estimate the velocity at one meter and the shear wave velocity increase trend with depth. These values can be used to estimate the thickness frequency relation for an area and its result will be compared with the experimentally derived thickness-frequency relationship for the same area. The sensitivity of the H/V curve shape to the subsurface velocity structure will find out for two main modelling techniques (Rayleigh wave ellipticity and diffused field based H/V curve). The different parts of the H/V curve are inverted (back modelled) to find out the part of H/V curve which is carrying the most important information about the subsurface structure. The lesson learned from all this analysis will be applied to experimental data of three different sites. The Love waves might contaminate the result of the H/V curve. Two different techniques to remove their effects will be discussed. Then, the joint inversion result of the dispersion and this Love effect removed H/V for more precisely ellipticity curve is discussed. Some new aspects of the H/V curve technique are also discussed at the end.
12
Chafi, Haysam. "Optimisation des efforts dans un ancrage courbe collé acier/composites." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1221/document.
Анотація:
Les matériaux composites connaissent un intérêt croissant dans la majorité des secteurs de l’industrie en raison de leur faible poids propre et de leurs propriétés physico-chimiques intéressantes. Cependant, l’utilisation de ces matériaux a nécessité de conduire en parallèle des réflexions sur leur assemblage avec d’autres matériaux qui a donné naissance au développement de la technologie d’assemblage par collage structural. Cette technique qui permet de pouvoir assembler des matériaux de nature différente en limitant par exemple l’augmentation du poids propre de la structure n’est pas encore totalement maîtrisée. Pour cela, des développements sur la qualification des efforts d’adhésion ou sur la compréhension de la durabilité sont encore nécessaires. Cette thèse aborde la problématique de l’optimisation des assemblages collés et vise en particulier à étudier de manière plus précise l’utilisation de la courbure afin d’optimiser le transfert des efforts au sein du joint de colle. Deux types de colle, présentant l’une un comportement élastique fragile et l’autre un comportement élastoplastique ont été étudiés dans ce travail sur les différents volets analytique, numérique, et, expérimental. Il s’est avéré que la plasticité de l’adhésif semble améliorer la capacité de résistance du joint collé et sera alors un paramètre essentiel dans leur optimisation. Une étude de la géométrie courbe des joints collés acier/composite a été ensuite menée et il ressort de cette étude que cette géométrie est efficace pour augmenter la résistance d'un joint collé à la rupture. De plus, afin d’approfondir les connaissances sur le comportement mécanique du joint collé courbe, et en absence d’étude bibliographique suffisante sur ce type de collage, nous avons ensuite eu recours à la modélisation par la méthode des zones cohésives pour pouvoir aussi valider l’atout de la géométrie courbe par rapport à la géométrie plane. Ce travail s’est enfin intéressé à la durabilité mécanique de cette solution en abordant la thématique de la fatigue ; même si des investigations supplémentaires seront nécessaires, nous avons d’ores et déjà constaté que l’optimisation du joint par l’utilisation d’une colle élastoplastique et une géométrie courbe permet d’améliorer le comportement en fatigue de l’assemblage colléComposite materials are gaining increasing interest in most of the industry sectors due to their low self-weight and their interesting physico-chemical properties. However, the use of these materials called for parallel reflections on their assembly with other materials which gave rise to the development of the structural bonding technology. This technique which allows to assemble materials of different natures by limiting, for example, the increase in the self-weight of the structure, is not fully mastered yet. For this purpose, further development on the qualification of the adhesion forces or on the understanding of durability are still necessary. This thesis addresses the problem of the optimization of adhesive bonded joints and aims in particular to study, more precisely, the use of the curvature in order to optimize the transfer of forces within the bonded joint. Two types of adhesive, one exhibiting a fragile elastic behavior and the other an elastoplastic behavior, have been studied in this work on the various analytical, numerical, and experimental aspects. We presumed that the plasticity of the adhesive appears to improve the strength of the bonded joints and; hence, shall be considered as an essential parameter in their optimization. A study of the curved geometry of the steel / composite bonded joints was then carried out, where it emerged that this geometry was effective in increasing the strength of the bonded joint and its ultimate capacity. Moreover, in order to extend the knowledge on the mechanical behavior of the curved bonded joints, and in the absence of sufficient bibliographical references on this type of bonding, we then resorted to the modeling by using the cohesive zone method to also validate the advantage of the curved geometry with respect to the plane geometry. This work finally focuses on the mechanical durability of this solution by addressing the fatigue thematic; even if additional investigations are needed, we have already found that the optimization of the joint by the use of an elastoplastic adhesive, and a curved geometry can improve the fatigue behavior of the adhesive bonded joints
13
Hsia, Wei-Kung 1958. "DOUBLE ANGLE CONNECTION MOMENTS (RICHARD EQUATION, PRYING FORCE, BEAM-LINE THEORY, MOMENT ROTATION CURVE)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/291892.
14
Špačková, Eva. "Multifunkční objekt v Českých Budějovicích." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240487.
Анотація:
The subject of this thesis is the design and assessment of the supporting structure multifunctional building in the Czech Budejovice . The construction of a sphere with a maximum diameter of 30 m and a height of 19.5 meters the highest point . The supporting structure consists of curved ribs , elevator shaft and ceiling beams . The structure is designed in 4 versions . Two variants are made of steel, the third option is wooden and the latest version solves a combination of wood and steel. In the variant selected is done loading , ultimate limit state, serviceability limit state , fire resistance and compounds selected details.
15
Raigoza, Jaime Antonio. "Temporal Join Processing with Hilbert Curve Space Mapping." NSUWorks, 2013. http://nsuworks.nova.edu/gscis_etd/280.
Анотація:
Management of data with a time dimension increases the overhead of storage and query processing in large database applications especially with the join operation, which is a commonly used and expensive relational operator whose processing is dependent on the size of the input relations. An index-based approach has been shown to improve the processing of a join operation, which in turn, improves the performance of querying historical data. Temporal data consist of tuples associated with a time interval value having a valid life span of different lengths. With join processing on temporal data, since tuples with longer life spans tend to overlap a greater number of joining tuples, they are likely to be accessed more often. The efficient performance of a temporal join depending on index-clustered data is the main theme studied and researched in this work. The presence of intervals having an extended data range in temporal data makes the join evaluation harder because temporal data are intrinsically multidimensional.
Some temporal join processing methods create duplicates of tuples with long life spans to achieve clustering of similar data, which improves the performance on tuples that tend to be accessed more frequently. The proposed Hilbert-Temporal Join (Hilbert-TJ) join algorithm overcomes the need of data duplication by mapping temporal data into Hilbert curve space that is inherently clustered, thus allowing for fast retrieval and storage. A balanced B+ tree index structure was implemented to manage and query the data. The query method identifies data pages containing matching tuples that intersect a multidimensional region. Given that data pages consist of contiguously mapped points on the curve, the query process successively traverses along the curve to determine the next page that intersects the query region by iteratively partitioning the data space. The proposed Adaptive Replacement Cache-Temporal Data (ARC-TD) buffer replacement policy is built upon the Adaptive Replacement Cache (ARC) policy by favoring the cache retention of data pages in proportion to the average life span of the tuples in the buffer. By giving preference to tuples having long life spans, a higher cache hit ratio was evident. The caching priority is also balanced between recently and frequently accessed data.
An evaluation and comparison study of the proposed Hilbert-TJ algorithm determined the relative performance with respect to a nested-loop join, a sort-merge join, and a partition-based join algorithm that use a multiversion B+ tree (MVBT) index. The metrics are based on a comparison between the processing time (disk I/O time plus CPU time), cache hit ratio, and index storage size needed to perform the temporal join. The study was conducted with comparisons in terms of the Least Recently Used (LRU), Least Frequently Used (LFU), ARC, and the new ARC-TD buffer replacement policy. Under the given conditions, the expected outcome was that by reducing data redundancy and considering the longevity of frequently accessed temporal data, better performance was achieved. Additionally, the Hilbert-TJ algorithm offers support to both valid-time and transaction-time data.
16
Panneerselvam, Ashok. "A Joint Model of Longitudinal Data and Time to Event Data with Cured Fraction." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1278619003.
17
Olsson, Emma. "Method development for fatigue lifeprediction in welded gearset joints undertorsional loading." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-86879.
Анотація:
This report presents the degree project for a master's degree in Mechanical Engineeringat Luleå University of Technology performed by Emma Olsson at GKN ePowertrain in Köping. The aim of the thesis was to develop a calculation method to evaluate fatigue ina weld due to torsion. During the degree project, two di erent calculation methods weredeveloped - An analytical method and a numerical method. The analytical method is based on a calculation method already used at GKN for calculatingfatigue due to rotary bending, but with the adaptations required for when the weld issubjected to torsion. For this method, Wöhler's curve, Goodman and Gerber mean stresscorrection and Palmgren-Miner's rule have been used. The numerical method was performed in the commercial software FEMFAT, which hasbeen developed to calculate, among other things, fatigue and safety factors. This is asimulation program the company in question has, but previously not used for this purpose. During the process of developing these calculation methods, areas such as mean stresscorrection, fatigue strength and weld classi cation have been studied, and appropriatesettings for the simulation.This resulted in two calculation methods whose results differ greatly from each other.The analytical method is a very conservative method in which the fatigue damage that iscalculated becomes very high and according to the damage value the weld will fail. Forthe numerical method, on the other hand, the fatigue is very low and, according to thedamage value, will not fail. Based on this, it can be stated that the numerical method is the method considered mostreliable and should be further investigated and nally used. However, it is not possible togive a precis conclusion of whether the methods correspond to the reality, since no physicaltesting have been performed.
18
Shrestha, Alina. "Fatigue Testing and Data Analysis of Welded Steel Cruciform Joints." ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1670.
Анотація:
In this study, ABS Publication 115, “Guidance on Fatigue Assessment of Offshore Structures” is briefly reviewed. Emphasis is on the S-N curves based fatigue assessment approach of non-tubular joints, and both size and environment effects are also considered. Further, fatigue tests are performed to study the fatigue strength of load-carrying and non-load-carrying steel cruciform joints that represent typical joint types in marine structures. The experimental results are then compared against ABS fatigue assessment methods, based on nominal stress approach, which demonstrates a need for better fatigue evaluation parameter. A good fatigue parameter by definition should be consistent and should correlate the S-N data well. The equivalent structural stress parameter is introduced to investigate the fatigue behavior of welded joints using the traction based structural stress approach on finite element models of specimens, and representing the data as a single Master S-N curve.
19
Ahmed, Abubaker Ali Tan Tein-Min. "Initiation and growth of multiple-site damage in the riveted lap joint of a curved stiffened fuselage panel : an experimental and analytical study /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1560.
20
Lourens, Spencer. "Bias in mixtures of normal distributions and joint modeling of longitudinal and time-to-event data with monotonic change curves." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1685.
Анотація:
Estimating parameters in a mixture of normal distributions dates back to the 19th century when Pearson originally considered data of crabs from the Bay of Naples. Since then, many real world applications of mixtures have led to various proposed methods for studying similar problems. Among them, maximum likelihood estimation (MLE) and the continuous empirical characteristic function (CECF) methods have drawn the most attention. However, the performance of these competing estimation methods has not been thoroughly studied in the literature and conclusions have not been consistent in published research. In this article, we review this classical problem with a focus on estimation bias. An extensive simulation study is conducted to compare the estimation bias between the MLE and CECF methods over a wide range of disparity values. We use the overlapping coefficient (OVL) to measure the amount of disparity, and provide a practical guideline for estimation quality in mixtures of normal distributions. Application to an ongoing multi-site Huntington disease study is illustrated for ascertaining cognitive biomarkers of disease progression.
We also study joint modeling of longitudinal and time-to-event data and discuss pattern-mixture and selection models, but focus on shared parameter models, which utilize unobserved random effects in order to "join" a marginal longitudinal data model and marginal survival model in order to assess an internal time-dependent covariate's effect on time-to-event. The marginal models used in the analysis are the Cox Proportional Hazards model and the Linear Mixed model, and both of these models are covered in some detail before defining joints models and describing the estimation process. Joint modeling provides a modeling framework which accounts for correlation between the longitudinal data and the time-to-event data, while also accounting for measurement error in the longitudinal process, which previous methods failed to do. Since it has been shown that bias is incurred, and this bias is proportional to the amount of measurement error, utilizing a joint modeling approach is preferred. Our setting is also complicated by monotone degeneration of the internal covariate considered, and so a joint model which utilizes monotone B-Splines to recover the longitudinal trajectory and a Cox Proportional Hazards (CPH) model for the time-to-event data is proposed. The monotonicity constraints are satisfied via the Projected Newton Raphson Algorithm as described by Cheng et al., 2012, with the baseline hazard profiled out of the $Q$ function in each M-step of the Expectation Maximization (EM) algorithm used for optimizing the observed likelihood. This method is applied to assess Total Motor Score's (TMS) ability to predict Huntington Disease motor diagnosis in the Biological Predictors of Huntington's Disease study (PREDICT-HD) data.
21
Varadarajan, Ravikumar. "On the Nature of Static and Cyclic Fracture Resistance of Ultra High Molecular Weight Polyethylenes Used in Total Joint Replacements." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1164903681.
22
Zugna, Daniela. "Theoretical and applied issues arising from the joint modelling of longitudinal response processes and time to competing events." Doctoral thesis, Università degli studi di Padova, 2008. http://hdl.handle.net/11577/3425521.
Анотація:
The statistical analysis of observational data arising from HIV/AIDS research is generally faced with complexities that arise from both the longitudinal and survival features of the data.This thesis proposes a methodology for modelling the joint variation over time of the two main biomarkers of the progression of disease and of the survival processes of a set of competing events.
Modelling two longitudinal response processes as a bivariate linear mixed effects model, with knots at relevant times, will account for the dependence between two biomarkers by random effects while overcoming the problem of irregularly measured data and of the possible measurement errors. Furthermore modelling the informative withdrawals from the study as dependent competing risks, by estimating the
so called cumulative incidence functions whithin a proportional hazards model, will allow for an unbiased estimate of the markers' processes. At the same time the parameters that specify the association between the markers processes and the survival processes will allow to model the effect of the biomarkers, adjusted for other covariates, on the competing events. The essential feature of joint modelling is that
the parameters which describe the longitudinal response processes and those which describe the failure risks, as a function of the longitudinal processes, are estimated
simultaneously, making a more efficient use of data.
23
Lozano, Minguez Estivaliz. "Fatigue and fracture mechanics of offshore wind turbine support structures." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9756.
Анотація:
Wind power, especially offshore, is considered to be one of the most promising sources of ‘clean’ energy towards meeting the EU targets for 2020 and 2050. However, its popularity has always fluctuated with the price of fossil fuels since nowadays wind electricity production cannot compete with nuclear or coal electricity production. Support structures are thought to be one of the main drivers for reducing costs in order to make the wind industry more economically efficient. Foundations and towers should be fit for purpose, extending their effective service life but avoiding costs of oversizing. An exhaustive review of the background and state of the art of the Fatigue-Life assessment approaches has been carried out, combining analysis of the gathered experimental data and the development of Finite Element models based on contemporary 3D solid models with diverse Regression Analyses, in order to identify their weakness and evaluate their accuracy. This research shows that the guides and practices currently employed in the design and during the operation of the offshore wind turbine support structures are obsolete and not useful for optimisation, which generally leads to conservationism and an unnecessary increase in costs. The basis for a comprehensive update of the Girth Weld and Tubular Joint S-N curves and the Stress Concentration Factors of Tubular Joints has been set out. Furthermore, a reliable methodology for deriving the Stress Intensity Factor at the deepest point of a semi-elliptical surface saddle crack in a tubular welded T-joint has been proposed.
24
Haag, Jefferson. "Influência da geometria do corpo de prova e do tamanho de trinca na tenacidade à fratura do aço API 5DP tool joint." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/116623.
Анотація:
Ensaios de mecânica da fratura utilizando corpos de prova padronizados apresentam alto nível de restrição à deformação plástica na ponta da trinca, devido a esforços de flexão e a trincas profundas. Em decorrência do emprego desses corpos de prova, há um alto conservadorismo nos resultados obtidos por esses ensaios, quando aplicados em materiais de boa tenacidade. Aplicações cujos defeitos estão submetidos a baixos níveis de constricção e a pequenas margens de segurança fazem com que sejam necessários corpos de prova mais próximos do estado de tensão submetido pela estrutura para realizar adequadamente a análise crítica de engenharia (Engineering Critical Analysis - ECA). Este trabalho visa analisar a influência da geometria de corpos de prova e do tamanho da trinca na tenacidade à fratura do aço API 5DP Tool Joint. Este estudo constitui-se da realização de ensaios de tenacidade à fratura com duas geometrias de corpos de prova (SE(B) e SE(T)) e quatro tamanhos de trinca normalizados (a0/W = 0,40; 0,50; 0,60; e 0,70) com a técnica da flexibilidade no descarregamento (unloading compliance). Foi utilizado o projeto de experimentos (DOE) para obter resultados referentes aos efeitos principais dos dois fatores e de suas interações. Foram calculadas, a partir de triplicatas para cada condição, curvas de resistência e valores únicos de tenacidade à fratura (Integral J e CTOD), sendo que o último foi utilizado para o cálculo da análise de variância (ANOVA). Com base nos resultados obtidos, conclui-se que a geometria de corpo de prova, tamanho da trinca e a interação entre os dois fatores possuem efeito significativo sobre as variáveis resposta (CTOD e Integral J) com nível de significância de 5%. Além disso, obtiveram-se os valores de JIC e δi através das curvas de resistência, mostrando que esses valores independem da geometria e do tamanho da trinca.Fracture mechanics testing using standardized specimens have a high level of restriction to plastic deformation at the crack tip, due the bending stresses and deep crack lengths. Due to the use of these specimens geometry, there is a high conservatism on the obtained results of fracture toughness testing when applied on high toughness materials. The application of specimens closely modeling to the actual stress conditions in the component under consideration are necessary to evaluate structures containing defects with low levels of constraint and small safety margins to perform appropriately the engineering critical analysis (ECA). This work aims to analyze the influence of specimen geometry and crack length on the fracture toughness of API 5DP Tool Joint steel. This study consists in the execution of fracture toughness testing on two specimen geometries (SE(B) e SE(T)) and four normalized crack lengths (a0/W = 0,40; 0,50; 0,60; and 0,70) with the unloading compliance method. Design of experiments (DOE) was applied to obtain results regarding to the main factors effects and their interactions. From triplicates of each condition, resistance curves and unique values of fracture toughness (J integral and CTOD) were calculated, and the latter result was used to calculate the analysis of variance (ANOVA). The obtained outcomes show that the specimen geometry, crack length and the interaction between these factors have significant effect on the response variables (CTOD and J integral) on a significance level of 5%. In addition, there were obtained the values of JIC e δi through the resistance curves, showing that these values do not depend on the geometry and crack length.
25
Nusia, Jiota. "Evaluation of Knee Ligament Injuries in Occupants of Heavy Goods Vehicles by Simulating Frontal Impacts using THUMS HBM." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-262667.
Анотація:
INTRODUCTION. Frontal collisions have been observed to cause the severe injuries on heavy goods vehicle occupants, and the lower extremities have been frequently injured. Injuries of knee joints are rarely life threatening, however they tend to give long-term consequences. AIM. Evaluate non-lethal frontal impacts towards the knee joint of Total Human Model for Safety (THUMS) v4.0 using a cylindrical barrier. The main objectives are to 1) create local injury risk functions of the knee ligaments restraining frontal impacts, 2) simulate frontal impacts towards the knee joints of THUMS and3) prepare the Hybrid III (HIII)-model for corresponding frontal impacts conducted on THUMS. The intention is for future HIII-simulations to be cross-correlated with the responses from THUMS for the ability to estimate knee ligament strains by investigating impacts on HIII. METHODS. 1) Ligament risk curves of PCL, MCL and LCL were formulated by assembling mean strain threshold values and standard deviations from literature. Virtual values were generated from these pooled strain thresholds, creating the risk curves. 2) THUMS lower body was impacted by a cylindrical steel barrier at four different locations - middle of patella, middle of knee joint, upper tibia and below tibia tuberositas. Four impact velocities ranging from 8-14 km/h were used at each location, giving a total of 16 impacts. 3) The HIII-model was prepared by removing the upper body and inserting the cylindrical steel barrier into the model file. RESULTS. The strain threshold at 50% rupture risk for PCL resulted in 23.6±4.4%, 34.2±6.0% for MCL and 26.6±6.5% for LCL. The simulated THUMS PCL strains reached between 36%-58% for the highest velocity at the impact locations where tibia was involved. Both MCL and LCL gave an approximate 5% strain outcome. The resultant knee displacement for these impacts ranged between 22 mm - 32 mm. The knee displacements at the PCL strain threshold ranged between 14 mm - 16 mm. DISCUSSION and CONCLUSION. Most of the maximal PCL strains exceeded the PCL threshold with large margins. However, the knee displacement at the PCL strain threshold resulted in outcomes comparable to the thresholds used for HIIImodel. These results supported the obtained PCL threshold to be within a reasonable range.
26
Jatheeshan, Varathananthan. "Numerical and experimental studies of cold-formed steel floor systems made of hollow flange section joists in fire." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/120145/1/Varathananthan_Jatheeshan_Thesis.pdf.
Анотація:
The cold-formed steel utilization in buildings has increased globally due to its higher strength to weight ratio, ease of transportation and rapid erection and dismantlement.
However, cold-formed steel buildings must be designed with adequate Fire Resistance Ratings (FRR). Hence cold-formed Light gauge Steel Frames (LSF) are assembled using channel sections and lined with fire resistive plasterboards to provide load-bearing wall and floor systems. There is an industry need to develop LSF floor systems with improved FRR. Adding multiple layers of plasterboard to increase the FRR of LSF floor systems is not an efficient method. Past research has focused on investigating the behaviour of LSF floor systems made of Lipped Channel Section (LCS) joists. No attempt has been made to use an improved joist section in LSF floor systems. The Hollow Flange Sections (HFS) with torsionally rigid hollow flanges and no free edges have higher local and lateral distortional buckling capacities than the conventional LCSs. This research focuses on investigating the structural and fire performance of LSF floor systems made of HFS joists with a goal to improve their FRRs.
Four full scale standard fire tests were undertaken on non-insulated dual and single plasterboard lined LSF floor panels and cavity insulated dual plasterboard lined floor panel made of welded HFS joists known as LiteSteel beams (LSB). Fire tests of these panels undertaken for varying load ratios provided valuable results, which included failure times, joist temperatures and modes, and deflection versus time curves. The floor panels failed due to the section failures of joists. Both non-insulated and cavity insulated LSF floors made of LSB joists showed a significant improvement in the FRRs in comparison to Baleshan's (2012) results for LSF floors made of LCS joists.
Another experimental study was undertaken to determine the elevated temperature mechanical properties of the steel used in LSB web and flange elements. The mechanical property reduction variation of LSB steel elements was found to be quite different to that of normal cold-formed steels and was even dissimilar amongst them.
The yield strength reduction factors of Eurocode 3 Part 1.2 (ECS, 2005) were proposed for the web elements since they closely followed them whereas a new yield strength reduction factor model was proposed for the flange elements. An identical variation was proposed for the elastic modulus reduction factors of both web and flange elements. Suitable modifications were made to Dolamune Kankanamge and Mahendran's (2011) stress-strain model for improved predictions of LSB web and flange elements' stress-strain curves.
A Finite Element (FE) model of an individual simply supported LSB joist was developed and validated using the cold-formed steel design standards and Anapayan et al.'s (2011b) section moment capacity test results. By using the accurate mechanical property reduction factors of LSB steel elements, the FE model was then extended to simulate the full scale fire tests. Finite element analyses (FEA) showed reasonably good agreements in terms of failure times, temperatures and modes, and the mid-span deflection versus time curves. Such good agreements verified the accuracy of the developed FE model to simulate the LSF floor panels made of HFS joists under fire conditions.
Thermal FE models of LSF floor systems made of HFS joists were then developed and the time-temperature profiles were compared with the fire test results. They showed better agreements for Tests 1 and 4 whereas there were some discrepancies for Tests 2 and 3. Thermal FEA results obtained using appropriate thermal properties of plywood showed a reasonably good agreement with Baleshan's (2012) fire test results. Parametric studies using the validated model showed that joist section depth and profile had no significant impact on the thermal performance of LSF floor systems whereas steel joist thickness had a significant influence.
An extensive FEA based parametric study was then undertaken to investigate the effects of joist thickness, depth, section profile, steel grade and mechanical property reduction factors, and web openings on the structural and fire performances (FRR) of LSF floor systems. Steel joist thickness significantly influenced the FRR of LSF floor systems due to different temperature developments in the steels for varying thicknesses. Joist section depth, section profile and web openings had no significant impact on the FRRs of LSF floor systems. Steel type affected the FRRs of LSF floor systems significantly due to different mechanical property reduction factors, especially different yield strength reduction factors. It was shown that Baleshan's (2012) critical average joist temperature method can be used to determine the FRR of non-insulated dual and single plasterboard lined floor panels made of HFS joists.
However, it can be used for cavity insulated floor panels when the load ratio is less than 0.3. Fire test and FEA results showed that LSF floor panels made of LSB joists gave higher FRRs due to improved elevated temperature mechanical properties of LSB plate elements and lower temperature development due to thicker joists.
Fire design rules were developed to predict the FRRs of LSF floor systems made of HFS joists based on Eurocode 3 Part 1.3 (ECS, 2006), AS/NZS 4600 (SA, 2005) and Direct Strength Method (DSM). For this purpose, Baleshan's (2012) three fire design rules of LCS joists were used and suitable modifications were made in order to use them for HFS joists. A good agreement was observed between the FRR predictions using two design methods and FEA, and thus they were recommended. In addition, the FRR predictions of HFS joists using the fire design method developed based on DSM were modestly conservative and therefore they were also recommended.
Finally, the spread sheet based design tool was developed to undertake the complex calculations in predicting the FRR of LSF floors made of HFS joists with varying sizes and steel types, and subjected to varying load ratios.
In summary, this research has significantly improved the knowledge and understanding of the fire performance of LSF floor systems made of hollow flange section joists and developed accurate fire design rules. Structural and fire design engineers can use the developed spread sheet based design tool to predict the fire performance of LSF floor systems made of HFS joists with varying sizes and steel types for a range of applications in commercial and residential buildings.
27
Volejník, Petr. "Lávka pro pěší." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240233.
Анотація:
The theme of this thesis is the design and assessment of the supporting structure of a footbridge over the river Svratka in Brno. Span bridge is 40 meters and width of 4.2 meters. The bridge is located in the administrative area Brno - Bystrc.
28
Junková, Karolina. "Jezdecká hala v Českém Těšíně." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240357.
Анотація:
The subject of my diploma thesis is to design timber and steel variants of riding hall. For static assessment was chosen timber. The hall is a one nave building. The dimensions of ground plans is 35,0 m x 75,0 m and the hall is 11.70 meters high. The load-bearing was formed by a curved glue laminated timber trusses. The building is located in Český Těšín, climate loads are designed for the area. The calculation were made in accordance with the Czech technical norms ČSN EN.
29
Ryšánek, Michal. "Posouzení životnosti svařované žebrované hřídele generátoru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231103.
Анотація:
This master thesis deals primarily with the prediction of fatigue life of welded ribbed shaft. Recommendations taken from the International Institute of Welding (IIW) are used to express the stress values and the fatigue life. The stress values of examined place are expressed by approach of nominal stress, structural hot spot stress and effective notch stress. Results from stress-strain analysis are combined together with fatigue strength curves for prediction of the fatigue life. At the end of the analysis, the predicted fatigue life is compared with design life of welded ribbed shaft.
30
Kuchař, Martin. "Stanovení modulu pružnosti zdiva ve směru ložné spáry." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227159.
Анотація:
The determination of strain properties of masonry in the direction parallel to bed joints is a fundamental pre-requisite for designing structures, where masonry is subjected to horizontal stresses (e. g. strengthening with prestressing). The diploma thesis summarized techniques of determination of masonry modulus of elasticity presented in available literature. The goal is to suggest suitable methodology of determination of masonry modulus in direction parallel to the bed joints. In the practical part of the diploma thesis is that methodology verified by experimental test and results of tests are analyzed and discussed.
31
Drexler, Martin. "Lávka pro pěší." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226916.
Анотація:
This thesis deals with the design and assessment of the wooden footbridge. The structure is designed for the locality of the village Loučná nad Desnou acrros the river Desná. Span of the footbridge is 30m, and the width is 4m. The footbridge is covered with a saddle roof. The main supporting elements are two triple joint arcs with intermediate bridge deck. The bridge deck is made of two main beams and nine cross members, with always two longitudinal members in between them. Roofing is of nine cross-bindings, which are connected by purlins and top purlin. The stability of the whole structure is stiffened by the horizontal longitudinal stiffeners in the top and bottom surface and vertical longitudinal stiffener in the roof. The main load-bearing elements are made of glued laminated timber, the other elements are made of solid timber. Stiffeners are made of steel rods.
32
Grussmann, Jan. "Lávka pro pěší." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227762.
Анотація:
Master´s thesis deals with design and complex static assessment of timber roofed footbridge structural system. The calculation part is divided into three main chapters, that are dedicated to determine load impacts on structure, to particular structural and roof members assessment and also to design details of connections. The lower part of structure is formed by flat arched main beams of glued laminated timber, floor beams, stringers and under-deck bracing. The upper part of footbridge is formed by structure of gabled roof and additional bracings. Transversal frames of footbridge copy the shape of arch and they are arranged orthogonally to its axis. They form a radial fan with commom centre in the longitudinal direction. The static scheme of structure is thought as a statically undefinite system thanks to the bedrock surrounding the footbridge.
33
Kuchtová, Ludmila. "Pavilon v botanické zahradě v Jihlavě." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409838.
Анотація:
The aim of this diploma thesis is to design a load-bearing structure of the botanical pavillion in Jihlava. The construction is designed as a variable structure of both steel and timber. Each solution has a different type of ribs. The layout is a hexadecagon with maximum dimension of 30 meters. The height of the building is considered to be 10 meters.
34
Heinrich, Stefan. "Modulbasierte Synthese ebener Koppelgetriebe unter Einbeziehung kinetischer Kenngrößen." Universitätsverlag Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A31872.
Анотація:
Die Entwicklung mechanischer Antriebskonzepte für nichtlineare Bewegungsaufgaben stellt bis heute ein komplexes und domänenübergreifendes Fachgebiet des Maschinenbaus dar. Auf dem Gebiet der ebenen Koppelgetriebe gibt es dabei seit vielen Jahren Versuche, die optimale Lösung für eine Aufgabe unter Berücksichtigung kinetischer Kenngrößen zu finden. Die vorliegende Arbeit stellt eine Methodik vor, die sowohl den klassischen Verfahren der Getriebetechnik als auch den Ansätzen der Mechanik zum Ausgleich der Massenwirkungen im Getriebe gerecht wird. Der entwickelte Ansatz des modulbasierten Analyse-Synthese-Parameter-Abgleiches (ASPA) erlaubt erstmals eine domänenübergreifende Simulation komplexer Antriebskonzepte auf Basis einer neuartigen modularen Synthesebibliothek. Diese lässt sich dank umfangreicher Dokumentation und der dargestellten Programmablaufpläne in beliebige Software implementieren. Die exemplarisch im Systemsimulator SimulationX implementierte Bibliothek ermöglicht somit unter anderem die Anwendung der klassischen Drei- und Vierlagensynthese im bewegten oder ruhenden Bezugssystem für Dreh- und Schubgelenkketten. Neben der Ausgabe gerundeter Getriebeabmessungen eröffnet der beschriebene Ansatz somit die Berücksichtigung kinetischer Kenngrößen wie den Pendelschwingungen in spielbehafteten Gelenken oder der Änderung der Trägheitskenngrößen während der Synthese. Weiterführend kann eine multikriterielle Optimierung der noch freien Syntheseparameter erfolgen.Developing nonlinear transmitting planar coupler linkages represents a domain spanning area in mechanical engineering. In recent years many efforts have been made to determine the optimal planar linkage regarding kinetic characteristics. This thesis introduces a method linking classical synthesis procedures with mechanical approaches for a dynamically balanced mechanism. For the first time, the module based analysis-synthesis-parameter-adjustment (ASPA) allows for a domain spanning simulation of complex drive assemblies based on a novel modular synthesis library. Due to an extensive documentation and detailed program flow charts it is possible to implement the library in arbitrary software environments. The exemplarily implemented library in SimulationX allows to apply the classical three- and four-position synthesis within a steady or moving reference frame of revolute or prismatic joint chains. Further, the modules return rounded link dimensions. By applying this library according to ASPA it is now possible to account for kinetic boundaries such as pendulum oscillations of joints with joint clearance or the change of mass properties during the position synthesis. Thus, a multi-criteria optimization of the remaining free synthesis parameters can be applied.
35
Zaghlool, Baher SalahElDeen Othman Ahmed. "Behaviour of three-dimensional concrete structures under concurrent orthogonal seismic excitations." Thesis, University of Canterbury. Civil Engineering, 2007. http://hdl.handle.net/10092/1177.
Анотація:
This thesis is a study into the response and seismic safety of three-dimensional multi-storey concrete structures under concurrent orthogonal seismic excitations. It employs the nonlinear time-history method as its analysis tools. Time-history analyses rely heavily on their utilised earthquake records. Accordingly, this study examines the different approaches of selecting earthquake suites and develops a methodology of selecting representative earthquake scenarios. This methodology is credibly implemented in selecting a far- and a near field suites representative of the New Zealand seismic hazard. The study investigates the response of 6-, 9- and 12-storey concrete structures of different n-X-bays × m-Y-bays. Bidirectional responses of these considered structures are examined and consequently the current combination rules are scrutinised. Consequently this study strongly recommends the use of the 40-percent combination rule in lieu of the widely used 30-percent rule; and the use of time-history analysis in lieu of quasi/equivalent static and response modal analysis methods to avoid their strong dependence on combination rules. An intensive study is conducted employing the incremental dynamic analysis (IDA) technique to investigate structural demands of interstorey drifts, lateral storey drifts and storey accelerations. The study utilises the developed far-field suite and identifies the 50th and 90th percentile demands. Hence it provides easy-to-use expressions to facilitate rapid calculation of the structural demands and the effects of biaxial interactions. An implementation into the Demand and Capacity Factor Design (DCFD) format is presented that infers confidence in the performance levels of the considered structures. The study also draws attention to the importance of considering storey accelerations as their storey values reach as high as 10 × PGA. A sensitivity study is conducted by repeating the IDA investigation while using the developed near-field suite. Subsequently a comparison between the near- and the far-field results is conducted. The results were markedly similar albeit of less magnitudes until the (seismic hazard) intensity measure IM = Sa(T₁) = 0.4g when the near-field results show sudden flat large increase in demands suggesting a brittle collapse. This is attributed to the higher content of the higher mode frequencies contained in near-field ground motions. Finally, the study examines the (vectorial) radial horizontal shear demands in columns and beam-column joints of the previous far- and near-field studies. The combined radial shear demands in corner, edge and internal columns and joints are evaluated that roughly show a square-root proportional relationship with IM that exhibit somewhat brittle failure at IM ≥ 0.35g. Shears demands in the (4-way) internal columns and the (2-way) corner joints show highest magnitude in their respective class. The results suggest transverse joint shear reinforcement of 1.5, 1.0 and 0.5 of the longitudinal reinforcement of the neighbouring beam respectively for corner, edge and internal joints. An implementation of a proposed practical (and simpler) DCFD format shows satisfactory confidence in columns performance in shear up to IM = 0.35g, conversely to joints unsatisfactory performance in shear at the onset of inelastic behaviour (IM > 0.05g).
36
Pei-ChenTsai and 蔡沛辰. "A Development and Application of Joints for Curved Wood Box Beams." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/26246394045051806543.
Анотація:
碩士國立成功大學
建築學系
102
Due to many benefits of woods, timber buildings are comfortable to dwell. More and more architects choose this material for design nowadays. To pursuit the potential of timbers, this thesis tried to design a wooden construction from structure system called the curved grid system. The thesis discussed the mechanical behavior of grid system, and then extended to wood curved grid system. It developed modularized joints which contain two parts: 1. Vault Joint (one direction curved) 2. Hyperbolic-Paraboloid Joint (Two direction curved). The purpose of these two developments is to create three-D freeform wood structure. In the case of vault joint, it could play the role of a roof structure or any other system shaped with one direction curved. To discuss the feasibility of vault joint, the thesis operated a design case, the assembly hall of Bei-Dou junior high school, and examined the mechanical behavior of it. In the case of hyperbolic-paraboloid joint, it could be the structure of 3D curved shape like a covering. In this case, it also operated a design case, the roof facility of Huei-Lai relic exhibition, and examined the mechanical behavior. For the practical development and application, in this thesis, there are several subjects related to the joint construction detail. Laboratory test still needs to be further investigated. Key words: Timber, Curved Grid System, Freeform. INTRODUCTION There are many timber buildings constructed by wood grid system, some of them are 3D curved grid. In those wood curved grid cases, they always need higher technology and lots of customized elements. For the purpose of popularity, it focused on how to make the system more simple and common. The thesis tried to design wood curved grid system with modularized joints to improve those problems. It developed one-direction curved system with the same members and connections consequently, and developed two-direction curved system focused on how to connect wood members with rotatable mechanism. As the same reason, modularized concept was required. To investigate the feasibility, the structural analysis calculated the fundamental stress and strain, then designed the dimensions of members by SAP 2000. In the case of vault joint, member’s section was 14x45 centimeters square using bolts to connect each wood member. In the case of hyperbolic-paraboloid joint, member’s section was also 14x45 centimeters square using drift-pins to connect each wood member. Due to the modularized concept, there were only two dimensions of length. After the design of joints, the thesis operated a reality case application of them. 1. The assembly hall of Bei-Dou junior high school 2. The roof facility of Huei-Lai relic exhibition MATERIALS AND METHODS The procedure of the thesis is assisted by the Rhinoceros 5 for 3D modeling, SAP 2000 for structural analysis, and 3D printer for reality modeling. 1.Rhinoceros 5: building a virtual model on the computer is convenience to image the mechanism and find out the problems quickly. 2.SAP 2000: It shows the structural details concluding dimensions, loadings, and the result of structural analysis. They are helpful to revise the design easily. 3.Makerbot Replicator 2X: the machine is lent by Architecture Department of National Cheng Kung University. The reality model is helpful to evaluate the feasibility.
37
(9524555), Hwa-Ching Wang. "Behavior and Design of Concrete Frame Corners: Strut-and-Tie Method Approach." Thesis, 2020.
Анотація:
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.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.
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.
38
Henriques, José Alexandre Gouveia. "Behaviour of joints : simple and efficient steel-to-concrete joints." Doctoral thesis, 2013. http://hdl.handle.net/10316/24515.
Анотація:
Tese de doutoramento do Programa Doutoral em Construção Metálica e Mista, apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraA utilização de sistemas estruturais combinando elementos de diferente natureza, como seja paredes de betão armado com vigas e pilares metálicos ou mistos, apresenta-se como uma solução competitiva onde se retira partido da eficiência estrutural de cada tipo de elemento. Este tipo de solução requer ao projectista um conhecimento multidisciplinar onde o principal obstáculo reside na ligação entre os elementos de diferente natureza como são as ligações parede de betão armado com viga metálica/mista. Neste tipo de ligação, a principal problemática reside na ausência de configurações e modelos simplificados para dimensionamento que facilitem a avaliação das suas propriedades e a sua realização. Ao longo das últimas décadas, o desenvolvimento do método das componentes permitiu demonstrar a eficiência da metodologia na avaliação do comportamento de ligações metálicas e mistas. Consequentemente, a sua extensão a ligações estruturais aço-betão revela-se conveniente e requer a integração de “novas” componentes associadas aos modos de ruptura que despontam no elemento de betão armado. Assim, torna-se necessário a caracterização e inclusão destas componentes nos modelos globais de avaliação do comportamento da ligação. Foi com o intuito de responder a esta problemática que se desenrolou um projecto Europeu de investigação (RFCS). Neste, estudaram-se várias configurações de forma a responder às diferentes exigências estruturais. Do envolvimento do autor no projecto, desenvolveu-se a presente tese. O seu principal objectivo é a abordagem transversal às ligações estruturais aço-betão, utilizando uma configuração desenvolvida no projecto. Na versão “mais completa”, a configuração seleccionada permite realizar uma ligação entre viga mista e parede de betão armado, conferindo continuidade parcial ou total (ligação semi-continua/continua). Contudo, a flexibilidade da configuração permite a adaptação para soluções com diferentes exigências estruturais, ou seja, ligação rotulada. Na presente tese efectua-se uma abordagem sequencial, evoluindo da configuração mais simples para a mais completa, com caracterização numérica e analítica de componentes e ligações. A validação experimental é feita sempre que possível com a contribuição da literatura e dos resultados da campanha experimental do referido projecto. Assim, propõese modelos numéricos e analíticos que permitem avaliar o comportamento de uma ligação entre viga mista e parede de betão armado independentemente da idealização estrutural pretendida: rotulada, semi-continua ou continua. Por fim, é efectuado um estudo simplificado ao nível do comportamento estrutural global onde se pretende investigar as exigências estruturais a que estão submetidas as ligações estudadas. A análise considera um conjunto de pórticos planos (solução mista aço-betão) onde se incorpora o comportamento das ligações e se extraem os requisitos para diferentes estados limites.
The use of the structural systems combining members of different nature, such as reinforced concrete walls with steel/composite beams and columns, presents a competitive solution benefiting from the structural efficiency of each type of member. This type of solution requires to the designer multidisciplinary knowledge where the main obstacle lies in the joints between members of different nature, as are the reinforced concrete wall to steel/composite beam joints. In such joints, the main problem is the lack of solutions for easy execution and simplified models for evaluation of their properties. Over the past decades, the development of the component method has demonstrated the effectiveness of the methodology in assessing the behaviour of steel and composite joints. Consequently, its extension to structural steel-concrete joints is convenient and requires the integration of "new" components associated with the failures modes that develop in the reinforced concrete member. Thus, it becomes necessary to characterize and to include these components in global models for evaluation of the joint behaviour. Aiming at the study of steel-to-concrete joints, the RFCS project entitled "New market chances for steel structures by innovative fastening solutions" was developed. In the project, three joint configurations were investigated for different structural requirements. The present thesis is also the outcome of the author’s involvement in this project. Its main objective is a transversal approach to structural steel-to-concrete joints using a configuration developed within the referred project. In its “complete” version, the joint configuration provides a semi-continuous/continuous solution to connect a composite beam to a reinforced concrete wall. Though, the adaptability of the configuration allows its modification to perform under different structural requirements, as pinned joint. In this thesis a sequential approach is carried out, evolving from the simplest configuration to the “most complete”, with numerical and analytical characterization of the components, connections and joints. The experimental validation is performed whenever possible with the contribution of the results available in the literature and produced in the experimental campaign of the referred project. Thus, analytical and numerical models are proposed for characterization of the behaviour of joints between composite beam and reinforced concrete wall independently of the structural idealization: pinned, semi-continuous and continuous. Finally, at the structural level, a simplified study is performed to investigate the performance requirements of the steel-to-concrete joints. The analysis considers the structural calculation of three portal frames (mixed steel-concrete solution) which incorporate the behaviour of joints. The structural requirements for the different limit states are extracted and compared with the properties of the approached joints.
39
SADLER, ERIN. "PRINCIPAL COMPONENT ANALYSES OF JOINT ANGLE CURVES TO EXAMINE LIFTING TECHNIQUE." Thesis, 2010. http://hdl.handle.net/1974/5976.
Анотація:
The objectives of the present body of work were 1) to evaluate the Personal Lift-Assist Device (PLAD) in terms of its effect on lifting technique, interjoint coordination, and whether sex modulates these effects and 2) to explore the use of principal component analysis (PCA) as a method to investigate lifting waveforms. Thirty participants (15M, 15F) completed a freestyle, symmetrical lifting protocol during which three-dimensional kinematics of the ankle, knee, hip, and lumbar and thoracic spine were collected using a two-camera Optotrak 3020 system. There were four testing conditions: a) with and b) without wearing the PLAD; and c) 0% load and d) 10% of maximum back strength load. All data were evaluated using PCA. In the first analysis, the relationship between the PLAD and lifting technique under a loaded condition was explored. Results showed that 8 PCs were significantly different between the PLAD/No PLAD conditions yet there were no significant effects of sex on any of the PCs. It was concluded that wearing the PLAD encourages a lifting technique that is reflective of a squat lift, independent of sex. In the second analysis, the PLAD’s effect on interjoint coordination patterns under both loaded and unloaded conditions was examined using the relative phase angle (RPA). It was found that there were no significant differences between device, sex, or load conditions on any of the PCs retained in the model. A novel approach to enhance interpretability of PCs was developed during this study. Finally, when the PLAD was not worn, male and female differences were further investigated under loaded and unloaded conditions. It was determined that when the load is individualized to personal strength characteristics, sex differences in lifting technique are negligible. This is a contradictory finding from previous research. Overall, the major contributions of this research are: support for the use of the PLAD in industry; the recommendation that load be selected based on individual strength characteristics for lifting research experimental design; the use of PCA as a method to effectively evaluate lifting waveforms; and the development of a novel approach to aid in the interpretation of principal components.Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2010-08-18 09:35:19.142
40
du, Tertre Antonin. "Nondestructive Evaluation of Asphalt Pavement Joints Using LWD and MASW Tests." Thesis, 2010. http://hdl.handle.net/10012/5485.
Анотація:
Longitudinal joints are one of the critical factors that cause premature pavement failure. Poor-quality joints are characterized by a low density and high permeability; which generates surface distresses such as ravelling or longitudinal cracking. Density has been traditionally considered as the primary performance indicator of joint construction. Density measurements consist of taking cores in the field and determining their density in the laboratory. Although this technique provides the most accurate measure of joint density, it is destructive and time consuming. Nuclear and non-nuclear gauges have been used to evaluate the condition of longitudinal joint non-destructively, but did not show good correlation with core density tests. Consequently, agencies are searching for other non-destructive testing (NDT) options for longitudinal joints evaluation.
NDT methods have significantly advanced for the evaluation of pavement structural capacity during the past decade. These methods are based either on deflection or wave velocity measurements. The light weight deflectometer (LWD) is increasingly being used in quality control/quality assurance to provide a rapid determination of the surface modulus. Corresponding backcalculation programs are able to determine the moduli of the different pavement layers; these moduli are input parameters for mechanistic-empirical pavement design. In addition, ultrasonic wave-based methods have been studied for pavement condition evaluation but not developed to the point of practical implementation. The multi-channel analysis of surface waves (MASW) consists of using ultrasonic transducers to measure surface wave velocities in pavements and invert for the moduli of the different layers.
In this study, both LWD and MASW were used in the laboratory and in the field to assess the condition of longitudinal joints. LWD tests were performed in the field at different distances from the centreline in order to identify variations of the surface modulus. MASW measurements were conducted across the joint to evaluate its effect on wave velocities, frequency content and attenuation parameters. Improved signal processing techniques were used to analyze the data, such as Fourier Transform, windowing, or discrete wavelet transform. Dispersion curves were computed to determine surface wave velocities and identify the nature of the wave modes propagating through the asphalt pavement. Parameters such as peak-to-peak amplitude or the area of the frequency spectrum were used to compute attenuation curves. A self calibrating technique, called Fourier transmission coefficient (FTC), was used to assess the condition of longitudinal joints while eliminating the variability introduced by the source, receivers and coupling system.
A critical component of this project consisted of preparing an asphalt slab with a joint in the middle that would be used for testing in the laboratory. The compaction method was calibrated by preparing fourteen asphalt samples. An exponential correlation was determined between the air void content and the compaction effort applied to the mixture. Using this relationship, an asphalt slab was prepared in two stages to create a joint of medium quality. Nuclear density measurements were performed at different locations on the slab and showed a good agreement with the predicted density gradient across the joint.
MASW tests were performed on the asphalt slabs using different coupling systems and receivers. The FTC coefficients showed good consistency from one configuration to another. This result indicates that the undesired variability due to the receivers and the coupling system was reduced by the FTC technique. Therefore, the coefficients were representative of the hot mix asphalt (HMA) condition. A comparison of theoretical and experimental dispersion curves indicated that mainly Lamb waves were generated in the asphalt layer. This new result is in contradiction with the common assumption that the response is governed by surface waves. This result is of critical importance for the analysis of the data since MASW tests have been focusing on the analysis of Rayleigh waves.
Deflection measurements in the field with the LWD showed that the surface modulus was mostly affected by the base and subgrade moduli, and could not be used to evaluate the condition of the surface course that contains the longitudinal joints. The LWDmod software should be used to differentiate the pavement layers and backcalculate the modulus of the asphalt layer. Testing should be performed using different plate sizes and dropping heights in order to generate different stress levels at the pavement surface and optimize the accuracy of the backcalculation.
Finally, master curves were computed using a predictive equation based on mix design specifications. Moduli measured at different frequencies of excitation with the two NDT techniques were shifted to a design frequency of 25 Hz. Design moduli measured in the field and in the laboratory with the seismic method were in good agreement (less than 0.2% difference). Moreover, a relatively good agreement was found between the moduli measured with the LWD and the MASW method after shifting to the design frequency.
In conclusion, LWD and MASW measurements were representative of HMA condition. However, the condition assessment of medium to good quality joints requires better control of the critical parameters, such as the measurement depth for the LWD, or the frequency content generated by the ultrasonic source and the coupling between the receivers and the asphalt surface for the MASW method.
41
Lin, Chung-Kuang, and 林宗寬. "Electromigration in flip-chip solder joints: Effect of temperature on failure mechanism and analysis of bump resistance curves." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/3ysq4b.
Анотація:
博士國立交通大學
材料科學與工程學系所
102
Temperature-dependent electromigration failure was investigated in solder joints with Cu metallization at 126°C, 136°C, 158°C, 172°C, and 185°C. At 126°C and 136°C, voids formed at the interface of Cu6Sn5 intermetallic compounds and the solder layer. However, at temperatures equal 158°C or greater than, extensive Cu dissolution and thickening of Cu6Sn5 occurred, and few voids were observed. We proposed a model considering the flux divergence at the interface. At temperatures below 131°C, the electromigration flux leaving the interface is larger than the in-coming flux. Therefore, voids formed at the interface. Yet, the in-coming Cu electromigration flux surpasses the out-going flux at temperatures above 131°C. This model successfully explains the experimental results. This study also examines the formation of Sn-rich phases in the matrix of Cu-Sn-Ni intermetallic compounds (IMCs) after current stressing of 1.2 × 104 A/cm2 at 160°C. The Sn-rich phases were formed at the cathode end of the solder joints with Cu metallization, and this formation was attributed to the decomposition of Cu6Sn5 IMCs. When the Cu6Sn5 IMCs were transformed into Cu3Sn during current stressing, Sn atoms were released. Due to the insufficient supply of Cu atoms, Sn atoms accumulated to form Sn-rich phases among the Cu-Sn-Ni IMCs. Resistance curves play a crucial role in detecting damage of solder joints during electromigration. In general, resistance increases slowly in the beginning, and then rises abruptly in the very late stage; i.e., the resistance curve behaves concave-up. However, several recent studies have reported concave-down resistance curves in solder joints with no satisfactory explanation for the discrepancy. In this study, electromigration failure mode in Sn2.5Ag solder joints was experimentally investigated. The bump resistance curve exhibited concave-down behavior due to formation of IMCs. In contrast, the curve was concave-up when void formation dominated the failure mechanism. Finite element simulation was carried out to simulate resistance curves due to formation of IMCs and voids, respectively. The simulation results indicated that the main reason causing the concave-down curve is rapid formation of resistive Cu6Sn5 IMCs in the current-crowding region, where resistivity is nine times larger than that of Cu. Therefore, when Cu reacted with Sn to form Cu6Sn5 IMCs, the resistance increased abruptly, resulting in the concave-down resistance curve. Cu3Sn was constantly found in the solder joint after current stressing. In this study, two different types of Cu3Sn formed according to the stressing temperature of solder joints. The solder joint was under 1.30 × 104 A/cm2 current stressing test at 170°C, the solder joint could transform to layer Cu3Sn joints. However, when the stressing temperature increased to 222°C and the current density was 2.27 × 104 A/cm2, an interesting porous Cu3Sn formed at the solder joint. The formation mechanism of porous Cu3Sn, Could be explained by the phase transformation and side wall wetting phenomenon.
42
Arcovio, STEFANO. "FATIGUE PERFORMANCE OF A HYBRID CFRP/STEEL SPLICE DETAIL FOR MODULAR BRIDGE EXPANSION JOINTS." Thesis, 2013. http://hdl.handle.net/1974/8124.
Анотація:
As traffic demand on bridges increases, loading cycles on critical components will increase, reducing their service life. Modular bridge expansion joints, which are imperative to allowing the bridge superstructure to move, are susceptible to fatigue damage at their field splice. These splices are used to connect segments of the total joint, during staged construction. Current splice designs are either bolted or welded connections, which allow stress concentrations to induce pre-mature fatigue failure. This thesis examines the use of a hybrid FRP/steel design under fatigue loading for use as a splice detail.
The splice detail consists of steel plates bolted to steel beam webs and CFRP pultruded plates adhesively bonded to the underside of the steel beam flanges. Two different moduli of CFRP were examined: Normal Modulus and Ultra High Modulus. Two beams of each modulus were tested under static conditions and six under constant amplitude fatigue loading. A testing rig was used to simulate similar bending moments experienced in bridge joints.
In the static tests, slippage of the web plates caused considerable stiffness loss and the slippage load varied drastically between CFRP moduli. For the fatigue tests, the intention was to reach two million cycles at the different constant load ranges. Stiffness degradation was noticed during the fatigue process, and was likely due to bolt pre-tension loss and/or plastic deformation of the adhesive. Specimens that reached two million cycles were monotonically loaded to failure. Once the CFRP had failed, a secondary mechanism was observed for reserve load capacity.
Simple beam mechanics were used to create prediction models for the initial spliced beam stiffness and peak CFRP load. Flexural and shear deformations of the spliced system were considered for beam stiffness. For the CFRP failure load prediction, a design peak strain in the CFRP was used to account for shear lag effects in the material and variability of the splice detail. While the model was inaccurate for beam stiffness, it provided a good approximate of the peak CFRP load. Based on the presented test data, the Normal Modulus CFRP hybrid splice detail showed better fatigue performance than conventional steel connection details.Thesis (Master, Civil Engineering) -- Queen's University, 2013-07-24 11:28:19.728
43
Lai, Tzung-Chi, and 賴宗祺. "Prediction on Shear Stress-Strain Curve of Beam-Column Joint without Shear Reinforcement by Means of Softened Truss Model." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/48637099010730042354.
Анотація:
碩士國立中央大學
土木工程研究所
92
This thesis comes from an idea of Hakuto’s shear degradation curve provided in 1990’s, proposing a rationally theoretical model verified basing on experimental data. The purpose of this study is to simulate the beam-column joint using a panel truss model via present concrete softened theories to find out the degradation curve of joint. Meanwhile, the analytical results of shear. Degradation on curves of beam-column joints can offer a tool for the seismic assessment of building structures. Results show, in order to predict the ultimate joint stress, the ratio of joint reinforcement have to properly reduce, restricting to the assumption of distributed joint reinforcement of the panel analysis. To obtain joint shear degradation curve, previous softened concrete models are adopted. According to data fitting, 1995’s Belarbi and Hsu softened model with Thorefeldt can simulate the behavior of beam-column joint well. However, it needs more experimental verification.
44
Mittal, Anshul. "Mechanical Characterization of Adhesively Bonded Jute Composite Joints under Monotonic and Cyclic Loading Conditions." Thesis, 2017. http://etd.iisc.ac.in/handle/2005/3271.
Анотація:
Fiber-reinforced composites comprise an important class of lightweight materials which are finding increasing applications in engineering structures including body components of automobiles and aircraft. Traditionally, synthetic fibers made of glass, carbon, etc. along with a polymeric resin have constituted the most common composites. However, due to environmental concern, occupational health safety considerations, higher cost, etc., research has been focused on substituting synthetic fibers, especially glass fibers with safer, economic and biodegradable natural fibers. Due to the ease of availability and affordability in terms of cost, woven jute mats, among a wide variety of natural fiber-based reinforcements, offer a good choice in combination with a suitable resin such as polyester or epoxy for fabrication of composite laminates. In structural applications, joining of parts made of jute fiber-reinforced composites (JFRCs) would be a natural requirement. Alternatives to joining processes for metals such as welding, riveting, etc. are required for composites. A joining process of high potential is adhesive bonding which has the advantages of reducing stress concentration, permitting fastening of dissimilar materials, etc.
In the present study, adhesively bonded joints of JFRCs and their mechanical behavior are investigated under quasi-static and cyclic loading conditions. Initially, characterization of substrates is carried out under monotonic loading. This is followed by determination of stress-
Strain curves, failure load and mean shear strength of bonded joints as functions of joint curing temperature and overlap length using a two-part structural epoxy adhesive. All tests are carried out according to relevant ASTM standards. It has been observed that higher curing temperatures give rise to only marginally high failure load and mean shear stress at failure compared to curing at room temperature. For a given curing temperature, failure load increases while mean shear strength decreases with respect to overlap length in both types of joints.
As fatigue failure is a crucial consideration in design, the behavior of adhesively bonded JFRC joints is studied for the first time under cyclic loading conditions leading to the commonly-used S-N curve for characterization of failure of materials at different loading-unloading cycles. Interestingly, the fatigue strength for infinite life of adhesively bonded JFRC joints turns out to be approximately 30% of the quasi-static strength, a correlation which usually applies to materials in general. The effect of joint overlap length on fatigue life is studied and it is observed that the above relation between fatigue and quasi static strength is retained for different overlap lengths. Additionally, insights are provided into failure modes of joints under different loading conditions and for varying overlap lengths. Various empirical predictors such as exponent, power and hybrid models fitting the S-N curve are obtained and their relative efficacy (in terms of Coefficient of Determination R2, Adjusted-R2, Akaike’s Information Criterion and Residual Sum of Squares) enumerated in prediction of failure load including quasi-static failure load.
As numerical simulation is an indispensable tool in designing geometrically complex structures under nonlinear conditions including failure and contact, finite element modeling of JFRC substrates, bulk adhesive and adhesively bonded joints has been investigated using implicit and explicit LS-DYNA solvers. In this context, the effects of various modeling parameters (mesh size and loading rate) and details of constitutive models capable of capturing plasticity and failure in an orthotropic composite and isotropic adhesive are discussed. Mesh size has been found to be an important parameter affecting computed results. Finally, a good correlation within ~(4% - 7%) was found between the predicted and experimental results for JFRC substrates, bulk adhesive and adhesively bonded single lap joints.
45
Mittal, Anshul. "Mechanical Characterization of Adhesively Bonded Jute Composite Joints under Monotonic and Cyclic Loading Conditions." Thesis, 2017. http://hdl.handle.net/2005/3271.
Анотація:
Fiber-reinforced composites comprise an important class of lightweight materials which are finding increasing applications in engineering structures including body components of automobiles and aircraft. Traditionally, synthetic fibers made of glass, carbon, etc. along with a polymeric resin have constituted the most common composites. However, due to environmental concern, occupational health safety considerations, higher cost, etc., research has been focused on substituting synthetic fibers, especially glass fibers with safer, economic and biodegradable natural fibers. Due to the ease of availability and affordability in terms of cost, woven jute mats, among a wide variety of natural fiber-based reinforcements, offer a good choice in combination with a suitable resin such as polyester or epoxy for fabrication of composite laminates. In structural applications, joining of parts made of jute fiber-reinforced composites (JFRCs) would be a natural requirement. Alternatives to joining processes for metals such as welding, riveting, etc. are required for composites. A joining process of high potential is adhesive bonding which has the advantages of reducing stress concentration, permitting fastening of dissimilar materials, etc.
In the present study, adhesively bonded joints of JFRCs and their mechanical behavior are investigated under quasi-static and cyclic loading conditions. Initially, characterization of substrates is carried out under monotonic loading. This is followed by determination of stress-
Strain curves, failure load and mean shear strength of bonded joints as functions of joint curing temperature and overlap length using a two-part structural epoxy adhesive. All tests are carried out according to relevant ASTM standards. It has been observed that higher curing temperatures give rise to only marginally high failure load and mean shear stress at failure compared to curing at room temperature. For a given curing temperature, failure load increases while mean shear strength decreases with respect to overlap length in both types of joints.
As fatigue failure is a crucial consideration in design, the behavior of adhesively bonded JFRC joints is studied for the first time under cyclic loading conditions leading to the commonly-used S-N curve for characterization of failure of materials at different loading-unloading cycles. Interestingly, the fatigue strength for infinite life of adhesively bonded JFRC joints turns out to be approximately 30% of the quasi-static strength, a correlation which usually applies to materials in general. The effect of joint overlap length on fatigue life is studied and it is observed that the above relation between fatigue and quasi static strength is retained for different overlap lengths. Additionally, insights are provided into failure modes of joints under different loading conditions and for varying overlap lengths. Various empirical predictors such as exponent, power and hybrid models fitting the S-N curve are obtained and their relative efficacy (in terms of Coefficient of Determination R2, Adjusted-R2, Akaike’s Information Criterion and Residual Sum of Squares) enumerated in prediction of failure load including quasi-static failure load.
As numerical simulation is an indispensable tool in designing geometrically complex structures under nonlinear conditions including failure and contact, finite element modeling of JFRC substrates, bulk adhesive and adhesively bonded joints has been investigated using implicit and explicit LS-DYNA solvers. In this context, the effects of various modeling parameters (mesh size and loading rate) and details of constitutive models capable of capturing plasticity and failure in an orthotropic composite and isotropic adhesive are discussed. Mesh size has been found to be an important parameter affecting computed results. Finally, a good correlation within ~(4% - 7%) was found between the predicted and experimental results for JFRC substrates, bulk adhesive and adhesively bonded single lap joints.
46
zeng, yu-ling, and 曾毓玲. "The Effect of Group Buying Curve Appeal on Consumer's Intentions to Join Group Buying." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/57471714544262734032.
Анотація:
碩士國立嘉義大學
行銷與流通管理研究所
95
Abstract With the development of internet netowrk, and the transparent of information casuses the marketing right to transfer, and then creat consumers with of the strong negociation price, so do group shopping beconme a kind of possible trade type. The feature of group buying is that the price will go down as the accumulated orders are increasing. However, consumer will not know the final price forecast of group buying. So, consumers only can consider whether they can join the group buying or not. As such, how to speed make the consumers join the group buying, become they concerns essential issue. At present, many group buying web provide motiviation system to attract potential consumers join it. Although this ways can efficiency attract potential consumers under the motivation system，outside the motivation system can not any appeal to consumers. And the price information which the group buying website use it do the way of appealing through the form, figure. So this resaerch expects that presents the way through another kind of price curve, let consumers pass the result on vision, the consciousness reaches prices to drop fast, and can consumers to predict the final price, reduce congitive effort, promoting the memory and attitugde of the information of the price, than can raise the consumers accede to the intetion of the group buying. The experimet method was applied this study. In order to improve the research validly and reliability the questionnaire was used to collect the quantitative data. Findings showed that the consumers’ predict the final price、congitive effort、attitude and memory of the advertisement significantly ( p<0.05 ) impacted on price curve. Further, both memory of the advertisement and congitive effort significantly( p<0.05 ). That is, via increasing the consumers’ memory of the advertisement and reduce their congitive effort, raise their attitude of the advertisement. It has proved that if the consumer has the good attitude toward to the price curve and this price cureve can effectively help to predict the final price, then the consumers’s joint of intention in group buying will uprise relatively. The statistics shows that :through the dynamic price curve can effectively the consumer’s joint of intention in group buying. Managerial implications of how B2C Website can sort out the problems of the price information boring not attract potential consumers joint the group buying.
47
Lewis, Barbara Jane. "To determine the immediate effect of sacroiliac and lumbar manipulation on quadriceps femoris and hamstring torque ratios in the contralateral limb in patients suffering from mechanical low back pain." Thesis, 2005. http://hdl.handle.net/10321/199.
Анотація:
Thesis (M.Tech.:Chiropractic)-Dept. of Chiropractic, Durban Institute of Technology, 2005
120 leavesLow back pain has been shown to be associated with inhibition of the lower limb musculature. This inhibition is called arthrogenic muscle inhibition (AMI). Sacroiliac joint dysfunction has been linked with AMI of the ipsilateral and contralateral quadriceps and hamstring muscles. Sacroiliac manipulation has been shown to significantly reduce ipsilateral AMI, however no studies have been conducted to illustrate the effect of sacroiliac manipulation on contralateral AMI. Neither have their been studies to show the presence or extent of spinal dysfunction between the levels of L2-L5 and its significance on muscle inhibition in the quadriceps and hamstring muscles, nor the effect of manipulation of these levels on AMI of the quadriceps and hamstring muscles. The purpose of this study was therefore to determine whether spinal manipulation has an effect on AMI of the contralateral limb as well as that of the ipsilateral limb.
48
Santos, Maria Paula Correia Pedroso dos. "Divesture/acquisition analysis: PT/Telefónica/VIVO case study." Master's thesis, 2011. http://hdl.handle.net/10071/4324.
Анотація:
The main objective of this master thesis is to evaluate the impact of events/announcements in the market capitalization of companies involved and to test market efficiency.
Acquisitions, mergers and divestures are strategies followed by companies in order to adjust to economic and political changes and explore opportunities to develop capabilities in new environments.
In this study it is analyzed the impact of selling the stake held in Vivo by PT to Telefónica in the market capitalization of the both companies. Additionally it was applied the event study methodology suggested by Mackinlay et al. (1997). This methodology can be used to measure the impact of a specific event on the market capitalization of companies with the purpose to test market efficiency in capital markets.
In this study were detected abnormal returns in every events in analysis, with special focus on event 2 and 3, that correspond respectively, to the day 1st June 2010 (day in which Telefónica launched the second offer in order to acquire Vivo, for the amount of €6.5 bn) and the day 30th June 2010 (day when the General Board Meeting occurred and the Portuguese government used the golden share in order to block the operation).O principal objectivo desta tese de mestrado é avaliar o impacto dos eventos/anúncios na capitalização bolsista das empresas de forma a testar a eficiência dos mercados. As aquisições, fusões e desinvestimentos são estratégias levadas a cabo pelas empresas de forma a ajustarem-se ás mudanças económicas e políticas para assim desenvolverem novas capacidades que lhes permitam aproveitar as oportunidades que existem na envolvente. Neste estudo analisa-se o impacto que a venda da participação da PT na Vivo, á Telefónica, teve na capitalização bolsista de ambas as empresas. Adicionalmente, é também aplicada a metodologia do estudo de eventos sugerida por Mackinlay et al. (1997). Esta metodologia tem como objectivo medir o impacto de um evento/anúncio específico na capitalização bolsista das empresas, estando desta forma a testar a eficiência dos mercados de capitais. Neste estudo detectaram-se rentabilidades anómalas em todos os eventos em análise, com especial incidência no evento 2 e 3, que correspondem respectivamente, ao dia 1 de Junho de 2010 (dia em que a Telefónica lançou a segunda oferta com o objectivo de adquirir a participação detida pela PT na Vivo pelo montante de €6.5 bn) e ao dia 30 de Junho de 2010 (dia em que ocorreu a Assembleia Geral de Accionistas da PT em que foi usada a Golden Share por parte do Governo Português de forma a bloquear a operação).
49
SAIYAR, MASOUMEH. "BEHAVIOUR OF BURIED PIPELINES SUBJECT TO NORMAL FAULTING." Thesis, 2011. http://hdl.handle.net/1974/6302.
Анотація:
Thesis (Ph.D, Civil Engineering) -- Queen's University, 2011-01-31 20:52:11.162One of the most severe hazards for buried pipelines, which are sometimes referred to as lifelines due to their essential role in delivering vital resources, is the hazard due to Permanent Ground Deformation (PGD). Earthquake induced PGD can be caused by surface faulting, landslides and seismic settlement. In this thesis, the behaviour of buried pipelines subject to normal faulting has been experimentally investigated through a series of centrifuge tests performed on both continuous and jointed pipelines. Both pipe and soil displacements were measured using image analysis. Signal processing techniques were then developed to filter this data so as to enable the calculation of curvature and other aspects of the response from the observed pipe deformations. First, a series of centrifuge tests was conducted on continuous pipelines of varying materials, representing a wide range of pipe stiffness relative to the soil and investigating the effect of pipe stiffness relative to the soil on soil-pipe interaction. The experimentally derived p-y curves at different locations along the pipe were compared to the recommended soil-pipe interaction models in the relevant guidelines. These p-y curves showed that the central shearing region was not captured well with independent soil springs. The response of the pipelines predicted by the ALA (2001) guideline, however, was shown to match the experimental data within 50%. Two new simplified design approaches were then developed. The first features calculations based on simplified pressure distributions. The second featured peak curvature normalized using a characteristic length, ipipe, the distance from peak to zero moment. A series of centrifuge tests using brittle pipes was also performed. The pipes were buried at three different depths, and the post-failure fracture angle of the pipe was measured to be used as an input for design of liners. Based on the experimental data, a computationally efficient approach was developed to estimate the initial fracture angle which occurs immediately after the pipe breaks. The last series of centrifuge tests was conducted on jointed pipelines with five different joint stiffnesses to investigate the flexural behaviour of jointed pipelines under normal faulting. Based on the observed pipe response, a simplified kinematic model was proposed to estimate the maximum joint rotation for a given geometry, pipe segment length, and the magnitude of the imposed ground displacement.
Ph.D