<p>Access floor systems have been widely used to support equipment in telecommunications central offices. In this thesis, the seismic response of equipment supported on access floors in telecommunications central offices is studied. There are two major issues for equipment supported on access floor under seismic condition. First, the access floor tends to amplify the motions from the building floor; as a result, the equipment supported on it is subjected to a more severe shaking than if it were supported directly on a building floor. Second, most access floor systems are designed for gravity load only. Their seismic performance depends on their lateral stiffness and strength. Such information is not generally available. The objective of the study is to address the first issue and to provide guidelines for the seismic analysis, design and qualification of equipment installed on access floors. This is achieved by a systematic study on the dynamic response of combined equipment-access floor systems by experimental and analytical approaches.</p> <p>The experimental work is carried out using commercial access floors of two different floor heights and a typical switching equipment unit commonly used in telecommunications central offices as test specimens. There are three phases involved in the experimental work. First, static tests are performed to investigate the stiffness and strength properties of the access floors. Second, dynamic exploratory tests are carried out to study the dynamic characteristics of the access floors, the telecommunications equipment and the combined equipment-access floor systems. Lastly, seismic tests are performed for the equipment alone and the combined equipment-access floor systems to evaluate the effect of the access floor on the seismic response of the equipment.</p> <p>Based on the observations and results of the experiment, an analytical model is developed. The reliability of the model to predict the dynamic properties and the seismic response of combined equipment-access floor systems is checked by experimental results. A parametric study is then carried out using this model to provide insight into the dynamic properties of equipment-access floor systems. The model is also used to study the seismic response of equipment supported on access floors in telecommunications central offices. Finally, design spectra for telecommunications equipment supported on access floors are generated for the purposes of seismic analysis, design and qualification.</p> / Doctor of Philosophy (PhD)

<p>The behaviour of a concrete gravity dam-reservoir-foundation system is a very complex system to analyze. Currently, the length of the reservoir is assumed infinite during the seismic analysis and design of dam structures. Since many of the natural reservoir systems are finite, this assumption may significantly miscalculate the response of the dam monolith to earthquake ground motion. The objective of this research is to investigate the effect of a finite length upstream reservoir on the monolith's seismic response, including consideration of the reservoir's characteristics. This study is comprised of three main components. First, a closed form solution of the dam-reservoir problem is developed. The ground motion is assumed to only excite the dam monolith. Second, a detailed analysis procedure is used to investigate the response of the monolith when both the monolith and the reservoir's far boundary is excited. Lastly, a stress analysis is conducted to examine the effect of a finite length reservoir on the dynamic tensile stresses that are developed in the monolith. The finite length of the upstream reservoir was found to be a very important parameter in defining the response of the dam monolith to seismic input. The response of the dam-reservoir-foundation system was found to be significantly different when the reservoir's length was assumed to be finite than when it was assumed infinite. The ratio of the reservoir length to dam height (L/H), the reservoir-foundation interface, the monolith's elastic modulus, the phase of the ground motion between the monolith and the reservoir's far boundary, and the reservoir's far boundary have all been determined to be important aspects in defining the monolith's dynamic and seismic response.</p> / Doctor of Philosophy (PhD)

<p>In spite of significant improvements in the quantification of site effects in the NBCC (National Building Code of Canada) since the introduction of the foundation factor (F) in 1965, recent parametric studies have shown the 1990 NBCC provisions for site effects to be inadequate. In addition, soil-structure interaction effects are neglected in the current NBCC provisions. The current study, aimed at investigating the implications of these soil-structure interaction effects on the seismic response of high-rise reinforced concrete buildings, is carried out for three cities in Canada, namely Ottawa, Vancouver and Prince Rupert. Soil models are developed to correspond to the soil classifications used to define F in the 1990 NBCC. For each of the three cities, structural models are developed to represent both 20-storey reinforced concrete ductile moment-resisting frames and ductile flexural walls. Three sets of ground motion records are developed to represent the postulated bedrock motions at each of the three cities, based on the magnitude and source-distance combinations dominating the seismic hazard at the respective sites. The computer program FLUSH is used to perform the analyses of the various soil-structure systems. Results from the current study indicate that the code F values generally underestimate the site effects associated with the respective soil deposits, but appear to be reasonably adequate, in most cases, when soil-structure interaction effects are taken into consideration. In spite of some apparent deficiencies in the code F values, the 1990 NBCC design base shear is shown to be conservative for regular high-rise reinforced concrete buildings. Conventional uncoupled analyses are shown to provide estimates of the coupled base shear demand that are too conservative. A simple measure to account for the inertial interaction effects in uncoupled analyses is proven to provide a significant improvement in the prediction of the coupled base shear demand. A simplified approach to estimate the coupled system period is shown to provide a satisfactory estimate of values based on the rigorous, but time-consuming coupled analyses.</p> / Doctor of Philosophy (PhD)

<p>A study has been conducted on the seismic site response of alluvial valleys with limited width and the effects of spatially varying surface motions in these valleys on the response of a suspension bridge. The intent of this investigation is to extend the work carried out by seismologists on the two-dimensional seismic response of alluvial valleys to include the effects of stiffness variation with depth and non-linear behaviour of soils which were mainly considered by engineers in a one-dimensional perspective. One objective is to provide engineers with useful guidelines to predict the valley response at different sites. Another objective is to analyze the potential of soil conditions and subsurface topographic structure in alluvial valleys for producing significant variations in the bridge response to a multiple-support excitation. A simplified engineering model (frame model) has been developed to predict the non-linear seismic response of symmetrical valleys. The proposed model is a one-dimensional model which accounts for the limited horizontal extent of soil in a two-dimensional valley. The frame model provides valuable insight into the dynamic behaviour of the alluvial valley by identifying the vibration modes of significance and their variation in the horizontal and vertical directions. Response results from the frame model show good agreement with those results from the two-dimensional finite-element model of the valley. Effect of the key parameters governing the spatial variations of motions at different sites in the valley has been analyzed. This includes the effect of soil type, valley geometry and control motion characteristics in rock. It is found that the two-dimensional effect from the valley edges extends toward the centre up to a distance after which only one dimension, the depth, governs the response. The soil amplification varies from one soil type to another, depending on the stiffness of soil and the amount of damping existing during excitation. The magnitude of the surface spectral acceleration at a site depends on the proximity of the local-amplification period at site to the dominant period of the input rock record. Finally, the free-field surface motions in a hypothetical valley are applied to the Humber suspension bridge in U.K. It is concluded that the inclusion of the multiple-support excitation case in the analysis is significant when soil conditions and topography produce noticeable variations in the intensity of support motions in the period range of interest for the bridge response.</p> / Doctor of Philosophy (PhD)

<p>The object of this work is to explore in depth a variety of polymer forming processes and to examine the behavior of polymers during processing by developing large deformation finite element models and computer tools for the numerical simulations of the processes. Thermoforming, one of the major forming processes dealt with in this thesis, is the fabrication of numerous plastic products by use of heat, pressure and mold. Thermoforming is penetrating existing and new product categories due to ease of production, low costs, and the high performance of final products. Axisymmetrical finite element models have been developed that include large deformation, large strain, moving boundaries, contact of polymer with rigid mold, deformation-dependent loading, free surface evolution, and material nonlinearities. The thermoplastics in the forming processes are considered as incompressible, hyperelastic materials, since there is little time for viscous dissipation. The incompressibility condition is accurately incorporated by employing the penalty method. No restriction of sheet thickness is made in the models for thermoforming so that thermoforming of single layer or multilayer composite sheets of finite thickness can be dealt with, as well as plug-assist forming of thick sheet. A simple, efficient method for passing the limit point is established in the finite element formulations, and for the first time the limit point in thermoforming is successfully simulated using this method. Numerical simulations compare well with analytical solutions for simple geometries and experiments for thermoforming, plug-assist forming, combined plug-assist pre-stretching and vacuum forming, and compression forming. The important parameters in the processes which influence processing and products are studied, including the effects of material constants, boundary conditions, and processing sequence. For these processes, information of deformation and stress can be obtained by the developed computer models, such as deformed profile, thickness variation, the relationship between applied loading and deformation, and stress and strain variations at critical areas, which are important in process optimization and damage analysis. The computer modeling and analysis provide a comprehensive understanding of these forming processes and could be valuable for industrial designers in the process of reducing trial-and-error procedures, optimizing their designs, minimizing material and cost, and maximizing product performance.</p> / Doctor of Philosophy (PhD)

<p>The available literature on the in-plane behaviour of masonry was categorized and reviewed under one of three research approaches; experimental testing of masonry shear walls, microscopic modelling, and macroscopic modelling. The significant differences found in the results obtained from different research programs may leave a wrong impression about the potential of masonry as a structural material. The literature review also pointed out the lack of experimental data on the macro-behaviour of grouted concrete masonry, particularly for reinforced assemblages. Accordingly, the reported investigation provides explanations of behaviours which lead to an improved understanding of the in-plane behaviour of grouted concrete masonry. The experimental part provides a body of test data for North American conditions (practice and material) to form the basis of a macro-behaviour model. The experimental program in this investigation included two major parts; biaxial tests and auxiliary tests. The biaxial tests involved a total of 36 full scale unreinforced or reinforced panels tested under uniform states of biaxial tension-compression. A biaxial test rig was specially devised to perform these tests. The variables considered covered the bed joint orientation θ, the ratio between principal stresses σ₁/σ₂, and the percentages of reinforcement used parallel and normal to the bed joints. The auxiliary tests comprised 33 prisms tested under uniaxial compression, 27 prisms tested under uniaxial tension, and 15 couples tested under direct shear. In addition, a large number of component material tests were performed to determine the physical and mechanical properties of each material used. These also served as control tests. A macro-model was proposed to predict the in-plane behaviour of grouted concrete masonry. In this model, the masonry assemblage was replaced by an "equivalent material" which consisted of a homogenous medium intersected by two sets of planes of weakness (along the head joint and bed joint planes) and two sets of reinforcement. The macro-behaviour of the "equivalent material" was determined by smearing the influence of these sets, which provided a means for modelling the inherent part of the anisotropic characteristics of masonry assemblages. On the other hand, the behaviour of the homogeneous medium was described by an orthotropic model to account for the induced part of the anisotropic characteristics. The reliability of the proposed model was confirmed using the experimental results from this investigation and others. The model was also used to fill the gaps in the available test results and to provide a more complete picture of the in-plane behaviour of grouted masonry.</p> / Doctor of Philosophy (PhD)

Titanium and its alloy (Ti-6Al-4V) are widely used in aerospace industries because of their light weight, high specific strength, and corrosion resistance. This study conducted a comparative experimental analysis of the machinability of Ti-6Al-4V for conventional flood coolant machining and sustainable dry machining. The effect of cutting speed, feed rate, and depth of cut on machining performance has been evaluated for both conditions. The machining time and surface roughness were found to be lower in dry machining compared to flood coolant machining. The tool wear was found to be unpredictable, and no significant difference was observed for dry and coolant machining. In a comparison of all the parameters, sustainable dry machining was found to provide better performance in machining Ti-6Al-4V. This study also investigated the machinability of Ti-6Al-4V using coated and uncoated tungsten carbide tools under dry conditions. Tool wear is a serious problem in the machining of titanium alloys in dry conditions. Heat dissipation from the toolworkpiece interface a difficult challenge in dry machining, resulting in the alloying of the workpiece to the tool surface. Dry machining with the coated tool was comparatively faster, and resulted in less tool wear than uncoated tools. Using the Titanium aluminum nitride TiAlN coated carbide tool during dry machining provided a smoother surface finish with lower average surface roughness. The conclusion, therefore, is that the tool coating was found to be effective for the dry machining of titanium alloys.

<p>Som en del i Maskiningenjörsutbildningen vid Karlstads Universitet har detta examensarbete utförts under en 15 veckors period. Uppdragsgivare är Scana Steel AB:s stålverk i Björneborg och arbetet behandlar en av deras traverser. Arbetet bestod i att lokalisera och om möjligt förinta vibrationer som uppfattas som störande i förarhytten till traversen. För att lokalisera vibrationerna har olika analyser genomförts med hjälp av SpectraPro samt Vibshape, vilket är två mjukvaror tillhörande mätutrustningen Easy Viber. Dessa två program ger oss möjlighet att se animeringar av traverskroppens rörelse och visa spektran för specifika punkter.</p><p>Analyserna visar på att förarhytten huvudsakligen rör sig vid tre olika frekvenser. Frekvenserna i hytten visar sig överensstämma med frekvenserna från det sista kuggingreppet på växellådan samt från kopplingen mellan motor och växellåda. En del resonansfenomen har tagits i beaktning.</p><p>Metoderna för att undvika att föraren känner obehagliga vibrationer är flera och skiljer sig stort i hur omfattande operationer som krävs. Det finns dock några åtgärder som smidigt kan prövas.</p><p>Föreslagna åtgärder för avhjälpning av vibrationerna innefattar bland annat frekvensstyrning, dynamisk dämpare och dämpande maskinfötter.</p> / <p>As a part of the Machine engineer-program at Karlstad University this dissertation has been in progress for 15 weeks. The principal is Scana Steel AB, a steelworks in Björneborg and the dissertation concerns one of their cranes. The task was to find sources to vibration and, if possible, eliminate the vibrations that the driver in the wheelhouse finds uncomfortable. To locate the source of the vibrations different analyses have been made with the help of SpectraPro and Vibshape, which are two softwares belonging to the measuring instrument Easy Viber. These two programs gave us the possibility to animate the movements of different components and they also gave us different spectra to analyze.</p><p>The analyses show that the wheelhouse mainly vibrates in three different frequencies. These frequencies appear to be the same as the frequencies from the last cogwheel and the coupling. When determining the frequencies we have also taken some resonance phenomena into consideration.</p><p>The methods how to avoid that the driver is uncomfortable due to the vibrations are numerous and require different sizes of operation. Some actions can, however, easily be tried without any bigger problems.</p><p>Suggested actions are among others dynamic damper, frequency control and damping machine shoes.</p>

<p>To improve the usage of material in fatigue loaded complex welded structures a better calculation method (based on FEA) is needed than what is available on the market and an improved management of weld quality. Improved FE-procedures are directly applicable to design of generic structural components within virtually all industries using CAD and FEtools, irrespective of industrial sector. More and more welded structures are created as 3D models from the design offices and the FE-work will be easier but the requirement of being accurate from the beginning and the reduction of lead times create a great need to substantially reduce calculation time. </p><p>The main objectives in this thesis is to develop novel procedures to extract design data from finite element stress analyses of complex fatigue loaded welded structures, to achieve a better understanding of the limits of the different fatigue design methods and to investigate the influence of fatigue strength due to the weld quality. </p><p>An investigation of how weld geometry and different type of defects influence fatigue life of the weld has been made on a non-load carrying cruciform joint. The weld geometries were measured and the stress distributions were computed using FEA. Fatigue tests have been performed and the initial defects were analysed. Life predictions with LEFM based on the stress distributions and defects were performed with good agreement with the test results. </p><p>The different fatigue design methods Nominal stress, Structural stress, Effective Notch stress and LEFM proposed by the International Institute of Welding (IIW) have been investigated and applied on a welded link. In order to verify the accuracy of the prediction methods, fatigue tests of the link were made. Structural optimisations based FEA, using different objectives regarding the fatigue properties of the welded link were also carried out to increase the performance of the link. </p><p>Comparison and investigations of the advantages and disadvantage of the two different LEFM approaches, weight function technique and FEA solutions is made on welded structures. Based on the conclusions of the investigations an automatic 3D FE based LEFM program was developed. The program was successfully implemented and verified on two welded structures.</p>

Structural health monitoring (SHM) is a quickly advancing field of study in civil engineering and recent advances in the field are in stark contrast to where the field started. For example modern technology of wireless sensing systems allowed for easier monitoring of structures, but the challenge of limiting the number of instrumented locations has not been overcome with traditional methods. The potential of alternative methods has only been realized in recent years with the increase of model based approaches. In particular, the use of limited measurements to estimate structural response at all locations is appealing. To accomplish this goal, this work approaches SHM by using a numerical model combined with a linear recursive state estimation algorithm, known as the Kalman Filter, to update the model-based prediction with a limited number of real time measurements taken on the structure. A thorough overview of the contents is given here. The first section introduces the topic of SHM and the goal of SHM. Then the challenges and limitation that face SHM are discussed along with the recent advances that can be used to overcome them. In Section 2, the proposed framework, a Kalman filter approach, is established. First, a finite element model is formulated for plate structures using the Mindlin-Reissner plate theory and then this finite element code is verified by a comparison with a commercial FEA software. Then the state space model of the system is defined for use with the Augmented Kalman Filter (AKF); the AKF approach overcomes the intrinsic challenge of unknown excitations for civil structures. The AKF is then formulated and discussed. For Section 3, using the AKF in numerical simulations are conducted for 5 different cases. The first three cases study the advantages of multi-metric measurements, i.e. strain and acceleration measurements combined, versus single metric measurement, i.e. strain measurement only or acceleration measurement only. Following that, the next two cases explore the question of whether multi-metric measurements will always provide the best results. Based on the conclusions from the previous section, Section 4 investigates the application of a genetic algorithm, a search algorithm based of Darwinian principles, to find the optimal sensor placement to use as the input to the AKF. Here the developed search algorithm is used in two cases, the first is to find the optimal placement for the strain measurement only case. Next, the improvements in accuracy that are gained by placing taking more measurements is investigated to determine if the gain in accuracy per added measurement decreases for large numbers of measurements. Section 5 contains the final conclusions about the use of the AKF for SHM of plate structures then the potential opportunities of future work regarding plate structures are discussed.