In North America, cold-formed square and rectangular hollow sections (collectively referred to as RHS hereinafter) of commonly specified cross-sectional dimensions are produced using either the indirect-forming approach or the direct-forming approach. The indirect-forming approach, as the conventional approach of the two, consists of three steps: (i) roll-forming the coil material progressively into a circular hollow section; (ii) closing the section using electric resistance welding (ERW); and (iii) reshaping the circular section into the final square or rectangular shape. On the other hand, the direct-forming approach, as the new approach of the two, roll-forms the coil material directly into the final square or rectangular shape. RHS with similar cross-sectional dimensions but different production histories (i.e., different cold-forming approaches and post-production treatments) are expected to have significantly different material and residual stress properties. However, RHS design provisions in the existing North American steel design standards (AISC 360-16 and CSA S16-19) are in general developed based on research on indirect-formed RHS and currently do not differentiate RHS cold-formed by different approaches. Based on the research presented in Chapter 1 of this thesis, comparing to indirect-formed RHS, direct-formed RHS in general contain lower levels of residual stresses around cross sections, since the flat faces are not severely cold worked during production. This in turn affects member behaviours under compressive and flexural loadings. The test results presented in Chapters 2 and 4 show that direct-formed RHS have superior stub column and beam behaviours, comparing to their indirect-formed counterparts. In particular, the stub column and beam testing programs, covering a wide range of cross-section dimensions and two strength grades (nominal yield stresses of 350 and 690 MPa), show that the slenderness limits in the existing North American steel design standards are excessively conservative for direct-formed RHS, resulting in unnecessary penalty and member strength underestimation. As a result, the existing design formulae are not suitable for direct-formed RHS. In response to this, subsequent finite element (FE) parametric investigations are performed and presented in Chapters 3 and 5. Modified stub column and beam design recommendations for direct-formed regular- and high-strength RHS are proposed. The effects of post-cold-forming hot-dip galvanizing on material properties, residual stresses, stub column behaviours and beam behaviours of direct-formed regular- and high-strength RHS are also studied in Chapters 1-5 of this thesis. Similar to the application of the heat treatment per ASTM A1085 Supplement S1 or the Class H finish per CSA G40.20/G40.21, post-cold-forming galvanizing improves the stub column (Chapter 2) and beam (Chapter 4) behaviours of direct-formed RHS via effective reduction of residual stresses (Chapter 1). Based on subsequent FE parametric investigations, modified stub column and beam design recommendations catering to galvanized direct-formed RHS are proposed in Chapters 3 and 5. / Graduate

This thesis presents the results of an investigation of factors which influence the geotechnical properties of frozen mine backfill (FMB). FMB has extensive application potential for mining in permafrost areas. The uniaxial compressive strength (UCS) of hardened backfill is often used to evaluate mine backfill stability. However, the deformation behaviour and stiffness of the FMB are also key design properties of interest. In this thesis, uniaxial compressive tests were conducted on FTB and FCPB samples. Information about the geotechnical properties of FMB is obtained. The effects of FMB mix components and vertical compression pressure on the geotechnical properties of FMB are discussed and summarized. An optimum total water content of 25%-35% is found in which the strength and the modulus of elasticity of the FTB are 1.4-3.2 MPa and 35-58 MPa, respectively. It is observed that a small amount (3-6%) of cement can significantly change the geotechnical properties of FTB.

Cross-Laminated Timber (CLT) has recently become a popular construction material for building timber structures. One advantage of CLT is, that it can be used as floor, beam and wall element. As the arrangements of layers in CLT is in perpendicular direction to each other, it exhibits remarkable strength properties in both in-plane directions. However, the low stiffness and strength properties in compression perpendicular to the grain hinder application of CLT in high rising building, since forces are usually transferred from the wall elements through floor elements perpendicular to the grain. Thus, the aim of this thesis is to get a thorough understanding of the mechanical properties of such connections for different setups, including wood-wood connections, connections with acoustic layers and connections with screws. In addition, the wall was place at different positions on the CLT-floor element. Mechanical tests and numerical simulations, by means of finite element modelling (FEM) were carried out. CLT floor elements, consisting of 5-layers, were loaded by 3-layered CLT wall elements. Displacement and deformation were continuously measured by Potentiometers/LVDTs and an optical measurement system, respectively. Based on the experimental results compressive strength, slip curve and stiffness of the CLT connections were evaluated. Subsequently, results from FE-modelling were compared with experimental findings, which show a good agreement in elastic stiffness. Experimental results exhibited a pronounced influence of the wall position and connection setup on strength and stiffness. Central position of the wall showed higher mechanical properties than edge position. Highest strength and stiffness were found for screwed connections, where the wood-wood connections showed similar results. Connections with acoustic layers exhibited the lowest mechanical properties.

An implantable hearing aid device is being developed by a project group which is part of an EU initiative. This device contains a diaphragm consisting of a submicron thick freestanding titanium film, which should be free of internal stresses. Stress is the force exerted per unit cross-sectional area of the film and it can impair the functionality and performance of the device. The stress that evolves in a thin film during deposition at a substrate is compressive or/and tensile and affects the bending that occurs of the substrate due to the lateral force applied to the substrate by the stressed film. The goal of this diploma work was to contribute to the understanding of in situ stress evolution in a micron thick titanium film and thereby by tuning different physical parameters to obtain minimal residual stress in the films after growth. Titanium films were deposited on silicon sistrates using DC magnetron sputtering. The stress in the material varied, by tuning different physical parameters such as working pressure, power, distance between magnetron and the sample and substrate bias. For this thesis, firstly two different series were done; one where the changing parameter was the distance between the sample and the magnetron and one where it was the working pressure. Later a last series were done to see what effect the bias has on the stress. A multi-beam optical sensor system (MOS) was used to measure the stress in real-time during deposition. X-ray diffraction (XRD) was later used to make post-deposition stress measurements to verify the stress obtained from the MOS. However, the MOS shows the stress evolution in real time and XRD shows a ’final’ average value that can be compared with the stress obtained from MOS-data when the deposition is finished. The results showed that the stress goes from compressive to tensile as the working pressure and the distance between the magnetron and the sample increases. There are other factors, such as the temperature/heating in the main chamber, base pressure of the main chamber, cleaning of the sample and also where the argon gas is let in to the process chamber (in this project called the main chamber (MC)), that influences the results. This will in turn influence the repeatability of the data/measurements, since these effects can affect the process of nucleation and coalescence. The stress evolution can change if a bias is applied during the initial stage of the deposition process when the film has still not grown thick. This is could be due to the bias not having much of an impact on the stress evolution when the film is thicker and thereby more porous.

There are approximately 4000 railway bridges in Sweden managed by the Swedish Administration of Transport (Trafikverket), of which a common construction type is the reinforced concrete (RC) trough bridge, which is a structure that consists of a slab carried by two longitudinal main beams which transfer loads towards the supports. A substantial amount of the RC trough bridge population is approaching the end of their service lives which consequently implies that the replacement of some of these bridges can be expected in the near future. Extending their service lives can yield positive effects from a financial- as well as an environmental perspective, and therefore it is highly beneficial to evaluate their capacities as realistically as possible. One factor that may help improve accuracy during the determination of their capacities is an evaluation of how it is affected by the location of the railway track on the bridge.  In current design codes defined by Trafikverket, consideration is taken to horizontal track displacement for a minimum displacement of 0.1 m if there doesn’t exist data suggesting that a larger displacement is prevalent on the bridge. However, Trafikverket has received data which suggest that a considerable number of bridges could experience load eccentricities which exceed the standard minimum value. This raises the question whether or not 0.1m is the most optimal limit value for load eccentricity on railway bridges. For RC trough bridges, a larger load eccentricity may result in one main beam carrying a larger portion of the load which will decrease the axle load which the bridge can carry. It is therefore important to evaluate the influence of larger horizontal displacements than what is currently is considered as a preventive action.   In addition, several studies on Swedish concrete bridges constructed during the 20th century have pointed to a significant increase in concrete compressive- and tensile strength over time. This suggests that it is possible that a considerable amount of RC trough bridges have a higher capacity than what was originally intended, and further research is required in order to understand the behaviour of these bridges when key material parameters are altered.        There are three main tasks which this master thesis seeks to complete. The first part is a detailed analysis of a database named BaTMan (Bridge and Tunnel Management) that belongs to Trafikverket. In this analysis parameters such as span length, age, material type and damages for every identified railway bridge is extracted and further processed in Microsoft Excel in order to gain a clear overview of the RC trough bridge population. The second task regards the development of a non-linear finite element model of a typical RC trough bridge named Lautajokki. The model is analysed using ATENA Science and its behaviour is verified against test results obtained during a full-scale test of the bridge performed by Paulsson et al. (1996). The last task is to use the devolved model to perform a parametric study where the effects of changes in load eccentricity, compressive strength as well as tensile strength is studied.

No description available.

Non-stationary signals, particularly frequency modulated (FM) signals which arecharacterized by their time-varying instantaneous frequencies (IFs), are fundamental to radar, sonar, radio astronomy, biomedical applications, image processing, speech processing, and wireless communications. Time-frequency (TF) analyses of such signals provide two-dimensional mapping of time-domain signals, and thus are regarded as the most preferred technique for detection, parameter estimation, analysis and utilization of such signals. In practice, these signals are often received with compressed measurements as a result of either missing samples, irregular samplings, or intentional under-sampling of the signals. These compressed measurements induce undesired noise-like artifacts in the TF representations (TFRs) of such signals. Compared to random missing data, burst missing samples present a more realistic, yet a more challenging, scenario for signal detection and parameter estimation through robust TFRs. In this dissertation, we investigated the effects of burst missing samples on different joint-variable domain representations in detail. Conventional TFRs are not designed to deal with such compressed observations. On the other hand, sparsity of such non-stationary signals in the TF domain facilitates utilization of sparse reconstruction-based methods. The limitations of conventional TF approaches and the sparsity of non-stationary signals in TF domain motivated us to develop effective TF analysis techniques that enable improved IF estimation of such signals with high resolution, mitigate undesired effects of cross terms and artifacts and achieve highly concentrated robust TFRs, which is the goal of this dissertation. In this dissertation, we developed several TF analysis techniques that achieved the aforementioned objectives. The developed methods are mainly classified into two three broad categories: iterative missing data recovery, adaptive local filtering based TF approach, and signal stationarization-based approaches. In the first category, we recovered the missing data in the instantaneous auto-correlation function (IAF) domain in conjunction with signal-adaptive TF kernels that are adopted to mitigate undesired cross-terms and preserve desired auto-terms. In these approaches, we took advantage of the fact that such non-stationary signals become stationary in the IAF domain at each time instant. In the second category, we developed a novel adaptive local filtering-based TF approach that involves local peak detection and filtering of TFRs within a window of a specified length at each time instant. The threshold for each local TF segment is adapted based on the local maximum values of the signal within that segment. This approach offers low-complexity, and is particularly useful for multi-component signals with distinct amplitude levels. Finally, we developed knowledge-based TFRs based on signal stationarization and demonstrated the effectiveness of the proposed TF techniques in high-resolution Doppler analysis of multipath over-the-horizon radar (OTHR) signals. This is an effective technique that enables improved target parameter estimation in OTHR operations. However, due to high proximity of these Doppler signatures in TF domain, their separation poses a challenging problem. By utilizing signal self-stationarization and ensuring IF continuity, the developed approaches show excellent performance to handle multiple signal components with variations in their amplitude levels. / Electrical and Computer Engineering

Ultra-high performance concrete (UHPC) has progressively gained interest because of its favorable strength and durability properties. Literature shows that curing temperature has a significant effect on the resultant mechanical properties of UHPC, generally resulting in increased compressive strength. However, limited datasets are currently available to ascertain the degree of change related to compressive strength as a function of curing temperature and conditions. This study investigates the effect of isothermal and submerged curing temperature conditions, ranging from 10°C to 90°C, on the compressive strength and elastic modulus development of UHPC and generates a numerical model to capture these effects. The extent and rate of compressive strength development in Cor-Tuf UHPC was found to increase with curing temperature, while only the rate of elastic modulus development increased with curing temperature. The numerical model shows reasonable agreement when compared with the experimental results and was successfully implemented in finite element analysis software.

No description available.

Sulfide soils are silty soils, often found in saturated conditions, under the groundwater level. Characteristics of these soils, including particle size distribution and consistency limits along with chemical composition and environmental properties, cause excavation to be necessary for construction purposes. The excavated sulfide soil usually is transported and deposited in landfills. These soils are either deposited in saturated conditions or chemical buffers are added to the soil to prevent acidification. Special conditions of these landfills complicate the disposal procedure and the landfill maintenance which makes those financially expensive. Reusing sulfide soil in construction is a solution to reduce the expenses related to the management of sulfide soils. Since the mechanical properties of these soils are not suitable for construction purposes, the first step is to improve soil characteristics to the level that fulfills the needs of construction applications. One solution to improve the mechanical properties of the soil is adding a binder to the soil. The main focus of the research was to improve the mechanical properties of soil. The research activities were divided into two parts. The first part was conducted in a laboratory environment to develop mixtures, while the second focused on transferring the results to field conditions. The laboratory tests included mixing soil and binder i.e., cement was added to the soil at different percentages to evaluate the soil improvement. An unconfined compressive strength (UCS) test was conducted on the stabilized sample to evaluate the efficiency of the stabilization. The resultsof UCS for the stabilized samples were compared. Since the soil contains a high amount of water, the traditional sample preparation was not suitable. Therefore, an alternative method was developed and evaluated. Moreover, the effect of curing time on the strength and consistency limit of stabilized samples was evaluated. At last, the effect of different variables, including porosity, binder content and initial water content, on the UCS of soil was investigated to identify potential correlation between UCS and different soil variables. The results of the tests showed that adding a binder, regardless of the type of sulfide soil, positively affects the UCS of prepared samples and increasing the curing time increased the UCS of the samples. At higher cement content, the effect of curing time was more significant. Also, it was shown that at higher water content, the effect of binder is lower in comparison with the same soil at lower water content. By lowering the water content, the strength of stabilized soil reaches a maximum and drying further the soil, below the optimum water content, led to strength reduction. A correlation between UCS of sample and porosity/binder ratio was employed to predict the strength behavior of stabilized soil based on variables such as porosity, initial water content and binder dosage. In order to evaluate if laboratory results can be applied to geotechnical applications, the second part of this research included a field mixing experiment for a large-scale mixture of soil and cement. The effect of the mixing procedure with common equipment on the homogeneity of industrial-size mixture was investigated. A sampling strategy for collecting representative samples of mixture was selected and assessed. the number of mixing steps and the effect of binder dosage on the uniformity of samples were studied. Results of UCS of samples prepared from field and laboratory mixture were compared and evaluated. A field evaluation was conducted to determine the quality of the mixture and how many mixing steps are required to reduce variability between samples. Two different percentages of binder were added to the 5 Tons of soil. The UCS test samples were prepared from the soil-cement mixture in the same way as they were prepared in the laboratory and cured for a specific time. The UCS test was conducted on cured samples. The test results were compared to evaluate the mixture homogeneity in the field. The results showed that homogeneous mixtures can be obtained in the field with the available equipment. Assessing the sampling strategy showed that increasing the sampling sections from 5 to 12 and preparing single UCS sample from the collected soil provides representative samples from the soil mixture pile. Additionally, it was shown that by increasing mixing steps from 2 to 3, it was possible to eliminate samples with notable lower strength than average UCS. A greater number of mixing steps improves homogeneity while reducing the average UCS. It was found that mixing soil and binder in the laboratory improves strength better than mixing them in the field. When applying laboratory results to field design, this point must be taken into account.