This thesis investigates a parametric study of a flat plate floor system designed using post-tensioning. The load balanced by the post-tensioning, the slab depth, and the strength of concrete were varied to create the parametric study of a hotel/condominium grid layout. In order to perform the parametric study, research was conducted on the development of post-tensioning, methods of analysis for two-way slab design, and post-tensioning methods of analysis. Design was conducted by hand through a series of Excel spreadsheets and compared to results found using the computer analysis program, ADAPT-PT. The designs found in the parametric study were then used to perform a cost analysis across ten cities in the United States: Atlanta, Boston, Chicago, Denver, Houston, Los Angeles, Miami, Phoenix, San Francisco, and Seattle. The designs from the hand analysis and the ADAPT-PT model provided similar results for the post-tensioning, and both methods provide an adequate design. The use of ADAPT-PT is recommended because of its ease of use and quick calculation capabilities. The designs of the hand analysis were quantified and along with unit prices gathered from contractors and suppliers the cost analysis found that the design with 100% of the dead load balanced provided the least expensive solution for all the cities, and the design using a 6000 psi strength concrete provide the most expensive solution for all cities. The least expensive slab design was $9.02 per square foot in Atlanta, Georgia, and the most expensive slab design was $24.96 per square foot in Miami, Florida. A more rigorous parametric study in the future may provide a better optimization for the hotel/condominium slab investigated as the parametric study of this thesis found costs which varied by less than 10% between the most expensive and least expensive slabs in the ten cities.

This paper presents the axial compressive behaviour of stub concrete-filled columns with elliptical stainless steel and carbon steel hollow sections. The finite element method developed via ABAQUS/Standard solver was used to carry out the simulations. The accuracy of the FE modelling and the proposed confined concrete stress-strain model were verified against experimental results. A parametric study on stub concrete-filled columns with various elliptical hollow sections made with stainless steel and carbon steel was conducted. The comparisons and analyses presented in this paper outline the effect of hollow sectional configurations to the axial compressive behaviour of elliptical concrete-filled steel tubular columns, especially the merits of using stainless steel hollow sections is highlighted.

Technological advances require novel solutions for contactless energy transfer. Many engineering applications require unique approaches to power electrical components without using physical wires. In the past decade, awareness of the need to wirelessly power electrical components spawned many forays into the field of wireless power transfer (WPT). WPT techniques include capacitive energy transfer, electromagnetic inductive power transfer, electromagnetic radiative power transfer, electrostatic induction, and acoustic energy transfer. Acoustic energy transfer (AET) has many advantages over other methods. These advantages include lower operating frequency, shorter wavelengths enabling the use of smaller sized receiver and transmitter, extended transmitter-to-receiver distance therefore more manageable design constraints, achieving lower attenuation, higher penetration depth, and no electromagnetic losses. Most AET systems operate in the ultrasonic frequency range and are more commonly referred to as ultrasonic acoustic energy transfer (UAET) systems. Through-wall UAET systems are constructed of a transmitter bonded to a transmission elastic layer, which in turn is bonded to a receiver. The transmitter and receiver layers are constructed of a piezoelectric material. Piezoelectric materials behave according to the piezoelectric effect, which is when a material generates an electric charge in response to mechanical strain. The transmitter utilizes the reverse of the piezoelectric effect. A sinusoidal input voltage is applied to the transmitter, inducing vibrations in the transmitter. The vibration-induced acoustic waves emanating from the transmitter travel through the initial bonding layer, the transmission layer, and the final bonding layer to the receiver. In turn, the acoustic waves cause the receiver to deform and undergo strain. This induces a flow of charge in the receiver, which is an electric current. The receiver feeds current to a resistive load. In this manner, energy is acoustically transferred between two transducers without wires. The performance of UAET systems can be evaluated based on power transfer efficiency, voltage magnification, and input admittance. UAET systems require extensive modeling before experimental assembly can be attempted. The analytical models of UAET are either based on the mechanics of the constitutive relations of piezoelectricity and solid mechanics or using equivalent circuit methods. The equivalent circuit method approximates the physics of the UAET system with electrical assumptions. The mechanics-based method is the most comprehensive description of the physics of all the intermediate layers in a UAET system. The mechanics-based method has been based on the assumption that the UAET system is operated in the thickness mode of vibration, i.e., piston-like vibration mode where the transmitter and receiver disks vibrate only in the thickness direction. This poses an issue for disks with aspect ratios between 0.1 and 20 because the piezoelectric transducers vibrate in both the radial and thickness modes. In addition to this assumption, most of the works on UAET models only have accounted for the piezoelectric and transmission layers. The effects of the bonding layers were not considered. Bonding the piezoelectric layers to the transmission layer introduces epoxy material with mechanical properties that are not accounted for. The epoxy layers are extra barriers to the transmission that introduce attenuation and alter the vibrational and acoustical behaviors of the UAET system. Investigations into UAET commonly focus on metal through-wall applications. Alternate transmission layer materials are not investigated and the impact of varying mechanical properties on the performance of a through-wall UAET system has not been comprehensively studied. Even with the metal transmission layers, the impact of the metal thickness has not been extensively investigated thoroughly. This work addresses the issues of the thickness-mode assumption in UAET modeling, the effects of epoxy layers, the impacts of the metal layer geometry, and the performance of UAET systems with alternate transmission layer materials. Particularly, (1) we showed that the thickness-mode assumption, that has been used in the UAET modeling leads to inaccurate results. (2) We modified the available acoustic electro- elastic theoretical modeling to include the effects of radial modes as well as the epoxy bonding layers. (3) We showed that the geometry of the elastic/metal layer requires optimization for peak system efficiency. (4) The results show that using alternate transmission layer materials impacts the performance of UAET systems. The results of this work were investigated using an improved 5-layer analytical model and finite element modeling in COMSOL Multiphysics. / Master of Science / Wireless power transfer (WPT) is an innovative solution to the problem of powering sophisticated technological applications. Such instances include the powering of implanted medical devices, recharging inaccessible sensor networks, and wireless powering of components in sealed containers. Acoustic energy transfer (AET) is a feasible WPT method that addresses these needs. AET is based on the propagation of acoustic waves to a piezoelectric receiver which converts the vibrations caused by incident acoustic waves into electrical energy. Most AET systems operate in the ultrasonic frequency range, and so AET can also be referred to as ultrasonic acoustic energy transfer (UAET). Through-wall UAET systems are constructed from a transmitter that is bonded to a transmission elastic layer. The transmission layer is bonded to a receiver. The transmitter and receiver are made of a piezoelectric material. This thesis addresses the modeling process of through-wall UAET systems. In previous works, the fundamental assumption has been that such systems vibrate purely in the thickness mode. Additionally, other investigations did not comprehensively analyze the effects of the bonding layers, ascertain the performance of non-metal transmission layers, or provide practical insight on the effect of the resistive loading on such systems. This work addresses all these issues with a mathematical framework and finite element modeling results.

Most of the today’s concrete structures are older than tenyears, and the need to strengthening existing structures is growing steadily. This is due to various reasons such as degradation due to ageing, environmentally induced degradation, poor initial design or construction and lack of maintenance, to name a few. Among the benefits of strengthening existing structures are; less impacts on the environmental and financial benefits. Therefore, there is a need to find alternative ways to strengthen concrete structures more effectively. For the past decades, several different strengthening methods have been studied. Two examples are externally bonded reinforcement (EBR) and near surface mounted reinforcement (NSM). The outcome of these studies has shown a significant enhancement to the structures. Steel plates and rebar have been used to strengthen concrete structures and have shown good increases in flexural capacity. For this purpose, resins have been used to implement the steel plates and rebar, e.g. shotcrete and epoxy. Due to the weight of steel and its sensitivity to corrosion, new materials have been sought. A promising material for this use is the fiber reinforced polymers (FRP). There are several types of FRP such as, carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP) and aramid fiber reinforced polymer (AFRP). These new material has shown a better performance, due to their light weight, resistance to corrosion,etc. NSM and EBR perform extremely well in practice as long as sufficient anchorage is provided. However, a premature debonding has been observed by several researchers. This report will study an alternative method to reinforce existing concrete structures called “Side Near Surface Mounted Reinforcement (S-NSMR)” in association with a project run by Gabriel Sas at Luleå University of Technology. This is compared to Bottom Near Surface Mounted Reinforcement (B-NSM), which is a well-established method. It is assumed that the fiberutilisation will increase in NSM applied on the side of the beam. If this hypothesis is proven correct, the proposed method will also solve a major constrain in the utilisation of the NSM technique. In certain cases, the bottom of a beam is not fully accessible for strengthening using bottom Applied NSM techniques due to e.g. partition walls or beam-column joints. To test the effect of S-NSMR seven concrete beams, one reference beam with no fiberreinforcement and two sets of three, for S-NSMR and B-NSMR respectively with different CFRP-rebar length, were tested in the laboratory. An analytical calculation has also been carried out. In this thesis, a parametric study is performed with FEM software Atena. The thesis begins with a study of the failure phenomena occurring in the earlier mentioned strengthening method. A benchmark model is then modelled with a good comparison to the experimental results. An idealised model of the steel reinforcement in the concrete beam is used according to Eurocode 2. Material parameters in concrete are calculated according to Atena theory documents. The influence of creep and shrinkage are considered by reducing the elastic modulus of concrete by 25 %, reducing the tensile strength by 50 % and fracture energy accordingly. Thereafter, three additional parameters were chosen to continue the parametric study with Atena, 1) CFRP with E-modulus 160 GPa, 2) two different position in cross-section height of S-NSM and 3) five shorter CFRP-rebar each 100 mm smaller than the previous rebar. The behaviour of the two reinforcing types is then compared. The first parameter is, CFRP with a smaller E-modulus. It could be observed that all beams lost their stiffness, especially after yielding of the steel reinforcement. A small improvement in ductility could also be observed. The utilisation rate of CFRP increased by 13-16% in the case of S-NSM and 18-20% in the case of B-NSM. The second parameter is, different position of CFRP along the height of the beams cross-section in S-NSM beams. The positions of the CFRP was lowered in two steps. In each case an increase in stiffness and a decrease in ductility could be observed. However, the increase of the stiffness was still smaller than the stiffness in the B-NSM, in all cases. The failure mode changed from a ductile (concrete crushing) type to a more brittle kind (peeling-off concrete), due to large flexural cracks at the end of the CFRP-rebar.   The utilisation rate of CFRP-rebar, is decreased in each S-NSM beam except for S-NSM 2 with the height 25 mm. The reduction in the utilisation rate of the CFRP is 7-32 % and in S-NSM 2 with the height H25mm showing an increased in utilisation rate by 7 %. The third is parameter, different length of CFRP-rebar. In the case of S-NSM, the failure mode changed from a ductile failure mode to a brittle failure mode. The utilisation rate decreased with the decrease in CFRP length. In three of five cases, the S-NSM shows a higher ultimate load-displacement relation, and in all five cases the maximum tensile strains in the CFRP were higher in S-NSM than B-NSM. Even though the stiffness in the S-NSM is lower than the B-NSM, it would be more preferable to use the S-NSM than B-NSM, because of its higher ultimate load and lower displacements.

Ce travail de thèse concerne l’utilisation des décharges électriques de haute tension (DEHT) en milieu aqueux comme méthode d’extraction des polyphénols à partir de pépins de raisin.Les arcs électriques produits en milieu aqueux provoquent une succession de phénomènes (ondes de choc, bulles de cavitation) qui ont pour effet de fragmenter toute matière première située à proximité de l’arc électrique. L’objectif de cette thèse est d’étudier ces phénomènes afin d’améliorer la compréhension et l’efficacité des DEHT en tant que méthode d’extraction.Dans un premier temps, une étude des conditions d’apparition de l’arc électrique dans l’eau a permis de montrer que l’arc apparaît initialement dans des bulles de vapeur générées à la surface de l’électrode à cause de l’échauffement du liquide par effet Joule. Des mesures électriques, des prises de vues à haute vitesse, ainsi qu’une simulation numérique du problème ont permis de vérifier cette hypothèse. Une étude paramétrique des phénomènes générés par l’arc électrique (onde de choc et bulle de cavitation) a été menée. Grâce à des mesures de la pression des ondes de choc, des mesures de la taille des bulles de cavitation, et grâce des mesures électriques précises (notamment de la résistance électrique de l’arc), il apparaît que l’amplitude des phénomènes dépendent essentiellement de l’énergie dépensée dans l’arc. Cette énergie doit être distinguée de l’énergie totale d’une impulsion électrique, dont une partie est dépensée avant le claquage, mais également de l’énergie disponible au moment du claquage, dont une partie importante est dépensée dans le circuit électrique. La partition de cette énergie entre l’arc et le circuit électrique dépend du rapport entre la résistance du circuit et la résistance de l’arc. Ainsi une méthode pour augmenter significativement l’amplitude des phénomènes étudiés, et donc l’efficacité du procédé est d’améliorer le rapport entre ces résistances. Il a par exemple été observé qu’en augmentant la longueur de l’arc électrique de 2.5 mm à 2 cm, la résistance de l’arc augmente de 40 m à 0.55, et l’amplitude de l’onde de choc augmente de 135%. Pour finir, une étude paramétrique sur l’efficacité des DEHT comme procédé d’extraction des polyphénols des pépins de raisin a été menée. Entre autres, les effets sur l’extraction de la conductivité du liquide, du rapport liquide-solide, du nombre d’impulsion, de l’énergie par impulsion, de la distance inter-électrode ont été étudiés. Ces études ont mis en évidence l’importance de la répartition de l’énergie totale d’une impulsion en énergie dépensée avant le claquage, énergie dépensée au claquage dans le circuit électrique et énergie dépensée dans l’arc électrique. Ces études ont montré comment cette répartition est influencée par ces différents paramètres, et comment cela influence l’efficacité d’extraction. L’influence de la distance inter-électrode, et donc de la longueur de l’arc, a été particulièrement été mise en évidence par les résultats d’extraction. / This thesis work focuses on the use of high voltage electrical discharges (HVED) in aqueous media as a method for extracting polyphenols from grape seeds. Electric arcs generated in an aqueous environment cause a succession of phenomena (shock waves, cavitation bubbles) that have the effect of fragmenting any raw material located near the electric arc. The objective of this thesis is to study these phenomena in order to improve the understanding and effectiveness ofHVED as an extraction method. First, a study of the conditions under which the electric arc appears in water showed that the arc initially appears in vapour bubbles generated on the electrode surface due to the heating of the liquid due to Joule effect. Electrical measurements, high-speed photography and a numerical simulation of the problem have allowed this hypothesis to be verified. A parametric study of the phenomena generated by the electric arc (shock wave and cavitation bubble) was carried out. Through measurements of shock wave pressure, of cavitation bubble size, and precise electrical measurements (including the electrical resistance of the arc), it appears that the amplitude of the phenomena depends essentially on the energy consumed in the arc. This energy mustbe distinguished from the total energy of an electrical pulse, part of which is spent before the breakdown. The energy spent in the electric arc must also be distinguishedfrom the energy available at electrical breakdown, as a significant part of breakdown energy is spent in the electrical circuit. The partition of breakdown energy between the arc and the electrical circuit depends on the ratio between the resistance of the circuit and that of the arc. Thus a method to significantly increase the amplitude of the studied phenomena (and therefore the efficiency of the process), is to improve the ratio between these resistances. For example, it has been observed that by increasing the length of the electric arc from 2.5 mm to 2 cm, the resistance of the arc increases from 40 m to 0.55, and the amplitude of the shock wave increases by 135%. Finally, a parametric study on the efficiency of DEHT as a process for extracting polyphenols from grape seedswas carried out. Among other things, the effects on the extraction of liquid conductivity, liquid-solid ratio, number of pulses, energy per pulse, and distance between electrodes were studied. These studies highlighted the importance of the distribution of the total pulse energy into energy spent before the breakdown, energy spent after breakdown in the electrical circuit and energy spent in the arc. These studies have shown howthis distribution is influenced by these different parameters, and how it influences extraction efficiency. The influence of the inter-electrode distance, and therefore the length of the arc, was particularly highlighted by the extraction results.

Solid oxide fuel cells (SOFCs) are solid-state ceramic cells, typically operating between 1073 K and 1273 K. Because of high operating temperature, SOFCs are mostly applicable in stationary power generation. Among various configurations in which SOFCs exist, the planar configuration of solid oxide fuel cell (SOFC) has the potential to offer high power density due to shorter current path. Moreover, the planar configuration of SOFC is simple to stack and closely resemble the stacking arrangement of polymer electrolyte membrane (PEM) fuel cells. However, due to high operating temperature, there are problems associated with the development and commercialization of planar SOFCs, such as requirement of high temperature gas seals, internal stresses in cell components, and high material and manufacturing costs. Mathematical modeling is an essential tool for the advancement of SOFC technology. Mathematical models can help in gaining insights on the processes occurring inside the fuel cell, and can also aid in the design and optimization of fuel cells by examining the effect of various operating and design conditions on performance. A multi-component and multi-dimensional mathematical model of SOFCs has been developed in this thesis research. One of the novelties of the present model is its treatment of electrodes. An electrode in the present model is treated as two distinct layers referred to as the backing layer and the reaction zone layer. Reaction zone layers are thin layers in the vicinity of the electrolyte layer where electrochemical reactions occur to produce oxide ions, electrons and water vapor. The other important feature of the present model is its flexibility in fuel choice, which implies not only pure hydrogen but also any reformate composition can be used as a fuel. The modified Stefan-Maxwell equations incorporating Knudsen diffusion are used to model multi-component diffusion in the porous backing and reaction zone layers. The coupled governing equations of species, charge and energy along with the constitutive equations in different layers of the cell are solved for numerical solution using the finite volume method and developed code written in the computer language of C++. In addition, the developed numerical model is validated with various experimental data sets published in the open literature. Moreover, it is verified that the electrode in an SOFC can be treated as two distinct layers referred to as the backing layer and the reaction zone layer. The numerical model not only predicts SOFC performance at different operating and design conditions but also provides insight on the phenomena occurring within the fuel cell. In an anode-supported SOFC, the ohmic overpotential is the single largest contributor to the cell potential loss. Also, the cathode and electrolyte overpotentials are not negligible even though their thicknesses are negligible relative to the anode thickness. Moreover, methane reforming and water-gas shift reactions aid in significantly reducing the anode concentration overpotential in the thick anode of an anode-supported SOFC. A worthwhile comparison of performance between anode-supported and self-supported SOFCs reveals that anode-supported design of SOFCs is the potential design for operating at reduced temperatures. A parametric study has also been carried out to investigate the effect of various key operating and design parameters on the performance of an anode-supported SOFC. Reducing the operating temperature below 1073 K results in a significant drop in the performance of an anode-supported SOFC; hence ionic conductivity of the ion-conducting particles in the reaction zone layers and electrolyte needs to be enhanced to operate anode-supported SOFCs below 1073 K. Further, increasing the anode reaction zone layer beyond certain thickness has no significant effect on the performance of an anode-supported SOFC. Moreover, there is a spatial limitation to the transport of oxide ions in the reaction zone layer, thereby reflecting the influence of reaction zone thickness on cell performance.

Solid oxide fuel cells (SOFCs) are solid-state ceramic cells, typically operating between 1073 K and 1273 K. Because of high operating temperature, SOFCs are mostly applicable in stationary power generation. Among various configurations in which SOFCs exist, the planar configuration of solid oxide fuel cell (SOFC) has the potential to offer high power density due to shorter current path. Moreover, the planar configuration of SOFC is simple to stack and closely resemble the stacking arrangement of polymer electrolyte membrane (PEM) fuel cells. However, due to high operating temperature, there are problems associated with the development and commercialization of planar SOFCs, such as requirement of high temperature gas seals, internal stresses in cell components, and high material and manufacturing costs. Mathematical modeling is an essential tool for the advancement of SOFC technology. Mathematical models can help in gaining insights on the processes occurring inside the fuel cell, and can also aid in the design and optimization of fuel cells by examining the effect of various operating and design conditions on performance. A multi-component and multi-dimensional mathematical model of SOFCs has been developed in this thesis research. One of the novelties of the present model is its treatment of electrodes. An electrode in the present model is treated as two distinct layers referred to as the backing layer and the reaction zone layer. Reaction zone layers are thin layers in the vicinity of the electrolyte layer where electrochemical reactions occur to produce oxide ions, electrons and water vapor. The other important feature of the present model is its flexibility in fuel choice, which implies not only pure hydrogen but also any reformate composition can be used as a fuel. The modified Stefan-Maxwell equations incorporating Knudsen diffusion are used to model multi-component diffusion in the porous backing and reaction zone layers. The coupled governing equations of species, charge and energy along with the constitutive equations in different layers of the cell are solved for numerical solution using the finite volume method and developed code written in the computer language of C++. In addition, the developed numerical model is validated with various experimental data sets published in the open literature. Moreover, it is verified that the electrode in an SOFC can be treated as two distinct layers referred to as the backing layer and the reaction zone layer. The numerical model not only predicts SOFC performance at different operating and design conditions but also provides insight on the phenomena occurring within the fuel cell. In an anode-supported SOFC, the ohmic overpotential is the single largest contributor to the cell potential loss. Also, the cathode and electrolyte overpotentials are not negligible even though their thicknesses are negligible relative to the anode thickness. Moreover, methane reforming and water-gas shift reactions aid in significantly reducing the anode concentration overpotential in the thick anode of an anode-supported SOFC. A worthwhile comparison of performance between anode-supported and self-supported SOFCs reveals that anode-supported design of SOFCs is the potential design for operating at reduced temperatures. A parametric study has also been carried out to investigate the effect of various key operating and design parameters on the performance of an anode-supported SOFC. Reducing the operating temperature below 1073 K results in a significant drop in the performance of an anode-supported SOFC; hence ionic conductivity of the ion-conducting particles in the reaction zone layers and electrolyte needs to be enhanced to operate anode-supported SOFCs below 1073 K. Further, increasing the anode reaction zone layer beyond certain thickness has no significant effect on the performance of an anode-supported SOFC. Moreover, there is a spatial limitation to the transport of oxide ions in the reaction zone layer, thereby reflecting the influence of reaction zone thickness on cell performance.

In this study, the seismic fragility assessment of low-rise and mid-rise reinforced concrete frame buildings which constitute approximately 75 % of the total building stock in Turkey is investigated to quantify the earthquake risk. The inventory used in this study is selected from D&uuml / zce damage database which was compiled after the devastating 1999 earthquakes in the Marmara region. These buildings are not designed according to the current code regulations and the supervision in the construction phase is not adequate. The building database is divided into sub-classes according to the height and absence of infilled walls. Each building in the database is represented by an equivalent single degree of freedom system with three structural parameters: period, strength, and post-elastic stiffness ratio. The ground motion records are selected from different parts of the world covering a wide range of characteristics. The capacity of the structure is represented for each sub-class by the limit states. Hence, a set of fragility curves for low- and mid-rise reinforced concrete structures are developed by making use of the building characteristics in the database. The generated fragility curve set is referred as &ldquo / reference&rdquo / since it forms the basis of a parametric study. A parametric study is conducted to examine the influence of post-elastic stiffness ratio, simulation and sampling techniques, sample size, limit state definition and degrading behavior on the final fragility curves. Estimated damage distribution after two consecutive major earthquakes is compared with the actual field data in order to investigate the validity of the generated fragility curves.

The trend of structural engineering in the recent years is toward the use of lighter and moreeconomical structural elements. In steel construction, peculiarly, thin-walled structural elements arebecoming more popular and have a growing importance. Improved techniques in a manufacturing ofthin-walled elements have led to increased competitiveness of such products in the buildingapplications. Some examples of such structural element can be found in everyday life in form ofcolumns, studs, roofing trusses, and light-weight frames. However, the use of slender profiles and acomplex cross sections shape lead to requirements to study instability phenomenon in a form of local,distortional, flexural, torsional and coupled instability. Such complex structural behavior is inevitablyaccompanied by demand to improve calculation methods and design provisions. In this thesis, aninnovative solution of structural element composed of thin-walled plates is proposed for theapplication on lattice support structure of wind turbine.Thin-walled cold-formed profiles are steel products usually made from cold rolled coils and folded inthe second step. In this way, only open profiles can be produced. The predominant problem of theopen cross-section is the excessive torsional effect caused by the non-coincidence between the shearcenter and mass center, and a poor torsional resistance. A better response is possible with closed crosssections, but such profiles could not be produced by the folding. The solution is to make semi-closedsection by assembling them into polygonal profiles with mechanical fasteners, as presented in thisthesis.Objective of this work is to study the proposed structural sections in design situation and toinvestigate possible design models. The expected structural behavior of the column is a mixturebetween the open and closed cross-section. These cases will be investigated through numerical study.In this thesis presented a comprehensive parametric study on the ultimate strength of proposed coldformedsteel columns using the Finite Element package ABAQUS. FE models were first developedfor columns by using automation that was made through MATLAB and Python script. The bucklingand non-linear FE study was done for the investigation of local (L), distortional (D) and global (G)possible buckling failures and ultimate resistance, respectively. Modelling issues such as boundaryconditions, meshing, initial imperfections, material models, and non-linear solution controls in FEAwere also addressed.The parametric study involved series of profiles of built-up polygonal cross-section types with variedthickness (t), number of corners (n), diameter (d), slenderness (slend), yield strength (fy), number ofpoints along corner radii (np), extension lip length (lext), gusset plate thickness (tg), member length (l),and density of fasteners (s/d ratio), loaded in compression and bending moment. The bending momentoccurs as the effect of forces acting on the connection. The purpose of this analysis is to study thecritical load, cross-sectional behavior, influence of the amplitude of initial imperfections on theultimate load, and influence of each parameter used in the analysis through Full Factorial Design.

Brake squeal is an old and well-known problem in the vehicle industry and is a frequent source for customer complain. Although, brake squeal is not usually affecting the performance of the brakes, it is still important to address the problem and to predict the brakes tendency to squeal on an early stage in the design process. Brake squeal is usually defined as a sustained, high-frequency vibration of the brake components, due to the braking action. By using simulation in finite element (FE) method it should be possible to predict at what frequencies the brakes tend to emit sound. The method chosen for the analysis was the complex eigenvalues analysis (CEA) method, since it is a well-known tool to predict unstable modes in FE analysis. The results from the CEA were evaluated against measured data from an earlier study. Even though there are four main mechanism formulated in order to explain the up come of squeal, the main focus in this project was modal coupling, since it is the main mechanism in the CEA. A validation of the key components in model was performed before the analysis, in order to achieve better correlation between the FE model and reality. A parametric study was conducted with the CEA, to investigate how material properties and operating parameters effected the brakes tendency to squeal. The following parameters was included in the analysis; coefficient of friction, brake force, damping, rotational velocity, and Young’s modulus for different components. The result from the CEA did not exactly reproduce the noise frequencies captured in experimental tests. The discrepancy is believed to mainly be due to problems in the calibration process of the components in the model. The result did however show that the most effective way to reduce the brakes tendency for squeal was to lower the coefficient of friction. The effect of varying the Young’s modulus different components showed inconsistent results on the tendency to squeal. By adding damping one of the main disadvantages for the CEA, which the over-prediction of the number of unstable modes, where minimized.