The purpose of this thesis has been to investigate, both analytically and experimentally, the behaviour of bolted joints in cold formed steel members. To this aim, the influences of all factors bearing a significant effect on behaviour of bolted connections in cold formed steel assemblies and structures have been investigated. Design expressions have been derived. With this information the moment capacity of bolted joints can be calculated with considerably more accuracy than the present existing expressionsin the current codeso f practice. The findings of the thesis have already influenced the design expressions for bearing strength of bolted connections in the European code of practice for design of cold formed steel sections, i. e. Eurocode No 3, Annex A. It is hoped that the conclusions drawn are further incorporated in the above mentioned code, and replace the existing guidelines in the British Standard, BS 5950 Part 5, for the design of such sections. Furthermore for the first time ever, as a result of the analyses and experiments carried out, designers are able to predict the moment-rotation relationship of such connections without having to resort to testing. It is intended to feed this information into design programmes to radically affect the elastic design of cold formed steel structures. It should then be possible to design optimum structures by specifying joints with appropriate characteristics.

The work presented in this thesis is concerned with the effect of shear-bond on the behaviour of profiled steel sheet/concrete composite slabs. A review of the previous work carried out to investigate the influence of shear bond in composite construction and the factors which may affect shear bond resistance is presented and discussed. Also, the different empirical shear-bond equations proposed and design methods for composite slabs are reviewed. A description of push-off and pull-out tests follows and several examples of concrete/profiled steel sheeting units were tested and the results discussed. These small scale tests provided information on the load/slip relationship which was used in the subsequent modelling of the full-scale composite slabs. Fullscale composite slab tests are then considered together with a discussion of results. These are analysed using the regression approach of British Standards and the Eurocode 4. Comparison is made with the design values using the partial interaction method. The comparison indicates that both design methods are valid with the regression approach being slightly more conservative. Finite element methods and their advantages are reviewed and the ANSYS software is introduced together with it's proprietary elements, material models and contact elements. This is followed by a description of three-dimensional finite element modelling of composite slabs (small and full scale). The load versus deflection, and load versus slip provide a comparison between the numerical analysis and test results. The finite element analysis of the composite slabs was successful. The failure load of each slab was modelled satisfactorily using the contact stiffness from the small-scale tests modified by a small percentage (less than 10%). A close correlation between the experimental and finite element analysis predictions for the load/slip and load/deflection behaviour was also obtained. Three-dimensional finite element modelling of embossments with different parameters for the steel sheet and concrete was carried out and conclusions drawn. The general conclusions of the work follows together with recommendations for future research.

The aim of the research reported in this thesis was to improve the understanding of footwear and soft ground interaction and, in particular, its mathematical modelling. The work was undertaken for the Military Footwear Section of the MOD's Defence Clothing and Textiles Agency (DCTA) who funded the research in conjunction with the Engineering and Physical Sciences Research Council (EPSERC). Although research has been carried out on the interaction of footwear on firm surfaces, minimal work has previously been carried out on softer surfaces often encountered in combat situations and little effort has been applied to its mathematical modelling. The research programme included the development of mathematical models using soil mechanics theory, and experimental work using a soft-ground slip-rig. The prototype soft-ground footwear slip-rig that has been developed is a manually operated device based on simple mechanical mechanisms using weights and pulleys. The rig enables the measurement of traction and sinkage for different soil types, sole materials and tread geometry, at various angles of heel contact and applied vertical load. All experimental work has been carried out with the use of scaled up cleats to obtain measurable results. An investigation into three dimensional end effects has determined at what cleat length the problem becomes two dimensional. The experimental results have shown the effects of cleat geometry on total cleat traction for sand, and in particular the geometric characteristics that promote and reduce traction. These results have been analysed using Taguchi's Analysis of Variance technique. Traction distribution experiments have determined the proportion of traction obtained from different cleat areas. Soil mechanics theory, and in particular Coulomb's retaining wall theory, has been applied in the theoretical modelling of footwear and soft ground interaction. A two dimensional total traction model has been developed using MATLAB software and experimental and theoretical results have been compared. The traction versus cleat geometry trends for both the experimental and theoretical results were in good agreement.

A new concept in composite construction has been developed at the University of Salford, involving the use of fibre-reinforced cement channels, combined structurally with partially prestressed composite concrete T-beams. The British Standards Institution Code of Practice, CP110: 1972, "The Structural Use of Concrete", permits the use of Class 2 and Class 3 (partially prestressed) concrete members in structural design'. The limiting design criteria for such members are usually the limit'states of deflection and cracking and therefore, an improvement in their flexural behaviour would be beneficial. This improvement may be brought about by the addition of fibre-reinforcement, in the form of two or three dimensionally randomly distributed fibres. The Code of Practice, CP110: 1972, does hot, however, give any guidance on the use of fibres in structural members and it is also apl. arent that the methods outlined in the code for the calculation of the limit states are limited and can be improved. The flexural behaviour of twenty-two partially prestressed composite concrete T-beams was investigated. Each beam consisted of a precast partially prestressed X-joist web, combined with a cast-insitu lightweight aggregate concrete flange. Alkali-resistant glass fibrereinforced cement channels were placed at the soffits of six beams and steel fibre-reinforced concrete was used in the webs of two beams. The T-beams were subjected toshort-term, long-term and fatigue loading and their structural performance was considered in terms of strength, cracking and deformation. Theoretical relationships are derived between the applied moment and the depths of the neutral axes of stress and bending, enabling a design equation relating applied moment to the steel stress to be developed. Subsequently, design equations for the calculation of the limit states of deflection and cracking are developed, which are directly applicable to both conventional and fibre-reinforced structural members. The use of a fibre-reinforced cement channel as an integral structural part of a concrete member results in many important advantages when compared with conventional concrete members and the test results show that they considerably improve the structural performance of the partially prestressed composite concrete T-beams.

Mith their unique transparent and conductive properties, TCO (transparent conductive oxide) coatings are becoming increasingly studied These commercially important coatings have a promising future due to their various applications as components in optoelectronic devices, photovoltaic solar cells, flat panel displays, electroluminescent devices, etc. Their high transmittance and low resistivity are generally achieved through the use of specific dopant materials, whilst adjustments are made to the deposition processes to improve the structure of the coatings. TCO coatings are commonly deposited by the magnetron sputtering process. Sputtering normally takes place from a solid plate, known as the target, of the material to be deposited. Clearly, each solid target can only be of a single composition. Thus, to change the compositions ofthe coatings, the whole target has to be replaced Furthermore, alloy, or doped targets can be very expensive and the choice ofavailable compositions is likely to be limited. In this project, instead of using solid targets, metal or ceramic powder blends were used as the targets. The powder blends were spread across the surface of a magnetron and lightly tamped down to produce a smooth surface. The benefits of this approach are that any material that is available in powderform can be considered as a target material and alloy or multi-component compositions can be readily blended The basic aim of this project, therefore, was to produce novel TCO coatings by magnetron sputteringfrom powder targets. The coatings were deposited in a specially designed rig with a number of important features, including a pulsed DC power supply and a closed magnetic field. The project concentrated on the production of commercially useful zinc oxide-based TCO coatings. Coatings were produced with different dopant materials and concentrations, and their optical and electrical properties were measured. After the coatings were annealed at 500 *Cfor 2 hours in vacuo, aluminum and gallium doped zinc oxide coatings showed their low resistivity, which were no larger than 5.19xI0-3S2cm, and the lowest resistivity was obtained from 3at% A 1-doped ZnO coating; 1.95 xI 00cm. The average transmittance in the visible range of the ZnO coatings was 90%. From this, optimal compositions were identified For comparison purposes, coatings were also produced of the TCO material most commonly used at present; namely ITO (Indium tin oxide). The results showed that ITO coatings generally had lower resistivity and visible transmittance, (4-6xlO-492cm and 80-8216), than doped ZnO coatings. Also, the electrical and optical properties of ITO coatings were very sensitive to the content of oxygen in the deposition atmosphere. Finally, theflexibility offered by this approach was exploited through the use of multi-component target compositions to produce TCO coatings with tailored optical and electrical properties.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

The fields of nanomaterial and nanostructures are some of the fastest growing fields in material science today. Carbon nanotubes are at the forefront of these fields and their unique mechanical and electrical properties are of great interest to those working in multiple engineering fields. The overall objective of this study was to design and develop a new process and the equipment necessary, to synthesize carbon nanotubes using high voltage and a high-frequency induction field. This was the first time that a high voltage and an induction field have been used simultaneously in high yield production of carbon nanotubes. The source of carbon came from acetylene with cobalt used as the doping agent. The carbon was molded into carbon nanotubes by the high-voltage field. The carbon nanotubes were characterized using electron microscope techniques. Raman spectroscopy was also used to reveal the defects and graphitic structures of the carbon nanotubes.

Quantum coherence plays a vital role in the excitonic properties of organic semiconductors. Several theoretical and experimental studies have shown an unprecedented role of coherence in charge transfer and transport processes, which in turn can improve the performance of electronic devices. Specifically, an enhancement of exciton coherence size can result in fast energy transport and efficient charge separation. The ability to tailor the design and performance of organic electronics based on exciton coherence effects represents the possibility of ultrafast electronic applications in communication and information technology. The objective of this thesis is the excitonic coherence studies of 1D crystalline thin films of phthalocyanine-based organic semiconductors using steady-state and time-resolved photoluminescence spectroscopy (TRPL). One of the main focuses of this work is on investigating the correlation of intermolecular interactions, $\pi$ orbital overlap and dynamic disorders on the excitonic coherent behaviors in crystalline thin films of various phthalocyanine derivatives (i.e. H$_2$TPP, H$_2$OBPc, H$_2$OCPc, and H$_2$OBNc). Specifically, coherence lengths, exciton-phonon coupling strengths and the nearest neighbor (NN) interaction strengths are determined via: (1) the PL ratio of the excitonic coherence transition and its first vibrational replica and (2) the temperature evolution of radiative recombination lifetimes of coherent excitons. This study showed that the optimum coherence size and the robustness of excitonic coherence can be achieved by a complex interplay between NN interaction, vibrational energies and the coupling to vibrational modes. In particular, it is shown that the shortest NN distance does not ensure the achievement of maximum coherence length within the four investigated phthalocyanine species. Instead, the largest coherence length is measured in the octabutoxy derivative, where the saddle shape of the molecule and crystalline packing results in weaker coupling to the acoustic phonons modes despite having larger intermolecular NN distance. In addition, the effect of static and dynamic disorders on the behavior of exciton coherence is explored by alloying two phthalocyanine derivatives that are close in band gap energies and possess large coherence lengths, H$_2$OBPc and H$_2$OBNc. This study demonstrated the successful tuning of exciton coherence lengths and excitonic parameters in organic analogues of semiconductor alloys, H$_2$OBNc$_x$H$_2$OBPc$_{1-x}$. Furthermore, the correlation of exciton-phonon coupling and radiative recombination rate of coherent excitons with increasing alloy concentration or static disorders are successfully revealed.

This investigation represents a comparative study of the flexural behavior of lightweight and normal weight concrete. Both theoretical and experimental moment-curvature characteristics of the tested specimens were used to study the flexural behavior. A generalized computer program to determine the moment-curvature relationships of a singly reinforced rectangular concrete beam was developed. For this limited study it was observed that lightweight concrete beams when compared to normal concrete beams achieve comparable moment capacity (about 92% of normal weight concrete) but exhibit higher deflections (about 40% more than normal weight concrete).

This study was directed toward the development of a bistable wall attachment Flip-Flop device which was capable of directionally controlling particle flow. The particles were transported by a fluid stream which under the influence of wall attachment. The dominant criteria in the development of the device was the achievement of the highest recovery of particles at the active output, without destroying the wall attachment of the fluid stream The experiment was conducted in several distinct stages; each of which was concerned with at least one aspect of wa1l attachment or particle flow. Results derived from one test were used to develop the criteria for the next experimental arrangement. Two experimental models were constructed: one of plywood with only one attachment wall, and one of plexiglas which had two attachment walls and was bistable. The plywood model was used in testing wall attachment and particle recovery as a function of the attachment wall angle. From these tests it was concluded that the optimum wall angle was 18 degrees from the center line of the device. Observations of particle action in the plywood model led to the incorporation of additional features in the plexiglas model. They were: an extended nozzle, the elimination of the separation bubble, and the development of smooth transitions at the corners. The plexiglas model was used to investigate optimum splitter location, the effect of jet velocity on recovery efficiency, the effect of vents on the performance of the device, and the performance of the device using a water jet. In the last stages of testing, moving parts and additional output features were used in conjunction with the bistable device to improve the collection efficiency. Some observations resulting from the data gathered in the various tests include: 1. The higher the jet velocity, the greater the wall attachment. 2. The higher the density and viscosity of the fluid stream the greater the recovery of particles at the active output. 3. Particles with large inertial forces were controlled less by the attached jet stream. The addition 0f vents in the device may produce greater particle recovery. 5. The use of moving parts and variations in the output leg design can produce 100 percent particle recovery. This study indicated that it was possible to control the directional flow of particles with the bistable wall attachment device which was developed. However, the pure fluid bistable device could not achieve 100 percent recovery of particles. The addition of moving parts or variations in the output leg design can produce 100 percent recovery of the particles. The use of a bistable device could provide simplicity, reliability and adaptability in transporting materials for industrial processes.