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The objective of this thesis is the development of an exhaust gas system concept for diesel engines that meets the present and future challenges of exhaust gas aftertreatment of nitrogen oxides at low exhaust gas temperatures. Previous studies on this topic have mainly focused on the optimisation of the currently used exhaust gas aftertreatment systems. This thesis starts one step earlier. In the first part of this thesis – the concept development phase – the objectives and boundary conditions for the development of an exhaust gas system for low temperatures will be established. The result will show that the efficiency of the exhaust gas aftertreatment at low exhaust temperatures, as well as in the entire engine map range, depends in particular on the provision of reducers (substances required for the conversion of NOX into N2) and on the homogeneity of these reducers on the SCR catalyst. Based on these results, the physical principles with which the reducers can be optimally provided for the conversion process will be investigated. Three principles will be identified: Process before injection, Process during injection, and Process after injection. In the following step, these established principles will be discussed in terms of advantages and disadvantages, which will then be compiled by means of a literature search and evaluated using VDI guideline 2225. The result will show that the introduction of the reducers on the basis of the process during injection (using a heated injector) is the most suitable solution. Based on this finding, the components of the exhaust gas system relevant for the adaption of the heated injection (injector, mixer and mixing section) will be identified. In a further analysis stage, it will be investigated and determined which configuration of these components (e.g. exhaust gas system near the engine or underbody system) will be used for the following test series. Subsequently, these components will be modified for the heated injection process. The exhaust gas concept system will then be designed in CAD. Finally, the concept system will be built in hardware. The second part of the thesis – the experimental phase – will comprise several test series on different test benches. The thermodynamic principles and boundary conditions of the heated spray process will be identified and the required parameters for the test bench trials will be derived. Subsequently, in an initial test series, the heated injector will be measured on an optical test bench. The aim will be to determine the fundamental spray properties, to validate the previously identified parameters, and to compare the test results to the literature. During this series of tests, the required parameters for the subsequent test series on the engine test bench will also be determined. The result will be that the expected spray behaviour will be achieved and a fine spray will be produced, which also shows an increasing gas content with increasing injection temperature. The subsequent test series on the engine test bench will cover the entire concept exhaust gas system. The aim of these test series will be to analyse the factors that determine the efficiency of the exhaust gas system, as identified in the first part of this thesis. These are the provision of reducers, which can be measured by the degree of conversion of the nitrogen oxides, and the distribution uniformity of the reducers on the SCR catalyst. Relevant effects such as the formation of solid deposits will also be investigated and discussed. Furthermore, the result of the second part of the thesis will include pinpointing the challenges of the new method, which can be briefly described as spray drift effects. In the third part of the thesis, the challenges identified in the second part will be addressed and solution proposals will be developed. Based on the methodical development process, a concept of an exhaust gas system optimised to meet the previously identified challenges will be developed. For this purpose, different design possibilities of the concept exhaust gas system will be developed, analysed, and evaluated. The result of this concept study will then first be designed in CAD. This will be followed by comprehensive flow-engineering studies based on CFD. The aim of these flow mechanical investigations will be to identify and discuss the central flow mechanical effects of the exhaust gas system spray interaction. For this reason, only the heated spray in the concept exhaust gas system without a mixer will be investigated in the first step. The result will show that spray drift effects also take a central role here. Based on these findings, basic mixer concepts will be developed. The flow mechanical effects that occur will again be analysed and discussed here as well, and optimisation potential will be deduced from them. In summary, the results of the thesis are the legal, design, and flow-mechanical boundary conditions for the development of an innovative but close-to-production exhaust gas system.

Modern concretes are increasingly susceptible to a failure mechanism known as heat-induced explosive concrete spalling. This involves the sudden loss of material during severe thermal exposures such as might be experienced during a fire. This typically occurs violently, and could result in; severe loss of cross-section, direct thermal exposure of the internal steel reinforcement or prestressing, and – in some cases – structural collapse. As such, heat-induced explosive concrete spalling in fire poses a credible risk to reinforced and prestressed concrete structures and has received considerable research attention in recent decades. Certain types of structures such as tunnels have historically been more susceptible to spalling due to the concrete used, the particular mechanical conditions, and the potential fire loads and dynamics involved. However, with advancements in concrete technology being driven by sustainability and optimisation, spalling is becoming more prominent in conventional concrete structures such as buildings and bridges. Due to the complex nature of heat-induced explosive spalling there is currently no validated guidance to enable the design of concrete mixes to prevent spalling, nor any established, widely verified, repeatable test methods to confidently quantify or demonstrate spalling resistance for a particular mix in a given end-use application. As a result of this lack of validated testing and the complexity of the phenomenon, no theoretical or computational models yet exist that can predict spalling with sufficient confidence to be used in design. The aim of this thesis was to advance experimental spalling research through the development of an experimental apparatus which addresses deficiencies of others, most notably repeatability and control of thermal and mechanical boundary conditions under a range of relevant heating scenarios. Following this, the aim was to carry out carefully controlled, repeatable experiments with a precision and scale which has not been achieved before, in order to understand variability in spalling phenomena and improve knowledge of some of the main parameters that are known to influence spalling. In this thesis the key variables known to influence concrete’s spalling propensity are identified, initially based on the available research literature. Following this, an experimental method and framework to allow repeatable testing of concrete mixes, with careful control of these key variables, is developed, presented, and applied. This experimental method is based on the use of a radiant panel array impose an incident heat flux on samples. This approach to heating was developed previously at The University of Edinburgh, and has been referred to as H-TRIS within the spalling community. This name will be used throughout the thesis but it should be noted that since this work other authors have made use of the same apparatus and chosen not to use this name to describe the movable radiant panels. The experiments and development of the method are split into three stages within this thesis. Initially, four heavily instrumented furnace tests were carried out within the Prometheus testing facility at CERIB, France, on a total of thirty six concrete samples with a range of mix (i.e. polypropylene fibre content) and geometric parameters (i.e. plan dimensions and thickness). Importantly, this also allowed the thermal exposure received by the samples when tested under exposure to standard cellulosic, and French modified hydrocarbon temperature versus time curves to be monitored and characterised, as well as giving insight into the influences of different key sample parameters. Second, thirty three samples, all of which were cast in parallel with the samples used in the CERIB furnace tests, were transported to Edinburgh and tested using the H-TRIS experimental method and apparatus. This involved upgrading the existing H-TRIS apparatus with more powerful radiant panels to allow replication of the more severe thermal exposures used to assess concretes for use in tunnels. This test series allowed validation of the thermal exposures being used and a comparison of the differences between the two test methods, as well as further investigation of key parameters thought to influence spalling. For the final test series, a 3 Meganewton uniaxial loading frame was designed and constructed within the H-TRIS apparatus to allow application of simultaneous uniaxial external loading coincident with heating. Understanding the influence of mechanical loading and restraint on spalling performance is critical, since concrete is typically loaded in real end-use applications. The loading method and magnitudes were chosen so as to maintain relevance to concrete tunnelling construction within this thesis – however the versatility of the experimental method ensures the relevance of the resulting data to a range of possible structural concrete applications. Forty-five samples were tested in this test series, allowing the influence of loading and restraint to be carefully investigated, as well as permitting comparison of the effects of various other parameters believed to influence spalling. Taken together, the 114 concrete samples tested under various conditions for this thesis have provided a range of insights into the influence of different parameters on heat-induced explosive concrete spalling. These include – for the first time ever – careful quantification of the variability of spalling and specific knowledge of the parameters which may play the most important causal roles with respect to spalling in practice. Through the testing, a test apparatus able to accurately and repeatably control the necessary thermal and mechanical parameters was developed, and a guidance for carrying out spalling experiments has been developed and presented, making it available for future research studies and possibly also for compliance testing in practice. It has been shown existing experimental approaches have deficiencies and that this kind of carefully considered approach to experimental spalling research is required.

The slagging and fouling characteristics of biomass fuels can act as a barrier to their use as a fuel for thermal power generation. Biomasses with high alkali metal and alkaline earth metal contents, in particular those with high potassium contents, have high slagging and fouling propensities due to the formation of low melting temperature mineral phases. Under slow heating conditions using a muffle furnace, olive cake ashes have been produced at low temperature to retain inorganic volatile compounds while fully oxidizing carbon. These ashes have subsequently been heated with and without kaolin additives in different ratios to high temperatures, under both slow and fast heating rate conditions, in a muffle furnace and drop tube furnace respectively. Particular focus has been on the interactions of olive cake and kaolin in drop tube furnace combustion at temperatures ranging between 1000-1450°C and in 10% O2 – conditions representative of pulverized fuel combustion. Two additive ratio test series were conducted involving additive ratios ranging from 20% kaolin in olive cake ash (equivalent to 2% additive in raw fuel) to 50% kaolin in olive cake ash (equivalent to 10% additive in raw fuel). These tests were conducted at two temperatures: 1150°C and 1300°C. It was found that as the additive ratio increased, a threshold level for retention of volatile potassium was approached for each temperature. At 1150°C this value was 100% while at 1300°C this threshold level was approximately 80%. Furthermore, log curves were produced from the results obtained. These approximations serve to offer an insight into the levels of retention that might be achieved as a function of additive ratio. Notably, it would appear that high levels of retention are attainable with small additive ratios at the optimum temperature of 1150°C. From these additive ratio experiments it can clearly be seen that the combustion temperature has a significant effect on the efficacy of the kaolin additive. To further investigate this, an experimental test series was conducted involving DTF testing with 50% kaolin in olive cake ash at 1000°C and 1450°C. It was found that the level of retention at 1000°C was similar to that found at 1300°C (approximately 70%) while at 1450°C, 40% retention was measured. It is expected that at 1000°C the reaction is not under thermodynamic control and so the reduced retention is due to the slower kinetics at that temperature. This is not the case at the two higher temperatures of 1300°C and 1450°C. At these very high temperatures it is possible that there may be some degradation of the kaolinite additive which reduces its ability to react with the potassium. Following the experiments with olive cake and kaolin, some further tests were conducted with miscanthus and wood as alternative feedstocks with different levels of potassium. While these tests were limited in number, they did show significant signs of substantial retention of volatile potassium. With wood in particular being a favoured feedstock in large scale biomass combustion (in part due it its low ash content) further research in this area is expected. Additionally, the use of an alternative aluminosilicate additive was explored. The additive chosen was coal fly ash due to its high availability and low cost. When compared with the results achieved with kaolin, the coal fly ash that was used performed poorly. The notable contrast between the fly ash and the kaolin additive was a much lower alumina to silica ratio. When considering the ternery mineral phase diagram for the system K-Al-Si and the area of high melting temperature phases that exist where higher ratios of alumina are present, it is expected that the alumina to silica ratio of the additive is key to its performance. To further investigate this, further coal fly ash additives comprising of higher alumina to silica ratios should be tested. The use of Mineral Liberation Analysis in this research afforded the opportunity to examine the form of potassium species (by association) present in olive cake ash samples. By using this method, it was observed that the volatile potassium present in the starting fuel existed primarily as KOH. By comparing this starting material with the ash following combustion with and without kaolin at 1150°C and 1300°C, it was possible to see the transformations that occur to the potassium species. In the absence of the additive it was found that while all KOH was volatilised and lost, some of this volatile potassium migrated to form potassium silicates. In the presence of the additive however, this migration did not occur. In preference, a large proportion (up to 100%) of the KOH reacted with the aluminosilicate additive to form potassium aluminium silicate mineral phases. Thermodynamic data available in literature demonstrates that this is due to the favourable ΔG energies of formation for this reaction. By further analysis of the molar ratios of elements present in the mineral phases detected, it was possible to speculate as to the identity of potential specific compounds in the ash samples. These include the most commonly reported products of the reaction of K with Al-Si: kalsilite and leucite. By using this method it was found that the reaction product kalsilite was most likely to exist in large quantities in the samples.

Over the last few decades, researchers have shown conclusively that is it possible to incorporate self-healing systems into concrete structures. Some of these are enhanced natural autogenic mechanisms, while others are based on autonomic (or engineered healing) techniques. One promising approach involves embedding channel networks in cementitious matrices as a delivery system for healing agents. These vascular healing systems have the advantage that they can be pressurised and provide a continuous supply of healing agent, which enables multiple cycles of damage to be healed. Although much experimental work had been undertaken on vascular systems for cementitious structural elements, the author found that there was not a complete characterisation study on any one system that was adequate for developing a comprehensive design or numerical model of the system. This provided the motivation for the work reported in the thesis, which involved an extensive experimental programme of work aimed at characterising the transport and mechanical behaviour of a cementitious vascular material system with cyanoacrylate as a healing agent. The tests series undertaken included (i) three-point flexural bending tests on unreinforced notched prisms, in which the effects of varying the healing period, healing agent pressure and loading rate were explored; (ii) flexural tests on notched beams with an offset arrangement of discontinuous reinforcement that were undertaken to study healing behaviour when complex crack patterns occur; (iii) direct tension tests on notched cubes with different crack openings for a range of healing periods; (iv) dynamic healing-agent flow tests that investigated the variation of the capillary meniscus contact angle with velocity; (v) the sorption of healing agent into a concrete specimen through a natural crack surface; and (vi) tests in which healing-agent curing adjacent to a cementitious substrate was studied. A particular focus of the present work is simultaneous damage-healing behaviour and the various properties that influence the associated response. This requirement governed the range of loading rates (crack opening rates), healing agent pressures and fixed healing periods considered in the test series. The test series successfully characterised the mechanical behaviour of the healing system for situations in which damage and healing are separated in time as well as for cases in which these processes overlap. In addition, the experimental programme provided data on the curing response of the healing agent and on its dynamic flow characteristics in flow channels, discrete cracks and within the cementitious continuum. This work guided the development of a series of constitutive models for both mechanical and transport behaviour. These formed the basis of a numerical model, which was developed by others, but used in a material tailoring exercise in the current study.

In addition to the immediate life safety concerns during building fires, uncontrolled fires within buildings have the potential to cause extensive structural damage. Current design guidance for structures in fire focuses exclusively on the life safety of the occupants within buildings. With regard to the structure this is generally achieved by specifying a defined fire resistance period during which structural integrity must be maintained and fire spread must be prevented. This is to ensure that the building's egress routes are not compromised until all occupants have escaped from the building and fire-fighting operations have been completed. Designers are not typically required to explicitly consider the residual post-fire effects on structures. Particularly in relation to concrete structures which tend to perform well in fire and can often be reinstated, this raises questions about whether the post-fire effects are important from a life safety perspective. This thesis explores the applicability of some of some simple models to reflect the complex behaviour observed when symmetrically reinforced concrete columns are subjected to non-uniform heating regimes. An experimental test series was designed to provide an extensive data bank of the performance of a single reinforced concrete column subjected to many combinations of different loading and heating conditions. To this end 46 geometrically identical reinforced concrete columns were subjected to a combination of loading and heating conditions and both the thermal and mechanical response were monitored during both the heating and cooling phases of the experiments. All surviving columns were destructively tested to determine their residual performance 24 hours after cooling back to ambient temperature conditions. A sectional analysis model is presented to determine the load-moment interaction of a reinforced concrete column after exposure to elevated temperatures. This has been aided with the use of non-destructive testing of each of the columns with the aim of helping practitioners determine the post-fire properties and to aid in the residual analysis of a concrete structure exposed to elevated temperatures. In comparing the results to the current design guidance available it would be expected that each experiment would react in an identical fashion as the design of each of the columns and the external heat source is identical in each case. This experimental test series has concluded that this is not necessary the case. From a post-fire residual structural performance standpoint, this raises a number of questions regarding how practitioners can approach the assessment and analysis of reinforced concrete structures in the future. Given the findings of this work, and the one of a kind data bank that has been created as regards to the performance of reinforced concrete columns subjected to non-uniform heating and cooling regimes, fire engineering modellers now have the capability to validate Finite Element models against a series of 46 reinforced concrete columns through the full range of heating, cooling and post-cooling structural performance. The results of which have profound implications for the current design methodologies recommended. This data bank can now be used to validate such models and inform future design methodologies.

This thesis describes the design and construction of an experimental apparatus to enable the repeatable testing of appliqué protective systems against buried charges. This thesis highlights the difficulties in understanding and predicting buried blast loading, as well as why it is important to know the distribution of impulse as well as how quickly it is delivered. A review of the literature investigating the phenomenology of buried charge testing is presented, along with previous work which has looked into the factors which can affect the output of a buried charge. Tests were conducted using the developed apparatus, with the detailed output of 21 tests against varying thicknesses of Armox 440T steel being presented within this thesis. The testing was conducted at 1/2 scale, with charge sizes between 400 and 1000 grams, and nominal plate thicknesses between 6 and 12 mm. For each test the full deformation profile was provided along with dynamic (peak) and residual deflections to enable numerical model validation. The preparation of the soil bed for the testing has been carefully controlled based on previous experience at the University of Sheffield. The test series used Leighton Buzzard 14/25 sand which is a silica based uniform soil with particle sizes between 0.6-1.18 mm. This was prepared to a moisture content of 5% and dry density of 1620 kg/m3. Analysis of the test series was done using the Nurick and Martin (1989) analysis method with modified correction factor based on the distribution of kinetic energy. This analysis has shown that for the appliqué systems tested, the normalised deflection can be predicted if the normalised total impulse as well as the distribution of impulse imparted to the system is known; this finding should be the basis of a fast running engineering model for plate deformation from shallow buried blast and other non-uniform impulsive loading.

This research concerns the influence of a range of construction methods, acting at or below excavation formation level, on ground movements of the retained surface attributed to a 12m deep excavation in very soft to soft soil. Movements around excavations arise as a consequence of the removal of soil and lateral wall deformations. The work examined the behaviour of excavations that were supported by a high stiffness embedded retaining wall whilst modelling a variety of construction techniques. Four distinct construction methods were modelled which could be regarded as surcharging the formation level or stiffening the ground below excavation formation level. The specific techniques that were explored include underwater excavations, bermed excavations, deep soil mixing and double walled excavations. This study aimed to determine the efficiency of these construction measures on reducing the magnitude and extent of displacements occurring behind the retaining wall. Experimental data were obtained from twenty-two plane strain centrifuge model tests undertaken at 160g. The geometry of the model comprised a pre-formed excavation where the retaining wall was laterally supported by a continuous prop acting over the majority of the height of the wall and the excavation formation level was surcharged by a pressurised rubber bag. Pressure in the bag at formation level was reduced at a constant rate to simulate the stress change caused by the excavation process. Vertical movements at the retained ground surface were measured using displacement transducers whilst subsurface deformations elsewhere in the model were determined from the analysis of digital images captured by cameras viewing the front of the model through a Perspex window. The magnitude and extent of movements were quantified and the general patterns of ground deformation were identified for the construction methods implemented. A series of reference tests were conducted to provide a baseline against which modified excavation tests were compared. The stiff wall and continuous prop supporting the retaining wall ensured that the reference tests quantified the magnitude of displacements at the retained surface arising simply as a result of heave at the formation level. The main test series investigated a range of construction methods that aimed to surcharge or stiffen the formation level. Additional tests were also undertaken to evaluate the influence of wall embedment on the performance of the excavation system. Direct comparisons were also drawn between tests in an attempt to establish the significance of wall crest fixity on soil movements. The use of all of the special construction techniques investigated were shown to reduce the magnitude of vertical displacement behind the retaining wall and at the formation level; in addition to reducing horizontal displacements at the toe of the wall. Increasing the retaining wall embedment depth in the main test series generally reduced the magnitude of vertical settlement by a factor of two, however the effect was less pronounced in the reference tests. Improving the fixity of the crest of the wall delayed excavation collapse and, where additional support mechanisms were not employed, pinning the crest of the wall was shown to reduce maximum settlement in the reference test by a factor of three. Of the four supporting construction methods the underwater excavation was found to be the most effective owing to the reduced change in vertical stress during the simulated excavation. Various deep soil mixing geometries were modelled and similar excavation behaviour was observed, however deep soil mixing ground treatment extending to the toe of the retaining wall and across 2/3 of the excavation demonstrated a slight reduction in settlement. Similar behaviour was observed for double walled excavations. Combining underwater excavations with a double wall was shown to further reduce maximum settlements however little additional benefit was observed when performing an underwater excavation with a deep soil mixed soil layer at excavation formation level.

Laser scabbling of concrete is the process by which the surface layer of concrete may be removed through the use of a high power (low power density) laser beam. The aim of this study was to investigate the mechanism(s) responsible for laser scabbling. This was achieved in three stages. The first stage was a test series used to establish an experimental procedure for assessing the effects of various parameters that may be critical for the effectiveness of the process, such as material composition and initial moisture content. The second stage was a test series investigating the effect of concrete composition on laser scabbling. The first two test series identified that the driving force of laser scabbling in concretes originates from the mortar, therefore, the third test series concentrated on the factors that influence laser scabbling of mortars. Throughout the study, infra red recordings have been used to quantify laser scabbling behaviour, along with the volume removal due to laser scabbling and characterisation techniques such as XRF, DTA and TGA. The results suggest that scabbling is mainly driven by pore pressures, but strongly affected by other factors. The removal of free water from mortars prohibits scabbling, but resaturation allows mortar to scabble. A reduced permeability, either due to a reduction in the water/binder ratio or the use of 25% PFA replacement, enhances laser scabbling. Results show that the biggest effect of ageing is due to specimens drying. Mortars and cement pastes were seen to scabble at a constant rate, whereas concretes experienced a peak rate, after which volume removal reduced dramatically. Basalt aggregate concrete was less susceptible to laser scabbling than limestone aggregate concrete due to vitrification. A higher fine aggregate content increases volume removal and fragment sizes during laser scabbling.

This investigation is concerned with the large-strain characterisation of Magneto-Rheological Elastomers (MREs), with the main focus on experimental characterisation. Quasi-static uniaxial compression, uniaxial tension, pure shear and equi-biaxial tension experiments have been performed both in the absence and in the presence of magnetic fields. The experimental data generated during this investigation constitutes an extensive data set characterising MREs under various deformation modes. This is the first time that such a consistent data set has been produced, and such data are essential to develop accurate constitutive models characterising MREs under general deformations. Isotropic and anisotropic MREs composed of silicone rubber and up to 40 vol% carbonyl iron powder were manufactured using a reliable and repeatable process. Specimens of different shapes were made in specially designed moulds and anisotropic samples were produced by placing the moulds inside a strong magnetic field during the curing process. Understanding the magnetic permeability of MREs is a prerequisite for both the development of constitutive models and for quantifying the magnetic flux applied to specimens during testing. Accordingly, the magnetic permeability of MREs has been characterised using a novel, simple and low-cost method. Large-strain experiments were conducted using test rigs specially designed for use in universal test machines, while incorporating permanent magnets. The magnetic flux was applied in the loading direction and samples were aligned with their direction of particle alignment both parallel and perpendicular to the loading direction. Where possible, strains were measured using a digital image correlation system. MREs were found to be very sensitive to the stress-softening Mullins effect as such a novel testing strategy was used: MRE samples were repeatedly used in several cyclic tests in a test series and tests conducted in the absence of magnetic fields were repeated twice in the test series in order to verify the stress-strain results and importantly, to eliminate the influence of the Mullins effect when interpreting the final stress-strain results. Cyclic fatigue tensile tests were conducted to determine stability strain limits of MREs, and specimens were not tested beyond these limits in the experiments. The mechanical response of MREs was found to be strongly nonlinear when tested up to large strains. Anisotropic MREs with particle alignment in the loading direction are the stiffest specimens, followed by anisotropic MREs with their particle alignment perpendicular to the loading direction, while isotropic MREs are the softest type of MRE. Moduli were found to increase with increasing iron content and MREs preconditioned to larger levels of strain were measured to be softer than the same type of MRE tested to lower strain levels. The largest MR effects were found in the small-strain region for all MREs. Anisotropic MREs containing 30% volume iron fraction with particle chains aligned parallel to both the loading direction, and the direction of the magnetic field, were found to exhibit the greatest MR effect of all specimens tested. MR effects generally decrease rapidly in the mid-strain region, but increase again at larger strain (> 15%). MR effects can be enhanced by preconditioning the specimens to larger levels of strain. The largest relative MR effects were found in uniaxial and equi-biaxial tension tests. Data fitting to pre-established hyperelastic constitutive models were conducted to evaluate their ability to characterise MREs. The parameters of the Ogden model describing isotropic MREs under general deformations in the absence of a magnetic field were successfully de- termined when experimental data obtained from tests up to the same strain level were combined in multi-deformation mode data fitting. The Ogden-Roxburgh model was found to describe the stress-softening well. Data fitting of several transversely isotropic constitutive models to experimental data of anisotropic MREs was not successful and none of the models employed in this investigation could accurately represent the data.

This document reports the efforts conducted to determine critical parameters and configurations for Manual for Assessing Safety Hardware 2016 (MASH) Test Level 3 (TL-3) compliant breakaway luminaire poles supported by slip bases, including identifying pole configurations with the potential to meet MASH TL-3 as well as recommending critical configurations for full-scale crash testing. A thorough literature review was conducted which included survey results collected from Midwest Pooled Fund state departments of transportation (DOTs), standard plans from state DOT’s, and past luminaire pole testing. Numerical LS-DYNA models were developed for luminaire poles with 4-bolt slip base utilized by the Utah Department of Transportation (UDOT). The LS-DYNA simulations were validated using the USBLM full-scale crash test series. The validated slip base model was utilized to simulate various pole configurations with 4-bolt slip base under MASH test nos. 3-60, 3 61, and 3-62 at impact angles of 0 and 25 degrees, with vehicle impacting at the center and quarter points. The pole configurations included pole heights ranging from 20 to 50 ft and mast arm length ranging from 4 to 20 ft. The simulations were post-processed and analyzed to identify trends regarding the MASH safety criteria, including occupant compartment deformation, occupant risk measures, and vehicle instability, to identify the critical parameters and configurations for slip base luminaire poles. The following trends were identified from simulation results: (1) none of the simulations exceeded MASH limits for OIV, ORA, roll and pitch values; (2) MASH 3-60 impacts appeared to be more critical in terms of roof crush; (3) Vehicle center impacts were found more critical than quarter point impacts for roof crush; (4) roof crush beyond the 4-in. MASH limit occurred for multiple configurations at each pole height in MASH 3-60 impacts, (5) none of the MASH 3-61 and 3-62 impacts led to intrusion into the occupant compartment; (6) pole configurations with 4-ft long mast arms showed the best potential to pass MASH; and (7) nearly all pole configurations between 450 and 600 lb showed potential to pass MASH. Based on simulations results, critical pole configurations and impact conditions were recommended for full-scale crash testing. Advisor: Mojdeh Asadollahipajouh

A well-established ground improvement approach, the polymer injection technique has the advantages of being durable, hydro-insensitive, fast curing, and easy to deploy in dense urban environments. It is being widely employed with much success, primarily for uplifting embankments, releveling slabs and foundations, and erosion control. In view of the aforementioned advantages, its potential as a soil liquefaction countermeasure is of current interest. In this regard, the main objective of this dissertation is to explore viability of the polymer injection technique as a soil liquefaction countermeasure. This objective is achieved in three phases. First, a large-scale shake table test series is conducted to assess potential of the polymer injection technique as a countermeasure against seismically induced soil liquefaction. Specifically, mitigation of settlement for a shallow foundation supported on a liquefiable sand deposit is explored. In a series of two shake table experiments, system response is studied first without (baseline) and subsequently with the injection of polymer into the liquefiable stratum. Upon application of the polymer injection countermeasure, results show a significant reduction in the tendency for liquefaction and resulting foundation settlement. After the test, careful excavation of the deposit provided additional insights into the injected polymer configuration, creating solidified zones that further support the shallow foundation load and increasing the overall stratum strength (relative density and confinement).In the second phase, insights gained from the test series are leveraged to calibrate a nonlinear solid-fluid coupled finite element model. In this regard, stress-strain properties of the solidified polymer zones and surrounding strengthened ground are developed. This calibrated model was then extended to explore additional scenarios beyond the scope of the original test series. Effects of geometric configuration of the solidified polymer zones, and state of compacted soil around the solidified zones were explored in detail. Finally, within a computational framework, a representative practical application of the polymer injection technique as a liquefaction countermeasure is addressed. For that purpose, numerical modeling scenarios of polymer injection are studied to mitigate the damage reported in a well-documented bridge seismic response case history, where large lateral spreading ground deformations ultimately resulted in unseating of a railroad bridge-deck span. Detailed post-earthquake reconnaissance surveys and observations are used to computationally simulate the bridge-ground system, and capture the documented damage mechanisms. Three different polymer injection configurations are studied, and the response of the remediated bridge-ground system is explored. In these configurations, injections of the order of 10 % (volume of liquid polymer to soil) resulted in a major reduction of lateral spreading deformations, precluding the observed bridge-deck unseating damage mechanism. Overall, the insights gained from this research indicate that the polymer injection technique has considerable potential for mitigating soil liquefaction.

Climate change has the potential to affect any transportation network that comprises embankments and cuttings built with soil material in an unsaturated state that is exposed to the climate. The BIONICS project (BIOlogical and eNgineering Impacts of Climate change on Slopes) aims to investigate how climate change will affect the serviceability and safety of earth structures. Part of the BIONICS project was to build a full-scale highly instrumented embankment combined with an automated climate control system. Studies on the fill material used in the construction of the BIONICS embankment were carried out to understand the hydro-mechanical behaviour of the material, which is a sandy clay of medium plasticity. This involved the determination of the soil water retention behaviour and the mechanical behaviour under unsaturated conditions. Soil water retention curves (SWRC) were determined by a series of tests performed on compacted samples comprising various techniques (filter paper, psychrometer, high capacity suction probe and pressure plate). Total and matric suction SWRC following primary drying paths from 25% of water content were determined. In addition, a series of tests with the filter paper on samples at lower water contents (15%, 20% and 22%) was also performed. The SWRC following drying paths showed behavior similar to scanning curves intercepting the primary curve around 3000 kPa (11% water content). However, SWRCs that followed wetting paths showed atypical behaviour by intercepting the primary drying curve. For the investigation of the mechanical behaviour a series of constant water content triaxial tests were carried out in double cell triaxial cells on as-compacted samples, and also samples wetted and dried from as-compacted conditions of 15%, 20% and 22%. A test series of samples tested in a saturated state was also performed to provide a reference state for the unsaturated tests. The unsaturated test series showed that the slope of the critical state line (CSL) in deviatoric stress space (M) was found to be similar for all water contents. The slope of the CSL in ν-ln(p-uw) space (λ) was found to be similar for all water contents, however the CSL shifted position due to variation in the intercept, Γ. Since specimens were at high degrees of saturation, calculations based on effective stress showed a reasonable interpretation of the data. However, a better agreement was achieved using the Bishop’s average stress assumption. A new field measurement system to continuously measure pore water pressure at different depths using high capacity suction probes has been developed. This system was installed at the BIONICS embankment in two different panels (well and poorly compacted). In the well compacted panel pore water pressure behaviour had the tendency to increase with depth, always recording values that were slightly negative at shallower depths and positive at greater depths, showing profiles roughly parallel to the hydrostatic line suggesting that the material was close to saturation. In the poorly compacted panel the behaviour was found to be more variable showing abrupt reactions from the probes to weather events. The differences in behaviour between the well compacted and poorly compacted panels could be related to the laboratory investigations. The well compacted panel was more homogeneous and less permeable (10-11 m/s). The poorly compacted panel was more heterogenic, more permeable and hence, during monitoring, showed more dramatic changes in pore pressure compared to the well compacted panel.

The construction industry has been challenged by the UK Construction Foresight Panel to apply advanced information and communication technology to improve the performance, in terms of sustainability, of the existing built environment and infrastructure. Traditionally, built-environment maintenance is a capital-cost-driven activity that relies either upon the subjective assessment of a built environment and infrastructure condition (i.e. a stock condition survey) to identify maintenance needs, or upon a reactive response to a component failure. The effectiveness and efficiency of the stock condition survey process to support planned maintenance has previously been questioned and a more sustainable approach, based on an objective assessment of a built environment and infrastructure performance, has been suggested. Previous attempts to develop objective-based (though not performance–based) maintenance models have largely failed, due to the limitations of technology, the daunting task of managing large amounts of data, and the inability of mathematically based models to cope with the complexity of real-life situations. This thesis addresses this challenge by exploring the feasibility of a performance-based assessment methodology to determine the maintenance needs of a buried oil steel-pipeline system and the impact that any changes in condition may have on the performance and integrity of related components in the pipeline system. The thesis also contains an evaluation of the ability and effectiveness of piezoelectric elements in pipeline defect (crack) signature detection to predict changes in component performance with data sets derived experimentally using laboratory bench testing. Vibration sound-emission detection techniques performed on various oil steel-pipeline defects, using non-destructive testing methods, were validated using attenuation and waveform analysis. Defect size and progression (i.e. the pattern characteristics of the defect) were monitored, measured and identified through spectrum analysis of multiple emission signals in combination with a number of frequency bands. Two series of tests were undertaken to evaluate the ability of vibration sound emission characteristics to identify steel pipeline defects, including leakage. Test Series 1 established the frequency (waveforms) of the generation of the acoustic emission signal caused by normal fluid dynamics (water flow) through the experimental steel pipe and the resulting signal propagation characteristics. Test Series 2 detected and monitored changes in the signal characteristics for incipient defects: (a) small-nail damage, (b) medium-sized nail damage, (c) large-nail damage and (d) crack to leakage source [sealed holes as a simulated corrosion to total failure]; oil was the fluid medium. The defect sources and leakage signals were also studied, and compared with theoretical models. The results of the theoretical analysis and the laboratory experiments confirmed the ability of non-destructive testing, based on vibration sound emission techniques, to detect and distinguish between different failure modes. The ability to carry out a basic inspection, analysis and report of a pipeline using an integrated-sensor device offers many potential benefits. The use of an integrated-sensor device is expected to provide valuable pipeline management information. Specifically the ability to detect and locate mechanical damage at the incipient stage and provide an assessment of the overall pipeline operating condition, including changes in performance profile and prediction of an estimated time to failure, has been shown to be feasible as part of a pipeline maintenance and rehabilitation programme.

The increasing requirements in the automotive industry regarding safety, weight and economic efficiency involve the application of stiff structures made from hollow sections, manufactured by bending tubes and profiles into complex shapes. These geometries comprise different radii in several planes, including compound bends, and demand new techniques for manufacture. To this end, the free-bending technique has evolved which has the potential to realise almost arbitrary bending geometries combined with fast bending speed. This research provides a general insight' into free-bending and investigates the possibilities of this novel bending technique in respect to applications in the automotive industry. The principles of the free-bending technique are explained and a comparison is drawn with other bending techniques. The Nissin CNC Bender was used to carry out the bending tests in order to investigate the free-bending technique with regard to its geometrical capabilities, bending speed, surface quality and the resulting ovality of the tube after bending. For this a try-out geometry similar to an engine cradle was bent using steel, stainless steel and aluminium tubes and the repeat accuracy was examined. For feasibility studies, a FEA model was developed and validated with the results from the tubes bent from a second bending test series where the geometrical results including wall thickness and ovality were investigated. From this FEA model the elastic and plastic forming ofthe tube during the process was examined. In order to determine the necessary bending control data for arbitrary bending geometries, an analytical model based on the geometrical data (bending line and tool set-up) was derived. Finally a third test series with rectangular aluminium profiles was carried out and the profiles' geometries, the wall thicknesses and the strains were evaluated and compared with the FEA results. The free-bending technique has proven its potential to realise almost any arbitrary bending geometry with a bending ratio of the centre line radius with respect to the initial tube diameter of2.1 using a ball mandrel. Free-bending has the added advantage in achieving compound bends without the recourse to special tools or tool changes for different bending radii. Furthermore, the improvement of up to 100 %in bending speed compared to rotary draw bending can be achieved dependent on the composition of bends in the geometry. However, due to its sensitivity to changes in material behaviour, lubrication or geometrical tolerances, it is necessary to have stringent control for parts with small bending tolerances. This research has contributed to new knowledge with regard to the possibilities and limitations of the free-bending technique and serves as a decision aid for the application ofthis novel technique in series automotive production. Furthermore, the FEA model in conjunction with the analytical model to determine the process control data enables the evaluation and the realisation offeasibility for any required bending geometry before the production ofexpensive bending tools.

Presented in this thesis is a combined physical testing and computational modelling programme of research for the structural integrity of bolted joints for Pultruded Fibre Reinforced Polymer (PFRP) profiles. The work was carried out in a joint EPSRC funded Structural Integrity (SI) project between the Universities of Warwick and Lancaster. It will be shown in the thesis that it provides a significant new body of scientific understanding and relevant independent joint test data, which can be used in the future preparation of design guidance for the safe and rational design of joints. The contribution from the author to this SI project on plate-to-plate steel bolted joints can subdivided into four parts. The first part includes the evaluation of the 10 single-bolted and the 5 multi-bolted double lap-joint test series that appeared before 2001. This identifies that the 15 test series, from 10 centres, are often different because the researchers chose different parameters to study. Of the 800 concentric strength tests 640 were single-bolted and 160 were multi-bolted. It is noteworthy that few of these previous tests include environmental conditioning of the joints. A review of design methods is given in this part of the thesis. This shows that significant joint test data is required to appraise SI design methods for PFRP bolted joints, such as presented in the EUROCOMP Design Code and Handbook of 1996 and in 1981 by Hart-Smith. The EUROCOMP simplified and rigorous methods are expected to be generic and involve damage tolerance to increase the strength of the joint design. It is further found that application of these methods requires Finite Element (FE) stress calculations for the target analysis due to bolt bearing, and for the source analysis, for multi-bolted joints, to determine the bolt load distribution and by-pass loads. Parts two and three of the contribution from the author are combinations of experimental and FE analysis work that focuses on the target and the source problems, respectively. The strain field close to a notch is measured in part two using a pin-bearing test method and strain gauged specimens. To find out if FEA can predict the target strains/stresses an ABAQUS© FE model is developed. The PFRP material is assumed to be homogeneous and possess orthotropic properties. It is shown that a linear elastic analysis, with contact and friction modelled, gives strains that are similar to those measured. This observation is supported by a small photo-elastic strain analysis using the GFP 1000 system from Stress Photonics. By way of the evaluation of previous testing in part one it was decided in part three to conduct a comprehensive series of multi-bolted joint tests. Constant variables in this series of concentric loaded tests are the PFRP material, the plate thickness, the material orientation, the bolt diameter, the clearance hole size, and the bolt torque. This test series, design using a method by Taguchi, comprised four different joint configurations, twelve different joint geometries and four different environmental conditionings (including a temperature of 60oC and ‘wet’ ageing for 1000hrs). The author presents the testing procedure and 432 resistance results for 144 different joints, having a batch size of three. Mechanisms and modes of failure are identified, and several unrelated to the distinct modes of bearing, shear-out and net-tension used in current design approaches are presented. Using this fairly large number of consistent data points an evaluation is made on the influence of the various variables. It is shown that is not straightforward to establish simple strength trends. Furthermore, the findings of this test series suggest that a batch size of three is too small, as batch strength variability is relatively high. By way of a Round-Robin exercise between the two Universities, with joints having a batch size of 10, it is shown that the high strength variability can be associated with the non-homogeneity of the reinforcement arrangement in the PFRP material. Two multi-bolted joints having three rows of three bolts are instrumented with strain gauges to determine the strain distributions linked to bolt load distribution and by-pass loads. Measured strains are compared to numerical predictions from an ABAQUS FE analysis using the same modelling methodology as for the pin-bearing target analysis. The source analysis comparison is acceptable, but like many of the results presented in the thesis it appears likely that the experimental measurements are affected by the non-homogeneity in the macrostructure of the PFRP. Presented in part four is a preliminary appraisal of the EUROCOMP simplified design method and the Hart-Smith design method. The EUROCOMP method is shown to possess deficiencies, via a critique by Lancaster University, which indicates that it cannot be used in practice. By taking information from the multi-bolted joint test series in part three the author constructs semi-universal design charts using the Hart-Smith method, which can be used to design joints with changing geometry. An important finding from this preliminary appraisal is that the SI design methods are difficult to apply since they require lots of physical test data and relevant and reliable stress results from FEA. Finally, despite the programme of research providing a significant new body of scientific understanding and relevant independent joint test data it is concluded that further work is needed before an SI method for the universal design of plate-to-plate PFRP bolted joints can be considered for a code of practice.

Dry-lubricated contact systems are widely used in varied engineering applications, among which the spherical plain bearing (with dry-lubricating liner) in aerospace applications is one with increasing demands in performance. To achieve the improvements, the surface texturing is a propitious technique since it has seen a rapid development in the last few decades as it achieved promising effects in friction, wear and adhesion with different forms. However, to tailor the surface textures to the needs in tribological performance, it is essential to fill the gap of knowledge in the aspects such as the interaction between the liner surface and the textured counterface and the influence of the kinematics of the transmission system. Meanwhile, the relationship between the bonding strength of the liner and texturing morphology and adhesion force needs to be investigated. The research in this thesis firstly aims at explaining the effects of surface texturing on the tribological performance of the dry contact pair (Polytetrafluoroethylene, or PTFE composite against steel surfaces), conducting systematic test series investigating the friction and wear performance with different texturing parameters (e.g. depth, coverages). To obtain understanding of the tribological phenomenon occurring with the dry contact, a novel transfer film characterisation technique based on multi-accelerating-voltage Scanning electron microscope (SEM) and Secondary ion mass spectrometry (SIMS) is developed. With this method, previous obscurity in the transfer film characterisation, particularly with worn counterface is eradicated. Combined with contact mechanics analysis using Finite Element (FE) methods, the mechanism of micro-abrasion and transfer film formation/re-distribution are identified. Moreover, in this work a new aspect of the effects of the surface texturing on tribological performance is explored, considering the kinematics of the transmission system. With the proposed novel output-oriented modelling method of the kinematics of the transmission, a series of anisotropy tests of the tribological performance is instructed, leading to the finding that surface texturing may alter the anisotropy of the dry contact. Fundamentally, the introduced surface textures convert the contact between an anisotropic surface (composite) and a homogenous counterface into a contact between two heterogeneous surfaces. Finally, this work investigates the effects surface texturing/roughing in bonding strength and improvement. The basic mechanism and phenomenon related with bonding strength are discussed. After identifying the inefficiency in describing the wettability of textured surfaces with conventional contact angle models, the surface free energy analysis is modified with a droplet morphology analysis. The theoretical support for anisotropic wettability of surfaces with directional surface textures is formulated. To conclude, focusing on the physical phenomenon and working mechanism of surface textures in dry-lubricated contact system, this thesis illustrates the influence of surface texturing on tribological performance and bonding strength of bearing liner in aerospace applications. With the innovative transfer-film characterisation technique, systematic contact mechanics analysis, the output-oriented kinematic modelling and the modified surface free energy analysis for wettability, knowledge is added to the corresponding aspects that have opacity in previous research.

This study examined the effects of student choice-of-text and reading comprehension outcomes in a 12-week independent reading program in an upper-secondary school. Students aged 17-18 (N = 52) were divided into two groups with one receiving an assigned text of age-appropriate Lexile estimate and genre; the other group was given free choice-of-text from an appropriate Lexile level from a classroom library. This quasi-experimental study followed a pretest-posttest, one-way ANCOVA model with both groups receiving the Gates-MacGinitie Reading Test series before and after the intervention. Both groups made modest gains; however, the ANCOVA results revealed no statistically significant difference between the choice-of-text and No Choice-of-text groups (p =.262). Participant interviews of typical and non-typical cases are included. Recommendations for further research include a call for a readjustment of previously reported effect sizes upon which to build future studies in adolescent literacy. Keywords: Adolescent Motivation to Read Profile (AMRP), Gates-MacGinitie Reading Test (GMRT), Sustained Silent Reading/Daily Independent Reading (SSR/DIR), Analysis of Covariance (ANCOVA), Reading Comprehension, Instructional Design Theory, Choice-of-Text, Secondary Education

Earthquake induced liquefaction can cause significant damage in the built environment. Structures on shallow foundations can suffer large settlement and rotation, and light under- ground structures can uplift. The performance of structures with basements, which intuitively combines these two problems, is not understood. In this thesis, the seismic behaviour of structures with basements in liquefiable soil has been investigated. A series of highly instrumented dynamic centrifuge tests showed that the presence of a basement can reduce the liquefaction induced settlement of a structure whilst maintaining the natural isolation provided by liquefied soil. The generation of positive excess pore pressures during shaking increased the buoyancy force provided by the basement. When the ratio of uplift to total weight during liquefaction was controlled, this buoyancy reduced settlement compared to structures with shallow foundations without basements. The centrifuge test data showed that structures with basements were susceptible to suffer a large accumulation of rotation during earthquake induced liquefaction. Compared to structures without basements, resistance to rotation provided by the soil decreased because the buoyancy provided by the basement reduced the vertical effective stresses below the structure. Rotation was exacerbated by an increase in the moment loading imposed by the structure due to the presence of the basement. An increase in the plan area of the basement was found to reduce residual rotation. A mechanical model for displacement and rotation in liquefiable soil was developed using data from the centrifuge test series. It was based on a traditional mass-spring-damper model, with the addition of slider elements to incorporate accumulation of displacement and rotation. The model was able to replicate the centrifuge test results when liquefaction occurred. Parametric studies using the model found that residual rotation was highly sensitive to the basement width and height of the centre of gravity of the structure. In summary, liquefaction induced settlement and rotation, and seismic demand of a structure can be minimised by including a basement and controlling the basement geometry, mass distribution, and total weight of the structure. The increase in usable space that a basement provides in a building is anticipated to make this mitigation method an attractive option compared to conventional alternatives such as soil improvement.

This thesis deals with the behaviour of concrete materials and reinforced concrete members incorporating recycled rubber particles, as a partial replacement for mineral aggregates. The research involves several experimental investigations on materials and members, coupled with detailed numerical simulations and parametric assessments. Tests on cylindrical material specimens focus on examining the uniaxial behaviour of rubberised concrete. The experimental investigation, combined with the detailed assessment of data from previous tests, show that the rubber particles influence the mechanical properties as a function of the quantity and type of replaced aggregates. A series of expressions and analytical models defining the mechanical properties of rubberised concrete are proposed. Further tests on confined rubberised concrete cylinders show that external confinement provides significant enhancement to the strength and deformation capacity of the material. The experimental behaviour of rubberised concrete members under shear loading is also investigated in this research. The design of an asymmetric four-point shear test set-up is discussed and a detailed account of test results on eighteen prismatic rubberised concrete members, with or without confinement, is presented. Close observation of specimens exhibiting shear-governed failure shows that rubber particles have a significant influence on the member shear resistance and force transfer mechanisms along the cracked interface. In addition to the material and shear tests, the experimental performance of large-scale beam-column members is examined in the thesis. Tests on fourteen large scale reinforced rubberised concrete members, subjected to lateral cyclic displacements and co-existing axial loading, are reported. The test results enable a direct assessment of key response characteristics of beam-column specimens. It is shown that members with rubber particles can offer a better balance between capacity and ductility compared to conventional reinforced concrete members. In addition, external confinement, such as using fibre reinforced polymer (FRP) sheets, can be adopted to recover the loss of strength and provide highly stable hysteretic response. Numerical simulations of all the test series are performed using nonlinear finite element analysis and validated against the corresponding experimental results. The numerical models are then used to conduct parametric studies in order to examine the effect of key material and geometric factors on the behaviour of rubberised concrete members. Based on the findings from the experimental and numerical investigations, a series of expressions to assess the key performance characteristics of rubberised concrete members are proposed in a form that is suitable for practical design application.

For more than 20 years, energy production has been experiencing a disruptive change to more efficient operation and fewer emissions. In 2018, heat production accounted for 50% of global final energy consumption and caused 40% of global carbon dioxide (CO₂) emissions. Around 50% of the total heat generated was consumed in industrial processes, while 46% was utilised in district heat for space and water heating. Combustion of natural gas provides a large share of this heat and will play a crucial role in decreasing emissions emitted by this sector. To reduce gas turbine generated CO₂ emissions, the replacement of fossil fuels is inevitable. A promising opportunity lies in the transition from hydrocarbon fuels to hydrogen (H₂). Not only does the combustion of H₂ emit no CO₂, carbon monoxide (CO) emissions are also avoided. Switching to H₂ and hydrogen natural gas fuel blends is accompanied by altered combustion characteristics, which need to be better understood. The goal of this thesis is to investigate the combustion behaviour of a newly developed multi-tube burner integrated in an existing can combustor. It is capable of burning hydrogen and natural gas mixtures. For this purpose, a simplified one-dimensional calculation model is developed to explore mass flows, pressure drops and velocities in the new system. The acquired data is subsequently used as input for a computational fluid dynamics model. Different modelling approaches are investigated to finally analyse the combustion behaviour of the system at base load with either H₂ or CH₄ as fuel. The simulations provide insights into parameter dependencies regarding flame front modelling. The computations highlight the feasibility of the technology concept for the chosen engine and that stable combustion is achievable. Furthermore, nitrogen oxides (NOₓ) emissions are analysed in post-processing calculations. These emphasise the importance of the thermal NOₓ generation path with flame temperatures close to 1800 K. Nonetheless, the threshold of 25 ppm is met for both fuels, with CH₄ combustion even reaching single-digit values. This project provides a modelling framework for a real-life test series of the current prototype burner combustor set-up. The conceptual basis helps to understand the expected combustion system behaviour as well as NOₓ emission levels.

Abstract: Prestressed concrete (PC) highway bridges represent an integral part of the transportation network and contribute significantly to socio-economic development. However, highway bridges are susceptible to Deterioration and thus exhibit structural deficiency after years of service, especially in the cold climate of North America (e.g., Alberta, Canada) where the de-icing salt is used seasonally and can heavily corrode roads and bridges. To facilitate the reliability-based safety assessment for both intact (e.g., as-built) and corroded PC bridge girders, reliable load-carrying capacity prediction models are required as a fundamental ingredient including both mechanics-based and data-based models. Firstly, a mechanics-based load-carrying capacity prediction model (i.e., a flexure-shear coupled fibre beam element) for intact PC girders was developed based on Timoshenko beam theory combined with multi-axial material models, as complementary to the conventional fibre beam elements without considering shear. The developed element was validated through a classic test series of shear-critical reinforced concrete (RC) beams from the literature and a PC girder recently tested under both shear-critical and flexure-dominated scenarios. Then, the developed element was applied to a representative nine-girder PC bridge in Alberta, Canada to study the bridge system behavior and load sharing of multi-girder bridges. Data-based shear capacity models for intact PC girders were then developed by adding probabilistic correction terms to existing deterministic design code models. In this research task, an experimental database containing 369 PC girders that failed in shear was compiled. Using the experimental database, shear capacity models from five concrete structure and bridge design codes were assessed, including ACI 318-19, AASHTO LRFD 2017, CSA A23.3:19, CSA S6:19 and fib MC 2010. Probabilistic correction terms were then calibrated and added to the design code models via Bayesian linear regression and Gaussian process regression approaches. The resulted models can benefit shear capacity predictions with better accuracy and precision, as well as reliability/fragility analysis of PC girders with the model error considered. Data-based load-carrying capacity models were also developed for corroded PC voided girders which are popular for short-span bridges in North America. Firstly, a 2D continuum-based FE model for corroded PC girders was developed and validated by existing experimental tests. Then, a virtual experimental database of 4,165 PC girder tests considering various design, loading, and corrosion conditions was generated based on the developed FE model. With the generated virtual experimental database, the probabilistic capacity reduction factor model and the load-carrying capacity model were developed via Gaussian process regression to study the corrosion effects on capacity reduction and failure probability of corroded PC girders, respectively.

The high pressure and high temperature (HP/HT) of operating fluid and soft soil content significantly account for the axial and lateral displacement of subsea pipelines. The ability of a pipeline to resist displacement depends on the soil strength. Due to low soil shear strength, the accumulation of displacement over a period of operating cycles leads to pipeline displacement. Increasing the pipe-soil interaction resistance will significantly reduce pipeline displacement. Soil contains solid, water and air particles. The levels of water, air and the solid particle size in the soil, govern its mechanical behaviour. Removal of pore water content from the soil voids may lead to consolidation with a resultant increase in effective stress. One of the methods used to increase soil strength is the Electro-Kinetic (EK) process. This is applied to increase the strength of onshore and offshore soil foundations. An important advantage is a reduction in time taken for the soil to consolidate. A Numerical model is developed for the determination of the EK effect on soft soil using the ABAQUS software tool. Two stages involved in the EK analyses are electro-osmotic consolidation and dynamic pipe-soil interaction. Three different test series each for electro-osmotic consolidation and dynamic analyses were built. The electro-osmotic consolidation analyses determined the soil consolidation followed by a dynamic pipe-soil interaction process. The electro-osmosis considered the effect of voltage variations, time taking for the soil to consolidate and variations with numbers of electrodes. The dynamic analyses consider the effect of electro-osmosis due to the displacement of pipeline in the vertical, axial, and lateral direction. From the electro-osmotic analyses, the soil settlement is due to its reduction in void volume as a result of the pore water pressure dissipation. A further interaction of pipeline on the (settled) consolidated soil indicates a significant improvement in the soil strength when compared with the non-treated soil.

Unmanned Ground Vehicles (UGVs) are becoming more widespread in their deployment. Advances in technology have improved not only their reliability but also their ability to perform complex tasks. UGVs are particularly attractive for operations that are considered unsuitable for human operatives. These include dangerous operations such as explosive ordnance disarmament, as well as situations where human access is limited including planetary exploration or search and rescue missions involving physically small spaces. As technology advances, UGVs are gaining increased capabilities and consummate increased complexity, allowing them to participate in increasingly wide range of scenarios. UGVs have limited power reserves that can restrict a UGV’s mission duration and also the range of capabilities that it can deploy. As UGVs tend towards increased capabilities and complexity, extra burden is placed on the already stretched power resources. Electric drives and an increasing array of processors, sensors and effectors, all need sufficient power to operate. Accurate prediction of mission power requirements is therefore of utmost importance, especially in safety critical scenarios where the UGV must complete an atomic task or risk the creation of an unsafe environment due to failure caused by depleted power. Live energy prediction for vehicles that traverse typical road surfaces is a wellresearched topic. However, this is not sufficient for modern UGVs as they are required to traverse a wide variety of terrains that may change considerably with prevailing environmental conditions. This thesis addresses the gap by presenting a novel approach to both off and on-line energy prediction that considers the effects of weather conditions on a wide variety of terrains. The prediction is based upon nonlinear polynomial regression using live sensor data to improve upon the accuracy provided by current methods. The new approach is evaluated and compared to existing algorithms using a custom ‘UGV mission power’ simulation tool. The tool allows the user to test the accuracy of various mission energy prediction algorithms over a specified mission routes that include a variety of terrains and prevailing weather conditions. A series of experiments that test and record the ‘real world’ power use of a typical small electric drive UGV are also performed. The tests are conducted for a variety of terrains and weather conditions and the empirical results are used to validate the results of the simulation tool. The new algorithm showed a significant improvement compared with current methods, which will allow for UGVs deployed in real world scenarios where they must contend with a variety of terrains and changeable weather conditions to make accurate energy use predictions. This enables more capabilities to be deployed with a known impact on remaining mission power requirement, more efficient mission durations through avoiding the need to maintain excessive estimated power reserves and increased safety through reduced risk of aborting atomic operations in safety critical scenarios. As supplementary contribution, this work created a power resource usage and prediction test bed UGV and resulting data-sets as well as a novel simulation tool for UGV mission energy prediction. The tool implements a UGV model with accurate power use characteristics, confirmed by an empirical test series. The tool can be used to test a wide variety of scenarios and power prediction algorithms and could be used for the development of further mission energy prediction technology or be used as a mission energy planning tool.

During recent decades, the use of aluminium lipped channel (ALC) beams as purlins, and floor joists in roof and floor systems in the construction industry has significantly increased due to their superior mechanical characteristics compared to steel, such as durability, light weight, high strength to weight ratio, and being weatherproof. However, despite these advantages, the elastic modulus of aluminium is only one-third that of steel. Hence ALC beams with shorter span lengths are vulnerable to buckling failures under concentrated load, such as shear and web crippling. On the other hand, ALC beams with longer span lengths can fail due to combined actions such as bending and shear actions, and bending and web crippling actions. In the past, the structural response of ALC beams has been investigated, but only under single actions of shear, web crippling, and bending. However, the behaviour of ALC beams subjected to combined bending and shear actions, and bending and web crippling actions needs to be investigated for real-world engineering applications. To address this research gap, experimental and numerical investigations on the strength and behaviour of ALC beams subjected to two scenarios of combined bending and shear actions, and combined bending and web crippling actions were conducted, and are presented in this thesis. The first step of the research focused on experimental investigation. Subsequently, numerical investigations including validation and parametric studies were carried out. Finally, the current available design rules were assessed and new design rules were proposed where needed. The experimental study comprised four test series of pure bending, web crippling, combined bending and shear actions, and combined bending and web crippling actions, using 12 different ALC sections. All ALC beams chosen for the experimental test program were supplied by BlueScope Permalite, Australia. The test specimens were fabricated by roll-forming method using aluminium alloy 5052-H36. A total of 62 tests were conducted on the ALC specimens, consisting of six four-point bending tests undergoing local buckling; nine web crippling tests under unfastened interior-one-flange (IOF) loading condition; 24 combined bending and shear tests considering two aspect ratios (ARs) of 1.5 and 2.0; and 23 combined bending and web crippling tests considering five interaction factors of 1.0, 1.5, 2.0, 2.5 and 3.0 under unfastened IOF loading condition. In the numerical study, nonlinear finite element (FE) models of ALC beams using ABAQUS/CAE software package were developed to simulate the behaviour of such beams under pure shear, web crippling, bending and combined actions. The developed FE models were validated by comparing the finite element analysis (FEA) results with those obtained from the tests. Good agreements were achieved throughout three criteria of ultimate capacities, applied load versus vertical displacement curves, and failure modes. The developed FE models were then used to undertake a detailed parametric study to obtain a large dataset of the strengths of the ALC sections with different parameters. The ultimate capacities of ALC beams obtained from the tests and FE models were compared with those predicted using current design rules of AS/NZS 4600, including direct strength method (DSM), AS/NZS 1664.1, AISI S100, Eurocode 3 Part 1-3, and the previously proposed design equations. It was found that the current DSM was safe in predicting the ultimate bending moment capacities of ALC beams undergoing local buckling. The previously proposed design equations were reasonably reliable in predicting the shear and web crippling capacities of the ALC beams. The available design equations in the form of circular and linear interaction curves provided by AS/NZS 4600 and developed in the previous study were too conservative in estimating the combined bending and shear capacities of the ALC beams. Hence, new design equations were proposed in the current study for the accurate prediction of the capacities of ALC beams under combined bending and shear actions. The current design rules of AS/NZS 4600, AISI S100, and Eurocode 3 Part 1-3 are not suitable to predict the combined bending and web crippling capacities of the ALC beams accurately. Therefore, new design equations were developed for the accurate prediction of the combined bending and web crippling capacities of the ALC beams under unfastened and fastened IOF loading conditions.

Civil engineers are presently faced with the challenge of strengthening and repairing many existing structures to assure or increase their structural safety. The reasons for this include changes in the use of structures, and increased traffic loads on bridges. In Iraq, for example, several highway bridges needed to accommodate increased axle load during the transportation of huge turbines for electricity generating stations. The requirement for structural strengthening and repair methods is, however, driven by the worldwide need to ensure the safety and sustainability of our aging infrastructure which is deteriorating at a rate faster than it can be renovated. The ever increasing damage caused by environmental effects and the corrosion of steel and deterioration of concrete, reduce structural safety and lead to disruption for the users, which can have serious economic consequences. In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), which are welded or, in older bridges, bolted or riveted together to form the vertical web and horizontal flanges of the beam. The two primary functions of the web plate in a plate girder are to maintain a relative distance between the top and bottom flanges and to resist the induced shear stresses. In most practical ranges of plate girder bridges’ spans, the induced shear stresses are relatively low compared to the bending stresses in the flanges induced by flexure. As a result the web plate is generally chosen to be much thinner than the flanges. The web panel consequently buckles at a relatively low shear force. For steel girder structures dominated by cyclic loading, as is the case with repeated vehicle axle loads on bridges, this can lead to the so-called ‘breathing’ phenomenon; an out-of-plane buckling displacement that can induce high secondary bending stresses at the welded plate boundaries. In the current work, a novel FRP strengthening technique using bonded shapes is applied to resist these out of plane deformations, and hence reduce the breathing stresses, and improve the fatigue life of the plate girder which is very different to the majority of applications of FRP strengthening that exploit the FRP for its direct tensile strength and stiffness. The objective of the current experimental programme is to strengthen thinwalled steel girders against web shear buckling using a corrugated CFRP or GFRP panel bonded externally along the compression diagonal of the web plate. The programme was divided into three main phases, including: (1) the development of a new preformed corrugated FRP panel, and (2, 3) testing its performance in two main experimental series. The initial series involved tests on 13 steel plates strengthened with the proposed preformed corrugated FRP panel and subjected to in-plane shear loading using a specially manufactured “picture-frame” arrangement designed to induce the appropriate boundary conditions and stresses in the web plates. This initial test series investigated the performance of different forms of strengthening under static load, in preparation for another series of cyclic tests to investigate their fatigue performance. The test variables included FRP type (CFRP or GFRP), form of FRP (closed or open section), number of FRP layers, and orientation of GFRP fibres used to produce the FRP panel. In the second series, six specimens were manufactured to simulate the end panel of a plate girder. These were strengthened with the optimized FRP panel from the initial series and tested for shear buckling under repeated cyclic loading with a stress range 40-80% of the static ultimate capacity. A considerable increase in the stiffness of the strengthened specimens is evident in the observed reductions of the maximum out-of-plane displacement. The stiffness of the strengthened specimens is assessed to be increased by a factor ranging between 3 to 9 times the stiffness of the corresponding unstrengthened specimen, depending upon the type of the FRP panel used and the aspect ratio of the tested specimens. The breathing phenomena is also significantly reduced, consequently the surface, membrane and secondary bending stresses are reduced. The 45° strengthening scheme succeeded the best both in reducing the breathing stresses and increasing the ultimate shear capacity of the specimen by 88%. Fatigue analyses indicated that the proposed strengthening technique is able to considerably elongate the life expectancy of the strengthened plate girders by a factor ranging between 2.5 and 7 depending on the applied cyclic load amplitude. In addition, the proposed strengthening technique did not show any debonding or delamination under both static and cyclic loading which makes it a good candidate for strengthening thin-walled structural members, especially, when ductility is a concern. In fact, the proposed strengthening technique succeeded in improving the energy absorption capacity of the strengthened specimens by a factor ranging between 1.5 and 2.5 times the corresponding control specimen which means that the ductile failure type associated with shear buckling of steel plate girders is not only maintained, but it was improved as well. This type of ductile failure is not common in other types of FRP strengthening techniques. Finally, a geometrical and material non-linear finite element model is presented both for the steel and composite sections which showed very good correlation with test results and was capable of predicting both the strength and deformational behaviour of the tested specimens. This numerical model is used for a parametric study to support the proposed design method.

The current project represents the first attempt to test the environmental performance of the direct utilisation of purified used cooking oil as a fuel in a heavy goods vehicle under real world driving conditions. The properties of the used cooking oil were different from those of petroleum diesel (PD) standards however, its heat value, carbon footprint reduction potential and low cost were the key incentives driving it’s use as a fuel. The current research was a collaborative project between Convert to Green (C2G), the fuel provider, the United Biscuits Midlands Distribution Centre, the heavy goods vehicle provider and the University of Leeds as the scientific consultant and research executor. The brand of used cooking oil was Convert to Green Ultra-biofuel (C2G UBF) tested on a Mercedes-Benz EURO 5 emissions standard compliant 44 tonne articulate heavy goods vehicle (HGV). The HGV was modified for on-board UBF heating and mixing with PD. UBF was heated by heat recovery from the engine cooling system. The results showed that the UBF/PD blending ratio was 0.845 as a journey average for the entire test series. However, the HGV was recorded to run on 100% UBF at steady high speed on the M1 motorway in the Midlands region of the UK. There were no discernible deficiencies in the HGV’s performance or its traction effort. Nevertheless a slight increase in specific fuel consumption (SFC) was detected for the blended fuel. Engine durability, combustion chamber deposits and maintenance frequency were not affected by the UBF content in the fuel. Although the engine technology was designed to suppress particulate matter (PM) within the combustion process, the use of blended UBF further reduced the tailpipe PM emissions compared to the use of PD. Carbon monoxide emissions decreased when using the blended fuel, while nitrogen oxides, total hydrocarbons and carbon dioxide increased compared to PD emissions. The benefits of UBF utilisation as a fuel lie in the huge carbon savings and reduced PM emissions when compared to the use of PD as well as its use in providing a cost effective fuel supply and waste management technique.

Concrete is one of the most commonly used building materials in the world because of its excellent versatility. The concrete consumption has increased considerably because of the rapid urbanisation development. Annual cement consumption is expected to increase to 5.2 billion tons by 2050. An average of 850 kg of carbon dioxide can be released into the environment to produce one tone of clinker. To minimise the disadvantages of cement production, one option is to use Supplementary Cementitious Materials (SCMs) such as fly ash and ground granulated blast furnace slag (GGBFS) to partially replace cement in concrete. Accordingly, this thesis extensively focuses on the research of time-dependent behaviour such as shrinkage and creep of blended cement concrete containing high volume of fly ash and GGBFS. To advance the understanding of volumetric changes in concrete mixes with high volume of fly ash and GGBFS, the presented research focused on five areas: (a) autogenous, drying and total shrinkage of concrete; (b) tensile stress development of concrete in restrained ring test; (c) tensile creep of concrete; (d) nonlinear tensile creep of concrete; and (e) thermal cracking of concrete. The first part of this dissertation reports the autogenous, drying and total shrinkage results of a total of 21 concrete mixes with a high volume of fly ash and GGBFS using concrete prisms. The experimental results were also compared to the predictions by Australian Standard AS3600 (2009 and 2018 versions) and Eurocode 2. Additional tests on pastes with the same SCM content were conducted to investigate both autogenous and chemical shrinkage in relation to their time-dependent pore structure refinement assessed using the nitrogen adsorption isotherm technique. For concrete with a characteristic compressive strength lower than 50 MPa, the autogenous shrinkage of concretes with 40-60% GGBFS was significantly higher than that of reference concretes mostly due to a later increase in the autogenous shrinkage between 28 and 100 days. No clear difference in autogenous shrinkage was observed for GGBFS concretes with a compressive strength greater than 50 MPa. Autogenous shrinkage of fly ash concretes was overall equivalent to that of reference concretes. However, the drying shrinkage of concrete mixes with SCMs was significantly lower than that of reference concretes, leading to an overall reduction in total shrinkage for most of the concretes with SCMs. Some amendments to the shrinkage model in AS3600 are proposed to improve the estimation of both autogenous shrinkage and drying shrinkage of high-volume fly ash or GGBFS concretes. The restrained ring test is conducted to determine the early age cracking performance of blended cement concrete with the same SCM content under standard conditions. An analytical model for the analysis of the restrained ring test is proposed, capturing the effect of both restrained shrinkage and tensile creep based on the age-adjusted effective modulus theory. The analytical model allows for accurately predicting the tensile stress of the restrained concrete ring based on the experimental measurements of the time-dependent development of elastic modulus, total free shrinkage, and tensile creep of concrete. A numerical finite element simulation was also successfully carried out to validate the new analytical model. The dog-bone test was carried out to determine the tensile creep of blended cement concrete with the same SCM content under standard conditions. It was observed that the tensile creep of fly ash concretes was slightly lower than that of the reference mixtures without SCM. For GGBFS concrete, the higher the GGBFS content, the higher the tensile creep. The experimental results were compared with existing creep models and a tensile creep model was then proposed to improve the prediction for concretes with fly ash and GGBFS. The new model was calibrated only for controlled environmental conditions (23 °C and 50% RH) and was validated to analyse the development of concrete tensile stress in the restrained ring test. The nonlinear tensile creep behaviour of ultra-high performance concrete (UHPC) is further evaluated using dog-bone specimens. The tensile creep test series were subjected to three tensile stress levels (40%, 60% and 75%) and loaded at the age of 2 and 28 days after curing. The experimental results were compared with the values calculated based on various existing prediction models (ACI-209R-92, GL 2000, AS3600-2018, and Eurocode 2). In addition, some simple analytical models from the literature for calculating nonlinear creep coefficient were also compared with the experimental values. A nonlinear tensile creep model was proposed for UHPC allowing a better prediction of the experimental results. Finally, the thermal cracking resistance of concrete mixes with fly ash and GGBFS is investigated using a rigid cracking frame (RCF) with a computer-controlled temperature profile. RCF was used to evaluate the coupled effects of restrained shrinkage, tensile creep and temperature. The temperature profile is determined using the software ConcreteWorks at the centre point of the concrete specimen. The free shrinkage frame (FSF) and match-curing oven followed the same temperature profile used in RCF test to measure the free total deformation and time-dependent mechanical properties of concrete, respectively. Autogenous shrinkage was measured using concrete prisms. Basic tensile creep was computed according to the modified FIB 2010 model. An analytical model was proposed to calculate the autogenous shrinkage induced and thermal stress separately. The time-dependent ratio and risk coefficient to analyse the early-age cracking of concrete are also performed.

Plastic bonded explosives are unique materials with complex properties. Research has deeply explored the reactive nature of these materials, but their mechanical performance has been largely neglected. Due to the aggregate composition of solid crystals covered in polymer binders which are heated and pressed into parts, the mechanical response of these materials is extremely complex. The primary objective of this thesis was to develop a unique fixture to allow for a smaller explosive specimen to be installed and tested under multiaxial loading conditions. The design was heavily dependent on set requirements as well as production and use preferences, and a thorough analysis was performed to verify the fixture correctly loaded the specimen without concerns of fixture damage or improper loading due to excessive strain across the fixture. Once fabricated, a test series was conducted on explosive specimens to validate the fixture’s capabilities and provide an initial look at the mechanical response of a complex aggregate material loaded in various combinations of stress states.Analytical methods were again relied on to convert load data to an expected stress state in the unique geometry to provide a first look at the material response.

The performance of structural timber connections is of utmost importance since they control the global response of the building. A ductile failure mechanism on the global scale is desirable, especially in the design of structures in seismic areas, where dissipative components in which ductile failure modes need to be ensured are considered. Therefore, the knowledge of possible brittle failure modes of connections is crucial. The paper investigates the brittle failures of laterally loaded dowel-type connections in cross-laminated timber subjected to tensile load in a lap joint configuration through experimental investigations and analytical estimations. A set of 13 different test series has been performed with fully threaded self-tapping screws of 8 mm diameter and different lengths (40 to 100 mm) in cross-laminated timber composed of 3 or 5 layers (layer thickness range from 20 to 40 mm), giving rise to the activation of different brittle failure modes at different depths. Plug shear was among the most typically observed failure modes. A previously proposed model for the brittle capacity was applied to the tested connections at the characteristic level. As shown by the performed statistical analysis, the existing model is not reliable and mainly unconservative. A very low performance is observed (CCC = 0.299), but with a good cor- relation (c = 0.750) for the tests in the parallel direction. Further research work is required to improve the current model predictions and to gain a better understanding of the underlying resisting mechanisms.

The basic assumption of the radiocarbon dating method is that the carbon-14 concentrations in the atmosphere have remained essentially constant in the past although there is some evidence that fluctuations have occurred during the past 10 millennia. These fluctuations are reflected in biospheric and oceanic carbon-14 concentrations since the distribution of carbon-14 is controlled by the exchange processes between the respective reservoirs. A precise knowledge of these exchange rates is desirable, therefore, if past carbon-14 fluctuations are to be explained and future carbon-14 concentrations predicted. Evaluation of these parameters also yields important data for the study and understanding of meteorological, biological and oceanographic processes. Some estimates of exchange rates have been made on the basis of measured carbon-14 variations during the past 20 years as a result of the Suess effect. Further studies have been based on the artificial carbon-14 produced prior to the major test series of 1961-62. During 1961-62 large-scale atmospheric testing of thermonuclear devices produced substantial quantities of carbon-14 through the interaction of escaping neutrons from the weapons with atmospheric nitrogen, 14N (n1H) 14C. Prior to 1961 the amount of carbon-14 produced by nuclear weapons amounted toonly about one third that produced in the new test series. Thus the most recent amounts produced can be regarded as a new tracer for the study of the distribution and exchange rates of carbon dioxide between the various dynamic carbon reservoirs, i. e., the troposphere) stratosphere) ocean surface layer, deep ocean and biosphere. During 1967 and 1968 extensive measurements were madeof the carbon-14 concentrations in tropospheric carbon dioxide samples collected at a world-wide network of sampling stations. These results) together with the stratospheric and oceanic data have been used to calculate the inventories of artificial carbon-14 in various reservoirs of the carbon cycle for July 1967 and 1968. Residence times of carbon dioxide in various reservoirs of the carbon cycle have also been studied using a number of "chain" and "cyclic" models of varying complexity. The calculated exchange rate parameters indicate that both the ocean and biosphere are important in determining the atmospheric carbon-14 level. The magnitude of the exchange processes between the atmosphere and each of these reservoirs are comparable. However, the relatively large size of the oceanic reservoir suggests that this is the major controlling factor over the long term.

This thesis describes work carried out on the properties of plain concrete under uniaxial tensile stress, using the test method previously developed at University College. In the first chapter a review is made of the present state of knowledge of the structure of concrete, shrinkage and creep properties, and the behaviour of concrete under short-term loading, wherever possible comparing properties under tension and compression. 'The importance of cracking is also discussed. An initial test series was carried out to determine the effectiveness of the test method, and its inherent variability. It proved to be satisfactory in both respects. Strains were measured by internal vibrating wire gauges, which were found to have a small, but significant effect on failure stress. This, however, could be allowed for. The main test series was designed to assess the effect of shrinkage (for a period of up to 21 days) and creep (for a period of up to 14 days at 35% ultimate load) on the short-term failure properties (stress, strain and Young's modulus) of seven different mixes. Specimens could be under immersed, sealed or air drying ambient conditions. The results show that any variation in properties is not significantly greater than the inherent variation of the test system. The influence of mix proportions and curing conditions on the tensile short-term failure properties and the ultrasonic pulse velocity of the concrete is discussed. The third test series was designed to study the effects of tension on several well-known phenomena of compressive creep, i.e. creep recovery, combined creep and shrinkage, creep under fluctuating humidity, and creep at all levels of loading up to 90%of the ultimate short-term strength. Similar trends to those in compression were observed, and existing theories of creep, and the influence of cracking are examined in the light of these results.

Worldwide, many rivers are affected by various river engineering measures and exhibit ecological deficits as a result. Sediment input from upstream is often limited by the presence of hydropower plants, sediment retention basins, and other river training measures, resulting in a lack of bed-load and morphological degradation. Sediment deficit can undermine structures, negatively influence groundwater formation, and decrease habitat quality for aquatic flora and fauna. Sediment replenishment by means of artificial gravel deposits or enhanced by bank erosion are two options when attempting to compensate for sediment deficits in rivers and to improve their ecological conditions. The ability to predict bank erosion rates and their impact on the river reach are important when attempting to implement restoration projects successfully. In the first part of this study, experiments are conducted on the erosion pattern of artificial gravel deposits to (i) investigate the influence of the governing parameters on the erosion process of gravel deposits, (ii) improve understanding of fluvial bank erosion in case of non-cohesive, granular bank material, and (iii) identify the fundamentals to implement and improve bank erosion in numerical models. In a second test series, the ability of non-submerged structures to enhance bank erosion is evaluated. Erodible and non-erodible structures are tested to obtain bank erosion volumes that are favourable from river engineering and ecological perspectives. In a third test series, the long-term evolution of the bed of a typical Swiss river as a result of changing sediment supply is investigated. Predicting equations intended to describe the erosion pattern of artificial gravel deposits and to estimate the backwater rise that occurs due to gravel deposits are proposed. This study demonstrates that an excess shear stress relation can describe the temporal evolution of the mean erosion rate of an artificial gravel deposit. Non-erodible structures perpendicular to a river’s bank and groins on the opposite bank are efficient to enhance bank erosion for discharges where no or negligible bank erosion occurs without a structure being present. The introduction of large wood debris jams is a promising option for enhancing bank erosion, as this approach combines low maintenance requirements with the immediate creation of complex habitats. In the third test series, channel responses to a long-term change in sediment supply took the form of a combination of (i) an adjustment on the grain scale by a smoothening of the bed; (ii) a change of the cross-sectional shape by sediment deposition, primarily in the thalweg; and (iii) and a reduction of the longitudinal bed slope. This study’s findings allow for improved predictions of the rate and magnitude of bank erosion and their subsequent impact on the downstream river reach; thus, they can consequently aid in determining design frequency and deposit volumes for planned restoration projects.

This thesis firstly examines the demountability and performance of the conventional steel column connections under various loading conditions through the developed finite element model, with which the accuracy of the behaviour prediction for the steel column connections can be significantly improved. The concept of demountability of these steel column connections is firstly involved into the design consideration. The extensive analytical and numerical investigation on the steel column connections can be categorised into steel column-column connections; bolted steel column-base connections and embedded steel column-base connections. Effects of a series of major design parameters on the behaviour and demountability of these steel column connections are evaluated, and design recommendations are included. In addition to the investigation on connections along steel columns, this thesis attempts to propose an innovative connection for concrete-filled steel tubular (CFST) columns, through which the CFST columns can be readily dismantled at the end of their service life. For the proposed demountable connection, a number of blind bolts are utilised to connect four separate side-plates with the CFST columns. In contrast to the existing connections of CFST columns, a pre-welded baseplate was included to separate the top and bottom CFST columns, consequently ensuring the ease of dismantling. Two series of experimental tests are thereafter conducted on the proposed demountable CFST column-column connections to demonstrate their mechanical performance satisfying the existing codes of practice. In the first test series, eight demountable CFST column-column connections are subjected to axial compression and three other specimens are subjected to compression combined with bending moment. Similar specimen configurations are replicated in the second test series except that instead of compression, an eccentric tensile loading was introduced to the demountable CFST column-column connections. Effects of various design parameters on the behaviour of the demountable CFST column-column connections are investigated for both test series. Furthermore, finite element models that accounts for the geometric and material nonlinearities are developed to predict the behaviour of the demountable CFST column-column connections. Extensive finite element analysis are carried out to enhance the understanding of the experimental results by demonstrating the failure modes of the connection and by extending the experimental results through analysis of a series of parameters that are not investigated in the test. Results obtained from this thesis indicate that the developed finite element models for conventional steel column connections are accurate, particular for the cases where seismic loading is introduced. Demountability can be achieved for these steel column connections with existing design methods, providing proper guidance is followed. Moreover, results emanating from the experimental tests on the proposed CFST column-column connections demonstrate that CFST columns can be easily dismantled and safely reused. The design axial and flexural strength of the demountable CFST column-column connections satisfy the current codes of practice. It is believed that the findings in this thesis are useful in promoting the concepts of demountable connections to be widely used in future engineering practice.

Widespread urbanisation of communities has led to a need for increased urban infrastructure. Surface space constraints in urban areas have resulted in new infrastructure being increasingly moved underground. Significant tunnel construction, using various tunnelling techniques, has been undertaken in a number of major cities in recent years. The ground is subjected to stress relief during tunnelling; this propagates through the soil to the foundations of buildings and infrastructure close to and above the tunnel. The interaction between these movements and the foundations is important for assessing movements and any subsequent damage to the overlying structures. Research has historically focussed on shallow foundations, with deep, or piled foundations, receiving less attention. Investigations into the effects of tunnelling on piled foundations have, in the past, concentrated on tunnelling adjacent to piles and the effect on pile bending. Where work has been undertaken for tunnelling directly beneath piles, this has been directed at driven piles. As pile driving is less desirable in urban areas, owing to noise and vibrations, bored piling is becoming increasingly prevalent. As a result, the focus of this research has been the effect of tunnelling beneath bored piles in clay. Centrifuge modelling was used to investigate the effects of tunnelling on bored piles in clay. A new centrifuge package, including an innovative new model pile, was designed to simulate tunnelling on bored piles in clay. Particle Image Velocimetry (PIV) was used to monitor the soil and pile movements when tunnelling volume losses were simulated. The effects of pile-soil relative stiffness, pile factor of safety and the positioning of the piles relative to the tunnel were all investigated as part of the test series. Pile factor of safety was seen to have a significant effect in determining the pile head settlement when subjected to tunnelling movements. Pile positioning was also shown to be important, as were the effects of pile-soil stiffening and interaction effects between piles. Two case studies, from the Crossrail project in London, are presented for tunnelling on piled structure in clay. The case study at 4-18 Bishops Bridge Road (BBR) showed the effects of earth pressure balance (EPB) tunnel boring machine (TBM) tunnelling on an overlying piled building. The other case study at Kempton Court showed the effects of sprayed concrete lining (SCL) tunnelling on an overlying piled building. Both of the buildings exhibited displacements which followed the `greenfield' surface settlements. A number of analytical models were compared with the centrifuge results, with most able to predict aspects of the data. The need for plasticity within the analytical models was highlighted. The importance of correctly modelling the pile base was also shown as this could lead to unconservative predictions if ignored.

Understanding the mechanical performance of additively manufactured aerospace metals is of paramount importance for the development of new structural materials and next-generation aerospace components. Of particular interest in this investigation is the titanium alloy Ti-6Al-4V produced using laser powder bed fusion (LPBF), and its structural integrity in the event of sudden aerospace-related impacts. These impacts, known as foreign/domestic object damage, can cause catastrophic damage to aircraft components and serious injuries to passengers. To enable simulation-aided design and analysis for foreign/domestic object damage survival, the overarching goal of this project is to develop a stress-state-dependent ductile fracture model for LPBF Ti-6Al-4V that is representative of the material’s behavior across a broad range of loading conditions. The foundational steps presented in this thesis include the design of an experimental program to calibrate the LPBF Ti-6Al-4V fracture locus, a three-dimensional representation of the variation of equivalent plastic strain at fracture with stress triaxiality and Lode parameter, commonly utilized in continuum damage models. The proposed experimental program provides a family of mechanical tests that employ different specimen geometries (e.g., notched plane stress, plane strain, axisymmetric, and thin-walled tube specimens) and loading conditions (e.g., tension and torsion) to access a broad window of stress states (triaxiality and Lode parameter combinations). Six axisymmetric tension specimens were chosen from the aforementioned family of candidate specimen designs for subsequent mechanical testing and stress state analysis. The grain morphology and porosity of the LPBF-printed Ti-6Al-4V material was characterized using electron backscatter diffraction (EBSD) and X-ray computed tomography (XCT), respectively. Quasi-static mechanical testing was performed on a servo-hydraulic load frame, with full-field surface strains measured using three-dimensional digital image correlation (DIC). The effective plastic strain (EPS) at fracture for each test (thirty total, with five runs for each of the six specimen geometries) was obtained through direct DIC measurements and the customary plastic incompressibility assumption. Traces and weighted average values of the stress state parameters (triaxiality and Lode parameter) over the plastic deformation history were obtained from parallel numerical simulations of each test. Acceptable agreement between simulation and experiment – as quantified by comparing force-displacement and principal strain-displacement curves – was observed across the majority of the test series. However, a general trend was noticed across the force-displacement plots where the simulations predicted sometimes meaningfully higher yield stresses and ultimate tensile stresses than the experiments. This discrepancy is attributed to the material constitutive modeling and/or specimen metrology. Arithmetic averages of the stress state parameters and EPS at fracture were reported across the five tests performed for each specimen geometry. A trend of the EPS at fracture (ductility) decreasing with an increasingly negative (tensile) triaxiality is observed, consistent with a significant body of previous literature in the ductile fracture community, including previously published results on wrought Ti-6Al-4V. The research presented in this thesis complements the few existing studies on ductile fracture of LPBF Ti-6Al-4V, providing additional fracture data that can be used to calibrate tabulated or parameterized ductile fracture models used in predictive simulations of aerospace-related structural impacts.

Mechanical behavior of the composite material T800/F3900, a strengthened epoxy carbon-fiber reinforced polymer, is investigated in multiple types of loading conditions at various strain rates. The objective of the project is to generate experimental data for calibration of the material model, MAT_213, in LS-DYNA for better predictive accuracy of the composite material in numerical simulations. Anisotropic material properties, strain rate effects and geometry effects are studied. In-plane and out-of-plane tension and compression tests are conducted at strain rates ranging from 0.001 1/s to 1000 1/s. In-plane shear experiments are performed to learn shear characteristics of the material in 1-2 and 2-1 directions. In-plane tension, compression and shear test samples are cut from a 0.125” 16-ply panel, and out-of-plane tension and compression test samples are cut from a 0.7” 96-ply panel. Strain rate effects are noticeable in compression in the 90-degree and through thickness orientations, and more test data is required to see if strain rate effects exist in tension in the transverse direction. Anisotropic mechanical behavior is also significant in each orientation. Four geometries of tension test samples are attempted in tension test series since pre-mature failure is seen taking place in tension test samples. Tension test data from each geometry are studied and compared in order to learn how geometry influences the mechanical responses. Double notch shear specimen is used for investigating in-plane shear properties of the material. The physical loading conditions applied on the test samples and failure modes in 1-2 shear and 2-1 shear experiments are studied in the shear test series. Two-dimensional and three-dimensional Digital Image Correlation are used to measure full field strains. Numerical simulations are done using LS-DYNA for investigating the hydrostatic stress states at the endpoint of the parallel gage section of the tension dobgone test samples. Strain states from simulation results are also compared to DIC measurement data.

The different technologies of passive cooling concepts have to rely on a good thermal coupling between a building's thermal mass and indoor air. In many cases, the ceiling is the only surface remaining for a good coupling. Further research is necessary to investigate discrepancies between existing correlations. Therefore, the overall aim of the work described in this thesis is the investigation of heat transfer at a heated ceiling in an experimental chamber. Acoustic baffles obstruct the surface of the ceiling and impede heat transfer. However, there is nearly no published data about the effect of such baffles on heat transfer. Available results from simulations should be verified with an experimental investigation. Consequently, one of the primary aims of this work was to experimentally determine the influence of such acoustic baffles. A suitable experimental chamber has been built at Biberach University of Applied Sciences. The thesis describes the experimental chamber, the experimental programme as well as results from five different test series. With a value of ±0.1Wm⁻²K⁻¹ for larger temperature differences, uncertainty in resulting convective heat transfer coefficients for natural convection is comparable to that of results from an existing recent experimental work often recommended for use. Additionally, total heat transfer (by convection and radiation) results are presented. Results are given for natural, forced and mixed convection conditions at an unobstructed heated ceiling. Furthermore, results for acoustic baffles in both an unventilated and a ventilated chamber are shown. Natural convection results show a very good agreement with existing correlations. Under mixed convection conditions, convective heat transfer at an unobstructed ceiling decreases to the limiting case described by natural convection. Installation of acoustic baffles leads to a reduction in total heat transfer (convection and radiation) between 20% and 30% when compared to the case of an unobstructed ceiling.

The research presented in this thesis examines various aspects on connections and joints in Pultruded Fibre Reinforced Polymeric (PFRP) structures. The work is divided into two experimental investigations on the determination of pin-bearing strength and the characterisation of dowel connections and joint for the Startlink Lightweight Building System (SLBS). To support the development of a strength formula for bearing resistance in bolted connections two pin-bearing strength test series were conducted to study the effects of load orientation and hot-wet conditioning. The limitations of existing standard test methods are exposed from a critical review to show that they do not specify the need for a clearance hole, the range of bolt diameters and PFRP thicknesses found in practice. Because the size of tension coupons is found to be too big to be cut from standard structural profiles an alternative test method, having a smaller coupon size, is needed for every pin-bearing strength to be quantified by testing. Reported in this thesis are test results using an in-house test method that requires a maximum blank coupon of 100 mm × 125 mm. Characteristic strength are determined using Annex D7 of Eurocode 0. Pin-bearing strengths for load orientations of 0, 5, 10, 20, 45 and 90o, to the direction of pultrusion are obtained for a web material taken from a standard wide flange section of 9.53 mm thick. In the test matrix there were four sizes of pin diameter from 9.7 mm to 25.4 mm and a minimum clearance hole of 1.6 mm. The in-house test method is shown to satisfactorily determine pin-bearing strength. Another finding from this study is that the Hankinson formula cannot be applied to establish pin-bearing strength at any orientation on knowing the two characteristic strengths at 0o and 90o. To characterise the effect of hot-wet conditioning 0, 45 and 90o specimens were immersed under water for 3000 hours at 40° C. It is found that the average reduction in characteristic strength is in the range of 18 to 31%. The extent of strength reduction is found to be independent of pin size, except when the diameter is 25.4 mm. The second experimental investigation is for fact finding strength tests towards the application of PFRP dowelling as a method of connection in SLBS. This innovative building system has been engineering for the execution of a FRP house that meets the requirements for code level 6. A series of static coupon-sized tests were conducted to determine the minimum resistance of dowel connections similar to those used in the Startlink house. These results were used to verify the structural engineering design calculations. Another sub-assembly test configuration was used to determine the moment-rotation characteristics of joint details for the portal frame in the SLBS house. Four different beam-to-column joints with dowel connections, and with and without adhesively bonded connections, were statically loaded so that their rotational stiffnesses and modes of failure could be determined. The main conclusions from this study are that: -- all joints had adequate strength against the design ULS moment; -- only when the joint had adhesive bonding between the overlapping beam and column members does the rotational stiffness approach the design rigid condition; -- when clearance holes are present the rotational stiffness is low and applying adhesive bonding around the dowels cannot remove this structural limitation.

In this work experimental and numerical investigations were conducted on seismic behaviour of steel plate shear wall systems (SPSW) with and without cut-outs. Medium-scale specimens with moment-resisting connections between beam and columns and specific edge connections for fish plates were designed and constructed. The specimens were subjected to the cyclic quasi-static load. A loading system and proper lateral bracing unit was designed and built to apply the loading history according to ATC-24 protocol. Nonlinear finite element analysis models with dynamic formulation were developed to analyse test specimens. The results were validated with available published test results from other researchers. After validation, the model was used for estimating the maximum load required for testing of specimens. The efficiency of the method was finally proved by comparing the pushover and hysteresis analysis results with tests carried out in Kingston University's lab. The test series comprised frame-only, steel plate shear wall with two different types of steel plate and corresponding specimens with circular cut-outs in the steel plates, GFRP-steel Sandwich Shear Walls (GSSW) with different GFRP lay-up, GSSW with cut-outs and finally the steel plate shear wall with cut-out and optimally designed steel stiffeners, The specification of boundary members and the type of connections was kept unchanged in all specimens. The effectiveness of utilising the GFRP plies and steel stiffeners for improving the seismic performance of steel plate shear walls with and without cut-outs was explored. The effectiveness of these methods for enhancing the initial stiffness and ultimate load capacity of specimens with no noticeable requirements for increasing flexural stiffness for columns was verified.

This research investigated the longitudinal shear transfer mechanism in composite shallow cellular floor beams. The shear transfer mechanism is different with the headed shear studs used in composite construction. The shear resisting properties and behaviour of the shear transfer mechanism has not been studied previously. Experimental and analytical studies were carried out with the aims of improving and optimizing the design details, and advancing the method of shear connection in shallow floor beam construction. The composite shallow cellular floor beam investigated in this research is a new type of beam fabricated by welding two highly asymmetric cellular tees along the web. The shear connections of this type of composite beam are formed by the web openings, which transfer longitudinal shear force. Four types of these shear connections were studied: concrete-infill-only, tie-bar, ducting and web-welded-stud shear connections. In total, 24 push-out tests were performed in two test series to investigate the load-slip behaviour and shear resistance of the shear connections under direct shear force. The failure mechanisms of the two forms of shear connections were extensively studied, which lead to the development of a design method for the composite action. The concrete infill element passing through the web opening is subject to a complex three-dimensional stress state, and it is difficult to analyse it using the mathematical model rather than empirical formula. Finite Element Analysis of the concrete-infill-only shear connection was performed with a parametric study to further verify the design method that has been developed. Two flexural tests were carried out on a full-scale composite shallow cellular floor beam with a solid slab. The shear connections investigated in the flexural tests were: concrete-infill-only and tie-bar shear connections passed through the web. The behaviour and performance of the shear connections in the flexural tests were compared with those in the push-out tests. The degree of shear connection of the two flexural tests was determined in the back analysis using plastic theory with measured material properties. Based on the findings of the push-out tests and flexural tests, two design methods of deflection check and moment resistance were developed for composite shallow cellular floor beams at the serviceability limit state and the ultimate limit state respectively. The deflection check design method is based on the uncracked section properties of the composite beam. The moment resistance design method developed in this thesis is compatible with the design methods of BS5950 and Eurocode 4 (EC4).

Automotive crashes are a leading cause of death in the US, with side-impacts being the most fatal. Thoracic injuries are among the leading causes of such fatalities in small, elderly females. Thus, a series of six realistic side-impact post-mortem human surrogate (PMHS) sled tests were conducted. Results showed serious thoracic injuries in all PMHS, despite current side-impact anthropomorphic test devices (ATDs) predicting a The objectives of this study were to investigate the following in small, elderly female PMHS: 1) discrepancies between existing injury risk assessment tools and actual injury outcomes; 2) the effects of seatbelt pretensioners on thoracic injury; and 3) the effect of combined loading from the seatbelt pretensioner and side airbag on thoracic injury in side-impact.Prior to PMHS testing, SID-IIs ATD tests were run to match conditions to the previous study. A foam-padded pneumatic lateral impactor was used as a repeatable airbag surrogate. Three PMHS were tested, each under three different loading conditions: 1) A/P-only (seatbelt pretensioner), 2) lateral-only (airbag surrogate), and 3) combined loading (both). Anterior and posterior aspects of right and left ribs were instrumented with strain gages to detect potential fractures and fracture timing. Chest deflection was measured by axillary- and xiphoid process- level chestbands. Seatbelt load and spine motion were also measured. An anatomical dissection was completed after each test series to document all injuries.Each PMHS first underwent an A/P-only test, resulting in A/P chest compressions of 7-12% and no rib fractures. While the goal was to conduct one lateral-only and combined loading test per PMHS, number of tests and impact energy varied due to detected rib fractures or lack thereof. PMHS 1 only experienced one 4.9 m/s lateral-only impact due to 5 rib fractures occurring at 11% half-lateral compression. PMHS 2 underwent three lateral-only and two combined tests. Half-lateral compressions ranged from 4-8% for lateral-only and 7-8% for combined tests; 2 rib fractures occurred after the third lateral-only impact at 3.2 m/s. PMHS 3 underwent two lateral-only and one combined test. Half-lateral compressions measured 6-9% for the lateral-only and 7% for combined. PMHS 3 had 6 rib fractures in the second lateral-only impact at 3.0 m/s.Poor prediction of input impact energy from SID-IIs tests suggested low ATD biofidelity. A/P-only tests revealed that pretensioners alone do not likely cause rib fractures in fragile occupants. The high frequency of rib fractures in lateral-only tests restated the need for demographic-specific injury risk criteria. Strain gage data in combined tests showed initial tensile strain in the impact-side ribs that became compressive, indicating dynamic loading. Combined loading also reduced rib strain magnitude despite constant chest deflections. While these findings may imply an increased thoracic injury risk under combined loading, future work is needed to fully understand the underlying injury mechanism.

Background: Fluorides are commonly used for caries prevention in everyday life. Although the exact mode of action has not been clarified until now. Question: In the context of this study, it was examined to what extent under different conditions a homogeneous, stable fluoride layer can be generated on enamel. In addition the influence of the pellicle on the fluoridation was investigated. Methods: For the fluoridation, 1,000 ppm and 10,000 ppm solutions were made of the pure substances olaflur or stannous fluoride. The generated fluoride layers and their distribution were visualized using scanning electron microscopy and the fluoride content was measured using energy-dispersive X-ray spectroscopy. The 5-minute incubation of the enamel specimens with the respective fluoride solution was always carried out in-vitro. The persistence of the generated fluoride layer was investigated using in-vitro as well as a combination of in-vitro and in-situ experiments. As part of the in-vitro test series, after fluoridation, the enamel specimens were exposed to different intensive in-vitro cleaning protocols with distilled water (5 s, 6 x 5 min, 1 h, 5 min ultrasonic bath, 24 h) and compared with each other. Within the combined in-vitro and in-situ experiments, the influence of the pellicle was examined with the 10,000 ppm olaflur solution. Here the enamel specimens were either first incubated in-vitro with the olaflur solution and then exposed intraorally for 3 min or 2 h – or vice versa, the specimens were first exposed intraorally and afterwards in-vitro incubated with the olaflur solution. In order to avoid swallowing an excess amount of fluoride, the specimens were cleaned in distilled water for 5 s prior to intraoral exposure. Results: Under in vitro conditions, the 1,000 ppm olaflur solution or stannous fluoride solution did not produce a satisfactory, persistent fluoride layer on the pellicle-free tooth enamel. Using a 10,000 ppm concentration of fluoride in the olaflur solution a stable and homogeneous fluoride layer was generated on the tooth enamel. Only after being stored in distilled water for 24 hours the fluoride content was below the detection limit. As part of the blockface imaging it was shown that the generated fluoride cover layer consisted of calcium fluoride globules. Since the stannous fluoride solution could not generate a homogeneous fluoride layer in either a concentration of 1,000 ppm or 10,000 ppm, and because of the precipitation of the stannous fluoride, the stannous fluoride solution was excluded from the combined in-vitro and in-situ experiments. In the combined in-vitro and in-situ series of experiments, the scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis of the specimens, which were first incubated and then exposed intraorally, showed a homogenous cover layer of globules with a high fluoride content. However, if the intraoral exposure was carried out first and then the incubation with the olaflur solution, only the fluoridation of the specimens with the 3 min pellicle was successful. No fluoride could be detected on the 2 h-pellicle-covered tooth enamel. Conclusions: It was only possible to establish with the 10,000 ppm olaflur solution stable fluoride layers on the pellicle-free enamel as well as on the pellicle-covered tooth enamel. The 2 h pellicle layer, on the other hand, represented a barrier to the generation of a calcium fluoride layer. The study results show that the concentration, the frequency and the time of the fluoridation play an essential role for the fluoridation’s success. The study results show that regarding to the fluoridation success the olaflur solution was superior compared to the stannous fluoride solution.

Finite element models tend to overestimate the actual elastic response of structural timber connections. The paper shows how such overprediction relates to the modelling of the contact between fasteners and timber. The use of a control parameter called stiffness contact is proposed. After an experimental campaign, a method to determine it, based only on the geometry of a rectangular contact area, is proposed. The modeling adequacy is demonstrated by applying it to dowel embedment and moment resistant wood joint tests. The obtained results show good agreement with the experimental test series.

Within recent years, numerous fields of engineering, like mechanics, optics and electronics, have been influenced and revolutionised by the technique of microand nano-structuring. For example, special optical elements for beam shaping, surface structures for the reduction of friction or modern "lab on chip" devices have been produced. Within this thesis a universal system has been developed facilitating the production of such structured surfaces with dimensions down to 500 nm. This system is not only capable of structuring surfaces by means of lithographic processes; it further allows the inspection of surfaces by scanning their topography. To realise such a system, two different technologies have been evaluated: Scanning Near-field Optical Lithography (SNOL), a very sophisticated technique which uses a thin fibre tip to expose a photo resist-covered surface, and confocal scanning technology. Here, the confocal scanning is accomplished using an adapted optical component, the optical pickup unit (OPU), from a gaming console, which turned out to be the most suitable and cost-efficient solution for the realisation of this system. Several test series have been carried out during this work, to verify the performance of the confocal system, both to structure photo resist surfaces and to characterise unknown surfaces. This present work will show the ability of the developed system to produce structures down to the sub-micron range and to characterise unknown surfaces with sub- micron precision. Various patterns have been written into photo resistcoated substrates to structure their surface. Beginning with diffractive optical elements (DOE) for beam shaping, followed by Dammann gratings for twodimensional beam shaping and optical gratings for light guidance as well as producing technical surfaces imitating the properties of sharkskin or simple micromechanical structures, the developed confocal system has shown itself to be flexible and widely-applicable. IV During the development of the confocal system, a strong need for a beam profiling system analysing the light beam diverging from the OPU, was recognised. Due to the fact that no commercially available system was capable of characterising beam sizes within the range of the diffraction limit, a novel method for beam profiling was invented. This method makes use of the fibre tips already applied within the SNOL system, producing tomographical scans of the beam spot.

The flow around three-dimensional aircraft wings, including delta-wings is very complicated. Much experimental and numerical work has been performed to discover its complexity. To date, all numerical calculations on delta wings have been carried out for either fully laminar or fully turbulent boundary layers. The transition status of the boundary layer is considered unknown despite several efforts to identify transition from laminar to turbulent flow. One such study, called the International Vortex Flow Experiment – 2 (VFE-2), has been carried out by an international group and mainly focuses on the boundary layers on delta wings. The data from the VFE-2 experimentals potentially provide the location of transition on the upper and lower surfaces of the wing to guide associated numerical studies. The effects of Reynolds number, Mach number, angle of attack and the leading edge bluntness are also investigated. Almost all delta wing studies to date have involved tests on wings with sharp leading edges and these have led to the conclusion that the flows are relatively independent of Reynolds number. In fact, most real wings have finite leading edge radii. Hence, the flow separation is no longer fixed at the leading edge, thus making the flow dependent on Reynolds number. This particular aspect has been studied extensively by the VFE-2 team. As part of the VFE-2 project, Glasgow University constructed a delta wing with four different sets of leading edges. Small-, medium- and large-radius edges and a pair of sharp leading edges were constructed in order to compare results from four delta wing configurations. In the current study experiments were carried out on these wings in the 2.65 metre by 2.04 metre, closed circuit, Argyll Wind tunnel of Glasgow University. The models were mounted on a specially designed sting support structure that allowed them to be pitched around a constant centre of rotation throughout the experiments. Tests were conducted at speeds of 20.63 m/s and 41.23 m/s representing Reynolds numbers of 1 x 106 & 2 x 106 respectively, based on the mean aerodynamic chords of the wings. The tests were conducted in three phases. In the first phase, steady and unsteady forces and moments on all wings were measured at an angle of attack that varied from α =100 to 250. The forces and moments were captured at two sampling rates; i.e., 100 Hz and 8000 Hz. The second test series captured flow visualization data on the four wings. In these experiments, a mixture of Ondina oil and paraffin was combined with Dayglo powder and applied to the surfaces of the delta wings. The images of the flow topology on the wings were recorded. The final series of experiments involved Particle Image Velocimetry measurements. A stereo-PIV arrangement was applied in this experiment and two CCD-Cameras were positioned outside the test section for image capture. The current study has identified interesting features of the interrelationship between the conventional leading edge primary vortex and the occurrence and development of the inner vortex on the round-edged delta wings. The inner vortex was first identified and verified by the VFE-2 team. The effects of Reynolds number, angle of attack and leading-edge radii on both vortices are discussed in detail. The steady balance data have shown that the normal force coefficients are sensitive to leading edge bluntness at moderate angles of attack but are less so at high angles of attack. In relation to this, the flow visualization images have also shown that the primary vortex origin is located further aft on the wing at higher leading edge bluntness. This impacts on the strength of the inner vortex which remains a significant flow feature until the primary vortex approaches the apex. The lateral extent of the inner vortex is very dependent on the primary vortex at the leading edge; i.e. the weakening of the primary vortex has positive effects on the inner vortex. Particle Image Velocimetry shows that the increase in leading edge bluntness significantly decreases the swirl magnitude of the primary vortex. The results obtained from the current investigation provide considerable insight into the effects of Reynolds number, angle of attack and bluntness on the flow structures experienced by delta wings, with rounded leading edges. This work will, therefore, inform and guide future investigations of delta wing flows and has the potential to impact on future wing design.

Wildland fire is a natural part of the earth’s phenomenological pattern and like most natural phenomena has presented a challenge to human activity and engineering science. Wildfire presents Fire Safety Engineering with the task of developing fundamental research and designing analysis tools to address fire on a scale where interactions with atmospheric and terrestrial conditions dominate fire behavior. The research work presented in this thesis addresses a fundamental research issue involving transport processes in porous wildland fuel beds. This research project had the specific goal of developing an understanding of how transport processes affected the combustion of wildland fuels that were in the form of a porous bed. No detailed study could be found in the literature that specifically addressed how the fuel structure affected the combustion process in these types of fuels. To this end, a series of experiments were designed and carried out that approached the understanding of this problem using commonly available fire testing equipment, specifically the cone calorimeter and the FM Global Fire Propagation Apparatus. The goal of this research study and the basis for the novel and relevant contribution to the field of engineering was to conduct an experimental test series, analyze the data and examine the scalability of the results, to determine the effect of transport processes on the Heat Release Rate (HRR) of porous wildland fuels. The project concluded that flow dominates HRR in fires involving the wildland fuels tested. A dimensionless analysis of the fuel sample baskets showed consistency with well established mass transfer, fluid flow and chemical kinetic relationships. The dimensionless analysis also indicates that the experimental results should be scalable to similar configurations in larger fuel beds. One conclusion of this study was that wildland fire modeling efforts should invest in understanding flow conditions in fuel beds because this behavior dominates over the chemical kinetics of combustion for predicting HRR which is an important parameter in fire modeling.

In 2001, the Australian Standards for Concrete Structures AS 3600 incorporated 500 MPa grade reinforcing steels, which represented a 20 percent increase in strength over the 400 MPa grade steel of the previous version. The latest version of AS 3600 - 2018 allows for high strength steel up to 600 MPa for longitudinal reinforcement and 800 MPa for tie reinforcement in columns. Such improvement in the performance of materials can lead to more efficient, smaller sections with lower carbon footprints and lower costs. This thesis reports the results of a test series on high-strength concrete columns with nominal compressive strength of 100 MPa; reinforced with 520, 610, and 670 MPa grade steel, and confined with 810 MPa steel ties. Twenty-three columns were tested under different geometries, reinforcement arrangements and load eccentricities. The results of the tests conducted in this research, together with a further 10 specimens of an earlier study, are compared with the design models of AS 3600 – 2018 in terms of axial strength and ductility; the models are shown to give a reasonable lower bound to the test data. The effect of influencing parameters on the strength and ductility was investigated, namely section shape either square or rectangular, axial load eccentricities, tie arrangements, end conditions, ratio of and yield strength of longitudinal reinforcement. In this thesis the finite element model in ATENA was calibrated to study the behaviour of high-strengthconcrete column reinforced and confined with high strength steel reinforcement. The model was validated with the experimental results of this study, and others from literature. The fracture-plastic model introduced by Cervenka and Papanikolaou was used for the concrete material. To capture the effect of cover spalling the compressive strength of cover concrete was set to be decreased to zero once the cracks were formed at the interface of the cover and core. The comparison showed that the FEA results show good agreement with the test results. A parametric study was also conducted, and demonstrates the potential for the use of high strength steels in column elements of high-rise buildings.

This research study investigates the contribution of excessive deflection of horizontal members to the vertical shortening of mid-rise light timber framed buildings, due to compression perpendicular to the grain. Various timber species and different reinforcement methods were tested to identify the most appropriate solution(s) for the mid-rise light timber­framed building. A solution is to apply extra plates and screws or nails, which were spaced in the connections, to decrease compression and accordingly increase the strength of the elements under compression. To develop an appropriate reinforcement method( s) to be implemented by the industry, extensive experimental and numerical analyses were performed in this research project. The second phase of this research is related to the investigation of the structural performance of full-scale lightweight timber-framed walls for mid-rise construction, where different applicable solutions for reinforcing light timber-framed walls were studied, and the compression perpendicular to the grain was considered. The most appropriate solutions obtained from the first phase of the study were employed in the second phase to enhance the compression perpendicular to the grain of the timber-framed walls and validate the outcomes. To verify the full-scale lightweight timber-framed walls' experimental results a couple of numerical analyses were carried out. Following the above mentioned studies, the modelling outcomes were compared with results from the experimental tests and were seen to connect well. The growth of stiffness due to the reinforcement(s) was accurately identified by the developed numerical model(s). In addition to the comparison of modelling and experimental test outcomes, the test series on connections have shown that common nail(s) can be replaced by a self-tapping screw(s). This thesis demonstrates the feasibility of the increase of the connections' strength under compression perpendicular to the grain with high strength self-tapping screws and applying some different timber species as horizontal elements. Further research is recommended into the investigation of the combination of high­density timber species with very high strength self-tapping screws in connections which can give promising performance levels under compression perpendicular to the grain.

The continuing evolution of high voltage circuit breaker technology has directed current research and development throughout the switchgear industry towards the next generation of interrupter devices, which offer even more advantages than currently applied technologies. A novel rotating arc SF₆ filled interrupter designed to interrupt fault currents at the 145kV level is investigated for such an application. Initial low voltage, low current tests examine the magnetic field and phase angle in the arcing volume, identifying a number of solutions which can be utilised to reduce eddy current circulation in the structural components of the rotating arc coil assembly and consequently optimise the spatial distribution in the arcing volume. The structural capability of the interrupter components has been investigated experimentally under short circuit fault conditions. Short time current tests in excess of 70kA have demonstrated that the coil components can fail when the coil is subjected to extremely high thermal and mechanical stresses due to the short circuit fault current. High-speed photography has been utilised to investigate if the rotating arc interrupter is operating as was initially envisaged and identified fundamental properties of the arc during the interruption process as well as provide information regarding the condition of the arcing volume following arc extinction to assess the dielectric integrity of the interrupter. Although measurements identified correct operation of the rotating arc interrupter, a number of problems with the design have been identified during the test series. The initial half cycle of arcing in the core of the arc runner electrode has been investigated experimentally utilising high speed footage and optical fibres fitted directly to the arc runner electrode revealing important characteristics with respect to the rotating arc interrupters performance. Optimisation of the arc transfer time from the fixed contact to the arc runner electrode has been identified to be one of the fundamental parameters in successful operation. The arc's velocity has been measured experimentally as a function of applied peak current and interrupter gas pressure identifying significant variation in the performance during low and high current operation due to deviation in Lorentz force. Dielectric probe and optical pressure measurements have provided direct evidence of the condition of SF¢ gas in the arcing volume and identified problems associated with the capability of the interrupter to remove hot gas and ionised particles. Finally high current, high voltage tests have been performed to ascertain the limits of the interrupter design at 145kV level by simulating service conditions. The interaction between the arcing time and rate of rise of recovery voltage has been investigated enabling the short circuit performance of the interrupter to be segregated into three regions. Parameters improving the thermal and dielectric capability of the interrupter and consequently the short circuit performance have been identified, and in order to overcome the associated dielectric problems, several flush pipe configurations are tested and the optimum configuration ascertained. Successful performance of the rotating arc interrupter has been achieved at the 145kV, 31.5kA level.

Advanced material models for the intra- and inter-laminar damage and failure prediction of biaxial carbon/epoxy Non Crimp Fabric (NCF) composites are presented, which enable application to large scale practical composite structures for the automotive industry. The model established for intra-laminar failure combines the elasto-plastic continuum damage constitutive model first proposed by Ladevèze, with the matrix failure model of Puck, and improves the shear damage representation by using an exponential damage evolution law. An extensive test program has been conducted using biaxial NCF composites with differing degrees of fabric pre-shear. The presheared biaxial NCF are considered to take into account potential changes of the damage and failure properties occurring due to the draping process in real structures. The database established is used to identify parameters for the proposed Ladevèze-Puck matrix damage and failure model, allowing prediction of the main matrix failure modes of unsheared and presheared biaxial NCF composites. Furthermore, the failure prediction within zones of stress concentrations is addressed utilising flat NCF laminates with different holes and lay-ups. For numerical elastic failure prediction of these tests a simple fibre criterion is presented which is related to a characteristic element size. The Puck failure model is adopted to represent the inter-laminar (delamination) crack initiation strength of the investigated NCF. This stress based model for delamination crack initiation operates in conjunction with existing methods for the simulation of delamination crack propagation, which are related to the critical strain energy release rate. All material models that have been combined and further developed during the course of this work have been implemented in a research version of a commercial crashworthiness Finite Element code. The intra-laminar failure model is validated against a test series of transversely loaded circular- composite discs having differing degrees of fabric pre-shear. The final validation example for intra-laminar failure has considered a complex composite door structure subjected to lateral punch intrusion. The enhanced delamination failure model is validated using a composite beam structure, exhibiting delamination failure under local transverse tension loading. For all validation tests a good agreement between simulations and experiments has been demonstrated. It is believed by the author that the new contributions presented in this thesis significantly raise the level of numerical prediction of deformation, damage, and failure for Continuous Carbon Fibre Reinforced Composites. Special emphasis is placed on the fact that all material model parameters have been obtained from simple specimen tests, and have been used without adjustment for the simulation of subsequent Validation tests utilising Composite structures of high complexity. This continuous approach is in contrast to the majority of similar investigations found in the literature, in which the adjustment of material model parameters appeared to be necessary in order to achieve a good agreement between simulations and experiments of complex structures.