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An advanced finite-element package, tailored to the static and dynamic analysis of radial impellers has been produced. Two families of new elements, one for thin and thick plates and the other for thin and thick shells, have been derived and proved to perform very well within a wide range of structural thicknesses. Static and dynamic economical solvers, two- and three-dimensional mesh generation and plotting, sectorial symmetric analysis, steady state response, transient response, and other programs are part of the large number of facilities available in the package. The finite-element package has been validated by solving a large number of simple case studies and comparing the package results with those obtained from analytical solutions. Two different radial impeller, experimental validation tests have been carried out, the first being the dynamic analysis of a radial impeller using the time averaged holographic technique, and the second the measurement of the steady-state stresses by means of a strain-gauge/slip ring assembly for a rotating impeller. The experimental results have been shown to be in good agreement with those obtained from the package.

No description available.

The behaviour of connections in fire has become of particular interest to the structural engineering community following the possible link of connection failure to the collapse of the World Trade Centre building 7 and the failures and huge distortion of some connections after the Cardington full scale tests. In order to widen the understanding of the complex behaviour of connections in fire this thesis discusses a number of specific issues relating to connections in fire and their influence on structural response. The first part of this work presents a finite element model for predicting connection temperature profiles. A parametric study is then carried out to investigate which factors have the greatest influence on temperature prediction. This method is compared to the currently available methods for connection temperature prediction presented in the Eurocodes: using a percentage of the beam mid-span lower flange temperature to estimate the temperature across the connection and a lumped capacitance method to calculate average joint temperature based on the mass of material and surface area. In each case, along with the predicted temperatures, the influence on connection material strength is also presented. The three methods have varying levels of accuracy. The finite element model provides detailed and accurate results due to the thorough consideration given to the input parameters. The percentages method gives reasonable estimates in the heating phase but is less accurate in cooling and the lumped capacitance method is only suitable for crude estimations. The remainder of the thesis is concerned with how a number of phenomena affect the overall structural behaviour of buildings: the inclusion of detailed connection models within larger, less complex, finite element models; the effects of connection rotational capacity and the composite beam-slab shear connection. A finite element model for isolated joints is presented in detail for a number of heating regimes and connection types. The influence of the bolt shear and tensile properties is considered in detail and the need for further testing on bolts at high temperatures is discussed. The model has the capacity to predict a number of failure modes and also shows a good comparison between experimental and theoretical deflected shapes. This connection model is then inserted into a large model. It is shown that whilst the inclusion of the shell connection has a small influence on the residual deflections of a structure after cooling when compare to a model where connections are simple and fixed, the difference between heating and not heating the connection does effect structural deflections. Following on from the previous full scale model, simple connections are then exclusively included where the connection rotational capacity is varied. Results show that there is not a large effect on the structural deflections or beam axial and shear forces when rotational behaviour is changed. However column bending moments are hugely increased during heating both in the fire compartment and away from it and fixed connections result in larger bending moment that pinned ones. Finally, the shear interaction between the slab and beams is investigated. The detailed development of both an ambient temperature and then an elevated temperature model of a beam-slab system including explicit shear studs are presented. A study is then carried out looking at the effects on deflections and beam forces when the strength and ductility of the studs are altered. It is found that more ductile studs with a high shear capacity are beneficial for reducing forces in beams and limiting their deflections. Finally the shear studs are included in the larger model used in previous chapters where results are similar to those seen in the beam-slab model, but are less pronounced.

Wind energy has emerged as a promising and renewable solution to reduce reliance on fossil fuels in remote off-grid locations. Conventional wind turbine towers are made from concrete or steel, which present several significant drawbacks in certain applications. The use of lightweight and corrosion-resistant fibre reinforced polymer (FRP) tubes as permanent structural formwork can mitigate these challenges. Existing literature has highlighted the performance of concrete-filled FRP tubes (CFFTs) through experiments and successful applications in the field. However, only a few cantilever CFFTs have been tested, and their sizes were much smaller than required for wind turbine towers. In consequence, this thesis focuses on relatively large cantilever CFFTs at a scale representative of small wind turbine towers. The finite element (FE) method was adopted to simulate the behaviour of CFFT towers using the commercial software ABAQUS. The first part of this thesis presents the development and validation of CFFT FE models under bending and axial loading conditions, as well as hollow FRP tubes under bending. The models were compared to experimental results reported by Fam (2000) to ensure the selection of appropriate material properties. Good agreements were observed, and the accuracy of the FE modelling approach was proved. Subsequently, a parametric study was conducted to explore the feasibility of CFFTs for wind turbine towers. The analyses of cantilever towers with different geometric properties and reinforcement configurations under concentrated lateral load were performed first. Then, a cantilever CFFT tower under different loading configurations was tested. It is noted that towers subjected to concentrated load had the lowest load capacity and stiffness. Conclusions were made that with or without axial load, lateral load eccentricity does not affect the behaviour of cantilever CFFTs significantly. Meanwhile, the increase in height-to-diameter ratio decreases the load capacity and stiffness of cantilever CFFTs. Finally, the CFFT tower results were compared with concrete and steel tubular models with similar geometry. The results suggest that CFFTs have better overall performance than the other two types of towers. They are also superior with respect to flexibility in installation and their durability.

The mechanism of soil-reinforcement interaction for a reinforced embankment on soft clay has been explored by conducting a parametric study using a coupled non-linear elastoplastic finite element program. One of the major issues in the design of a reinforced embankment on soft clay is the magnitude of tension that can be mobilized in the geosynthetic reinforcement. Previous research using geotechnical centrifuge modelling and present research using finite element modelling has confirmed that the tension mobilized in the reinforcement is only of the order of active lateral thrust in the embankment. The parametric study has revealed that the soil-reinforcement interaction mechanism depends on the ratio of embankment height to the depth of the clay layer. The embankment behaves similar to a rigid footing in case of deep clay deposit. In this case, the failure mechanism is similar to a slip circle and there is very little contribution from the clay-reinforcement interface towards the mobilization of reinforcement tension. However, if the depth of clay deposit is small, the soil-reinforcement interaction mode is similar to direct shear failure and slip surface is located close to the clay-reinforcement interface. In this case, the contribution of clay-reinforcement interface towards the tension mobilized in the reinforcement is higher and therefore, the contribution of the reinforcement towards overall stability of the embankment is greater. Based on the results of the parametric study a novel serviceability criterion is proposed that aims to limit the lateral deformation of the clay foundation at the toe of the embankment by limiting the allowable mobilized tension in the reinforcement. A simple procedure for the evaluation of the efficiency of soil-reinforcement interface for reinforced embankments on soft clays is also proposed. The validity of the proposed serviceability criterion and the design charts was successfully tested using two field case studies. Sackville test embankment constructed to failure in 1989 and a levee test section that remained serviceable after construction in 1987 at Plaquemine, Louisiana were able to confirm the validity of the serviceability criterion proposed in the present study.

The mechanism of soil-reinforcement interaction for a reinforced embankment on soft clay has been explored by conducting a parametric study using a coupled non-linear elastoplastic finite element program. One of the major issues in the design of a reinforced embankment on soft clay is the magnitude of tension that can be mobilized in the geosynthetic reinforcement. Previous research using geotechnical centrifuge modelling and present research using finite element modelling has confirmed that the tension mobilized in the reinforcement is only of the order of active lateral thrust in the embankment. The parametric study has revealed that the soil-reinforcement interaction mechanism depends on the ratio of embankment height to the depth of the clay layer. The embankment behaves similar to a rigid footing in case of deep clay deposit. In this case, the failure mechanism is similar to a slip circle and there is very little contribution from the clay-reinforcement interface towards the mobilization of reinforcement tension. However, if the depth of clay deposit is small, the soil-reinforcement interaction mode is similar to direct shear failure and slip surface is located close to the clay-reinforcement interface. In this case, the contribution of clay-reinforcement interface towards the tension mobilized in the reinforcement is higher and therefore, the contribution of the reinforcement towards overall stability of the embankment is greater. Based on the results of the parametric study a novel serviceability criterion is proposed that aims to limit the lateral deformation of the clay foundation at the toe of the embankment by limiting the allowable mobilized tension in the reinforcement. A simple procedure for the evaluation of the efficiency of soil-reinforcement interface for reinforced embankments on soft clays is also proposed. The validity of the proposed serviceability criterion and the design charts was successfully tested using two field case studies. Sackville test embankment constructed to failure in 1989 and a levee test section that remained serviceable after construction in 1987 at Plaquemine, Louisiana were able to confirm the validity of the serviceability criterion proposed in the present study.

An intramedullary nail is a trauma treatment device used for fracture fixation of long bones. These devices are subject to failure, including lag screw cut-out and failure at the lag screw insertion hole from high stress concentrations in that region. Clinical developments for such devices are frequently based on a trial and error method, which often results in failure before improvement. However, the finite element method can be used for the development of trauma treatment devices, and their interaction with bone, by providing a large data set at a relatively low cost. Also, parameters can be changed to assess the relative benefits of one device to another. A novel finite element model has been developed that can be used for the analysis of intramedullary nails inserted into long bones. A commercially available finite element package, ANSYS, has been used to implement the modelling strategy. The finite element modelling technique has been applied to fractures of the proximal femur, but the model is generic, and can be developed to deal with any form of intramedullary device where contact between the bone and implant is important. The finite element strategy can be used in pre-clinical trials to test a new device, or for the design optimisation of existing devices. The finite element model consists of the device surrounded by a thin layer of bone, which forms a 'base' model component that is re-usable. This 'base' component can be mathematically connected to any long bone model, forming an integrated implant and bone construct. The construct can be used to assess which device is best suited to a particular fracture, for example. Contact elements have been used to allow stresses to develop as contact is achieved within the implant and bone construct. Pre-assignment of contact points is not required. Verification of the finite element model is achieved by comparison to available data from experiments carried out on constructs of bone and device that use intramedullary femoral nails. In this thesis the finite element model has been applied to two areas of proximal femoral nailing. The finite element model is used to analyse the distal end of a Gamma nail, and shows that analyses that do not consider contact may not lead to accurate predictions of stresses. The model has been developed for using configurations with one and two distal locking screws. The most distal locking screw is more critical under axial loading, and the more proximal screw is more important for bending loads. The use of 'softer' screws distributes the load more evenly between them. The finite element model has been used to investigate the mechanical environment of a fracture callus for a femoral neck fracture, and a subtrochanteric fracture. The use of one and two lag screws, fracture gap size and material properties of the nail have been investigated for a stiffening callus. Results show that the use of two lag screws for a neck fracture provides a more rigid support at the early stages of fracture healing, and minimises stress-shielding once the callus has healed. For subtrochanteric fractures there is a critical point at which the fracture callus is able to carry any load. A Titanium nail significantly reduces the peak stress at the lag screw insertion hole, and titanium lag screws share the load more evenly between them. Each two-lag-screw configuration used transfers a similar load into the fracture callus. A configuration using a larger lag screw above a smaller has a significantly higher stress at the upper lag screw insertion hole. Critically, the load shared between two lag screws changes as the fracture callus stiffens and an assessment should be made at different stages of fracture healing to optimise the use of a device.

A machining process is one of the most common techniques used to remove material in order to create a final product. Most studies on mechanisms of cutting are performed under the assumption that the studied material is isotropic, homogeneous and continuous. One important feature of material- its anisotropyis linked to its crystallographic nature, which is usually ignored in machining studies. A crystallographic orientation of a workpiece material exerts a great influence on the chip-formation mechanism. Thus, there is a need for developing fundamental understanding of material's behaviour and material removal processes. While the effect of crystallographic orientation on cutting-force variation is extensively reported in the literature, the development of the single crystal machining models is somewhat limited.

Concussions are injuries that can result in debilitating symptoms, suffered by people of all ages, with children being at elevated risk for injury. Falls account for over 20% of head injuries worldwide, and up to 50% of concussive injuries in children. Following a concussion, children typically take longer for symptoms to resolve compared to adults. It is unknown whether or not children are more, less, or equally susceptible to concussive injury based on the mechanical response, with researchers divided on the subject. There is currently a paucity of published data for concussive injuries in children, with few studies investigating impact biomechanics and strain response in the brain using FE models. Those that exist typically rely on scaled adult models that do not capture age-dependent geometric properties, material properties of tissues, and the developmental stage of the brain reflected by the patterns of grey and white matter within the brain. Newer child models are being developed, however at present they are focused on car crash investigations that do not offer an accurate reflection of sports-related impacts, and those that could be experienced from day-to-day activities since impact characteristics (e.g. magnitude, duration, surface compliance) differ largely between these types of events. Strain magnitudes differ between events causing concussion in adults (falls, collisions, punches, and projectiles), so it follows that the unique impact characteristics of car crash events do not typically coincide with those associated with sports impacts. Car crash events can result in much longer impact durations compared to sporting impacts (100 ms duration in car crashes vs. 5-30 ms in sports impacts). The purpose of this thesis was to assess how the mechanical response of the brain in young children near 6 years old differs from an adult brain in cases resulting in concussive injury for sports impacts. Study one created a novel FE model of a 6-year-old brain, using medical images to extract an accurate representation of the geometry and tissues inside the head of a 6-year-old child. The developmental stage of the younger brain was captured using a highly-refined mesh to accurately represent the folds of white matter within the cerebrum. With no intracranial data for child cadavers available, published data of adult cadavers was used to validate the brain motion from impacts. Comparisons were made to a scaled adult model to highlight how the different model constructions influence brain motion and resulting strains. The new model showed higher correlation to the cadaver data compared to the scaled model, and yielded “good biofidelity” measures when assessed using a modified version of the normalized integral square error method. For young children, the new model was proposed to be more appropriate for concussion investigations as it captures age-appropriate geometry, material properties, and developmental stage of the brain, reflected in the patterns and volumes of grey and white matter within the brain. Study two tested the model for sensitivity across three levels of surface compliance and impact velocity consistent with sport impact events, and compared strain responses to a scaled adult model. The 6-year-old model showed unique strain responses compared to the scaled adult model with peak strains being lower across most impact events. Strain patterns also differed between models, with less strain being transmitted into the white matter in the 6-year-old model. Low compliance impacts yielded highest differences in strains (~30%), moderate compliance impacts yielded more similar strains (~9% lower), with high compliance impacts showing a location dependent response with frontal impacts being 14% lower, and side impacts being 9% higher than the scaled model. The sensitivity study characterized the model responses, allowing for better comparisons between the two different model constructions. Study three then compared the strain responses of reconstructed real-world concussive events for both children and adults. Forty cases of concussion from falls in children and adults (20 children aged 5-7, 20 adults) were reconstructed using physical models, with the measured impact kinematics used to load the FE models. Concussive cases of children showed lower strains than adults, finding a velocity driven relationship since the child concussions occurred at lower impact velocities compared to the adults. Lower peak strains, as well as cumulative strains in the child cases suggest that children are vulnerable to concussion at lower strain compared to adults. Protective strategies for children should address this vulnerability, no longer relying on product scaling to create head protection for youth.