Full-scale testing and numerical modeling of a multistory masonry structure subjected to internal blast loading

As military and diplomatic representatives of the United States are deployed throughout the world, they must frequently make use of local, existing facilities; it is inevitable that some of these will be load bearing unreinforced masonry (URM) structures. Although generally suitable for conventional design loads, load bearing URM presents a unique hazard, with respect to collapse, when exposed to blast loading. There is therefore a need to study the blast resistance of load bearing URM construction in order to better protect US citizens assigned to dangerous locales. To address this, the Department of Civil and Environmental Engineering at the University of North Carolina at Charlotte conducted three blast tests inside a decommissioned, coal-fired, power plant prior to its scheduled demolition. The power plant's walls were constructed of URM and provided an excellent opportunity to study the response of URM walls in-situ. Post-test analytical studies investigated the ability of existing blast load prediction methodologies to model the case of a cylindrical charge with a low height of burst. It was found that even for the relatively simple blast chamber geometries of these tests, simplified analysis methods predicted blast impulses with an average net error of 22%. The study suggested that existing simplified analysis methods would benefit from additional development to better predict blast loads from cylinders detonated near the ground's surface. A hydrocode, CTH, was also used to perform two and three-dimensional simulations of the blast events. In order to use the hydrocode, Jones Wilkins Lee (JWL) equation of state (EOS) coefficients were developed for the experiment's Unimax dynamite charges; a novel energy-scaling technique was developed which permits the derivation of new JWL coefficients from an existing coefficient set. The hydrocode simulations were able to simulate blast impulses with an average absolute error of 34.5%. Moreover, the hydrocode simulations provided highly resolved spatio-temporal blast loading data for subsequent structural simulations. Equivalent single-degree-of-freedom (ESDOF) structural response models were then used to predict the out-of-plane deflections of blast chamber walls. A new resistance function was developed which permits a URM wall to crack at any height; numerical methodologies were also developed to compute transformation factors required for use in the ESDOF method. When combined with the CTH derived blast loading predictions, the ESDOF models were able to predict out-of-plane deflections with reasonable accuracy. Further investigations were performed using finite element models constructed in LS-DYNA; the models used elastic elements combined with contacts possessing a tension/shear cutoff and the ability to simulate fracture energy release. Using the CTH predicted blast loads and carefully selected constitutive parameters, the LS-DYNA models were able to both qualitatively and quantitatively predict blast chamber wall deflections and damage patterns. Moreover, the finite element models suggested several modes of response which cannot be modeled by current ESDOF methods; the effect of these response modes on the accuracy of ESDOF predictions warrants further st

FUN3D and CFL3D Computations for the First High Lift Prediction Workshop

Two Reynolds-averaged Navier-Stokes codes were used to compute flow over the NASA Trapezoidal Wing at high lift conditions for the 1st AIAA CFD High Lift Prediction Workshop, held in Chicago in June 2010. The unstructured-grid code FUN3D and the structured-grid code CFL3D were applied to several different grid systems. The effects of code, grid system, turbulence model, viscous term treatment, and brackets were studied. The SST model on this configuration predicted lower lift than the Spalart-Allmaras model at high angles of attack; the Spalart-Allmaras model agreed better with experiment. Neglecting viscous cross-derivative terms caused poorer prediction in the wing tip vortex region. Output-based grid adaptation was applied to the unstructured-grid solutions. The adapted grids better resolved wake structures and reduced flap flow separation, which was also observed in uniform grid refinement studies. Limitations of the adaptation method as well as areas for future improvement were identified

Dialogue and Roles in a Strategy Workshop: Discovering Patterns through Discourse Analysis

Strategy workshops are frequently used by Executive management teams to discuss and formulate strategy but are under-researched and under-reported in the academic literature. This study uses Discourse Analysis to discover participant roles and dialogic patterns in an Executive management team’s strategy workshop, together with their effect on the workshop’s operation and outcome. The study shows how the workshop participants adopt different roles through their language and content. It then identifies a dialogic pattern in the workshop discourse, with the emphasis on achieving shared understanding rather than winning the debate. The workshop facilitator’s role is shown to bring discussion as a counter balance to the group’s dialogue, focusing the evolving dialogic discourse on actionable outcomes. The study goes on to show how these two discourse features combine to enable a comprehensive exploration of a strategic topic in a limited time frame and to build a consensus based strategy to be followed. The group’s use of metaphor and the construction of organisation and individual identities were also examined. They were shown to have limited impact on the developing roles, dialogic discourse or workshop’s outcome. Overall, the analysis shows how the combination of roles and dialogue surface implicit meaning from the group’s discourse and enable a significant shift in the groups thinking, charting the way for a fresh perspective on an acknowledged long-standing, strategic problem

Working Inside the Black Box: Refinement of Pre-Existing Skills

This thesis aimed to address and inform the gap in current sport psychology/coaching research, knowledge and practice related to the implementation of technical refinement in already learnt, well-established and self-paced skills. This was achieved through a series of studies conducted within golf. Accordingly, Chapter 2 revealed technical refinement as neither systematic nor consistent within and between European Tour players and coaches and high-level amateurs. Building on this need, the systematic Five-A Model was derived from the literature (Chapter 3), targeting outcomes of permanency and pressure resistance. Following, motor control (Chapter 4) and kinematic (Chapter 5) measures, technological methods from which these data could be obtained (Chapter 6) and appropriate training environments and task characteristics (Chapter 7) were determined, aimed at enabling informative tracking of progress through the Five-A Model in applied golf coaching environments. Having developed these ranges of measures and methods, Chapter 8 presented three longitudinal case studies aimed at implementing and tracking progress through stages of the Five-A Model. Results revealed outcomes with different levels of success in facilitating technical refinement, based primarily on psycho-behavioural limitations that were also found in Chapter 2. Therefore, as a final check on measures proposed, Chapter 9 confirmed previous suggestions by tracking six performers making short-term technical refinements within a single training session. Finally, Chapter 10 summarised the findings and implications of this thesis. Particular emphasis was directed towards the impact of psycho-behavioural skills in determining the success when attempting refinements, the further development of informative measures to track progress and inform coaches decision making and the wider implications of this research within clinical and rehabilitation settings

MAC-REALM: A video content feature extraction and modelling framework

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A consequence of the ‘data deluge’ is the exponential increase in digital video footage, while the ability to find relevant video clips diminishes. Traditional text based search engines are no longer optimal for searching, as they cannot provide a granular search of the content inside video footage. To be able to search the video in a content based manner, the content features of the video need to be extracted and modelled into a content model, which can then act as a searchable proxy for the video content. This thesis focuses on the extraction of syntactic and semantic content features and content modelling, using machine driven processes, with either little or no user interaction. Our abstract framework design extracts syntactic and semantic content features and compiles them into an integrated content model. The framework integrates a four plane strategy that consists of a pre-processing plane that removes redundant data and filters the media to improve the feature extraction properties of the media; a syntactic feature extraction plane that extracts low level syntactic feature and mid-level syntactic features that have semantic attributes; a semantic relationship analysis and linkage plane, where the spatial and temporal relationships of all the content features are defined, and finally a content modelling stage where the syntactic and semantic content features are integrated into a content model. Each of the four planes can be split into three layers namely, the content layer, where the content to be processed is stored; the application layer, where the content is converted into content descriptions, and the MPEG-7 layer, where content descriptions are serialised. Using MPEG-7 standards to produce the content model will provide wide-ranging interoperability, while facilitating granular multi-content type searches. The framework is aiming to ‘bridge’ the semantic gap, by integrating the syntactic and semantic content features from extraction through to modelling. The design of the framework has been implemented into a prototype called MAC-REALM, which has been tested and evaluated for its effectiveness to extract and model content features. Conclusions are drawn about the research output as a whole and whether they have met the objectives. Finally, future work is presented on how concept detection and crowd sourcing can be used with MAC-REALM

Application of local mechanical tensioning and laser processing to improve structural integrity of multi-pass welds

Multi-pass fusion welding by a filler wire (welding electrode) is normally carried out to join thick steel sections used in most engineering applications. Welded joints in an installation, is the area of critical importance, since they are likely to contain a higher density of defects than the parent metal and their physical properties can differ significantly from the parent metal. Fusion arc welding process relies on intense local heating at a joint where a certain amount of the parent metal is melted and fused with additional metal from the filler wire. The intense local heating causes severe transient thermal gradients in the welded component and the resulting uneven cooling that follows produces a variably distributed residual stress field. In multi-pass welds, multiple thermal cycles resulted in a variably distribution of residual stress field across the weld and through the thickness. These complex thermal stresses generated in welds are undesirable but inevitable during fusion welding. Presence of such tensile residual stresses can be detrimental to the service integrity of a welded structure. In addition to a complex distribution of residual stress state, multi-pass welds also forms dendritic grain structure, which are repeatedly heated, resulting in segregation of alloying elements. Dendritic grain structure is weaker and segregation of alloying elements would result in formation of corrosion microcells as well as reduction in overall corrosion prevention due to depletion of alloying elements

An evaluation of the production of magnesium base alloy castings by the expendable pattern casting process

Magnesium alloy is a light weight metallic material which offers good engineering properties and environmental advantages. Most cast components in this material are produced by the traditional casting processes, predominantly the die-casting process. The Expendable Pattern Casting Process (EPC process) is a relatively new casting process which provides many design, processing and environmental benefits. However, the process differs significantly from the conventional empty mould sand casting process and there is the need for research to develop an understanding of the process parameters. The research was established to provide a preliminary evaluation of the production of magnesium base alloy castings by the expendable pattern casting process under gravity and counter gravity pouring. The major process parameters investigated were filling pressure, pouring temperature and pattern bead density. The problems experienced in applying this process for this material in the experimental research were defined. Microstructures and mechanical properties of the cast specimens were investigated and reported. The results showed that the quality of test bar specimens produced by the EPC process under counter gravity pouring with optimised process parameters was compatible with the quality of castings produced by the conventional sand casting process. In addition to the experimental research a review was conducted of the modelling of different methods of pouring. The pouring methods considered were bottom gating in gravity pouring, counter gravity pouring in an empty cavity mould process, and expendable pattern casting processes under both gravity and counter gravity pouring. A quasi one dimensional fluid mechanics analysis was conducted to explain the effect of pattern degradation on the delay in mould filling