Lateral pressures on non-yielding walls due to surface strip loads were investigated considering the non-linear stress-strain behaviour of the soil by finite element analyses. Data obtained from the finite element analyses were used to train neural networks in order to obtain a solution to assess the total lateral thrust and its point of application on a non-yielding wall due to a strip load. A 2-layered backpropogation type neural network was used. An artificial neural network solution was obtained, as a function of six parameters including the shear strength parameters of the soil ( cohesion and angle of friction ). The effects of each input parameter on the lateral thrust and point of application were summarized and the results were compared with the conventional linear elastic solution.

Many computers and devices such as smart phones, laptops and tablet devices are now equipped with multiple network interfaces, enabling them to use multiple paths to access content over the network. If the resources could be used concurrently, end user experience can be greatly improved. The recent studies in MPTCP suggest that improved reliability, load balancing and mobility are feasible. The thesis presents a new multipath delay based algorithm, MPPERT (Multipath Probabilistic Early response TCP), which provides high throughput and efficient load balancing. In all-PERT environment, MPPERT suffers no packet loss and maintains much smaller queue sizes compared to existing MPTCP, making it suitable for real time data transfer. MP-PERT is suitable for incremental deployment in a heterogeneous environment. It also presents a parametrized approach to tune the amount of traffic shift off the congested path. Multipath approach is benefited from having multiple connections between end hosts. However, it is desired to keep the connection set minimal as increasing number of paths may not always provide significant increase in the performance. Moreover, higher number of paths unnecessarily increase computational requirement. Ideally, we should suppress paths with low throughputs and avoid paths with shared bottlenecks. In case of MPTCP, there is no efficient way to detect a common bottleneck between subflows. MPTCP applies a constraint of best single-path TCP throughput, to ensure fair share at a common bottleneck link. The best path throughput constraint along with traffic shift, from more congested to less congested paths, provide better opportunity for the competing flows to achieve higher throughput. However, the disadvantage is that even if there are no shared links, the same constraint would decrease the overall achievable throughput of a multipath flow. PERT, being a delay based TCP protocol, has continuous information about the state of the queue. This information is valuable in enabling MPPERT to detect subflows sharing a common bottleneck and obtain a smaller set of disjoint subflows. This information can even be used to switch from coupled (a set of subflows having interdependent increase/decrease of congestion windows) to uncoupled (independent increase/decrease of congestion windows) subflows, yielding higher throughput when best single-path TCP constraint is relaxed. The ns-2 simulations support MPPERT as a highly competitive multipath approach, suitable for real time data transfer, which is capable of offering higher throughput and improved reliability.

This thesis investigates the effects of elastic restraint at the supports on the behaviour of shallow concrete arches, and the time-dependent effects of shrinkage and creep of concrete on the nonlinear behaviour of shallow arches. The nonlinear behaviour of shallow circular arches with elastic rotational restraints at each support and subjected to a uniformly distributed radial load is firstly investigated. A virtual work formulation is used to establish both the nonlinear equilibrium equations and the buckling equilibrium equation for shallow arches. The analytical results show that the effects of the stiffness of the rotational restraints on the prebuckling and buckling response are significant. An analytical model is developed for the in-plane elastic stability analysis of shallow parabolic arches with horizontal spring supports subjected to a uniformly distributed vertical load. A parametric study is undertaken using the proposed analytical model. It is found that the effects of the stiffness of the horizontal springs on the prebuckling response, buckling load and buckling behaviour of arches are significant. An analytical model is developed to simulate the time-dependent behaviour of shallow concrete parabolic arches with horizontal spring supports subjected to a sustained loading, and in particular to investigate creep buckling. The time-dependent buckling load and the critical time (or age) of the arches are calculated by using an iterative process based on the proposed model. A systematic parametric study is undertaken, and the results show that the various parameters have a profound effect on the time-dependent buckling load and the prebuckling life of arches. Both short-term and long-term experimental investigations of shallow parabolic tied concrete arches are described and used to validate the analytical models. For the short-term tests, three concrete arches were subjected to a uniformly distributed vertical load and were loaded to failure. For the long-term tests, seven concrete arches were subjected to sustained service loads. The instantaneous and time-dependent deflections were recorded throughout the period of loading, together with the distribution of the horizontal thrust at the supports. Comparisons between the experimental results and the analytical predictions using the analytical models are made to verify the accuracy of the theoretical models.

Cognitive load theory uses the immense size of human long-term memory and the significantly limited capacity of working memory to design instructional methods. Five basic principles: information store principle, borrowing and reorganizing principle, randomness as genesis principle, narrow limits of change principle, and environmental linking and organizing principle explain the cognitive basics of this theory. The theory differentiates between three major types of cognitive load: extraneous load that is caused by instructional strategies, intrinsic cognitive load that results from a high element interactivity material and germane load that is concerned with activities leading to learning. Instructional methods designed in accordance with cognitive load theory rely heavily on the borrowing and reorganizing principle, rather than on the randomness as genesis principle to reduce the imposed cognitive load. As learning fractions incorporates high element interactivity, a high intrinsic cognitive load is imposed. Therefore, learning fractions was studied in the experiments of this thesis. Knowledge held in long-term memory can be used to reduce working memory load via the environmental linking and organizing principle. It can be suggested that if fractions are presented using familiar objects, many of the interacting elements that constitute a fraction might be embedded in stored knowledge and so can be treated as a single element by working memory. Thus, familiar context can be used to reduce cognitive load and so facilitate learning. In a series of randomized, controlled experiments, evidence was found to argue for a contextual effect. The first three experiments of this thesis were designed to test the main hypothesis that presenting students with worked examples concerning fractions would enhance learning if a real-life context was used rather than a geometric context. This hypothesis was tested using both a visual and a word-based format and was supported by the results. The last two experiments were intended to test the context effect using either worked examples or problem solving. The results supported the validity of the previous hypothesis using both instructional methods. Overall, the thesis sheds some light on the advantages of using familiar objects when mastering complex concepts in mathematics.

The study of the response of tall buildings to wind has become more critical with the increase of super tall buildings in major cities around the world. Outrigger-braced tall building is considered as one of the most popular and efficient tall building design because they are easier to build, save on costs and provide massive lateral stiffness. Most importantly, outrigger-braced structures can strengthen a building without disturbing its aesthetic appearance and this is a significant advantage over other lateral load resisting systems. Therefore this thesis focuses on the optimum design of multi-outriggers in tall buildings, based on the standards set out in the Australian wind code AS/NZS 1170.2. / As taller buildings are built, more outriggers are required. Most of the research to date has included a limited number of outriggers in a building. Some tall buildings require more outriggers especially for those more than 500m building height. Therefore there is a need to develop a design that includes many outriggers (e.g. more than 5). In addition, wind-induced acceleration is not covered in most of the research on outrigger-braced buildings. The adoption of outrigger-braced systems in tall buildings is very common and therefore a discussion of wind-induced acceleration will be included in this thesis. / Most of the current standards allow for the adoption of a triangular load distribution in estimating the wind response of a structure. However, there are only few publications on the utilization of a triangular load distribution to determine the optimum location of a limited number of outriggers. This issue will be addressed in this thesis and will be compared with a uniformly distributed wind load. Further to this, an investigation will be carried out on the factors affecting the efficiency of an outrigger-braced system in terms of the core base bending moment and the total drift reduction. / This thesis principally provides a preliminary guide to assess the performance of outrigger-braced system by estimating the restraining moments at the outrigger locations, core base bending moment, the total building deflection, along-wind and crosswind acceleration of a tall building. While many computer programs can provide accurate results for the above, they are time-consuming to run. For designers working on the preliminary design in the conceptual phase, a quick estimation drawn from a simpler analysis is preferable. Therefore, as an alternative to computer-generated estimations, a methodology for an approximate hand calculation of the wind-induced acceleration in an outrigger-braced structure will be developed.

Flotation models describe the separability of mineral particles using a loosely defined term known as floatability or probability of collection, a response of particles in the pulp zone of a flotation vessel, unrelated to events in the froth phase. The Bubble Load measurement samples the particles that have attached to bubbles in the pulp zone and, thus, should give an indication of floatability. This thesis investigates the role of floatability in flotation models, and assesses the Bubble Load measurement as a direct estimate of floatability. Towards these ends, continuous pilot-scale flotation tests were carried out in which collector addition rate was varied. This allowed the floatability of mineral particles to be back-calculated on a size-by-liberation basis and be compared to the measured Bubble Load. Contrary to expectations it was found that, with increasing collector addition rate, the “floatability” of a majority of galena particle classes did not increase after 5 mg/kg of collector, while the measured Bubble Load actually decreased. This was found to be due to the stability of the froth increasing with collector addition rate, causing more galena to reach the concentrate, and less to drop-back to the pulp phase to be reattached. Conversely, there were other particle classes (such as sphalerite and coarse galena) where the expected trends were found, namely increasing floatability and Bubble Load with collector addition rate. These results indicate a high level of interdependence between the pulp and froth zones of the studied flotation cell through the flow of material between them (internal reflux). In the case of galena, the flow of material returning via drop-back from the froth had a greater impact on the Bubble Load than the galena in the feed made sufficiently hydrophobic to attach to bubbles. This means that, for the system studied here, the Bubble Load measurement does not provide a direct estimate of mineral particle floatability, defined as a sole consequence of pulp phase events. Moreover, for the current case, it appears that this definition of floatability is not sufficient to capture the interactions between the pulp and the froth. It is recommended that pulp and froth zone flotation models be developed in concert, recognising the interaction between the two zones, and that flotation models be formulated with due allowance for the material transport paths within a flotation vessel. It should be recognised that “floatability” is an aid for the imagination; a term for a process, rather than a particle “property” to be measured. An extension of the kinetic chemical reaction analogue, incorporating flotation sub-processes, is suggested/revived, to give some phenomenological basis to kinetic flotation models.

This thesis explores the design of flexible pipes, buried in shallow trenches with dry sand backfill. The thesis reports the comprehensive analysis of twenty-two full-scale load tests conducted between 1989 and 1991 on pipe installations, mainly within a laboratory facility, at the University of South Australia. The pipes were highly flexible, spirally-wound, uPVC pipes, ranging in diameter from 300 to 450 mm. Guidelines were required by industry for safe cover heights for these pipes when subjected to construction traffic. The tests were designed by, and conducted under the supervision of, the author, prior to the author undertaking this thesis. As current design approaches for pipes could not anticipate the large loading settlements and hence, soil plasticity, experienced in these tests, finite element analyses were attempted. Extensive investigations of the materials in the installations were undertaken to permit finite element modelling of the buried pipe installations. In particular, a series of large strain triaxial tests were conducted on the sand backfill in the buried pipe installations, to provide an understanding of the sand behaviour in terms of critical state theory. Subsequently a constitutive model for the soil was developed. The soil model was validated before implementation in an element of finite element program, AFENA (Carter and Balaam, 1995). Single element modelling of the triaxial tests proved invaluable in obtaining material constants for the soil model. The new element was applied successfully to the analysis of a side-constrained, plate loading test on the sand. The simulation of the buried pipe tests was shown to require three-dimensional finite element analysis to approach the observed pipe-soil behaviour. Non-compliant side boundary conditions were ultimately adjudged chiefly responsible for the difficulty in matching the experimental data. The value of numerical analyses performed in tandem with physical testing was apparent, albeit in hindsight. The research has identified the prediction of vertical soil pressure above the pipe due to external loading as being the major difficulty for designers. Based on the finite element analyses of the field tests, a preliminary simple expression was developed for estimation of these pressures, which could be used with currently available design approaches to reasonably predict pipe deflections.

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [227]-238).

Thesis (M.S.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 82-85). Also available via the World Wide Web.