Evolutionary Structural Optimisation (ESO) is a relatively new design tool used to improve and optimise the design of structures. It is a heuristic method where a few elements of an initial design domain of finite elements are iteratively removed. Such a process is carried out repeatedly until an optimum design is achieved, or until a desired given area or volume is reached. There have been many contributions to the ESO procedure since its conception back in 1992. For example, a provision known as Bi-Directional ESO (BESO) has now been incorporated where elements may not only be removed, but added. Also, rather than deal with elements where they are either present or not, the designer now has the option to change the element's properties in a progressive fashion. This includes the modulus of elasticity, the density of the material and the thickness of plate elements, and is known as Morphing ESO. In addition to the algorithmic aspects of ESO, a large preference exists to optimise a structure based on a selection of criteria for various physical processes. Such examples include stress minimisation, buckling and electromagnetic problems. In a changing world that demands the enhancement of design tools and methods that incorporate optimisation, the development of methods like ESO to accommodate this demand is called for. It is this demand that this thesis seeks to satisfy. This thesis develops and examines the concept of multicriteria optimisation in the ESO process. Taking into account the optimisation of numerous criteria simultaneously, Multicriteria ESO allows a more realistic and accurate approach to optimising a model in any given environment. Two traditional methods � the Weighting method and the Global Criterion (Min-max) method have been used, as has two unconventional methods � the Logical AND method and the Logical OR method. These four methods have been examined for different combinations of Finite Element Analysis (FEA) solver types. This has included linear static FEA solver, the natural frequency FEA solver and a recently developed inertia FE solver. Mean compliance minimisation (stiffness maximisation), frequency maximisation and moment of inertia maximisation are an assortment of the specific objectives incorporated. Such a study has provided a platform to use many other criteria and multiple combinations of criteria. In extending the features of ESO, and hence its practical capabilities as a design tool, the creation of another optimisation method based on ESO has been ushered in. This method concerns the betterment of the bending and rotational performance of cross-sectional areas and is known as Evolutionary Moment of Inertia Optimisation (EMIO). Again founded upon a domain of finite elements, the EMIO method seeks to either minimise or maximise the rectangular, product and polar moments of inertia. This dissertation then goes one step further to include the EMIO method as one of the objectives considered in Multicriteria ESO as mentioned above. Most structures, (if not all) in reality are not homogenous as assumed by many structural optimisation methods. In fact, many structures (particularly biological ones) are composed of different materials or the same material with continually varying properties. In this thesis, a new feature called Constant Width Layer (CWL) ESO is developed, in which a distinct layer of material evolves with the developing boundary. During the optimisation process, the width of the outer surrounding material remains constant and is defined by the user. Finally, in verifying its usefulness to the practical aspect of design, the work presented herein applies the CWL ESO and the ESO methods to two dental case studies. They concern the optimisation of an anterior (front of the mouth) ceramic dental bridge and the optimisation of a posterior (back of the mouth) ceramic dental bridge. Comparisons of these optimised models are then made to those developed by other methods.

If we are to understand how we can build machines capable of broad purpose learning and reasoning, we must first aim to build systems that can represent, acquire, and reason about the kinds of commonsense knowledge that we humans have about the world. This endeavor suggests steps such as identifying the kinds of knowledge people commonly have about the world, constructing suitable knowledge representations, and exploring the mechanisms that people use to make judgments about the everyday world. In this work, I contribute to these goals by proposing an architecture for a system that can learn commonsense knowledge about the properties and behavior of objects in the world. The architecture described here augments previous machine learning systems in four ways: (1) it relies on a seven dimensional notion of context, built from information recently given to the system, to learn and reason about objects' properties; (2) it has multiple methods that it can use to reason about objects, so that when one method fails, it can fall back on others; (3) it illustrates the usefulness of reasoning about objects by thinking about their similarity to other, better known objects, and by inferring properties of objects from the categories that they belong to; and (4) it represents an attempt to build an autonomous learner and reasoner, that sets its own goals for learning about the world and deduces new facts by reflecting on its acquired knowledge. This thesis describes this architecture, as well as a first implementation, that can learn from sentences such as ``A blue bird flew to the tree'' and ``The small bird flew to the cage'' that birds can fly. One of the main contributions of this work lies in suggesting a further set of salient ideas about how we can build broader purpose commonsense artificial learners and reasoners.

Research in the area of bridge design has been and still isconcentrated on the study of the strength of materials andrelatively few studies have been performed on traffic loads andtheir effects. Traffic loads have usually been assumed to begiven in codes. This is mainly because it is very difficult tomodel traffic loads in an accurate manner because of theirrandomness. In this work, statistical evaluations of traffic loadeffects, obtained from real as well as Monte Carlo (MC)simulated vehicle data, are presented. As the dynamiccontribution of the vehicle load was filtered by the systemused for measuring vehicle weight, no attention was paid in thepresent study to the dynamic effects or the impact factor. Thedynamic contribution of the traffic load models from codes wasdeducted wherever they were compared with the result from theevaluation of the real data. First, the accuracy of thecollected data was investigated. This was done to examine theinfluence of what was most probably unreasonable data on thefinal evaluated results. Subsequently, the MC simulationtechnique, using a limited amount of the collected data, wasused to generate fictitious vehicle data that could representresults from field measurements which would otherwise have tobe recorded under a long period. Afterwards, the characteristictotal traffic loads for bridges with large spans weredetermined by probabilistic analysis. This was done using realas well as simulated data and the two were compared. Theseresults were also compared with the corresponding valuescalculated using the traffic load model from the Swedish bridgedesign code. Furthermore, using traffic data, different load effects onbridges (girder distribution factor of slab-on-girder bridgesand the mid-span deflection as well as the longitudinal stressat critical locations on box-girder bridges) were investigated.The main task was to obtain a more accurate knowledge oftraffic load distributions on bridges as well as their effectsfor infrastructure design. The results showed that the trafficload models from codes gave considerably higher load effectscompared to the current actual traffic load effects. Theseinvestigations were based on the available data for the actualposition of the vehicles on a single bridge and might not coverall possible traffic scenarios. The results showed only how thereal traffic loads, under”normal”conditions andtheir transverse positions relate to the load model accordingto the codes. <b>KEYWORDS:</b>bridge, traffic load, load effect, transversedistribution, characteristic value,weigh in motion, MonteCarlo simulation, Rice’s formula, level crossinghistogram, vehicle queue.

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Fluid dispensing is a method by which fluid materials are delivered to the targeted boards in a controlled manner and has been extensively applied in various packaging processes in the electronics assembly industry. In these processes, the flow rate of the fluid dispensed and/or the fluid amount transferred onto a board are two important performance indexes. Due to the involvement of the compressibility and non-Newtonian behaviour of the fluid being dispensed, modeling the fluid dispensing process has proven to be a challenging task. This thesis presents a study on the modeling of the positive displacement dispensing process, in which the linear displacement of a piston is used to dispense fluid. Also, this thesis presents an evaluation of different designs of the fluid dispensing system based on the axiomatic design principles. <p>At first, the characterization of the flow behaviour of fluids used in the electronic packaging industry is addressed. Based on the previous experiments conducted in the authors lab, a 3-parameter Carreau model for the fluid Hysol FP4451 is derived for use in the present study. Then, taking into account fluid compressibility and flow behaviour, a model is developed to represent the dynamics of the flow rate of the fluid dispensed. The resulting model suggests that the dynamics of the flow rate in the positive displacement dispensing process is equivalent to that of a second order system. Based on the model developed, the influences of the fluid compressibility and the process parameters such as the dispensing time and needle temperature are investigated by simulations. <p>In the positive dispensing process, it is noticed that the fluid amount dispensed out of needle is different from the fluid amount finally transferred to the board, if the fluid amount dispensed is very small. This difference is considered one major problem affecting dispensing performance. In order to determine the fluid amount transferred to the board, a 3-step method is developed in the present study, based on existing theories of liquid bridges and Laplaces equation. Simulations are conducted based on the developed method to study the influence of surface tension and initial fluid amount on the final fluid amount transferred onto the board. <p> Finally, this thesis presents a new approach to evaluate and compare different designs of the fluid dispensing system, namely air-pressure, rotary-crew, and positive- displacement. In this approach, the axiomatic design principles, i.e., the Independence Axiom and the Information Axiom, are employed. This approach can be used not only to evaluate existing dispensing systems, but also to design new dispensing systems.

Vibration-based damage detection (VBDD) methods are structural health monitoring techniques that utilize changes to the dynamic characteristics of a structure (i.e. its natural frequencies, mode shapes, and damping properties) as indicators of damage. While conceptually simple, considerable research is still required before VBDD methods can be applied reliably to complex structures such as bridges. VBDD methods require reliable estimates of modal parameters (notably natural frequencies and mode shapes) in order to assess changes in the condition of a structure. This thesis presents the results of experimental and numerical studies investigating a number of issues related to the potential use of VBDD techniques in the structural health monitoring of bridges, the primary issue being the influence of the excitation source.<p> Two bridges were investigated as part of this study. One is located on Provincial Highway No. 9 over the Red Deer River south of Hudson Bay, Saskatchewan. The other is located near the Town of Broadview, Saskatchewan, off Trans-Canada Highway No. 1, 150 km east of the City of Regina. Field tests and numerical simulations were conducted using different types of excitation to evaluate the quality of the modal properties (natural frequencies and mode shapes) calculated using these excitation types, and thus to evaluate the performance of VBDD techniques implemented using the resulting modal data. Field tests were conducted using different sources of dynamic excitation: ambient, traffic excitation, and impact excitation. The purpose of field testing was to study the characteristics and repeatability of the modal parameters derived using the different types of dynamic excitation, and to acquire data that could be used to update a FE model for further numerical simulation.<p> A FE model of the Red Deer River bridge, calibrated to match the field measured dynamic properties, was subjected to different types of numerically simulated dynamic excitation with different noise (random variations) levels added to them. The types of dynamic excitation considered included harmonic forced excitation, random forced excitation and the subsequent free vibration decay, impact excitation, and different models of truck excitation. The bridge model was subjected to four different damage scenarios; in addition, six VBDD methods were implemented to evaluate their ability to identify and localize damage. The effects of uncertainty in the definition of controlled-force excitation sources and variation in measurement of the bridge response were also investigated.<p> Field tests on the Hudson Bay bridge showed that excitation induced by large trucks generally produced more reliable data than that of smaller vehicles due to higher signal-to-noise ratios in the measured response. It was also found that considering only the free vibration phase of the response after the vehicle left the bridge gave more reliable data. Impact excitation implemented the on Hudson Bay bridge using a spring-hammer yielded repeatable and high quality results, while using a heavy weight delectometer for impact excitation on the Broadview bridge produced results of lesser quality due to the occurrence of multiple strikes of the impact hammer. In general, wind induced vibration measurements taken from both bridges were less effective for defining modal properties than large vehicle loading or impact excitation. All of the VBDD methods examined in this study could detect damage if the comparison was made between modal parameters acquired by eigenvalue analyses of two FE models of the bridge, before and after damage. However, the performance of VBDD methods declined when the dynamic properties were calculated from response time histories and noise was introduced. In general, the damage index method performed better than other damage detection methods considered.<p> Numerical simulation results showed that harmonic excitation, impact excitation, and the free decay phase after random excitation yielded results that were consistent enough to be used for the identification of damage. The reliability of VBDD methods in detecting damage dropped once noise was introduced. Noise superimposed on the excitation force had little effect on the estimated modal properties and the performance of VBDD methods. On the other hand, noise superimposed on the measured dynamic response had a pronounced negative influence on the performance of the VBDD methods.

This thesis presents the results of an investigation into the evaluation of a selected test bridge using instrumentation to obtain site-specific factors contributing to the evaluation, with the ultimate objective of improving the estimate of the bridges reliability in order to assess allowable loading more accurately. The experimental portion of the research program involved instrumenting the test bridge with strain gauges, and recording field measurements using two forms of loading. The analytical portion of the research program involved the analysis of the bridge in the as-designed state, based on the design drawings and specification, followed by a re-analysis of the bridge using the site-specific factors measured on-site. The bridge was evaluated using methods outlined in the Canadian Highway Bridge Design Code CAN/CSA-S6-00 (CSA 2000). <p>The test bridge is located near the community of Hudson Bay, Saskatchewan. The bridge is constructed of steel-reinforced concrete, and there are three, three-span arch-shaped girders. There are also external steel bars added after initial construction to increase the midspan bending moment resistance. In total, 45 strain gauges were placed on the middle spans of the three girders to record strain induced by two forms of loading: controlled loading, in which a truck of known weight and dimensions was driven over the bridge in a number of pre-determined configurations, and in-situ loading, in which normal truck traffic was used. The current allowable loading on the bridge is a gross vehicle weight of 62.5 t, although increasing the allowable loading to 110 t has been proposed, along with two strengthening alternatives to make this increased loading feasible. <p>To provide a base-line analysis for comparison purposes, the bridge was first evaluated based strictly on information taken from the design drawings and specifications. The evaluation was performed using the load and resistance factor method, in which load and resistance factors were used to account for uncertainty, as well as by the mean load method, in which statistical properties of the variables parameters included in the design were used to account for uncertainty. The result of the load and resistance factor method was a live load capacity factor, indicating the overall rating of the bridge. In addition to the live load capacity factor, the mean load method was also used to determine the reliability index. The results of the as-designed analysis showed that the mean load method gave more conservative estimates of the bridge capacity. Furthermore, it was determined that, based on these assessments, the bridge would not have sufficient capacity to carry the proposed 110 t truck loads.<p>The bridge was re-evaluated using site-specific factors with the mean load method. Using the measured strains, statistical parameters were determined for live load effects, distribution factors, dynamic load allowance, and resistance. Statistical parameters that could not be obtained readily through testing were obtained from the literature. The results indicated that code-predicted estimates of a number of factors were highly conservative. Flexural and shear load effects in the girders were found to be less than 15% of the theoretical predictions, as a result of apparent arching action in the girders, generating significant axial forces. For this arching action to occur, horizontal restraint was required at the supports, either through unanticipated restraint in the bearings, or tension tie action of the tensile girder reinforcement. Furthermore, the dynamic amplification was found to be less than 1.0. The resulting reliability indices indicated that the bridge would be safe under the proposed increased allowable loading (110 t). <p>Finite element models were used to confirm the dynamic amplification observations and examine the effects of different degrees of bearing restraint. The model showed results similar to those measured for dynamic amplification. It was found that if the bearings were to become completely fixed against horizontal translation, the bridge would become overloaded as a result of increased shear effects, demonstrating the need for proper bearing maintenance. <p>An analysis of relative costs was completed to determine the most cost-effective solution for hauling logs. Assumptions were made regarding truck and maintenance and operating costs. The results indicated that the most economic solution was to use the method outlined in the research to increase the allowable loading on the bridge to 110 t, over the strengthening alternatives and simply leaving the bridge in the current state.