Reliability levels of Japanese 2x4 wood frame structures were evaluated using lumber property data derived from evaluation of Canadian Spruce-Pine-Fir dimension lumber. The evaluations were made using the "Standard for Limit States Design of Steel Structures (Draft)", which was newly published by the LRFD Subcommittee of Architectural Institute of Japan, and In-Grade Data obtained by a Canadian Wood Council research project. These analyses were implemented using the computer program "RELAN" developed by Dr. R.O. Foschi at UBC and Monte Carlo simulations. Reliability levels of current Japanese 2x4 wood frame structures were also evaluated. Recommendations were made to encourage the application of limit states design into existing Japanese design methods. / Forestry, Faculty of / Graduate

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The increasing integration of digital information with our daily lives has led to the rise of big data, cloud computing, and the internet of things. The growth in these categories will lead to an exponential increase in the required capacity for data centers and high performance computation. Meanwhile, due to bottlenecks in data access caused by the limited energy and bandwidth scalability of electrical interconnects, computational speedup can no longer scale with demand. A better solution is necessary in order to increase computational performance and reduce the carbon footprint of our digital future. People have long thought of photonic interconnects, which can offer higher bandwidth, greater energy efficiency, and orders-of-magnitude distance scalability compared to electrical interconnects, as a solution to the data access bottleneck in chip, board, and datacenter scale networks. Over the past three decades we have seen impressive growth of photonic technology from theoretical predictions to high-performance commercially available devices. However, the dream of an all-optical interconnection network for use in CPU, Memory, and rack-to-rack datacenter interconnects is not yet realized. Many challenges and obstacles still have to be addressed. This work investigates these challenges and describe some of the ways to overcome them. First we will first examine the pattern sensitivity of microring modulators, which are likely to be found as the first element in an optical interconnect. My work will illustrate the advantage of using depletion mode modulators compared to injection mode modulators as the number of consecutive symbols in the data pattern increases. Next we will look at the problem of thermal initialization for microring demultiplexers near the output of the optical interconnect. My work demonstrates the fastest achieved initialization speed to-date for a microring based demultiplexer. I will also explore an thermal initialization and control method for microrings based on temperature measurement using a pn-junction. Finally, we will look at how to control and initialize microring and MZI based optical switch fabrics, which is the second element found in a optical interconnect. Work here will show the possibility of switching high-speed WDM datastreams through microring based switches, as well as methods to deal with the complexities inherent in control and initialization of high-radix switch topologies. Through these demonstrations I hope to show that the challenges facing optical interconnects, although very real, are surmountable using reasonable engineering efforts.

Many methods have been developed and studied to detect damage through the change of dynamic response of a structure. Due to its capability to recognize pattern and to correlate non-linear and non-unique problem, Artificial Neural Networks (ANN) have received increasing attention for use in detecting damage in structures based on vibration modal parameters. Most successful works reported in the application of ANN for damage detection are limited to numerical examples and small controlled experimental examples only. This is because of the two main constraints for its practical application in detecting damage in real structures. They are: 1) the inevitable existence of uncertainties in vibration measurement data and finite element modeling of the structure, which may lead to erroneous prediction of structural conditions; and 2) enormous computational effort required to reliably train an ANN model when it involves structures with many degrees of freedom. Therefore, most applications of ANN in damage detection are limited to structure systems with a small number of degrees of freedom and quite significant damage levels. In this thesis, a probabilistic ANN model is proposed to include into consideration the uncertainties in finite element model and measured data. Rossenblueth's point estimate method is used to reduce the calculations in training and testing the probabilistic ANN model. The accuracy of the probabilistic model is verified by Monte Carlo simulations. Using the probabilistic ANN model, the statistics of the stiffness parameters can be predicted which are used to calculate the probability of damage existence (PDE) in each structural member. The reliability and efficiency of this method is demonstrated using both numerical and experimental examples. In addition, a parametric study is carried out to investigate the sensitivity of the proposed method to different damage levels and to different uncertainty levels. As an ANN model requires enormous computational effort in training the ANN model when the number of degrees of freedom is relatively large, a substructuring approach employing multi-stage ANN is proposed to tackle the problem. Through this method, a structure is divided to several substructures and each substructure is assessed separately with independently trained ANN model for the substructure. Once the damaged substructures are identified, second-stage ANN models are trained for these substructures to identify the damage locations and severities of the structural ii element in the substructures. Both the numerical and experimental examples are used to demonstrate the probabilistic multi-stage ANN methods. It is found that this substructuring ANN approach greatly reduces the computational effort while increasing the damage detectability because fine element mesh can be used. It is also found that the probabilistic model gives better damage identification than the deterministic approach. A sensitivity analysis is also conducted to investigate the effect of substructure size, support condition and different uncertainty levels on the damage detectability of the proposed method. The results demonstrated that the detectibility level of the proposed method is independent of the structure type, but dependent on the boundary condition, substructure size and uncertainty level.

Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In this dissertation the traditional model-centred (MC)design approach for the development of software in the civil engineering field is compared to a newly developed application-centred (AC)design approach. In the MC design software models play the central role. A software model maps part of the world, for example its visualization or analysis onto the memory space of the computer. Characteristic of the MC design is that the identifiers of objects are unique and persistent only within the name scope of a model, and that classes which define the objects are components of the model. In the AC design all objects of the engineering task are collected in an application. The identifiers of the objects are unique and persistent within the name scope of the application and classes are no longer components of a model, but components of the software platform. This means that an object can be a part of several models. It is investigated whether the demands on the information and communication in modern civil engineering processes can be satisfied using the MC design approach. The investigation is based on the evaluation of existing software for the analysis and design of a sewer reticulation system of realistic dimensions and complexity. Structural, quantitative, as well as engineering complexity criteria are used to evaluate the design. For the evaluation of the quantitative criteria, in addition to the actual Duration of Execution, a User Interaction Count, the Persistent Data Size, and a Basic Instruction Count based on a source code complexity analysis, are introduced. The analysis of the MCdesign shows that the solution of an engineering task requires several models. The interaction between the models proves to be complicated and inflexible due to the limitation of object identifier scope: The engineer is restricted to the concepts of the software developer, who must provide static bridges between models in the form of data files or software transformers. The concept of the ACdesign approach is then presented and implemented in a new software application written in Java. This application is also extended for the distributed computing scenario. Newbasic classes are defined to manage the static and dynamic behaviour of objects, and to ensure the consistent and persistent state of objects in the application. The same structural and quantitative analyses are performed using the same test data sets as for the MCapplication. It is shown that the AC design approach is superior to the MC design approach with respect to structural, quantitative and engineering complexity .criteria. With respect to the design structure the limitation of object identifier scope, and thus the requirement for bridges between models, falls away, which is in particular of value for the distributed computing scenario. Although the new object management routines introduce an overhead in the duration of execution for the AC design compared to a hypothetical MC design with only one model and no software bridges, the advantages of the design structure outweigh this potential disadvantage. / AFRIKAANSE OPSOMMING: In hierdie proefskrif word die tradisionele modelgesentreerde (MC)ontwerpbenadering vir die ontwikkeling van sagteware vir die siviele ingenieursveld vergelyk met 'n nuut ontwikkelde applikasiegesentreerde (AC) ontwerpbenadering. In die MContwerp speel sagtewaremodelle 'n sentrale rol. 'n Sagtewaremodel beeld 'n deel van die wêreld, byvoorbeeld die visualisering of analise op die geheueruimte van die rekenaar af. Eienskappe van die MContwerp is dat die identifiseerders van objekte slegs binne die naamruimte van 'n model uniek en persistent is, en dat klasse wat die objekte definieer komponente van die model is. In die AC ontwerp is alle objekte van die ingenieurstaak saamgevat in 'n applikasie. Die identifisieerders van die objekte is uniek en persistent binne die naamruimte van die applikasie en klasse is nie meer komponente van die model nie, maar komponente van die sagtewareplatform. Dit beteken dat 'n objek deel van 'n aantal modelle kan vorm. Dit word ondersoek of daar by die MC ontwerpbenadering aan die vereistes wat by moderne siviele ingenieursprosesse ten opsigte van inligting en kommunikasie gestel word, voldoen kan word. Die ondersoek is gebaseer op die evaluering van bestaande sagteware vir die analise en ontwerp van 'n rioolversamelingstelsel met realistiese dimensies en kompleksiteit. Strukturele, kwantitatiewe, sowel as ingenieurskompleksiteitskriteria word gebruik om die ontwerp te evalueer. Vir die evaluering van die kwantitatiewe kriteria word addisioneel tot die uitvoerduurte 'n gebruikersinteraksie-telling, die persistente datagrootte, en 'n basiese instruksietelling gebaseer op 'n bronkode kompleksiteitsanalise , ingevoer. Die analise van die MC ontwerp toon dat die oplossing van ingenieurstake 'n aantal modelle benodig. Die interaksie tussen die modelle bewys dat dit kompleks en onbuigsaam is, as gevolg van die beperking op objekidentifiseerderruimte: Die ingenieur is beperk tot die konsepte van die sagteware ontwikkelaar wat statiese brue tussen modelle in die vorm van lêers of sagteware transformators moet verskaf. Die AC ontwerpbenadering word dan voorgestel en geïmplementeer in 'n nuwe sagteware-applikasie, geskryf in Java. Die applikasie word ook uitgebrei vir die verdeelde bewerking in die rekenaarnetwerk. Nuwe basisklasse word gedefinieer om die statiese en dinamiese gedrag van objekte te bestuur, en om die konsistente en persistente status van objekte in die applikasie te verseker. Dieselfde strukturele en kwantitatiewe analises word uitgevoer met dieselfde toetsdatastelle soos vir die MC ontwerp. Daar word getoon dat die AC ontwerpbenadering die MC ontwerpbenadering oortref met betrekking tot die strukturele, kwantitatiewe en ingenieurskompleksiteitskriteria. Met betrekking tot die ontwerpstruktuur val die beperking van die objek-identfiseerderruimte en dus die vereiste van brue tussen modelle weg, wat besonder voordelig is vir die verdeelde bewerking in die rekenaarnetwerk. Alhoewel die nuwe objekbestuurroetines in die AC ontwerp in vergelyking met 'n hipotetiese MC ontwerp, wat slegs een model en geen sagteware brue bevat, langer uitvoerduurtes tot gevolg het, is die voordele van die ontwerpstruktuur groter as die potensiële nadele.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Actionl'I' is a project undertaken by a consortium consisting of CSIR, Simeka Management Consulting, University of Pretoria and the University of Stellenbosch for the Innovation Fund of the Department of Arts, Culture, Science and Technology in South Africa. Their objective is to create a basic specification for seletected information exchange that is compatible with all levels of government. The comparison between existing information systems at municipal level and ActionIT specifications will be investigated for the purpose of exposing shortcomings on both sides. Appropriate features of existing information systems will be identified for the purpose of enhancing the ActionIT specifications. The ActionIT project is presently in its user requirement and conceptual model definition phase, and this thesis aims to assist in providing information that may be helpful infuture developments. The study undertaken in this thesis requires the application of analytical theory and a working knowledge of information systems and databases in order to: 1. Research existing information systems and relevant engineering data at local municipal authorities. Also important will be the gathering of information regarding systems currently in use, and the format in which information is stored and utilised at municipalities. 2. Do an adequate analysis of the contents of recorded information. This information will establish background knowledge on the operations of local authorities and a clearer understanding of information systems. 3. Evaluate to what degree existing information systems comply with ActionIT specifications. This will be the main focus of this thesis. Thus the focus of this thesis is to record (provide an overview oj) activities in a municipal environment and the interaction with the environment on information system level where standards provided by ActionIT as an Open Decision Support Framework can be of value. / AFRIKAANSE OPSOMMING: ActionIT is in projek wat deur ActionIT konsortium bestaande uit die WNNR, Simeka Management Consulting, Universiteit van Pretoria en die Universiteit van Stellenbosch, onderneem is vir die Innovasie Vonds van die departement van Kuns, Kultuur, Wetenskap en Tegnologie van Suid-Afrika. Hul mikpunt is om in spesifikasie vir informasie sisteme te onwikkel, wat met alle vlakke van regering kan skakel. Die vergelyking tussen die bestaande informasie sisteme op munisipale vlak en ActionIT spesifikasies salondersoek word vir die doelom tekortkominge aan beide kante uit te wys. Vir die verbetering van ActionIT spesifikasies moet aanvaarbare eienskappe van bestaande informasie sisteme geindentifiseer word. Die ActionIT projek is tans in die gebruikers vereiste en konseptueIe model definisie fase, en die tesis is gemik daarop om 'n bydrae te lewer tot die bevordering van informasie wat mag help in toekomstige ontwikkeling. Die werk onderneem in die tesis vereis in teoretiese kennis van informasie sisteme en databasise om: 1. in Ondersoek in die bestaande informasie sisteem en relefante ingenieurs data van in plaaslike munisipaliteit te doen. Die insameling van informasie oor die huidige sisteme in gebruik, die formaat waarin die informasie gestoor en gebruik word is ook belangrik. 2. in Analise van die inhoud van die waargenome informasie te doen. Die informasie sal agtergrond kennis gee oor die werking van plaaslike munisipale owerheid en in beter insig in informasie sisteme gee. 3. in Evaluasie van die verband tussen die bestaande informasie sisteme en ActionIT spesifikasies te doen. Dit is die hoof fokus punt van die tesis. Dus die doel van die tesis is om in oorsig te gee oor die aktiviteite in in munisipale omgewing en die interaksie met die omgewing op informasie sisteem vlak. Waar standaarde wat deur ActionIT voorgeskryf word as in "Open Decision Support Framework" van belang kan wees.

published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

M.Ing. / Traffic has become an extreme irritation and costly entity to deal with in recent years. Gone are the days where one could simply widen roadways to increase flow rates due to space constraints. Traffic costs countries billions of dollars per annum and thus the need to alleviate traffic congestion. Many technologies are currently available that can be used to lower the traffic density at an intersection, one of them being the use of cameras. Not only are digital cameras dropping in price, but the associated cost of maintenance is low. Distance information of a scene can thus be calculated via a visual system and from this information advanced control can be implemented in order to maximise traffic flow through an intersection. A traffic simulator was coded and analysed in order to validate the use of a visual system for increasing the amount of cars passing through the intersection per unit time over the current fixed timing system. Two different algorithms were compared to the current fixed timing scheme using a traffic simulator. The results showed that an improvement can be achieved over the current fixed timing scheme (of up to 19.92%). The use of stereovision as a method of attempting to monitor traffic flow is discussed. Vehicles were tracked using 13 trackers and the distance away from the stereo setup was calculated and compared to the actual distance away from the stereo setup. The best results found that with a baseline distance of 1500mm the average error in determining the distance of a vehicle was 16.46m. Although this error is quite large, it is still possible to monitor traffic flow using stereo vision with these inputs. Some of the issues that may cause these errors are camera quality, camera calibration and variable lighting conditions.

No description available.