Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Structural analysis is examined in order to identify its essential information requirements, its fundamental tasks, and the essential functionalities that applications which support it should provide. The special characteristics of the information content of structural analysis and the algorithms that operate on it are looked into and exploited to devise data structures and utilities that provide proper support of the analysis task within a local environment, while presenting the opportunity to be extended to the context of a distributed network-based collaboratory as well. Aspects regarding the distribution of analysis parameters and methods are analysed and alternatives are evaluated. The extentions required to adapt the local data structures and utilities for use in a distributed communication network are developed and implemented in pilot form. Examples of collaborative analysis are shown, and an evaluation of the overhead involved in distributed work is performed. / AFRIKAANSE OPSOMMING: 'n Ondersoek van die struktuuranalise-taak word uitgevoer waarin die kerninligtingsbehoeftes en fundamentele take daarvan, asook die vereisde funksionaliteit van toepassings wat dit ondersteun bepaal word. Die besondere eienskappe van struktuuranalise-inligting en die algoritmes wat daarop inwerk word ondersoek en benut om data strukture en metodes te ontwikkel wat die analise-taak goed ondersteun in In lokale omgewing, en wat terselfdertyd die moontlikheid bied om sodanig uitgebrei te word dat dit ook die taak in 'n verspreide samewerkingsgroepering kan ondersteun. Aspekte van die verspreiding van analiseparameters en metodes word ondersoek en alternatiewe oplossings word evalueer. Die uitbreidings wat nodig is om die datastrukture en metodes van die lokale omgewing aan te pas vir gebruik in verspreide kommunikasienetwerke word ontwikkel en in loodsvorm toegepas. Voorbeelde van samewerking-gebasseerde analise word getoon, en die oorhoofse koste verbonde aan analise in 'n verdeelde omgewing word evalueer.

Thesis (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The problem of how the mind relates to the brain stands as one of the greatest challenges today. The materialistic worldview and pragmatic approach to social problems are both being transformed by discoveries of how human experience and culture arise in cerebral activity. Even so, this effort, spearheaded by neuroscience, has seen the important and contentious issue of driver behaviour somehow been left behind. From an extensive literature study, it can be concluded that gross disregard of the neural underpinnings of such behaviour tied to a behaviouristic approach is endemic to the field. Numerous qualitative psychological models (each associated with debates about their validity) and Artificial Intelligence models, which effectively only imitate robots 'impaired' to display some humanlike characteristics, were come across. Although neural networks are derived from current knowledge of computation within the brain and deployed in industry, human driver behaviour modelling is not benefiting from this revolution in humanlike information processing. To date, very little has been done to determine what makes road users speed, drive while drunk, overtake, or yield at crossroads. As the central nervous system is the human measuring device in and of the world and thus key affector of human behaviour, it is ofutrnost importance to invest resources in 'inoculating' the field of driver behaviour modelling onto a robust basis provided by neuroscience. Being a human driver incorporates a broad complement of interrelated brain systems to perform driving tasks (psychological functions) at hand, such as lane keeping, speed choice, risk perception, and obstacle avoidance. The proper level of analysis of such a psychological function is the level at which that function is represented in the brain. Providing a theoretical model of human behaviour, based on biological facts of the brain as a whole, is surely a challenge for decades to come, but the field of driver behaviour should be part of such an effort. Collaboration is needed among investigators from the fields of neuroscience, psychology, mathematics, computer science, and engineering to further driver behaviour modelling. It is uncommon that professionals from these fields have a thorough understanding of the other fields involved, but the author, not pretending to be an expert, argues that such a union of fields will be of significant value not only to transportation, but all behavioural sciences. The wealth of to-date knowledge amassed in neuroscience lies ready to be tapped by researchers interested in explaining human driver behaviour. To this end, the use of modem brain-imaging techniques will be invaluable in pinning down the neural correlates of particular driving subtasks, bearing in mind the extent of structural impacts on the brain of each individual, brought about by a lifetime of interaction with the environment. Thus, based on the findings of this literature study, the author proposes that supplementary work be conducted by a multi-disciplinary team to roll-out an experiment to study the nature of environmental stimuli as instigators of aggression and road rage, by drawing on knowledge about brain imaging and (amygdala) activation. / AFRIKAANSE OPSOMMING: Die vraagstuk hoe die verstand [denke] met die brein in verband staan, is een van die grootste uitdagings tans. Die materialistiese wêreldbeskouing sowel as die pragmatiese benadering van maatskaplike probleme word verander deur ontdekkings aangaande die wyse waarop menslike ervaring en kultuur hul in serebrale aktiwiteit voordoen. Desondanks is in hierdie poging, met die neurowetenskap aan die spits, die belangrike en omstrede kwessie van bestuurdersgedrag om een of ander rede agterweë gelaat. Uit 'n uitgebreide literatuurstudie kan afgelei word dat grootskaalse verontagsaming van die neurale basis van sodanige gedrag gekoppel aan 'n behavioristiese benadering endemies is aan die gebied. Talle kwalitatiewe sielkundige modelle en kunsmatige intelligensiemodelle is teëgekom, elk gepaard met debatte oor die geldigheid daarvan. Hoewel neurale netwerkmodelle gebaseer word op huidige kennis van verwerking binne die brein en ontplooi word in die industrie, trek menslike bestuurdersgedragmodellering nie voordeel uit hierdie revolusie in neurale inligtingsverwerking nie. Tot op hede is baie min gedoen om vas te stel waarom padgebruikers jaag, dronkbestuur, verbysteek of by kruispaaie toegee. Aangesien die sentrale senuweestelsel die menslike meettoestel in en van die wêreld is en dus die sleutelbeïnvloeder van menslike gedrag is, is dit van die uiterste belang om middele te investeer in die fundering van die gebied van bestuurdersgedragmodellering op 'n stewige basis daargestel deur die neurowetenskappe. Om'n menslike bestuurder te wees behels 'n omvattende komplement van verbandhoudende breinstelsels om bestuurstake (sielkundige funksies) te verrig, soos spoedkeuse, risikowaarneming en die vermyding van obstruksies. Die gepaste ontledingsvlak van so 'n sielkundige funksie is die vlak waarop daardie funksie in die brein verteenwoordig word. Die daarstelling van 'n teoretiese model van menslike gedrag, gebaseer op biologiese feite van die brein in die geheel, is gewis nog vir komende dekades 'n uitdaging, maar die gebied van bestuurdersgedrag moet deel uitmaak van so 'n pogmg. Samewerking is nodig tussen navorsers uit die neurowetenskappe, sielkunde, wiskunde, rekenaarwetenskap en ingenieurswese om bestuurdersgedragmodellering te bevorder. Dit is ongewoon dat vakkundiges uit hierdie velde 'n deeglike begrip het van die ander gebiede wat betrokke is, maar die outeur, sonder om voor te gee dat hy 'n deskundige is, betoog dat so 'n samesnoering van vakgebiede van betekenisvolle waarde sal wees, nie net vir die vervoerwese nie, maar ook vir al die gedragwetenskappe. Die omvang van die jongste kennis wat in die neurowetenskappe vergaar is, lê gereed om deur navorsers benut te word wat belang stel in die verklaring van menslike bestuurdersgedrag. Met dié doel sal die gebruik van moderne breinskanderingstegnieke van onskatbare waarde wees om die neurale korrelate van bepaalde bestuursubtake vas te pen, gedagtig aan die omvang van strukturele impakte op die brein van elke indiwidu teweeggebring deur 'n leeftyd van interaksie met die omgewing. Daarom, gebaseer op die bevindinge van hierdie literatuurstudie, stel die outeur voor dat addisionele werk gedoen word deur 'n multi-dissiplinêre span ten einde 'n eksperiment uit te voer, waarin die aard van stimuli uit die omgewing, wat lei tot padwoede, bestudeer kan word, met inagneming van die beskikbare kennis oor breinskandering en (amygdala) -aktiveringpatrone.

Thesis (PhD (Civil Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: In South Africa, wind constitutes the most critical environmental loading affecting the design of the built environment. The wind climatic information, which is currently incorporated in structural design standards, is based on the analysis of records from a limited number of wind recording stations, mainly located in large cities, and was done several decades ago. In view of the size and the climatological diversity of South Africa, this information cannot be deemed to be adequate. Therefore, the incorporation of welldistributed and updated information on wind climate is essential. The present study endeavoured to address this issue. A strong wind climatology was developed with the use of observed climate data, with the most significant result that a mixed strong wind climate is prevalent in the greater part of South Africa. Statistical approaches to estimate extreme wind speeds were investigated with applicable wind data, with the optimum approach guided by the unique climatological environment and the statistical properties of the utilised data set: For the wind gust analysis the Peak-Over-Threshold method with the exponential distribution is recommended, while in a mixed strong wind climate the “mixed climate” approach is preferred. For the analysis of the hourly mean wind speeds the choice is between the Gumbel distribution and the mixed climate approach, depending on the strong wind climate. The estimation and incorporation of environmental correction factors to the measured wind speeds were necessary as the surroundings of most weather stations did not correspond to the reference Terrain Category. For some of the weather stations it was impossible to compensate for the inadequate exposure and surrounding complex topography, so that a reduced number of weather stations were available for the strong wind analyses. The values estimated for the design wind speeds, adjusted for the short lengths of data records, as well as techniques developed to guide the spatial interpolation of the quantiles, were utilised to develop updated maps of the regional design wind speeds. A comparative study between the results of this study, and that of the previous study on which the current loading code in South Africa is based, indicates that the present study should produce more reliable quantile estimations. / AFRIKAANSE OPSOMMING: Wind vorm die mees kritieke omgewingslading wat die ontwerp van die beboude omgewing in Suid-Afrika beïnvloed. Die windklimaat-inligting wat tans gebruik word in die ontwerp spesifikasies is gebaseer op die statistiese analiese van veskeie dekades gelede op ‘n beperkte aantal windmeting-stasies, hoofsaaklik gesentreer in groot stede. Indien die grootte sowel as die klimatologiese diversiteit van Suid-Afrika in ag geneem word kan hierdie inligting nie as voldoende gereken word nie. Die gebruik van heelwat beter verspreide en opgedateerde inligting oor die windklimaat is daarom noodsaaklik en die studie poog om hierdie leemte aan te spreek. ‘n Sterk-wind klimatologie van Suid-Afrika is ontwikkel deur die gebruik van waargenome klimaatdata, met die mees betekenisvolle bevinding dat ‘n gemengde sterk-wind klimaat in die grootste gedeelte van Suid-Afrika heers. Statistiese benaderings om ekstreme winde te beraam is ondersoek met die beskikbare winddata, met die optimale benadering wat sal afhang van die klimatologiese omgewing van die weerstasie en die statistiese eienskappe van die betrokke windrekord: Vir die wind-stoot analieses word die “Piek-Oor-Drumpel” metode met die eksponensïele verdeling aanbeveel, behalwe in ‘n gemengde sterkwind klimaat waar die “gemengde klimaat” benadering gebruik word. Vir die analiese van die uurlikse gemiddelde winde is die keuse tussen die Gumbel verdeling en die gemengde klimaat benadering, afhangende van die sterk-wind klimaat. Die skatting en toepassing van omgewingskorreksiefaktore vir die windspoed was nodig, aangesien die omgewings waarin die meeste weerstasies is nie ooreenkom met die verwysings Terrein Kategorie nie. Vir sommige weerstasies was dit onmoontlik om vir die onvoldoende blootstelling te vergoed, met die gevolg dat minder stasies beskikbaar was vir die sterk wind analiese. Die geskatte waardes vir die ontwerp-windsnelhede, asook tegnieke ontwikkel vir ruimtelike interpolasie, is gebruik vir die ontwikkeling van kaarte van die omgewings-ontwerpsnelhede, na verstellings van die waardes om te vergoed vir die kort data rekords wat gebruik is. ‘n Kritiese vergelykingstudie wat gedoen is tussen die resultate van die huidige studie, en die vorige waarop die huidige laskodes vir Suid-Afrika gebaseer is, dui aan dat die huidige studie betroubaarder skattings van die kwantiele behoort op te lewer.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: South Africa is a relatively dry country with an annual average rainfall of 464mm compared to a world average of 860mm (WSA, 2009). Water shortages and droughts are fairly common to the western and high lying of regions South Africa. Due to its population growth and the rapid development, like the rest of the world, there has been an increased demand for water. Due to increasing costs of procuring water and its decreasing availability, the option of using seawater as a source for freshwater or directly in industrial processes has become competitive, especially in the arid parts of the world. The design of seawater intakes forms an integral part of providing a secure source of seawater. The objective of this thesis is to aid in the development of guidelines for the design of small scale seawater abstraction systems on rocky coastlines using the Horizontal Well Method. Recommendations for guidelines will be given. / AFRIKAANSE OPSOMMING: Geen opsomming

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: All structures are designed for a particular set of load combinations. For roof structures the critical loading combinations are predominantly wind actions. The accumulative effect of wind actions, by wind entering through dominant openings to exert pressure on the inside of roof structures together with the suction of wind vortices on the outside of the roof, can contribute to extreme load combinations. Frequently recorded failures on roof structures suggest that either the loads are underestimated or the resisting capacity of the roof coverings is overestimated. The focus of this study is directed on the latter, determining the effective resistance of roof coverings in the form of sheeting against a Uniformly Distributed Load (UDL) such as wind actions. To determine the carrying capacity of a roofing structure, the standard approach used involves experimental tests on certain configurations with two or more spans. The structural test set-up is loaded with sandbags until failure is reached. For the design of roofing systems, design tables are used that list the maximum allowable purlin spacing. The purlin spacing is presented in the form of a fixed value in units of length and is shown independent of a UDL that the roof needs to be designed for. The need to a new approach to determining the resistance of roof covering systems was identified. The resistance of roof coverings for the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS) depends on a number of parameters such as the bending resistance, the stiffness of the sheeting in bending and the carrying capacity of the fastening system. To evaluate these structural parameters, experimental tests were performed. A full-scale experimental test setup, capable of simulating a UDL on roof sheeting, was developed. The experimental test set-up consists of four different configurations, each specifically schematized to evaluate a certain structural design parameter. The magnitude of the structural design parameters depends on the applied UDL and the span length, which is the distance between consecutive supports of the sheeting system. Therefore, by using the structural design parameters determined experimentally, a set of design tables could be generated. The design tables produce the maximum allowable span length of a roofing system that uses a desired UDL as a variable. By using the design tables, the purlin spacing for any roof structure can be calculated given its design loading combination. The calculated purlin spacings are now a function of the basic parameters that determine the resistance of the roof sheeting. / AFRIKAANSE OPSOMMING: Geen opsomming

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009.

Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2006. / Some experiments utilizing the shear capacity of Engineered Cement-based Composites (ECC) have suggested that elimination of shear reinforcement is feasible when the concrete matrix is replaced by ECC. However, actual application and more rigorous cost analysis are prevented by the fact that the shear stress and strain properties of ECC have not yet been characterized as accurately as the tensile properties. This study focuses on the investigation of the shear property of ECC. The study starts with a survey and comparison of existing shear tests for composite materials. The Iosipescu shear test concept is chosen as the most objective method for ECC, and subsequently, modified for specific application on ECC by simple analytical design and finite element refinement. The modified Iosipescu shear test method is applied on, four types of ECC specimens with different fibre content (0%, 1%, 2%, 2.5% by volume), which have been cast in specially designed moulds and cured in laboratory conditions. Three phases of shear measurements are used to check the shear test appropriateness and study the shear mechanical properties of ECC. The failure mode is verified in the first phase, detailed measurement of the shear strain and shear stress is performed and recorded in the second phase, and in the third phase more information about the ductility of diagonal cracking is obtained by measurement of the tensile principal deformation. By also conducting direct tensile tests on specimens of the exact same mix, information of both uniaxial tension and shear behaviour is available, from which elastic and shear moduli, as well as Poisson’s ratio of ECC are computed. A first step toward application of this knowledge of the shear behaviour of ECC is taken by studying the response of shear-dominated beams and beam-columns of reinforced concrete and reinforced concrete combined with ECC as the outer crusts. These beams were prepared and tested by other members of the research group of the Division for Structural Engineering of the University of Stellenbosch. It is shown that ECC can indeed successfully replace shear reinforcing steel, due to its shear capacity.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2007. / Mozambique is investing heavily in rehabilitating and upgrading the current roadway infrastructure. Investigation by the Mozambican roads authority found that some consulting engineers and contractors were not familiar with Mozambican conditions and materials. The World Bank sponsored a research project to support the roadway infrastructure preservation and maintenance efforts. The thesis work presented forms an integral part of the work conducted by the World Bank project research team. The objective of the thesis is to characterise cement stabilized sand bases in Mozambique under Accelerated Pavement Testing (APT) in terms of stiffness and deflection responses under load trafficking. This work forms the basis for developing guidelines for a mechanistic-empirical design method for Mozambican conditions and materials. Reported findings from initial MMLS3 testing conducted for the World Bank project were used to scope the full-scale research study and provided guidelines for the selection and construction of full scale test sections on natural subgrade. The APT presented encompass full-scale pavement testing including wet trafficking cycles to emulate environmental effects.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: See item for full text / AFRIKAANSE OPSOMMING: Sien item vir volteks

Thesis (MScEng)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: It is argued that an understanding of variability is central to the modelling of travel behaviour and the assessment of policy impacts and is not the peripheral issue that it has often been considered. There is a growing need to assess multi-day data to assess the distribution of user charges for road pricing, or patterns of public transport usage as well as improve the ability to identify mechanisms behind travel behaviour for modelling purposes. Drawing on studies worldwide, in conjunction with a review of the literature, the thesis first examines the relevance for using multi-day data, then discusses the methodology and results of a five week survey undertaken specifically for this study, makes a comparison of the findings with that observed in other studies, and finally discusses issues relating to the application of the data and future research possibilities. Previous studies have shown that behaviour which makes up the daily travel pattern can be highly repetitious in nature but that observing an individual’s behaviour on a single day might not be representative of their routine travel and that this behaviour varies across demographic segments and driver gender. This paper examines day-to-day travel behaviour variability of a residential area, Summer Greens, located in Cape Town (South Africa) using a travel dataset collected recently in November/December 2006. The survey technique employed was the recording of numberplates of all exiting vehicles from 06:00 to 10:00, weekdays from Monday to Friday over a period of five weeks. A total of 5677 vehicles undergoing 44 743 trips was observed and analysed. This research replicates and extends previous work dealing with day-to-day variability in trip-making behaviour that was conducted with data collected by Del Mistro and Behrens (2006) in Buitengracht Street, Cape Town CBD, in July/August 2005. The present research extends the earlier work by including departure time variations as well as conducting the observations during both a school period (3 weeks) and consecutive holiday period (2 weeks). Further, the thesis presents a method to measure day-to-day variability using the available data surveyed. This thesis finds a considerable difference in school and holiday traffic volumes as expected, but that despite this, certain identical travel behaviour patterns (such as vehicle appearance frequencies, following week repeat proportions etc.) is observed during both these periods. It was found that the peak hour for both school and holiday periods occurred during the same time period and greater traffic volume variability was found to occur on Fridays during the holiday period than in the school period. Traffic volumes across all weeks appeared to decrease from Monday to Wednesday and “bounce back” on Thursday and Friday consistent with the findings of another international study. It was found that motorists exhibited more departure time freedom during the holiday period with average holiday departure times much later than during the school period. Departure times were also observed to gradually become later from Monday to Friday during both the school and holiday periods with Thursday and Friday departure times significantly different to the other weekdays. The proportion of unique vehicles observed was found to increase with time of day and the resulting impact of this on the effectiveness of Variable Message Sign (VMS) applications is also discussed. The research concludes by applying the findings to determine the impact of a hypothetical congestion pricing scheme on traffic volumes. / AFRIKAANSE OPSOMMING: Die argument is dat ‘n begrip vir variasie sentraal staan tot die modellering van reisgedrag en die assessering van beleidsimiplikasies, en is dus nie net n nagedagte soos wat gereeld gedink word nie. Daar is ‘n toenemende behoefte om multi-dag data te analiseer om die verspreiding in gebruikerskostes te bestudeer vir die waardasie van paaie, of om verhoudings in publieke vervoergebruik uit te lig, asook, vir die verbetering van die vermoë om die meganismes agter reisgedrag te identifiseer vir modelleringsdoeleindes. Die tesis bestudeer eerstens die relevansie van die gebruik van multi-dag data in samewerking met die literatuurstudie, gebaseer op studies wêreldwyd onderneem. Tweedens bespreek dit die metodologieë en resultate van ‘n vyf-week lange opname wat spesifiek vir hierdie studie onderneem is en tref vergelykings met die resultate verkry deur vorige studies. Dit bespreek dan die probleme wat voortspruit uit die toepassing van die data en ook toekomstige moontlikhede tot verdere navorsing. Vorige studies het getoon dat die gedrag wat tydens daaglikse reispatrone voorkom van nature hoogs herhaaldelik is. Wanneer ‘n individu se gedrag observeer word op ‘n enkele dag is dit egter nie noodwendig verteenwoordigend van sy/haar roetine reisgedrag nie en dat hierdie gedrag afhanklik is van demografiese faktore en die geslag van die bestuurder. Hierdie tesis bespreek die variasie in dag-tot-dag reisgedrag van ‘n residensiële gebied, Summer Greens, in Kaapstad (RSA) deur gebruik te maak van ‘n datastel wat onlangs saamgestel is (November/Desember 2006). Die data is ingesamel deur ‘n opname te doen van die nommerplate van alle uitgaande voertuie tussen 06:00 en 10:00, weeksdae van Maandag tot Vrydag, oor ‘n periode van vyf weke. A totale aantal voertuie van 5677 wat 44 743 ritte onderneem het, is waargeneem en ‘n analise is uitgevoer. Die navorsing herhaal en brei uit op vorige werk wat die dag-tot-dag variasie in ritopwekking bestudeer. Del Mistro en Behrens (2006) het data bestudeer wat ingesamel is in Julie/Augustus 2005 in Buitengrachtstraat, in die Kaapse Middestad (RSA). Die huidige navorsing brei uit op hierdie werk deur die variasie in vertrektyd in te sluit asook om waarnemings te doen tydens die skoolperiode (3 weke) en die daaropvolgende vakansieperiode (2 weke). ‘n Metode word ook aangebied om die dag-tot-dag variasie te meet deur middel van die beskikbare data wat ingesamel is. Hierdie tesis vind ‘n merkwaardige verskil in die skool en vakansie verkeersvolumes, soos verwag kan word, maar ten spyte daarvan bestaan daar sekere identiese reisgedragspatrone (byvoorbeeld die frekwensies waarteen ‘n voertuig voorkom, weeklikse herhaling van proporsies, ens.) gedurende beide hierdie periodes. Die bevinding is dat die spitsuur vir skool- en vakansieperiodes gedurende dieselfde tydsperiode plaasvind en dat verkeersvolumes groter variasie toon op Vrydae gedurende die vakansieperiode, as die skoolperiode. Dit wil blyk of verkeersvolumes gedurende al die weke afneem van Maandag tot Woensdag en dan “terug spring” op Donderdae en Vrydae. Hierdie bevinding is in ooreenstemming met resultate van ‘n ander internasionale studie. Motoriste het ‘n neiging getoon tot groter vryheid in terme van vertrektye tydens die vakansieperiode, met die gemiddelde vakansie vertrektye heelwat later as gedurende die skoolperiode. Vertrektye is ook gevind om geleidelik later te word van Maandag tot Vrydag gedurende beide die skool en vakansieperiodes, met Donderdag en Vrydag se vertrektye wat merkwaardig verskil van ander weeksdae. Die verhouding uniek waargenome voertuie het volgens hierdie navorsing se bevindinge toegeneem met die tyd van die dag en die gevolglike impak hiervan op die effektiwiteit van sogenaamde “Vehicle Message Sign” toepassings word bespreek. Die navorsing sluit dan af deur die bevindinge toe te pas om die impak te bepaal wat ‘n hipotetiese kongestieprysskema op verkeersvolumes het.