Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Connections are a vitally important part of any structural framework. Thisstatement may seem obvious, yet it is surprisinghow often insufficient attention is given to the design of this essential aspect of steelwork projects. This thesis concentrates on developing a specification for designing steel connections with the main emphasis on the practical and economical design of typical connections. The design methods of the specification are developed according to the new South African design code which is currently in draft form, namely SANS10162:Code of Practice for the Structural Use of Steel: Part 1: Limit States Design of hot-rolled steelwork - 2002. An object-oriented framework and associated graphical user interface for designing the connections are developed and implemented. The primary objectives of the implemented framework are: • Being generic in the sensethat it allows for easy addition of additional connection types, • To implement the design paradigm of the South African code, without fixing specific parameter values programmatically in the implementation and • To build on an existing architecture that allows for structural analysis,structural steel member design and distributed collaboration in the design process. / AFRIKAANSE OPSOMMING: Verbindings vorm In uiters belangrike deel van enige staal struktuur. Alhoewel hierdie stelling dalk vanselfsprekend mag wees, is dit egter verbasend hoe selde voldoende aandag aan die ontwerp van hierdie essensiëleaspek van staalwerk projekte gegee word. Hierdie tesis konsentreer op die ontwikkeling van In spesifikasievir die ontwerp van staal verbindings met die oog op praktiese en ekonomiese ontwerp van tipiese verbindings. Hierdie ontwerpmetodes isgebasseer op die nuwe Suid Afrikaanse ontwerpkode wat tans in proef-vorm is, naamlik SANS 10162: Gebruikskode vir Stoa/bouwerk: Dee/I: Grenstoestandontwerp vir warmgewa/ste staa/werk - 2002. In Objek orienteerde raamwerk en In geassosieerde grafiese gebruikerskoppelvlak word ontwikkel en geimplimenteer. Die primêre mikpunte van hierdie geimplimenteerde raamwerk is: • Om generies te wees in die sin dat dit die byvoeging van addisionele verbinding tipes toelaat, • Om die paradigma van die Suid Afrikaanse kode te implimenteer sonder om enige waardes van spesifieke parameters programmaties vas te lê, en • Om dit op In bestaande argitektuur te bou wat strukturele analise, strukturele ontwerp en verspreide samewerking in die ontwerpproses toelaat.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: South Africa, and other developing countries, experience great problems concerning road traffic accidents. Despite road safety campaigns like Arrive Alive being launched, accident rates do not decline significantly and the problem is predicted to get worse. This study is done on a road in the Western Cape, the R44, to investigate the causes of road accidents. The causes of the accidents are deduced from the accident reports and relationships are sought with other factors. The results of this study are risk factors (human-, environment- and vehicle factors) for the 14 accident types that occurred on the R44, as well as measures to prevent road accidents. It has been found that the human factor plays the biggest role in road accidents. Out of the 404 accidents analysed, 77.7% were caused by human factors, 8.7% by unknown factors, 7.2% by environmental factors and 6.4% by vehicle factors. The problems experienced with the data quality are reported and recommendations concerning it are made. / AFRIKAANSE OPSOMMING: Suid-Afrika en ander ontwikkelende lande ervaar groot probleme met verkeersongelukke. Ten spyte van veldtogte soos Arrive Alive wat geloods word, neem ongelukskoerse nie beduidend af nie, en daar word voorspel dat die situasie nie gaan verbeter nie. Hierdie studie is op 'n pad in die Wes-Kaap, die R44, gedoen om die oorsake van padongelukke vas te stel. Die oorsake van ongelukke i s van die ongeluksvorms a fgelei, en verwantskappe is gesoek met ander faktore. Die resultate van die studie is risikofaktore (menslike-, omgewings- en voertuigfaktore) vir die 14 ongelukstipes wat op die R44 voorgekom het, asook voorkomingsmaatreëls om padongelukke te voorkom. Daar is gevind dat die menslike faktor die grootste oorsaak van ongelukke is. Uit die 404 ongelukke wat geanaliseer is, is 77.7% van die ongelukke deur menslike faktore, 8.7% van die ongelukke deur onbekende faktore, 7.2% van die ongelukke deur omgewingsfaktore en 6.4% van die ongelukke deur voertuigfaktore veroorsaak. In hierdie studie is probleme ondervind met die datakwaliteit, en daaroor is verslag gedoen en aanbevelings gemaak.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This work investigates methods to theoretically determine the lateral velocity distribution across a river from which factors may be derived to translate a single point velocity into average velocity for the river as a whole. A wide range of field data from vanous nvers was analysed. This produced over a hundred velocity distributions with which to compare theoretical distribution results. Four theoretical approaches were considered: the one-dimensional method (Manning's equation), a two-dimensional flow formula solved as an initial-value-problem, a two dimensional flow formula solved as a boundary-value-problem and an empirical method developed from energy principles. The one-dimensional and initial-value-problem approaches were unsuccessful. The boundary-value and empirical approach did however produce promising results. Surprisingly the analysis of the field data revealed patterns of similarity which could produce accurate results without the need of a theoretical approach. / AFRIKAANSE OPSOMMING: Metodes word ondersoek om teoreties 'n laterale snelheidsverspreiding oor 'n rivier te bepaal en sodoende 'n faktor te vind waarmee 'n gemete enkelpuntsnelheid in die rivier omgeskakel kan word na 'n gemiddelde snelheid vir die rivier in geheel. Vloeimeetdata van verskeie nviere IS geanaliseer. Sodoende is meer as 100 snelheidsverspreidings gegenereer waarmee die teorie vergelyk kon word. Vier teoretiese benaderings is gevolg: Manning se een-dimensionele vloeivergelyking, 'n twee dimensionele vloei-vergelyking opgelos met behulp van 'n beginwaarde, 'n twee dimensionele vloei-vergelyking opgelos met behulp van randwaardes, en 'n empiriese metode ontwikkel vanuit energie beginsels. Die een-dimensionele- en beginwaarde-benaderings was me suksesvol me. Die randwaarde- en empiriese benaderings het wel belowende resultate gelewer. Selfs verwerking van die gemete stroommetings het waardevolle inligting gelewer: daar bestaan duidelike ooreenkomste in die snelheidsverspreidings wat gebruik kan word om die verspreidingsfaktor mee te bereken sonder om teoretiese oplossings te soek.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Up to this point in time research on the South African solar chimney, proposed for a site in the Northern Cape, comprised of determining the structural integrity of the chimney structure, as well as airflow calculation, finding the optimal shape for the airflow channels. Not much work had been done on the realisation of the foundation of the global structure, i.e. how the cardinal parts are optimized in an integrated system. The inlet guide vanes (IGV's) should be central in such research efforts, being the main support of gravitational and lateral wind load on the chimney structure, as well as its important role in channelling air and creating pre-swirl of the airflow onto the turbine blades. However, little detailed research - research to actually determine and fix the many variables of the IGV's and integration with surrounding parts - had been performed! In this thesis as many of these variables as possible are investigated - ranging from structural integrity with regard to compressive and shear strength through optimizing structure eigenfrequency to economic feasibility. The outcome of this study is conceptual solutions regarding the geometry of the IGV structures in order for it to support the chimney while minimizing material volume. Finite element methods are used to create insight into the behaviour of the IGV's and force transferring structures, incorporating external factors such as lateral wind and gravitational loadsto determine the optimal shape of these structures. This study is valuable for researchers on the solar chimney, serving as a reference from where to design and secure the variables of the global structure, and eventually building the solar chimney. Keywords: Solar chimney, inlet guide vanes, solar power, massive concrete structures, structural realisation, finite element application, structure optimisation. / AFRIKAANSE OPSOMMING: Tot op hede het die navorsing op die Suid Afrikaanse sonskoorsteen, wat beplan word vir konstruksie in die Noordkaap, bestaan uit die bepaling van die integriteit van die struktuur asook lugvloei berekeninge om die optimale vorm van die lugvloei kanale te lewer. Min werk is gedoen om die fondasies van die globale struktuur, dus hoe die kardinale dele geïntegreer is in die gesamentlike sisteem, te ondersoek. Die inlaat lei lemme behoort sentraal te lê in sulke navorsingspogings aangesien dit die hoof ondersteuner en verspreider van gravitasie en laterale windlaste op die skoorsteen struktuur is. Dit speelook 'n integrale rol in die kanalisering van invloeiende lug om dit vooraf 'n vorteks beweging te gee vir 'n optimale invalshoek op die turbine lemme. Min gedetaileerde navorsing - navorsing om die verskeie onbekende faktore rondom die inlaat lei lemme en die omliggende strukture te bepaal - is tot op hede gedoen. Hierdie tesis mik om soveel moontlik van hierdie veranderlikes - wat reik van struktuur integriteit met betrekking tot die samedrukkings- en skuifsterktes in die materiaal tot die eie-frekwensies en ekonomiese vatbaarheid van die struktuur - vas te stel. Die uitkoms van hierdie studie is konseptueie oplossings vir die geometrie van die inlaat lei lem strukture wat terselfdertyd die totale struktuur se materiaal volume minimiseer. Eindige element metodes word gebruik om insig in die gedrag van die inlaat lei lemme en ander strukture wat krag oordra, te genereer. Die metodes inkorporeer soveel as moontlik van die eksterne faktore soos gravitasie en laterale windlas om die optimale geometrie vir die betrokke struktuur te bepaal. Hierdie studie is waardevol vir navorsers oor die sonskoorsteen en dien as 'n bron waaruit verdere ontwerp en die vasstel van veranderlikes in die globale struktuur gedoen kan word met die oog op die uiteindelike daarstelling van 'n sonskoorsteen.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Presented here is an Eulerian scheme for solving the unsteady pipe-flow equations. It is called the Characteristic Dissipative Petrov-Galerkin finite element algorithm. It is based on Hicks and Steffler's open-channel finite element algorithm [5]. The algorithm features a highly selective dissipative interface, which damps out spurious oscillations in the pressure field while leaving the rest of the field almost unaffected. The dissipative interface is obtained through upwinding of the test shape functions, which is controlled by the characteristic directions of the flow field at a node. The algorithm can be applied to variable grids, since the dissipative interface is locally controlled. The algorithm was applied to waterhammer problems, which included reservoir, deadend, valve and pump boundary conditions. Satisfactory results were obtained using a simple one-dimensional element with linear shape functions. / AFRIKAANSE OPSOMMING: 'n Euleriese skema word hier beskryf om die onbestendige pypvloei differensiaal vergelykings op te los. Dit word die Karakteristieke Dissiperende Petrov-Galerkin eindige element algoritme genoem. Die algoritme is gebaseer op Hicks en Steffler se oop-kanaal eindige element algoritme [5]. In hierdie algoritme word onrealistiese ossilasies in die drukveld selektief gedissipeer, sonder om die res van die veld te beinvloed. Die dissiperende koppelvlak word verkry deur stroomop weegfunksies, wat beheer word deur die karakteristieke rigtings in die vloeiveld, by 'n node. Die algoritme kan dus gebruik word op veranderbare roosters, omdat die dissiperende koppelvlak lokaal beheer word. Die algoritme was toegepas op waterslag probleme waarvan die grenskondisies reservoirs, entpunte, kleppe en pompe ingesluit het. Bevredigende resultate was verkry vir hierdie probleme, al was die geimplementeerde element een-dimensioneel met lineere vormfunksies.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: This study sets out to describe the incipient motion process in cobble/boulder bed rivers in terms of the unit applied power approach. This objective has been met through the collection of data on stone movement from a total of thirteen flood events observed in two undisturbed rivers in the Western Cape, namely the Molenaars and Berg Rivers. The data were plotted on the original modified Liu diagram for incipient motion and it was found that the threshold of movement for the smaller stones did not conform with the portion of the Liu diagram which represents fully turbulent flow (i.e. where ~ gDs tv: = 0.12 for Re. >13). It was concluded that the only reason that could explain this deviation is the fact that the original modified Liu diagram had been derived for uniform particle size beds while the data of the Molenaars and Berg Rivers represent non-uniform particle size beds. This was proved through re-deriving the y-axis function of the original modified Liu diagram to include a factor that makes provision for the roughness of a non-uniform particle size bed. It was found that the average absolute roughness of the non-uniform particle size beds in the Molenaars and Berg Rivers is reasonably well approximated by a value of k=da. Design curves (in terms of the original modified Liu diagram parameters) for intensity of motion were also produced. Although it is not possible to read off accurate percentages of movement values directly from these curves, it should be possible to deduce reasonably accurate values in practical situations. / AFRIKAANSE OPSOMMING: Die studie poog om die begin van beweging proses in klip/rotsbed riviere te beskryf in terme van die eenheids aangewende drywing metode. Hierdie doel is bereik deur die insameling van klipbewegingdata in 'n totaal van dertien vloedgebeurtenisse in twee ongerepte riviere in die Wes-Kaap, naamlik die Molenaars en Bergriviere. Die data was geplot op die oorspronklike aangepaste Liu diagram vir begin van beweging en dit was gevind dat die grens van beweging vir die kleiner klippe nie ooreenstem met die gedeelte van die Liu diagram wat volle turbulente vloei verteenwoordig nie (waar ~ gDs tv; = 0.12 vir Re. >13). Daar was tot die gevolgtrekking gekom dat die enigste rede wat die afwyking kan beskryf is die feit dat die oorspronklike aangepaste Liu diagram afgelei was vir uniforme partikelgrootte beddens terwyl die data van die Molenaars and Bergriviere nie-uniforme partikelgrootte beddens verteenwoordig. Dit was bewys deur die heratleiding van die y-as funksie van die oorspronklike aangepaste Liu diagram om 'n faktor in te sluit wat voorsiening maak vir die ruheid van 'n nie-uniforme partikelgrootte bed. Dit was gevind dat die gemiddelde absolute ruheid van die nieuniforme partikelgrootte beddens in die Molenaars en Bergriviere word redelik goed benaderd met 'n waarde van k=ds4• Ontwerpkurwes (in terme van die oorspronklike aangepaste Liu diagram parameters) vir intensiteit van beweging was ook ontwikkel. Alhoewel dit nie moontlik is om baie akkurate persentasies van beweging af te lees van die kurwes nie, is dit moontlik om akkuraat genoeg waardes te verkry in praktiese situasies.

Thesis (MscEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The environmental impacts of manmade changes to rivers are, in modern days, extremely important. The impact needs to be quantified in order to predict future happenings and to assist in determining preventative measures. Dam construction forms an essential part of modern life to provide the necessary water demand for the ever increasing population. One manmade change that has a major impact on rivers is large dam developments in the upper reaches of rivers. These developments normally have the following effects on the lower reaches of the river due to the change in flow regime: • Narrower main channel, • Deeper main channel, • Reduced sediment transport, • Changes in sediment erosion and deposition patterns, • Less frequent flood plain inundation, • Overgrown flood plains, • Changes in ecological and biological parameters. All the above mentioned factors play an important part in the stability of the ecological and biological parameters. Prior to construction of a dam, however, the baseline ecological, physical Ichemical, hydrological, hydraulic and social conditions of the river system, including its associated groundwater, estuarine and floodplain components, would need to be established, to allow clear identification of future changes as a result of implementation of the instream flow requirements (lFR), as well as to guide the post-construction monitoring programme itself. The discharge and sediment transport changes that might occur as a result of the Berg River Dam development was thoroughly investigated in this reseach. The physical processes and mathematical modelling that formed part of this investigation are discussed in this thesis. The mathematical modelling was carried out using MIKE 11, software developed by the Danish Hydraulic Institute for Water and Environment. This program was developed especially for one dimensional modelling of hydrodynamics and sediment transport within a river system. The results obtained from the simulations were used to calculate a hydrodynamic and sediment mass balance for both the pre and post dam scenarios in the Berg River, Western Cape. The influence of artificial flood releases from the Berg River Dam which is currently under construction was also investigated. Most of the data needed for the calibration and verification of the mathematical model was obtained from field work. Suspended and bed load sediment samples were taken in order to aid in the calibration of the sediment transport model. The bed roughness coefficients of the various sections of the river were calibrated against actual recorded water levels measured during flood events that occurred in 2003 and 2004. An intensive study of the incipient motion of cobbles and boulders in the upper reaches of the Berg River was carried out. Unfortunately it has to be stated that the transport of cobbles and boulders cannot be simulated by most computer programs as almost all the transport models available are only defined up to a maximum diameter of 20mm. The lack of consistent sediment load data as well as the low rainfall during 2003 and 2004 presented problems during the calibration of the sediment transport model; it is therefore recommended that sediment load sampling is continued for at least two years in order to verify the calculated sediment yield for the various catchments. From this study it can be concluded that the Berg River Dam will have a significant effect on the downstream river morphology of the first 70 kilometres of the river. Thereafter the effect will decrease to a minimum. The proposed artifical flood releases are effective in reinstating the river to its present state. This study also showed that a fully hydrodynamic model of a large river system such as the Berg River can be calibrated and validated. / AFRIKAANSE OPSOMMING: Die omgewingsimpak van mensgemaakte veranderinge in natuurlike riviere raak meer en meer belangrik. Hierdie impak moet gekwantifiseer word om sodoende toekomstige gebeurtenisse te verstaan en om die nodige voorkomingsmaatreëls in werking te stel. Om aan die waterbehoefte te voldoen vorm damkonstruksie 'n belangrike deel van die hedendaagse samelewing. Damme is moontlik een van die veranderinge aan die ewewig van riviere wat die grootste impak op die stroomaf dele van die rivier het. Die volgende veranderinge ten opsigte van die hoofkanaal word meestalopgemerk na die konstrukie van 'n dam in die hoërliggende dele van riviere: • Nouer hoofkanaal, • Dieper hoofkanaal, • Afname in die volume sediment wat vervoer word, • Veranderinge ten opsigte van die erosiepatrone, • Vloedvlaktes word minder oorstroom, • Toegegroeide vloedvlaktes, • Veranderings aan die ekologiese en biologiese parameters. Die bogenoemde faktore speel 'n belangrike rol ten opsigte van die stabiliteit van die ekologiese en biologiese veranderlikes. Alvorens die konstruksie begin moet die natuurlike ewewigstoestand van die rivier ten opsigte van die ekologiese, fisiese, chemiese, hidrologiese, hidrouliese, en sosiale faktore gemeet word. Dit moet gedoen word om sodoende toekomstige veranderinge wat moontlik mag plaasvind as gevolg van die damkonstruksie en die omgewingsloslatings te kwantifiseer. Hierdie metings word ook gebruik om die na - konstruksie monitering te evalueer. Die veranderinge ten opsigte van vloei en sedimentvervoer wat moontlik mag plaasvind as gevolg van die Berg Rivier Dam konstruksie is noukeuring ondersoek. Die fisiese prosesse as ook die wiskundige modelle wat gedurende hierdie studie aangewend is word in hierdie tesis bespreek. Al die wiskundige modellering is met MIKE 11 wat deur die Deense Instituut vir Water en Omgewing ontwikkel is, uitgevoer. Hierdie sagteware is spesifiek vir die een dimensionele simulasie van hidrodinamika en sediment vervoer van riviere ontwikkel. Die resultate wat verkry is, is gebruik om 'n hidrodinamiese en sedimentvervoer massabalans vir beide die voor - en na - dam toestande op te stel. Die effek van beheerde, kunsmatige vloede is ook ondersoek. Die meeste van die data wat benodig word om die wiskundige model the kalibreer is verkry deur fisiese veldwerk te doen. Sediment monsters is geneem gedurende die winter seisoen van 2003 en 2004. Hierdie data is gebruik om die sediment vervoer model te kalibreer. Die bodemruheid van die verskillende dele van die rivier is gekalibreer teen gemete vloedhoogtes tydens 2003 en 2004. 'n Deeglik studie van die begin van beweging van die groter partikels wat in die bolope van die Berg rivier aangetref word is uitgevoer. Ongelukkig moet dit genoem word dat hierdie een van die groot tekortkominge is van die model aangesien dit nie in die sedimentvervoer model ingekorporeer kan word nie omdat die meeste van die sedimentteorieë wat tans beskikbaar is net gedefinieer is tot 'n partikel groote van 20 mm. Die tekort aan deurlopende sediment lading data as ook die lae reënval gedurende 2003 en 2004 het probleme veroorsaak tydens die kalibrasie van die sedimentvervoer model. As gevolg hiervan word daar aanbeveel dat die insameling van sedimentdata vir ten minste nog twee jaar volgehou word ten einde die beskikbaarheid van sediment in die verskeie opvanggebiede deeglik na te gaan. Uit hierdie studie kan afgelei word dat die Berg rivier dam 'n beduidende effek op die morfologie van die eeste 70 kilometer van die Berg Rivier sal hê. Verder stoomaf sal die effek minder sigbaar wees. The beheerde kunsmatige vloedloslatings speel 'n beduidende rol in die normalisering van die sedimentvervoer van die Berg rivier. Hierdie studie toon dat 'n volledige hidrodinamiese model van 'n groot rivierstelsel gekalibreer kan word.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The study reported in this thesis focuses on the development of algorithms that can be used to schedule routine maintenance work in maintenance wards of a gravel road network, This was undertaken as part of the development of the Blading Optimisation Module of the Gravel Management System of the Provincial Government: Western Cape. Two scheduling algorithms were developed and mapped to a pilot object model on the computer. The algorithms and application interface takes account of the constraints and variables of routine maintenance that were identified through interviews with personnel of the five District Municipalities contained in the Western Cape. The algorithms are tested and evaluated using the pilot application. Based on the evaluation of the algorithms conclusions are drawn and recommendations are made. / AFRIKAANSE OPSOMMING: Die studie beskryf in hierdie tesis fokus op die ontwikkeling van algoritmes vir die skedulering van roetine instandhoudingswerk in instandhoudingswyke van 'n gruispadnetwerk. Dit is ondemeem tydens die ontwikkeling van die "Blading Optimisation Module" van die "Gravel Management System" van die Provinsiale Regering: Wes Kaap. Twee algoritmes is ontwikkel en afgebeeld op 'n loods-objekmodel op die rekenaar. Die algoritmes en toepassingskoppelvlak maak voorsiening vir die beperkings en veranderlikes wat geidentifiseer is tydens onderhoude met personeel van die distrikmunisipaliteite in die Wes Kaap. Die algoritmes is getoets en geevalueer met behulp van die loodstoepassing. Gevolgtrekkings en aanbevelings word gemaak op grond van die resultate van die evaluasie van die algoritmes.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Accelerated pavement testing (APT) is the application of a wheel loading, to a prototype or actual layered, structural pavement system to determine pavement response and performance under controlled, accelerated accumulation of damage in a compressed time period. It is a tool used for the evaluation of performance of new pavement materials, distress mechanisms, pavement distress, and selection of rehabilitation strategies. In this study, the research work that was done in Jacksboro, Texas (USA) with the third-scale Model Mobile Load Simulator (MMLS3) as part of the APT programme of the Texas Department of Transportation (TxDOT) is presented. The primary objective was to evaluate the performance ofthe different asphalt concrete (AC) materials (Dustrol and Remixer) used on highway US 281, in terms of rutting and distress due to wet trafficking. The other objective was to investigate the difference in rutting between the MMLS3 and the full-scale Texas Mobile Load Simulator (TxMLS). The scope of the study included fieldwork, laboratory work and theoretical analysis. On average, the performance of the layer from the Dustrol process was found to be poorer than that of the Remixer process. The Dustrol process was more susceptible to moisture damage and less resistant to permanent deformation compared to the Remixer process. The MMLS3 and TxMLS permanent deformations in the upper 90 mm surface layers correlated well in terms of the respective vertical stresses imposed by the two APT devices, after allowing for the difference in environmental conditions during trafficking. Overall, the study demonstrated that the MMLS3, used in conjunction with nondestructive field and laboratory testing, is a significant cost-effective APT device that can be used for evaluating the response and performance of the (surface) layers of full-scale, in-service pavements. / AFRIKAANSE OPSOMMING: Versnelde Plaveisel Toetsing bestaan uit die gebruik van 'n wiellas op 'n prototipe of 'n bestaande gelaagde plaveiselstruktuur om die plaveiselgedrag onder beheerde en versnelde toename in skade in 'n verkorte periode te bepaal. Dit word gebruik om die gedrag van nuwe plaveiselmateriale, swigtingsmeganismes, plaveiselswigting en die keuse van rehabilitasie strategieë te evalueer. Die navorsingswerk met die derde skaal Model Mobile Load Simulator (MMLS3) wat onderneem is in Jacksboro, Texas (VSA), en deel uitmaak van die Versnelde Plaveisel Toetsingsprojek van die Texas Departement van Vervoer (TxDOT), word uiteengesit. Die hoofdoel van die studie was om die gedrag van twee verskillende asfaltmateriale, naamlik Dustrol en Remixer, wat gebruik is op die US 281-snelweg, in terme van sporing en swigting as gevolg van nat belastingstoestande te evalueer. 'n Verdere doelstelling was om die verskil in die gemete sporing tussen die MMLS3 en die volskaal Texas Mobile Load Simulator (TxMLS) te ondersoek. Die studie het veld- en laboratoriumtoetse en teoretiese analise behels. Die gedrag van die Dustrol laag is oor die algemeen swakker as die Remixer lae. Die Dustrol laag, in vergelyking met die Remixer lae, is meer vatbaar vir vogskade en spoor makliker. Nadat die invloed van verskillende omgewingstoestande gedurende asbelasting inaggeneem is, korreleer die sporing vir die MMLS3 en die TxMLS in die lae van die boonste 90mm van die plaveisel goed in terme van die vertikale spannings soos opgewek deur die twee toetstoestelle. In die geheel word bewys dat die MMLS3 tesame met nie-destruktiewe veld- en laboratoriumtoetse 'n belangrike koste-effektiewe versnelde plaveisel toetstoestel is, wat aangewend kan word in die evaluasieproses van die gedrag van (oppervlak) lae van volskaalse plaveisels in gebruik.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The intent of this thesis is to examine the solving of problems with neural networks. Three cases are investigated: the calculation of a Visual Condition Index (VCI), the determination ofthe reseal need, and the back-calculation of E-moduli from measured deflection basins. The calculation of a Visual Condition Index (VCI) is a very good example of how a neural network can be applied to reach a conclusion through the association of a number of facts with one single outcome. VISual assessments of the road condition are done on a yearly basis and the Assessor gives his impression of the condition of a road. A neural network simulates the association between the inputs of elements of distress on the road and the eventual assessment of the overall condition expressed as the VCI, very well. Reseal need is determined by the Provincial Administration: Western Cape (PAWC) with a Reseal Expert System. Data produced by the expert system was used to train a neural network to determine the reseal need. The strength of using these two methods in combination is shown. Meaningful results could not be obtained due to insufficient data in certain categories. Deflection measurements with a Falling Weight Deflectometer are meaningful indicators of pavement strength. Back-calculation is used to calculate E-moduli of pavement layers which can be used in a mechanistic approach to estimate remaining pavement life from pavement response. Conventional backcalculation programs, when implemented in a pavement management system, result in very long computing times due to the large volumes of data available. Neural networks offer the alternative of very fast processing, making the implementation of back-calculation in real-time possible. It is shown that neural networks can back-calculate E-moduli, but with varying degrees of success. The main problem identified is the basis on which the dataset used to train neural networks, is generated using linear elastic theory. The biggest limitation in the linear elastic theory is that non-linear and stress dependent behaviour of materials cannot be simulated, two aspects that have a major influence on the back-calculated E-moduli. Improvements in the data generation process using a theory that accommodates non-linear and stress dependent behaviour of materials may result in improved performance of the neural networks. It is also shown that it is very difficult to design a single neural network that can be successfully used on all the possible pavement types. It is better to identify representative pavement types and train neural networks for each of these. Neural networks can be applied with success in the pavement management field and the combination of Expert Systems, Neural Networks and Fuzzy Logic can be a very powerful method to solve complicated problems. Care should be taken in the design of the neural networks and a good understanding ofthe data is a prerequisite for success. / AFRIKAANSE OPSOMMING: Die bedoeling met die tesis is om die vermoë van neurale netwerke om probleme op te los, te ondersoek. Drie gevalle word beskou: die berekening van 'n Visuele Toestand Indeks (VTI), die bepaling van die herseël behoefte en die terugberekening van die E-moduli vanaf defleksie metings. Die berekening van die VTI demonstreer die vermoë van neurale netwerke om,deur middel van die assosiasie tussen 'n hele aantal veranderlikes tot 'n enkele uitkoms, tot 'n gevolgtrekking te kom. Visuele opnames van paaie word op 'n jaarlikse basis gedoen waar die opnemer sy indrukke gee van die toestand van die pad. In Neurale netwerk simuleer die assosiasie tussen die insette (waargenome gebreke) en die uiteindelike toestands beskrywing van die pad, uitgedruk as die VTI, baie goed. Die Provinsiale Administrase: Wes-Kaap bepaal die jaarlikse herseëlbehoefte met behulp van 'n Herseël Ekspertstelsel. Die uitsette van hierdie stelsel is gebruik om 'n neurale netwerk op te lei om die herseëlbehoefte te bepaal. Die voordele om die twee stelsels saam aan te wend, word getoon. Betekenisvolle resultate kom nie bekom word nie vanweë onvoldoende inligting in sekere kategorieë. Defleksiemetings deur 'n vallende-gewig meetapparaat is betekenisvolle indikators van die plaveiselsterkte. Die E-moduli van die plaveisellae word bepaal deur terugberekenings vanaf defleksiemetings. Hierdie Emoduli kan gebruik word om met behulp van meganistiese metodes die oorblywende leeftyd van 'n plaveisel te bepaal. Konvensionele terugberekenings programme, geïmplementeer in In plaveiselbestuurstelsel, neem lank om die groot hoeveelheid defleksiemetings te verwerk. Neurale netwerke bied die alternatief van die intydse berekening van E-moduli vanweë die besonder hoë berekeningspoed wat behaal word. In hierdie tesis word aangetoon dat neurale netwerke aangewend kan word om die terugberekenigs te doen, maar met 'n wisselende mate van sukses. Die gebruik van die lineêre elastiese teorie om die data vir die neurale netwerke te genereer, word as 'n probleem geïdentifiseer. Die grootste tekortkoming wat met die lineêre elastiese teorie ondervind word is dat dit nie die nie-lineêre en spanningsafhanklike gedrag van materiale voldoende simuleer nie. Beide hierdie twee aspekte het 'n groot invloed op die akkuraatheid van terugberekende E-moduli. Verbeteringe in die generering van data deur 'n teorie te gebruik wat nie-lineêre en spanningsafhanklike gedrag van materiale behoorlik simuleer, mag lei tot 'n beter prestasie van die neurale netwerke. Dit word ook getoon dat dit moeilik is om 'n enkele neurale netwerk te ontwerp wat suksesvol gebruik kan word op alle plaveiseltipes. Dit is beter om verteenwoordigende plaveiseltipes te identifiseer en dan neurale netwerke vir elkeen te ontwerp. Neurale netwerke kan met sukses in die plaveiselbestuur veld toegepas word en die kombinasie van ekspertsteiseis, neurale netwerke en vaagheidstelsels (fuzzy) kan tot kragtige metodes lei om komplekse probleme op te los. Sorg moet aan die dag gelê word met die ontwerp van neurale netwerke en 'n goeie begrip van die data is 'n voorvereiste vir sukses.