Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Precast concrete has been used for decades in the construction industry, locally as well as internationally. Rapid urban development and the need for shorter construction periods for building and infrastructure projects have however encouraged more use of precast concrete construction. The improved speed of construction, high quality and less labour requirements that precast offers makes it an effective type of construction method for modern development. The utilization of various precast concrete systems has been frequently used in the international construction industry, making it a very popular construction method. It was however found that one of the major drawbacks or concerns with the use of precast concrete is the connections between the precast elements. In-situ construction does not have this problem, because it is designed to a monolithic structure or building. It was identified that if the connections in precast buildings or structures are designed or constructed in an insufficient way, it can lead to severe structural problems and even failure. This highlights the importance the design and construction of precast concrete connections have on the overall stability, strength and robustness of the structure. Precast concrete buildings are not merely separate precast elements, connected together to eventually form the same principals of in-situ construction. Precast concrete and connection design is considered to be a specialist field and requires the sufficient expertise and knowledge to understand the structural system and all its different aspects. The precast connection’s function is not merely to transfer loads, but also to develop continuity and ensure monolithic behaviour of the entire precast concrete structure (Englekirk 2003). The most important or desirable structural functions of precast connections are; (i) direct transfer of loads (load paths and flow or forces), (ii) develop structural continuity and integrity, (iii) distribution of concentrated loads, (iv) allow for movements and unintended restraints and lastly to (v) ensure efficient rigidity and robustness for the connection. It can be seen that there is many factors that contribute to the overall design and construction phases of precast concrete connections. The aim of this study is to identify and investigate aspects that influence the design and construction of precast concrete connections. This study will mainly focus on precast concrete and precast connection preferences of participants in the South African construction industry. During this study, industry participants (contractors and consultants) were asked to identify certain aspects and concerns associated with precast concrete and precast connection construction. These answers were used to develop guidelines and preferences that can be used by industry participants to improvise and effectively manage the precast construction, mainly focussing on the connections between the precast elements. / AFRIKAANSE OPSOMMING: Voorafvervaardigde beton word al vir dekades gebruik in die konstruksiebedryf, plaaslik sowel as internasionaal. Vinnige stedelike ontwikkeling en die behoefte vir korter konstruksie tydperke vir die struktuur en infrastruktuur projekte het egter die gebruik en implementasie van voorafvervaardigde beton konstruksie laat toeneem. Die verbeterde spoed van die konstruksie proses, 'n hoë gehalte produk en minder arbeid vereistes wat voorafvervaardiging bied maak dit dus 'n effektiewe tipe konstruksie metode vir moderne ontwikkelings. Die benutting van verskeie voorafvervaardigde beton sisteme en elemente word reeds herhaaldelik gebruik in die internasionale konstruksiebedryf, wat dit vervolglik ʼn baie populêre en effektiewe sisteem maak. Dit is egter bevind dat een van die groot struikelblokke of probleme met die gebruik van voorafvervaardigde beton is die verbindings tussen die voorafvervaardigde elemente. In-situ beton konstruksie het dus nie hierdie probleem nie, want dit word ontwerp om 'n monolitiese beton struktuur of gebou te vorm. Dit was immers geïdentifiseer dat as die verbindings in ʼn voorafvervaardigde gebou of struktuur, ontwerp word deur ʼn ontoereikende manier, dit kan lei tot ernstige strukturele probleme en selfs strukturele faling. Dit beklemtoon dus die belangrikheid wat die ontwerp en konstruksie proses van voorafvervaardigde beton verbindings het op die algehele stabiliteit, sterkte en robuustheid van die struktuur. Voorafvervaardigde beton geboue en strukture kan nie slegs beskou word as aparte voorafvervaardigde elemente wat met mekaar verbind word om eventueel dieselfde beginsels van insitu konstruksie te vorm nie. Voorafvervaardigde beton en verbinding ontwerp word beskou as 'n spesialis veld en vereis dat die ontwerper die nodige kundigheid en kennis van die strukturele stelsel en al sy verskillende aspekte verstaan. Voorafvervaardigde beton verbindings se funksie is nie net om toegepaste kragte oor te dra nie, maar ook om strukturele kontinuïteit te ontwikkel en te verseker dat monolitiese gedrag gehandhaaf word vir die hele voorafvervaardigde beton struktuur (Englekirk 2003). Die mees belangrike strukturele funksies van voorafvervaardigde beton verbindings sluit die volgende in; (i) verseker direkte oordrag van toegepaste kragte (vloei van kragte), (ii) ontwikkeling van strukturele kontinuïteit en integriteit, (iii) die verspreiding van puntbelastings, (iv) moet voorsiening maak vir die bewegings in die voorafvervaardigde element en konneksie self en laastens (v) verskaf doeltreffende rigiditeit en robuustheid vir die konneksie sone. Dus kan daar afgelei word dat daar baie faktore is wat bydra tot die algehele ontwerp en konstruksie fases van voorafvervaardigde beton verbindings. Die doel van hierdie studie is om aspekte te identifiseer en te ondersoek wat die ontwerp en konstruksie van aspekte beton verbindings wel beïnvloed. Die studie sal hoofsaaklik fokus op voorafvervaardigde beton en verbindings voorkeure van persone in die Suid-Afrikaanse konstruksiebedryf. Tydens die studie was persone in die industrie (kontrakteurs en konsultante) ook gevra om sekere aspekte en kwellings wat verband hou met voorafvervaardigde beton asook die verbindings te identifiseer. Die antwoorde wat verkry was uit die industrie deelnemers kan toepaslik gebruik om word riglyne en voorkeure op te stel wat vervolglik gebruik en toegepas kan word in die konstruksie bedryf van Suid Afrika. Die riglyne kan effektief gebruik word om voorafvervaardigde beton asook die verbindings te verbeter en persone in die konstruksie bedryf in te lig oor voorkeure en toepassings van hierdie metode.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Tropical cyclones are synoptic scale rotating storms capable of generating intense wind speeds and rainfall with potentially devastating social and economic consequences. In addition to abnormally high winds and rainfall, the associated storm surge and extreme waves can lead to severe coastal erosion, damage to coastal property and inundation. A good understanding of the risk exposure to these events is therefore of great importance to planners and designers of coastal infrastructure in vulnerable regions. Probabilistic approaches have been routinely adopted for the calculation of extreme tropical cyclone induced wind speeds, with significant developments in these techniques over the last few decades. While the application of these approaches has become widely adopted in regions such as the North Atlantic, North Pacific and South Pacific Oceans, relatively little attention has been paid to the South-West Indian Ocean. This thesis focusses on the quantification of the risk exposure to tropical cyclones over the South-West Indian Ocean, using current state-of-the-art techniques. The primary results of the thesis are extreme wind speed maps at various return periods of interest for engineering design. Best track data for the South-West Indian Ocean, as archived by the Joint Typhoon Warning Centre (JTWC), has been used as the primary dataset forming the basis of this study. These data provide estimates of the location and intensity of historical tropical cyclones at six hourly intervals. Location data are provided as estimates of longitude and latitude of the eye, while intensity data are provided as estimates of the maximum sustained surface (10 m elevation) wind speed and/or minimum central pressure. The modelling of tropical cyclone wind fields has been carried out using both the Holland (1980) and the Willoughby et al. (2006) parametric wind field models. Using the limited information available in the best track data as input to the model, surface wind fields which reasonably resemble those of actual storms have been generated. Both considered parametric wind field models have been shown to yield reasonable wind speeds and directions when compared with measurements. Of the two considered models the Willoughby et al. (2006) model has been shown to provide the best fit to historical wind speed measurements. Extreme value analyses of tropical cyclone induced wind speeds based on historical data alone have been shown to lead to potentially large errors, owing to the small sample size of the historical data. This highlights the need to augment the historical database through a probabilistic approach. Largely following the methods described in Powel et al. (2005) and Emanuel et al. (2006), a synthetic track model for the South-West Indian Ocean has been developed. The objective of the synthetic track model is to simulate thousands of years of tropical cyclone tracks, thereby circumventing errors induced by small sample sizes in the available historical best track data. The synthetic track model developed as part of this study is a Markov chain model, capable of simulating track propagation and intensity evolution along the track, from track genesis through to termination. The model is purely statistical, based on properties derived from the historical best track data. Adjustments have however been made to account for physical limitations such as those imposed by the equator and the maximum potential intensity which an event can attain. The statistical characteristics of synthetic tracks have been shown to agree well with those of the historical population. Applying the Willoughby et al. (2006) wind field model along synthetic tracks has enabled the simulation of 5 000 years of tropical cyclone induced wind speeds at any location of interest in the South-West Indian Ocean. Applying calculations on a 1 degree geographical grid, wind speed maps corresponding to return periods of 50, 100, 200 and 500 years have been generated for the South-West Indian Ocean. Extreme wind speeds along coastal regions provide valuable input for the design of coastal infrastructure in the region. / AFRIKAANSE OPSOMMING: Tropiese siklone is sinoptiese orde roterende storms wat in staat is om aansienlike windspoed en reënval, tot gevolg te hê met potensiële vernietigende sosiale en ekonomiese gevolge. Benewens die abnormale sterk winde en hoë reënval kan die verwante stormdeinings en vloedgolwe lei tot ernstige kus-erosie, skade aan kusfront-eiendom en oorstromings. ‘n Goeie begrip van die risiko-blootstelling aan hierdie gebeurtenisse is daarom van groot belang vir die beplanners en ontwerpers van kus-infrastruktuur in kwesbare gebiede. As gevolg van die beduidende ontwikkeling van probabilistiese benadering tot die berekening van windspoed wat veroorsaak word deur ekstreme tropiese siklone, word hierdie tegnieke huidiglike op ‘n roetine basis aangewend. Terwyl die toepassing van hierdie benaderings wyd aanvaar word in gebiede soos die Noord-Atlantiese, Noordelike- en Suidelike Stille Oseaan, word relatief min aandag gegee aan die Suid-Westelike Indiese Oseaan. Hierdie tesis fokus op die kwantifisering van die risiko-blootstelling aan tropiese siklone in die Suid-Westelike Indiese Oseaan met die gebruik van die huidige gevorderdste tegnieke. Die primêre resultaat van die tesis is uiterste wind spoed kaarte vir ‘n verskeindenheid herhaal periodes wat van belang in vir engenieursontwerp. Beste roete-ata vir die Suid-Westelike Indiese Oseaan, soos voorsien deur die Gesametlike Tifoon Waarskuwing Sentrum (JTWC), is gebruik as die primêre data stel wat die basis vorm van hierdie studie. Hierdie data gee die beste skattings van die ligging (lengte- en breedtegraad), en intensiteit (maksimum volgehoue oppervlak (10m hoogte) wind spoed en/of sentrale druk tekort) van historiese tropiese siklone teen ses-uurlikse intervalle. Die modelering van tropiese sikloon windvelde was uitgevoer met die gebruik van die Holland (1980) en die Willoughby et al. (2006) parametriese windveldmodelle. Met die gebruik van beperkte inligting wat beskikbaar is in die beste roete data as invoer vir die model, was oppervlak wind velde gegenereer wat ‘n billike ooreenstemming het met die van werklike storms. Beide tegnieke se parametriese windveldmodelle is al bewys om redelike akkurate windspoed en windrigtings te lewer in vergelyking met waargenome waardes. Van die twee modelle het die Willoughby et al. (2006) model se resultate die beste ooreenstemming gewys met historiese wind spoed metings. Dit is al uitgewys dat uiterste waarde-analises van tropiese sikloon veroorsaakte windspoed moontlik kan lei tot groot foute in die resultate as gevolg van die klein monster-grootte van die historiese data. Dit beklemtoon die noodsaaklikheid om die historiese databasis aan te vul met behulp van probabilistiese metodes. Die metodes soos beskryf deur Powel et al. (2005) en Emanuel et al. (2006) is hoofsaaklik gebruik om ‘n sintetiese roete-model vir die Suid-Westelike Oseaan te ontwikkel. Die doelwit van die sintetiese roete model is om duisende jare se tropiese sikloonroetes te produseer, en in effek foute te vermy as gevolg van die gebruik van klein monster groottes van die beskikbare historiese beste roete data. Die sintetiese roete model wat tydens hierdie studie ontwikkel is, is ‘n Markov kettingmodel wat in staat is om die roete verspreiding asook die evolusie van intensiteit saam die roete te simuleer vanaf die onstaan tot die beëindiging van die sikloon se roete. Die model is suiwer statisties en is gebasseer op die eienskappe soos afgelei vanaf die historiese beste roete data. Aanpassings is gemaak om rekening te hou van die fisiese beperkings soos die wat opgelê word deur die ewenaar en die maksimum potensiële intensiteit wat ‘n sikloon kan bereik. Dit is voorgelê dat die statistiese einskappe van die sintetiese roetes goed saamstem met die van die historiese populasie. Die toepassing van die Willoughby et al. (2006) wind veld model langs die sintetiese roetes het dit moontlik gemaak om 5000 jaar se windspoed, wat veroorsaak is deur tropiese siklone, te genereer by enige ligging wat van belang is in die Suid-Westelike Indiese Oseaan. Met berekeninge wat op ‘n 1 grade geografiese ruitnet gedoen is, is windspoedkaarte vir herhaal periodes van 50, 100, 200 en 500 jaar opgestel vir die Suid-Westelike Indiese Oseaan. Die uiterste wind spoed in kusgebiede gee waardevolle invoer vir die ontwerp van kus-infrastruktuur in die omgewing.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In this thesis we set out to design an algorithm for solving the all-pairs fixed-radius nearest neighbours search problem for a massively parallel heterogeneous system. The all-pairs search problem is stated as follows: Given a set of N points in d-dimensional space, find all pairs of points within a horizon distance of one another. This search is required by any nonlocal or meshless numerical modelling method to construct the neighbour list of each mesh point in the problem domain. Therefore, this work is applicable to a wide variety of fields, ranging from molecular dynamics to pattern recognition and geographical information systems. Here we focus on nonlocal solid mechanics methods. The basic method of solving the all-pairs search is to calculate, for each mesh point, the distance to each other mesh point and compare with the horizon value to determine if the points are neighbours. This can be a very computationally intensive procedure, especially if the neighbourhood needs to be updated at every time step to account for changes in material configuration. The problem also becomes more complex if the analysis is done in parallel. Furthermore, GPU computing has become very popular in the last decade. Most of the fastest supercomputers in the world today employ GPU processors as accelerators to CPU processors. It is also believed that the next-generation exascale supercomputers will be heterogeneous. Therefore the focus is on how to develop a neighbour searching algorithm that will take advantage of next-generation hardware. In this thesis we propose a CPU - multi GPU algorithm, which is an extension of the fixed-grid method, for the fixed-radius nearest neighbours search on massively parallel systems. / AFRIKAANSE OPSOMMING: In hierdie tesis het ons die ontwerp van ’n algoritme vir die oplossing van die alle-pare vaste-radius naaste bure soektog probleem vir groot skaal parallele heterogene stelsels aangepak. Die alle-pare soektog probleem is as volg gestel: Gegewe ’n stel van N punte in d-dimensionele ruimte, vind al die pare van punte wat binne ’n horison afstand van mekaar af is. Die soektog word deur enige nie-lokale of roosterlose numeriese metode benodig om die bure-lys van alle rooster-punte in die probleem te kry. Daarom is hierdie werk van toepassing op ’n wye verskeidenheid van velde, wat wissel van molekulêre dinamika tot patroon herkenning en geografiese inligtingstelsels. Hier is ons fokus op nie-lokale soliede meganika metodes. Die basiese metode vir die oplossing van die alle-pare soektog is om vir elke rooster-punt, die afstand na elke ander rooster-punt te bereken en te vergelyk met die horison lente, om dus so te bepaal of die punte bure is. Dit kan ’n baie berekenings intensiewe proses wees, veral as die probleem by elke stap opgedateer moet word om die veranderinge in die materiaal konfigurasie daar te stel. Die probleem word ook baie meer kompleks as die analise in parallel gedoen word. Verder het GVE’s (Grafiese verwerkings eenhede) baie gewild geword in die afgelope dekade. Die meeste van die vinnigste superrekenaars in die wêreld vandag gebruik GVE’s as versnellers te same met SVE’s (Sentrale verwerkings eenhede). Dit is ook van mening dat die volgende generasie exa-skaal superrekenaars GVE’s sal implementeer. Daarom is die fokus op hoe om ’n bure-lys soektog algoritme te ontwikkel wat gebruik sal maak van die volgende generasie hardeware. In hierdie tesis stel ons ’n SVE - veelvoudige GVE algoritme voor, wat ’n verlenging van die vaste-rooster metode is, vir die vaste-radius naaste bure soektog op groot skaal parallele stelsels.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Structural design standards based on the principles of structural reliability are gaining worldwide acceptance and are fast becoming the new basis of structural safety verification. The application of these principles to establish a standardised basis for structural design using partial factor limit states design procedures is done in the European Standard for the Basis of Structural Design EN 1990 from which it is adapted to the South African Basis of Design Standard for Building and Industrial Structures SANS 10160-1. The basis of design requirements stipulated in EN 1990 and SANS 10160-1 apply to all aspects of structural design: This includes reliability levels of structural performance and their differentiation and management; identification of various limit states and design situations; the specification of all the basic variables; separate treatment of actions and material-based resistance. However, application of these requirements is then primarily focused on actions whilst the provision for structural concrete is then left to the materials based design standards. This two-part thesis describes a systematic assessment of the degree to which the application of the reliability framework presented in the basis of design requirements has been achieved in the present generation of structural concrete design standards. More importantly, attempts are made to identify ways in which the process can be advanced. Special attention is drawn to issues that are specific to South African conditions and practice in structural concrete. Part One of the thesis focuses on the key elements of the reliability framework presented in EN 1990 and traces to what extent the requirements have been propelled through the design stipulations of the Eurocode Standard for Design of Concrete Structures EN 1992-1-1. The implications of the different reference level of reliability between the Eurocode default value of ß = 3.8 and that characteristic of South African practice ß = 3.0 through various issues are highlighted. The use and advantage of explicit treatment of reliability performance on reliability management related to some aspects of quality control are explored. A critical aspect is the shear prediction model providing unconservative estimates of shear resistance. Part Two of the thesis focuses on characterising the model factor of the EN 1992-1-1 shear prediction model for members requiring design shear reinforcement. This is done by a comparison to a compiled experimental database with special focus on situations with high reinforcement ratios. The significance of the modelling uncertainty in shear prediction is verified by this comparison. The use of the more conceptually rational modified compression field theory (MCFT) to improve on the quality of shear predictions is investigated and proves to yield more precise values with lower scatter hence making it a more reliable tool for predicting shear. The MCFT can then be used as reference for the reliability calibration and possible improvement for the Eurocode procedure. / AFRIKAANSE OPSOMMING: Strukturele ontwerpstandaarde gebaseer op die beginsels van strukturele betroubaarheid verkry wêreldwye aanvaarding en word vinnig die nuwe basis van strukturele veiligheid bevestiging. Die toepassing van hierdie beginsels om ʼn gestandaardiseerde basis vir strukturele ontwerp is bevestig deur gebruik te maak van gedeeltelike-faktorbeperkende stadiums ontwerpprosedures in die Europese Standaard vir die Basis van Strukturele Ontwerp EN 1990 waarvandaan dit herbewerk is na die Suid-Afrikaanse Basis van Ontwerp Standaarde vir Bou en Industriële Strukture SANS 10160-1. Die basis van ontwerpvereistes bepaal in EN 1990 en SANS 10160-1 is van toepassing op alle aspekte van strukturele ontverp: Dit sluit inbetroubaarheidsvlakke van struktureele prestasie en hul diversifikasie en bestuur; identifikasie van verskeie beperkende state en ontwerpsituasies; die spesifikasie van al die basiese veranderlikes; afsonderlike behandeling van aksies en materiaal-gebaseerde weerstand. Desnieteenstaande, die toepassing van hierdie voorwaardes is dan hoofsaaklik gefokus op aksies terwyl die voorsiening van strukturele beton is dan gelaat op die materiaalgebaseerde ontwerpstandaarde. Hierdie tweeledige verhandeling beskryf ʼn stelselmatige beoordeling van die graad waartoe die toepassing van die betroubaarheidsraamwerk aangebied word in die basis van ontwerpvereistes bereik in die huidige generasie van strukturele beton-ontwerp standaarde is. Meer belangrik, pogings is aangewend om die maniere hoe die proses bevorder kan word te identifiseer. Spesiale aandag word gevestig op kwessies wat spesifiek op Suid-Afrikaanse toestande en praktyke in strukturele beton toepaslik is. Deel Een van die verhandeling fokus op die sleutel-dele van die betroubaarheidsraamwerk aangebied in EN 1990 en skets die mate waartoe die vereistes aangespoor word deur die ontwerp voorskrifte van die Eurocode Standard for the Design of Concrete Structures EN 1992-1-1. Die implikasie van die verskillende verwysingsvlakke van betroubaarheid tussen die Eurocode standaardwaarde van ß = 3.8 en die eienskap van Suid-Afrikaanse praktyk ß = 3.0 deur verskillende kwessies word uitgelig. Die gebruik en voordeel van spesifieke behandeling van betroubaarheidsuitvoering op betroubaarheidsbestuur verwantskap met sekere aspekte van kwaliteit kontrole word ondersoek. ʼn Kritiese aspek is die model vir die voorspelling van skuif-weerstand wat die onkonserwatiewe beramings vir skuif-weerstand gee. Deel Twee van die verhandeling fokus op karakterisering die modelfaktor van die EN 1992- 1-1 skuif-weerstand voorspellings-model. Dit word gedoen deur ʼn vergelyking na ʼn saamgestelde eksperimentele databasis met spesifieke fokus op situasies met hoe herbevestigingsvergelykings. Die oorheersing van die modellering- onsekerheid in skuifweerstand voorspelling is bevestig deur hierdie vergelyking. Die gebruik van ʼn meer konseptuele rasionele gemodifiseerde druk-veld teorie (bekend as MCFT) om die kwaliteit van skuif voorspelling te verbeter is ondersoek en verskaf ‘n meer presiese waarde met laer verspreiding wat lei tot ʼn meer betroubaree instrument om skuif mee te voorspel. Die MCFT word dan gebruik as verwysing vir die betroubaarheid-samestelling en moontlike verbetering van die Eurocode prosedures.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Strain Hardening Cement-based Composite (SHCC) is part of the High Performance Fibre Reinforced Cement-based Composite (HPFRCC) family and is a relative new concrete composite. This Fibre Reinforced Cement-based Composite (FRCC) contains randomly distributed short fibres and when subjected to a uni-axial tensile load multiple cracking occurs. The multiple cracking generates fine cracks which are normally smaller than 100 μm and achieve a strain capacity of more than 5 %. There are limited publications regarding the research of sustained tensile tests on SHCC and especially the cracking behaviour of SHCC under quasi-static uni-axial as well as sustained tensile loads. The cracking behaviour is described as the average crack width, number of cracks and descriptive statistical properties which could be used to represent the distribution of the multiple fine cracks under uni-axial tension. There are two types of tests that were under consideration to determine the cracking behaviour of SHCC. The first is quasi-static uniaxial tensile tests and the second is sustained tensile tests. The latter was dependant on the uni-axial tensile tests in terms of the sustained load applied. The sustained loads ranged from 40 % to 80 % of the ultimate tensile resistance recorded from the uni-axial tensile tests that correspond with a strain rate of 0.001 /s. Different strain rates were used for the uni-axial tensile tests to determine the effect on the cracking behaviour. The cracking behaviour was determined with the aid of a non-contact optical 3D digital deformation measuring device called ARAMIS. The content of this thesis gives a background study of the cracking behaviour and relevant research performed on SHCC under certain loads as well as some literature about the timedependant effects of a cement-based composite. The functioning of the device called ARAMIS is explained as well as the resulting effects of this device on the preparation of the test specimens. The experimental framework for the uni-axial and sustained tensile tests is discussed. Thereafter, the experimental results of the tests are depicted and discussed. The results shed some light on the basic material properties such as the average ultimate stress and average ultimate strain, Young’s modulus, etc. for the quasi-static tensile tests as well as shrinkage and creep of SHCC. The cracking behaviour such as the average crack width, number of cracks, the variance and skewness of the distribution of the crack widths in the test specimens for the quasi-static uni-axial and sustained tensile tests are depicted and discussed. The cracking behaviour when subjected to uni-axial tensile tests with different strain rates is significantly governed by the formation of new cracks and the average crack width remains small with increase in strain. There is no significant difference for the cracking behaviour found when subjected to different strain rates. However, when SHCC is subjected to a sustained load then the average crack width is dependant on the number of cracks that form over time as well as the load level. The formation of fewer and wider cracks was observed for specimens loaded at average 40 % of the ultimate tensile resistance stress, however at loading percentages of higher than 65 % more cracks developed which resulted in a smaller average crack width. / AFRIKAANSE OPSOMMING: Vervorming Verharding Sement gebaseerde samestelling “Strain Hardening Cement-based Composite” (SHCC) is deel van die familie van “High Performance Fibre Reinforced Cement-based Composite” (HPFRCC) en is ʼn relatiewe nuwe beton samestelling. Hierdie vesel versterkte sement gebaseerde beton bevat willekeurig verspreide kort vesels en veelvoudige klein krake vorm onder monotoniese trekkragte. Hierdie veelvoudige klein krake is minder as 100 μm wyd en lei tot ʼn vervorming van meer as 5 %. Daar is ʼn tekort aan navorsing oor die kruip van SHCC sowel as die kraak gedrag van hierdie sement gebaseerde samestelling onderhewig aan trek. Die kraak gedrag word beskryf as die gemiddelde kraakwydte, aantal krake en ʼn paar beskrywende statistiese parameters. Hierdie kraak gedrag parameters kan gebruik word om ʼn verdeling te kan weergee van die veelvoudige klein krake onder ʼn trek belasting. Twee tipes toetse was uitgevoer om die kraak gedrag te beskryf. Die eerste tipe toets was monotoniese trek toetse en die tweede tipe was kruip toetse. Die tweede toets was afhanklik van die monotoniese trek toetse in terme van die belasting wat gebruik was vir die kruip toetse. Die belasting was gevarieer vanaf 40 % tot 80 % van die breekbelasting wat bepaal is met die monotoniese trektoetse wat ooreenstem met ʼn vervorming tempo van 0.001 /s. Verskillende vervorming tempo’s vir die monotoniese trektoetse was uitgevoer om te bepaal wat die effek is op die kraak gedrag. Die kraak gedrag was bepaal met behulp van ʼn geen-kontak optiese 3D digitale deformasie meet instrument genoem ARAMIS. Die inhoud van die tesis bevat ʼn kort opsoming oor ʼn agtergrond studie van die kraak gedrag en relevante navorsing oor vesel versterkte sement gebaseerde beton, sowel as literatuur oor die tydafhanklike effekte van ʼn sement gebaseerde samestelling. Die beheer en gebruik van die meet instrument ARAMIS word verduidelik, sowel as die effek van hierdie masjien op die voorbereiding vir die eksperimente. Die eksperimentele uiteensetting vir die monotoniese en kruip toetse word beskryf. Daarvolgens is die resultate van die eksperimentele toetse getoon en verduidelik. Die resultate verduidelik die basiese materiaal eienskappe, byvoorbeeld die gemiddelde breekspanning met die ooreenkomstige breekvervorming, Young’s modulus en so voorts vir die monotoniese trektoetse, sowel as eienskappe met betrekking tot krimp en kruip van SHCC. Die kraak gedrag naamlik die gemiddelde kraakwydte, aantal krake per meter, variansie en die skuinsheid van die ontwikkelde krake met die toets proefstukke vir die monotoniese en kruip trek toetse word weergegee en verduidelik. Die kraak gedrag van SHCC wanneer getoets word met verskillende monotoniese trektoets tempo’s word beheer deur die ontwikkeling van nuwe krake en die gemiddelde kraakwydte is beduidend laag met toenemende vervorming. Daar is geen beduidende verskil in die kraak gedrag ten opsigte van die verskillende monotoniese trek tempo’s nie. In teendeel, wanneer SHCC belas word met ʼn konstante las oor tyd word die gemiddelde kraakwydte beheer deur die ontwikkeling van nuwe krake sowel as die belasting wat aangewend is. Onder ʼn belasting van so laag as 40 % van die breekbelasting vorm daar minder krake, maar met ʼn groter gemiddelde kraakwydte. Wanneer belas word met meer as 65 % van die breekbelasting vorm meer krake wat lei tot ʼn kleiner gemiddelde kraakwydte.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2002. / 198 leaves double sided printed, preliminary pages i-xx and numberd pages 1-1-12-6.Includes bibliography. List of tables, figures and appendices and acronyms. Scanned with a HP Scanjet 8250 Scanner to pdf format (OCR). / ENGLISH ABSTRACT: In this study the numerical short wave model SWAN is evaluated for application to a selected coastal region in South Africa. The aim of this study was to evaluate the degree of accuracy with which SWAN can simulate prototype nearshore wave spectra and wave parameters (e.g. wave height, mean wave direction and mean wave period) for an Algoa Bay field case. Algoa Bay represents a typical deep, sheltered embayment on the South African south coast, which is exposed to high-energy swell. Sensitivity analyses on various wave-related processes were also done, with the aim of establishing the dominant physical processes and appropriate model setup for the Algoa Bay field case. With the dominant wave-related processes and appropriate model setup for the Algoa Bay field case established, selected final runs were performed to determine the degree of accuracy with which SWAN can simulate prototype conditions, by comparing its results with available field recordings. This study comprises a review of the SWAN evaluation work conducted to date by others, an overview of South African coastal conditions, and numerical model simulations. The model simulations, which represent the main focus of this study, were conducted for a selection of available offshore wave conditions (at 85 m water depth) observed during the Algoa Bay field case and were compared to available nearshore observations (at 17 m water depth). Environmental conditions of waves, wind and currents were included in these simulations. The study focuses on model application and sensitivity analysis, rather than model development, and includes evaluation of all relevant processes, without focussing on any specific model aspect. The results of this study show that SWAN simulations correlated well with observations at the nearshore station in Algoa Bay, both in wave spectral shape and its associated parameters. Dominant processes identified for the field case were depth-induced refraction, bottom friction and directional spreading. This finding agrees with those of previous evaluations of SWAN and previous modelling experience by others. It is shown that high-energy swell is relatively more sensitive to the choices of model setup than wind sea. Based on the simulation results of high-energy swell, it is concluded that the calculation of depth-induced refraction in SWAN seem to contain a degree of inaccuracy. It is also concluded that the findings of this study could be used as a guideline to SWAN modelling studies along the South African south coast. / AFRIKAANSE OPSOMMING: In hierdie studie word die toepassingsmoontlikhede van die numeriese kortgolf model SWAN vir 'n geselekteerde gedeelde van die Suid-Afrikaanse kuslyn beoordeel. Die doel van hierdie studie is om die vlak van akkuraatheid waarmee SWAN prototipe golfspektra en golfparameters (bv. golfhoogte, gemiddelde golfrigting en gemiddelde golfperiode) in die vlakwater kan simuleer te beoordeel, vir 'n Algoabaai gevallestudie. Algoabaai verteenwoordig 'n tipiese diep, beskermde baai aan die Suid-Afrikaanse kuslyn, wat blootgestel is aan hoe-energie deining. Sensitiwiteitstoetse is ook uitgevoer vir verskillende golfprosesse, met die doel om die dominante fisiese prosesse en gepaste modelopstelling vir die Algoabaai gevallestudie te vind. Nadat die dominante golfprosesse geidentifiseer is, en die toepaslike modelopstelling gevind is, is finale simulasies uitgevoer vir geselekteerde gevalle om die mate van akkuraatheid te bepaal waarmee SWAN prototipe kondisies kan simuleer, deur simulasie resultate met beskikbare veldmetings te vergelyk. Hierdie studie bestaan uit 'n samevatting van die evaluasiewerk verrig op SWAN deur andere, 'n samevatting van golf-, wind- en stroomtoestande aan die Suid-Afrikaanse kus en numeriese modelsimulasies. Die modelsimulasies, wat die hooffokus van hierdie studie is, is uitgevoer vir 'n seleksie van beskikbare diepsee golftoestande (in 85 m waterdiepte) uit die Algoabaai gevallestudie en is vergelyk met beskikbare vlakwater metings (in 17 m waterdiepte). Omgewingstoestande van golwe, wind en seestrome is ingesluit in hierdie simulasies. Die studie fokus op modeltoepassing en sensitiwiteits-analise, eerder as modelontwikkeling, en behels die beoordeeling van alle toepaslike modelprosesse, sonder om te fokus op enige spesifieke model aspek. Die resultate van hierdie studie toon aan dat die SWAN simulasies goed korrileer met vlakwater meetings in Algoabaai, vir beide golfspektraalvorm en verwante golfparameters. Bodemrefraksie, bodemwrywing en rigtingsspreiding is geidentifiseer as dominante modelprosesse. Hierdie resultaat kom ooreen met bevindings van vroeere beoordeling van SWAN en modelleer-ervaring deur andere. Dit word aangetoon dat hoe-energie deining relatief meer sensitief is vir modelopstelling as wind-see. Gebasseer op resultate van simulasie met hoe-energie deining, word die gevolgtrekking gemaak dat die berekening van bodemrefraksie in SWAN 'n mate van onakkuraatheid toon. Die gevolgtrekking word ook gemaak dat die resultate van hierdie studie as riglyn gebruik kan word vir modelleerwerk met SWAN aan die Suid-Afrikaanse suidkus.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Reinforced concrete structures, designed according to proper capacity design guidelines, can deform inelastically without loss of strength. Therefore, such structures need not be designed for full elastic seismic demand, but could be designed for a reduced demand. In codified design procedures this reduced demand is obtained by dividing the full elastic seismic demand by a code-defined behaviour factor. There is however not any consensus in the international community regarding the appropriate value to be assigned to the behaviour factor. This is evident in the wide range of behaviour factor values specified by international design codes. The purpose of this study is to assess the seismic drift of reinforced concrete structural walls in order to evaluate the current value of the behaviour factor prescribed by SANS 10160-4 (2009). This is done by comparing displacement demand to displacement capacity for a series of structural walls. Displacement demand is calculated according to equivalency principles (equal displacement principle and equal energy principle) and verified by means of a series of inelastic time history analyses (ITHA). In the application of the equivalency rules the fundamental periods of the structural walls were based on cracked sectional stiffness from moment-curvature analyses. Displacement capacity is defined by seismic design codes in terms of inter storey drift limits, with the purpose of preventing non-structural damage in building structures. In this study both the displacement demand and displacement capacity were converted to ductility to enable comparison. The first step in seismic force-based design is the estimation of the fundamental period of the structure. The influence of this first crucial step is investigated in this study by considering two period estimation methods. Firstly, the fundamental period may be calculated from an equation provided by the design code which depends on the height of the building. This equation is known to overestimate acceleration demand, and underestimate displacement demand. The second period estimation method involves an iterative procedure where the stiffness of the structure is based on the cracked sectional stiffness obtained from moment-curvature analysis. This method provides a more realistic estimate of the fundamental period of structures, but due to its iterative nature it is not often applied in design practice. It was found that, regardless of the design method, the current behaviour factor value prescribed in SANS 10160-4 (2010) is adequate to ensure that inter storey drift of structural walls would not exceed code-defined drift limits. Negligible difference between the equivalency principles and ITHA was observed. / AFRIKAANSE OPSOMMING: Gewapende beton strukture wat ontwerp is volgens goeie kapasiteitsontwerp-riglyne kan plasties vervorm sonder verlies aan sterkte. Gevolglik hoef hierdie strukture nie vir die volle elastiese seismiese aanvraag ontwerp te word nie, maar kan vir 'n verminderde aanvraag ontwerp word. In gekodifiseerde ontwerpriglyne word so 'n verminderde aanvraag verkry deur die volle elastiese aanvraag te deel deur 'n kode-gedefinieerde gedragsfaktor. Wat egter duidelik blyk uit die wye reeks van gedragsfaktor waardes in internasionale ontwerp kodes, is dat daar geen konsensus bestaan in die internasionale gemeenskap met betrekking tot die geskikte waarde van die gedragsfaktor nie. Die doel van hierdie studie is om seismiese verplasing van gewapende beton skuifmure te evalueer ten einde die waarde van die gedragsfaktor wat tans deur SANS 10160-4 (2009) voorgeskryf word te assesseer. Dit word gedoen deur verplasingsaanvraag te vergelyk met verplasingskapasiteit. In hierdie studie word verplasingsaanvraag bereken deur middel van gelykheidsbeginsels (gelyke verplasingsbeginsel en gelyke energiebeginsel) en bevestig deur middel van nie-elastiese tydsgeskiedenis analises (NTGA). Die effek van versagting as gevolg van nie-elastiese gedrag word in aanmerking geneem in die toepassing van die gelykheidsbeginsels. Verplasingskapasiteit word deur seismiese ontwerpkodes gedefinieer deur perke te stel op die relatiewe laterale beweging tussen verdiepings, met die doel om nie-strukturele skade te verhoed. Om verplasingsaanvraag en -kapasiteit te vergelyk in hierdie studie, word beide omgeskakel na verplasingsduktiliteit. Die eerste stap in kraggebaseerde seismiese ontwerp is om die fundamentele periode te beraam. Die invloed van hierdie eerste kritiese stap word in hierdie studie aangespreek deur twee periodeberamingsmetodes te ondersoek. Eerstens kan die fundamentele periode bereken word deur 'n vergelyking wat 'n funksie is van die hoogte van die gebou. Dit is egter algemeen bekend dat hierdie vergelyking versnellingsaanvraag oorskat en verplasingsaanvraag onderskat. Die tweede metode behels 'n iteratiewe prosedure waar die styfheid van die struktuur gebaseer word op die gekraakte snit eienskappe, verkry vanaf 'n moment-krommingsanalise. 'n Beter beraming van die fundamentele periode word verkry deur hierdie metode, maar as gevolg van die iteratiewe aard van die metode word dit selde toegepas in ontwerppraktyk. Die resultate van hierdie studie toon dat die huidige waarde van die gedragfaktor soos voorgeskryf in SANS 10160-4 (2010) geskik is om te verseker dat die relatiewe laterale beweging tussen verdiepings binne kode-gedefinieerde perke sal bly. Onbeduidende verskil is waargeneem tussen die resultate van gelykheidsbeginsels en NTGA.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: In the study, six irrigation schemes based in the Eastern Cape have been considered and evaluated, according to two levels of supply (LOS) of irrigation water. The two levels of supply are that of a commercial irrigator and that of a smallholder irrigator. The irrigation infrastructure for each of the six schemes was designed, and the associated costs determined, for each level of supply. The primary objective of the study is to determine the impact of infrastructure costs and irrigation areas on the target user, either the commercial or the smallholder irrigator. This is related directly to the assumption that lower water volumes are used by the smallholder irrigator. The study addresses the impact of different designs on the amount of water used, land utilised and resultant costs of the infrastructure. The initial capital costs and the on-going operational and maintenance costs (O&M) for each level of supply for each of the schemes have been calculated. The evaluation of the two LOS has shown that the capital cost for the commercial LOS is approximately 18 % higher than for the smallholder LOS and the O&M costs 6 % to 36 % higher. The schemes that were investigated can be grouped into five general scheme types. The first type is gravity schemes, which need rehabilitation, while the bulk supply is in place with no augmentation or rehabilitation required. The second is pumped scheme which is in need of rehabilitation, while the bulk supply is in place with no augmentation or rehabilitation required. The third type includes run-of-river schemes where water is abstracted and pumped directly to the lands. The fourth type includes run-of-river schemes where water is abstracted and pumped to storage. The fifth type is the gravity scheme where the bulk supply needs to be installed as part of the scheme. These types are then grouped and can be used to give guidance on the anticipated costs dependant on the scheme type and the required level of service. A further objective of the research is to determine the impact on the smallholder irrigators who find themselves on a commercial LOS system. This can be either on a scheme that has already been designed, or on a new system. The evaluation of the commercial under-utilised LOS and the smallholder LOS has shown that the commercial capital cost is 18 % higher and the O&M costs 5 % to 29 % higher. The study further aligns the estimated costs with the farmer typology providing a broader understanding of the design to be adopted for different levels of supply. This provides the linkage between farmer types, the design to be implemented and the anticipated costs thereof. / AFRIKAANSE OPSOMMING: As deel van hierdie narvorsing word ses verskillende besproeiingsskemas in die Oos-Kaap ten opsigte van twee voorsieningsvlakke ondersoek. Die twee voorsieningsvlakke ter sprake is vir ‘n kommersiële en kleinboerdery opset. Die besproeiingsinfrastruktuur is vir elk van die ses besproeiingsskemas ontwerp en ‘n kosteberaming vir elk van voorsieningsvlakke gedoen. Die hoofdoelwit van hierdie verslag is om te bepaal wat die impak van kostes en besproeiingsareas op beide kommersiële- en kleinboerderye is. Dit is direk gebaseer op die aanname dat kleinboerderye minder water gebruik. Die verslag ondersoek die impak van verskillende ontwerpe op waterverbruik, besproeiingsoppervlak benodig en die gevolglike infrastruktuurkostes. Die aanvanklike kapitaalkostes asook bedryfs- en onderhoudsuitgawes (B&O) vir elk van die voorsieningsvlakke, is vir elk van die besproeiingskemas bereken. Die resultaat van die ondersoek van die twee voorsieningsvlakke het aangetoon dat die kapitaalkoste van kommersiële besproeiingskemas 18 % hoër as die van kleinboerderye is, en bedryfs- en onderhoudsuitgawes 6 tot 36 % hoër. Die skemas wat ondersoek is, kan in vyf algemene skema tipes verdeel word. Die eerste is die gravitasieskemas wat rehabilitasie benodig terwyl die hooftoevoer in plek is met geen uitbreidings- of rehabilitasiebehoeftes. Die tweede is pompskemas wat rehabilitasie benodig terwyl die hooftoevoer in plek is met geen uitbreidings- of rehabilitasiebehoeftes. Die derde is rivierskemas waar besproeiingswater direk uit die rivier na die landerye gepomp word. Die vierde is rivierskemas waar besproeiingswater direk uit die rivier na a reservoir gepomp word. Die vyfde skema tipe is die gravitasieskemas waar die hooftoevoer ook gebou moet word as deel van die skema. Die skema tipes kan gebruik word om leiding te verskaf ten opsigte van verwagte skema kostes afhangende van die skema tipe en vereiste voorsieningsvlak. ‘n Verdere doelwit van die studie is om die impak op kleinboere te bepaal wat op ‘n kommeriële voorsieningsvlak boer. So ‘n stelsel kan ‘n gevestigde of nuwe stelsel wees. Die resultaat van die ondersoek van die onderbenutte kommersiële voorsieningsvlak en die kleinboerdery voorsieningsvlak het gewys dat die kapitaalkoste van kommersiële besproeiingskemas 18 % hoër as die van kleinboerderye is, en bedryfs- en onderhoudsuitgawes 5 tot 29 % hoër. Die verslag vereenselwig die verwagte kostes met die tipe boerdery en verskaf ‘n beter begrip van die tipe ontwerp wat elk van die voorsieningsvlakke benodig. Dit verskaf dus die verband tussen die tipe boerdery, die ontwerp benodig en die verwagte projekkostes.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The various consequences of climate change pose a significant threat to developments near the coast. These threats include saltwater intrusion, coastal erosion and flooding. In the coastal context, the climate change effect often raising the most concern is that of sea-level rise. Much work has therefore been done on the linear setback caused by a rise in sea-level. In order to get the full picture of possible changes caused by sea-level rise, the secondary effects of a rising sea-level also need to be considered. Sea-level rise could cause changes to the nearshore wave climate and could have impacts such as coastal erosion and changes to the coastline shape. The primary objective of this study was therefore to investigate the effects of sea-level rise on the nearshore wave climate and, consequently, the coastline stability. Other consequences of climate change considered in this study include increasing average wave heights and a rotation of offshore wave directions. The many headland-bay beaches on the South African coastline are generally in a state of dynamic equilibrium and find their planforms based on the local wave climate. Changes to the wave climate may therefore disrupt the equilibrium shapes of these bays. This study was therefore also aimed at investigating the effects of the changes to the wave climate on the stability of headland-bay beaches. The three consequences of climate change expected to affect the nearshore wave climate were identified as (1) sea-level rise; (2) an increased wave height; and (3) changing offshore wave angles. Although changes to storm frequency and intensity are also possible, the impacts of these changes were not studied. In order to assess the impacts of the three considered changes on a typical headland-bay beach, two numerical models were set up for Mossel Bay – a headland-bay beach on the southern coast of South Africa. The modelling approach included a wave transformation model to calculate nearshore wave climates from offshore data and a coastline model to assess the stability of the bay under the changed nearshore wave climates. The model results indicated that the rising sea-level alone would cause changes in the nearshore wave direction. These changes were shown to alter the longshore sediment transport regime such that rotations are expected in the south-western corner and eastern end of Mossel Bay. These rotations do not include the cross-shore effects of inundation and erosion, as suggested by models such as the Bruun Model. The results for an increased offshore wave height were inconclusive. The southerly rotation in offshore wave angles was shown to affect the nearshore wave angles. These changes affected the longshore transport regime such that the outward sediment transports were reduced. A minor accretion resulted in the centre of the bay for a 1° southerly rotation in offshore wave angles. For a 2° rotation, the extent of accretion increased and shifted towards the eastern end of the bay, primarily due to the dominance of south-westerly waves in the local wave climate. A valuable observation was made regarding the current stability of Mossel Bay. Inter-tidal reefs are present along three sections of the bay. These reefs protect the coastline such that the current bay shape contains sharp bends between the reefs. Under a rising sea-level, however, the effect of the reefs will become less pronounced. If a water level should be reached where these reefs become less significant, the planform of the bay is expected to smooth out through a significant redistribution of sediment. This smoothing effect was shown to cause erosion of the coastline in the order of 80m near the town of Klein Brak River. / AFRIKAANSE OPSOMMING: Die verskeie gevolge van klimaatsverandering bied ‘n merkwaardige bedreiging vir ontwikkelings naby die kus. Hierdie bedreigings sluit die versouting van varswaterbronne, kuserosie en oorstromings in. Vir kusgebiede is seevlakstyging gereeld die effek van klimaatsverandering wat die meeste kommer wek. Dus is heelwat navorsing rakende die direkte erosie as gevolg van seevlakstyging reeds gedoen. Om die volle beeld van die gevolge van ‘n stygende seevlak te verkry, is dit egter nodig om ook die sekondêre effekte hiervan in ag te neem. Seevlakstyging kan veranderinge in die golfklimaat naby die kus veroorsaak, en kan impakte soos kuserosie en veranderende baaivorms tot gevolg hê. Die primêre doel van hierdie studie is dus om die effek van seevlakstyging op die golfklimaat by die kus en gevolglik die stabiliteit van die kuslyn, te ondersoek. Benewens die styging van die seevlak word die effekte van groter gemiddelde golfhoogtes en die rotasie van diepsee golfrigtings ook in hierdie studie ondersoek. Die vele landpunt-baaie (headlandbay beaches) op die Suid-Afrikaanse kus is meestal in ‘n dinamiese ekwilibriumtoestand, waarvan die vorm deur die lokale golfklimaat bepaal word. Veranderinge aan dié golfklimaat mag dus die ekwilibrium vorms van sulke baaie versteur. Hierdie studie het dus ook die stabilititeit van landpuntbaaie onder ‘n veranderende golfklimaat ondersoek. Die drie gevolge van klimaatsverandering wat verwag word om die golfklimaat naby die kus te beïnvloed is geïdentifiseer as (1) seevlakstyging; (2) vergrote golfhoogtes; en (3) veranderende diepsee golfhoeke. Veranderinge aan die frekwensie en intensiteit van storms is ook moontlike gevolge van klimaatsverandering, maar die impakte hiervan is nie in die studie ondersoek nie. Twee numeriese modelle is toegepas om die impak van die drie bogenoemde gevolge op Mosselbaai – ‘n tipiese landpunt-baai aan die suidkus van Suid-Afrika – te ondersoek. ‘n Golfmodel is ingespan om die golfklimaat naby die kus te bepaal waarna ‘n kuslynmodel gebruik is om die stabiliteit van die baai onder die veranderde golfklimaat te ondersoek. Die resultate van die studie dui daarop dat die golfhoeke naby die kus beïnvloed word deur seevlakstyging. Daar is aangetoon dat dié veranderinge die langsstroomvervoer sodanig sal verander dat kuslynrotasies in die suid-westelike hoek asook die oostelike rand van Mosselbaai verwag word. Hierdie rotasies sluit nie die lineêre landwaartse verplasing van die kuslyn as gevolg van erosie en oorstroming in nie. Die effek van vergrote golfhoogtes kon nie met akkuraatheid ondersoek word nie. Daar is wel gevind dat die suidwaartse rotasie van diepsee golfhoeke rotasies in die golfklimaat naby die kus veroorsaak. Hierdie rotasies verander die langsstroom sedimentvervoer sodanig dat die uitwaartse sedimentvervoer verminder word en ‘n klein opbou van sediment in die middel van die baai vir ‘n 1° diepsee rotasie verwag word. Vir ‘n 2° suidwaartse rotasie is daar ‘n groter opbou van sediment wat verder ooswaarts veplaas is. Die ooswaartse veplasing is primêr ‘n gevolg van die oorheersing van suid-westelike golftoestande in die golfklimaat. ‘n Waardevolle gevolgtrekking rakende die huidige stabiliteit van Mosselbaai is ook gemaak. Langs drie gedeeltes van die Mosselbaaise kus word riwwe in die gebied tussen hoog- en laagwater aangetref. Hierdie riwwe beskerm die kus sodanig dat skerp kinkels in die vorm van die baai tussen die riwwe gesien kan word. Wanneer die seevlak styg, word die beskermende effek van die riwwe egter minder doeltreffend. Indien ‘n watervlak bereik word waar dié effek genoegsaam verminder is, word daar verwag dat die baai deur ‘n merkwaardige verplasing van sediment die kinkels sal uitstryk. Deur hierdie proses word erosie in die orde van 80m naby die dorp van Klein Brakrivier verwag.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This study focuses on the water demand of selected residential properties with access to groundwater in serviced areas of the Cape Peninsula. This winter rainfall region is typified by hot and dry summer months, corresponding to peak garden water demand. Water restrictions in the area are relatively common and primarily target outdoor use. Groundwater serves as an alternative source of water to some consumers in the area, but little is known about the extent of such use and the impact thereof on potable water demand. A major part of the area is underlain by a primary, unconfined aquifer that has been reported to have high exploitation potential. Its unconsolidated sand and shallow water table provides ideal conditions for small scale groundwater abstraction. Several owners of properties situated above the aquifer unit have capitalised on this and utilise groundwater as an alternative to potable water, mostly for garden irrigation purposes. The main objective of this research was to investigate the average extent of the expected reduction in average annual municipal water demand due to private groundwater use at the selected properties in the study area. The methodology involved abstracting data from the City of Cape Town’s registration process for the private use of non-potable water. The data was recorded between 2000 and 2006 and was available only in hard copy format. The registration data was used to identify residential properties with access to private groundwater sources, based on the physical addresses recorded on the registration forms. The rate of groundwater abstraction was not recorded during the registration process, nor was any of the properties spatially referenced. The data set contained information for 4 487 properties, of which 3 764 could ultimately be used in the analysis. Data from a recent hydro-census in Hermanus (which was done by others prior to this study) was used to test the intended research method first. This trial investigation involved only 114 properties and was used to streamline the proposed methodology for application on the full-scale analysis of the City of Cape Town data. Each address was captured electronically, verified manually and filtered to extract only those representing residential properties for which groundwater use was registered. In order to identify the properties spatially, the addresses had to be converted to coordinates through a procedure called geocoding, so as to plot each spatially and obtain the attributes such as stand size, position and the unique Surveyor General’s code. This was necessary in order to link the addresses to the municipal treasury system and obtain their latest available water consumption records using a commercial software package that incorporates consumer information. Next the actual annual water consumption figures were compared with recently published water demand guidelines based on stand size as single explanatory variable. The selected residential stands were divided into pre-defined stand size categories. The average water consumption of all the stands in each size category was calculated and compared with the suggested water demand as per the guidelines used, based on the centre value of the size range of each category. The results of the comparative analysis confirm findings from two earlier studies where lower municipal water use was reported for residential properties with access to groundwater in a summer rainfall region. The results further showed that the mean average annual potable water demand of consumers in the study area with access to groundwater was on average 31.4% lower than those considered without such access in the same region. This represents an average reduction of 333 l/stand/day (about 10 kl/stand/month) in the potable water demand of the selected residential stands. This study therefore confirms that serviced residential stands with access to private groundwater sources in the Cape Peninsula have lower average metered water consumption from the municipal supply system. / AFRIKAANSE OPSOMMING: Hierdie studie fokus op die water anvraag van geselekteerde residensiële erwe met toegang tot grondwater in gedienste woongebiede van die Kaapse Skiereiland. Die gebied is ‘n winterreënvalstreek, met warm, droë somermaande wat saamval met piek water aanvraag vir tuinbou. Waterbeperkings in die area is relatief algemeen, veral op die buitegebruik van water. Grondwater dien as alternatiewe bron vir sommige verbruikers, maar kennis oor die omvang van sulke gebruik, sowel as die impak wat dit het op die aanvraag na drinkbare water is beperk. Die grootste deel van die gebied ter sprake is geleë bo ‘n onbegrensde hoof waterdraer, met berigte hoë ontginningspotensiaal. Die ongekonsolideerde sand en hoë watertafel is ideal vir kleinskaalse grondwateronttrekking. Heelwat van die eienaars van grond wat bo hierdie akwafeer geleë is het die situasie uitgebuit en gebruik grondwater as alternatief vir drinkwater, veral vir tuinbesproeiïng. Die hoofdoel van hierdie navorsing was om die gemiddelde omvang van die verwagte vermindering in gemiddelde jaarlikse munisipale wateraanvraag weens die privaat gebruik van grondwater by die geselekteerde erwe in die studiegebied te ondersoek. Die metodiek het die onttrekking van data uit die Stad Kaapstad se registrasieproses vir die privaat gebruik van nie-drinkbare water behels. Hierdie data, wat tussen 2000 en 2006 vasgelê is, was slegs in harde kopie formaat beskikbaar. Die registrasie data is gebruik om woonerwe te identifiseer met toegang tot privaat grondwater bronne, volgens die fisiese adres verskaf op die registrasie vorms. Die tempo van grondwater onttrekking was nie opgeneem gedurende die registrasie proses nie, so ook nie ruimtelike aanwysings na die ligging van die eiendomme nie. Die datastel het inligting bevat oor 4 487 eiendomme, waarvan 3 764 uiteindelik bruikbaar was in die analise. Data van ‘n onlangse hidro-sensus in Hermanus (wat deur ander gedoen is voor die aanvang van hierdie studie) is gebruik om die beoogde navorsingsmetodiek eers te toets. Die toetsondersoek het slegs 114 eiendomme behels, en is gebruik om die voorgestelde metodologie meer vaartbelyn te maak voor toepassing op die volskaalse analise van die Stad Kaapstad data. Elke adres is elektronies vasgevang, met die hand geverifiëer, en dan gefilter om slegs die residensiele eiendomme waarvoor grondwater gebruik geregistreer is, te behou. Om die ruimtelike verwysing van die eiendomme verder te kon indentifiseer, moes die adresse omskep word in koördinate om sodoende die erwe te kon posisioneer en die erfgrootte, posisie en die unieke Landmeter Generaal kode van elke erf te verkry. Dit was nodig sodat die adresse aan die munisipale stelsel gekoppel kon word om sodoende die jongste beskikbare waterverbruik rekords te verkry deur gebruik te maak van ‘n kommersiële sagteware pakket wat verbruikers-inligting inkorporeer. Hierna is die werklike jaarlikse waterverbruik syfers vergelyk met onlangs gepubliseerde wateraanvraag riglyne, gebaseer op erfgrootte as enkel verklarende veranderlike. Die geselekteerde woonerwe is toe in voorafgekose kategorië verdeel volgens erfgrootte. Die gemiddelde waterverbruik van al die erwe binne elke grootte-kategorie is bereken en vergelyk met die voorgestelde wateraanvraag volgens die riglyne, gebaseer op die middelpuntwaarde van die grootte strekking van elke kategorie. Die resultate van die vergelykende analise staaf die bevindinge van twee vroeër studies wat laer munisipale watervebruik rapporteer vir residensiële eiendomme met toegang tot grondwater in ‘n somerreënvalgebied. Die resultate wys ook dat die gemiddelde jaarlikse drinkbare water aanvraag van verbruikers in die studiegebied wie toegang het tot grondwater, gemiddeld 31.4% laer is as dit van verbruikers wie beskou word sonder sulke toegang in dieselfde streek. Dit verteenwoordig ‘n gemiddelde vermindering van 333 l/erf/dag (rondom 10 kl/erf/maand) in die aanvraag na drinkbare water van die geselekteerde woonerwe. Hierdie studie bevestig dus dat gedienste residensiële erwe met toegang tot privaat grondwater bronne in die Kaapse Skiereiland laer gemiddelde gemeette waterverbruik vanuit die munisipale toevoerstelsel het.