Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aim of this research is to investigate the potential use of coarse recycled concrete aggregate (RCA) as a material in structural concrete. The lack of knowledge and specifications in South Africa are the main reasons for this research of RCA. By increasing the database of research of RCA in South Africa the possibility of specifications for this alternative building material can be initiated. The implications of such specifications would lead to RCA acceptance in concrete design and therefore reducing the amount of construction and demolition (C&D) waste accumulating at landfill sites and decreasing the extraction of depleting natural aggregates. The objectives that are achieved through this research project are firstly, what is the percentage replacement of RCA to a concrete blend that will produce a material that achieves similar or better results than a concrete blend containing natural aggregates. Secondly, what aggregate properties and limits should be defined in the specification of RCA for it to be accepted as a material in concrete mixtures. The objectives were assessed through examining the geometrical, physical and chemical properties of the aggregate as a material and the fresh and hardened concrete properties of concrete which contains RCA as a constituent. RCA which was processed by a commercial recycling facility which produces concrete masonry units was collected at three different instances. This material was reprocessed in the laboratory to control the grading and amount of fine material not guaranteed by the recycling process. The RCA is then combined with natural aggregate (NA) at the replacement percentages: 0, 15, 30, 50 and 100% which is then used to examine the aggregate properties. It was determined that the physical properties of RCA were dependent on the geometrical properties, while taking into consideration that the geometrical properties are dependent on the source and method of recycling of the original C&D waste. The chemical properties were established as dependent on the physical properties of the RCA. The RCA is then mixed with NA at the same replacement percentages together with other concrete constituents to produce the concrete used to examine fresh and hardened concrete properties. The fresh concrete properties investigated were: slump, slump loss, air content and fresh compacted density. The hardened concrete properties studied were: compressive strength, tensile splitting strength, oxygen permeability, water sorptivity, chloride conductivity, modulus of elasticity, shrinkage and creep. The concrete properties were not significantly influenced by the inclusion of RCA. According to the aggregate and concrete properties examined in this investigation, the full replacement of NA in structural concrete is possible and will improve the sustainable development of the construction industry. / AFRIKAANSE OPSOMMING: Die doel van hierdie navorsing is om ondersoek in te stel na die potensiele gebruik van growwe herwonne betonaggregaat (RCA) as ‘n materiaal in betonstruktuurontwerp. Die gebrek aan kennis en spesifikasies in Suid Afrika is die vernaamste rede vir hierdie navorsing van RCA. Deur die vermeerdering van die databasis van hierdie navorsing van RCA in Suid-Afrika kan die moontlikheid van spesifikasies vir hierdie alternatiewe boumateriaal geïnisieer word. Die implikasie van sodanige spesifikasies sou lei tot RCA aanvaarding in betonontwerp en dus die vermindering van die hoeveelhede konstruksie en sloping (C&D) van afvalversameling by stortterreine en om die ontginning van natuurlike aggregate te verminder. Die doelwitte wat deur hierdie navorsingsprojek bereik word is eerstens, wat is die vervangings persentasie van RCA in 'n betonmengsel wat produseer word wat dieselfde of beter resultate sal lewer as 'n betonmengsel wat uit natuurlike aggregate bestaan. Tweedens, watter aggregaat eienskappe en beperkings moet gedefinieer word in die spesifikasie van RCA sodat dit aanvaarbaar is as ‘n materiaal in betonstruktuur ontwerp. Die doelwitte word geassesseer deur die ondersoek van die geometriese, fisiese en chemiese eienskappe van die aggregaat as ‘n wesenlike materiaal en die vars en verharde betoneienskappe van RCA as ‘n bestanddeel in struktuurbetonontwerp. RCA monsters was geneem by ‘n kommersiele herwinningsfasiliteit wat RCA gebruik om betonsteen eenhede te vervaardig, is op drie verskillende tydperke ingesamel. Hierdie materiaal is herverwerk in die laboratorium om die gradering en die hoeveelheid van fyn materiaal wat nie deur die herwinningsproses beheer is nie. Die RCA was dan gekombineer met NA teen vervangingspersentasies van: 0, 15, 30, 50 en 100 % wat dan gebruik was om die eienskappe van die aggregaat te ondersoek. Daar is vasgestel dat die fisiese eienskappe van die RCA afhanklik van die geometriese eienskappe, met inagneming dat die geometriese eienskappe afhanklik is van die bron en metode van die herwinning van die oorspronklike C&D afval. Dit is gestig dat die chemise eienskappe is afhanklik van die fisiese eienskappe van die RCA. Die RCA is toe gemeng met NA teen dieselfde vervangingspersentasies saam met ander beton bestanddele om beton te produseer wat dan vergelyk kan word met vars en verharde beton eienskappe. Die volgende vars betoneienskappe is ondersoek: insinking, insinking verlies, luginhoud en vars gekompakteerde digtheid. Die volgende verharde betoneienskappe is bestudeer: druksterkte, trek die splintsing van krag, suurstofpermeabiliteit, water sorptiwiteit, chloride geleidingsvermoё, modulus van elastisiteit, krimp en kruip. Die beton eienskappe was nie beduidend beïnvloed deur die insluiting van RCA nie. Volgens die aggregate en beton eienskappe wat in hierdie navorsing ondersoek is, blyk dit dat die volle vervangingswaarde van NA in strukturele beton moontlik is en die volhoubare ontwikkeling van die konstruksiebedryf sal verbeter.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The design of a water supply system relies on the knowledge of the water demands of its specific end-users. It is also important to understand the end-users’ temporal variation in water demand. Failure of the system to provide the required volume of water at the required flow-rate is deemed a system failure. The system therefore needs to be designed with sufficient capacity to ensure that it is able to supply the required volume of water during the highest demand periods. In practice, bulk water supply systems do not have to cater for the high frequency, short duration high peak demand scenarios of the end-user, such as the peak hour or peak day events, as the impact of events is reduced by the provision of water storage capacity at the off-take from the bulk supply system. However, for peak demand scenarios with durations longer than an hour or a day, depending on the situation, the provision of sufficient storage capacity to reduce the impact on the bulk water system, becomes impractical and could lead to potential water quality issues during low demand periods. It is, therefore, a requirement that bulk water systems be designed to be able to meet the peak weekly or peak month end-user demands. These peak demand scenarios usually occur only during a certain portion of the year, generally concentrated in a two to three month period during the drier months. Existing design guidelines usually follow a deterministic design approach, whereby a suitable DPF is applied to the average annual daily system demand in order to determine the expected peak demand on the system. This DPF does not account for the potential variability in end-user demand profiles, or the impact that end-storage has on the required peak design factor of the bulk system. This study investigated the temporal variations of end-user demand on two bulk water supply systems. These systems are located in the winter rainfall region of the Western Cape province of South Africa. The data analysed was the monthly measured consumption figures of different end-users supplied from the two systems. The data-sets extended over 14 years of data. Actual monthly peak factors were extracted from this data and used in deterministic and probabilistic methods to determine the expected monthly peak factor for both the end-user and the system design. The probabilistic method made use of a Monte Carlo analysis, whereby the actual recorded monthly peak factor for each end-user per bulk system was used as an input into discrete probability functions. The Monte Carlo analysis executed 1 500 000 iterations in order to produce probability distributions of the monthly peak factors for each system. The deterministic and probabilistic results were compared to the actual monthly peak factors as calculated from the existing water use data, as well as against current DPFs as published in guidelines used in the industry. The study demonstrated that the deterministic method would overstate the expected peak system demand and result in an oversized system. The probabilistic method yielded good results and compared well with the actual monthly peak factors. It is thus deemed an appropriate tool to use to determine the required DPF of a bulk water system for a chosen reliability of supply. The study also indicated the DPFs proposed by current guidelines to be too low. The study identified a potential relationship between the average demand of an end-user and the expected maximum monthly peak factor, whereas in current guidelines peak factors are not indicated as being influenced by the end-user average demand. / AFRIKAANSE OPSOMMING: Die ontwerp van ‘n watervoorsiening stelsel berus op die kennis van die water aanvraag van sy spesifieke eindverbruikers. Dit is ook belangrik om ‘n begrip te hê van die tydelike variasie van die eindverbruiker se water-aanvraag. Indien die voorsieningstelsel nie in staat is om die benodigde volume water teen die verlangde vloeitempo te kan lewer nie, word dit beskou as ‘n faling. Die stelsel word dus ontwerp met voldoende kapasiteit wat dit sal in staat stel om die benodigde volume gedurende die hoogste aanvraag periodes te kan voorsien. In die praktyk hoef grootmaat water-voorsiening stelsels nie te voldoen aan spits watergebeurtenisse met hoë frekwensie en kort duurtes, soos piek-dag of piek-uur aanvraag nie, aangesien hierdie gebeurtenisse se impak op die grootmaat stelsel verminder word deur die voorsiening van wateropgaring fasiliteite by die aftap-punte vanaf die grootmaatstelsels. Nieteenstaande, vir piek-aanvraag gebeurtenisse met langer duurtes as ‘n uur of dag, raak die voorsiening van voldoende wateropgaring kapasiteit by die aftap-punt onprakties en kan dit selfs lei tot waterkwaliteits probleme. Dit is dus ‘n vereiste dat grootmaat watervoorsienings stelsels ontwerp moet word om die piek-week of piek-maand eindverbruiker aanvrae te kan voorsien. Hierdie piek-aanvraag gebeurtenisse vind algemeen in gekonsentreerde twee- of drie maand periodes tydens die droeër maande plaas. Bestaande ontwerpsriglyne volg gewoonlik ‘n deterministiese ontwerp benadering, deurdat ‘n voldoende ontwerp spits faktor toegepas word op die gemiddelde jaarlikse daaglikse stelsel aanvraag om sodoende te bepaal wat die verwagte spits aanvraag van die stelsel sal wees. Hierdie ontwerp spits faktor maak nie voorsiening vir die potensiële variasie in die eindverbruiker se aanvraag karakter of die impak van die beskikbare water-opgaring fasiliteit op die benodigde ontwerp spits faktor van die grootmaat-stelsel nie. Hierdie studie ondersoek die tydelike variasie van die eindverbruiker se aanvraag op twee grootmaat watervoorsiening stelsels. Die twee stelsels is geleë in die winter reënval streek van die Wes-Kaap provinsie van Suid-Afrika. Die data wat geanaliseer is was die maandelikse gemeterde verbruiksyfers van verskillende eindverbruikers voorsien deur die twee stelsels. Die datastelle het oor 14 jaar gestrek. Die ware maand piekfaktore is bereken vanaf die data en is in deterministiese en probabilistiese metodes gebruik om die verwagte eindverbruiker en stelsel ontwerp se maand spits-faktore te bereken. Die probabilistiese metode het gebruik gemaak van ‘n Monte Carlo analise metode, waardeur die ware gemeette maand spits-faktor vir elke eindverbruiker vir elke grootmaatstelsel gebruik is as invoer tot diskrete waarskynlikheids funksies. Die Monte Carlo analise het 1 500 000 iterasies voltooi om waarskynlikheids-verdelings van elke maand spitsfaktor vir elke stelsel te bereken. Die deterministiese en probabilistiese resultate is vergelyk met die ware maand spits faktore soos bereken vanuit die bestaande waterverbruik data, asook teen huidige gepubliseerde ontwerp spits-faktore, wat in die bedryf gebruik word. Die studie het aangetoon dat die deterministiese metode te konserwatief is en dat dit die verwagte piekaanvraag van die stelsel sal oorskat en dus sal lei tot ‘n oorgrootte stelsel. Die probabilistiese metode het goeie resultate opgelewer wat goed vergelyk met die ware maand piek-faktore. Dit word gereken as ‘n toepaslike metode om die benodigde ontwerp spits-faktor van ‘n grootmaat-watervoorsiening stelsel te bepaal vir ‘n gekose voorsieningsbetroubaarheid. Die studie het ook aangedui dat die ontwerps piek-faktore voorgestel deur die huidige riglyne te laag is en dat dit tot die falings van ‘n stelsel sal lei. Die studie het ‘n moontlike verwantskap tussen die gemiddelde daaglikse wateraanvraag van die eindverbruiker en die verwagte maksimum maand spits faktor geïdentifiseer, nademaal die piek-faktore soos voorgestel deur die huidige riglyne nie beïnvloed word deur die eindverbruiker se gemiddelde verbruik nie.

Thesis (MEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Riprap is commonly used as an erosion protection measure around the world. In some cases, for example when constructing bed arrestors, riprap has to be designed to be stable on steep slopes. The literature shows that the problem of incipient motion is reasonably well understood, but existing hydraulic design methods are found to be largely unreliable. The main objective of this study is to improve the understanding of the different factors affecting incipient motion in order to furnish the prospective design engineer with a reliable method for sizing riprap on steep slopes adequately. Eight existing theories dealing with the threshold of incipient motion are reviewed, of which Liu’s work (1957) seems most promising. Naturally, the required median rock diameter of the riprap is reasonably large (due to the steep slopes), with high particle Reynolds numbers. However, little data is available for these flow conditions. Data collected from 12 large scale laboratory tests carried out for this research indicate that the dimensionless Movability Number is in fact constant for large particle Reynolds numbers. For design purposes, the recommended Movability Number which emerged from this study is 0.18, provided that the steep bed slope is taken into account, and that the theoretical settling velocity is calculated using an accurate drag coefficient and the d90 sieve size. A comparison of the laboratory data with design equations showed that a large variety of results are obtained, which supports the need for this study. Finally, it was shown that a calibrated one dimensional hydrodynamic model can be used by the practicing engineer to extract the hydraulic properties needed for applying Liu’s theory. It was found that the ratio ks/d90 = 0.81 may be applied to estimate the bed roughness for the grading used in this study. / AFRIKAANSE OPSOMMING: Stortklip is ‘n metode wat wêreldwyd gebruik word om erosie te voorkom. In sommige gevalle, byvoorbeeld vir die konstruksie van erosietrappe, moet stortklip teen steil hellings spesifiek ontwerp word om stabiliteit te verseker. Die literatuur beskryf die probleem van aanvanklike beweging redelik goed, maar dit is bevind dat die bestaande ontwerpmetodes grotendeels onbetroubaar is. Die hoofdoelwit van hierdie ondersoek was om die faktore wat beweging van stortklip veroorsaak, beter te verstaan en ‘n betroubare metode te ontwikkel wat ’n ingenieur kan aanwend om stortklipbeskerming wat op steil hellings geplaas word te ontwerp. Agt verskillende metodes wat die begin van beweging beskryf is bestudeer, en dit wil voorkom asof die Liu teorie van 1957 die grootste potensiaal het. As gevolg van die steil hellings wat ondersoek word, is die benodigde klipgroote redelik groot wat weereens die oorsaak is vir ‘n hoë deeltjie Reynolds getal is. In die literatuur kon geen data gevind word vir so ‘n vloeitoestand nie. Daarom is 12 laboratoriumtoetse gedoen en daar is gevind dat die Mobiliteitsgetal redelik konstant is vir groot deeltjie Reynoldsgetalle. Vir onwerpdoeleindes word ‘n Mobiliteitsgetal van 0.18 aanbeveel, met die voorwaarde dat die bodemhelling in ag geneem word, en dat die teoretiese valsnelheid bereken word met die d90 klipgroote en ‘n akkurate sleurkoëffisiënt. Verder is gevind dat die labaratorium data die voorspellings van die bestaande ontwerpvergelykings nie bevredigend pas nie. Dit ondersteun die behoefte vir hierdie studie. Om die bogenoemde bevindings vir praktiese probleme bruikbaar te maak, is daar gewys dat ‘n gekalibreerde een dimensionale hydrodinamiese rekenaarmodel gebruik kan word om die nodige hidrouliese eienskappe te verkry om die Liu teorie toe te pas. Dit is bevind dat die verhouding ks/d90 = 0.81 ‘n goeie benadering vir die hidrouliese ruheid kan voorsien.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Hot Mix Asphalt (HMA) plays a large role in the transportation infrastructure and is used to construct highways, runways, parking areas, foot paths and cycle paths. Asphalt is thus being produced in massive amounts around the world. The latest figures on asphalt production indicate that 1.6 trillion metric tonnes of asphalt are produced annually worldwide. This vast quantity of asphalt produced annually has a significant effect on the environment, economy and the surrounding society. According to Mike Acott from the National Asphalt Pavement Association (NAPA) the key strategy to improve HMA is to continuously strive to improve the health safety and environmental practices of HMA. He also emphasises the importance of engaging improvements and innovation in the design and operation phases of HMA as it will result into more health, safety and environmental benefits. (Acott, 2007) It is thus important to improve the sustainability of HMA as it will be used for generations to come. The purpose of this study is to investigate the potential benefits and risks of applying new technology to the current methods of design and construction of asphalt by the South African asphalt industry. The technologies that are investigated in this study are Warm Mix Asphalt (WMA) technology and the use of Reclaimed Asphalt (RA). WMA is asphalt that is designed to be manufactured at a lower temperature than HMA. RA is the use of recycled asphalt material in Hot Mix Asphalt (HMA) thus replacing virgin aggregate and virgin bitumen with recycled components. Both these technologies can have an effect on the sustainability of HMA. This study investigates the benefits and risks of the integration and application of WMA technology and RA into HMA industry in South Africa. The study uses interviews along with environmental and cost analyses to investigate this integration. The findings show that these technologies have definite environmental and cost benefits and that the magnitude of these benefits cannot be ignored. The current use of these technologies is a cause for concern as they are used in limited projects and limited authorities have warmed up to the use of these technologies. The risks involved in using these technologies are caused by a lack of experience and knowledge of these technologies which is aggravated as there are no standard specifications for their use. It is important that the right strategy is put into place to integrate these technologies into the South African asphalt industry in such a way that minimal risk and monetary losses are achieved. / AFRIKAANSE OPSOMMING: HMA speel 'n groot rol in vervoer-infrastruktuur en word gebruik om paaie, aanloopbane, parkeerareas, voet en fiets paaie te bou. Asfalt word dus wêreldwyd in groot hoeveelhede geproduseer. Die nuutste syfers toon dat 1.6 triljoen kubieke meter asfalt jaarliks wêreldwyd geproduseer word. Hierdie groot hoeveelheid asfalt wat geproduseer word het ‘n beduidende effek op die omgewing, ekonomie en die omliggende gemeenskap. Volgens Mike Acott van die Nasionale Asfalt Plaveisel Assosiasie (NAPA) is die voortdurende strewe om die gesondheids, veiligheids en omgewings impakte van HMA te verminder die sleutel-strategie om HMA te verbeter. Hy beklemtoon ook die belangrikheid om verbeterings en innovering in die ontwerp en bedryf fases van HMA aan te bring wat kan lei tot meer veiligheids, gesondheids en omgewings voordele. (Acott, 2007) Dit is dus belangrik om die volhoubaarheid van HMA te verbeter as dit bewaar wil word vir toekomstige geslagte te kom. Die doel van hierdie studie is om die potensiële voordele en risiko's van die gebruik van nuwe tegnologieë op die huidige ontwerp en konstruksie metodes in Suid-Afrika se asfalt bedryf te ondersoek. Die tegnologieë wat in hierdie studie ondersoek word is Warm Mengsel Asfalt (WMA) en die gebruik van Herwonne Asfalt (RA). WMA is asfalt wat ontwerp is om teen ‘n laer temperatuur as konvensionele HMA vervaardig te word. RA is die gebruik van herwinde asfalt in HMA wat lei tot die besparing van nuwe aggregaat en bitumen. Beide hierdie tegnologieë kan 'n invloed op die volhoubaarheid van HMA hê. Hierdie studie ondersoek dus die voordele en risiko's van die integrasie en gebruik van WMA en RA tegnologie in die HMA-industrie in Suid-Afrika. Die studie maak gebruik van onderhoude asook omgewings en koste impak analises om hierdie integrasie te ondersoek. Die bevindinge in die studie toon aan dat hierdie tegnologie definitief voordelig is vir die omgewing en die ekonomie en dat hierdie voordele groot genoeg is om nie geïgnoreer te word nie. Die huidige gebruik van hierdie tegnologieë is 'n rede vir bekommernis, want dit word slegs in ‘n paar projekte aangewend en daar is slegs ‘n paar owerhede wat die tegnologieë ondersteun. Die risiko's wat betrokke is in die gebruik van hierdie tegnologieë word veroorsaak deur 'n gebrek aan ondervinding en kennis van die tegnologieë wat verder vererger word deur die gebrek aan standaard spesifikasies vir die gebruik daarvan.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Geotextiles perform a number of functions in various applications in civil engineering practise. It is often cost effective and more environmentally friendly versus conventional construction methods. One of the main functions of a geotextile is filtration whereby the geotextile is expected to hold back the soil particles and simultaneously has to allow sufficient water to pass through it. Soils are all different and can be problematic when it comes to designing geotextile filters. One such problematic soil is encountered in KwaZulu- Natal, situated along the east coast of South Africa. The Berea sand is problematic as it can highly variable in its engineering properties over a small area. Geotextiles are becoming more and more common practice in South Africa and little is known about the filtration performance of commercially available geotextiles in conjunction with Berea sand. Local guidelines that are available are out of date and do not provide enough information to assist design engineers in decision making. Many international guidelines are available and it is difficult to choose which one is best suited to Berea sands. This primary objective of this study is to investigate the filtration performance of four variants of commercially available geotextiles and three variants of Berea sand. The applicability of some of the international filter design criteria will also be assessed. The soil to geotextile compatibility testing was carried out as per ASTM D5101 (2006) - Standard Test Method for Measuring the Soil-Geotextile System Clogging Potential by the Gradient Ratio. In total 12 permutations were executed. The results showed that only 5 test permutations met the gradient ratio and permeability criteria. The test results also conclude that the permeability is just as important as the gradient ratio. Thick geotextiles should be considered when used as filters in Berea sands. The available international geotextile filter design criteria were assessed and all showed poor correlation between laboratory results and suggested criteria. Designing geotextile filters in conjunction with Berea reds is challenging and it is recommended that design engineers perform laboratory performance testing in conjunction with their designs. / AFRIKAANSE OPSOMMING: Geotekstiele verrig vir 'n aantal funksies in verskeie programme in die siviele ingenieurswese praktyk. Dit is dikwels meer koste-effektief en omgewingsvriendelik, teenoor konvensionele konstruksie metodes. Een van die belangrikste funksies van 'n geotekstiel is filtrasie, waardeur van die geotekstiel verwag word om van die grond terug te hou, en gelyktydig genoeg water daardeur te laat vloei. Grond verskil en dit kan problematies wees wanneer dit kom by die ontwerp van geotekstiel filters. Een so ‘n problematiese grond kom voor in KwaZulu-Natal, geleë langs die ooskus van Suid-Afrika. (Die) Berea sand is problematies, want dit verander geweldig baie ten opsigte van ingenieurseienskappe oor 'n redelike klein area. Gebruik van geotekstiele word al hoe meer ‘n algemene praktyk in Suid- Afrika, terwyl min bekend is oor die filtrasie prestasie van kommersieel beskikbare geotekstiele in samewerking met Berea sand. Plaaslike riglyne wat beskikbaar is, is verouderd en onvoldoende inligting is beskikbaar aan ontwerpingenieurs vir besluitneming . Baie internasionale riglyne is beskikbaar en dit is moeilik om te besluit watter een die beste van toepassing is vir Berea sand. Die doel van hierdie studie is om die filtrasie prestasie van vier modelle van kommersieël beskikbare geotekstiele en voorbeelde van drie soorte Berea sand te ondersoek. Die toepaslikheid van 'n paar van die internasionale filter ontwerp kriteria sal ook beoordeel word. Die toetsing van grondverenigbaarheid met geotekstiel is uitgevoer soos aangedui in ASTM D5101 (2006 ) – Standaard Toets Metode vir die meet van die grond-Geotekstiel verstopping potensiëel deur die gradient verhouding. In totaal is 12 permutasies uitgevoer. Die resultate het getoon dat slegs 5 toetspermutasies beide gradiënt verhouding en permeabiliteit kriteria bevredig het. Dikker geotekstiele word ook aanbeveel vir gebruik as filters in Berea sand. Van die toets resultate kan ook afgelei word dat die permeabiliteit net so belangrik soos die gradiënt verhouding is. Beskikbare internasionalegeotekstiel filter ontwerp kriteria is nagegaan en al die metodes het swak korrelasie tussen laboratorium resultate en die voorgestelde kriteria getoon. Om geotekstiel filters in samewerking met Berea Reds te ontwerp is 'n uitdaging en dit word aanbeveel dat ontwerpingenieurs laboratorium prestasietoetsing in samewerking met hul ontwerpe uitvoer.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Variations made to the original scope of works are part of construction projects. Varying the scope of works has a cost and time impact, also referred to as the direct impact of V.Os. The direct impact is generally well understood by both contractor and client. Over and beyond the direct impact, V.Os also have a secondary impact on a project. Unlike the direct impact, the secondary impact appears not to be well recognised and managed by South African contractors. The principal aim of the research is to understand the secondary impact of V.Os. Based on this understanding, it then aims to give guidelines and recommendations to assist contractors to manage the secondary impact of V.Os. A variety of methods are used in this thesis. It includes literature review, questionnaire surveys and interviews. The qualitative analysis consists out of a pre-investigation which provided insight on how contractors deal with the secondary impact of V.Os. The JBCC and the GCC were analysed, which provided an understanding on how the contract deals with V.Os and its secondary impact. A definition was developed for the secondary impact. Key terms in the definition were analysed that assist with its understanding. Through means of a detailed literature review of relevant literature, a collection of delay and disruption events were identified that could be triggered by V.O. Studies are presented that proves V.Os cause a loss of productivity on construction projects. A comprehensive and systematic overview was given that explains the secondary impact of V.Os on construction projects. The main events discussed in the overview were validated for the South African contractor through means of interviews conducted with 2 contractors and questionnaires sent out to 44 individuals. It was found that in general, some South African contractors have accepted the secondary impact as part of construction projects. Contracts do not explicitly consider the secondary impact of change, nor does it provide clear guidelines as to how it should be addressed by the parties in contract. It was concluded that the secondary impact is unforeseen loss of productivity on the unchanged work due to the synergistic effect of the disruption caused by a multitude of V.Os (Jones, 2001, Hanna, 2004 and Ibbs, 2005). The secondary impact is an impact on human factors such as morale, self-esteem, motivation and the cause of difficult working conditions. It is a disruption that prevents project activities and events from starting and ending at the planned time and also prevents contractors from executing activities as planned. The cost due to the secondary impact is a combination of increased labour cost and also the increased cost of completing the unchanged work. It is clear that to pro-actively manage the secondary impact of V.Os will require the cooperation from the contract, the contractor and the client. In short contractors will need to understand the secondary impact, be aware of and prepared for delay and disruption events, keep record of the impact, monitor and control labour productivity and maintain a good relationship with the client. / AFRIKAANSE OPSOMMING: Veranderinge aan die oorspronklike omvang van die werk is deel van konstruksie-projekte. Wanneer die omvang van die oorspronklikke werke verander word, het dit ‘n tyd en koste implikasie tot gevolg. Dit word na verwys as die direkte impak van veranderringe. Die direkte impak word oor die algemeen goed verstaan deur beide die kontrakteur en die kliënt. Bo en behalwe die direkte impak, het variation orders (V.Os) ook 'n sekondêre impak op 'n projek. In teenstelling met die direkte impak, word die sekondêre impak waarskynlik nie goed erken en bestuur deur die Suid-Afrikaanse kontrakteurs nie. Die hoofdoel van die navorsing is om die impak van sekondêre V.Os. te verstaan. Op grond van hierdie begrip, het dit ten doel om riglyne en aanbevelings te gee wat kontrakteurs kan help om die sekondêre impak van V.Os. te bestuur. 'n Verskeidenheid van metodes word in hierdie tesis gebruik. Dit sluit in literatuurstudies, vrae-lys opnames en onderhoude. Die kwalitatiewe ontleding bestaan uit 'n voor-ondersoek wat insig verskaf oor hoe kontrakteurs die sekondêre impak van V.Os hanteer en beleef. Die JBCC en die GCC is ontleed, met die doel om te verstaan hoe die kontrak V.Os en hul sekondêre impak hanteer. 'n Definisie is ontwikkel vir die sekondêre impak. Sleutelterme in die definisie is ontleed wat help met die begrip. Deur middel van 'n omvattende literatuuroorsig van relevante literatuur, is 'n versameling van die vertraging-en ontwrigtings gebeure geïdentifiseer wat deur V.Os veroorsaak kan word. Studies wat bewys dat V.Os 'n afname in produktiwiteit van konstruksie-projekte veroorsaak, is geraadpleeg. 'n Omvattende en sistematiese oorsig word gegee wat die sekondêre impak van V.Os op konstruksie-projekte verduidelik. Die belangrikste gebeurtenisse wat in die oorsig beskryf word, is bekragtig vir die Suid-Afrikaanse kontrakteur deur middel van onderhoude wat met 2 kontrakteurs gevoer is en vraelyste wat uitgestuur is aan 44 individue. Daar is gevind dat in die algemeen, aanvaar sommige Suid-Afrikaanse kontrakteurs die sekondêre impak as deel van konstruksie-projekte. Kontrakte bevat nie duidelike riglyne wat verduidelik hoe kontrakteurs en kliënte die sekondêre impak van V.Os moet hanteer en aanspreek nie. Daar is tot die gevolgtrekking gekom dat die sekondêre impak ‘n onvoorsiene verlies van produktiwiteit op die onveranderde werk is. Dit is die gevolg van die sinergistiese effek van ontwrigting wat veroorsaak word deur 'n menigte van V.Os (Jones, 2001, Hanna, 2004 en Ibbs, 2005). Die sekondêre uitwerking is 'n impak op menslike faktore soos moraal, selfbeeld, motivering en die oorsaak van die moeilike werksomstandighede. Dit is 'n ontwrigting wat verhoed dat die aktiwiteite en gebeure van die projek begin of eindig op die beplande tye. Ook verhoed die sekondêre impak dat die kontrakteurs aktiwiteite uitvoer soos wat vooruit beplan was. Die koste as gevolg van die sekondêre impak is 'n kombinasie van verhoogde arbeidskoste en ook die verhoogde koste om onveranderde werk te voltooi. Dit is duidelik dat die samewerking van die kontrak, die kontrakteur en die kliënt noodsaaklik is om die sekondêre impak van V.Os op ‘n pro-aktiewe wyse te bestuur. Kortliks, vir kontrakteurs om die sekondêre impak te bestuur, het hul nodig om dit te verstaan, om bewus te wees van en voorbereid te wees vir die vertraging-en ontwrigtings gebeure wat plaasvind, rekord moet gehou word van die impak, die produktiwiteit van arbeid moet gemonitor en beheer word en 'n goeie verhouding met die kliënt moet nagestreef word.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Since the intervention of the Competition Commission and the abolition of the mandatory use of the government gazetted Engineering Council of South Africa (ECSA) fees scale, engineering services consultants in South Africa have been competing based on price for engineering contracts in both the public and private sectors. Discounts benchmarked against ECSA professional fees scale demanded by clients have resulted in declines in professional fees over the years. The capacity to deliver professional services that are of such high quality that it meets the client’s expectation, professional and ethical standards when working at low fees is one of the biggest challenges facing consulting professionals today. This research studied the risks encountered by civil and structural engineering services consultants and the impact of discounted professional fees on their risk exposure. The study included a review of literature, discussions with practicing engineers and a questionnaire based survey. A total of 23 practicing consulting engineers representing small, medium and large consulting engineering firms participated as respondents in the questionnaire survey. The literature review identified project and organisational level risks particular to civil and structural engineering services consultants. The study compiled information on the discounting practices of civil and structural engineering services consultants in South Africa. It is found that the practice of discounting is widespread, affecting small, medium and large consulting firms. The range of discounts offered in the industry results in a significant decrease in the fee scale recommended by ECSA for various engineering project types. Respondents identified the primary reasons why they are forced to offer discounts and identified project and organisational risks most impacted by discounted fees in an order of perceived importance to them. Financial loss on the project, inadequate supervision and quality control on site and inability to perform value engineering were identified as project risks with the most impact on respondents’ organisation. At the organisational level human resource issues such as training and mentoring of young engineers, ability to attract and retain quality/experienced staff and overall business sustenance were identified as risks most impacted by discounted fees. Measures adopted by respondents to mitigate risk associated with discounted fees on project were also identified and recommended. / AFRIKAANSE OPSOMMING: Sedert die ingryping van die Kompetisie Kommissie en die afskaffing van verpligte fooie soos gepubliseer deur die regerings koerant en Ingenieurs Raad van Suid Afrika (IRSA), het ingenieurs konsultante in Suid Afrika meegeding gebaseer op die prys van ingenieurs kontrakte in beide die publieke en private sektore. Afslag wat gemeet word teen professionele skale van ECSA word vereis deur kliënte. Onetiese tender gedrag deur kliënte en raadgewers het gelei tot ʼn daling in professionele fooie oor die jare. Die kapasiteit om professionele dienste te verskaf, wat van ʼn hoë kwaliteit is, kliënte se verwagtinge bereik en professionele en etiese standaarde bereik teen lae koste is een van die grootste uitdagings vir professionele raadgewende ingenieurs in vandag se mark. Hierdie tesis bestudeer die risiko’s wat siviele en strukturele raadgewende ingenieurs ondervind, asook die impak wat afslag van professionele fooie het in terme van die blootstelling van risiko’s. Hierdie studie behels ʼn literatuur studie, gesprekke met ingenieurs in die praktyk en ʼn vraelys opname. ʼn Totaal van 23 raadgewende ingenieurs wat klein, medium en groot raadgewende ingenieurs instansies verteenwoordig het deelgeneem aan die vraelys opname. Die literatuur studie het projek risiko’s en risiko’s op die organisasie vlak geïdentifiseer wat veral verband hou met siviele en strukturele raadgewende dienste. Die studie het informasie gegenereer oor die dalende uitvoering van siviele en strukturele raadgewende dienste in Suid-Afrika. Dit is bevind dat die beginsel van afslag in die algemeen klein, medium en groot raadgewende firmas beïnvloed. Die omvang van die afslag wat aangebied word in die ingenieurs bedryf het gelei tot ʼn beduidende afname in die fooi skaal wat aanbeveel word deur ECSA vir die verskeie ingenieurs projek tipes. Die verskeie deelnemers van die studie het gedui dat die primêre rede hoekom hulle gedwing word om afslag aan te bied en projek en organisasie risiko’s identifiseer, is omdat afslag fooie ʼn voorafgestelde belang is vir hulle. Finansiële verliese op ʼn projek, onvoldoende toesig, kwaliteitsbeheer en die onvermoë om hoë gehalte ingenieurswese toe te pas was geïdentifiseer as die projek risiko’s wat die meeste invloed het op die deelnemers se organisasies. By die organisasie vlak was menslike hulpbronne, soos opleiding en die mentorskap van jong ingenieurs, die vermoë om kwaliteit of ervare personeel te trek en te behou, en die algehele besigheid lewensmiddele geïdentifiseer as risiko’s wat die meeste beïnvloed word deur afslag fooie. Maatreëls wat aangeneem is deur deelnemers aan die studie om risiko’s wat verband hou met afslag fooie van ʼn projek te versag is geïdentifiseer en aanbeveel.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The aim of this project is to study the structural design and costing of various designs of tall wind turbine towers and the associated foundations in a South African context. Speci c design guidelines are proposed for the design of tubular steel, concrete and concrete-steel hybrid towers and foundations for hub heights of 80, 100 and 120m. Additionally, a conclusion will be made as to whether the concrete and hybrid towers are a viable alternative to steel towers at higher hub heights. To accomplish this, three of each type of tower (steel concrete and hybrid) and their foundations were designed according to the relevant design standards. The designs were then veri ed using the Abaqus nite element software. The costs of the designs for a South African environment were subsequently calculated according to the increases in material cost, as a function of the increase in hub height. It was found that for the chosen design assumptions, the foundations for the concrete and hybrid towers are less material intensive, and therefore cheaper, than the steel towers. The material costs of the concrete and hybrid towers were also shown to be lower than the material costs of the steel towers, especially at hub heights of 100 to 120m. For the circumstances in this project, it was found that an increase in hub height causes an increase in energy generation of 3.52 and 6.28 percent for 80m to 100m and 80m to 120m hub heights, respectively. It is therefore deduced that, given the trends in the design and cost associated with increasing hub heights, the concrete and hybrid towers become viable alternatives to the conventional steel towers at hub heights of 100 to 120m in height. / AFRIKAANSE OPSOMMING: Die doel van hierdie projek is om die strukturele ontwerp en koste van verskillende soorte ho e wind turbines en die toepaslike fondamente vir 'n Suid-Afrikaanse konteks te bestudeer. Spesi eke riglyne word voorgestel vir die ontwerp van silindervormige staal, beton en beton-staal hibriede torings en fondamente vir naafhoogte van 80, 100 en 120m. 'n Gevolgtrekking oor die lewensvatbaarheid van die beton en hibriede torings, in vergelyking met die gewone staal torings teen naafhoogte van 100 tot 120m sal ook gemaak word. Met die bogenoemde as doel, is drie van elke tipe toring (staal, beton en hibried) en hul fondamente volgens die toepaslike standaarde ontwerp. Daarna is die integriteit van die ontwerpe getoets en bevestig deur gebruik van die Abaqus eindige-element-metode sagteware. Ten slotte, die kostes van die ontwerpe vir 'n Suid Afrikaanse omgewing is bereken en die verandering in materiaalkoste uitgedruk as 'n funksie van die verhoging in naafhoogte. Daar is gevind dat, vir die aannames in die ontwerp, die fondamente van die beton en hybrid torings minder materiaal benodig, en dus goedkoper is as die staal torings. Verder, is die materiaalkoste van die beton en hibriede torings laer as die van die staal torings, veral vir naafhoogtes van 100 tot 120m. Verder, is daar vir die omstandighede in hierdie projek gevind dat ho er naafhoogtes stygings in energie-opwekking van 3.52 persent vir naafhoogte stygings van 80m tot 100m, en stygings van 6.28 persent vir naafhoogte stygings van 80m tot 120m lewer. Daar word dus tot die gevolgtrekking gekom dat, gegewe die tendense in die ontwerp en materiaal koste wat verband hou met die verhoging van die naafhoogte, die beton en hibriede torings 'n lewensvatbare alternatief vir die konvensionele staal torings vir naafhoogtes van 100 tot 120m word.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Exponential growth of the global wind turbine market has led to a significant increase in the capacity of wind turbine generators. Modern turbines require higher support structures as higher wind speeds combined with longer blades are necessary to increase their generating capacity. The standard 80-90 m tower is thus not economically viable anymore. Transportation logistics of large steel towers has led to concrete towers becoming a viable option. There are currently no design codes dealing exclusively with the design of concrete wind turbine towers. The aim of this project is to investigate and highlight important aspects of the design process of a normally reinforced high strength concrete wind turbine tower. The tower was designed using nonlinear finite element modelling as a design tool to accurately design the tower for various loads and load cases. An analytical design method was developed that can be used in the preliminary design stage. Finally, the importance of the soil-structure interaction was investigated through a sensitivity analysis. It was found that the formation of cracks greatly affected the stiffness of the structure and that the reduction in stiffness increased the deflection significantly. It was also found that a structure that has sufficient strength to resist the ULS loads may not necessarily comply with the maximum deflection limit for the SLS. The concrete strength class required was not only determined by the maximum compression stress the concrete would experience, but also by the stiffness required to ensure that the tower frequency is within the turbine’s working frequency. The dynamic behaviour of the tower was also affected by the formation of cracks. The fundamental frequency of the tower was reduced by 46% after the SLS loads were applied. It was found that the soil preparation for the foundation plays a vital role in ensuring that the tower frequency is not reduced to a level where it falls outside the turbine working frequency. / AFRIKAANSE OPSOMMING: Die eksponensiële groei van die globale wind turbine mark het gelei tot ʼn beduidende toename in die opwekkingskapasiteit van wind turbine kragopwekkers. Moderne turbines benodig hoër ondersteuningstrukture om hulle opwekkingskapasiteit te verhoog en daarom is die standaard 80-90 m toring nie meer geskik nie. Die vervoer logistiek van groot staal torings het daartoe gelei dat beton torings ʼn lewensvatbare opsie geword het. Daar is huidiglik geen ontwerpkodes wat uitsluitlik handel met die ontwerp van beton wind turbine torings nie. Die doel van hierdie projek is om die ontwerp proses van ʼn bewapende hoë sterkte beton wind turbine toring te ondersoek en belangrike aspekte uit te lig. Die toring word ontwerp deur ʼn nie-liniêre eindige element model te gebruik as ʼn ontwerp hulpmiddel, om die toring akkuraat te ontwerp vir verskeie laste en lasgevalle. ʼn Analitiese ontwerpmetode is ontwikkel wat gebruik kan word in die voorlopige ontwerpfase. Laastens is die grond-struktuur interaksie ondersoek deur ʼn sensitiwiteitsanalise. Daar is gevind dat die vorming van krake die styfheid van die struktuur aansienlik beïnvloed en dat die vermindering in styfheid die defleksie beduidend vermeerder. Daar is ook gevind dat ʼn struktuur wat voldoende sterkte het om die uiterste lastoestande te weerstaan, nie noodwendig voldoen aan die maksimum defleksiegrens vir die diens lastoestande nie. Die beton sterkte klas wat benodig is, is nie net bepaal deur die maksimum druk spanning wat die beton sal ondervind nie, maar ook deur die styfheid wat vereis word om te verseker dat die toring se frekwensie binne die turbine se werksfrekwensie val. Die dinamiese gedrag van die toring is ook beïnvloed deur die vorming van krake. Die fundamentele frekwensie van die toring is verlaag met 46% nadat die diens lastoestande toegepas is. Daar is gevind dat die grond voorbereiding vir die fondasie ʼn belangrike rol speel om te verseker dat die toring se frekwensie nie verlaag word tot ʼn vlak waar dit buite die turbine se werksfrekwensie val nie.

No abstract available. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 1973.