Dissertation (PhD)--Stellenbosch University, 1996. / One copy microfiche. / Some digitised pages may appear illegible due to the condition of the original microfiche. / ENGLISH ABSTRACT: The present network of now gauging stations in South Africa has grown from isolated observations on an ad extensive is to an extensive network of stations across the country. Standardised gauging stations to suit local conditions have been developed which include purposely desigll4:d compound weirs. Nearly all. compound gauging weirs In South Africa have. for practical reasons. been constructed without dividing walls. thus deviating lr',:.n the standards set by the British Standards Institution (1981). Uncertainty about the accuracy of calibration of such structures had to be darifi,ed and. where ~cessary. adjustments had to be made to existing calibration formulae in order to compensate for the de,,·iations. It was also necessary to determine whether the accuracies that could be attained were adequate in terms of the potential financial implications of inaccuracies. It has thus become necessary to re-evaluate the calibration of these structures which consist of mainly compound Crump .md sharp-crested weirs. Selected flow l"t'Cords were analysed and the data wa.\ used to determine the impact of errors on the required capacities of reservoirs. This wa., done in an anempt to provide guidelines for the accuracy required in flow records. An31ysing a single application of a flow record cannot provide guidelines for the required accuracy of a flow record and thus the gauging of flow. Although no general conclusions can be drawn. it appears thal the benefits arising from an improvement in the accuracy of a flow record are proportionally greater than the percentage improvement in accuracy. Three-dimensional flow conditions exist either upstream or downstream of the point of stage measurement depending on the presence or absence of diViding walls at a compound gauging weir. The existing calibro1tion theory does not account for the influences of three-dimensional flow conditions and a.-'isociatcd energy losses in the determination of the upstream total energy head. Hydraulic model tests were thus undenaken to detemline the magnitude of the resulting energy losses. New techniques were developed to compensate for these energy losses in the calibration theory of compound gauging weirs. Application of the new calculation techniques to rate compound weirs using a single point of stage measurement results in improvements in accuracy. It was found that compound weirs without dividing walls can be rated to greater levels of accuracy than weirs with dividing walls, where stage measurements are taken at a single point / AFRIKAANSE OPSOMMING: Die huidige nc!werk van vloclmectpumc III SUld-Afnka hel gegroei van gc'isoleerde waamemings op 'n ad hoc basis, tot 'n uitgebrcldc nctwerk. van meetpunte vcrsprei oor die hele land, Standaard mcetstruktuure aangepas vir plaaslike omstandighede is ontwikkei en sluit in doelgeboudc saamgestelde mcetstrukture. Byltans aile saamgestelde mcetstruklure in Suid-Afrika is weens praktisc oorwegings opgerig sonder verdeelmure, wal afwyk van die standaarde gestel deur die British Standards Institution (1981). Onsekerhede aangaande die akkuraathcid ,'an die kaJibrasie van sulke slrukture moes opgekJaar word en unpassjngs un die beSlaande leorie moes gedoen word om hier'OOf te kompenseer. iodien nodig. Oil was ook nodig om va~ Ie s,tel of akkuraathede Waf hulbaar is voldoende is, met inagneming Vlll poIensi~1c finamiitle implikasies van onakkuruthede. Oit hel dus nodig gcword om die bestaandc kaJibra.liic van saamgestelde meetstrukture. hoofsaakJik Crump en sterpkroin meetwaJle, Ie hcr·cval~r. Seleere vloei:rekords is ontl~ en die data is gcbruik om die impak van foule ~ bepaal op die berekende k.apasitei~ van opgaardamme. Oil IS gedoen in 'n poging om riglyne neer te Ie rakende die akkuraatheid verlang in 'n vloeirekord. Die ontleding van '0 enkele loepassing van 'n vloeirekord lewer nie genoegsame data om riglyne vas Ie stell. "ir die verlanp akkuraalheid van 'n vloeirekord of vloeimeling nie. AlhoeweJ geen duidelike riglyne hieruii vOilr1spruit nie. kom dit voor asof die voordele verkry uit '0 verbetering io die akkuraatheid van 'n vloeirekord in verhouding groter is as die vcrmiodering in die vloeimetingsfout. Drie-dimensionele II'loeitoeslande bestaan of stroomop of stroomaf van die punt van watervlakmeting, afl1iangende van die 'cenwoordigheid of afwesigheid van vcrdeelmure by 'n saamgestclde meetstlruktuur. Die beslaande kalibrasieleorie maak nie voorsiening vIr die invloed van drie-dimensionele vloeitoestande en die gepaardgaande energieverlicse op die bepahng van die totale stroomop energiehoogte nie. Hidrouliese mode1tor: sc is ondemeem om die omvang van die resulterende energieverliese vas te ste!. Nuwe tegnieke in die kaJibrasieteorie vir saamgestelde strukture is ontwikk.e1 0:t1 tc kompenseer vir hierdie energieverliese. 'n Verbc:tcde akkuraatheid word verkry wanneer die nuwe tegniek toegepas word op die kalibrasie van saamge~telde meetstrukture met 'n enkele punt van watervla.kmeting. Daar is gevind daR saamgestelde meetstrukture sonder verdeelmure illurater gekalibn:er lean word. as suuktt.Rmet vcrdeelmure waar walervlakke slegs by 'n enkclc punt gemeet word.

Thesis (PhD (Civil Engineering))--Stellenbosch University, 1986. / ENGLISH ABSTRACT: This dissertation presents the development process of a wind damage and disaster management support model for South Africa. Several aspects of wind damage are analysed. The impact of wind disasters on human habitat is highlighted by providing selected data of loss due to such events. This is followed by a comprehensive review of relevant research, carried out locally and internationally. The role and relevance of wind loading codification is discussed. The factors influencing wind damage are identified and their applicability to South African conditions is evaluated. An outline of a database of wind damage in South Africa which has been developed during the course of the project is presented. Selected statistics derived from this database are presented. A probabilistic model for assessing wind damage in South Africa is proposed. The model is based on the spatial principle of occurrence of strong wind events. A 'first approximation' division of the country into zones where various types of wind events occur and the characteristics of their generic footprints (i.e. distribution of wind speeds) are developed. The risk model procedure also takes the distribution of wealth, and the vulnerability of the built environment into account. / AFRIKAANSE OPSOMMING: Hierdie verhandeling bied die ontwikkelingsproses vir 'n hulpmodel vir windskade en rampbestuur vir Suid-Afrika aan. Verskeie aspekte van windskade word ontleed. Die invloed van windskade op woongebiede word beklemtoon deur die aanbieding van geselekteerde data oor relevante plaaslike en internasionale navorsing. Die rol en toepaslikheid van windbelasting in ontwerpkodes word bespreek. Die faktore wat windskade beinvloed, word geidentifiseer en die aanwendbaarheid onder Suid-Afrikaanse omstandighede word beoordeel. 'n Beskrywing van n databasis vir windskade in Suid'-Afrika, wat tydens die projek saamgestel is, word aangebied. Sekere statistiek wat uit die databasis afgelei is, word voorgelê. n Statistiese model vir die beraming van windskade in Suid-Afrika word voorgestel. Die model is gebaseer op die ruimtelike beginsel van voorkoms van sterk-wind-gebeurlikhede. 'n "Eerste benadering" - indeling van die land in streke waar verskillende soorte windgebeurlikhede voorkom en hulle karakteristieke kenmerke (bv. verspreiding van windspoed) is ontwikkel. Die werkwyse vir die risikomodel neem die verdeling van rykdom en die kwesbaarheid van die beboude omgewing in ag.

Thesis(PhD (Civil Engineering))-- University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Bitumen based road surfacing seals and asphalt wearing courses have been used by society's Engineers "to counter the damage to the existing unsurfaced roadways by the newly developed automobile with its rubber driving wheels" since the early 1900's. Early experiments were conducted with both tar and bitumen to find a suitable material to alleviate the situation, and ongoing research has been carried out through the past century and into the new millennium, throughout the world, examining improvements, from materials used, to design and construction methods. However, there is still much to be understood, improved and refined, when considering road surfacing seal design. Pavement designers have the choice of utilizing either an asphalt (graded aggregate remanufactured with a bitumen binder and applied as a complete product) or a surfacing seal (including variations of bitumen binder sprayed onto the road surface, with the addition of single size stones, either in one or two layers of binder and aggregate, i.e. single or double seals) as a pavement wearing course. Current road surfacing seal design practice depends on empirical analysis and experience, being primarily a volumetric based assessment of bitumen application. This research project assesses South African seal design philosophy, investigates design areas where review or updating is required to accommodate changing bitumen sources and types, and traffic loading. Seal performance criteria are examined, with the development of a matrix of influences on seal performance. Using this, the need for a seal design method based on mechanistic material properties is proposed, and the prototype example of such a numerical model using finite element method is presented. To contribute further towards a performance related seal design method, the feasibility of modelling of road surfacing seals using mechanistic principles was examined. The potential of developing failure and fatigue criteria or relationships to enable assessment of the expected seal performance, with inclusion of different component material characteristics and variations, varying traffic and environmental conditions, was also examined. From assessment of literature, and understanding of the components of the seal, pavement, and influencing factors, a choice of numerical model of seal performance was made. The Finite Element Method (FEM) Analysis was selected for the purpose of modelling seal performance. The model was developed to enable examination of the interaction of individual seal components (i.e. stone and bitumen), at micro-mechanic scale. The prototype 3-dimensional numerical seal model was undertaken in 2002 and 2003 at Technical University Delft, using the CAPA research program. On the basis of the linear calculations the developed numerical prototype model is able to provide insight into seal behaviour and distinction between mechanical (seal geometry) and chemical (components) seal aspects, and insight into stress and strain development in the different seal types. Simulations of different seal, environmental and traffic scenarios are provided to demonstrate the potential of the model (excluding seal aggregate interlock and embedment effects at prototype stage). In order to provide data for the verification of the prototype numerical model, and to further contribute to the development of a performance related seal design method, performance tests were developed, with a new tool for assessment of comparative seal performance using the Model Mobile Load Simulator Accelerated Pavement Testing apparatus. The performance of each different seal binder type - Penetration grade Mumen, SBS, SBR, EVA and Bitumen Rubber - was undertaken. A methodology for the assessment of in-service seal performance was developed, and the performance of the respective seals reported. The results of this examination showed that each binder type has its unique contribution to seal performance. These new performance tests will be able to assist designers in the added determination of the fundamental binder properties on seal performance, and the seals' ability to contribute to the overall performance of the pavement. An additional comparative performance test method was developed to enable assessment of the effect of ageing and moisture, to complement the MMLS results. In summary, the performance testing has assisted in identifying the critical parameters a seal designer should consider during the design process. From this research, it is evident that the current seal design method requires further development to able designers to predict the effect of: Varying axle loads, tyre pressures and design speed; Varying characteristics of the different binders, (i.e. temperature - viscosity relationships, adhesion and visco-elastic behaviour); on the performance of seals. The major areas for suggested improvement in current seal design methods towards a performance based design method are: inclusion of variable traffic load and environmental characteristics, including temperature and moisture influences, and inclusion of mechanistic material characteristics into the design methodology. / AFRIKAANSE OPSOMMING: Bitumengebaseerde padoppervlakseellae en asfaltslytlae is sedert die 1900's deur ingenieurs gebruik as teenwig teen die skade wat die pas ontwikkelde voertuig met sy rubberwiele aan bestaande ryvlakke sonder oppervlakbehandeling aangerig het. In vroeëre eksperimente wat daarop gemik was om 'n geskikte materiaal te vind om die probleem teen te werk, is 'n kombinasie van teer en bitumen gebruik. Sedertdien word voortgesette navorsing steeds wêreldwyd gedoen om verbeterings te ondersoek, nie net ten opsigte van materiale nie maar ook ontwerp- en konstruksiemetodes. Wat die ontwerp van padoppervlakseëling betref is daar egter heelwat wat reg begryp, verbeter en verfyn moet word. Plaveiselontwerpers het die keuse om of 'n asfalt te gebruik (gegradeerde aggregaat voorafvervaardig met 'n bitumen bindmiddel en aangewend as 'n klaarproduk), of 'n oppervlakseël (een laag of twee lae [m.a.w. enkel- of dubbelseël] bitumen bindmiddel met aggregaat [enkelgrootte klippies] bygevoeg, gespuit op die padoppervlak). In die praktyk berus die ontwerp van padoppervlakseëling tans op empiriese analise en ervaring (wat hoofsaaklik 'n volumetriesgebaseerde assessering van die aanwending van bitumen is). Hierdie navorsingsprojek doen 'n waardebepaling van die Suid-Afrikaanse filosofie van seëlontwerp, en ondersoek ontwerpterreine wat hersiening of bywerking benodig om vir veranderende bitumenbronne en -tipes, asook verkeerslading, voorsiening te maak. Met die ontwikkeling van 'n matriks van die invloede op seëlprestasie is die kriteria vir seëlprestasie ondersoek. Op grond daarvan word aangevoer dat daar 'n behoefte is aan 'n seëlontwerpmetode gebaseer op die meganistiese eienskappe van materiaal, en word 'n voorbeeld van 'n numeriese modelprototipe wat die eindige-element-metode gebruik, voorgelê. Ten einde 'n verdere bydrae te lewer tot die ontwikkeling van 'n prestasiegerigte seëlontwerpmetode, is die uitvoerbaarheid van die modellering van padoppervlakseëllae gebaseer op meganistiese beginsels, ondersoek. Daar is ook ondersoek ingestel na die potensiaal vir die ontwikkeling van kriteria vir die vasstel van mislukking en vermoeidheid of verhoudinge wat die assessering van die verwagte seëlprestasie (ingesluit die verskillende kenmerke en variasies van seëlkomponentmateriaal en wisselende verkeers- en omgewingsomstandighede) moontlik kan maak. Met oorweging van die bestudeerde literatuur en 'n begrip van die komponente van seël, plaveisel en inwerkende faktore, is 'n keuse van 'n numeriese model vir seëlprestasie gemaak. Die eindige-element-metode (Finite Element Method [FEM]) is gekies as die analitiese metode vir die modellering van seëlprestasie. Die model is ontwikkel om die ondersoek van die interaksie tussen individuele seëlkomponente (klip en bitumen) op mikromeganiese skaal moontlik te maak. Die ontwikkeling van die driedimensionele, numeriese, model-seëlprototipe is tussen 2002 en 2003 by die Delft Tegniese Universiteit gedoen, met gebruikmaking van die CAPA-navorsingsprogram. Wat lineêre berekenings betref, kan die ontwikkelde numeriese modelprototipe 'n insig gee in seëlgedrag en in die onderskeid tussen aspekte van seëlgeometrie (meganies) en seëlkomponente (chemies), asook in die spanning- en vervormingsontwikkeling van die verskillende tipes seël. Simulasies van verskillende seël-, omgewings- en verkeerscenario's word voorgestel om die potensiaal van die modelprototipe te demonstreer. Met die oog daarop om data vir die verifikasie van die numeriese modelprototipe te voorsien, en om verder tot die ontwikkeling van 'n prestasiegerigte seëlontwerpmetode by te dra, is prestasietoetse, met 'n nuwe instrument vir die assessering van vergelykende seëlprestasie met behulp van die Model Mobile Load Simulator Accelerated Pavement Testing apparaat, ontwikkel. Die prestasie van elke verskillende tipe seëlbindmiddel- penetrasiegraad bitumen, SBS, SBR, EVA en bitumenrubber - is getoets. 'n Metodologie vir die assessering van die ingebruiksprestasie van seëllae is ontwikkel, en daar is verslag gedoen oor die prestasie van die verskillende seëllae. Die resultate van die ondersoek het getoon dat elke tipe bindmiddel 'n eie unieke bydrae tot die prestasie van die seël lewer. Die nuwe prestasietoets sal ontwerpers help met die bepaling van die grondliggende bindmiddeleienskappe wat by seëlprestasie ter sprake is, asook van die seël se vermoë om tot die algehele prestasie van die plaveisel by te dra. 'n Bykomende prestasievergelykingstoetsmetode vir die assessering van die effek van veroudering en vogtigheid is ontwikkel om die MMLS-resultate aan te vul. Ter opsomming, die prestasietoetsing het bygedra tot die identifisering van die kritiese parameters wat die seëlontwerper tydens die ontwerpproses in gedagte behoort te hou. Die navorsing wat gedoen is, dui daarop dat die huidige seëlontwerpmetode verder ontwikkel moet word om ontwerpers in staat te stel om die effek van die volgende te kan voorspel: Wisselende aslas, banddruk en ontwerpspoed; Verskillende kenmerke van die verskillende bindmiddels (bv. temperatuur viskositeitsverhoudinge, vashegting en viskoëlastiese gedrag). Wat huidige seëlontwerpmetodes betref, is die hoofterreine waarop 'n verbetering voorgestel word, die insluiting van veranderlike verkeerslas- en omgewingskenmerke, ingesluit die invloed van temperatuur en vogtigheid, en insluiting van meganistiese kenmerke van materiaal in die ontwerpmetodologie.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: A major challenge for our society is the protection of the environment. Some of the important issues are the reduction in the consumption of energy and natural raw materials, as well as the increase in consumption of waste materials. At present these topics are getting considerable attention as part of sustainable development programs. The use of recycled concrete aggregates (RCA) from construction and demolition waste (C&DW) in construction, as alternative to virgin (natural) aggregates, has strong potential. The use of RCA preserves natural resources and reduces the space required for the disposal of RCA in landfill. It is estimated that 16 thousand million (billion) tons of concrete (and 25 billion tons of aggregate) were used in 2010. Of the 2-3 billion tons of C&DW which are produced worldwide every year, South Africa contributes 5-8 million tons. This amount is increasing rapidly every year. Significant amounts of demolished concrete find their way to landfill sites. A solution for excess waste production would be the utilization of RCA together with an improvement in the final quality of RCA. It might be an important breakthrough for our society in our attempt towards sustainable development. Worldwide, infrastructure has developed a great deal since the beginning of the twentieth century. Much of the core infrastructure, including roads, bridges, water systems, and sewers, was put in place during the first half of that century. Aggregates used as construction materials, as for instance in road pavements, or as an ingredient of concrete, are important components of infrastructure. Urbanization involves reduction of natural aggregate (NA) resources, but environmental concern and the rising cost of NA is the reason that recycled materials from different sources (like roads, buildings) are being used more and more with NA in new construction work. Environmental awareness is increasing in every country for many reasons and sustainable development is demanded of all industries, including the building and construction industries. By nature, construction is not environmentally friendly, and sometimes it also changes the behavior of nature in many ways. Recycling is one of the most important ways to minimize the waste that comes from different sources, thereby avoiding repetition of, and additional environmentally hazardous practices. It may create new wealth by diminished transport and production costs and sparing of landfill site space and cost. It has the potential to extend the life of natural resources by adding a source of material, thereby reducing environmental interference and impacting on nearby construction sites, all of which improve sustainability of our natural resources. Much research on the uses of RCA has been performed during the last few decades. In fact, most of them showed that the strength class of recycled aggregate concrete (RAC) is adequate for use as structural concrete although volume changes in and durability performance of RAC in comparison with natural aggregate concrete (NAC) are still being debated and researched. Some researchers found that the durability of concrete produced with RCA is inferior, but others have found it to be sufficient for use in structural concrete. The fact that an insufficient number of studies have been carried out on the durability aspects, has limited the use of RCA as material for road construction. The aim of this study is to determine the suitability of using the RCA in structural concrete based on its strength, stiffness, dimensional stability and durability. Three types of RCA designated RCA1, RCA2 and RCA3 in this study, were taken from three different sources. These materials were tested to establish their mechanical characteristics for use as aggregates in concrete. In the experimental program RCA was used at replacement percentages of 0%, 30% and 100% to (partially) replace NA in order to study its suitability as aggregate in concrete, and to what level of NA replacement its behavior is satisfactory for structural application. A single compressive strength class was studied, due to the limited time. By performing tests of compressive strength, Young’s modulus, creep, shrinkage, and durability performance, it has been found that selected types of RCA show a real possibility for use as aggregate in concrete. When concrete with a RCA replacement of 100% was compared with NAC100% there was a small decline in strength, but when concrete with a RCA replacement of 30% was compared with NAC100% the results showed almost equal strength. A slight reduction in durability performance was found for RAC30% compared with NAC100%, but similar dimensional stability performance in terms of specific creep and drying shrinkage was measured for RAC30% and NAC100%. Based on detailed experimental results obtained from this thesis project, a number of recommendations have therefore been made for RCA characteristics that will be used in concrete mixes also taking into account the quality of RCA. Some suggestions are proposed based on the mechanical properties and durability of the concrete. In the final conclusions, future studies on RCA properties are suggested, which would help us in increasing our knowledge in the application of RCA, and which may lead to the optimal production of structural concrete in a sustainable way. In general the use of RCA in concrete is feasible and good quality RCA at 30% replacement of NA may be suitable for any kind of structural concrete. / AFRIKAANSE OPSOMMING: ‘n Groot uitdaging vir ons samelewing is die beskerming van die omgewing. Van die belangrike sake is die vermindering in die verbruik van energie en van natuurlike, onverwerkte materiale asook die groter verbruik van afvalmateriaal. Hierdie onderwerpe kry tans aanienlike aandag as deel van volhoubare ontwikkelingsprogramme. Die gebruik van betonaggregate, herwin vanaf konstruksie-en slopingsafval, en gebruik in konstruksie as alternatief vir ongebruikte natuurlike aggregate, het goeie potensiaal. Die gebruik van herwonne aggregaat beskerm natuurlike hulpbronne en verminder die oppervlakte en volume wat nodig is vir die weggooi daarvan op stortingsterreine. Dit is beraam dat 16 duisend miljoen (biljoen) ton beton (en ongeveer 25 biljoen ton aggregaat) gedurende 2010 gebruik is. Van die 2-3 biljoen ton konstruksie-en slopingsafval wat jaarliks wêreldwyd gegenereer word, dra Suid Afrika 5-8 miljoen ton by. Hierdie hoeveelheid word elke jaar vinnig meer. Beduidende hoeveelhede gesloopte beton beland elke jaar op stortingsterreine. ‘n Oplossing vir die probleem van te veel atval generering sou wees die gebruik daarvan as herwonne beton-aggregaat, sou saamval met ‘n verbetering in die uiteindelike kwaliteit van herwonne aggregaat beton. Dit kan dalk ‘n belangrike deurbraak wees vir ons samelewing in ons strewe na volhoubare ontwikkeling. Infrastruktuur het wêreldwyd baie ontwikkel sedert die begin van die twintigste eeu. Baie van die kerninfrastruktuur insluitende paaie, brue, waterstelsels en riole is gebou tydens die eerste helfte van daardie eeu. Aggregaat gebruik as konstruksiemateriaal, byvoorbeeld in padplaveisels of as’n bestanddeel van beton, is ‘n belangrike deel van infrastruktuur. Verstedeliking veroorsaak vermindering van natuurlike aggregaat hulpbronne maar besorgdheid oor die omgewing en die stygende koste van nataurlike aggregaat veroorsaak dat herwonne materiale vanaf verskillende bronne (soos paaie en geboue) meer en meer aanvullend tot natuurlike aggregaat in nuwe konstruksiewerke gebruik word. Omgewingsbewustheid is om baie redes aan die toeneem in elke land en volhoubare ontwikkeling word vereis van alle industrieë. Herwinning is een van die hoofmaniere om afval vanaf verskillende bronne tot ‘n minimum te beperk. Dit skep nuwe rykdom, verminder vervoeren vervaardigingskoste en benut afval wat anders op stortingsterreine verlore sou gegaan het. Dit het die potensiaal om die lewensduur van natuurlike hulpbronne te verleng deur ‘n materiaalbron by te voeg, deur inmenging in die omgewing te verminder, wat almal bevorderlik is om volhoubare benutting van ons hulpbronne te verbeter. Baie navorsing is gedurende die laaste paar dekades gedoen aangaande die gebruik van herwonne aggregaat. Die meeste van die navorsing het inderdaad getoon dat die sterkte van beton met herwonne aggregaat genoegsaam is vir gebruik as struktuurbeton alhoewel daar wel debatte gevoer word oor die volumeveranderings en duursaamheid prestasie van herwonne aggregaat beton vergeleke met dié van natuurlike aggregaat beton. Sommige navorsers het bevind dat die duursaamheid van beton wat met herwonne aggregaat gemaak is, minderwaardig is maar andere het bevind dat dit voldoen aan die vereistes van struktuurbeton. Slegs die feit dat daar onvoldoende toetse rakende duursaamheid gedoen is, het die gebruik van herwonne beton aggregaat beperk tot padboumateriaal. Die doel van hierdie navorsing is om te bepaal wat die geskiktheid van herwonne betonaggregaat is vir gebruik in struktuurbeton, gegrond op sterkte en duursaamheid. Drie soorte herwonne betonaggregaat wat in hierdie studie as RCA1, RCA2 and RCA3 aangedui word, is elk vanaf ‘n ander bron geneem. Hierdie materiale is getoets om hulle meganiese kenmerke vas te stel vir gebruik as aggregaat in beton. In die eksperimentele program is 0%, 30% en 100% herwonne betonaggregaat gebruik om natuurlike aggregaat gedeeltelik be vervang om sodoende die geskiktheid as betonaggregaat te bestudeer. Deur toetse uit te voer op ‘n beperkte sterkte-klas beton, soos toetse vir die bepaling van druksterkte, Young’s modulus, kruip, krimp en duursaamheid, is daar bevind dat sekere soorte herwonne betonaggregaat heel moontlik gebruik kan word in struktuurbeton. Toe beton met 100% herwonne betonaggregaat vergelyk is met beton met 100% natuurlike aggregaat, is bevind dat daar ‘n klein vermindering in sterkte was, maar waar beton met 30% herwonne betonaggregaat vergelyk is met beton met 100% natuurlike aggregaat, het die resultate byna dieselfde sterkte getoon. Dus op grond van gedetaileerde eksperimentele resultate is ‘n aantal aanbevelings gemaak vir kenmerke van herwonne betonaggregaat wat in betonmengsels gebruik sal word met inagneming van die gehalte van herwonne betonaggregaat. Die resultate vir beton met 30% en 100% herwonne betonaggregaat word vergelyk met beton wat slegs natuurlike aggregaat bevat. Sekere voorstelle gegrond op meganiese eienskappe en duursaamheid van die beton word gemaak, asook aanbevelings vir toekomstige studies van herwonne betonaggregaat wat ons sal help om ons kennis vir die toepassing van herwonne betonaggregaat uit te brei.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Hybrid concrete construction (HCC) is a construction technique that makes use of both in-situ and pre-fabricated concrete products by making optimum use of the advantages of both these methods in the same project. Although the advantages of this building method is well recognised throughout the world and a feasibility study illustrated that HCC is a suitable building method in South Africa, it remains under-utilised in the country. HCC encourages early involvement from the project team and provides clients with the best value projects and a "win-win" situation for the project team during the project development. The objective of this study is to identify barriers that prohibit an increased utilisation of HCC for the South African construction industry. Additionally, it provides possible solutions to overcome these barriers. These proposed solutions are similar to the programmes and methods that are implemented in other countries to improve their HCC utilisation. Furthermore, drivers are identified in this study to implement these solutions in the industry and a proposed "change model" is developed for private companies to assist with the change process. This study is unique because current South African conditions are used to establish the barriers and solutions. Furthermore, it takes into account that not all countries have such progressive construction industries as the European markets and therefore it considers solutions and drivers that are suitable for less advanced industries such as South Africa. The model that is proposed is applicable to any industry regardless of its nature or country. Although the United Kingdom is not the widest user of pre-fabricated concrete products, their HCC research is extensive, making it a suitable comparative country for the South African construction industry. During the investigation, the procurement methods in South Africa were found to be traditional and do not allow for early involvement or partnering in the project team. To obtain early involvement, it is critical to initiate methods such as design-and-build, contract management or public-private-partnerships during the procurement phase. Decision and design assistance from the whole project team and software tools are essential when HCC is considered. Because the South African construction industry does not provide such support it is advised here to incorporate contractors from an early stage and to develop software tools that can assist during the decision making and design process of HCC structures. The industry does not provide the project team with sufficient training programmes that increase knowledge of HCC. Training programmes that are cognitive stimulating must be developed for the industry. Furthermore, a database is required to illustrate the utilisation of different pre-fabricated products and in different projects within South Africa. Labour-intensive construction regulations and green building techniques (not compulsory) are promoted in South Africa. Labour-intensive programmes should consider the negative impact it has on the labourers and consider HCC as a building technique because the pre-fabricated elements are manufactured in a controlled and safe environment. It is advised that the toolkits that are used for green building accreditation, must be revised to accommodate the additional benefits such as less waste generation, that HCC offers to a project. Regardless of the country in which HCC is utilised, the environment must be acceptable for the innovation. By analysing the criteria that influences the use of HCC in a country and adding weighting functions to these criteria, the acceptability towards the innovation can be obtained. Furthermore, public clients and companies are recognised here as drivers of change. While public clients can commit to HCC for the cost, labour-intensive factories, green building methods, improved health and safety, training for labourers, private companies can utilise HCC to provide best value to a project. A model is proposed here for innovative companies that will allow them to change not only the company, but the industry towards a HCC "mindset". / AFRIKAANSE OPSOMMING: Hibriede beton konstruksie (HBK) is ’n tegniek waarby beide voorafvervaardigde betonelemente en in-situ beton in dieselfde projek gebruik word ten einde voordeel uit beide metodes te trek. Alhoewel die voordele van die konstruksietegniek wel bekend is in talle lande van die wêreld en ’n uitvoerbaarheidsanalise getoon het dat HBK ’n voordelige konstruksiemetode vir Suid-Afrika is, is dit tans onderbenut in die plaaslike sektor. HBK bied vir kliënte projekte van goeie waarde en omdat dit vroeë betrokkenheid verg vanaf die projekspan, resulteer dit ’n "wen-wen" situasie tydens die projekontwikkeling. Die doel van hierdie studie is om die hindernisse te ondersoek wat veroorsaak dat HBK nie meer gereeld in Suid-Afrika gebruik word nie. Ten einde die effekte hiervan te verminder, word moontlike oplossings vir hierdie hindernisse voorgestel. Die oplossings is gebaseer op tegnieke en metodes wat geïmplimenteer word in ander lande waar HBK gebruik word. Rolspelers wat hierdie verandering na HBK kan dryf word geïdentifiseer en ’n model om verandering binne ’n maatskappy te lei word voorgestel om die rolspelers te ondersteun tydens die proses. Hierdie studie is uniek omdat dit inligting gebruik van die huidige situasie van die Suid-Afrikaanse konstruksie-industrie om die hindernisse en oplossings te identifiseer. Omdat nie alle konstruksie-industrieë so vooruitstrewend is soos in Europese lande nie, is die oplossings en rolspelers relevant vir enige land wat ’n industrie het wat soortgelyk is aan Suid-Afrika. Die model wat voorgestel word is ook relevant tot enige industrie afgesien van die land waar nuwe tegnieke geïmplimenteer word. Alhoewel dit bevind is dat die Verenigde Koningkryk nie die grootste gebruikers van HBK is nie, is hulle navorsing in die veld omvattend. Daarom word die Verenigde Koningkryk beskou as ’n voorbeeld om Suid-Afrika se konstruksie-industrie mee te vergelyk, asook om inligting van HBK te verkry. Tydens die studie is bevind dat die projekaanstellingsmetodes van projekte in Suid-Afrika tradisioneel is, aangesien dit nie toelaat vir vroeë betrokkenheid of vennootskappe binne die projekspan nie. Om vroeë betrokkenheid te verkry, is dit noodsaaklik om van ontwerp-en-bou, kontrakbestuur of publiek-privaat-vernootskappe gebruik te maak. Tans is daar geen hulp wat aan ontwerpers verleen word ten opsigte van besluitnemingsmodelle en ontwerpsagteware wanneer HBK oorweeg word in Suid-Afrika nie. Die behoefte aan sulke bystand dui daarop dat sagtewarepakkette ontwerp moet word wat toepaslik is vir Suid-Afrika se konstruksie-industrie. Die industrie bied nie doelgerigte en genoegsame opleidingsprogramme aan om die industrie se kennis van HBK te verbreed nie. Addisionele opleiding wat kognitiewe stimulasie sal bied vir die hele projekspan word aanbeveel. ’n Databasis wat HBK projekte insluit, moet geskep word om die industrie bloot te stel aan die verskillende moonlikhede. Arbeid-intensiewe konstruksie-regulasies asook groen konstruksietegnieke (nie wetgedrewe nie) word sterk bevorder in Suid-Afrika. Dit word hier aanbeveel, dat voorafvervaardiging se addisionele voordele in ag geneem word wanneer hierdie regulasies en tegnieke relevant is. Hierdie voordele sluit onder meer in: die veiligheid wat aan werkers gebied word in arbeid-intensiewe fabrieke en die vermindering van afval in HBK projekte. Afgesien van die land waarin HBK gebruik word, moet die omgewing ontvanklik vir die tegniek wees. Deur verskillende kriteria te analiseer wat die gebruik van HBK beïnvloed binne ’n land en geweegde faktore daaraan te koppel, kan die ontvanklikheid van die innovasie bepaal word. Laastens word publieke kliënte en maatskappye as die drywers (of katalisators) wat verandering kan meebring, beskou. HKB bied onder andere die volgende voordele aan publieke kliënte: koste-effektiwiteit, arbeid-intensiewe werk, groen konstruksie, beter gesondheid, veiligheid en opleiding vir werkers. Maatskappye kan gebruik maak van HBK om waarde tot hul projekte toe te voeg. ’n Model word hier voorgestel om innoverende maatskappye in staat te stel om nie net hulself nie, maar ook die industrie as ’n geheel te help om ’n gesindheidsverandering jeens HBK te skep.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Higher grade steels are being rolled in South Africa by suppliers and results in structural members having an increased axial and bending moment capacity due to an increased yield stress. Structural elements used in designs are stronger and therefore lighter sections with sufficient axial and bending moment capacity are used. Displacements of structural elements are calculated using the stiffness and Young’s modulus of a profile. These values are not affected by the increased yield stress in higher steel grades and therefore have a negative effect on the displacements of the structure. The potential of these higher grade structural elements are not utilized through serviceability limit state criteria, since the displacement determination does not account for the increased capacities of higher grade steels, but only stiffness and elasticity of the members. Structural analysis of portal frames does not account for the real behaviour of steel connections and column bases. It is assumed that connections and bases are either fully rigid or perfectly pinned. This assumption is used in the analysis and design of the structure. Although it is assumed that connections and bases are either rigid or pinned, the real behaviour is in between these two extremes. Rigid connections exhibit a certain flexibility under loading whereas pinned bases provide a certain restraint under loading. The real behaviour of connections and bases are referred to as the moment-rotation behaviour of the connection. For a certain applied moment to the connection or base, the connection exhibits a certain rotation. The focus of this study is placed on the accuracy and feasibility of modelling the real behaviour of connections and bases in a structural analysis of a portal frame. A connection stiffness is determined from the connection’s moment-rotation behaviour, and is assigned to a rotational spring of zero length in a structural analysis. An experimental investigation was conducted to obtain the real displacement data of a portal frame subject to loads for two different support conditions, i.e. a perfect hinge and grouted-support. A perfect hinge support was used to isolate the moment-rotation response of the ridge and eaves connection. The experimental results were used to compared to the results obtained from a structural analysis to determine the accuracy of the numerical results. A real design case was investigated with load combinations imposed on the frame in accordance with SANS 10160:2011. Three methods of modelling connections and bases in an analysis were considered. Firstly modelling connections as rigid and bases as pinned, secondly modelling connections as linear rotational springs and bases as pinned. Lastly was to model connections as linear rotational springs and bases as non-linear rotational springs. The outcome of the research was that more accurate displacements of a portal frame could be obtained by modelling the real behaviour of rigid connections as rotational springs, but this is not the case with grouted column bases. It is thus not feasible to model the real behaviour of connections and bases in a structural analysis as the current method of modelling connections as rigid and bases as pinned provides reliable and accurate displacement results. / AFRIKAANSE OPSOMMING: Hoë graad staal word tans in Suid Afrika gerol deur verskaffers en lei daartoe dat strukturele elemente oor ’n groter aksiale- en buigmomentkapasiteit het as gevolg van ’n groter vloeispanning. Strukturele elemente in ontwerpe is sterker en gevolglik het ligter elemente die benodigde aksiale- en buigmoment-kapasiteit. Verplasings van strukturele elemente word bepaal vanaf die styfheid en Young modulus van die element. Hierdie waardes word nie beïnvloed deur die groter vloeispanning van hoë graad staal nie, en het dus ’n negatiewe uitwerking op die verplasings van die struktuur. Die potensiaal van die gebruik van hoë graad staal word nie benut in die geval van voldoening aan diensbaarheids kriterium nie, aangesien verplasings bepaal word vanaf die styfheid en elastisiteit van die elemente, en nie vloeispanning nie. Strukturele analise van portaalrame neem nie die ware gedrag van konneksies en kolomvoetstukke in ag nie. Die aanname word gemaak in analises en ontwerpe dat konneksies en voetstukke óf rigied óf geskarnierd is. Hierdie is slegs ’n aanname en in die werklikheid lê die ware gedrag van konneksies en voetstukke tussen hierdie grense. Rigiede konneksies toon ’n sekere buigbaarheid tydens belasting en geskarnierde voetstukke toon ’n sekere beperking teen rotasies. Die ware gedrag van konneksies en voetstukke word gedefinieer as moment-rotasie gedrag. Vir ’n spesifieke aangewende moment, ondergaan die konneksie of voetstuk ’n sekere rotasie. Hierdie studie fokus op die akkuraatheid en uitvoerbaarheid van die modellering van die ware gedrag van konneksies en voetstukke in ’n strukturele analise van portaalrame. Die styfheid van ’n konneksie word bepaal vanaf sy unieke moment-rotasie gedrag, en word ingevoer as ’n styfheid van ’n rotasieveer in ’n strukturele analise. ’n Eksperimentele ondersoek was gedoen om verplasingswaardes van ’n portaalraam onder belastings te bepaal. Twee ondersteunings is ondersoek in die eksperimentele program, naamlik ’n geskarnierde ondersteuning asook ’n breivul ondersteuning. Die gebruik van die geskarnierde ondersteuning isoleer die moment-rotasie gedrag van die nok en dakrand konneksies. Die eksperimentele resultate was gebruik om die akkuraatheid van die resultate vanaf die strukturele analise te ondersoek. Laastens was ’n ontwerpsprobleem ondersoek deur laskombinasies, soos bepaal volgens die riglyne van SANS 10160:2011, op ’n portaalraam aan te wend. Drie gevalle van modellering van konneksies in ’n strukturele analise is ondersoek. Eerstens om konneksies as rigied en voetstukke as geskarnierd te beskou. Tweedens was die konneksies as linieêre rotasievere gemodelleer en voetstukke as geskarnierd te beskou. Laastens was om konneksies as linieêre rotasievere te modeleer en voetstukke as nie-linieêre rotasievere. Die navorsing het getoon dat meer akkurate verplasings van portaalrame bepaal kan word deur rigiede konneksies te modelleer as rotasievere, maar dit is nie die geval met breivul ondersteunings nie. Die gevolg is dat die uitvoerbaarheid van die modellering van konneksies en voetstukke as rotasievere nie effektief is nie, aangesien die huidige metode van die modellering van konneksies as rigied en voetstukke as geskarnierd akkurate en betroubare resultate lewer.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: There is an increasing demand for the development and use of innovative materials with reduced cost of construction while offering improved structural properties. Steel fibre reinforced concrete (SFRC) can be used as a structural material to substitute the conventional reinforcing bars partially or fully. However, there is little or no codified approach on the design procedures for SFRC members in the latest guidelines outlined in the draft 2010 Model code. It is against this background that analytical methods are derived in this study for the determination of the flexural capacity of strain-softening, deflection-hardening SFRC with and without steel reinforcing bars. Models used for the determination of the flexural capacity of SFRC rectangular sections are based on equivalent stress blocks for both compression and tensile stresses. These are derived from an elastic-perfect plastic model for compression and either an elastic-constant post-peak response or Rilem’s multi-linear model for tension, in which strain compatibility and force equilibrium theories are used. By employing the equivalent stress blocks for both tensile and compressive stress states, parameters are defined by converting the actual stress-strain distribution to an equivalent stress block, depending on the ratio of yield (or cracking) strain and post-yield (post-cracking) strains. Due to the simplicity of a drop-down tensile model and a bilinear compression model, these material models are used for the subsequent derivation of the flexural models for both SFRC with and without steel reinforcing bars. An experimental program is designed and executed for model verification. This includes material characterisation experiments for the determination of material model input parameters, and main beam flexural experiments for the determination of the beam bending capacity. An indirect tensile test is used for the characterisation of the tensile behaviour while a four-point bending test is used for beam bending behaviour. Both flexural models for SFRC with and without reinforcing bars have been verified to fairly predict the flexural capacity of the beams. However, the flexural model for SFRC with steel bars offers some challenges as to whether the synergetic effect of using both steel bars and steel fibres should be incorporated at the low fibre volumes as used in the verification exercise. Furthermore, the use of indirect methods to characterise tensile behaviour added some uncertainties in the material model parameters and hence may have affected the predictability of the model. More research on the verification of the models is required to enable the use of a wider concrete strength spectrum for the verification and possible modification of the models. Studies on the model uncertainty may also help determine the reliable safety factor for the use of the model in predicting design strength of beam sections at a prescribed reliability index. / AFRIKAANSE OPSOMMING: Daar is ‘n groeiende aanvraag na die ontwikkeling en gebruik van innoverende materiale met verminderde konstruksiekoste maar verbeterde strukturele eienskappe. Staalvesel-gewapende beton (SVGB) kan gebruik word as strukturele materiaal om die konvensionele wapeningstawe gedeeltelik of ten volle te vervang. Daar is egter min of geen gekodifiseerde benaderings tot die ontwerpprosedures vir SVGB-dele in die nuutste riglyne uitgestippel in die konsepweergawe van die 2010 Modelkode nie. Dit is teen hierdie agtergrond dat in hierdie studie analitiese metodes afgelei is vir die bepaling van die buigkapasiteit van spanning-versagtende, defleksie-verhardende SVGB met en sonder staalbewapeningstawe. Modelle wat gebruik is vir die bepaling van die buigkapasiteit van SVGB reghoekige snitte is gebaseer op ekwivalente spanningsblokke vir beide druk- en trekspannings. Hierdie is afgelei van ‘n elasties-perfekte plastiese model vir druk en óf ‘n elasties-konstante post-piek respons óf Rilem se multi-lineêre model vir spanning, waarin teorieë vir drukkapasiteit en krag-ewewig gebruik is. Deur die ekwivalente spanningsblokke vir beide trek- en drukspanningstoestande te implementeer, is parameters bepaal deur die werklike verspreiding van spanningsdruk om te wissel na ‘n ekwivalente spanningsblok, afhangend van die verhouding van swig- (of kraak-)spanning en post-swig (post-kraak) spannings. Te wyte aan die eenvoud van ‘n aftrek trekmodel en ‘n bilineêre kompressiemodel, is hierdie materiaalmodelle gebruik vir die daaropvolgende afleiding van die buigingsmodelle vir beide SVGB met en sonder staalbewapeningstawe. ‘n Eksperimentele program vir modelkontrolering is ontwerp en uitgevoer. Dit sluit eksperimente in vir materiaalbeskrywing, om invoerparameters van materiaalmodelle te bepaal, asook eksperimente vir hoofbalkbuigings, om balkbuigingskapasiteit te bepaal. ‘n Indirekte trektoets is gebruik vir die beskrywing van die trekgedrag, terwyl ‘n vierpuntbuigingstoets gebruik is vir balkbuiggedrag. Dit is bewys dat beide buigingsmodelle vir SVGB met en sonder staalbewapeningstawe die buigingskapasiteit van die balke redelik akkuraat kan voorspel. Nietemin, bied die buigingsmodel vir SVGB met staalbewapeningstawe sekere uitdagings: die vraag ontstaan rondom die insluiting van die sinergetiese effek van die gebruik van beide staalstawe en staalvesels met die lae veselvolumes soos gebruik in die kontroleringsoefening. Verder het die gebruik van indirekte metodes om die buigingsgedrag te bepaal, onsekerhede gevoeg by die materiaalmodelparameters en dit mag dus as sulks die voorspelbaarheid van die model beïnvloed. Meer navorsing moet uitgevoer word oor die kontrolering van die modelle sodat ‘n wyer spektrum van betonsterkte gebruik kan word vir die verifikasie en moontlike aanpassing van die modelle. Navorsing oor die wisselvalligheid van die modelle mag ook help om die betroubare veiligheidsfaktor te bepaal vir die model se gebruik in die berekening van ontwerpkrag van balkdele teen ‘n voorgeskrewe betroubaarheidsindeks.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Plastic shrinkage cracking (PSC) in concrete is a well-known problem and usually occurs within the first few hours after the concrete has been cast. It is caused by a rapid loss of water from the concrete, either from the surface through evaporation or through absorption by dry subgrade or formwork in contact with the concrete and results in an overall reduction in concrete volume. If this volume reduction or shrinkage is restrained, plastic shrinkage cracks can occur. Plastic shrinkage cracks create an unsightly appearance on the concrete surface which reduces the quality of the concrete structure. These cracks also develop weak points in the concrete which can be widened and deepened later on by drying shrinkage and thermal movement. As a result harmful substances may enter the cracks causing accelerated concrete deterioration. These cracks may also expose the steel reinforcement causing it to corrode more aggressively. Consequently, the aesthetic value, serviceability, durability and overall performance of the concrete will be reduced. Therefore it is important to consider methods of limiting PSC. One of these methods is the addition of low volumes of polymeric fibres to concrete to reduce PSC. However, the application of this low volume fibre reinforced concrete (LV-FRC) is not clearly understood since there is a lack of knowledge and guidance available for the use of LV-FRC. The objective of this study is to gain a full understanding of PSC behaviour in conventional concrete and LV-FRC by investigating the effects of evaporation and bleeding as well as the effect of various fibre properties on PSC. The following significant findings were attained: A basis for a crack prediction model in conventional concrete was developed using the average differences in cumulative evaporation and cumulative bleeding to create a crack prediction value (CPV). This preliminary model showed that there exists a certain CPV range (-0.2 to 0.4 kg/m2 for this study) where a slight decrease in the CPV results in a significant PSC reduction. It also showed that if the CPV falls outside this range, varying the bleeding or evaporation conditions will have very little effect on the PSC. A study on the fibre properties in LV-FRC showed that there exist certain limits to the fibre volume, length and diameter where a further increase or decrease in value will have no or little effect on reducing PSC. It also showed that the effect of the fibres depend on the level of severity of PSC. The knowledge gained from this investigation can serve as a basis for the design of a model that can predict the risk of PSC in conventional concrete and specify preventative measures needed to reduce this risk. It also provides information that can be used to develop guidelines for the effective use of LV-FRC. / AFRIKAANSE OPSOMMING: Plastiese krimp krake (PKK) in beton is `n bekende probleem en vorm gewoonlik binne die eerste paar uur nadat die beton gegiet is. Dit word veroorsaak deur die vinnige waterverlies vanuit die beton, óf deur verdamping vanaf die beton oppervalk óf deur absorpsie van `n droeë grondlaag of bekisting wat in kontak is met die beton. Dit veroorsaak `n algehele vermindering in beton volume. As hierdie krimping van die beton beperk word, kan plastiese krimp krake ontstaan. PKK skep 'n onooglike voorkoms van die beton oppervlakte en verlaag die kwaliteit van die beton struktuur. Hierdie krake tree ook op as swak plekke in die beton wat later kan verbreed of verdiep deur droogkrimping en termiese beweging. Gevolglik kan skadelike stowwe vanuit die omgewing die krake binnedring wat lei tot versnelde agteruitgang van die beton. Hierdie krake kan ook die staalbewapening ontbloot wat veroorsaak dat dit vinniger roes. Gevolglik verminder die estetiese waarde, diensbaarheid, duursaamheid en algehele prestasie van die beton. Daarom is dit belangrik om metodes te ondersoek vir die beperking van PKK. Een van hierdie metodes is die byvoeging van lae volumes polimeer vesels tot beton om PKK te verminder. Die toepassing van hierdie lae volume - vesel versterkte beton (LV-VVB) word egter nog nie volledig verstaan nie as gevolg van 'n algemene gebrek aan kennis en riglyne vir die gebruik van die LV-VVB. Die doel van hierdie studie is om 'n volledige begrip van PKK gedrag in normale beton asook LV-VVB te kry. Dit word behaal deur die effek van verdamping en bloei op PKK sowel as die effek van verskillende vesel eienskappe op PKK te ondersoek. Die volgende noemenswaardige bevindinge is bekry. • Die basis van 'n kraak voorspellingsmodel vir gewone beton is ontwikkel deur gebruik te maak van die gemiddelde verskil tussen die kumulatiewe verdamping en die kumulatiewe bloei om 'n kraak voorspellingswaarde (KVW) te vorm. Hierdie voorlopige model toon dat daar `n sekere KVW interval ontstaan (-0,2 tot 0,4 kg/m2 vir hierdie studie) waar slegs 'n effense vermindering in die KVW 'n geweldige vermindering in die PKK tot gevolg het. Dit dui ook aan dat, indien die KVW buite hierdie interval val, ʼn verandering in die bloei of verdamping toestande `n baie klein invloed op die PKK het. 'n Studie oor die vesel eienskappe in LV-VVB het gewys dat daar sekere grense is aan die vesel volume, lengte en deursnee waardes, waar 'n verdere toename of afname in waarde min of geen effek het op die vermindering van PKK nie. Dit wys ook dat die effek van die vesels grotendeels afhanklik is van die risiko vlak vir PKK. Die kennis wat uit hierdie ondersoek opgedoen is, kan dien as 'n basis vir die ontwerp van 'n model wat die risiko van PKK in gewone beton kan voorspel en daarvolgens besluit op 'n voorkomingsmaatsreël om hierdie risiko te verminder. Dit bied ook inligting wat gebruik kan word om riglyne te ontwikkel vir die effektiewe gebruik van LV-VVB.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study entails the appraisal of the constitutive models available for the non linear finite element analysis of reinforced concrete, using the DIANA finite element package and following generally accepted guidelines for non linear finite element analyses. The constitutive models considered are plasticity and total strain based (fixed and rotating crack) models. The appraisal consists of the analysis of various experiments performed on reinforced concrete beams that are governed by compressive, shear and tensile dominated failures. The investigation is not limited to the accuracy of the results obtained using these models but also of the consistency of the results obtained with regard to various mesh types and sizes, as well as a study of the individual influence of several material parameters. The intention of the study was to provide the reader with an indication of the performance capacity (accuracy and consistency) of the available constitutive models, where the notion of the use of the results obtained from non linear finite element analyses for design purposes is considered. The results obtained were varied. The models performed reasonably well in the compressive and tension dominated studies, with the importance of accurate material parameters being emphasized especially for the more advanced cementitious materials investigated. The total strain rotating crack model also showed a proclivity of simulating incorrect failure modes as well as exhibiting reluctance towards stress redistribution. All models used for the shear dominated study yielded mostly inaccurate and inconsistent results, but it was found that the four node quadrilateral element with selective reduced integration performed the best. The plasticity model did not capture shear failure well, and convergence was often not attained. The constant shear retention factor of the total strain fixed crack model was found to yield more detailed response curves for the smaller mesh sizes. The results of the tension dominated beams inspired more confidence in the models as quite accurate values were attained, especially by the plasticity model used. The ability of the available models to simulate realistic structural behaviour under various failure modes is very limited, as is evident from the results obtained. The development of a more advanced and robust model is required, which can provide consistently accurate results and failure modes, and even ‘anticipate’ potential failure modes not considered by the user.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Water flows required for fire protection (fire flows) from water distribution systems (WDS) in rural towns in the Western Cape Province, South Africa, were evaluated as part of this research project. The fire flow requirements specified in different South African guidelines, as well as a number of international standards, were compared. Various guidelines and codes used in South Africa, including the South African National Standards, specify fire flow requirements according to the risk category of the area concerned. Alternative methods of firefighting and new firefighting technologies that can reduce the reliance on potable water resources for firefighting were evaluated. The traditional method of designing a WDS to provide potable water for firefighting, commonly employed in South African municipal areas formed the focus of the study. The potential fire risk costs (potential costs of damages if a fire was to occur) should also be considered, in addition to the network construction costs, when designing a WDS, in order to determine the most economically feasible option. Data obtained from the fire departments of three municipalities in rural towns of the Western Cape, was analysed to determine the actual flow rates that were required to extinguish fires in these towns. The records considered covered approximately one year in each case and included a total of 564 fire incident reports suitable for this study. According to the data, a small fraction (11%) of the fires was extinguished using water from the WDS by connecting firefighting equipment directly to a fire hydrant. The majority of the fires were extinguished by means of water ejected from a firefighting vehicle. This method implies the use of water drawn from the potable network at a certain location; the water is shuttled by firefighting vehicles, from either the fire station or from a central abstraction point in the WDS. The location of the said abstraction point was found to have a notable impact on the WDS and this received attention in this study. The data showed that 99.8% of the flows required in rural towns were lower than the flows recommended for moderate risk areas in typical South African guidelines. Hydraulic modelling of a hypothetical WDS model was conducted to illustrate that the provision of fire flows according to commonly used South African fire flow standards leads to higher costs. The latter hypothetical case study illustrates that designing a network to provide fire flows according to the referred standards resulted in 15% higher costs, compared to designing a network that would have provided for the actual recorded fire flows according to the data set obtained from the selected rural towns compiled for this study. The hypothetical case study also showed that the cost for a WDS, where sufficient pressure is required at all hydrants during peak fire flows, is 2.4% higher than the cost for a distribution system where water is supplied via predetermined hydrants for refilling firefighting vehicles. A WDS with central, predetermined abstraction points for refilling firefighting vehicles offers a solution to providing fire flows in areas where the distribution systems may be inadequate. The revision of the current fire flow standards of South Africa would, therefore, be a logical next step along with the reassessment of methods used for supplying fire flows. / AFRIKAANSE OPSOMMING: Water vloei vir brandbestryding (brandvloei) uit waterverspreidingstelsels (WVS) in plattelandse dorpe in die Wes-Kaap, Suid Afrika, is as deel van hierdie navorsingsprojek geëvalueer. Die brandvloei soos gespesifiseer in verskillende Suid-Afrikaanse riglyne, asook ʼn aantal internasionale standaarde is vergelyk. Verskeie riglyne en kodes wat in Suid-Afrika gebruik word, insluitende die Suid-Afrikaanse Nasionale Standaarde, spesifiseer brandvloei-vereistes op grond van die risiko-kategorie van ʼn spesifieke gebied. ʼn Verskeidenheid alternatiewe metodes vir brandbestryding en nuwe brandbestrydings-tegnologieë is ondersoek, om sodoende die afhanklikheid van ons beperkte drinkbare waterbronne vir brandbestryding te verminder. Die tradisionele metode om water aan munisipale areas te voorsien, die gebruik van ʼn WVS, is ook geassesseer. Hierdie metodes dui daarop dat die potensiële brandgevaar-kostes (potensiële koste van skade indien ʼn brand sou plaas vind) ook in ag geneem moet word, tesame met die konstruksie kostes van ʼn WVS, om sodoende die mees ekonomies haalbare netwerk te bepaal. Data wat verkry is vanaf die brandweer departement van drie plattelandse munisipaliteite in die Wes-Kaap is ontleed om die werklike vloei-tempos vas te stel wat nodig was om brande te blus in hierdie dorpe. Die data is verkry vir ʼn tydperk van een jaar en 564 brandverslae was bruikbaar vir die doeleindes van hierdie studie. Volgens die data was ʼn lae aantal (11%) van die brande geblus vanuit die WVS deur die koppeling van brandbestrydingstoerusting direk aan ʼn brandkraan. Die meeste van die brande is geblus met behulp van water wat voorsien is deur ʼn brandbestrydingsvoertuig. Met hierdie metode word water deur die brandbestrydings-voertuie aangery vanaf die brandweerstasie of onttrek vanuit ʼn sentrale ontrekkingspunt in die WVS. Daar is gevind dat die ligging van laasgenoemde ontrekkingspunt ʼn beduidende impak op die WVS het – hierdie aspek is daarom verder ondersoek. Die data het getoon dat 99.8% van die vloei-tempo’s wat nodig is om brande te blus in plattelandse dorpe, laer is as die brandvloei riglyne vir matige risiko-areas volgens tipes Suid-Afrikaanse standaarde. Hidrouliese modellering van ʼn hipotetiese WVS is uitgevoer om te illustreer dat die verskaffing van brandvloei volgens die standaarde wat algemeen gebruik word, hoër kostes tot gevolg het. Die laasgenoemde hipotetiese gevallestudie illustreer dat ʼn netwerk ontwerp om brandvloei te verskaf volgens die huidige standaarde 15% duurder is as vir netwerke wat ontwerp is om die werklike aangetekende brandvloei te voorsien soos getoon deur die veld-data wat vir hierdie studie verkry is. Die hipotetiese gevallestudie het ook getoon dat die koste vir ʼn WVS, waar voldoende drukke gehandhaaf moet word by alle brandkrane terwyl piek brand vloeie voorsien word, 2.4% duurder is as vir ʼn WVS waar die brandvloei verskaf word by voorafbepaalde brandkrane vir die hervulling van brandbestrydingsvoertuie. ʼn WVS met sentrale onttrekkingspunte vir die hervulling van brandbestrydingsvoertuie, bied ʼn metode om brandvloei te voorsien in gebiede waar die WVS onvoldoende is, bv. informele nedersettings. Die hersiening van die huidige brandvloei standaarde van Suid Afrika sou dus ʼn logiese volgende stap wees, tesame met die herevaluering van die metodes wat gebruik word vir die verskaffing van brandvloei.