Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Steel fibre reinforced concrete (SFRC) is the most prominent fibre reinforced concrete composite that was engineered to enhance the material’s post-cracking behaviour. In certain situations it is utilised to replace conventional reinforcement and considered to be more cost-efficient. The purpose of this research is to characterise the moment redistribution behaviour of a statically indeterminate SFRC structure with varying volumes of fibres, with the focus on the development of the moment redistribution accompanied by the rotation of the plastic hinges at the critical sections in the structure. The material properties were characterised with a series of experimental tests. The compression behaviour was obtained with uniaxial compression tests while the uniaxial tensile behaviour was obtained with an inverse analysis performed according to flexural test results. These properties were utilised to derive a theoretical moment-curvature relation for each SFRC member which supplied the basis for the characterised moment-rotation behaviour and the finite element analyses (FEA) performed on the statically indeterminate structure. Experimental tests were conducted on the statically indeterminate structure in laboratory conditions to validate the theoretical findings. For the different SFRCs the material properties in compression were similar, while it resulted in an increased tensile resistance with an increase in the volume steel fibres. The theoretical momentcurvature and moment-rotation responses also indicated an increased structural capacity and member ductility with an increase in the volume fibres. From the finite element analyses the computational moment redistribution-plastic rotation relations were obtained. It was found that the final amount of moment redistribution decreased with an increase in the fibre volume, but that the rotational capacity increased. It was found that the experimental moment-curvature and moment-rotation results correlate well with the theoretical predictions. Also, unexpected structural behaviour was observed, but the issue was addressed with applicable computational analyses which confirmed the possible causes. It was concluded that the computational moment redistribution approximations were reasonably accurate. A parameter study indicated that the crack band width differed among the different SFRC members. / AFRIKAANSE OPSOMMING: Staal vesel versterkte beton (SVVB) is die mees vooraanstaande vesel versterkte beton mengsel wat ontwikkel is om die materiaalgedrag na kraakvorming te verbeter. In sekere situasies kan dit gebruik word om konvensionele staal te vervang en lei soms to koste vermindering . Die einddoel van die studie is om die moment herverdeling gedrag te karaktiseer vir ‘n statiese onpebaalbare SVVB struktuur deur die invloed van verskillende volumes vesels en die rotasie kapasiteit by die kritieke posisies in ag te neem. Die materiaal eienskappe was geidentifiseer met ‘n reeks eksperimentele toetse. Die druk gedrag was geïdentifiseer deur eenassige druktoetse, terwyl die eenassige trek gedrag bekom is met die implementasie van ‘n inverse analise van die uitgevoerde buig toetse. Hierdie eienskappe is gebruik om die teoretise moment-kromming verhouding vir elke mengsel te bekom. Hierdie verhoudings word as die basis bestempel vir die teoretiese moment-rotasie verhouding en die eindige element analises (EEA) wat op ‘n staties onbepaalbare struktuur toegepas is. Eksperimentele toetse is op hierdie voorgestelde struktuur toegepas om die teoretiese verwagtings te verifieer. Dit is gevind dat die druk gedrag ooreenstem tussen die verskillende mengsels, alhoewel ‘n toename in die trek kapasiteit ervaar is met ‘n toename in die volume vesels. Die teoretiese momentkromming en moment-rotasie verwantskappe stel ook voor dat die strukturele kapasiteit en duktiliteit toeneem met ‘n toename in die volume vesels. Die teoretiese moment herverdeling-plastiese rotasie verwantskapppe is verkry deur middel van die eindige element analises. Dit is gevind dat die aantal moment herverdeling by faling afgeneem het vir ‘n toename in die volume vesels, maar dat dit to ‘n groter rotasie kapasiteit gelei het. Van die eksperimentele resultate is dit afgelei dat die teoretiese moment-kromming en momentrotasie verwantskappe goeie benaderings voorstel. Sekere invloede van die opstelling het daartoe gelei dat onverwagte strukturele gedrag bekom is, maar die moontlike invloede is verifieer met eindige element analises. Dit is afgelei dat die teoretiese beramings van die moment herverdeling gedrag redelik akkuraat is. ‘n Parameter studie het getoon dat die kraak spasiëring verskil tussen mengsels met verskillende volumes vesels.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Sustainability is difficult to achieve in a world where population and economic growth leads to increased production of greenhouse gases, resource depletion and waste generation. Today, the environmental dimension of sustainability, which is more commonly known as the natural environment, and the construction industry are two terms often mentioned together. In Europe, 12.4 % of greenhouse gas emissions are induced by the construction and manufacturing industry (Maydl, 2004). Also, 50 % of the resources extracted are used in the construction industry and more than 25 % of waste generated is construction and demolition waste. In South Africa, the building sector accounts for approximately 23 % of the total greenhouse gas emissions (Milford, 2009). Furthermore, 60 % of investment is made in the residential sector where 33 % of the building stock is the focus of the government’s Housing Programme. It is seen that the construction industry significantly impacts the natural environment and the aim should be to reduce this negative impact. Within the local residential sector, the low-cost housing sector presents potential when it comes to sustainable improvements. Each of the three spheres of sustainability, namely economy, natural environment and society, plays a crucial role in this sector. Various studies have been done on the economical and social fields, but little information exists on the impact low-cost houses have on the environment. A need arises to scientifically quantify the environmental impact hereof, therefore it is chosen as the focus of this study. Various methods in order to determine the environmental impact of the built environment exist globally, but they tend to be complex, are used in conjunction with difficult to understand databases and require expensive software. A need for a local quantification method with which to determine the environmental impact of the built environment, more specifically low-cost housing, has been identified. A simple and easy-to-use analysis-orientated quantification method is proposed in this study. The quantification method is compiled with indicators related to the local conditions; these include Emissions, Resource Depletion and Waste Generation. The end objective is to provide the user with an aggregated total value called the Environmental Impact Index to ease comparison of possible alternatives. The quantification method is developed as a mathematical tool in the form of a partial Life Cycle Assessment which can aid in objective decision making during the conception and design phase of a specific project. Note that only the Pre-Use Phase of the building life cycle is considered during the assessment, but can be extended to include the Use Phase and End-of-Life Phase. The proposed method has the capability of calculating and optimising the environmental impact of a building. Regarding low-cost housing, different housing unit designs can be compared in order to select the best alternative. The quantification method is implemented for two low-cost house design types in this study. Firstly, the conventional brick and mortar design is considered whereafter a Light Steel Frame Building is viewed as an alternative. The model implementation demonstrates that the model operates in its supposed manner. Also, Light Steel Frame Building housing units are shown to be worth investigating as an alternative to the conventional brick and mortar design but should be confirmed with a more accurate Life Cycle Assessment. / AFRIKAANSE OPSOMMING: In ’n wêreld waar toenemende ekonomiese en bevolkingsgroei veroorsaak dat al hoe meer kweekhuisgasse voortgebring word, hulpbronne uitgeput word en groter hoeveelhede rommel geproduseer word, is dit ’n bykans onbegonne taak om volhoubaarheid te probeer bereik. Volhoubaarheid rakende die natuurlike omgewing en konstruksie is twee terme wat vandag dikwels saam genoem word. Ongeveer 12.4 % van die kweekhuisgasse wat in Europa vrygestel word kom uit die konstruksie- en vervaardigingbedrywe (Maydl, 2004). Die konstruksiebedryf gebruik ook bykans die helfte van hulpbronne wat ontgin word en meer as 25 % van rommel word deur konstruksie of sloping produseer. Die Suid-Afrikaaanse boubedryf is verantwoordelik vir 23 % van die totale hoeveelheid kweekhuisgasse wat die land vrystel. Die behuisingsektor, waar die regering aan die hoof van 33 % van eenhede staan, ontvang 60 % van bestaande beleggings (Milford, 2009). Dit is dus duidelik dat die boubedryf ’n negatiewe impak op die natuurlike omgewing het en dat dit van groot belang is om dié situasie te verbeter. In die behuisingsektor het lae-koste-behuising groot potensiaal as dit kom by volhoubaarheid. Volhoubaarheid bestaan uit drie sfere: ekonomie, natuurlike omgewing en sosiaal, en al drie speel ’n betekenisvolle rol in lae-koste-behuising. Daar is reeds verskeie studies aangepak om die ekonomiese en sosiale sfere te beskryf, maar daar is steeds min inligting beskikbaar oor die omgewingsimpak van ’n lae-koste-huis. Dit laat die behoefte ontstaan om hierdie impak te kwantifiseer. Bestaande metodes wat wêreldwyd gebruik word om ʼn omgewingsimpak te bepaal is dikwels besonder kompleks en benodig duur sagteware tesame met ingewikkelde databasisse om dit te implementeer. ’n Behoefte aan ’n plaaslike kwantifiseringsmetode is geïdentifiseer. Hierdie studie stel ’n eenvoudige, gebruikersvriendelike kwantifiseringsmetode bekend. Dit word saamgestel uit faktore wat verband hou met die plaaslike omgewing: Uitlaatgasse, Hulpbronuitputting en Rommelvervaardiging. Uiteindelik word ’n saamgestelde waarde, wat die Omgewingsimpak-indeks genoem word, bereken om vergelyking te vergemaklik. Hierdie kwantifiseringsmetode word aan die hand van ’n gedeeltelike lewenssiklus-analise as ’n wiskundige hulpmiddel ontwikkel. Slegs die eerste fase van ’n gebou se lewenssiklus word beskou tydens hierdie studie, maar dit is moontlik om die ander twee fases in te sluit. Die voorgestelde metode het die vermoë om die omgewingsimpak te bereken en ook te optimeer. Tydens die ontwerpsfase, wanneer belangrike besluite geneem moet word, kan so ’n hulpmiddel van enorme waarde wees om die beste opsie uit verskillende alternatiewe te help identifiseer. Die studie beskou twee tipes behuisingseenhede vir die doel van implementering van die kwantifiseringsmetode: die konvensionele baksteen en mortel metode en alternatiewelik ’n ligte staalraamwerk-gebou. Tydens implementering van die voorgestelde metode, demonstreer die model dat dit werk soos dit veronderstel is om te funksioneer. Verder is getoon dat ’n ligte staalraamwerk-gebou ’n waardevolle alternatief is om te ondersoek, maar dit moet liefs met ’n meer akkurate lewenssiklus-analise bevestig word.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Various design guidelines have been published over the past four decades to calculate the minimum submergence required at pump intakes to prevent vortex formation. These design guidelines also require the suction bell to be located not higher than 0.5 times the suction bell diameter (D) above the floor. Sand trap canals are an integral part of large river abstraction works, with the pump intakes located at the end of the sand trap canals. The canals need to be flushed by opening a gate, typically 1.5 m high, that is located downstream of the pump intake. This requires the suction bell be raised to not interfere with the flushing operation, which leads to the question – what impact does the raising of the suction bell have on the minimum required submergence? A physical hydraulic model constructed at 1:10 scale was used to determine the submergence required to prevent types 2, 5 and 6 vortices for prototype suction bell inlet velocities ranging from 0.9 m/s to 2.4 m/s, and for suction bells located at 0.5D, 1.0D and 1.5D above the floor. The tests were undertaken for four suction bell configurations with a conventional flat bottom suction bell, fitted with a long radius bend, being the preferred suction bell configuration in terms of the lowest required submergence levels. The experimental test results of the preferred suction bell configuration were compared against the published design guidelines to determine which published formula best represents the experimental test results for raised pump intakes. It became evident from the experimental test results that the required submergence increased markedly when the suction bell was raised higher than a certain level above the floor. It was concluded that this “discontinuity” in the required submergence occurred for all the suction bell configuration types when the ratio between the prototype bell inlet velocity and the approach canal velocity was approximately 6.0 or higher. It is recommended that, for pump intakes with a similar geometry to that tested with the physical hydraulic model, critical submergence is calculated using the equation published by Knauss (1987), i.e. S = D(0.5 + 2.0Fr), if the prototype bell inlet velocity/approach canal velocity ratio is less than 6.0, and that the equation published by the Hydraulic Institute (1998), i.e. S = D(1 + 2.3Fr), can be used where the ratio, as determined with Knauss’ (1987) equation, exceeds 6.0. It is also recommended that prototype bell inlet velocities be limited to 1.5 m/s. / AFRIKAANSE OPSOMMING: Oor die afgelope vier dekades is verskeie ontwerpriglyne vir die berekening van minimum watervlakke, om werwelvorming by pompinlate te voorkom, gepubliseer. Hierdie ontwerpriglyne vereis dat die klokmond van die pompinlaat nie hoër as 0.5 keer die deursnee van die klokmond (D) bokant die kanaalvloer geleë moet wees nie. Sandvang kanale vorm ‘n integrale deel van groot riveronttrekkingswerke, met pompinlate wat aan die einde van hierdie kanale geleë is. Die kanale word aan die stroomaf kant van die pompinlaat voorsien met sluise sodat die kanale gespoel kan word. Hierdie sluise is tipies 1.5 m hoog. Dit is derhalwe nodig om die hoogte onder die klokmond dieselfde te maak as die hoogte van die sluis sodat die klokmond die spoelwerking nie beïnvloed nie. Die vraag is egter – wat is die impak op die minimum vereiste watervlakke indien die klokmond op ‘n hoër vlak installeer word? ‘n Fisiese hidrouliese model met ‘n 1:10 skaal is gebruik om die minimum watervlakke te bepaal waar tipes 2, 5 en 6 werwels aangetref word vir prototipe inlaatsnelhede van 0.9 m/s tot 2.4 m/s en klokmond hoogtes van 0.5D, 1.0D en 1.5D bokant die kanaalvloer. Vier klokmond konfigurasies is getoets. Die minimum vereiste watervlakke was die laagste vir die tradisionele plat klokmond met ‘n lang radius buigstuk en was dus die voorkeur klokmond. Die eksperimenttoetsresultate vir die voorkeur klokmond is met die gepubliseerde ontwerpriglyne vergelyk om te bepaal watter van die ontwerpsriglyne van toepassing sal wees vir verhoogde klokmond installasies. Uit die eksperimenttoetsresultate is dit duidelik dat die vereiste watervlakke skielik verhoog sodra die klokmond installasie ‘n seker hoogte bokant die kanaal vloer oorskry. Daar is bevind dat hierdie verskynsel by al vier klokmond konfigurasies voorkom sodra die verhouding tussen die prototipe klokmond inlaatsnelheid teenoor die snelheid in die kanaal hoër as 6.0 is. Daar word aanbeveel dat die minimum vereiste watervlak vir pompinlate met dieselfde geometrie as die fisiese model, met Knauss (1987) se vergelyking bereken word, naamlik S = D(0.5 + 2.0Fr), waar die snelheidsverhouding tussen die klokmond en kanaal 6.0 nie oorskry nie, en dat die vergelyking gepubliseer deur die Hydraulic Institute (1998), S = D(1 + 2.3Fr), gebruik word waar die snelheidsverhouding 6.0, so bereken met Knauss (1987) ser vergelyking, wel oorskry. Die prototipe klokmond inlaatsnelheid moet ook beperk word tot 1.5 m/s.

Thesis (MEng (Civil Engineering))--University of Stellenbosch, 2006. / Most construction projects do not complete exactly as scheduled or exactly as priced. During the implementation of a project there is almost certainly some deviation from the original estimate. The implementation of a majority of projects has actually been shown to cost more and take longer than originally estimated. However, the duration and cost performance of a project’s implementation is measured against the initial estimate produced. Thus if a project is considered to have completed late or over budget then essentially the duration or cost estimated was insufficient. Due to the fact that estimates are produced in a present day environment for inherently unique projects that occur in uncertain future environments, the estimates produced will need to incorporate uncertainty to increase their likelihood of achievability. This study aims to derive methods to incorporate future uncertainty into project estimates. This uncertainty is incorporated, analysed and manipulated through the use of Probabilistic models and First Order Second Moment Reliability methods. The derived methods provide project management professionals with tools that enable them to design estimates that incorporate future uncertainty and are reliable to a specified degree. Further methods are then derived to probabilistically assess the commercial feasibility of a project in an uncertain future environment. These derived methods then provide project managers and decision makers with more reliable procedures and information which in turn should assist them in making correct, project orientated decisions and ultimately increase profit reliability and client satisfaction.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / The Southern African Institute of Steel Construction expressed concern with regard to the unit definition of the effective length factor, K, stipulated for compressive elements of parallel chord trusses in Clause 15 of SANS 10162-1:2005 - Limit state design of hot-rolled steelwork. The simplified method for truss design specified in the code assumes all compression members are pin-connected, which allows for greater design simplicity and reduces the amount of code interpretation required by the designer. In addition to this, Clause 15 requires the additional reduction in resistance of the first web compression members by a factor of 0.85. However, this approach may be considered overly conservative and in current design practice the effective length factor is often reduced to less than 1.0. This research investigates the effective length factor of web compression members in parallel chord trusses, by means of investigative structural analyses of representative trusses using ANGELINE and Prokon analytical programs, and by designing, constructing and testing six representative trusses, using current design practices. A comparative study of a number of different countries’ codified approaches to truss design is also included. The structural analyses revealed that in-plane buckling of the web compression members was the consistent mode of failure, however at a much greater applied load than the design load determined according to SANS 10162-1:2005. Contrary to the expected mode of failure, all six tests performed on the representative trusses exhibited elastic out-of-plane buckling, or strongaxis buckling, of the web compression members, but still at a much greater applied load than the design load. The unexpected out-of-plane buckling of the web members is due to the inplane stiffness of the end connections used. In order to stay true to current design practice, gusset plates and longitudinal welds were used to join the web members to the chords. The stiffness of the gusset plates therefore significantly reduced the effective length of the web compression members in-plane, but did not reduce the effective length out-of-plane. Despite the unanticipated behaviour of the tests performed, certain conclusions can still be drawn from the results. The unit definition of the effective length factor for in-plane buckling of web compression members is too conservative and a K factor of 0.8 is recommended. In addition to this an effective length factor for out-plane-buckling of web compression members of 1.1 is recommended for trusses with welded connections. The necessity of the reduction in resistance of 0.85 of the first web compression members requires further investigation. The most important conclusion to be drawn is that out-of-plane buckling of web compression members can be the dominant failure mode, which is not taken into consideration in current design practice.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Pre-cast sections have the advantages of structural efficiency, better quality control and less construction time, which enable them to be widely used in building structures. The connections of pre-cast buildings play a vital role for the stability and strength of structures. Nowadays, more attention is drawn to the aesthetical appearance of building structures, especially by architects. The Hidden Corbel Connection (HCC) was then developed to make the building structures stable and aesthetically pleasing. A modified HCC was designed and investigated in this study. Amongst all the mechanisms in the connection zone, the mechanism of the end anchorage length of tension reinforcement plays a key role in the economy of the connection and is hence further investigated. In order to investigate whether the end anchorage length of tension reinforcement can be reduced for a simply supported beam, a 2D non-linear finite element model is used to analyze the stress distribution inside the connection zone. Based on the stress distribution in the connection zone, the tensile force was calculated at the face of the support, which directly correlates to the required end anchorage length of tension reinforcement. The confinement in the connection zone increases the bond stress, which in turn reduces the required anchorage length of tension reinforcement. Therefore, a 3D model is used to analyze the region inside the modified HCC to find the position of the best confinement. By comparing the finite element (FE) results with Eurocode 2 (2004), and SABS 0100-1 (2000), it is demonstrated that the FE results require the shortest anchorage length, while the longest anchorage length is specified in SABS 0100-1 (2000). Based on the comparison between the FE results and the design codes, a laboratory experiment was then performed to determine if the end anchorage length of tension reinforcement can be reduced. Four beams with different support conditions and with different end anchorage length of tension reinforcement were tested. The results of the laboratory experiment indicate that the end anchorage length for simply supported beams can be shortened from the specification of SABS 0100-1 (2000).

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2005. / 192 leaves on CD format, preliminary i-xii pages and numbered pages 1-135. Includes bibliography, list of figures and tables. / ENGLISH ABSTRACT: As a fibre reinforced material, engineered cementitious composite (ECC) has tough, strain-hardening behaviour in tension despite containing low volumes of fibres. This property can be brought about by developments in fibre, matrix and interfacial properties. Poly Vinyl Alcohol (PVA) fibre has been developed in recent years for ECC, due to its high tensile strength and elasticity modulus. However, the strong interfacial bond between fibre surface and matrix is a challenge for its application. This study focuses on the tailoring of matrix and fibre/matrix interfacial properties by cement replacement with fly ash (FA) and Ground Granulated Corex Slagment (GGCS). In this study the direct tensile test, three point bending test, micro-scale analysis, such as X-Ray Fluorescence Spectrometry analysis (XRF), Scanning Electron Microscope (SEM), are employed to investigate the influence of cement replacement, aging, Water/Binder (W/B) ratio, workability on ECC behaviour. This study has successfully achieved the aim that cement replacement by FA and GGCS helps to improve the fibre/matrix interfacial properties and therefore enhances the ECC tensile behaviour. Specifically, a high volume FA-ECC has stable high tensile strain capacity at the age of 21 days. This enables a constant matrix design for the investigation of other matrix influences. The Slag-ECC has a higher tensile strength but lower tensile strain capacity. The combination of FA and GGCS, moderate tensile strength and strain capacity is achieved Both tensile tests and Micro-scale analyses infer that the high volume FA-ECC has an adhesive type fibre/matrix interfacial interaction, as opposed to the cohesive type of normal PVA fibre-ECC. The different tensile behaviour trend of steel fibre-ECC and PVA fibre-ECC with the FA content is presented and discussed in this research. The investigations of aging influence indicate that the high volume FA-ECC has a beneficial effect on the properties of the composite at an early stage. However, at a high age, it has some difficulty to undergo multiple cracking and then leads to the reduction of tensile strain capacity. The modified mix design is made with the combination of FA and GGCS, which successfully increases the interfacial bond and, thereby, improves the shear transfer to reach the matrix crack strength. Therefore, an improved high age tensile behaviour is achieved. The W/B and fresh state workability influence investigations show that the W/B can hardly affect the tensile strain at early age. However, the workability influences on composite tensile strain significantly, because of the influence on fibre dispersion. Other investigations with regard to the hybrid fibre influences, the comparison of bending behaviours between extruded plate and cast plate, the relation between bending MOR and tensile stress, and the relation between compression strength and tensile strength contribute to understand ECC behaviour. / AFRIKAANSE OPSOMMING: As ‘n veselversterkte materiaal, het ontwerpte sementbasis saamgestelde materiale, taai vervormingsverhardingseienskappe in trek, ten spyte van lae veselinhoud. Hierdie eienskap word bewerkstellig, deur ontwikkelings in vesel, matriks en tussenveselbindingseienskappe. Poli-Viniel Alkohol (PVA) vesels is ontwikkel vir ECC, as gevolg van die hoë trekkrag en hoë modulus van hierdie veseltipe. Die sterk binding tussen die PVA-veseloppervlak en die matriks is egter ‘n uitdaging vir sy toepassing. Hierdie studie fokus op die skep van gunstige matriks en vesel/matriks tussenvesel-bindingseienskappe deur sement te vervang met vlieg-as (FA) en slagment (GGCS).In hierdie navorsing is direkte trek-toetse, drie-punt-buigtoetse, mikro-skaal analise (soos die X-straal ‘Fluorescence Spectrometry’ analise (XRF) en Skanderende Elektron Mikroskoop (SEM))toegepas. Hierdie metodes is gebruik om die invloed van sementvervanging,veroudering, water/binder (W/B)-verhouding en werkbaarheid op die meganiese gedrag van ECC te ondersoek.Die resultate van hierdie navorsing toon dat sementvervanging deur FA en GGCS help om die vesel/matriks tussenveselbindingseienskappe te verbeter. Dus is die ECC-trekgedrag ook verbeter. Veral ‘n hoë volume FA-ECC het stabiele hoë trekvervormingskapasiteit op ‘n ouderdom van 21 dae. Dit bewerkstellig ‘n konstante matriksontwerp vir die navorsing van ander matriks invloede. Die Slag-ECC het ‘n hoër treksterkte, maar laer trekvervormingskapasiteit. Deur die kombinasie van FA en GGCS word hoë treksterkte, sowel as gematigde vervormbaarheid in trek verkry. Beide trektoetse en mikro-skaal analise dui aan dat die hoë volume FA-ECC ‘n adhesie-tipe vesel/matriks tussenvesel-bindingsinteraksie het, teenoor die ‘kohesie-tipe van normale PVA vesel-ECC. Die verskille in trekgedrag van staalvesel-ECC en PVA vesel-ECC ten opsigte van die FA-inhoud is ondersoek en word bespreek in die navorsing. Die navorsing toon verder dat die hoë volume FA-ECC goeie meganiese eienskappe het op ‘n vroeë ouderdom. Op hoër ouderdom word minder krake gevorm, wat ‘n verlaging in die trekvervormingskapasiteit tot gevolg het. Met die kombinasie van FA en GGCS, word die vesel-matriksverband verhoog, waardeur ‘n verbetering in die skuifoordrag tussen vesel en matriks plaasvind. Verbeterde hoë omeganiese gedrag word daardeur tot stand gebring. Navorsing ten opsigte van die invoed van die W/B en werkbaarheid dui daarop dat die W/B slegs geringe invloed het op die trekvormbaarheid, terwyl die werkbaarheid ‘n dominerende rol speel in hierdie verband.Verdere studies sluit in die invloed van verskillende vesels, die vergelyking van die buigingsgedrag van geëkstueerde plate en gegote plate, die verhouding tussen buigsterkte en treksterkte, en die verhouding tussen druksterkte en treksterkte dra by tot beter begrip van die gedrag van ECC.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: In an attempt to improve the efficiency of the transport system, the national government has instituted a new tender system for public transport contracts. Small bus and taxi operators are unfamiliar with operating in the formal sector. This study focuses on the extent of their disadvantage in the current tender system and recommends measures to counterbalance this. A questionnaire was devised to determine how much assistance these operators would require to prepare them for the tender, using the model bus tender document as a basis for this. The response rate was 20% with 14 taxi and 17 bus questionnaires being retrieved for analysis. The results showed that 10% of operators had no know ledge of the tender and many needed training in basic accounting and business procedures as well as public transport operation skills. Recommendations included institutional changes in public transport funding, management and allocation of resources as well as the type of education and training required. These changes should be implemented soon enough to ensure that small, medium and micro enterprises (SMME) operators are well prepared for the new tender system. / AFRIKAANSE OPSOMMING: In 'n poging om die effektiwiteit van die vervoersisteem te verbeter, het die nasionale regering 'n tendersisteem vir openbare vervoerkontrakte ingestel. Klein bus en taxioperateurs is nie bekend met die bedryf van 'n besigheid in die formele sektor nie. Hierdie studie konsentreer op hul agterstand in die huidige tendersisteem en maak aanbevelings oor hoe dit oorkom kan word. 'n Vraelys is opgestel om te bepaal hoeveel bystand hierdie operateurs sal benodig om hu1le voor te berei vir die tender. Die model bus tenderdokument is as basis gebruik. 20% van die operateurs het op die vraelys gereageer - 14 taxi- en 17 busvraelyste is ontvang vir verder verwerking. Die resultate van die opname het getoon dat 10% van die operateurs geen kennis van die tender gehad het nie en dat baie van hulle opleiding benodig in basiese rekeninkundige en besigheidsprosedures sowel as openbare vervoer bedryfsmetodes. Aanbevelings van die studie sluit lil institusionele veranderinge lil openbare vervoerbefondsing, bestuur en die toewysing van hulpbronne asook die tipe onderrig en opleiding wat benodig word. Hierdie veranderinge behoort so gou as moontlik geïmplementeer te word sodat klein, medium en mikro operateurs goed voorberei kan word vir die nuwe tendersisteem.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: End stop impact forces are horizontal longitudinal forces imposed by the crane on the end stops. Both the previous South African loading code SABS 0160:1989 and the current South African loading code SANS 10160 , classify end stop impact force as an accidental load case , hence they are not expected to occur within the expected lifetime when the guide lines for crane operation are strictly adhered to. In the estimation of end stop impact force, the previous South African loading code SABS 0160:1989 gives two guidelines for estimating the end stop impact force. The first guideline is simplistic in its approach and it’s based on the assumption that the crane and its supporting structure act as rigid bodies; hence calculation is based on rigid body mechanics. Literature reviewed reveals that this is not correct. The second guideline is more explicit in its approach as it takes into account the crane speed, resilience of the buffers and resilience of the end stops. The current South African loading code, SANS 10160 gives a better representation of the dynamics of the crane movement. However, the dynamic factor recommended for the estimation of end stop impact force is empirical in nature and thus lacks adequate scientific backing. One of the purposes of this research was to investigate the influence of the stiffness of the crane bridge on the end stop impact force. This was achieved by conducting a series of FEA simulations on the double bridge EOHTC fitted with elastomeric buffers. For this set of simulations, the effect of each influencing parameter on the end stop impact force was investigated, and the maximum end stop impact force was obtained using a constraint optimization technique. From the results obtained, comparison was then made with the existing maximum end stop impact force for a single bridge EOHTC fitted with elastomeric buffers. Another purpose of this research was to investigate the end stop impact force for an electric overhead travelling cranes (EOHTC) fitted with hydraulic buffers taking into account the dynamics involved in the movement of the EOHTC. This was achieved by a series of experimental and numerical investigation. The numerical investigation was conducted using an existing numerical model of an EOHTC which captures the crane and its supporting structure as a coupled system. Finite element analysis (FEA) impact force histories obtained were calibrated to the base experimental impact force histories. Thereafter, a series of FEA simulations were conducted by changing the parameters which have a substantial effect on the end stop impact forces. This yielded various maximum impact peaks for various parameters. The maximum impact force was then mathematical obtained from the FEA impact force histories for a given level of reliability using a constraint optimization technique. Also, codified end stop impact forces were calculated for the SABS 0160:1989 and SANS 10160-6:2010. From the results obtained, comparison was made between the codified end stop impact force and the maximum impact force obtained from the constraint optimization technique. / AFRIKAANSE OPSOMMING: Ent buffer impak kragte is horisontale kragte wat deur die kraan op die entbuffers aangewend word. Beide die Suid Afrikaanse las kode SABS 0160:1989 en die voorgestelde Suid Afrikaanse las kode SANS 10160, klasifisseer die entbuffer impak kragte as ‘n ongeluks las geval, dus word die kragte nie verwag tydens die verwagte leeftyd van die kraan wanneer die riglyne van die kraan prosedures streng gevolg word nie. Volgens die Suid-Afrikaanse las kode SABS 0160:1989 word daar twee riglyne voorgestel om die entbuffer kragte te bepaal. Die eerste riglyn is ‘n eenvoudige riglyn en word gebaseer op die aaname dat die kraan en die ondersteunende struktuur as ‘n starre ligame reageer en dus word die kragte bereken deur star ligaam meganika, alhoewel, uit die literatuur word dit bewys as inkorrek. Die tweede riglyn is ‘n meer implisiete benadering aangesien dit die kraan snelheid, elastisiteit van die buffers sowel as die elastisiteit van die end stoppe in ag neem. SANS 10160-6:2019 gee ‘n beter benadering van die dinamiese beweging van die kraan. Die voorgestelde dinamiese faktor waarmee die ent_buffer_kragte bereken word, is empiries van natuur . Een van die doelstellings vir die navorsings projek was om te bepaal wat die invloed van die kraan brug se styfheid op die entbuffer kragte is. ‘n Aantal Eindige Element Analise (FEA) simulasies is uitgevoer op ‘n dubbel brug elektriese aangedrewe oorhoofse kraan met elastomeriese buffers. Van die stel FEA simulasies kan die invloed van elke parameter op die entbuffer impak_kragte bepaal word. Die maksimum entbuffer impak_kragte is bepaal met behulp van ‘n beperking optimiserings tegniek. Vanaf hierdie resultate is ‘n vergelyking gemaak met die bestaande maksimum ent_buffer impak_kragte vir ‘n enkel brug elektriese oorhoofse aangdrewe kraan met elastomeriese buffers. ‘n Tweede doel rede vir die navorsing was om te bepaal wat die ent buffer impak_kragte op ‘n elektriese aangedrewe oorhoofse kraan met hidrouliese buffers is. Dit is bepaal deur ‘n aantal eksperimentele en numeriese toetse uit te voer. Die numeriese toetse is uitgevoer deur gebruik te maak van ‘n huidige numeriese model van ‘n elektriese aangedrewe oorhoofse kraan wat die kraan en die ondersteunende struktuur as ‘n. Die Eindige Element Analise impak_kragte is gekalibreer teen die eksperimenteel bepaalde impak- kragte. Daarna is ‘n reeks Eindige Element Analise simulasies uitgevoer en sodoende die parameters te verander wat die mees beduidende invloed op die end stop impak_kragte het. Dit het verskeie impak_krag pieke vir verskillende parameters meegebring. Die maksimum impak kragte is bepaal van die impak kragte van die Eindige Element Analise vir ‘n gegewe vlak van betroubaarheid deur gebruik te maak van die beperking optimiserings tegniek. Daarmee saam is die gekodifiseerde ent buffer impak kragte bereken volgen SABS 0160:1989 en die SANS 10160- 6:2010. Vanaf hierdie resultate is ‘n vergelyking gemaak tussen die gekodifiseerde entbuffer impak_kragte en die maksimum impak_kragte wat bepaal is deur die (beperking optimiserings tegniek).

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In this research a Real-Time hydrodynamic optimisation model of the Orange-Fish-Sundays River (OFS) system which uses real-time data in order to forecast release hydrographs, is evaluated. The OFS system stretches over three catchment areas in the Eastern Cape namely Great Fish, Little Fish and Sundays Rivers. The OFS supplies water from the Orange River through a 800 km system of canals, tunnels, dams and rivers to registered water users in this area. In order to cope with increasing pressures on water saving, water demand, water quality and dam safety, the Department of Water Affairs implemented this Orange Fish Sundays-Real Time (OFS-RT) system to calculate the optimal water flow, by running customised Danish Hydraulic Institute (DHI) MIKE11 software. The system utilizes an optimisation module that evaluates the simulated outcome at seven water release structures (dams, weirs and tunnels). Then during the optimisation process performs more adjustments to reach the objectives of the system to obtain the forecast release hydrographs. This OFS-RT model aims at target based objectives, using: (i) Hydras real-time field data of dam water levels, river flows and water quality from the area sent to the control office main computer at four hourly intervals via SMS and (ii) abstractors weekly water requests. This system takes irrigation and domestic demand into account as well as water quality, evaporation, rainfall, dam levels, dam safety, instream flow requirements and tributary flow. In order to manage the water flows through the OFS system the OFS-RT model forecasts the release hydrographs and uploads the predictions to a website to smooth operational procedures. The target outcomes were tested and evaluated during this research and it was found that the OFS- RT model succeeded in delivering release forecasts for the seven control structures to manage the OFS system. This research proved that management of river systems by using a real-time hydrodynamic model with optimisation is a useful tool for the optimal utilisation of water resources. / AFRIKAANSE OPSOMMING: Die doel van hierdie navoring is die evaluering van „n intydse hidrodinamiese optimiseringsmodel van die Oranje-Vis-Sondagsrivier (OVS) stelsel wat intydse data ontvang en loslatings hidrograwe verskaf. Die OVS stelsel strek oor drie opvangsgebiede in die Oos-Kaap: naamlik die Groot Vis-, Klein Vis- en Sondagsriviere en voorsien water vanuit die Oranjerivier deur „n 800 km stelsel van kanale, tonnels, damme en riviere, aan geregistreerde waterverbruikers in die gebied. Ten einde te voldoen aan die eise van waterbesparings, stygende vraag na water, die verskaffing van goeie water gehalte en damveiligheid, het die Departement van Waterwese „n intydse rekenaar model (OVS-IT) geïmplimenteer om die optimale watervloei deur middel van die aangepaste MIKE11 sagteware van die Danish Hydraulic Institute (DHI) te bereken. Hierdie stelsel maak gebruik van „n optimisering module wat die gesimuleerde uitkomste van verstellings aan sewe waterloslatingstrukture evalueer. Met optimisering word die verlangde hidrograaf deur verder aanpassings verkry. Data wat nodig is om die OVS-IT model se doel te bereik is: (i) Hydras intydse velddata van damwatervlakke, riviervloeie en water gehalte van die gebied ontvang deur die beheerkantoor se hoofrekenaar via SMS elke vier ure, en (ii) water verbruikers se weeklikse wateraanvrae Die stelsel neem die besproeiing en huishoudelike aanvraag in ag, sowel as soutgehalte, verdamping, reënval, damvlakke, dam veiligheid, stroom vloei vereistes en sytak byvloei. Die OVS se watervloei word beheer deur voorspelde loslatings hidrograwe, opgesom op „n webwerf wat die uitvoer prosedures aandui. Die intydse hidrodinamiese model met optimisering het volgens hierdie navorsing daarin geslaag om vir die beheer van die OVS stelsel, die loslatings van sewe beheerstrukture akkuraat te voorspel en bevind dat die model „n waardevolle instrument is vir die optimale bestuur van waterhulpbronne.