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

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

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

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

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

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / Doubly symmetric I-section columns are often utilised in portal frame construction. The sheeting (or cladding) is carried by sheeting rails connected to the outer flange of these columns. Although it is common practice to include the sheeting rails in the longitudinal bracing system, by connecting the sheeting rail to the cross-bracing, designers must be wary because the connection between column and sheeting rail will not prevent twisting of the columns cross-section. It has been shown ([11], [12], [17]), that by including this eccentric restraint into the bracing of the column, that a torsional-flexural buckling mode of failure can occur when the column is subjected to axial load only. It was seen that this phenomenon is provided for in BS 5950 [18], but is not present in many other design codes of practice, in spite of this phenomenon being relatively well known. In some cases the compression resistance of a column can be significantly reduced when compared to that of a flexural buckled configuration. Previous work performed by Helwig and Yura [15] proposed specific column to sheeting rail connections which would allow for the sheeting rails to be used as elastic torsional braces and effectively rigid lateral braces. However, it is the objective of this investigation to determine if it is possible to include the eccentric sheeting rails into the bracing system, even when using a relatively simple cleat connection with only two bolts onto the sheeting rail. The objective of the research was investigated by conducting experimental tests coupled with a series of detailed finite element analyses. The purpose of the experimental set-up was to investigate the behaviour of a column laterally supported on one flange by a continuous sheeting rail and to compare it to the behaviour of a column laterally supported on both flanges by means of fly-braces (“kneebraces”). The behaviour of the columns, as determined by the experimental tests, was validated by the finite element analyses. The evident conclusion that can be drawn is that, for the case of a continuous sheeting rail, connected to column simply by two bolts and a cleat, that sufficient torsional restraint is provided to the column to prevent torsional-flexural buckling from being critical. This result is helpful, as it means that the buckling capacity of a column can be increased four-fold by enforcing the second flexural buckling mode instead of the first mode through utilising a continuous sheeting rail connected to a cross-bracing system as longitudinal bracing on the columns. This can be achieved without the need to provide any specific detailing to the column to sheeting rail connection. It is however, recommended that further experimental work be conducted on varying lengths of column in order to further validate the results of this work.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Fibre reinforced concrete (FRC) transforms concrete from a characteristically brittle material to one with a post-crack tensile residual capacity. Its application in industry has varied over the past of which the tensile properties have generally been used in the form of crack mitigation. More recently, the introduction of steel fibres has broadened this scope to structural applications in which the resisting tensile stresses that develop within a steel FRC (SFRC) element can be rather significant. This thesis reviews the existing practices and design models associated with SFRC and the suitability of its implementation as the sole form of reinforcement in in-situ cast flat slab systems. As a material SFRC is dependent on a number of factors which include the fibre type and volume, fibre distributions, element size, as well as the support and applied load conditions. Thus, its performance can be considered rather variable in comparison to conventional concrete should the incorrect practices be implemented. In order to adequately define the material characteristics, it is necessary to use test procedures that accurately reflect on the intended structural application. As a result a number of test procedures have been developed. In addition to this, the post-crack material performance is associated with a non-linear behaviour. This attribute makes the design of structural SFRC elements rather difficult. In an attempt to simplify this, existing design models define stress-strain or stress-crack width relations in which assumptions are made regarding the cross-sectional stress distribution at specified load states. This thesis takes on two parts in defining the suitability of SFRC as the sole form of reinforcement in flat slab systems. The first is a theoretical investigation regarding the micro and macro scale material performance of SFRC, the practices that exist in defining the material properties and its application in structural systems (particularly suspended slab systems), and a breakdown of the existing design models applicable to strain softening deflection hardening SFRC materials. The second part is an experimental program in which the fresh state and hardened state material properties of specified SFRC mix designs defined through flow and beam testing respectively. These properties are then implemented in the design and construction of full scale flexural and punching shear test slabs in an attempt to verify the theory applied. The investigation reveals that the use of SFRC significantly improves the ductility of concrete systems in the post-crack state through fibre crack bridging. This ductility can result in deflection hardening of flat slab systems in which the redistribution of stresses increases the load carrying capacity once cracking has taken place. However, the performance of large scale test specimens is significantly influenced by the construction practices implemented in which the material variability increases as a result of non-uniform fibre distributions. The results indicate that the load prediction models applied have potential to adequately predict the ultimate failure loads of SFRC flat slab systems but however cannot account for possible non-uniform fibre distributions which could result in premature failure of the system. / AFRIKAANSE OPSOMMING: Vesel versterkte beton (VVB) verander beton van die kenmerkende uiters bros material na ‘n material met ‘n residuele post-kraak trekkapasiteit. Die toepassing daarvan in die bedryf het in die verlede gewissel en die trek eienskappe is oor die algemeen gebruik vir kraak vermindering. Meer onlangs het die bekenstelling van staal vesel hierdie omvang verbreed na die strukturele toepassings waar trekspannings wat ‘n VVB element kan weerstaan noemenswaardig kan wees. Hierdie tesis ondersoek bestaande praktyke en ontwerpmodelle met die oog op staalvesel versterkte beton (SVVB) en die geskiktheid van die implementering daarvan as die enigste vorm van bekisting in in-situ gegiete plat blad stelsels. As ‘n materiaal, is SVVB afhanklik van ‘n aantal faktore wat die tipe vesel en volume, vesel verspreiding, element grootte, sowel as die randvoorwaardes tipe aangewende las insluit. As gevolg hiervan, kan die gedrag van SVVB, wat korrek geïmplimenteer word, as redelik varieerbaar beskou word wanneer dit met konvensionele beton vergelyk word. Ten einde die materiaaleienskappe voldoende te definieer, is dit noodsaaklik dat prosedures wat die strukturele toepassing akuraat voorstel, getoets word en daarom is ‘n aantal toets prosedures ontwikkel. Verder het die post-kraak materiaalgedrag ‘n nie-lineêre verband wat struktuurontwerp met SVVB redelik moeilik maak. Om dit te vereenvoudig, definieer bestaande ontwerpmodelle spanning-vervorming of spanning-kraakwydte verhoudings waarin aannames gemaak word ten opsigte van die spanningsverdeling oor ‘n snit, gegewe sekere lastoestande. Hierdie studie bestaan uit twee dele wat die geskiktheid van SVVB as die enigste vorm van bikisting in plat blad stelsels definieer. Die eerste deel bestaan uit ‘n teoretiese ondersoek wat handel oor die mikro- en makro-skaal materiaalgedrag van SVVB, die praktyke wat bestaan om die materiaaleienskappe en toepassing in strukturele sisteme (spesifiek opgelegde blad stelsels) te definieer, en ‘n uiteensetting van die bestaande ontwerpmodelle wat van toepassing is vir defleksie as gevolg van vervormingsversagting wat SVVB material verhard. Die tweede deel bestaan uit ‘n eksperimentele program waarin die materiaaleienskappe van gespesifiseerde SVVB meng-ontwerpe in die vars toestand en in die verharde toestand gedefinieer word deur middel van vloei- en balktoetse onderskeidelik. Hierdie eienskappe word dan toegepas vir die ontwerp en konstruksie van volskaalse buig- en ponsskuif toetsblaaie ten einde die modelle en teorie wat toegepas is, te bevestig. Die ondersoek toon dat die gebruik van SVVB die duktiliteit van beton sisteme noemenswaardig verbeter in die post-kraak toestand deur kraak oorbrugging. Hierdie duktiliteit kan defleksie verharding van plat blad stelsels veroorsaak waarin die herverdeling van spannings, nadat kraking plaasgevind het, die lasdraende kapasiteit verhoog. Die gedrag van die grootskaalse toetsmonsters word egter noemenswaardig beïnvloed deur die konstruksiemetodes wat geïmplementeer word waarin die materialveranderlikheid toeneem as ‘n gevolg van nie-uniforme vesel verdelings. Die resultate dui daarop dat die modelle wat toegepas is om die laste te voorspel, die potensiaal het om die grens falingslas van SVVB plat blad stelsel voldoende te voorspel, maar neem nie moontlike nie-uniforme veselverdelings wat kan lei tot vroeë faling van die stelsel in ag nie.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / In many part of the world, but especially in Africa, land degradation leads to severe soil erosion and high sediment yields. Mathematical models and empirical methods can be used to simulate the sediment yields. In many cases spatial and temporal data are however limited in the large catchments often found in Africa. A model should be able to simulate the long-term hydrology and sediment yields for sub-catchments and should be physically based as far as possible. In this thesis several models were evaluated and the agrohydrological model of the University of Kwa- Zulu-Natal (ACRU) was applied on two large catchments with limited data in Kenya. The key aim of the thesis was to assess the applicability of the ACRU modelling system for sediment yield prediction in large catchments under conditions of limited data availability. Two catchments in Kenya which drain into Lake Victoria were selected for this research: Nyando (3562 km2) and Nzoia River (13692 km2). Lake Victoria, with a surface area of 68000 km2 and an adjoining catchment of around 184200 km2, is the second largest fresh water lake in the world and the largest in the tropics. The Lake Victoria Basin area is increasingly being used for domestic, agricultural and industrial purposes by the three riparian countries Kenya, Tanzania and Uganda. About 21 million people (year 2000) rely primarily on subsistence agricultural and pastoral production for their livelihoods. But pervasive poverty has hindered sustainable use of the land resources and there has already been considerable land degradation. There has also been expansion of the increasing on-site erosion (overland flow) and reducing buffering capacity of the natural vegetation in wetlands and in the riparian zones (Hansen, Walsh, 2000). A regional assessment identified the Nyando River Basin and Nzoia River Basin as major sources of sediment flow into Lake Victoria on the Kenyan side of the Lake. Accelerated run off sheet erosion over much of the Nyando catchment area has led to severe rill, gully and stream bank erosion in lower parts of the river basin (Swallow, 2000). The ACRU model is a hydrological model using daily time steps with the Modified Universal Soil Loss Equation (MUSLE, Williams, 1975) module to simulate soil erosion. The MUSLE sediment yield module uses factors that characterize physical conditions on the surface of a catchment as input information. Data required for the model include: sub-catchment daily rainfall, historical flow records, general catchment topographical information, meteorological information, land use and cover, soil characteristics, sediment yield data, etc. The model used daily time steps for a 55 years record for the period 1950 to 2004. During calibration it was found that the sediment yield is overestimated which was expected since the model is a soil erosion model (based on MUSLE). The model was calibrated in each catchment against observed sediment load data, but this data were limited. Verification of the model was carried out by using satellite images and independent sediment load data when available. Scenario analysis was carried out by changing land use in the model to investigate how soil erosion could be reduced. Grassland to replace subsistence farming was found most effective, but irrigated sugarcane was also investigated. The model was found to be very effective in indicating which sub-catchments contribute most of the sediment yield. Under limiting data conditions it was found that it is very important to calibrate the model against field data. The most sensitive parameters affecting the sediment yield were found to be: a) Hydrological: • Daily rainfall spatial distribution of rain gauge • Time of concentration • Mean annual precipitation • Minimum and maximum temperature • Monthly evaporation b) Soil and catchment characteristics: • Number of sub-catchments making up catchment in model • Catchment slope and slope length, steepness factor • Land cover • Crop coefficient • Soil texture class and depths • Soil erodibility factor

Thesis (PhD (Civil Engineering))--University of Stellenbosch, 1989. / ENGLISH ABSTRACT: Several aspects related to the estimation and selection of design wave conditions were investigated. An analysis program which includes strict quality control routines was developed for digital Waverider data. All available Waverider data from deepsea records were analysed with this program. A remarkable similarity in simultaneously recorded wave heights between Cape Town and Port Elizabeth was found. This similarity was used to compile a near continuous wave record over an eight year period for the Southern Cape coast. The 10537 values of significant wave height (Hmo) which made up the record for the Southern Cape were found to give a good visual fit to the Extreme I and Log-normal distributions over the entire range of Hmo values. Design wave heights derived from the Extreme I distribution were found to be insensitive to assumptions regarding the independence and identical distribution of the wave height samples and the method used for parameter estimation. Design wave heights for the coastline between Oranjemund and Port Elizabeth were found to be strongly correlated to the latitude of the recording site. High waves along these coasts are invariably caused by the passage of cold fronts past the southern tip of the continent. Wave heights reduce as the distance from the west to east route of these cold fronts increase, thus the reason for the abovementioned correlation. No deepwater wave records are available east of Port Elizabeth. Shallow water records indicate that a reduction in wave height can be expected between Port Elizabeth and East London.

Thesis (PhD (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In both developing and developed countries, to ensure sustained economic growth the quest for optimal roads performance is an extremely high priority. A global increase in the use of foamed bitumen and bitumen emulsion materials (BSMs) as a solution to roads maintenance, rehabilitation, and upgrading has become evident. This is driven by environmental policies aimed at conserving energy and limiting the exploitation of new borrows pits. It has therefore become imperative that BSMs are used optimally, and, in order to achieve this, practitioners need to understand the mechanisms that influence durability and long-term performance. The changes in the behaviour of materials and the failure mechanisms of BSM mixes are long-term phenomena. This implies that the study of the physicochemical and mechanical properties of the mixes is vital. Therefore, a fundamental understanding of the moisture damage and age-hardening characteristics, which are related to materials’ properties, is required. The main objective of this study is to advance BSM technology by assessing the influence of the selected materials on durability behaviour and long-term performance in all phases of application (i.e. mix design, construction, and in-service condition). This study begins with a comprehensive literature review of research dealing with the interactions of binder and mineral aggregates. The properties of bitumen (foamed bitumen or bitumen emulsion) and mineral aggregates were reviewed. This was followed by review into the colloidal behaviour of foam and emulsion and physicochemical and mechanical interaction with mineral aggregates. Factors influencing the interaction of BSMs were then identified. Finally, the fundamental theories on thermodynamics, hydrodynamics, and electrokinetics were used to describe the step-by-step process by which adhesive bonding and cohesion occur in BSMs. The mixture durability in terms of moisture damage was investigated. To achieve this aim, the physical and mechanical moisture-induced damage process was analysed. The test control parameters were established and a laboratory device to quantify these parameters designed. New moisture conditioning procedures were developed and demonstrated in this study. From the moisture induction simulation test (MIST) procedure, it became evident that pulsing water pressures into compacted and cured BSM mixes simulates the hydrodynamic effect that occurs in the field due to dynamic traffic loading. The different mix matrices typically applicable to the recycling processes – such as Hornfels-RAP and Quartzite crushed stone, stabilised with either foamed bitumen or bitumen emulsion and the addition of active filler (cement or lime) – were investigated. It was found that a new moisture-conditioning procedure using the MIST device and monotonic triaxial testing can distinguish those BSM mixes that are resistant to moisture damage from those that are less resistant. The validation of the MIST and monotonic test results was done using the APT device, which is the MMLS3 wet trafficking test. The results on both tests showed good correlations in evaluating and screening BSMs in terms of moisture susceptibility. Field temperature data was collected and a model to accurately simulate the curing of BSMs was identified and proposed for further investigation and validation. It was found from the field temperature data collected in this study that the temperature gradient on the study site varied according to the depth of the BSMs (that is, 10oC-17oC during winter and 17oC– 47oC during summer). Understanding the influence of the temperature conductivity and rate of evaporation is important for inferring moisture damage and age-hardening behaviour and proper selection of BSMs. The age-hardening behaviour of BSMs is linked to the durability properties and longterm performance of these materials. The fundamental characteristics associated with shortand long-term age hardening were investigated in this study. The short-term dimension involved assessing the age-hardening characteristics of the binder (foamed bitumen colloids and bitumen emulsion droplets) prior to the production of BSMs. The long-term study involved extracting and recovering the binder from the briquettes (made from different mixes) compacted in the laboratory and cores extracted from different field pavement sections which were in service for 8-10 years. The study found that the length of time bitumen is kept in circulation in the laboratory plant at elevated temperature (170oC–180oC) before making BSM-foam contributes to the ageing of the binder, especially after eight hours. The foaming process in itself was found not to alter the bitumen properties. It is recommended that a temperature range between 160oC- 165oC be used for the production of foamed bitumen with softer bitumen. This will not compromise its quality. In addition, the time of circulation of bitumen in laboratory plant should not be longer than three (3) hours. The rheological properties of the bitumen recovered from laboratory briquettes and cores from field pavement show that age hardening on foamed bitumen and bitumen emulsion during in-service life occurred. The ageing also seemed to be dependent on the effect of traffic, with trafficked areas (i.e. on-wheel path and inner-wheel path) experiencing more ageing than untrafficked areas (i.e. between-wheel path). However, the extraction and recovery process was found to be complex, and produce uncertain results. Although the results show that binders in BSMs undergo age hardening, its distinct behaviour in BSM performance was not obvious from the extensive tests carried out in this study. The last part of the study contains its conclusions and recommendations. The study provides an insight into fundamental material durability properties, and this will assist in improving the current procedure for selection, combining and formulation of the mix matrices for BSMs. In addition, the study provides guidelines that will enable practitioners to confidently apply a mix that is durable and long-lasting. The specific durability-related issues addressed in this study are substance for future research. This novel solution to the application of BSMs will benefit all parties involved in the development of pavement recycling technology. / AFRIKAANSE OPSOMMING: Om volgehoue ekonomiese groei te verseker in beide ontwikkelende en ontwikkelde lande, geniet die soeke na die optimale werkverrigting van paaie ’n baie hoë prioriteit. ‘n Wêreldwye toename in die gebruik van skuimbitumen en bitumen-emulsiemateriale (BSMs) as ’n oplossing vir padonderhoud, rehabilitasie en opgradering is merkbaar. Dit word meegebring deur die omgewingsbeleide wat die ontginning van nuwe leengroewe beperk en besparing van energie bevorder. Die korrekte gebruik van hierdie materiale vereis dat die meganismes wat die duursaamheid en langtermyn-werkverrigting daarvan beïnvloed, deeglik verstaan word. Die verandering in materiaalgedrag en falingsmeganismes van BSM materiale is langtermynverskynsels. Dit impliseer dat bestudering van die fisiochemiese en meganiese eienskappe van die mengsels uiters belangrik is. Dis dus voor die hand liggend hoe belangrik vogbeskadiging en verharding met tyd, wat verwant is aan materiaaleienskappe, is. Die hoofdoelwit met hierdie studie is om die vooruitgang van BSM tegnologie te versnel deur dit moontlik te maak om gekose materiale te evalueer op grond van hulle invloed op duursaamheid en langtermyn-werkverrigting in alle toepassingsfases (naamlik mengontwerp, konstruksie en dienstoestand). Hierdie studie begin met ’n uitgebreide literatuuroorsig oor fundamentele begrippe van die karakterisering van interaksie van die bindstof en die minerale-aggregate. Inligting oor bitumen (skuimbitumen en bitumen emulsies) en eienskappe van minerale aggregate is bestudeer. Dit is gevolg deur ’n studie van die fundamentele begrip van die kolloïdale gedrag van skuim en emulsie, asook fisiochemiese en meganiese interaksie met minerale aggregate. Faktore wat die interaksie van BSM-materiale beïnvloed is geïdentifiseer. Die basiese teorie van termodinamika, hidrodinamika en elektrokinetika is daarna gebruik om stap vir stap die proses en formulering van adhesie-binding en kohesie in die BSMs, wat in hierdie studie aangebied word, te beskryf. Die kwantifisering van mengsel-duursaamheid in terme van vogbeskadiging is ontwikkel. Om hierdie doel te bereik, is die fisiese en meganiese proses van beskadiging deur vogindringing geïdentifiseer. Die gekontroleerde parameters is bepaal en ’n laboratoriumapparaat is ontwerp om hierdie parameters te kwantifiseer. Nuwe vogkondisioneringsprosedures is ontwikkel en in hierdie studie gedemonstreer. Van prosedures van voggeïnduseerde sensitiwiteitstoetsing (Engels: moisture induction simulation test (MIST)) was dit duidelik dat pulsering van waterdruk in BSM materiale die hidrodinamiese effek naboots wat in die veld bestaan as gevolg van dinamiese verkeerslaste. Verskillende mengselmatrikse wat tipies is van hergebruik, soos byvoorbeeld hoornfels-hersikleerde asfalt produk (Engels: recycled asphalt product (RAP)) en vergruisde granietklip, met skuimbitumen of bitumenemulsie gestabiliseer en met byvoeging van aktiewe vulmateriaal (sement of kalksteen), is ondersoek. Daar is bevind dat nuwe vogkondisioneringsprosedures (soos bepaal deur MIST apparaat en drie-assige toets) kan onderskei tussen BSM materiale wat weerstandig is teen vogbeskadiging en dié wat minder weerstandig (vatbaar) is. Die geldigheid van die MIST en monotone toetsresultate is bepaal deur gebruik van die APT apparaat wat ’n MMLS3 nat verkeerstoets is. Die resultate van beide toetse toon goeie korrelasie in die keuring van BM materiale in terme van vogvatbaarheid. In hierdie ondersoek is veldtemperatuurdata versamel en die toepaslike model om verouderende BM lae akkuraat te simuleer is geïdentifiseer en voorgelê vir verdere ondersoek en verifikasie. Daar is uit veldtemperatuurdata bevind dat temperatuurgradiënt op die betrokke terrein gewissel het met die dikte van die BSM, naamlik 10oC-17oC gedurende die winter en 17oC-47oC gedurende die somer. Begrip vir die invloed van temperatuuroordragkoëffisiënt en verdampingstempo is belangrik by die afleiding van vogbeskadiging en verharding met ouderdom en die korrekte keuse van BSM materiale.Verouderingsverhardinggedrag van BSMs is verwant aan die duursaamheidseienskappe en langtermynwerkverrigting van hierdie materiale. Die basiese karakteristieke wat met kort- en langtermyn verouderingsverharding geassosieer word, is in hierdie studie ondersoek. Die klem op die kort termyn is geplaas op die verouderingsverhardingsgedrag van die bindstof (skuimbitumen kolloïdes en bitumen-emulsiedruppels) voordat BSMs vervaardig word. In die lang termyn evaluasie het die studie ekstraksie en herwinning van bindstof uit brikette wat in die laboratorium gekompakteer is (van verskillende mengsels) en uit kerns verkry vanaf verskeie plaveiselgedeeltes na 8-10 jaar diens ingesluit. Die ondersoek het bevind dat die tydsverloop waarin bitumen in sirkulasie gehou is by verhoogde temperatuur (170oC-180oC) in die laboratorium-aanleg voordat BSMs vervaardig is, veral indien na 8 uur, bydra tot die veroudering van die bindstof. Die skuimproses op sigself verander nie die bitumeneienskappe nie. Daar word aanbeveel dat temperature tussen die grense 160oC-165oC gehandhaaf word vir produksie van skuimbitumen met sagter bitumen sonder dat die kwaliteit benadeel word en dat die sirkulasietyd nie 2 tot 3 ure behoort te oorskry nie. Die reologiese eienskappe van die herwinde bitumen vanuit laboratoriumbrikette en kerns van plaveisels toon dat ouderdomsverharding van skuimbitumen en bitumen-emulsie tydens die diensleeftyd plaasvind. Die veroudering is skynbaar ook afhanklik van verkeerseffekte, met belaste areas (in wielspoor of binne wielspoor) wat ’n hoër mate van veroudering toon as onbelaste areas (tussen wielspore). Die ekstraksie- en herwinningsproses op sigself was egter bevind as baie kompleks met uiters onseker resultate. Dit het gelei tot onsekere gedrag in terme van ouderdomsverharding van die BSM bindmiddel (skuim of emulsie). Alhoewel resultate toon dat die bindmiddels ouderdomsverharding ondergaan het, is die BSM werkverrigting nie duidelik uit die uitgebreide toetse wat in hierdie studie uitgevoer is nie. Die laaste deel van die studie bevat gevolgtrekkings en aanbevelings. Die studie lewer insig in die fundamentele duursaamheidseienskappe van die materiaal, wat bydra tot verbetering van die huidige prosedure van seleksie, saamstelling en formulering van die mengmatriks vir BSMs. Verder voorsien dit ’n metode wat in die praktyk gebruik kan word om met vertroue duursame mengsels met lang diensbaarheidsleeftye te vervaardig. ’n Nuwe oplossing en vooruitgang in die toepassing van BSMs is daargestel tot voordeel van alle partye betrokke by die ontwikkeling van herwinningstegnologie.