Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / This research provides and overview of sea storms around the South African Coast in terms of weather types, characteristic wave statistics, storm processes and wave energy. Sea Storm Profiles are unique to the particular storm events causing them, but they can be associated with Equivalent Wave Energy (EWE) Storm Profiles, which are representative of them and have a linear, symmetric, “Capital Lambda” ( Λ ), shape. The actual storm profile and the EWE Profile are equivalent in wave energy, and the benefit of the EWE is that it is regular and can be can be readily compared with another EWE Storm Profile for analysis, and for the comparison of impacts. The ability to compare the impacts of Sea Storms from different areas, on the basis of characteristic Equivalent Wave Energy (EWE) Storm Profiles within the South African Coastal Regions, is considered to be advantageous. This will allow Engineers to apply the knowledge gained in one area to another with a similar EWE Storm Profile, with more confidence. There will always be the need for site-specific investigations, data recording, data analysis and interpretations in Coastal Engineering Work, but one needs to start with an understanding of the general nature of the coastal region in which one is working. This research adds to the background “Body of Knowledge” relating to the character of the sea storms in the Regions around South Africa. The study is based on a literature survey of atmospheric weather, sea wave theory and wave climates, as well as the analysis of weather and sea state data at selected recording stations around the South African Coastline.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH SUMMARY: It is found that the serviceability limit state often governs the design of slender reinforced concrete members. Slender flexural members often have a percentage tension reinforcement less than 1.0% and an applied bending moment just above the point of first cracking. For such members, the available methods to evaluate the serviceability conditions produce inadequate and unrealistic results. The evaluation of the serviceability of a slender member includes the calculation of the predicted deflection, either by empirical hand-calculation or analysing a finite element model, and the verification using the span-to-effective-depth ratio. The focus of the study is on flat slab structures. It investigates the different deflection prediction methods and the span-to-effective-depth ratio verifications from various design standards. These design standards include the ACI 318 (2002), the SABS 0100-1 (2000), the EC2 (2004) and the BS 8110 (1997). The background to the methods, as well as the parameters which influences the deflection development for lightly reinforced members, are investigated in order to define the limitations of the methods. As a result of the investigation of the deflection calculation methods, an Alternative Approach is suggested and included in the comparisons of the various methods. The deflection prediction methods and the span/effective depth verification procedures are accurately formulated to predict the serviceability behaviour of beams. Additional approaches had to be used to apply these methods to a two-dimensional plane such as that of a flat slab structure. The different deflection prediction methods and the span/effective depth verification methods are calculated and compared to the recorded data of seven experimental flat slab specimens as performed by others. A study by Gilbert and Guo (2005) accurately recorded the flexural behaviour of flat slab specimens under uniformly distributed loads for test periods up to 750 days. The methods to evaluate the serviceability of a slender member were also applied to slab examples designed using South African standards. The study concludes by suggesting a suitable deflection prediction method for different parameter (limitation) categories with which a slender member can comply to. The typical span/effective depth ratio trend is also presented as the percentage tension reinforcement for a slender member changes. It is observed that the empirical hand-calculation methods present more reliable results than those of the finite element models. The empirical hand-calculation methods are accurate depending on the precision to which the slab was constructed relative to the actual slab design. The comparison of the deflection methods with South African case studies identified the role played by construction procedures, material parameters and loading history on slab behaviour. / AFRIKAANSE OPSOMMING: Die diensbaarheidstoestand is in baie gevalle die bepalende faktor vir die ontwerp van slank gewapende beton elemente bepaal. Slank elemente, soos lig bewapende buigbare beton elemente, het gewoonlik ‘n persentasie trekbewapening van minder as 1.0% en ‘n aangewende buigmoment net wat net groter is as die punt waar kraking voorkom. Die metodes beskikbaar om die diensbaarheid van sulke elemente te evalueer gee onvoldoende en onrealistiese resultate. Die evaluering van die elemente in die diensbaarheidstoestand sluit in die bepaling van defleksies deur berekening of die analise van ‘n eindige element model, en die gebruik van die span/effektiewe diepte metode. Die fokus van die studie is platbladstrukture. Die doel van die studie is om die verskillende metodes vir die bereking van defleksie asook die verifikasie volgens span/effektiewe diepte metodes van die verskillende ontwerp standaarde te ondersoek. Die ontwerp standaarde sluit die ACI 318 (2002), SABS 0100-1 (2000), EC2 (2004) en die BS 8110 (1997) in. Die agtergrond van hierdie metodes is ondersoek asook die parameters wat ‘n rol speel, sodat die beperkings van die metodes geidentifiseer kan word. As ‘n gevolg van die ondersoek na die beperkings van die metodes, is ‘n Alternatiewe Benadering voorgestel. Die Alternatiewe Benadering is saam met die metodes van die ontwerpstandaarde gebruik om die verskille tussen die metodes te evalueer. Die defleksievoorspelling en die span/effektiewe diepte verifikasie metodes is korrek geformuleer om die diensbaarheid van balke te evalueer. Ander benaderings was nodig om die diensbaarheid van blad blaaie te toets. Die onderskeie defleksievoorspelling en span/effektiewe diepte metodes is bereken vir sewe eksperimentele plat blaaie soos uitgevoer deur ander navorsers. Gilbert and Guo (2005) het ‘n studie uitgevoer waar die buigingsgedrag van die sewe plat blaaie, met ‘n uniforme verspreide las vir ‘n toetsperiode van tot 750 dae, akkuraat genoteer is. Die metodes om die diensbaarheid van ‘n slank element te toets, was ook op Suid-Afrikaanse blad voorbeelde getoets. Dit was gedoen om die Suid- Afrikaanse ontwerp van ligte bewapende beton elemente te evalueer. Die gevolgetrekkings stel ‘n gepaste defleksie metode vir ‘n slank element vir verskillende beperking kategorië voor. Dit is ook verduidelik hoe die tipiese span/effektiewe diepte verhouding met die persentasie trek bewapening vir ‘n slank element verander. Dit is bevind dat die imperiese handmetodes om defleksies te bereken, meer betroubaar as die eindige element modelle se resultate is. Die imperiese handberekening metodes is akkuraat relatief tot hoe akkuraat die blad konstruksie tot die blad ontwerp voltooi is. ‘n Vergelyking van defleksieberekening met Suid-Afrikaanse gevallestudies het die belangrikheid van konstruksieprosedures, materiallparamteres and belastingsgeskiedenis geïdentifiseer.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / Stepped spillways constructed of roller compacted concrete (RCC) is a hydraulic and cost effective measure to dissipate energy of large water flows over the spillway of a dam. Stepped spillways, like other spillway types, have its limitations and a measure to improve the energy dissipation effectiveness is proposed. Two hydraulic models were constructed at the hydraulics laboratory of the Department of Water Affairs and Forestry (DWAF) in Pretoria, South Africa. The scales of the models were 1:20 and 1:30. The study proposes the use of triangular protrusions applied over the spillway surface. The protrusions have the same height as the steps, with the width of the protrusions varying. The triangular protrusions deflect the water sideways resulting in higher energy losses. The results indicate that the protrusions reduce scouring at the toe of the dam, thus increasing the roughness of the steps. It also indicate that aeration occur earlier than with normal stepped spillways. An optimal spacing, lateral and across the steps, are proposed. The construction of the protrusions is also discussed, as well as the cost implications. It is concluded that the protrusions are effective at a unit discharge up to 35 m3/s.m. This value is however dependent on the configuration of the apron downstream of the toe of the dam. It is proposed that protrusions be added on the downstream face of the dam on every second step, with one protrusion and then no protrusion alternating in the flow path. It is recommended that the protrusions be cast in situ.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2008. / This thesis is an investigation of the wave power resource on the South African coast, focusing on the spatial distribution of wave power of the coastal region exposed to the highest wave power. The study’s main objective is to provide a detailed description of the spatial distribution of wave power to assist in the selection of locations for deployment of Wave Energy Converter (WEC) units in this zone. The study methodology employed to achieve this main objective entails an analysis of measured wave data recorded at wave recording stations distributed along the South African coast. The analysis provided a general description of wave power at locations for which wave data exist. From this analysis it was found that the South West Coast is exposed to the highest wave power, with an average wave power of approximately 40 kW per meter wave crest. The rest of the South African coast is exposed to average wave power between approximately 18 kW/m to 23 kW/m. The wave power characteristics on the South West Coast region (from Cape Point to Elands Bay) were therefore the focus of this thesis. The study objective was achieved by transferring deep sea wave data into the nearshore South West Coast study area with the Simulating WAves Nearshore (SWAN) wave model. The deep sea wave data was obtained from a 10 year period of available hindcast data. A simplified simulation procedure was required in order to make the study practically feasible. A sensitivity analysis was carried out to determine the validity of the simplified simulation procedure and it was found that the procedure slightly overestimate wave power in the shallower water regions due to the underestimation of energy dissipation processes. This overestimation was deemed acceptable for the dominant wave conditions and the simplified model was therefore applied in the study. An appropriate programming system was developed and used to transfer the available 10 year deep sea wave data into the selected South West Coast region. From this exercise spatial distribution of wave power and related statistical parameters were obtained for the study area. The accuracy of the modelled output was investigated by directly comparing it to wave data recorded during the overlapping recording period. It was found that the model slightly overestimates the monthly wave power resource compared to the measured data with a maximum overestimation of 9%; which is sufficiently accurate for the purpose of the study. The results of this investigation can be used for the identification of areas of high wave power concentration within the study area for the location of WEC units. Further numerical modelling is required for the detailed design of wave farms, especially if potential sites are located in shallow water (shallower than approximately 50 m). / Centre for Renewable and Sustainable Energy Studies

Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: A study of the state of reservoir sedimentation in South Africa based on reservoir sediment deposit data, has shown that a considerable number of reservoirs have serious sedimentation problems. The analysis of the reservoir sediment deposit data showed that almost 25% of the total number of reservoirs have lost between 10 to 30% of their original storage capacity. The average storage loss due to sedimentation in South African reservoirs is approximately 0.3% per year while the average annual storage loss for all the reservoirs in the world is 0.8%. The aim of this research was to develop sediment yield prediction methods based on analytical approaches and mathematical modelling. The sediment yield prediction methods can be used in planning and management of water resources particularly in reservoir sedimentation control. The catchment erosion and sediment yield modelling methods can be applied in temporal and spatial analysis of sediment yields which results are essential for detailed design of water resources, particularly in the identification of critical erosion areas, sediment sources and formulation of catchment management strategies. Current analytical methods for the prediction of sediment yield have been reviewed. Nine sediment yield regions have been demarcated based on the observed sediment yields and catchment characteristics. Empirical and probabilistic approaches were investigated. The probabilistic approach is based on analysis of the observed sediment yields that were calculated from reservoir sediment deposit, river suspended sediment sampling data and soil erodibility data. The empirical equations have been derived from regression analysis of the variables that were envisaged to have a significant effect on erosion and sediment yields in South Africa. Empirical equations have been developed and shown to have accurate and reliable predictive capability in six of the nine regions. The probabilistic approach has been recommended for the prediction of sediment yields in the remaining three regions where reliable regression equations could not be derived. The predictive accuracy of both the probabilistic and empirical approaches was checked and verified using the discrepancy ratio and graphs of the observed and calculated data. While the analytical methods are needed to predict the sediment yield for the whole catchment, mathematical modelling to predict sediment yields is applied for more detailed analysis of sediment yield within the catchment. An evaluation of available catchment sediment yield mathematical modelling systems was carried out. The main criteria for the choice of a numerical model to be adopted for detailed evaluation was based on the following considerations: the model’s capabilities, user requirements and its application. The SHETRAN model (Ewen et al., 2000) was therefore specifically chosen because of its ability to simulate relatively larger catchment areas (it can handle catchment scales from less than 1km2 to 2500km2), its ability to simulate erosion in channels, gullies and landslides, its applicability to a wide range of land-use types and ability to simulate land use changes. Another model, ACRU (Smithers et al., 2002) was also reviewed. The aim of the model evaluation was to provide a conceptual understanding of catchment sediment yield modelling processes comprising model set up, calibration, validation and simulation. The detailed evaluation of the SHETRAN model was done through a case study of Glenmaggie Dam in Australia. The flow was calibrated and validated using data from 1975 to 1984, and 1996 to 2006 respectively. The results for both the calibration and validation were reasonable and reliable. The sediment load was validated against turbidity derived sediment load data from 1996 to 2006. The model was used to identify sources of sediment and areas of higher sediment yield. The land use of a selected sub-catchment was altered to analyse the impact of land use and vegetative cover on the sediment yield. Based on the results, the SHETRAN model was confirmed to be a reliable model for catchment sediment yield modelling including simulation of different land uses. / AFRIKAANSE OPSOMMING: ‘n Studie van die stand van damtoeslikking in Suid-Afrika toon dat daar ernstige toeslikkingsprobleme by baie reservoirs bestaan. ’n Ontleding van die toeslikkingsyfers gegrond op damkomopmetings toon dat omtrent 25% van die totale getal reservoirs tussen 10 en 30% van hulle oorspronklike opgaarvermoë verloor het. Die gemiddelde tempo van damtoeslikking in Suid-Afrika is 0.3%/jaar, wat laer is as die wêreld gemiddeld van 0.8%/jaar. Die oogmerk met hierdie navorsing was om sedimentlewering voorspellingsmetodes te ontwikkel deur gebruik te maak van analitiese metodes en wiskundige modellering. Die sedimentlewering voorspellingsmetodes kan gebruik word vir die beplanning en bestuur van waterbronne en veral vir damtoeslikking beheer. Die opvangsgebied erosie en die sedimentlewering modelleringsmetodes kan toegepas word in tydveranderlike en ruimtelike ontleding van sedimentlewering. Hierdie inligting word benodig vir die detail ontwerp van waterhulpbronne en veral vir die identifisering van kritiese erosiegebiede, bronne van sediment en die formulering van opvangsgebied-bestuur strategië. ‘n Literatuuroorsig oor die huidige metodes vir die voorspelling van erosie en sedimentlewering is gedoen. Nege sedimentasie streke is afgebaken in Suid-Afrika, gegrond op waargenome damtoeslikkingsdata en opvangsgebied-eienskappe. Proefondervindelike en waarskynlikheidsbenaderinge is ondersoek. Die waarskynlikheidsbenadering is gegrond op die ontleding van waargenome damtoeslikking wat bereken is uit reservoir opmeting data en rivier gesuspendeerde sediment data, asook data oor gronderosie. Die proefondervindelike metode se vergelykings is afgelei vanuit regressie ontleding van die veranderlikes wat ‘n belangrike invloed het op die erosie en sedimentlewering in Suid-Afrika. Daar is bevestig dat die ontwikkelde proefondervindelike (empiriese) vergelykings ‘n akkurate en betroubare voorspellingsvermoë in ses van die nege streke het. Die waarskynlikheidsbenadering is aanbeveel vir die voorspelling van sedimentlewering in die ander drie streke, waar betroubare regressie vergelykings nie afgelei kon word nie. Die voorspellingsakkuraatheid van albei metodes is nagegaan en bevestig deur gebruik te maak van die teenstrydigheidsverhouding en grafieke van die waargenome en berekende data. Analitiese metodes van sedimentleweringsvoorspelling is nodig vir ‘n volle opvangsgebied, terwyl wiskundige modellering om sedimentlewerings te voorspel gebruik kan word om ‘n meer in diepte ontleding van die sedimentlewering binne ‘n opvanggebied te doen. ‘n Evaluasie van beskikbare wiskundige modelle wat opvangsgebied sedimentlewering kan voorspel, is gedoen. Die hoofkriteria vir die keuse van ‘n model vir gebruik by gedetailleerde ontleding is gegrond op die volgende: die vermoëns van die model, wat verbruikers benodig en die aanwending van die model. Die SHETRAN model (Ewen et al., 2000) is spesifiek gekies weens sy vermoë om relatief groter opvangsgebiede te simuleer (dit kan opvangsgebiede van 1km2 tot 2500km2 wees) asook om erosie in kanale, dongas en grondverskuiwing simuleer. Dit kan toegepas word op ‘n wye reeks grondtipes en kan ook die gevolge simuleer as die gebruik van die grond verander. ‘n Ander model, ACRU (Smithers et al., 2002) is ook ondersoek. Die doel van die modelevaluering was om ‘n konseptuele begrip te kry van sedimentlewering modelleringsprosesse wat die opstelling, kalibrasie, toetsing en simulasies insluit. Die volledige evaluasie van SHETRAN is gedoen deur middel van ‘n gevalle-studie van die Glenmaggiedam in Australia. Die riviervloei is gekalibreer en getoets deur gebruik te maak van data wat strek van 1975 tot 1984, en van 1996 tot 2006 onderskeidelik. Die resultate van beide die kalibrasie en die toetswas redelik en betroubaar. Die sedimentlading is gekalibreer teen velddata van 1996 tot 2006. Die model is gebruik om bronne van sediment te identifiseer, asook gebiede met ‘n hoër sedimentlewering. Die gebruik van die grond op ‘n gekose sub-opvangsgebied is verander om die impak van grondgebruik en plantbedekking op sedimentlewering te ontleed. Die resultate bewys dat die SHETRAN model ‘n betroubare model is vir groot opvangsgebied sedimentlewering modellering, asook vir die simulasie van verskillende grondgebruike.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Calculation of longshore sediment transport rates is a typical part of coastal engineering work. One of the important inputs to such calculations is the sediment grain size. A single, representative grain size is typically required. The inter-tidal beach is the most convenient and common area from which grain size data can be obtained. Yet only a fraction of the longshore transport occurs at the beach, with the bulk of the transport occurring in the surf zone, where sampling is difficult. Sediment transport calculations can be improved if the representative grains size is also characteristic of this area. A better understanding how the grain size in the longshore transport zone compares to the beach grain size is required. A review of relevant literature indicates that limited attention has been given to quantifying the grain size in the longshore transport zone. No previous investigations were found that tried to link the longshore transport zone grain size to that found on the beach. A comprehensive analysis of beach and longshore transport zone grain sizes was therefore undertaken and is described in this thesis. Beach grain sizes were compared to those in the longshore transport zone for three different locations around the world: Published grains size information, together with detailed wave and profile data, was obtained from the US Army Field Research Facility at Duck; a second data set was obtained from measurements done at Bogenfels in Namibia; a third dataset was compiled from sampling undertaken by the author in Table Bay, South Africa. A total of 189 samples were collected at four sampling lines in Table Bay between September 2005 and September 2006. Samples were collected across the entire profile from the primary dune to a water depth of 10 m. Samples were collected by grab in the offshore, and by swimming and diving in the surf zone. The location of the four Table Bay sampling lines was chosen so as to obtain data from beaches with different wave and grain size characteristics. Together with the Duck and Bogenfels data, data from six different beaches was therefore available for study. A settling tube was used to determine the grain sizes. Verification of the settling tube analyses against conventional sieving indicated a good comparison. However, the settling tube proved unsuitable for processing of samples with coarse to very coarse material, for which sieving was conducted instead. The grain size at the mid-tide level has been used to characterise the beach. The limits of the longshore transport zone were defined by calculating the cross-shore distribution of longshore transport with the Unibest model. Simpler methods, such as the depth of closure, either overestimated or underestimated it, depending on which wave condition was used in the depth of closure formula. It was found that the beaches with steeper mid-tide beach slopes, such as Bogenfels and northern Table Bay, had coarser median grain sizes than more gently sloping beaches such as found in the south of Table Bay. On energetic beaches, the mid-tide beach grain sizes were significantly coarser than those in the surf zone, by more than twice. At less exposed locations, such as Duck and the central Table Bay beaches, this difference was less. At sheltered locations, such as the southern sampling lines in Table Bay, the mid-tide beach grain sizes are virtually the same as those found in the surf zone. The surf similarity parameter was used to compare the characteristics of the different sites. This parameter was defined using the average wave height seaward of breaking, and the mid-tide beach slope. The ratio between the longshore transport zone grain size and the mid-tide beach grain size was found to be similar to the inverse of the surf similarity parameter for the six beaches that were studied. These findings have led to an improved understanding of the grain size in the longshore transport zone and allow a better characterisation of the representative grain size to use for sediment transport calculations. / AFRIKAANSE OPSOMMING: In kusingenieurswese word langstrandse sedimentvervoer (langsvervoer) gereeld bereken. Belangrike invoer vir sulke berekeninge is die verteenwordigende korrelgrootte van die sand. Die sandkorrelgrootte van die benatte strand is die maklikste om te bepaal, al vind net ‘n klein gedeelte van die langsvervoer op die benatte strand plaas. Die grootste gedeelte van die langsvervoer kom in die brandersone voor, waar dit moeilik is om monsters te neem. Sedimentvervoerberekeninge kan verbeter word as die korrelgrootte ook hierdie sone verteenwoordig. Dit is dus van belang om te verstaan hoe die korrelgrootte van die benatte strand met die gemiddelde korrelgrootte oor die algehele langsvervoersone vergelyk. ‘n Literatuursoektog dui aan dat min aandag al gegee is aan hoe die korrelgrootte op die benatte strand met dié in die langsvervoersone vergelyk. ‘n Ontleding van sandkorrelgroottes op die benatte strand en in die langsvervoersone is dus onderneem en word in die tesis uiteengesit. Strandkorrelgroottes word met dié in die langsvervoersone vergelyk vir drie verskillende gebiede in die wereld : (1) Gepubliseerde data oor korrelgroottes, sowel as strandhellings en golwe, is van die Field Research Facility by Duck in die VSA verkry ; (2) ‘n tweede stel data is van opmetings by Bogenfels in Namibie verkry; (3) die derde stel data is saamgestel deur die skrywer tydens opmetings in Tafelbaai, Suid-Afrika. ‘n Totaal van 189 monsters is tussen September 2005 en September 2006 by vier verskillende opmetingslyne in Tafelbaai geneem. Monsters is geneem van die duin tot in 10 m waterdiepte. In dieper water is grypmonsters geneem, terwyl dié in the brandersone verkry is deur te duik. Die posisie van die vier Tafelbaaise opmetingslyne is gekies om strande met verskillende golftoestande en korrelgroottes te dek. Tesame met die data van Duck en Bogenfels is dus ses datastelle vir ontleding beskikbaar. ‘n Valbuis is gebruik om die korrelgroottes te bepaal. Die valbuismetode het goed met gewone sifresultate vergelyk, behalwe vir monsters met baie growwe korrels. Hiervoor is sifwerk gebruik. Die korrelgrootte van die benatte strand is gebruik om die strand te karakteriseer. Die grense van die langsvervoersone is bepaal deur die dwarsstrandse verdeling van die langsvervoer met die Unibest-model te bereken. Eenvoudiger metodes, soos die berekening van die sluitingsdiepte, het minder betroubare resultate gelewer. Daar is gevind dat steiler benatte strande, soos Bogenfels en Noord-Tafelbaai se strande, groter gemiddelde korrelgroottes as platter benatte strande, soos dié in suidelike Tafelbaai, het. Op blootgestelde strande is die benatte strand se korrelgrootte tot meer as twee keer groter as dié in die brandersone. By gedeeltelik beskutte strande, soos Duck en Sentraal- Tafelbaai se strande, was die verskil minder. Op beskutte strande, soos die Suid-Tafelbaai se strande, is gevind dat die benatte strand se korrelgrootte amper dieselfde as dié in die brandersone is. Die brandergelyksoortigheidsfaktor is gebruik om die verskillende strande te vergelyk. Die golfhoogtes net buite die branderlyn en die benatte strandhelling is gebruik om die veranderlike te bereken. Daar is gevind dat by die ses strande wat ondersoek is, die verhouding van die korrelgrootte in die langsvervoersone en dié van die benatte strand ongeveer gelyk aan die omgekeerde brandergelyksoortigheidsfaktor is. Die bevindings het tot ‘n beter begrip van die wisseling van die korrelgroottes in die langsvervoersone gelei. Gevolglik kan ‘n akkurater verteenwoordigende sandkorrelgrootte bepaal word.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2005. / There has always been some debate in the past about the most effective and economical type of revetment to be used to combat or prevent erosion in rivers and channels. Some of the most common materials used for these mitigation measures are gabions, Reno mattresses and rip rap. A study done by the Colorado State University (CSU, 1984), comprised hydraulic tests of Reno mattresses used as a channel bed revetment. The result were compared with those of rip rap. This thesis mainly deals with the evaluation of incipient motion conditions for rock used in Reno mattresses and as rip rap. In this thesis the results of the CSU study and the design criteria of Maccaferri are evaluated and compared with the result obtained when applying the stream power theory and the Shields' theory with respect to incipient motion. This thesis includes the theory with respsect to incipient motion conditions, background to the CSU study and comparisons of the results of the CSU study and Maccaferri's design criteria with theoretical calculations. A cost comparison of Reno mattresses and rip rap as channel bed revetment measures, as well as conclusions and recommendations with regard to the design and use of these options, are also included. The frame of reference for this thesis is the set of CSU test results. The calibrations achieved, proposals made and accuracy of conclusions thus depend on those results.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / Introduction South Africa is currently experiencing a significant increase in infrastructure investment. Forecasts by BMI-BRSCU have shown that the building and construction industry is expected to grow considerably to 2010, before languishing slightly to 2015. This growth will be driven in particular by investment in non-residential building (41% growth) and construction (73% growth) activities. Even beyond 2015 however, the demand will still be high on the construction industry to provide infrastructure for South Africa’s growing population. South Africa is also facing a serious shortage of engineers, technicians and other skilled workers in the construction industry. This places high demands on designers and contractors to provide services and to realise projects in ever-reducing time periods and at less cost. These conditions have made it increasingly difficult to maintain the required quality of construction in an industry where mistakes can lead to disastrous consequences. Recent advances in structural materials, structural systems and the way in which projects are handled, now enables a new look at the possibilities of combining pre-fabrication with on site work. This method, known as Hybrid Concrete Construction (HCC), has the potential to revolutionize the South African construction industry if applied correctly. Local research into this technique is however required and it is the aim of this thesis to draw attention to this subject. Key Findings Hybrid Concrete Construction (HCC) can be applied to any structural project, it will however not necessarily be successful. A structure needs to be adapted from the very start to suit a particular construction method. This ensures that all the advantages of the selected construction method may be achieved. Adapting a structure to a different construction method requires a mutual understanding and commitment from all project participants, including the architect, engineer, contractor and client. HCC also requires a certain degree of repetition in a project to be financially viable. A theoretical cost exercise was performed where only the material and erection costs were considered. In this exercise, HCC was found to be slightly less expensive than other construction methods for the Office Building of more than 10 storeys. HCC was also found to be significantly faster than other construction methods for the Office Building of more than 3 storeys. The time calculation was however based on the simplified time estimates from one source. Because of HCC’s shorter estimated construction period, the client can expect to earn revenue from a much earlier date. This decreases the relative cost of a HCC project. This advantage, however, needs to be quantified for chosen South African projects. On-site safety is still an important issue with HCC projects. Labourers are not accustomed to this construction method and it may be necessary to alter current skill development programs to include a crane safety course. The training of qualified riggers and crane operators should receive priority if HCC is to develop in South Africa. This preliminary investigation has shown that Hybrid Concrete Construction (HCC) can be feasible for the South African market. Further investigation is however required to determine the parameters for which HCC would be the preferred construction method. Recommendations Based on the findings and conclusions of this investigation, the following recommendations are made. The following actions should be undertaken by individual South African companies: · Develop relationships with external project partners · Train competent riggers and crane operators The South African concrete industry should invest in the following actions: · Invest in mass-producing precast concrete facilities · Develop a central database of South African projects with information on time, costs, project concepts and layouts to be used as a guideline for decision making · Develop local guidelines for the production and application of self compacting concrete · Compile guidelines for the design and construction of HCC and precast concrete construction in South Africa · Develop a local hidden corbel type connection to its full potential

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This investigation focused on the marine components of large direct seawater intake and brine discharge systems for seawater desalination plants, with the main aim to provide an overall design approach for these components. Due to its complexity, an overall and systematic design approach, addressing all the components (feedwater requirements, plant technology, marine structures and environmental issues) is required to ensure an optimum design. A literature review was done on the various desalination technologies, the main components of a seawater desalination plant, as well as the physical, hydraulic, operational and environmental issues regarding seawater extraction facilities, marine pipelines and discharge structures (diffuser). In order to obtain practical input to the development of an overall design approach, information regarding the marine structures of ten of the largest existing seawater desalination plants throughout the world were obtained and compared with each other and the available technologies. By way of example, the recently designed marine components of a new seawater reverse osmosis desalination plant in Namibia were reviewed and, as part of this thesis, alternative conceptual concepts which will include two additional components (sump and brine reservoir) were designed. The alternative design was compared with the actual design in order to determine the feasibility of the alternative in terms of operation and cost and subsequently provide input to the overall design recommendations. Furthermore, from the literature review it seems that there are still significant uncertainties regarding the required performance of a brine (dense) outfall and this required more attention in terms of environmental and hydraulic performance. Based on the Namibian plant, the diffuser configuration was analysed in terms of its hydraulic and environmental performance and subsequently some general guidance with specific respect to a brine diffuser was developed, which in turn formed part of the overall design approach for the marine components. Finally, the design approach for seawater intake structures, brine outfalls and the connecting marine pipelines is provided in the form of flow diagrams. / AFRIKAANSE OPSOMMING: Hierdie ondersoek handel oor die mariene komponente van groot en direkte toevoer van seewater en die sout-uitvloeisisteme van ontsoutingsaanlegte van seewater. Die doel is om ‘n oorsigtelike ontwerpbenadering vir hierdie component te verskaf. As gevolg van die kompleksiteit, is ‘n oorsigtelike en sistimatiese benadering, wat al die komponente (vereistes vir toevoerwater, tehnologie by die aanleg, mariene omstandighede en omgewingsfaktore) in ag neem noodsaaklik om die beste ontwerp te verseker. ‘n Literêre oorsig is gedoen ten opsigte van die tegnologie van verskeie ontsoutingsmetodes, die hoofkomponente van ‘n seewater-ontsoutingsaanleg, asook die fisiese, hidrouliese, operasionele en omgewingskwessies rakende die fasiliteite om die seewater te onttrek, die mariene pyplyne en die strukture vir die afvloei. Ten einde die optimum ontwerp te ontwikkel, is inligting oor die tegnologie en strukture van tien van die grootste bestaande onsoutingsaanlegte in die wêreld bekom, bestudeer en vergelyk Hulle is met mekaar vergelyk, asook met beskikbare tegnologie. As ‘n voorbeeld is die nuut ontwerpte mariene komponente van die nuwe ontsoutingsaanleg in Namibië, waar ontsouting d.m.v. omgekeerde osmose gedoen word ondersoek en as deel van hierdie tesis, is ‘n alternatiewe konsep, wat twee bykomende komponente – ‘n opvangput en reservoir vir die afloop – ontwerp. Hierdie alternatiewe ontwerp is met die werklike aanleg vergelyk om die uitvoerbaarheid van die onderneming en die koste daaraan verbonde te toets. Dit is gebruik as aanbeveling vir die oorhoofse ontwerp. Uit die literêre oorsig blyk dit dar daar nog groot onsekerheid is oor die vereistes van die (digte) waterafloop en dat meer aandag aan die omgewings- en hidrouliese aspekte gegee moet word. Met die Namibiese aanleg as voorbeeld, is die struktuur van die spreiers t.o.v. hidrouliese werkverrigting en die omgewing ontleed. Voortspruitend daaruit is algemene riglyne vir ‘n spesifieke spreier vir afloopwater ontwikkel, wat op sy beurt weer deel vorm van die oorhoofse ontwerp vir mariene komponente. Laastens is die ontwerp vir die strukture vir seewater-invloei, die afloopwater en die mariene verbindingspyplyne as vloeidigramme aangetoon.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The research conducted in this study forms part of the Phase II process of the Bitumen Stabilized Materials (BSMs) Guideline improvement initiative. The initiative aims to address areas of concern in the cold mix design procedures for BSMs. Current road rehabilitation using the bitumen stabilization process requires testing of representative specimens as means to evaluate pavement performance over time. In order to adequately acquire specimens representative of field conditions, it is necessary to condition the materials in a process called curing. Although curing procedures have been standard in many countries on different continents, the protocols are varied and an acceptable procedure is currently not available. In order to develop an acceptable curing protocol for BSMs, both field and laboratory environments were investigated. Considering that curing takes time in the field, production of representative samples intended for laboratory testing must undergo accelerated curing in the laboratory. Given the complexities involved in achieving close correlations between field and laboratory environments, the research strived to reconcile field and laboratory material behaviour. In particular, the main objective of the research was to unify the curing protocol for BSMs, with the standardization of the curing protocol being top priority. In this study, laboratory results have confirmed that the different natures of curing mechanisms inherent in a BSM-foam and BSM-emulsion contribute to irreconcilable material behaviour(s). Results have confirmed that curing of BSM-foam is largely a function of water repulsion, with the addition of active filler dominating material performance almost immediately. Unlike BSM-foam, curing of BSM-emulsion is both a function of the breaking of emulsion during the initial phase and the gradual release of moisture with time. In this instance, BSM-emulsion material performance resembled active filler influences past the breaking of the emulsion cycle. Consequently, given the observed differences regarding material behaviour(s), the unification of the curing protocol for BSMs has not been successful. In terms of accommodation of active filler in the final curing protocol for BSMs, findings in this research have revealed that active filler’s tendency to absorb moisture in the initial stages requires longer curing time to help extract the absorbed moisture during the curing process. Although the use of active filler has an impact on curing, its inclusion in a BSM does not justify its extension in the curing time as cementation is not one of the desired properties of these materials. BSMs are primarily desirable for their flexibility in pavement structures. For this reason, active filler was omitted in the final curing protocol due to reasons of simplifying the mix design process. In conclusion, different curing protocols were tested and developed to help produce reconcilable material behaviour in both the field and laboratory environments. Through the reconciliation of key material properties such as the resilient modulus, long term equilibrium moisture conditions and shear parameters, an acceptable standardized curing protocol for BSM-foam and BSMemulsion intended for application in industrial laboratories across South Africa was successfully developed. / AFRIKAANSE OPSOMMING: Die navorsing tydens hierdie studie gedoen, vorm deel van die Tweede fase van die Bitumen Gestabiliseerde Materiale Riglyne verbeteringsinisiatief. Die inisiatief het ten doel om areas van bekommernis in die kouemengsel-ontwerp-prosedures vir Bitumen Gestabiliseerde Materiale aan te spreek. Huidige padrehabilitasie wat gebruik maak van die Bitumen Gestabiliseerde Materiale proses, vereis toetsing van verteenwoordigende monsters om sodoende plaveiselgedrag oor ‘n tydperk te evalueer. Materiale moet deur die verouderingsproses gekondisioneer word, om sodoende monsters te verkry wat akkuraat verteenwoordigend van veldtoestande is. Alhoewel verouderingsprosesse in meeste lande - op verskillende kontinente - gestandariseerd is, is die protokol verskillend en ‘n aanvaarbare prosedure is nie tans beskikbaar nie. Beide veld- en laboratoriumomgewings is ondersoek, om sodoende ‘n aanvaarbare verouderings-protokol vir Bitumen Gestabiliseerde Materiale te ontwikkel. Wanneer in ag geneem word dat veroudering in die veld tydrowend is, moet vervaardiging van verteenwoordigende monsters vir laboratoriumgebruik versnelde veroudering in die laboratoruim ondergaan. Gegee die kompleksiteite betrokke om goeie korrelasie tussen velden laboratoriumomgewings te verkry, het die navorsing daarna gestreef om die veld- en laboratoriummateriaalgedrag te verenig. Die hoofdoel van die navorsing was om die verouderingsprotokol vir Bitumen Gestabiliseerde Materiale te verenig met die stardaardisering van die verouderingsprotokol as top prioriteit. In hierdie studie het laboratorium resultate bevestig dat die verskillende aard van voorbereidings- meganismes inherent in BSM-skuim en BSM-emulsie bydra tot onversoenbare materiaalgedrag. Resultate het bevestig dat voorbereiding van BSM-skuim ’n funksie van waterrepulsie het en met die byvoeging van aktiewe vullers dominieer dit die materiaalgedrag byna onmiddelik. Anders as BSM-skuim is die voorbereiding van BSM-emulsie beide ’n funksie vir die breek van emulsie tydens die begin fase en die geleidelike vrystelling van vog oor tyd. In hierdie geval het BSM-emulsie se materiaalgedrag die invloed van aktiewe vuller getoon nadat die emulsie gebreek het. Gevolglik, weens die waargenome verskille rakende materiaalgedrag is die vereniging van die voorbereidings- protokols vir BSMs nie suksesvol nie. In terme van inagneming van aktiewe vullers in die finale voorbereidingsprotokol vir BSM’s, is deur navorsing bevind dat aktiewe vullers neig se neiging om vog te absorbeer in die beginstadia dit benodig dus ‘n langer verouderingstyd vir die ontrekking van die geabsorbeerde vog. Hoewel die gebruik van aktiewe vullers ’n impak het op die voorbereiding, reverdig dit nie die verlenging van die verouderingstyd vir die insluiting daarvan in BSM nie, siende dat sementering nie een van die gewenste eienskappe van hierdie materiaal is nie. BSMs word hoofsaaklik verkies vir sy buigsaamheid in paveiselsturkture. Om die mengselontwerp prosesse te vereenvoudig, was aktiewe vullers dus weggelaat in die finale voorbereidingsprotokol. Ter afsluiting was verskeie voorbereidings protokolle getoets en ontwikkel om te help met die vervaardiging van versoenbare materaalgedrag in beide veld-en-laboratoriumomgewings. Deur die versoening van kern materiaal eienskappe soos die elastisiteitsmodulus, lang termynewewigvog kondisies en skuifparameters, is ’n aanvaarbare gestandariseerde voorbereidingsprotokol vir BSM-skuim en BSM-emulsie bedoel vir aanwending in industriele laboratoriums regoor Suid Afrika suksesvol ontwikkel.