Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: South Africa is a relatively dry country with an annual average rainfall of 464mm compared to a world average of 860mm (WSA, 2009). Water shortages and droughts are fairly common to the western and high lying of regions South Africa. Due to its population growth and the rapid development, like the rest of the world, there has been an increased demand for water. Due to increasing costs of procuring water and its decreasing availability, the option of using seawater as a source for freshwater or directly in industrial processes has become competitive, especially in the arid parts of the world. The design of seawater intakes forms an integral part of providing a secure source of seawater. The objective of this thesis is to aid in the development of guidelines for the design of small scale seawater abstraction systems on rocky coastlines using the Horizontal Well Method. Recommendations for guidelines will be given. / AFRIKAANSE OPSOMMING: Geen opsomming

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: All structures are designed for a particular set of load combinations. For roof structures the critical loading combinations are predominantly wind actions. The accumulative effect of wind actions, by wind entering through dominant openings to exert pressure on the inside of roof structures together with the suction of wind vortices on the outside of the roof, can contribute to extreme load combinations. Frequently recorded failures on roof structures suggest that either the loads are underestimated or the resisting capacity of the roof coverings is overestimated. The focus of this study is directed on the latter, determining the effective resistance of roof coverings in the form of sheeting against a Uniformly Distributed Load (UDL) such as wind actions. To determine the carrying capacity of a roofing structure, the standard approach used involves experimental tests on certain configurations with two or more spans. The structural test set-up is loaded with sandbags until failure is reached. For the design of roofing systems, design tables are used that list the maximum allowable purlin spacing. The purlin spacing is presented in the form of a fixed value in units of length and is shown independent of a UDL that the roof needs to be designed for. The need to a new approach to determining the resistance of roof covering systems was identified. The resistance of roof coverings for the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS) depends on a number of parameters such as the bending resistance, the stiffness of the sheeting in bending and the carrying capacity of the fastening system. To evaluate these structural parameters, experimental tests were performed. A full-scale experimental test setup, capable of simulating a UDL on roof sheeting, was developed. The experimental test set-up consists of four different configurations, each specifically schematized to evaluate a certain structural design parameter. The magnitude of the structural design parameters depends on the applied UDL and the span length, which is the distance between consecutive supports of the sheeting system. Therefore, by using the structural design parameters determined experimentally, a set of design tables could be generated. The design tables produce the maximum allowable span length of a roofing system that uses a desired UDL as a variable. By using the design tables, the purlin spacing for any roof structure can be calculated given its design loading combination. The calculated purlin spacings are now a function of the basic parameters that determine the resistance of the roof sheeting. / AFRIKAANSE OPSOMMING: Geen opsomming

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009.

Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2006. / Some experiments utilizing the shear capacity of Engineered Cement-based Composites (ECC) have suggested that elimination of shear reinforcement is feasible when the concrete matrix is replaced by ECC. However, actual application and more rigorous cost analysis are prevented by the fact that the shear stress and strain properties of ECC have not yet been characterized as accurately as the tensile properties. This study focuses on the investigation of the shear property of ECC. The study starts with a survey and comparison of existing shear tests for composite materials. The Iosipescu shear test concept is chosen as the most objective method for ECC, and subsequently, modified for specific application on ECC by simple analytical design and finite element refinement. The modified Iosipescu shear test method is applied on, four types of ECC specimens with different fibre content (0%, 1%, 2%, 2.5% by volume), which have been cast in specially designed moulds and cured in laboratory conditions. Three phases of shear measurements are used to check the shear test appropriateness and study the shear mechanical properties of ECC. The failure mode is verified in the first phase, detailed measurement of the shear strain and shear stress is performed and recorded in the second phase, and in the third phase more information about the ductility of diagonal cracking is obtained by measurement of the tensile principal deformation. By also conducting direct tensile tests on specimens of the exact same mix, information of both uniaxial tension and shear behaviour is available, from which elastic and shear moduli, as well as Poisson’s ratio of ECC are computed. A first step toward application of this knowledge of the shear behaviour of ECC is taken by studying the response of shear-dominated beams and beam-columns of reinforced concrete and reinforced concrete combined with ECC as the outer crusts. These beams were prepared and tested by other members of the research group of the Division for Structural Engineering of the University of Stellenbosch. It is shown that ECC can indeed successfully replace shear reinforcing steel, due to its shear capacity.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2007. / Mozambique is investing heavily in rehabilitating and upgrading the current roadway infrastructure. Investigation by the Mozambican roads authority found that some consulting engineers and contractors were not familiar with Mozambican conditions and materials. The World Bank sponsored a research project to support the roadway infrastructure preservation and maintenance efforts. The thesis work presented forms an integral part of the work conducted by the World Bank project research team. The objective of the thesis is to characterise cement stabilized sand bases in Mozambique under Accelerated Pavement Testing (APT) in terms of stiffness and deflection responses under load trafficking. This work forms the basis for developing guidelines for a mechanistic-empirical design method for Mozambican conditions and materials. Reported findings from initial MMLS3 testing conducted for the World Bank project were used to scope the full-scale research study and provided guidelines for the selection and construction of full scale test sections on natural subgrade. The APT presented encompass full-scale pavement testing including wet trafficking cycles to emulate environmental effects.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: See item for full text / AFRIKAANSE OPSOMMING: Sien item vir volteks

Thesis (MScEng)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: It is argued that an understanding of variability is central to the modelling of travel behaviour and the assessment of policy impacts and is not the peripheral issue that it has often been considered. There is a growing need to assess multi-day data to assess the distribution of user charges for road pricing, or patterns of public transport usage as well as improve the ability to identify mechanisms behind travel behaviour for modelling purposes. Drawing on studies worldwide, in conjunction with a review of the literature, the thesis first examines the relevance for using multi-day data, then discusses the methodology and results of a five week survey undertaken specifically for this study, makes a comparison of the findings with that observed in other studies, and finally discusses issues relating to the application of the data and future research possibilities. Previous studies have shown that behaviour which makes up the daily travel pattern can be highly repetitious in nature but that observing an individual’s behaviour on a single day might not be representative of their routine travel and that this behaviour varies across demographic segments and driver gender. This paper examines day-to-day travel behaviour variability of a residential area, Summer Greens, located in Cape Town (South Africa) using a travel dataset collected recently in November/December 2006. The survey technique employed was the recording of numberplates of all exiting vehicles from 06:00 to 10:00, weekdays from Monday to Friday over a period of five weeks. A total of 5677 vehicles undergoing 44 743 trips was observed and analysed. This research replicates and extends previous work dealing with day-to-day variability in trip-making behaviour that was conducted with data collected by Del Mistro and Behrens (2006) in Buitengracht Street, Cape Town CBD, in July/August 2005. The present research extends the earlier work by including departure time variations as well as conducting the observations during both a school period (3 weeks) and consecutive holiday period (2 weeks). Further, the thesis presents a method to measure day-to-day variability using the available data surveyed. This thesis finds a considerable difference in school and holiday traffic volumes as expected, but that despite this, certain identical travel behaviour patterns (such as vehicle appearance frequencies, following week repeat proportions etc.) is observed during both these periods. It was found that the peak hour for both school and holiday periods occurred during the same time period and greater traffic volume variability was found to occur on Fridays during the holiday period than in the school period. Traffic volumes across all weeks appeared to decrease from Monday to Wednesday and “bounce back” on Thursday and Friday consistent with the findings of another international study. It was found that motorists exhibited more departure time freedom during the holiday period with average holiday departure times much later than during the school period. Departure times were also observed to gradually become later from Monday to Friday during both the school and holiday periods with Thursday and Friday departure times significantly different to the other weekdays. The proportion of unique vehicles observed was found to increase with time of day and the resulting impact of this on the effectiveness of Variable Message Sign (VMS) applications is also discussed. The research concludes by applying the findings to determine the impact of a hypothetical congestion pricing scheme on traffic volumes. / AFRIKAANSE OPSOMMING: Die argument is dat ‘n begrip vir variasie sentraal staan tot die modellering van reisgedrag en die assessering van beleidsimiplikasies, en is dus nie net n nagedagte soos wat gereeld gedink word nie. Daar is ‘n toenemende behoefte om multi-dag data te analiseer om die verspreiding in gebruikerskostes te bestudeer vir die waardasie van paaie, of om verhoudings in publieke vervoergebruik uit te lig, asook, vir die verbetering van die vermoë om die meganismes agter reisgedrag te identifiseer vir modelleringsdoeleindes. Die tesis bestudeer eerstens die relevansie van die gebruik van multi-dag data in samewerking met die literatuurstudie, gebaseer op studies wêreldwyd onderneem. Tweedens bespreek dit die metodologieë en resultate van ‘n vyf-week lange opname wat spesifiek vir hierdie studie onderneem is en tref vergelykings met die resultate verkry deur vorige studies. Dit bespreek dan die probleme wat voortspruit uit die toepassing van die data en ook toekomstige moontlikhede tot verdere navorsing. Vorige studies het getoon dat die gedrag wat tydens daaglikse reispatrone voorkom van nature hoogs herhaaldelik is. Wanneer ‘n individu se gedrag observeer word op ‘n enkele dag is dit egter nie noodwendig verteenwoordigend van sy/haar roetine reisgedrag nie en dat hierdie gedrag afhanklik is van demografiese faktore en die geslag van die bestuurder. Hierdie tesis bespreek die variasie in dag-tot-dag reisgedrag van ‘n residensiële gebied, Summer Greens, in Kaapstad (RSA) deur gebruik te maak van ‘n datastel wat onlangs saamgestel is (November/Desember 2006). Die data is ingesamel deur ‘n opname te doen van die nommerplate van alle uitgaande voertuie tussen 06:00 en 10:00, weeksdae van Maandag tot Vrydag, oor ‘n periode van vyf weke. A totale aantal voertuie van 5677 wat 44 743 ritte onderneem het, is waargeneem en ‘n analise is uitgevoer. Die navorsing herhaal en brei uit op vorige werk wat die dag-tot-dag variasie in ritopwekking bestudeer. Del Mistro en Behrens (2006) het data bestudeer wat ingesamel is in Julie/Augustus 2005 in Buitengrachtstraat, in die Kaapse Middestad (RSA). Die huidige navorsing brei uit op hierdie werk deur die variasie in vertrektyd in te sluit asook om waarnemings te doen tydens die skoolperiode (3 weke) en die daaropvolgende vakansieperiode (2 weke). ‘n Metode word ook aangebied om die dag-tot-dag variasie te meet deur middel van die beskikbare data wat ingesamel is. Hierdie tesis vind ‘n merkwaardige verskil in die skool en vakansie verkeersvolumes, soos verwag kan word, maar ten spyte daarvan bestaan daar sekere identiese reisgedragspatrone (byvoorbeeld die frekwensies waarteen ‘n voertuig voorkom, weeklikse herhaling van proporsies, ens.) gedurende beide hierdie periodes. Die bevinding is dat die spitsuur vir skool- en vakansieperiodes gedurende dieselfde tydsperiode plaasvind en dat verkeersvolumes groter variasie toon op Vrydae gedurende die vakansieperiode, as die skoolperiode. Dit wil blyk of verkeersvolumes gedurende al die weke afneem van Maandag tot Woensdag en dan “terug spring” op Donderdae en Vrydae. Hierdie bevinding is in ooreenstemming met resultate van ‘n ander internasionale studie. Motoriste het ‘n neiging getoon tot groter vryheid in terme van vertrektye tydens die vakansieperiode, met die gemiddelde vakansie vertrektye heelwat later as gedurende die skoolperiode. Vertrektye is ook gevind om geleidelik later te word van Maandag tot Vrydag gedurende beide die skool en vakansieperiodes, met Donderdag en Vrydag se vertrektye wat merkwaardig verskil van ander weeksdae. Die verhouding uniek waargenome voertuie het volgens hierdie navorsing se bevindinge toegeneem met die tyd van die dag en die gevolglike impak hiervan op die effektiwiteit van sogenaamde “Vehicle Message Sign” toepassings word bespreek. Die navorsing sluit dan af deur die bevindinge toe te pas om die impak te bepaal wat ‘n hipotetiese kongestieprysskema op verkeersvolumes het.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / Multi purpose reefs are a relatively new concept that incorporate functionalities of beach stabilization, breakwater/seawall protection, biological enhancement and recreational amenity. Economic benefits increase their attractiveness. There is, however, some degree of uncertainty in design guidelines as to the predictability of each of these aspects. With regards to recreational amenity enhancement, one such uncertainty exists in the ability to predict the reef configuration required to give a certain degree of surfability of a reef, and more specifically, to predict the shape of a plunging wave. An extensive survey of the relevant literature has been conducted to provide a background on multi purpose reefs and the uncertainties in predicting the success of multi purpose reefs in achieving their design objectives. A study of wave breaking has been done, along with an analysis of existing breaker height and breaker depth formulae. The effects of bottom friction, refraction, shoaling, winds currents and varying water level on wave breaking has been addressed. Surfability aspects were reviewed including a definition of breaking intensity which is defined by the wave profile in terms of vortex shape parameters, and other surfability parameters that influence the surfability of a reef. Background on numerical modelling methods has been given, along with a description and some trial runs of a new and promising method, Smooth Particle Hydrodynamics. Numerical models were run using the open source SPHysics package in order to assess the applicability of the package in measuring vortex shape parameters. The SPHysics package is, however, still in a stage of development, and is not yet suitable for reef studies with very long domains and with high numbers of particles (required for sufficient resolution in the plunging vortex). A theoretical examination was done on the relevant literature in order to gain an insight into the dynamics affecting the development of the plunging vortex shape. A case study of a natural surf reef was carried out in order to give qualitative estimation of the wave dynamics and reef structure required to give good quality surfing waves and high breaking intensity. The West- Cowell surfing reef factor was used as a tool in predicting wave focusing effects of a naturally occurring reef. Extensive two dimensional physical model laboratory studies were conducted in order to quantify the effects of the reef configuration and wave parameters on breaking intensity. Design guidelines were developed in order to assist in the prediction of breaking intensity for reefs constructed with surfing amenity enhancement as one of their design objectives. The results show that large underwater topographic features can significantly affect the shape and size of incoming waves. Refraction, focusing and shoaling can transform ordinary waves into waves deemed suitable for surfing. The West-Cowell surfing reef factor gives reasonable results outside its applicable range. The 2D physical model laboratory tests show significant variations in vortex shape parameters due to interactions between broken and unbroken waves in a wave train and also to the reflections developed in the flume. Results show that the predicted trends agree with the observations. The results also show that the junction between the seaward reef slope and the horizontal crest may have an effect on the wave shape in the form of a secondary crest between the primary crests. Design guidelines based on the results are presented, and show that breaker height formulae for smooth planar slopes show good agreement with the values of breaker heights measured in the physical model tests, and that existing breaker depth formulae show average agreement. The design guidelines could assist with more effective design of artificial reefs for surfing purposes.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / The climate of the world varies from one decade to another, and a changing climate is natural and expected. However there is a well-founded concern that the unprecedented human industrial development activities of the past two centuries (and mainly the last century) have caused changes over and above natural variation. Climate change is the natural cycle through which the earth and its atmosphere are going to accommodate the change in the amount of energy received from the sun. There are various indicators that can be monitored to measure and verify possible climatic changes. This thesis will firstly emphasize what the possible effects of climate change could be on amongst others, the coastal zone, biodiversity and water resources. If the impact of climate change on the above mentioned processes are monitored, and changing trends can be identified, these processes could in fact be seen as climate change indicators. This is of major importance to us, to be able to accurately identify whether climatic changes are experienced in any given area and to attempt to quantify it. Engineering hydrologists are, amongst other duties, responsible for the determination of peak discharges to be able to size conduits to safely convey the stormwater for given recurrence interval events. All hydrological predictions are indirectly or directly based on historical data. Empirical formulas and deterministic methods were developed and calibrated from known historical data. Statistical predictions are directly based on actual data. The question that arises is whether the historical data still provides an accurate basis from which possible future events can be predicted? This thesis strives to find an answer to this question and will also try to advise hydrologists on how they should interpret historical data in the future, taking climate change into consideration. The methodology that will be followed will be to compare the percentage of occurrence of 24-hour rainfall events of different magnitudes, for historical- as well as predicted rainfall, for five different rainfall stations in the Western Cape. A detailed analysis of measured data at a rainfall station, with 42 years of useable data, will also be performed, to verify whether any measurable trends have already been experienced. Conclusions shall be drawn as to possible trends, and recommendations will be made as to how hydrologists could allow for the possible changing rainfall patterns.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008.