Masters Degrees (Civil Engineering)

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2D Modelling of turbulant transport of cohesive sediments in shallow reservoirs
(Stellenbosch : University of Stellenbosch, 2006-12) De Villiers, J. W. L.; Basson, G. R.; University of Stellenbosch. Faculty of Engineering. Dept. of Civil Engineering.
Modelling of the transport of fine cohesive sediments, as found in most South African reservoirs, has not been well developed. This is because the transport processes that are involved are complex and the theories not as implicit as the traditional equilibrium transport theories for coarse non-cohesive sediment. Advection and dispersion are found to be the processes that best describe the transport of fine sediments in turbulent flow conditions. A two-dimensional modelling tool, MIKE 21C, which simulates reservoir hydrodynamics and cohesive sediment transport processes with an advection-dispersion model, was evaluated in this thesis. The creation of such a numerical model involves the setting up of a suitable curvilinear grid and requires data on the bathymetry, recorded inflows as well as water levels. It also requires sediment characteristic parameters and transport parameters. These parameters have to be specified by the user based on previous studies and field measurement data. MIKE 21C was applied to laboratory flume tests and reservoir case studies in the field in order to determine the effects that these parameters have on the sediment transport in a series of sensitivity studies. Ranges were determined within which these parameter values should fall. A procedure was also developed through which reservoir sedimentation models can be calibrated.
3D concrete printing technology: enhancing productivity in the South African construction industry – exploring the benefits, barriers, and improvement strategies
(Stellenbosch : Stellenbosch University, 2023-11) Mogale, Setekoane Phillemon ; Van Zijl, Gideon P. A. G.; Van Rooyen, Algurnon Steve Tata ; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Provided its multitude of benefits, 3D Concrete Printing (3DCP) technology has the potential to transform the South African construction industry, with specific reference to the building sector, by revolutionizing the current traditional construction techniques. However, to fully realize the full potential of this innovative technology, it is of utmost importance to have a comprehensive awareness of its benefits, an understanding of the potential barriers associated with its adoption, and strategic measures tailored to smoothly integrate it into the construction industry. Therefore, this research study aims to comprehensively explore the benefits, barriers, and strategic measures associated with the adoption and implementation of 3DCP technology within the South African construction industry. The research process began by conducting a comprehensive literature study, which delved deep into assessing the current state of 3DCP technology and its application in the construction industry. To fully comprehend the complex dynamics of this technology, a strong foundation was established through the literature study by synthesizing and consolidating information and conceptual frameworks. This assessment process provided insights into the unique potential opportunities and challenges that could be faced by the South African construction industry as it navigates its way into adopting and implementing 3DCP technology as one of the mainstream construction techniques. In addition to this, a survey questionnaire was distributed to various professionals working in the South African construction industry to collect detailed primary data. The survey questionnaire was well designed to probe their perceptions regarding this technology within the South African construction industry given its unique context. The collected data was subjected to a thorough and systematic analysis by applying both descriptive and inferential statistical techniques to determine how the industry perceives the benefits, barriers, and improvement strategies associated with the adoption of 3DCP technology. This systematic analysis yielded a wealth of information that highlighted common trends and main themes that shape the landscape of 3DCP technology adoption within the South African construction industry. The findings of this research highlighted that the South African construction industry is fraught with substantial barriers despite being ripe and well-positioned to embrace the transformative potential of 3DCP technology. The high initial investment was consistently highlighted as the most prevalent barrier, followed by the absence of 3DCP technology experts and the lack of government incentives and support. However, the strategic measures formulated to mitigate these barriers were highly appraised by the professionals, further highlighting the readiness of the industry to leverage this innovative construction technology. Ultimately, these research findings have implications that go beyond mere academic research as they are of significant value for stakeholders with a vested interest in the adoption and successful implementation of 3DCP technology in the South African construction industry. The research study promotes the application of sustainable and efficient innovative construction techniques, tailored to enhance productivity, and encourage environmentally friendly practices, thereby guiding the industry towards a future driven by innovation, competitiveness, and steady growth.
3D printing of eco-friendly concrete incorporating recycled plastic waste (RESIN8) as fine aggregate
(Stellenbosch : Stellenbosch University, 2022-12) Oosthuizen, Jandré Daniel; Babafemi, Adewumi John; Walls, Richard Shaun; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH BSTRACTS: Plastic waste is a massive environmental issue worldwide which cannot be solved in a simple manner. Sand being a natural resource is limited in nature in contrast to the abundance of waste plastics in our environment. This study, therefore, investigates the suitability of creating an eco-friendly 3D printable concrete where recycled plastic waste, in the form of Resin8, is incorporated by replacing different percentages of fine aggregates. Replacement values of 5%, 10% and 15% of natural sand by volume are investigated, which are further characterized by varying Resin8 particle sizes. Particle sizes of Resin8 included are sub-5 mm, sub-1 mm and a combination of the two by mixing them by equal proportions (50/50). The concrete incorporating recycled plastic waste (Resin8) was compared to, and tested against a reference concrete mix which is the standard 3DPC mix at Stellenbosch University. Samples of each concrete mix were also mould cast into 160 x 40 x 40 mm prisms from the same concrete mix that were used for printing to investigate the effect the printing process had on the mechanical properties of the concrete. The rheology, slump flow (workability), buildability, air content and density are some of the fresh properties that were investigated. The mechanical properties of the different concrete mixes were investigated by means of flexural (4-point bending) and compression tests. Due to the anisotropic nature of 3DPC, the printed samples were tested in two different directions; D1 and D3. Porosity analysis by means of Computed Tomography (CT) scans were done on printed and cast samples of the reference mix as well as all sub-1 mm Resin8 printed samples to compare and investigate the effect of Resin8 on the microstructure of the printed concrete. Scanning Electron Microscopy (SEM) analysis was conducted on sub-5 mm and sub-1 mm Resin8 particles used in this study, as well as on the 3D printed samples of the reference mix and all replacement percentages of the combination Resin8 mixes after 28 days. All mixes containing Resin8 performed adequately for use in 3DPC based on characterisation of its fresh properties. It was observed that mixes containing Resin8 were more flowable, which has been validated by an increase in slump flow value when compared to the reference mix, while the buildability was negatively affected by the increased flowability. A lower density was obtained as the percentage of Resin8 replacement increased as expected due to the lower relative density of Resin8 compared to sand. Both the flexural and compressive strength decreased as the Resin8 replacement increased. However, an increase in interlayer bond strength was observed in all Resin8 mixes compared to the reference mix, which could possibly be as a result of excess pore water at the interlayer region due to the hydrophobic nature of plastics. The printing process had little effect on the performance of the 3DPC mixes based on similar flexural and compressive strength results achieved for orientation D3 and the mould cast samples, while orientation D1 yielded the best results. Considering the results obtained in this research, the addition of Resin8 into 3D printable concrete is a feasible option and could potentially lead to great reductions of waste plastics in our natural environment even for low replacement volumes.
3D Printing of rapid setting ordinary concrete mixtures
(Stellenbosch : Stellenbosch University, 2021-12) Gunzel, Friedhelm Stefan; Combrinck, Riaan; Kruger, Pienaar Jacques; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: In recent years, significant research and development has gone into 3D printed concrete. This construction technique requires no formwork as in ordinary construction projects. The addition of admixtures increases the complexity of 3D printable mixtures in comparison to ordinary concrete mixtures in which cement, water and aggregate are the main constituents. In this study, more ordinary concrete mixtures are used for 3D printing in order to minimise the complexity of 3D printable mixtures. The combination of a more ordinary concrete mixture with the efficiency of 3D printing as a construction technique, combines the benefits of both construction techniques. The aim was to 3D print ordinary concrete mixtures that have improved buildability characteristics due to a rapid setting behaviour. Three types of rapid setting behaviours were tested in this study: false setting, ordinary Portland cement (OPC) cement replacement with belitic calcium sulfoaluminate (BCSA) cement and flash setting. The study was conducted in two phases. The first phase was used to characterise the three rapid setting mixtures. Compressive strength, hydration temperature development, setting time and early age compressive strength were tested for the characterisation. In the second phase, the three rapid setting mechanisms were printed in a 3D printer to determine the buildability of the three rapid setting mechanisms. In addition to buildability, the economic feasibility of the rapid setting mixtures was analysed. It was found that false setting does not significantly influence the mechanical characteristics of concrete. The early age strength gain is not as rapid as for flash setting or with the addition of BCSA cement. Flash setting improves the early ages strength gain of concrete but reduces the long-term compressive strength development. Replacing OPC cement with BCSA cement improves the early age strength gain and does not impact the mechanical properties significantly. Higher cement replacement rates increased the intensity of the rapid setting mechanisms, shorter setting times and higher early age strength was improved. From the buildability study it was found that flash setting has the largest positive impact on the buildability characteristics of 3D printed concrete. The buildability could be increased by 321% with flash setting. OPC cement replacement with BCSA cement resulted in a buildability increase of 214%. False setting was found to be the least effective rapid setting mechanism with a 35% increase in buildability. Flash setting and BCSA replacement are cost effective methods to improve the buildability of 3D printed concrete. False setting is found too expensive to induce and the compressive strength gain at early ages is little compared to the other two rapid setting mechanisms. The aim of this study was achieved by 3D printing rapid setting ordinary concrete mixtures. Significant buildability improvements could be made, and the rapid setting ordinary concrete mixtures are beneficial for the rapid construction of 3D printed components or structures.
Accelerated testing of an asphalt pavement with the third-scale model mobile load simulator (MMLS3)
(Stellenbosch : Stellenbosch University, 2000-12) Walubita, Lubinda F.; Van de Ven, M. F. C.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Accelerated pavement testing (APT) is the application of a wheel loading, to a prototype or actual layered, structural pavement system to determine pavement response and performance under controlled, accelerated accumulation of damage in a compressed time period. It is a tool used for the evaluation of performance of new pavement materials, distress mechanisms, pavement distress, and selection of rehabilitation strategies. In this study, the research work that was done in Jacksboro, Texas (USA) with the third-scale Model Mobile Load Simulator (MMLS3) as part of the APT programme of the Texas Department of Transportation (TxDOT) is presented. The primary objective was to evaluate the performance ofthe different asphalt concrete (AC) materials (Dustrol and Remixer) used on highway US 281, in terms of rutting and distress due to wet trafficking. The other objective was to investigate the difference in rutting between the MMLS3 and the full-scale Texas Mobile Load Simulator (TxMLS). The scope of the study included fieldwork, laboratory work and theoretical analysis. On average, the performance of the layer from the Dustrol process was found to be poorer than that of the Remixer process. The Dustrol process was more susceptible to moisture damage and less resistant to permanent deformation compared to the Remixer process. The MMLS3 and TxMLS permanent deformations in the upper 90 mm surface layers correlated well in terms of the respective vertical stresses imposed by the two APT devices, after allowing for the difference in environmental conditions during trafficking. Overall, the study demonstrated that the MMLS3, used in conjunction with nondestructive field and laboratory testing, is a significant cost-effective APT device that can be used for evaluating the response and performance of the (surface) layers of full-scale, in-service pavements.
Accessibility index to public facilities for prioritisation of community access road development
(Stellenbosch : Stellenbosch University, 2017-03) Nemvumoni, Fhatuwani Lesley; Jenkins, Kim Jonathan; Rudman, Chantal; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: A number of studies have acknowledged the positive impacts that rural roads have on the social and economic development of a region. This impact is due to the increased accessibility offered by road development. The effect of the social impact, however, has proven to be difficult to quantify, with many studies opting to use ratings to define this impact. The need to quantify the social impact arises from the need to aid decision-making processes, which seek to identify or prioritise the most cost effective projects. This is more often the case in rural communities where a typical economic prioritisation method, such as a cost-benefit analysis, will likely yield unfavourable results because of the low traffic volumes present on these roads. The method proposed for prioritisation in this research introduces an accessibility index that takes into account the accessibility provided by the road infrastructure, and by transportation modes, and by public facilities such as public schools and clinics. The data required to formulate and validate the model was collected in three villages located in the Limpopo Province of South Africa. The accessibility provided by the road infrastructure is quantified as the percentage of the length of the road link that conforms to road classification standards. The standards relate to travel speed for motorised transport and cross sectional dimensions for non-motorised transport. The probabilities of a preference to use a facility or transport mode are used as accessibility indices for the facilities and the transport modes. The probabilities are a result of stated preference experiments, which take into account the different quality attributes of public facilities, and characteristics of the transport mode. The final weighted accessibility index is obtained by considering the number of users in each observed facility in South Africa and the budget allocated to it. This enables the accessibility index to be converted further into a monetary value that is compared with the cost of successfully completing the project and the figures that arise from alternative projects. The facilities investigated were selected with the guidance of the National Development Plan (NDP) and included public schools and public healthcare facilities. The exercise resulted in accessibility indices that were used successfully to rank seven hypothetical projects from two of the identified villages. The research showed that, for low-volume roads, non-motorised transport modes are just as important as motorised transport modes. Other key findings were made which illustrated significant variables that influence preference for transport modes, school attendance and clinic visitation.
Adaptive conversational systems harnessing human expertise in modern chatbots
(Stellenbosch : Stellenbosch University, 2024-03) Van Eeden, Christiaan; Du Preez, Johan; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
ENGLISH ABSTRACT: Chatbots are a rapidly evolving technology integral to the automation of customer service. Traditionally designed around complex if-then-else statements, the technology has seen a paradigm shift towards deep learning techniques for improved flexibility and user interaction. This research proposes a novel approach for training chatbots to learn more effectively from human support agents within automated customer service. Capitalising on the extensive data generated by these agents, we develop a framework to train chatbot models to emulate human-like responses, encapsulating nuances of unique language and individual mannerisms. Using state-of-the-art machine learning and natural language processing techniques, we train these models, achieving more contextually appropriate and authentic responses that accommodate the subtle complexities of human interaction. While commercial large language models (LLMs) like ChatGPT have demonstrated proficiency in customer service automation, they present limitations that could hinder their practical use. Such models, being proprietary, are not available for modification, impeding a company’s capacity to customise them to their specific needs. The costs, both financial and technical, associated with training a bespoke LLM can also be prohibitive for many organisations. Furthermore, these models, with their billions of parameters, require substantial hardware resources and may struggle to manage high-volume, swift interactions typical in a customer service environment. Additionally, due to their general-purpose nature, these models can occasionally produce unpredictable or undesirable responses as they lack specific domain knowledge. Our proposed model, developed on the more manageable GPT-2, offers a tailored, cost-effective, and adaptive solution to these challenges. Although our research is limited in its scope, the findings indicate an improvement in the usability and effectiveness of chatbots trained with our proposed method. This study contributes to the broader field of AI-driven customer service by augmenting the development of more sophisticated and user-friendly chatbot systems.
Advanced characterisation of hot mix asphalt with recycled crushed glass
(Stellenbosch : Stellenbosch University, 2018-12) George, Theresa Bernadette; Jenkins, K. J.; Anochie-Boateng, J. K.; Van de Ven, M. F. C.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Over the last few decades, the use of glass in pavement applications has been implemented by various countries in the international community. South Africa, however, on average generates roughly 900 000 tonnes of domestic waste glass each year and has made little use of this readily available raw material. More recently, with national policies mandating the reuse, recycling and minimisation of domestic waste, in addition with several economic and environmental benefits, it is expected that the use of alternative materials, e.g. recycled glass, in road construction will increase. Depending on the application, the uses of recycled glass in road construction vary widely. This study investigates the engineering performance of Hot Mix Asphalt (HMA) incorporating locally available recycled crushed glass for use in the wearing course of South African pavements. The study contributes to current research at the Council for Scientific and Industrial Research (CSIR) which aims to optimise the design, construction and maintenance of roads through the use of cost-effective and sustainable materials that include waste materials. A continuously-graded asphalt mix with a glass replacement ratio of 15% and 50/70 penetration grade bitumen was designed for a traffic level of 3 to 30 million E80s. The mix design was conducted according to the current method for traditional asphalt mixes in South Africa. The results indicate that the glass-asphalt mix conforms to the South African mix design criteria. Furthermore, the moisture susceptibility of the glass-asphalt mix was evaluated with and without the use of anti-stripping additives. The standard Tensile Strength Ratio parameter supported with a microscopic imaging technique and an analytical modelling method were used to evaluate and quantify the resistance of the glass-asphalt mix to moisture damage. Analysis of the results reveal that an antistripping additive is essential to meet moisture susceptibility criteria and alleviate stripping for the investigated source and grading of glass particles, at a glass content of 15%. The study also assesses and compares the stiffness and permanent deformation properties of the glass-asphalt mix to a traditional continuously-graded asphalt wearing course mix, typically used for road construction in South Africa. Selected mathematical models were used to effectively characterise the deformation and stiffness behaviour of the mixes. The glass-asphalt mix shows increased stiffness and improved resistance to permanent deformation at elevated temperatures. Additionally, a multi-layer linear-elastic analysis is used to assess the influence of temperature and loading frequency variation on the structural capacity of the glass-asphalt and HMA surfacing layers. The analysis reveals that the structural capacity of both surfacing layers are comparable at intermediate temperatures, for both high and low loading frequencies. The findings of this study reveal that improved performance could potentially be achieved with the use of recycled crushed glass in continuously-graded asphalt wearing course mixes in South Africa.
Aeration of Roberts Splitters through an Internal Gallery of a Dam
(Stellenbosch : Stellenbosch University, 2016-12) Calitz, Gerard; Basson, G. R.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Roberts splitters have effectively been used for more than 75 years to dissipate the flood discharge energy of more than 30 dam spillways in South Africa and abroad. Roberts’ (1943) standard, unaerated splitter design procedure is, however, limited to a spillway head (𝐻) of 3.0 m, equivalent to a unit discharge (𝑞) of 12 m2/s. In order to avoid cavitation at higher design spillway heads, the flow is aerated by local air vents positioned on the splitters. On current dams, these air vents are individually fed by intake pipes placed in the step directly below the splitters. However, problems emerge when these pipes need to drain water entering the air vents. To avoid drowning the intake pipes, aeration through an internal gallery that is open to the atmosphere is proposed, with the end goal of increasing the unit discharge limit of Roberts splitters. A 1:20 scale hydraulic model of an ogee spillway equipped with Roberts splitters was constructed. Two aerated models, with different sized air vents, were compared to an unaerated control model in order to determine the effect that the proposed aeration system has on the cavitation risk of the splitters at prototype unit discharges (𝑞) of up to 50 m2/s. At the maximum tested spillway head of 7.6 m (𝑞 = 50 m2/s), the minimum pressures and air concentration around the splitters of both aerated models increased considerably. This indicated that the proposed aeration system completely alleviates the high cavitation risk of unaerated splitters. It was further observed that the unaerated splitters were prone to drowning at high spillway heads, leading to unfavourable hydraulic conditions that should be avoided at all cost. To summarise, the addition of aeration through an internal aeration gallery can increase the unit discharge capacity of Roberts splitters to at least 50 m2/s (up by 43%, from the unaerated limit of 35 m2/s, as tested during this study) while the proposed aeration gallery provides a solution to the problem of draining the inflow water of the air vents, without jeopardising the effective aeration of the splitters.
Age-related performance of typical seal binders in South Africa
(Stellenbosch : Stellenbosch University, 2018-03) Engelbrecht, Francois; Jenkins, Kim; Bredenhann, Steph; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: The age-related performance of typical seal binders in South Africa was studied to understand the behaviour of the binders as it ages. The three main failure mechanisms for surfacing seals include surface cracking, ravelling and texture loss. These mechanisms shorten the life of the pavement exponentially. Various factors may be the cause of these failures. This study includes the analyses of the rate at which oxidation influences the performance of surfacing seals. Rheology was used to analyse the age-related performance of the selected seal binders. Low and high temperature testing was conducted in the laboratory at various ages such as RTFO and PAV (20hr, 40hr and 80hr) which includes short-term ageing and long-term ageing of a binder. Several ageing parameters were used to analyse the results of each seal binder. The South African Performance Grade Specification and the AASHTO M320 specification are established to set the required performance of asphalt binders. These specifications were used to compare the performance of surfacing seal binders to asphalt binders. Results showed that ageing influences the modification within surfacing seal binders. It appears that the performance of the elastic component in the modifier decreases as the binders age. The low temperature results show that the difference between the unmodified and modified binders are minimal. The high temperature results indicate that the highly modified binders perform well considering the influence of ageing.
Algorithmic component and system reliability analysis of truss structures
(Stellenbosch : Stellenbosch University, 2013-12) Hashemolhosseini, Sepehr; Van der Klashorst, Etienne; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Most of the parameters involved in the design and analysis of structures are of stochastic nature. This is, therefore, of paramount importance to be able to perform a fully stochastic analysis of structures both in component and system level to take into account the uncertainties involved in structural analysis and design. To the contrary, in practice, the (computerised) analysis of structures is based on a deterministic analysis which fails to address the randomness of design and analysis parameters. This means that an investigation on the algorithmic methodologies for a component and system reliability analysis can help pave the way towards the implementation of fully stochastic analysis of structures in a computer environment. This study is focused on algorithm development for component and system reliability analysis based on the various proposed methodologies. Truss structures were selected for this purpose due to their simplicity as well as their wide use in the industry. Nevertheless, the algorithms developed in this study can be used for other types of structures such as moment-resisting frames with some simple modi cations. For a component level reliability analysis of structures different methods such as First Order Reliability Methods (FORM) and simulation methods are proposed. However, implementation of these methods for the statistically indeterminate structures is complex due to the implicit relation between the response of the structural system and the load effect. As a result, the algorithm developed for the purpose of component reliability analysis should be based on the concepts of Stochastic Finite Element Methods (SFEM) where a proper link between the finite element analysis of the structure and the reliability analysis methodology is ensured. In this study various algorithms are developed based on the FORM method, Monte Carlo simulation, and the Response Surface Method (RSM). Using the FORM method, two methodologies are considered: one is based on the development of a finite element code where required alterations are made to the FEM code and the other is based on the usage of a commercial FEM package. Different simulation methods are also implemented: Direct Monte Carlo Simulation (DMCS), Latin Hypercube Sampling Monte Carlo (LHCSMC), and Updated Latin Hypercube Sampling Monte Carlo (ULHCSMC). Moreover, RSM is used together with simulation methods. Throughout the thesis, the effciency of these methods was investigated. A Fully Stochastic Finite Element Method (FSFEM) with alterations to the finite element code seems the fastest approach since the linking between the FEM package and reliability analysis is avoided. Simulation methods can also be effectively used for the reliability evaluation where ULHCSMC seemed to be the most efficient method followed by LHCSMC and DMCS. The response surface method is the least straight forward method for an algorithmic component reliability analysis; however, it is useful for the system reliability evaluation. For a system level reliability analysis two methods were considered: the ß-unzipping method and the branch and bound method. The ß-unzipping method is based on a level-wise system reliability evaluation where the structure is modelled at different damaged levels according to its degree of redundancy. In each level, the so-called unzipping intervals are defined for the identification of the critical elements. The branch and bound method is based on the identification of different failure paths of the structure by the expansion of the structural failure tree. The evaluation of the damaged states for both of the methods is the same. Furthermore, both of the methods lead to the development of a parallel-series model for the structural system. The only difference between the two methods is in the search approach used for the failure sequence identification. It was shown that the ß-unzipping method provides a better algorithmic approach for evaluating the system reliability compared to the branch and bound method. Nevertheless, the branch and bound method is a more robust method in the identification of structural failure sequences. One possible way to increase the efficiency of the ß-unzipping method is to define bigger unzipping intervals in each level which can be possible through a computerised analysis. For such an analysis four major modules are required: a general intact structure module, a damaged structure module, a reliability analysis module, and a system reliability module. In this thesis different computer programs were developed for both system and component reliability analysis based on the developed algorithms. The computer programs are presented in the appendices of the thesis.
Alignment of South African National Building Regulation deemed-to-satisfy wall configurations to the loading code
(Stellenbosch : Stellenbosch University, , 2023-03) Rabie, Nadia; De Villiers, Wibke Irmtraut; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: The revision of the South African wind loading standard, SANS 10160-3 published in 2019, resulted in an increase of design wind load for South Africa of 11 % (Botha et al., 2019). Due to the cautious design restrictions of prior seismic standards, a new seismic loading standard, SANS 10160-4, was developed in 2009. However, since the deemed-to-satisfy walling solutions (SANS 10400-K) of the National Building Regulations (NBR) were created in 2000, they may not satisfy the most recent wind and seismic loading standards. The possible discrepancy between the National Building Regulations and South African loading standards could have an impact on the structural performance of South African masonry buildings. Many low-income housing owners have reported that the structure is inadequate and lacks quality. Furthermore, De Villiers (2019) showed that conventional masonry walls based on the NBR's deemed-to-satisfy solutions fail sustain the required design loads. With this said, there is still currently a housing shortage of 3.7 million (SA Stats, 2019) which is expanding at a rate of 178 000 units per year (Di Lollo et al., 2019). In addition, the government is struggling to meet the moving target and is shifting their policy to providing serviced land only which may increase self-builds. Therefore, it is required to conduct assessments on low-income housing that is subjected to wind and seismic loading according to SANS 10160-3 and SANS 10160-4. To analyse these discrepancies, various low-income housing buildings layouts were designed consisting of the most vulnerable wall configurations permitted by the National Building Regulations taking into account building energy usage, natural lightning, constructability, South African construction practice and skill level. Thereafter, the worst-case wind and seismic loadings according to South African loading standards are calculated and applied to the vulnerable wall configurations through computational modelling, using finite element analysis (DIANA FEA). To analyse the capacity of the wall configurations, the simplified micro-modelling approach was used together with two input parameter sets. The first parameter set represents masonry in South Africa's low-income housing general practice and is obtained through experimental results performed by Fourie (2017). The second parameter set represents the minimum requirements specified by the relevant South African standards. The results revealed that the majority of the deemed-to-satisfy wall configurations fail to meet the required ultimate limit state wind design load. Under ULS-S loading, the study findings indicate that the slenderness of the pier adjacent to the return wall governs the wall capacity. Therefore, SANS 10400-K does not provide sufficient requirements for deemed-to-satisfy panel walls and gable walls to sustain the ULS-W and SLS loading required by the updated wind loading standard of South Africa (SANS 10160-3, 2019) as well as the seismic loading standard (SANS 10160-4, 2017). It is recommended that the minimum required geometry requirements provided by SANS 10400-K (2011) as well as the minimum requirements for material parameters provided by the South African standards should both be increased to the ensure the subsequent structural capacity of the walls exceeds the design load required by SANS 10160-3 (2019) and SANS 10160-4 (2017).
Alkali-resistant glass textile reinforcement of 3D printed concrete
(Stellenbosch : Stellenbosch University, 2022, 2022-12) Janse van Rensburg, Johannes Jacobus; Combrinck, Riaan; Babafemi, Adewumi John; Civil Engineering; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Additive manufacturing such as 3D concrete printing (3DCP), has recently gained significant attention due to its numerous benefits. However, 3DCP still has significant challenges to overcome before it can be fully adopted as a feasible alternative to conventional construction methods. The reinforcement of 3D printed concrete elements has proven to be challenging and needs to be addressed. Moreover, there are multiple aspects to this challenge that need to be taken into account, such as the lack of clear space above the filament layer being printed, difficulty in installing the reinforcement in different directions as well as integrating the reinforcement into the printing process. Various strategies have been studied in order to address these challenges, with different materials used as reinforcement before, during or after printing. However, before reinforcement can be applied, the behaviour of the consequent composite materials must first be studied. This study, therefore, investigates the flexural performance and behaviour of two different alkaliresistant (AR) glass textile materials as reinforcement to determine whether it is a feasible solution. During this study, two different methods of printing and applications of the textiles are considered, one where the elements are printed vertically and the textiles are pre-installed, and one where the elements are printed horizontally and the textiles are installed during the printing process. The textiles are applied in two different locations, one at the middle of the depth of the sample and one lower down. Samples are extracted from these printed elements and tested in flexure by conducting fourpoint bending tests 28 days after printing. After conducting these tests, the crack sequence and failure mechanisms of the variations are investigated. Furthermore, an optical microscope is used to gather more information regarding the performance and failure of the various samples. The results show that there is a significant increase in the flexural performance of the samples reinforced with an AR glass Textile A. Textile A is fully impregnated with epoxy resin, with high tensile strength, stiffness, and large cross-section area. Additionally, the application of this textile promotes deflection hardening structural behaviour. However, in contrast, there is a significant increase in ductility with no increase in flexural strength for the samples reinforced with an AR glass Textile B. Textile B is coated with styrene butadiene, with high tensile strength but a small section area. The results further indicate that the samples reinforced lower in the sample experience higher flexural strength with lower ductility and more variability in behaviour. During testing, it is also discovered that voids form underneath Textile A when applied to horizontally printed samples (between the interlayers), and that these voids influence the performance of the samples. The voids further influence the failure mode as well as the cracking sequence. Investigation of the failure of the samples reinforced with Textile A show two failure mechanisms occurring, namely, delamination and shear. Delamination always occurs when the textile is applied in the middle of the depth of the samples, but shear only occasionally occurs for the variation where the textile is applied lower in the sample. Additionally, telescopic failure is detected for Textile B. It is concluded that for both the textiles, the best performance, behaviour and repeatability are observed when the elements are vertically printed, and the textiles are placed in the middle of the depth of the sample. Among others, it is recommended to apply different variations of textiles, use different application techniques (such as retrofitting) and to explore the micro mechanical behaviour of 3DPC elements reinforced with textiles in future studies.
Alternate methods to determine the microstructure of collapsible soils
(Stellenbosch : Stellenbosch University, 2015-12) Asante, Samuel Yaw; Fouche, Nanine; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Collapsible soil is one of the most widely distributed problematic soils in the world including South Africa. Extreme leaching and erosion of the colloidal matter and fine particles creates a structure similar to a honeycomb within the microstructure of these soils, leading to the formation of a collapsible grain structure. Upon wetting and under additional loading these soils undergo a significant decrease in volume resulting in severe damage to structures. In South Africa the collapse phenomenon, which is regarded a geotechnical hazard, was first identified in the 1950’s. According to Rogers (1995), a geotechnical engineer needs to be able to identify these soils by examining in detail the properties of collapsible soils by listing the features commonly associated with it; which includes:  An open soil structure;  A high void ratio;  A low dry density;  A high porosity;  Geologically young or recently altered deposit;  High sensitivity and  Low inter-particle bond strength. The first four features suggested by Rogers (1995) suggest that the collapse phenomenon is directly controlled by the microstructure of these collapsible soils. From Rogers’s definition, it can be concluded that the microstructure of collapsible soils are governed by the following: porosity, pore size distribution, grain size distribution, pore fluid content, and ions on the grain and in pores (mechanical properties). Each of these microstructure properties can be examined and/or determined by laboratory testing or field observation. For this reason, the collapse behaviour of two soil types (reworked residual granite and residual Malmesbury shale) within the Stellenbosch municipal area was investigated by examining the microstructure and mechanical behavior of these soils. Alternate methods (CT-scanning and scanning electron microscopy) as well as conventional laboratory tests were applied. The aims of the study was achieved by developing a soil testing method using x-ray computed tomography (CT-scanning) and scanning electron microscopy (SEM) to determine the porosity, void ratio, particle size distribution, particle shape, and pore size distribution of residual soils. In order to achieve this, the VGStudio Max version 2.2 coupled together with Avizo Fire image analysis software version 8.0 were used in filtering and classification and distribution of voids, and particle size distribution within the soil microstructure. The image analysis was achieved by examining three dimensional (3D) and two dimensional (2D) X-ray images obtained using a General Electric Phoenix VTomeX L240 X-ray micro computed tomography scanner (microCT) and ZEISS EVO MA15 scanning electron microscope. From the image analysis, it was found that substantial volumetric changes (settlement) occur within the macropores of a potentially collapsible soil. The measured particle size distribution (PSD) by CT-scanning compared relatively well with the mechanical sieving method, although a few discrepancies were noted between the two methods. The image analysis from the SEM 2D images revealed that the particle morphology and mineralogy contributed greatly to the degree of collapse. The PSD from SEM images using imageJ (image analysis software) was not possible due to the bleeding effect of fine to medium-sized particles. It can thus be concluded that CT-scanning and SEM are good alternative methods to investigate the microstructure of soils; and further research in this regard is indicated.
Alternative wall-to-slab connection systems in reinforced concrete structures
(Stellenbosch : Stellenbosch University, 2016-12) Gerber, Johannes Daniel; Van Zijl, G. P. A. G.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: In the construction of multi-storey buildings, the reinforced concrete (RC) core or shear walls normally precede the construction of the RC floors. A system is therefore required to connect the floors to the already cast walls. There are many different floor-to-wall connection systems available in South Africa, but their behaviour and capacity are not always fully understood, especially when the moment capacity of the joint is to be utilised in order to design more economical structures. This research investigation focusses on four systems. The first is the conventional way of casting walls and floors by using continuous starter-bars that protrude through the formwork. The second system makes use of pre-bent site-installed starter-bars that are fixed within the wall, straightened after the wall is cast and then lapped with the slab reinforcement. The third system is also based on the principle of pre-bent starter bars, but they are pre-assembled inside a steel box to speed up the installation process and ease access to the bars once the wall is cast. Another system, that is not as popular in South Africa yet, is the use of cast-in anchors with mechanical couplers. The anchors are cast into the concrete wall and, once the form work is removed, threaded continuation bars are screwed into the couplers to make the connection between the floor and wall. The design procedure for the continuous starter-bar system is well understood and documented in design codes, but not enough information is available on the design procedure for the other systems. Certain practical aspects of the installation process are also not fully understood. Cold bending and straightening of the starter-bars are inevitable in both bend-out systems. Previous research shows that this cold working of the reinforcement can reduce the yield stress, ductility and E-modulus of the steel. In order to investigate these findings, a series of tensile tests are conducted on Y10 and Y12 reinforcement (high yield, deformed reinforcing bars). The results indicate that a significant reduction can be expected in both the yield stress and modulus of elasticity of the steel. A low cycle fatigue test further con rmed that a reduction in the ductility of the steel is also present. The next phase in the research investigation is to construct full scale models of the four connection systems. The systems are installed in four separate joints between a cantilever oor and a free-standing wall. The systems are designed to all have the same moment and shear capacity and are based on a typical wall-to-slab connection found in an o ce block. The construction of the models are done in such a way as to mimic the construction methods in practice as closely as possible. The entire process is done in a controlled environment, with a best practice approach adopted. Once the models are constructed, a load is applied at the tip of the cantilever oor in order to generate a bending moment and shear force at the wall-to-slab joint. The displacement of the specimen is monitored throughout the test. The structural performance is subsequently compared in terms of tip displacement, crack widths and ultimate resistance. The e ect of the cold bending on the starter-bars is clearly visible, as both the responses of the bend-out systems are less desirable than the results from the continuous starter-bar system. The experimental phase is followed by numerical analysis of the connection systems. Once the FE model is calibrated and veri ed with the data from the experimental phase, a sensitivity study is conducted. The e ect of either varying the steel or the concrete properties on the structural performance of a slab-to-wall connection is investigated. The FE results shows that the structural performance is signi cantly more sensitive to a reduction in the yield stress of the starter-bars, than to the use of a lower concrete grade. Finally, the systems are compared in terms of their constructibility, availability, material cost and their structural performance. Some recommendations on quality control matters and best-practice principles are also discussed. It is concluded that all the alternative connection systems can be successfully implemented in a moment-fixed wall-to-slab connection. The site-installed bend-out system performed the best structurally, but other practical considerations and project specific aspects might play an even bigger role in deciding which system to use in practice. Further, in order to ensure that the bend-out systems perform on the same level as the conventional system, it is recommended that the design should be conducted with a set of modified steel properties to allow for the negative effect of the cold working on the starter-bars.
Altimetry comparison, backward wave refraction and extreme wave analysis of NCEP data: Cape Point to Richards Bay
(Stellenbosch : Stellenbosch University, 2018-12) Barnes, Jarryd; Schoonees, K.; Rautenbach, C.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: Offshore wave climate along the south and east coast of South Africa has been investigated in this thesis. The design waves are needed to understand the offshore wave climate and necessary for the design of structures in this region. The wave condition data was produced by the WAVEWATCH III numerical model, i.e. NCEP data. The ultimate aim of the study was to derive extreme wave estimates off the South African coastline and assess its accuracy through comparison of various datasets. Comparisons of Satellite Altimetry data with NCEP and wave buoy data at two locations along the south coast (Cape Point and FA-Platform) was performed. Thereafter, wave conditions, obtained from 'backward' refracting nearshore data to the offshore NCEP locations, were performed in an attempt to validate NCEP data for East London and Richards Bay. Two approaches were conducted in order to backward refract, namely; Snell's Law (serving as a first estimate) and SWAN (fully describing the wave processes). The SWAN approach achieved offshore conditions by running a numerical model of various input conditions and creating a lookup table or matrix by means of an interpolation function using those general input conditions and output results. The methodology is important as neither the SWAN outputs nor the NCEP data could be regarded as 'ground truth'. An Extreme Wave Analysis was performed for the offshore NCEP data at six locations along the south and east coast of South Africa. An Exponential, Gumbel and 3-parameter Weibull distribution was conducted, where it was found that the latter was a best fit for the South African waters. An objective and conservative automated Peaks-over-Threshold (POT) value technique was used and wave heights for 1 in 1, 5, 10, 30, 50 and 100 year return periods with associated directions were obtained. Lastly, an analysis of the different distributions as well as percent exceedance graphs of the peak period per site was performed and compared.
Analysing the Behaviour of Soil Reinforced with Polyethylene Terephthalate (PET) Plastic Waste
(Stellenbosch : Stellenbosch University, 2016-03) Luwalaga, John Groover.; De Wet, Marius; Vijay, P. V.; Stellenbosch University. Faculty of Engineering. Dept of Civil Engineering.
ENGLISH ABSTRACT: Environmental issue effects like natural resource depletion, climatic change and global warming have significantly influenced the innovations in material science and technology with the aim of attaining sustainable materials to avert calamities. Conservation and sustainability of quality natural materials in the civil engineering field is a challenge currently due to their scarcity brought about by increased population, rapid development of cities and continued depletion of such materials. On the other hand, currently there is a boom in the plastic industry as most of the sectors like agriculture, automotive, education, government, health, marketing and advertising, transportation, to mention but a few use plastic products. Due to the wear and tear of the plastic products there is a challenge in handling the non-biodegradable plastic waste by the solid waste management field. This research has been conducted to mitigate the challenges faced by the civil engineering field and the solid waste management field by analysing sand-PET (Polyethylene Terephthalate) plastic waste composite. The research was conducted at Stellenbosch University (SUN), using materials like PET plastic waste flakes from the Kaytech factory and sand of medium dense, clean quartz uniformly graded with round shaped particles which is predominant in Western Cape region, South Africa. Furthermore, the aim of this research was achieved through the experimental work which included particle size distribution testing, compaction testing, California Bearing Ratio (CBR) testing, and direct shear box testing. Sand was reinforced with randomly mixed PET plastic waste flakes of different varying percentages of 12.5%, 22.5% and 32.5%, and tests were performed on unreinforced sand and sand-PET plastic waste composite specimens. It was established that sand reinforced with 22.5% of PET plastic waste flakes gave an optimum value of PET plastic waste giving a maximum percentage increase in friction angle of 15.32%, hence the highest shear strength with an angle of friction equal to 44.4o.Furthermore, the optimum maximum dry density of 1547kg/m3 resulted into a maximumfriction angle of 44.4o. It was concluded that the appropriate percentage of PET plastic wasteto use while reinforcing sandy soil used in this study is 22.5%. Therefore, it was established that reinforcing soil with 22.5% PET plastic waste can improve its bearing capacity and CBR. The soil-22.5% PET plastic waste composite can be applicable in civil engineering applications like as material for foundation bearing strata, light road sub-base or subgrade, and as backfill materials for foundations and retaining walls. Additionally, the study has established that reinforcing soil with 22.5% PET plastic waste is sustainable, hence mitigating the social, economic and environmental impacts by reducing need for natural resources, no land filling of PET plastic waste, and increased utilisation of poor quality construction soils like sand. Furthermore, calculations where done and found out that reinforcing sand with 22.5% reduced the width of the foundation by 3% which made it more economical compared to unreinforced sand.
An analysis into the invigoration of a rail corridor through private sector investment and transit oriented development principles
(Stellenbosch : Stellenbosch University, 2021-12) Van Rensburg, Albertus Gerhardus; Bruwer, Megan; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: The steady decline in passenger volumes using the passenger railway network in South Africa since the implementation of the Transport Deregulation act in 1988 has escalated to a steep decline in passenger volumes since the early 2000’s. Train set loss, out-of-date technology, maintenance issues, operational inefficiency, a lack of skills development and safety and security issues have drastically reduced passenger utilisation across all public passenger rail networks in the country. The Passenger Rail Agency of South Africa (PRASA) has recognised the passenger decrease trend and is now actively trying to reverse the tide. PRASA unveiled a variety of key programmes in the 2020/2022 PRASA Medium Term Expenditure Framework (MTEF) Corporate Plan aimed at revitalising the national public passenger railway service by adding 3600 new rolling stock units to the current passenger train fleet and modernizing 135 stations along priority corridors (PRASA, 2018). The acquisition of new rolling stock and modernisation of stations are vital in reversing decades of neglect towards rail-based transport. This supply invigoration will need to be accompanied by a paradigm shift in how current and potential rail users view passenger rail transport if the demand for rail services is to be successfully and sustainably re-invigorated. This study analyses the ability of private sector investment and Transit Oriented Development (TOD) principles to re-invigorate passenger rail and provide the vital paradigm shift in how the public views passenger rail in South Africa. The analysis is conducted by assessing the anticipated effects of Stellenbosch Bridge on rail utilisation trends through a computer model of a section of the transport network. Stellenbosch Bridge is a proposed development designed using Transit Oriented Development principles located adjacent to a section of the railway line in the Cape Winelands. The proposed development will have direct access to the rail network, connecting Stellenbosch Bridge to surrounding suburbs, towns, and cities such as the Northern Suburbs of Cape Town, Stellenbosch, and Paarl. Stellenbosch Bridge provides an opportunity to assess the effects of a Transit Oriented Development on rail utilisation as it is located in a transit corridor which provides both road and rail movement alternatives. A variety of scenarios were developed to investigate the effects of revisions to passenger accessibility and the rail system itself, which are modelled by altering the way in which people view transport options in the study area. Analysis of the output is focused on the station usage rate and fluctuation in passenger volumes for each scenario set. A thorough study of the results produced by the simulation model allows the conclusion to be made that Transit Oriented Development principles and private sector investment can indeed re-invigorate rail and provide the required paradigm shift in how potential and current users view the passenger rail service.
An Analysis of flow characteristics of unconventional weaving traffic: Western Cape case Study
(Stellenbosch : Stellenbosch University, 2021-03) Masegela, Mathabo; Bruwer, Megan; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: The objective of this study is to analyse the characteristics of unconventional weaving behaviour of traffic within freeway sections and propose remedial measures. Thereby gaining a more detailed understanding of unconventional weaving behaviour, causes and possible solutions. Unconventional weaving traffic is defined as weaving that is not conventional according to the definition in the USA Highway Capacity Manual. It refers to excessive lane changing or weaving that occurs as a result of the geometry of the road, illegal behaviour, disregard of traffic marking etc. For purposes of this study the South African National Road N1 in the Western Cape between the R300 on-rampand the Okavango Boulevard was selected as the case study. The section of the road under consideration experiences a high number ofunconventional weaving manoeuvres resulting from the short distance between successive on-ramps (R300, Okavango), an observed general disregard of the lane markingsby numerous motorists(at the R300 on-rampdiverge point) and geometry of the section of road (particularly because no auxiliary lanesare provided). A regression analysis together with fundamental traffic flow diagrams are developed and applied to the base case and proposed remedial actions. The results indicate that weaving within the case study area can be improved by increasing the capacity of the R300 onramp and maintaining a lane balance. It is also observed that weaving within this section is not only related to the operations of the road but is also linked to human behaviour that may not be modelled.
Analysis of nearshore current patterns using aerial drone measurements at monwabisi
(Stellenbosch : Stellenbosch University, 2019-12) Abrey, Ryan Phillip Shaw; Schoonees, K.; Croukamp, L.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
ENGLISH ABSTRACT: This thesis explores the development of a methodology for using quadcopter aerial drones to measure currents in the nearshore zone, along with assessing other possible applications within the marine environment. Current velocities were measured at Monwabisi beach in False Bay, Cape Town to enable the results to be compared with similar studies already conducted in the area. This provided a means of result validation, as the scope of the study did not include budget for measurement of sea currents with electronic instruments during the testing for comparison. The primary drone used during testing was a DJI Mavic Air due to its affordable price and ease of use, making it more accessible to most users. Calibration tests were conducted on land to measure a fixed known length in order to adequately scale the photos taken by the drone to the altitude recorded by the on-board altimeter. During calibration the drone was flown at different heights with the camera facing directly down and a set of photos were taken of a tape measure which could then be scaled in AutoCAD. This was crucial as the typical land-based method of photogrammetry, to determine height and distance from the drone, would not be reliable over water as its surface is constantly shifting. A set of coordinates of a static point was also measured in order to determine the horizontal accuracy of the reported coordinates which rely on the on-board GPS measurements. It was found that the measured coordinates required smoothing to compensate for GPS errors encountered by the drone. The drone used has a reported horizontal hovering accuracy of ±1.5 m but was found to produce a measured mean current precision below 2 cm.s⁻¹ once averaged over 10 seconds. This information filtered into a method for tracking drifters as they floated on the sea surface behind the surf zone. This is similar to the existing method of GPS current drifters; however, biodegradable oranges could now be used in their place with the drone above measuring their coordinates as they drifted on the currents. Several tests were then carried out during different environmental conditions at Monwabisi and a range of currents were measured for comparison with the previous studies. Measurements taken by the drone resulted in similar current patterns to those seen in the previous studies model results. Furthermore, the current velocities were of the same order of magnitude. It was also found that the drone could observe other aspects from above such as: effluent plumes at diffusers, marine life and even sediment movements. Each of these aspects could prove valuable for coastal studies in providing data at a reasonable cost. Overall, the findings proved that a quadcopter aerial drone is a versatile engineering tool which was able to measure currents in the nearshore zone while finding similar flow patterns to previous model results.

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