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.

Thesis (MEng (Civil Engineering))--University of Stellenbosch, 2007. / Cold mixed asphalt concretes consist of bituminous binder, either cutback or emulsion, and aggregates that have not been heated. Cold mix asphalt is often used due to unavailability of hot mix asphalt in the vicinity of the project and also used for temporary patches. The poorer performance of the materials associated with expensive cold mixes will results in greater overall cost for patching due to increased cost of labour, equipment and traffic control. The main objective of this study was to evaluate performance of proprietary cold mix asphalts available in South Africa. Five products were used in this study, which are Roadfix, Tarfix, Much- Asphalt mix, Asphalt King and Glenpatch. Engineering properties of products were investigated, including volumetric properties, permeability and Indirect Tensile Strength. In addition, for performance properties, accelerated pavement testing using Model Mobil Load Simulator (MMLS3) was carried out. The testing was done dry at 50o C up 20,000 load repetitions. It was found out that all five products have high void contents which range between 15.1% and 23.5%. This makes these cold mix asphalts to be highly permeable. Indirect Tensile Strength values were found to be very low compared to minimum value of 800 kPa specified for Hot Mix Asphalt. Products with emulsion as binder (Asphalt King and Glenpatch) were found to be more susceptible to water damage compared to other mixes with cutback binder. MMLS3 test results showed that Asphalt King was less susceptible to rutting compared to the other four products. In general all products are very highly susceptible to rutting compared to Hot Mix Asphalt.

Thesis (MEng (Civil Engineering))--University of Stellenbosch, 2007. / In the past use was made of prescriptive design rules to provide for the fire limit state. Modern Design Codes provide the scope and the means to design for fire in a performance based manner. The Eurocode provides guidance on the actions on structures exposed to fire as well as methods to predict the structural behaviour of elements in fire. Structural designers can now incorporate the use of parametric fire curves to describe compartment fires. These fire models are not an extension of the old nominal standard temperature time curves. Parametric curves are analytical models that are based on natural fire behaviour. The temperature in the fire compartment can be predicted in a scientific manner taking account of fire loads, ventilation conditions and compartment characteristics. The combination of rational fire models and temperature dependant structural behaviour enables designers to predict whether elements will fail during a fire. This is an improvement on the empirical prescriptive fire resistance ratings, used to date. Multi-storey steel framed structures, with composite floors, were identified as structures with high inherent fire resistance and robust behaviour. The composite beams in the floor structure were identified as critical elements when subjected to fire. The deterministic design and the reliability level of these elements were studied. Deterministic fire design procedures are presented that can be used to design unprotected composite beams for the fire limit state. The reliability of the deterministic design procedures was evaluated through a First Order Reliability Method. Parametric fire curves are suitable for reliability analysis due to the fact that they can be described by stochastic variables. The fire load was determined to be the dominant variable influencing the reliability level of the composite beams. The ventilation conditions of the fire compartment also has important implications for the temperature development of the composite beams. The reliability analyses results show that reasonably sized composite beams can be used as unprotected elements in smaller fire compartments with moderate fire loads. It was found that a structural element’s total probability of failure can be improved by the use of active fire fighting measures. The benefit of active fire fighting measures can be quantified by considering their probability of failure. By use of conservative assumptions and basic knowledge of fire engineering principles, rational design methods can provide safe and economical solutions for fire design of composite beams.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / In order to plan the engineering work of large construction projects efficiently, a model of the engineering process is required. An engineering process can be modelled by sets of persons, tasks, datasets and tools, as well as the relationships between the elements of these sets. Tasks are more often than not dependent on other tasks in the engineering process. In large projects these dependencies are not easily recognised, and if tasks are not executed in the correct sequence, costly delays may occur. The homogeneous binary relation “has to be executed before” in the set of tasks can be used to determine the logical sequence of tasks algebraically. The relation can be described by a directed graph in the set of tasks, and the logical sequence of tasks can be determined by sorting the graph topologically, if the graph is acyclic. However, in an engineering process, this graph is not necessarily acyclic since certain tasks have to be executed in parallel, causing cycles in the graph. After generating the graph in the set of tasks, it is important to fuse all the cycles. This is achieved by finding the strongly connected components of the graph. The reduced graph, in which each strongly connected component is represented by a vertex, is a directed acyclic graph. The strongly connected components may be determined by different methods, including Kosaraju’s, Tarjan’s and Gabow’s methods. Considering the “has to be executed before” graph in the set of tasks, elementary paths through the graph, i.e. paths which do not contain any vertex more than once, are useful to investigate the influence of tasks on other tasks. For example, the longest elementary path of the graph is the logical critical path. The solution of such path problems in a network may be reduced to the solution of systems of equations using path algebras. The solution of the system of equations may be determined directly, i.e. through Gauss elimination, or iteratively, through Jacobi’s or Gauss-Seidel’s methods or the forward and back substitution method. The vertex sequence of an acyclic graph can be assigned in such a way that the coefficient matrix of the system of equations is reduced to staggered form, after which the solution is found by a simple back substitution. Since an engineering process has a start and an end, it is more acyclic than cyclic. Consequently we can usually reduce a substantial part of the coefficient matrix to staggered form. Using this technique, modifications of the solution methods mentioned above were implemented, and the efficiency of the technique is determined and compared between the various methods.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / The aim of this thesis is to study the stabilising effect which vertical ribs may have on a tall cylindrical structure, with the focus on the proposed Solar Chimney. The report begins with a brief introduction to the Solar Chimney concept. A study is made of flow regimes which exist for flow around a circular cylinder and these flow regimes, together with their characteristics, are described. Various threats to the Solar Chimney are identified and will be investigated. The natural shape and strength of the Saguaro Cactus leads to the investigation of vertically ribbed cylinders. Experimental wind tunnel tests are performed in Tokyo, Japan to obtain external pressure distributions. A smooth cylindrical model, as well as two different configurations of vertically ribbed cylinders are tested. These external pressure distributions are numerically integrated in order to obtain calculated drag coefficient values for the cylinders. The drag coefficients for a smooth cylinder and cylinders with vertical ribs are obtained experimentally by means of total drag force measurements. These tests were performed in the wind tunnel at the University of Stellenbosch. The effect of aspect ratio of a smooth cylinder is also addressed. Computational Fluid Dynamics (CFD) analyses are carried out using the CFD software program, FLUENT. Both the drag coefficient and the external pressure distributions were investigated in this way. The differences between theoretical conditions and those of real life conditions of a smooth cylinder are discussed. The report ends by concluding the stabilising effect of vertical ribs on tall cylindrical structures and how these ribs may eliminate some of the present threats to the proposed Solar Chimney.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / The floodplain of a river forms a close relationship with the stream that created it. Not only does the river influence the characteristics of the floodplain, the floodplain can also very easily influence its river, as is evidenced by examples such as the Huang He River in China and the Columbia River in Canada. These two cases clearly indicate that suspended sediment has a pronounced influence on the floodplain. This thesis investigates the processes which cause sediment to move onto the floodplain. As observed in many rivers worldwide suspended sediment on the floodplain has a tendency to settle near but not directly next to the main river channel. This gap between the river channel and the location of highest sedimentation rate stems from the fact that there is a zone of relatively higher turbulence at the boundaries of the floodplain. Close to this zone flow on the floodplain is increased in velocity whilst the flow velocity in the main channel is decreased as can be seen in the figure below: ...

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2005. / In the inverse finite element method (iFEM), given a finite element model of a structure and imperfect displacement measurements, the external loads acting on the structure can be assessed. The basic idea behind iFEM is the optimization of a quadratic cost function of the difference between the measured and estimated values, with a high cost corresponding to a high precision of the measurements. In the present research it is firstly shown how the iFEM theory was broadened to accommodate for strain measurements through the construction of cost matrices to express the cost associated with the estimation of the response. The main focus of the research falls however on the influence that the measurement set-up has on the quality of the iFEM estimates. Only a limited number of measurements may be available, therefore it is essential to plan the measurement set-up carefully to obtain the highest quality of estimates. The number of measurements and the precision required to obtain a realistic result from an iFEM analysis is also a factor which plays a role and varies for different types of measurements. A numerical method for systematic sensitivity study of the measurements set-up without involving the actual measurement data, is presented. Two examples consisting of structures with both displacement measurements and strain measurements being taken, are presented. It illustrates how the sensitivity study method can be used to plan a more effective measurement set-up.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / There are currently well established compaction methods being used in laboratories globally to prepare specimens for material testing. None of these methods provides the repeatability and reproducibility, ease of execution or simulation and correlation to field compaction desired by engineers. The research presented in this report was aimed at the development of a new or adapted compaction method for bituminous stabilized materials (BSM) that would address the aforementioned factors, by making use of a vibratory hammer. Along with this, a new protocol was to be established. The initial vibratory hammer that was tested was the Kango 637®. This specific vibratory hammer suffered irreparable damage to the gearbox during the research. A replacement Kango hammer could not be purchased, therefore a substitute hammer was purchased i.e. a Bosch GSH 11E®, for which back-up service and replacement parts are readily available throughout South Africa. Significant progress had been made with the development of a laboratory compaction protocol for BSM using the Kango Hammer. The specifications of the Bosch® hammer showed it was superior in terms of power, weight and other technical features. Comparative testing was therefore carried out. This allowed for the adaptation of the results achieved to that point. Extensive experimentation was then carried out using two types of BSM i.e. foamed bitumen (80/100 bitumen) and bitumen emulsion (60/40 Anionic Stable Grade) stabilized material. The initial material used for the experimentation was a G2 quality graded crushed stone. Additional material was also obtained from a recycling project taking place along the N7 near Cape Town. The N7 material was used to perform correlation experiments so as to determine how representative the laboratory compacted specimens were to field compacted material. Results showed that the vibratory hammer is capable of producing specimens for testing in the laboratory as well as providing a possible benchmark method for accurately controlling the quality of work on site i.e. field density control. This was done by identifying the time to and level of refusal density compaction. The level of refusal density compaction was expressed as a percentage of Mod AASHTO compaction and using current specifications, a potentially new site compaction level specification was determined. In order to asses the material applicability of the vibratory hammer compaction method, tests regarding moisture sensitivity analysis were carried out on a G5 material. The vibratory compaction protocol includes a specification for the type of hammer, guide-frame, surcharge weight, compaction moisture and number of layers. Vibratory compaction can be used to prepare two types of specimens: • Specimens for triaxial testing with a diameter of 150mm and a height of 300mm • Specimens for laboratory testing with a diameter of 150mm and a height of 125mm. Tests showed that the material properties prove to have an influence on the compactability of the material. Material from the N7 recycling project had been milled out thus altering the grading and including some RAP. This in turn influenced compaction. The vibratory hammer moisture curve was found to shift slightly to the left when compared to the Mod AASHTO moisture curve. The variability of the vibratory hammer was found to be well below the specified variability of 15%. Repeatability experiments on G5 material indicate that vibratory hammer compaction may be used on lesser quality granular materials. A recommended procedure for the compaction of BSM was developed following the experimentation results.