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.

Thesis (MEng (Civil Engineering))--University of Stellenbosch, 2007. / The failure rate of electric overhead travelling crane supporting structures across the world is unacceptably high. Failures occur even when the supporting structures are designed within the relevant design codes. This demonstrates a lack of understanding of the dynamic behaviour of cranes in many design codes. The current South African loading code is simplistic with respect to crane supporting structure design, relying on empirical factors to determine the correct loads. While these factors lead to predicted forces in the correct range of values, the Eurocode’s methods are more scientifically based. In recognition of this the draft South African code predominantly incorporates the methods used by the Eurocode to calculate design forces for crane supporting structures. The purpose of this thesis was to use an existing numerical model to determine the wheel loads induced by a crane into the crane supporting structure through hoisting, normal longitudinal travel, skewing and rail misalignment. The numerically obtained forces were then compared with the design forces estimated in the current South African code and the Eurocode, in order to determine whether the factors and methods used in the codes are accurate. The current empirically based South African code was found to be highly conservative. In contrast the scientifically based design forces from the Eurocode were close to the numerically calculated forces, only failing to predict the behaviour of the crane in the case of skewing. Further work needs to be completed in the estimation of forces induced during this load case. Once this is achieved it is hoped that the better understanding of the crane forces adapted from the Eurocode into the draft South African code will lead to a reduction in failures of electric overhead travelling crane supporting structures.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / The need for a more reliable testing procedure for the characterisation and Quality Assurance/ Control of Bitumen Stabilised Materials (BSMs), besides UCS and ITS testing, has long been recognised by the roads industry. In fact, at CAPSA 2004 and CAPSA 2007, discussions of improved test methods for granular materials, i.e. possible replacement tests for CBR procedures, were conducted in workshops. Triaxial testing for the evaluation of shear parameters is widely recognised as a reliable method of measuring these critical performance properties of granular and Bitumen Stabilised Materials (BSMs). However, the triaxial test in its current state as a research test has little chance of extensive use by practitioners and commercial laboratories, because of complexity, cost and time issues. Major adaptations to the research triaxial test are necessary, before this useful test can have a chance of being accepted by road practitioners. The main aim of this study is to investigate possibilities of developing a simple, affordable, reliable and robust test for characterizing granular and bitumen stabilized materials thus linking test outcome with in-situ performance. This is achieved through the innovative design and manufacture of a prototype triaxial cell capable of accommodating 150 mm diameter by 300 mm deep specimens. The cell is simpler than the research (geotechnical) triaxial cell and the operational protocols have been streamlined, thereby reducing the time and steps required in assembling specimens and testing them. In order to ensure the development of an appropriate triaxial cell for industry, a survey was conducted aimed at investigating currently available facilities, testing capacity and resources within civil engineering laboratories in South Africa. Findings of the survey (Appendix 4) have provided guidance with regard to the nature and sophistication of any new tests to be developed. The survey highlighted some of the limitations and lack of sophistication of the current loading frames used for CBR and UCS testing such as lack of electronic LVDTs, limited overhead space, limited loading capacity and others. Most laboratories would need to invest in new loading facilities to carry out triaxial tests. A review of the test procedure for monotonic triaxial test showed that two main factors contribute to the complexity of the research (geotechnical) triaxial cell namely, time taken to assemble the specimen accurately in the cell and secondly the inherent design of the cell which makes it water and/or air tight at relatively high pressures. The design of the Simple Triaxial Test, therefore, was aimed at overcoming the drawbacks of research triaxial test e.g. fitting a membrane to each specimen to be tested, through considerable simplification by means of a new structure design and procedure of assembly of specimen into the cell. The advantage of addressing these issues would be reduction in the number of steps required in the test procedure and therefore reduction in testing time. The design of the cell particularly was preceded by a conceptualization process that involved investigation of numerous options. Concepts such as the bottle, encapsulated-tube, bottle and sandwich concepts were considered and given reality checks. In addition, available triaxial procedures of a similar nature e.g. Texas Triaxial, were evaluated and analyzed. Ultimately, with some trials and innovation, a design was developed for a simple triaxial cell comprising a steel casing with a latex tube which is then introduced around the specimen sitting on a base plate. It is based on the ‘tube concept’ in which the specimen acts like a ‘rim’ and the cell acts like a ‘tyre’ providing confinement to the triaxial specimens for testing, within the tube. This approach eliminates the use of O-rings and membranes for the specimen and tie-rods for the triaxial cell, thus reducing testing time considerably. The overall dimensions of the cell are 244 mm diameter by 372 mm height (Appendix 5). The cell was manufactured at Stellenbosch University Civil Engineering workshop and preliminary tests were conducted under this study. Parallel tests were also conducted with the Research Triaxial Test setup at Stellenbosch University in order to determine if preliminary results obtained with the Simple Triaxial Test setup were comparable therefore providing a means of validating the data. Results of analysis of variance (ANOVA) show that variability between Simple Triaxial Test (STT) and Research Triaxial Test (RTT) results is less significant whilst that within samples of STT and RTT results is quite significant. Comparisons also show that good correlation were obtained from Reclaimed Asphalt Pavement (RAP) Hornfels + 3.3 % Emulsion + 0 % Cement mix and mixes with the G2 base course aggregate whilst completely different correlation was obtained from RAP + 3.3 % Emulsion + 1% Cement. It is evident however that the differences observed stem from material variability i.e. random variability to one degree or the other and not to the STT apparatus. It is recommended for future research that more STT versus RTT testing be done especially on a mix with known mechanical properties when compacted to a specified dry density, e.g. graded crushed stone (G1) compacted to 100% mod. AASHTO. In summary, a locally made, low cost, relatively durable triaxial cell with relatively easy and quick specimen assembly procedures has been developed. It is now possible to perform triaxial tests on 150 mm diameter by 300 mm high specimen relatively easily and quickly. However, the challenge of validating results obtained, as well as improving the manufacture process of its main component, the tube, still remains.

Thesis (MScEng (Civil engineering))--University of Stellenbosch, 2005. / In this study, the minimum standards required for the design of rural piped water supply projects as set by the Department of Water Affairs and Forestry (DWAF) are evaluated with respect to capital pipe cost using the Nooightgedacht rural water supply scheme selected as a case study.