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- Volume 56, Issue 1, 2014
Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Volume 56, Issue 1, 2014
Volumes & issues
Volume 56, Issue 1, 2014
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 2 –10 (2014)More Less
The paper assesses the impact of the recently completed Gautrain Rapid Rail link in Gauteng on property development in the vicinity of stations along the route. Our particular interest is in examining the extent to which the Gautrain, as a major public transport investment, has managed to stimulate and support the creation of Transit-Oriented Development (TOD) by leveraging private sector action, with the ultimate aim of moving towards more sustainable land use / transport environments. Data sources include property development records, aerial photographs and municipal zoning applications for the areas surrounding the Pretoria, Midrand, and Rosebank stations for the period 2000 to 2011, and interviews with officials and private property developers. The research found evidence of accelerated property development and increasing mixed use in all three station precincts, but significant variation in the extent to which TOD principles have been applied. Property developers considered the Gautrain to be a major factor attracting them to develop in station precincts, suggesting that the locational benefits offered by a high-quality public transport system are also present locally. However, when comparing the vibrant Rosebank with the slower-growing Pretoria and Midrand precincts, it is clear that real estate fundamentals drive property development and will ultimately determine the success of a TOD undertaking.
Factors predicting the intention to accept treated wastewater reuse for non-potable uses amongst domestic and non-domestic respondents : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 11 –19 (2014)More Less
Water reuse projects can fail if the factors (social, technical, financial, etc) governing their implementation are not adequately addressed prior to implementation. This paper presents the findings of the analysis of questionnaires administered to potential domestic and non-domestic consumers in Capricorn and Vhembe (Limpopo Province) where wastewater reuse was being considered. The analysis examined the factors considered to predict the intention to accept wastewater reuse prior to implementation. Structural Equation Modelling (SEM) was employed to test several hypotheses addressing respondents' intention to accept wastewater reuse for non-potable end uses. In other words, SEM tested whether certain factors (e.g. trust, attitudes and control) measured intention. Intention was measured as a second order factor. For non-domestic respondents, the factors that predicted intention to accept wastewater reuse in order of significance were their attitude towards wastewater reuse, the degree of control over the source of water and its application, the respondents' knowledge of the advantages of reuse and the respondents' trust in the service provider. For domestic respondents, the factors were their knowledge of the advantages of reuse, the degree of control over the source of water and its application, attitude towards wastewater reuse, trust in the service provider, and the subjective norms of the respondents. Physical quality satisfaction (for both respondent categories) and subjective norms (for non-domestic respondents only) could not be assessed because a reliable scale was not formed. The above findings have implications for future wastewater reuse in South Africa, i.e. that decision-makers contemplating reuse for non-potable uses would profit from addressing the various factors predicting intention to accept reuse prior to implementation.
The management of constructability knowledge in the building industry through lessons learnt programmes : technical paperAuthor V. KuoSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 20 –27 (2014)More Less
the 1980s the term "constructability" evolved in the USA. The proponents of this concept believe that constructability, which embraces both design and management functions, is comprehensive in facilitating construction operations and solving problems on site. Constructability problems are common on the construction site, due to the lack of construction experience in the design team and the absence of tools to assist designers in addressing constructability. Moreover, designs are predominantly done early in the project in the absence of contractor input, and there is yet no explicit means of defining or measuring constructability. This paper aims to address constructability problems in building construction, by understanding the nature of constructability knowledge and investigating how construction experience may be effectively disseminated amongst project participants, particularly through the use of lessons learnt programmes and inter-disciplinary knowledge sharing. It has been found that there is fundamental misalignment between consultants and contractors on the perceptions of criteria for a constructible design, implications of design decisions, and certain traits that may represent optimised vs poor constructability. The discrepancy in communication is the elemental cause of constructability problems and this research has demonstrated how lessons learnt programmes can be an effective tool in attaining better constructability knowledge management and collaboration.
Evaluation of the strength behaviour of unpaved road material treated with electrochemical-based non-traditional soil stabilisation additives : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 28 –39 (2014)More Less
Travel along unpaved roads is not always assured, because of their low standards, poor riding quality, impassability in wet weather, and the danger in the quantity of dust that is generated by moving vehicles and wind. Stabilisation with electrochemical-based non-traditional soil stabilisation additives (chemical additives) may offer a solution to this continual problem. The objective of this paper is to report on the strength behaviour of a typical marginal quality weathered quartz gravel material treated with two electrochemical-based non-traditional soil stabilisation additives, enzyme and sulphonated oil to assess their potential value for unpaved road construction under wet and dry conditions. These treated panels were trafficked under 100 vehicles per day. The evaluation was done by means of laboratory tests and field investigations for three years. The characteristics of the natural material and the binding ability of the non-traditional soil stabilisation additives were established from the laboratory testing. Density and moisture, and the strength development of the treated material were determined from field investigations. These two non-traditional soil stabilisation additives appear to have affected the particles and their water component, hence an increase in densities was achieved. The degree of formation and paste surrounding the particles appeared to have varied with time and differed between the additives. An increase in density in the sulphonated oil additive treated panel occurred three months after construction, and a further increase was again noticed eight months after construction (five months thereafter). Up to eight months after construction, the enzyme additive treated panel showed a significant decrease in density, but showed a slight increase thirty-one months after construction. This increase in densities might probably be because of further densification by traffic. The variations in density were attributed to testing variability. In the in situ and soaked DCP-CBR strength measurements, the sulphonated oil additive treated panel reached its maximum in situ strength at two months after construction, while the enzyme additive treated panel reached its maximum in situ strength at five months after construction. Up to eight months after construction, both treated panels indicated a significant decrease in both the in situ and soaked DCP-CBR strength conditions. The decrease was attributed to rain. There was, however, little evidence to show that the additives had improved the material, with the control panel being consistently stronger in both the in situ and soaked DCP-CBR conditions. The importance of considering the time factor in the strength development of non-traditional stabilisation test techniques, as well as the number of tests, was highlighted in the results of this study. The natural variability of the materials used in this type of study is generally high, and the precision of the test method is typically quite low. On this basis, it is usually difficult to draw definite conclusions.
The status of basic design ground motion provisions in seismic design codes of sub-Saharan African countries : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 40 –53 (2014)More Less
Basic provisions for design ground motions in seismic design codes of sub-Saharan African countries are critically reviewed. The seismic codes of Ethiopia, Kenya and Uganda are selected to represent the eastern region, Ghana to represent the west and South Africa to represent the south. The specific provisions considered are those pertaining to site effect and the recurrence period of the design earthquake. The codes are also compared with one another and with selected current international codes from the US and Europe, with respect to selected provisions. The provisions are further viewed from the perspective of the state of the art and the state of the practice. It has been concluded that these basic provisions in most of the sub-Saharan African codes considered are inadequate in guaranteeing safety of human life and limiting damage to property, suggesting a need for immediate updating, an exception being the South African code.
Soil-structure interaction provisions - a potential tool to consider for economical seismic design of buildings? : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 54 –62 (2014)More Less
Contemporary seismic design codes have become more stringent with respect to the requirements for design forces and deformations in building design. This paper demonstrates that it could be worthwhile to consider the introduction of soil-structure-interaction provisions into local design codes. This is partly to be able to offset the costs incurred by the high magnitude of base shear demand in most buildings attributed to site amplifications due to soft soil sites, as per the requirements of current codes, including the recent South African seismic design code. This beneficial effect of site soils is as a result of lengthening of the fundamental period and of the increased effective damping of the overall system due to soil-structure interaction, which in most cases lead to reduced design spectral values. The paper shows that, if pertinent provisions in some international codes are properly adapted, a substantial reduction in the base shear force can be achieved, in many cases resulting in structural-work cost saving. With this, the paper attempts to address the legitimate concern of design engineers regarding the potential escalation of construction costs associated with the introduction of stringent requirements of contemporary seismic design spectra, especially for soft soil sites.
Author J.E. Van ZylSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 63 –68 (2014)More Less
This study investigated factors affecting the average domestic water demand of a large number of suburbs in South Africa. Suburbs form an ideal demand grouping since they tend to have similar stand areas, climatic conditions and user characteristics. In addition, since properties within a suburb are close to one another, it may be reasonably assumed that differences in user demands will cancel one another out so that a designer only has to cater for the average demand of the suburb. A database on measured domestic water demands was used to determine the average of the Annual Average Daily Demand (AADD) for a large number of suburbs in South Africa (i.e. the average AADD per suburb), and this data was linked to census and climate data. The combined data set was then subjected to various regression analyses to identify the most important influencing factors. Stand area was found to be the most important influencing factor, validating the approach followed by the current South African design guidelines. However, the current guidelines were found to exclude a large number of measured data points, and thus a new, more comprehensive design envelope is proposed.
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 69 –76 (2014)More Less
Portal frames are steel structures used to construct industrial buildings. Conventional analysis techniques used by practising engineering professionals assume that the eave, ridge and base connections are either infinitely rigid or perfectly pinned. This approach leads to less accurate analysis of the displacement behaviour of portal frames when subjected to external loading. Portal frames must therefore be analysed with rotational springs at all connections to yield accurate displacement behaviour. This investigation focused on determining the accuracy and economic feasibility of modelling portal frame connections with rotational springs. The rotational spring stiffnesses of all connections were required before the portal frame could be analysed in a second-order two-dimensional non-linear analysis. The rotational spring stiffnesses unique to each connection were determined from the moment-rotation behaviour obtained from a series of finite element analysis simulations of each connection. Thereafter these stiffnesses were used to determine the vertical and horizontal displacements of the portal frame. These displacements were compared with experimental test results. The reasons for the discrepancies between the numerical and experimental results were investigated through a sensitivity analysis. The findings suggest that it is not computationally feasible to analyse portal frames with rotational springs, even though the model's predicted results are more accurate than those of conventional analysis using rigid and pin connections.
The application and interpretation of linear finite element analysis results in the design and detailing of hogging moment regions in reinforced concrete flat plates : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 77 –92 (2014)More Less
Finite Element methods have been used by civil and structural engineers since the 1960s, and the theory behind this is well researched. However, there is still a lack of direction on how to use the information obtained from this type of analysis to practically design a structure for strength and serviceability criteria. Design codes are broadly based on simplified calibrated strength models and are consistent with simplified and practical detailing. In this paper traditional methods of analysis of a simple pad foundation are compared with the linear finite element method, and the results compared to experimental results. The following questions are answered:
- Are the traditional simplified methods adequate with respect to overall strength?
- To what extent may finite element peaks or singularities be averaged or smoothed without compromising durability and serviceability?
- How should the reinforcement obtained from linear finite element methods be detailed?
Towards a systems thinking approach in allocating infrastructure budgets in local government : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 93 –99 (2014)More Less
Legislation, systems and processes provide a rigid framework within which local government operates. In a perfect world, perfect information would result in perfect decisions. However, the world is chaotic, people are far from perfect, and priorities vie for resources, as is evidenced through the social inequality and environmental degradation in society. A common way of managing complexity is to break complex processes into manageable portions. In doing so, the advantage of integration is often lost. Furthermore, silo thinking tends to yield duplication, often through localised efficiencies at the cost of overall value. System thinking can be employed to facilitate a constructive, creative space that has potential to evolve in the presence of intuitive trust, combined with a framework with which to measure and verify against. The City of Cape Town serves as example of a local authority grappling with allocation of resources in a manner which is fair and efficient in fulfilling its electoral mandate.
Analysing delay and queue length using microscopic simulation for the unconventional intersection design Superstreet : technical paperAuthor H.H. NaghawiSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56, pp 100 –107 (2014)More Less
With the increasing demand on today's roadway systems, intersections are beginning to fail at alarming rates prior to the end of their design periods. Therefore, maintaining safety and operational efficiency at intersections on arterial roadways remains a constant goal. This effort for sustainability has spawned the creation and evaluation of numerous types of unconventional intersection designs. Several unconventional designs exist and have been studied, including the Bowtie, Continuous Flow Intersection, Paired Intersection, Jughandle, Median U-Turn, Single Quadrant Roadway and Superstreet Median. Typically, these designs eliminate/reroute conflicting left-turn manoeuvres to and from the minor or collector cross road. High left-turning volumes are addressed by adding an exclusive left-turning signal. This consequently increases the required number of signal phases and shorter green time for the major through traffic. This paper describes the evaluation of an unconventional intersection designed to lessen the effects of high left-turning traffic. To aid in the evaluation of the unconventional Superstreet design, a comparison of a Conventional intersection's operation was made. Constructing and analysing a live Superstreet and Conventional intersection design is a massive undertaking. Microscopic traffic models were developed and tested using CORSIM. A variety of scenarios were created by changing the approach volumes and turning percentages on the major/minor roads to reflect different congestion levels that may occur at the intersection on any given day. The total number of created scenarios was 72, i.e. 36 scenarios for each design. Among the general findings of this research was that the Conventional design consistently showed evidence of higher delay time and longer queue length compared to the Superstreet intersection design. The reduction in the network delay ranged from 27.39% to 82.26%, and an approximate 97.5% reduction in average network queue length experienced on the major road's through lanes when the Superstreet design was implemented. This is a significant reduction, especially since the through lane volume of the major road is relatively high. These results are assumed to be due to the additional available green time for the Superstreet intersection design.
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56 (2014)More Less
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 56 (2014)More Less