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- Volume 53, Issue 2, 2011
Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Volume 53, Issue 2, 2011
Volumes & issues
Volume 53, Issue 2, 2011
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 2 –6 (2011)More Less
Many parties in the construction industry claim that codes of professional ethics can help mitigate the unethical conduct of civil engineers and improve the ethical level amongst construction players. However, the fact is, even though most organisations have their own codes of ethics, there still are many instances of unethical conduct in the construction industry. For this reason, this research attempted to study clients' perceptions of the impact on civil engineering works that codes of professional ethics have. Unethical conduct in the construction industry, such as fraud, bribery and collusive tendering, were addressed in 55 structured interviews. The interviews indicated the causes of the unethical conduct, as well as ways for mitigation. Finally, two models of disciplinary procedures to deal with unethical conduct were developed for the construction industry, particularly for civil engineers.
Application, advantages and limitations of high-density gravimetric surveys compared with three-dimensional geological modelling in dolomite stability investigations : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 7 –13 (2011)More Less
The article discusses the nature of the gravimetric survey as applied and used in dolomite stability investigations on areas underlain by the Chuniespoort Group in South Africa. A short discussion is given on the gravimetric survey procedure along with its uses and alternative methods. Finally, two case studies illustrate the application of the method on a high-density survey grid spacing in comparison with three-dimensional geological modelling based on the lithology and karst weathering horizons of the Chuniespoort Group deduced from rotary percussion borehole data and limited rotary core borehole data. The two different case studies highlight the advantages and limitations of the high-density gravimetric survey.
The first case studies shows that the high-density gravimetric survey can be applied to great effect to sites with a complex, variable profile, provided the grid spacing of the survey is adequate to identify the sub-surface features. Simultaneously, the findings of the second case study illustrate how the method has exactly the same limitations as regular gravimetric surveys if the scale of the grid is not compatible with sub-surface conditions.
Climate change and urban road transport - a South African case study of vulnerability due to sea level rise : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 14 –22 (2011)More Less
The focus of this investigation was the impact of predicted sea level rise on the road transportation network of the eThekwini Municipality, South Africa. The main objective was to identify the areas within the municipality which are most vulnerable to sea level rise and to develop adaptive responses and interventions in order to maintain road functionality. For the identification of the most vulnerable areas a multi-criteria analysis supported by geographical information system modelling was used. Three areas were identified, namely, the Isipingo, Bayhead and the Umgeni mouth areas. Adaptive road responses have been researched by employing a network analysis of each of the areas identified. Parameters modelled were traffic volume changes, travel time and volume to capacity ratio - for the main roads in the areas identified. The adaptive responses required for each area were found to be different, varying from the addition of a lane to changes in signal settings. Overall this study presents a model of how vulnerability and the development of adaptive strategies to sea level rise could be addressed by municipalities.
Validation of international concrete creep prediction models by application to South African concretes : technical paperAuthor G.C. FanourakisSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 23 –30 (2011)More Less
Creep deformation of concrete is often responsible for excessive deflections at service loads which can compromise the performance of a structure. National design codes therefore provide prediction models for the estimation of creep deformation. These models are empirical-based.
This paper assesses the accuracy of six international code type models, when compared with the actual strains measured on a range of South African concretes under laboratory control conditions. The models considered are those contained in AS 3600 (2001), AS 3600 (2009), Eurocode EC 2 (2004), GL (2000), GL (2004) and GZ (1993).
The results indicate that for the range of concretes tested, the GL (2000) model yielded the most accurate predictions, giving the lowest overall coefficient of variation (ωall) of 31,9%. The least accurate method was the AS 3600 (2009) which yielded an overall coefficient of variation (ωall) of 74,7%.
This paper also recommends a new approach to assessing the accuracy of creep models.
Behaviour of steel tubular stub and slender columns filled with concrete using recycled aggregates : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 31 –38 (2011)More Less
This paper is based on a study that was done by utilising construction and demolition debris that had been effectively recycled, in structural members. The steel tubular columns were filled with different types of waste material, as well as recycled aggregate concrete, instead of normal conventional concrete. The results were subsequently analysed. The behaviour of circular and square concrete-filled steel tubular sections (CFSTs) under axial load, in which coarse aggregate had been partially replaced by recycled aggregates, is presented. The effects of steel tube dimensions, shapes and the confinement of concrete are also examined. Measured column strengths are compared with the values predicted by Eurocode 4, Australian Standards and American Codes. Twelve specimens were tested with 20 MPa concrete and steel sections with diameter-to-thickness ratios of 18,5, 25,3 and 36,0. The columns were of two different shapes - a circular-shaped set with diameters of 76 mm and 89 mm, and a square-shaped set with sizes 72 mm and 91 mm. The circular-shaped columns of 76 mm diameter and the square-shaped columns with 72 mm diameter are 900 mm long. The circular columns with a diameter of 89 mm and the square columns of 91 mm diameter are 350 mm long. Eurocode 4 (EC4) gives the best estimation for both conventional and recycled aggregate concrete. However, the American Concrete Institute (ACI) / Australian Standards (AS) equation predicted lower values than measured during the experiments. Hence the ACI/AS equation has been modified by introducing a multiplying factor 'k' to predict good results for columns of L/D < 12. The values of k factor for L/D ratio varying from 4 to 12 are suggested in this study. From the results it has been noted that square columns save 30% of steel when compared with circular columns. It was also observed that the ultimate load of steel tubular columns filled with recycled aggregate concrete is higher than that of conventional concrete and columns filled with recycled aggregate concrete, and can result in a 10% saving in the cost of concrete. This research therefore proposes a solution for effective solid waste management, which will also prove to be cost effective.