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- Volume 53, Issue 1, 2011
Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Volume 53, Issue 1, 2011
Volumes & issues
Volume 53, Issue 1, 2011
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 2 –11 (2011)More Less
I read this excellent paper with great interest since I have been consulted in a couple of instances where flat plate slabs, containing spherical void formers, had experienced deflections far in excess of their designers' expectations. These slabs had been constructed in arid areas with very low average relative humidity. There may be several factors that contribute to greater than anticipated long-term deflections
Positioning technology development in the South African construction industry : a technology foresight study : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 2 –8 (2011)More Less
Internationally infrastructure is ageing rapidly and there is increased utilisation of infrastructure due to urbanisation and globalisation. Significant amounts are invested globally to address this issue, although funding fluctuates from year to year. One response to this situation is to position the construction industry with advanced technological solutions. However, the construction industry is renowned for low levels of innovation and the South African government has also underfunded research into infrastructure. There is a need to stimulate innovation in the construction industry to develop the uniquely South African technological solutions required to provide and maintain economic and social infrastructure. An investment in construction innovation should be based on a review of the current state of construction technology and the industry and an analysis of the drivers and trends that will shape the future construction industry landscape. Technology foresight studies are recognised as one way to determine the future factors that will influence a specific economic sector. This article describes a new approach to conducting a technology foresight study within the South African construction industry. The methodology, as well as initial results from it, is reported. A review is provided of the current state of the construction industry and its potential drivers and trends. Future work will include scenario development and the development of pathways and interventions to take the industry forward from its current position to a desired future state.
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 9 –21 (2011)More Less
This paper considers aspects related to the nature of dolomite, sinkholes, the risk classification of dolomitic land, as well as factors affecting the failure of pipelines in dolomitic areas. The information and data presented are used to derive equations that may be used to predict the probability of failure of steel pipelines in dolomitic areas subject to sinkhole formation. Consideration is also given to other factors that may influence the failure of pipelines in dolomitic areas.
Response of a full-scale dry-stack masonry structure subject to experimentally applied earthquake loading : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 22 –32 (2011)More Less
This paper presents the response of a full-scale dry-stack masonry structure subject to earthquake loads. The following earthquakes were applied to the base of the structure: (a) North Ridge, (b) Llolleo, (c) El Centro and (d) Llolleo for the second time. The earthquake displacement signals had to be filtered by removing the slow-varying frequency components so that the available servo-hydraulic test machine could be used. The filtering produced acceptably low error when comparing the applied histories with the real earthquake histories. A 4 x 4 m structure was constructed on a 1° of freedom shake table out of mortarless interlocking bricks with minimum reinforcement. A 2 560 kg mass was superimposed on the structure to model the roof. The test structure was instrumented with accelerometers and LVDTs. The results showed that the simulated Llolleo earthquakes caused the most damage. This damage was minor: several bricks cracked, other bricks shifted, vertical gaps opened up between the bricks, and the skim plaster spalled in several places. The Llolleo earthquake damage was estimated to be Grade 2 on the European Macroseismic Scale (EMS). During the earthquake simulations the walls deflected up to 42 mm. However, the maximum permanent deformation recorded due to bricks shifting was only 4,6 mm - a small fraction of the wall thickness. Although the peak ground acceleration (PGA) was 0,7 g, the maximum acceleration experienced by the structure at a door opening was 3,4 g. The tests were concluded by applying two harmonic base excitations. The first 5 Hz harmonic test, which corresponded to the undamaged structure's resonant frequency, produced less damage than the Llolleo earthquake. The second 15 s, 3 Hz sinusoidal base motion, which corresponded to the damaged structure's resonant frequency, caused major damage (EMS Grade 4). Despite major cracks in two walls forming the characteristic "X" failure, the structure continued to support the roof mass. Video analysis clearly demonstrated that dry stacking can result in large brick movements when the base is excited.
Reducing crime in South Africa by enforcing traffic laws - a 'broken windscreen' approach : technical paperAuthor P.C. BezuidenhoutSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 33 –38 (2011)More Less
The situation on our country's roads has gradually deteriorated to the point where traffic laws are being broken at various levels on a daily basis with few or no consequences for the offenders. Something needs to be done to turn the current situation around and prevent further deterioration. A 'broken windscreen' approach is introduced as a possible solution, with the emphasis on traffic enforcement, and it may also contribute to the combating of crime in South Africa.
The 'broken windows' theory and its implementation in New York City is briefly discussed to explain the concept. The difference between the broken windows and zero tolerance approaches is discussed from a local perspective, and the broken windows theory is then linked to the traffic situation in South Africa. The Safe Streets 1997 Program, which was based on the broken windows theory and implemented in Albuquerque, achieved a varying degree of success, and is discussed in this article. A critical link is then highlighted between traffic offences and more serious crime from the Safe Streets 1997 Program and also research conducted by the London Department of Transport (Knox & Silcock 2003). A broken windscreen approach is recommended in the light of the examples and data discussed.
Effectiveness of the fineness of two South African Portland cements for controlling early-age temperature development in concrete : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 39 –45 (2011)More Less
Temperature gradients due to heat of hydration of cement can cause cracking and present serious structural and serviceability concerns in concrete structures. Engineers use a wide range of strategies to limit the potential for such cracking, mainly by minimising the maximum temperature in the concrete. This paper considers the possibility of using more coarsely ground cement as one of the strategies for reducing the maximum concrete temperature. Two cement clinkers were used to produce cements with five different levels of fineness. These ten cements were then used to make concretes which were tested in an adiabatic calorimeter to determine the heat evolution characteristics. The measured results were then used in a computational model to calculate the temperature profiles likely to occur in two types of concrete elements. The results indicate that the effect of increasing fineness on the total amount of heat released during hydration is dependent on the mineralogy and crystal composition of the cement clinker. Also, the use of coarse-ground cement as a means of reducing the maximum temperature in concrete is more effective in the case of concrete elements with high cement content but of moderate dimensions. In sections of larger dimension, coarse-ground cements show lower levels of temperature reduction but also lower thermal gradients.
Correlating Standard Penetration Test and Dynamic Probe Super Heavy penetration resistance values in sandy soils : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 46 –54 (2011)More Less
This paper presents a statistical method used to develop an empirical equivalence between the Standard Penetration Test (SPT) and the Dynamic Probe Super Heavy (DPSH) in sandy material. Penetration resistance values from the two tests are often taken as equivalent for design purposes, as the same drive energy is used in both. SPT and DPSH resistance values from different geological depositional and weathering environments were examined. The data came from the following areas across southern Africa: Matola in Mozambique, Gope in Botswana, Umdloti and Cape Town in South Africa, and Illha de Luanda in Angola. It was apparent that energy losses were greater in the DPSH test than in the SPT, leading to higher resistance values in the former. The SPT is carried out within a borehole, whereas the DPSH is continuously driven into the soil. The dynamic force applied to the DPSH rods causes soil to fill the small air annulus around the rods, exerting a frictional resistance. The different geological settings of the test sites revealed that, although different factors cause the friction, the equivalence varied in a similar manner. Hence a single correlation formula is suggested to determine equivalent SPT values from raw DPSH resistance values.
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53, pp 55 –60 (2011)More Less
This paper considers the probability of power supply failures at bulk water distribution pump stations. Electrical power supply is important within the bulk water distribution environment, particularly when pumping is required. Reliability of power supply is commonly expressed by means of indices, such as amongst others, the SAIDI and SAIFI indices as defined by the Institute of Electrical and Electronics Engineering (IEEE). These indices are used to calculate the probability of failure associated with power supply. Data was obtained from a number of sources and used to benchmark the reliability of South African power supply against that of other countries. The reliability of power supply from seven South African Water Board (Rand Water) pump stations is also analysed. Limited data seems to be available that allows one to quantify the reliability of pump systems, taking into account the reliability of the various system components.
Spherical void formers in concrete slabs : technical paper, Journal of the South African Institution of Civil Engineering, 52 (2) 2010 : pp. 2-11 : errataSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 53 (2011)More Less