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- Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese
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- Volume 43, Issue 1, 2001
Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Volume 43, Issue 1, 2001
Volumes & issues
Volume 43, Issue 1, 2001
Author N.J. VermeulenSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 43, pp 2 –12 (2001)More Less
The piezocone (CPTU) has become one of the most popular site characterisation tools used by geotechnical engineers. Although limited by the hardness of the profile to be penetrated, the piezocone is unrivalled in its ability to define the in-situ seepage regime and is the only available routine technique, other than continuous sampling, that provides a continuous profile of soil stratification below the water table. In addition, piezocone data can be analysed empirically or theoretically to give soil parameters and direct correlations for geotechnical design. This paper demonstrates a numerical procedure for analysing piezocone data for the purposes of stratification and classification. The procedure employs polynomial curve fitting techniques to identify the principal layers of the profile, which are then refined and classified according to the classification chart proposed by Jones and Rust (1982). The procedure is evaluated against a field profile from continuous sampling and is shown to give an accurate representation of sub-surface stratigraphy with the advantages of speed, cost and operator independence.
Author A.R. KempSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 43, pp 13 –18 (2001)More Less
Premature failures have been observed to occur in single-bolt lap joints in bearing, particularly where the connected plates are relatively thin and washers are not provided. A series of 28 tests conducted under the author's supervision, as well as 12 tests conducted in Australia, are described covering a range of bolt diameters, plate thicknesses and washer arrangements. In many of these specimens the mode of bearing failure involves rotation and pull-through of the bolt associated with eccentricity of the lap joint. The bearing capacity of many of these joints was found to be well below the strength predicted for conventional bearing failure in the Canadian/South African design code, although within the range predicted in the clause for screws or hollow rivets in lap joints. Revised design criteria are proposed in which the presence of standard or large washers is important in achieving adequate bearing resistance.
The effect of global and partial factors of safety in bearing capacity calculations : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 43, pp 19 –23 (2001)More Less
At first sight the change from a global safety factor to partial safety factors seems quite sensible and straightforward. This may well be so where the analyses to be used show a linear relationship between the parameters to be factored and the final result. However, in geotechnical analyses, this is frequently not the case and the application of partial safety factors to c' and f' will have further effects on other factors such as earth pressure coefficients and bearing capacity factors. This study has looked at one category of geotechnical analyses, namely bearing capacity analyses and has shown that the overall margin of safety, comparing actions with resistances, when using partial safety factors varies from about 1, 5 to about 4. While the use of partial safety factors can be argued to be better than the use of a single global safety factor, this large variation in overall margins of safety must be a cause for concern, given that the 'traditional' use of a global safety factor of about 3 has proved adequate in limiting failures to a frequency acceptable to society.
Author M. GohnertSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 43, pp 24 –28 (2001)More Less
A recent amendment to the horizontal shear clause of SABS 0100 requires that the average horizontal shear stress is distributed according to the shape of the shear diagram. This change effectively doubled the design shear stress in simply supported members subjected to a uniformly distributed load and therefore threatened the economy of rib and block slabs. In response, a study into the specifications of international codes of practice was undertaken and compared with the South African code. An extensive experimental program was also conducted to determine the shear capacity along the contact interface of the in-situ concrete and precast ribs. It was found that the South African specification (as amended) is consistent with other international codes. It was also found that the surface roughness has a profound influence on the horizontal shear capacity and is a better indicator of shear strength than the strength of the in-situ concrete.
Sanitation, public health and the environment : looking beyond current technologies : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 43, pp 29 –33 (2001)More Less
Where there are poor or non-existent sanitation facilities, human excreta are spread throughout the environment and people, soils and bodies of water are negatively affected. With rapid population growth, especially in urban areas, the situation cannot improve unless there is a significant change in the manner in which sanitation systems are chosen, designed and implemented. <p>While waterborne sanitation systems have been widely successful in controlling the transmission of excreta-related diseases in most cities of industrialised countries, they have also created severe damage to ecosystems and natural water resources where the wastewater is inadequately treated. VIP toilets may also not be suited to densely populated urban areas, due to the increased risk of environmental pollution. Other systems should rather be employed, and they should preferably operate well without piped water. <p>The paper describes urine diversion sanitation systems, which have been used successfully in many developing countries, including South Africa. This sanitation technology is suggested as an additional means of combating the health and environmental problems caused by inadequate sanitation in many areas of the country.
Guidelines for incorporation of vehicle-pavement interaction effects in pavement design : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 43, pp 34 –39 (2001)More Less
Vehicle-pavement interaction defines the relationship between a vehicle on a pavement, and the pavement. Pavement unevenness causes vehicles to generate dynamic tyre loads. The pavement roughness level, vehicle type, vehicle components, and vehicle speed affect these tyre loads. Application of these loads to the pavement cause transient pavement responses that differ from static pavement response to static loads. Incorporation of these dynamic tyre loads into pavement design is a complicated mathematical process. A guideline based on existing pavement analysis procedures was developed to simplify this process. In this paper a short background to vehicle-pavement interaction is provided, followed by the guideline and an example of applying the guideline. The objective of the paper is to expose the pavement engineer to a practical guideline for incorporation of vehicle-pavement interaction issues into pavement design. Application of the guidelines indicated that use of dynamic tyre load populations rather than equivalent static loads in pavement response analyses can cause significantly different pavement responses.