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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 44, Issue 4, 2002
Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Volume 44, Issue 4, 2002
Volumes & issues
Volume 44, Issue 4, 2002
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 44, pp 2 –7 (2002)More Less
The influence of the beam-to-column joints on the lateral-torsional behaviour of steel frames is investigated. Commonly used connections with various stiffening arrangements are analysed in order to determine their effect on the stability behaviour of the whole structure. Through finite element modelling of portal frames, it is established that a consistent relationship exists between the critical load for lateral-torsional buckling of the frame beams and the joint design. A comparison between the critical loads obtained from the finite-element method, and those derived from the equivalent-member method, leads to a derivation of reliable coefficients that simulate joint-type behaviour and facilitate a simplified and effective analysis of frame beams.
Source: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 44, pp 8 –15 (2002)More Less
Information on the sedimentary processes at East London was obtained to optimise various facets of the required port maintenance dredging, including a redesign of the old (pre-1994) sand traps. Thus, the location and layout of new sand traps were determined so as to intercept the main sources of sediment deposition in the harbour and entrance channel. The optimum dimensions of these sand traps were also determined in terms of theoretical sand trapping efficiency and practical dredging guidelines. These 'new' sand traps were implemented in 1994, leading to a recent investigation of their effectiveness. Bathymetric surveys were compared, contour maps were analysed regarding sediment build-up and erosion, synoptic difference maps indicating patterns of bottom changes were produced and cross-sections through the sand traps were analysed. Dredging data were analysed to determine any noticeable trends and were also linked in general to deviations from the long-term average wave conditions. The present main sand trap was found to be between 80 % and 90 % effective. The design locations, layouts and dimensions of the sand traps are virtually optimal. Recommendations regarding further possible optimisation of sand traps and dredging were also made.
Applicability of stated preference for mode choice studies among less-literate commuters : technical paperSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 44, pp 16 –24 (2002)More Less
There is concern that research methodologies used in developed countries might not always be transferable to developing countries. This concern is prompted by conditions such as multi-culturalism, multi-lingualism, gender issues and literacy levels. Modal choice information can be collected using stated preference or stated choice questionnaires. <p>The hypotheses for the study were the following:<ul> <li>The level of literacy affects the quality of the responses. <li>The quality of response is affected by the complexity of the choice to be made. <li>The quality of responses is affected by the method of presentation. <li>The quality of response declines with the fatigue of the respondents.</ul> <p>The data for the study were collected using a questionnaire whereby respondents were required to select between either two or three alternatives described by either three or five attributes. The 364 respondents who took part in the study were recruited at modal transfer facilities in Mamelodi. In-depth interviews were also conducted with 26 of these respondents at their homes. <p>As a result of the study, the following can be deduced: <ul> <li>Stated preference data can be collected from less-literate respondents provided that the choice tasks are not complex. <li>A high degree of care needs to be taken in training interviewers and during the interviews to ensure that respondents interpret the profiles as hypothetical and do not use their experiential values for the attributes, really apply their minds when making choices / giving responses, and do not provide responses which they consider to be necessary to be polite or appear intelligent. <li>The possibility that the mode choice might be made using non-compensatory rather than compensatory decision rules needs to be investigated further. <li>The qualitative approach to the analysis appears to provide conclusions that are not always consistent with the statistical analysis approach. The reasons for these discrepancies need to be researched further. <li>The usefulness of in-depth interviews to provide a confidence to quantitative and complex surveys in developing countries needs to be investigated further.
Author K.D. HoganSource: Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese 44, pp 25 –28 (2002)More Less
In March 2000, 13 people died in a tubing accident on the Storms River. The reasons given in the media for the accident were 'freak flood' and 'flash flood in side kloof', which were considered to be acts of God. A study of the hydrology of this river and the surrounding rivers found this to be untrue. The rainfall records indicated significant widespread rainfall over the whole Tsitsikamma area during the accident period. The historic rainfall records indicated that rainfall of the magnitude experienced over the accident period had a recurrence interval of three times a year on average. The water level records from three nearby gauging stations showed a good correlation between them and are a good indication of the water level in the Storms River during the accident period. The historic records of these gauges indicated a flood of the magnitude experienced during the accident was likely to occur two to three times a year on average. An understanding of the hydrology of the river may have resulted in the river guides making a different choice when confronted with the flood in the major tributary, saving many lives.