Scielo RSS <![CDATA[Journal of the South African Institution of Civil Engineering]]> http://www.scielo.org.za/rss.php?pid=1021-201920190001&lang= vol. 61 num. 1 lang. <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>MicroCT-based bulk density measurement method for soils</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192019000100001&lng=&nrm=iso&tlng= High-resolution micro-computed tomography (microCT) is a method growing rapidly in popularity and has been applied to various soil studies with great success, especially for 3D characterisation of pore spaces or mineral distributions. However, microCT is not typically used for soil bulk density measurements, probably due to relatively simple and fast alternatives. Besides the complex process of image analysis from microCT scans, the method is also limited in resolution, which can result in incorrect total porosity estimation. This is especially true for granular materials, such as soils with small pore spaces between particles. In this work we demonstrate a different, yet very simple methodology for microCT adapted to overcome these limitations by using only volumetric measurements of the samples, and not segmentation of pore spaces or density calibrations. This method allows accurate bulk density determination for soil clods and cores. The method is faster than tradition methods, and it allows for additional analyses, such as surface area, macro-porosity, connected pore network and macro-particle shape analysis. The method is tested and directly compared for the same samples to the traditional waxing Archimedes method, with good correlation. The microCT scans of waxed samples also indicate sources of possible error in the waxing Archimedes method by visualising trapped air and wax penetration into open pore spaces. The method is then applied to cores and local bulk density measurements, and their variability down the cores is demonstrated, which can be very useful in complex soil profiles. The method is robust in varying resolution and image blur as it makes use only of volumetric measurements of the entire sample, not image grey-value calibration or segmentation of pore spaces. <![CDATA[<b>A research study of the impact testing of stainless steel reinforced concrete piers with different reinforcement ratios</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192019000100002&lng=&nrm=iso&tlng= In this study, a domestically advanced super-high heavy-hammer impact test machine system was used to perform horizontal impact tests on five 1/5 reduced scale models of stainless steel reinforced concrete piers with different ratios of longitudinal reinforcements. The impact velocity and force of the ship model, displacement of the specimen measurement point, reinforcement strain, cracks, and ultrasonic velocity data during the impact process were collected and analysed. The results showed that, under these test conditions, the increase of reinforcement ratio can improve the lateral impact resistance of reinforced concrete piers to a certain extent. <![CDATA[<b>Characterising the segregation of self-consolidating concrete using ultrasonic pulse velocity</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192019000100003&lng=&nrm=iso&tlng= Segregation is the unintentional separation of the fresh components of concrete or mortar, which can have negative impacts on the mechanical, transport and durability properties of the cured product. The problem is acute in self-consolidating concrete (SCC), because of its high fluidity level. To help evaluate segregation, this paper investigates the potential of using ultrasonic pulse velocity (UPV) as a means to identify and characterise segregation in traditional and SCC mixes. Fourteen different concrete mixes were tested using standard techniques (sieve and column) in comparison with the UPV-based test proposed herein. Six of the 14 concrete mixtures were stable, as indicated by having sieve segregation indices lower than 15% and segregation resistances (f) higher than 95%. These six stable samples displayed UPV segregation index values (f u) approaching 100%. The remaining samples were found to be unstable concretes with sieve segregation index values higher than 15% and resistance index values lower than 65%. These concretes could also be clearly identified as unstable by a UPV segregation index lower than 80%. The UPV method provides a clean, quick and easy nondestructive alternative for testing segregation of both fresh and hardened concrete. <![CDATA[<b>Eastern Cape employers' views on the strengths and weaknesses of civil engineering diplomates entering the workplace</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192019000100004&lng=&nrm=iso&tlng= Employer perceptions in the Eastern Cape Province of South Africa have been reviewed to determine whether universities within the province produce civil engineering diplomates who meet industry's expectations. A questionnaire, which contained 30 questions (closed and open-ended), was designed to allow employers to assess the strengths and weaknesses of the students' academic training. These were distributed to a purposive sample of 546 employers using a web-based survey approach. Sixty-five percent of the targeted population who opened the invitations populated the questionnaire. The survey yielded an overall response rate of 28% (based on invitations sent). The data gathered was statistically analysed. The results indicate that employers deem the competencies of diplomates to be "neither high nor low", when employers are considered as a single, comprehensive cohort. Within employer representative subgroups statistically significant differences were, however, observed. Of the competencies assessed, "individual and teamwork ability" received the highest and "engineering design ability" the lowest rating. Overall, the results indicate that employers within the Eastern Cape Province are reasonably satisfied with the competencies of newly qualified diplomates, but point to the need for the strengthening of "engineering design ability", "professional and technical communication ability" and "problem-solving ability" competencies within the diploma programme curriculum. <![CDATA[<b>The application of restructuring of knowledge in civil engineering</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192019000100005&lng=&nrm=iso&tlng= In this paper, it is shown how knowledge theories and knowledge acquisition techniques are integrated by contextualisation to lead to the drawing of concept maps that can be used in civil engineering design, and to analyse and record specific experience. The concept maps form part of concept-based ontologies that are analysed to identify problems and constraints. Solutions to these problems and constraints create new knowledge and can be reported and linked to the world-wide-web. This linkage is made possible by utilising the Top-Level-Ontologies or Upper-Level-Ontologies to link to existing or new ontologies on the world-wide-web. The logic base acts as a procedure to lead and integrate all the above-mentioned aspects into three modules. These modules of the logic base are described and simple examples are given of how the logic base functions. The logic base is a technique to bring knowledge closer to the practising engineer, and facilitates thinking processes that will greatly assist in systematising knowledge, the analysis thereof and making it accessible on the word-wide-web.