The paper briefly summarizes significant trends in structural research and their probable influence on design principles and procedures. The development of collapse load methods of design, studies in composite action, and the application of statistical principles to the assessment of safety margins are discussed.
Die beton ontwerp van 'n paar van die hoogste kantoorgeooue, noemenswaardige skulpdakke en belangrike graanskure en silos in Suid-Afrika, word met 'n kort oorsig van die belangrikste ontwikkelings en neigings, deur die Skrywer bespreek.
The engineering materials to which the paper refers are briefly defined and various classifications mentioned. Developments concerning some interesting and important materials are discussed, with particular reference to probable future developments. Large-scale production of engineering materials in South Africa developed recently ,and thus the study of production, use and quality control is very necessary. New qualities in materials and methods of using them, and above all new approaches to engineering problems, are demanded. These developments will require a progressive approach on the part of both engineers and the industry which applies their knowledge. Improved educational and research facilities will be required.
High-magnesia slags ground to various finenesses were added at the mixer to yield concretes having standard aggregate to slag plus Portland cement, and water to slag plus Portland cement ratios. Cube crushing strength, modulus of rupture, elastic modulus, shrinkage and creep tests were carried out to determine the effect of incorporating various proportions of these materials. Concrete of good quality was obtained with slag to slag plus Portland cement ratios of up to 0.6 with slags ground to a specific surface of 4,600 cm2/gm as determined by the Blaine method.
The paper refers first to the developments in soil stabilisation procedures like the use of chemical additives in cement stabilisation and the use of resins in soil waterproofing. The problems of providing good quality crushed stone for bituminous surfacing work and the possibilities of drawing up a national specification for crushed stone are then discussed. The paper ends with reference to trends in bituminous binders - the use of bitumens from Middle East sources with their attendant problems, rubberised bitumens, and the recently developed cationic emulsions.
Chemical and physical techniques for the development and evaluation of building materials are briefly reviewed in relation to their significance, selection, interpretation, application, diversity and effectiveness, The principles, characteristics and interpretation of accelerated performance tests, dimensional change studies and high temperature techniques are discussed in general terms with some examples of their application to specific problems. Current and probable future trends envisaged are increases in extent and complexity of research and test methods, their more judicious and rational application, a demand for skilled and specialised manpower, new procedures to develop and assess materials for special requirements arising from the application of advances in science, and a greater need for fundamental research,
The paper prognosticates, in the light of current developments, what South African Railways main line track standards of the future are likely to be and what methods will be used for maintaining such tracks. The disadvantages of the various components of existing permanent way are discussed and indications given as to how they are being eliminated. The necessity for mechanising track maintenance is emphasized and an attempt made to prophesy how far such mechanisation will be implemented.
The progress made in tunnelling on the South African Railways during the past eighty years, both in conception and execution, are reviewed. Modern equipment and methods of construction which have made the progress, particularly over the last few years, possible are briefly descriptionbed, followed by a forecast of future trends.
The basic problems in the use of long welded rails are discussed. The. stability of the track is of prime importance and maintenance must be on a high order to maintain this stability. The use of long welded rails results in considerable economies in maintenance and extends the life of the rail in the track.
The ways and works of rail transport are costly investments that cannot lightly be radically altered or discarded. There is an understandable tendency to modify and add to layouts until congestion and an altered method of working seriously impair their efficiency. For several years few railways have been able to meet all demands on them and wisdom as well as necessity has dictated a measure of patchwork. Planning has had to be accompanied by improvisation. Certain basic principles are quoted to ensure that each is accorded its rightful place. The principal fields in which improvements are possible are limited in number, although the works to provide the improvements may be large and varied. Delay is the commonest symptom of deficiencies which must be divided into their components. The evidence that deficiencies exist, determination of their nature and extent, and the means of overcoming them are discussed.
This paper descriptionbes the construction of the Swaziland Railway, the events leading up to the realisation of the project, together with its design and economics. The project is unusual for modern times in that the territory in which the line was built had no existing railway or railway background. The overall organisation is detailed, covering the functions of the Railway Board, the Consulting Engineers and the various contractors.