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published_or_final_version / Public Administration / Master / Master of Public Administration

M.Phil. / In an ever - increasing competitive business world it is essential to optimise the replacement of expensive mining equipment. The decisions regarding the replacement of assets used in a coal mine are usually based on life cycle costing models. Financial methods such as Net Present Value, Internal Rate of Return or Payback are applied to determine the feasibility of replacement of the asset. Whereas these methods and other models such as life cycle costing, challenger / defender and the Non-Homogeneous Poisson Process models can be applied in most cases, it is deemed to be insufficient as the sole decision making tool for the replacement of mining equipment. The development of another tool to assist in the decision making process is required for specific use by the engineer to be used in conjunction with the traditional financial models. Key performance indicators are used extensively in the mining industry to manage the performance of equipment and are deemed to be essential components in achieving the organisation's objectives. There are certain limitations when using only the traditional financial life cycle costing methods when viewed from the engineer's perspective, since they do not directly incorporate the level of the maintenance function and the performance effectiveness of the asset. The engineer usually requires more insight into the performance of the asset to assess the feasibility of replacement, hence the need for an additional tool that incorporates these key performance indicators. In most cases there are relationships between the various key performance indicators themselves as well as between them and the operating and maintenance cost of the asset. The key performance indicators used are availability, reliability (mean time to failure), maintainability (mean time to repair) and the operability (tons per direct operating hour). There are certain factors that may lead to the excessive operating and maintenance cost of an asset, especially if there is no investigation into the reasons for the excessive cost. Examples are sub-standard maintenance practices and an insufficient level of service from suppliers. Both are issues that can be resolved with a consequent decrease in the cost of ownership of the asset. Cost as the only indicator of the feasibility of replacement may therefore not be a true reflection of the real status of the performance of the asset. Weighting factors are used to allocate values to the key performance indicators in terms of their contribution towards achieving the organisational objectives. The equipment effectiveness is derived from these values to give an indication of how well the equipment is performing against predetermined benchmarks. This dissertation attempts tb find a solution to the problem through the use of the key performance indicators in addition to the existing models that focus on the financial aspect in order to provide a more accurate assessment of the replacement requirement of an asset in an opencast coal mine.

M.Phil. / In the modern world maintenance organisations are exposed to rapid changes in equipment complexity and the maintenance thereof. Maintenance people have to adopt completely new ways of thinking and managing. If organisations and their management do not adapt to these changes and challenges they are destined to oblivion. Moubray (1991:1) states that: "Managers everywhere are looking for a new approach in maintenance. They want to avoid the false starts and dead ends which always accompany major upheavals. Instead they seek a strategic framework which synthesizes the new developments into a coherent pattern, so that they can evaluate them sensibly and apply those likely to be of most value to them and their companies" One of the viable alternative business strategies and maintenance approaches in dealing with equipment complexity and hence the management thereof, is by means of maintenance outsourcing and contract setting. If done correctly it reduces the risk of organisations and increases flexibility. During outsourcing initiatives organisations will look for benefits such as improvement of its profit margins by means of inventory reductions, improved reliability, maintenance efficiency and expert skills maintaining their assets. Coetzee (1997:24) explain that the task of the maintenance function is "to support the production process with adequate levels of availability, reliability and operability at an acceptable cost". The same principles apply in adherence to the maintenance contracts where the Original Equipment Manufacturer (OEM) or contractor also needs to support the customer with the adequate levels of availability, reliability and operability at defined costs. This can only be achieved by quality maintenance; "the right level of maintenance performed at the right time to the right equipment by workmen able and willing to deliver quality workmanship and using correct task specifications" (Coetzee, 2000a). The method used in maintenance outsourcing negotiation and binding agreements between the organisation and the contractor is a Repair and Olivier-2008 Department of Mechanical and Manufacturing Engineering - UJ Maintenance Contract; commonly known as R+M or MARC contracts. Essentially a Repair and Maintenance contract is the outsourcing of a long term Service Level Agreement (SLA) or maintenance project, normally to the OEM, or its authorised service organisation. "A maintenance and repair contract is a contractual agreement between the OEM (original equipment manufacturer), or contractor, and the equipment owner or user, where the OEM or contractor carries out all maintenance and repair activities at a guaranteed rate per hour" (Lugtigheid, et al. 2007). When organisations adapt outsourcing as a business strategy, it creates a framework of uncertainty and risk to Original Equipment Manufactures and/or maintenance contractors who has to perform the maintenance services. The focus of manufacturing and selling is thus disrupted by the challenge of the unknown playgrounds of competitiveness

With the rise in interest in the field of grid and cloud computing, it is becoming increasingly necessary for the grid to be easily maintainable. This maintenance of the grid and grid services can be made easier by using an automated system to monitor and repair the grid as necessary. We propose a novel system to perform automated monitoring and repair of grid systems. To the best of our knowledge, no such systems exist. The results show that certain faults can be easily detected and repaired. / TeX / Adobe Acrobat 9.51 Paper Capture Plug-in

No description available.

A number of older bridges built before the 1970’s were constructed with floor systems consisting of a non-composite concrete slab over steel girders. Many of these bridges do not satisfy current load requirements and may require replacement or strengthening. A potentially economical means of strengthening these floor systems is to connect the existing concrete slab and steel girders to permit the development of composite action. This dissertation describes a research program investigating methods to develop composite action in existing non-composite floor systems by the use of postinstalled shear connectors. Three types of post-installed shear connection methods were investigated. These methods are referred to as the double-nut bolt, the high tension friction grip bolt, and the adhesive anchor. These post-installed shear connectors were tested under static and fatigue loading, and design equations for ultimate strength and fatigue strength were developed. These post-installed shear connectors showed significantly higher fatigue strength than conventional welded shear studs widely used for new construction. The superior fatigue strength of these post-installed shear connectors enables strengthening of existing bridge girders using partial composite design, thereby requiring significantly fewer shear connectors than possible with conventional welded shear studs. Five full-scale non-composite beams were constructed and four of these were retrofitted with post-installed shear connectors and tested under static load. The retrofitted composite beams were designed as partially composite with a 30-percent shear connection ratio. A non-composite beam was also tested as a baseline specimen. Test results of the full-scale composite beams showed that the strength and stiffness of existing non-composite bridge girders can be increased significantly. Further, excellent ductility of the strengthened partially composite girders was achieved by placing the postinstalled shear connectors near zero moment regions to reduce slip at the steel-concrete interface. Parametric studies using the finite element program ABAQUS were also conducted to investigate the effects of beam depth, span length, and shear connection ratio on the system behavior of strengthened partially composite beams. The studies showed that current simplified design approaches commonly used for partially composite beams in buildings provide good predictions of the strength and stiffness of partially composite bridge girders constructed using post-installed shear connectors. / text

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Call number: LD2668 .T4 1978 W44 / Master of Science

The main objective of this research is to estimate the sizes of riprap (loose rock) on highway or railroad embankments approaching bridges, that would be stable in major floods. Two assumptions about the flow direction were made: one horizontal to the bridge abutment and the other normal to the projection of the bridge abutment. Three dynamic conditions of stability of riprap were observed and classified as shaking, some movement, and large movement (washing out). Shaking is the most conservative criteria for design because it indicates more stability than is necessary, requires larger rock, and is less cost efficient. Some movement suggests a conservative design criteria and is the most desirable because it requires smaller riprap and is therefore less expensive. Large movement or washing out means the least stable condition; it may leave the structure as well as human lives exposed to danger.