Infrastructure Engineering - Theses
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ItemDecision-making under spatial uncertainty( 2005)Errors are inherent to all spatial datasets and give rise to a level of uncertainty in the final product of a geographic information system (GIS). There is growing recognition that the uncertainty associated with spatial information should be represented to users in a comprehensive and unambiguous way. However, the effects on decision-making of such representations have not been thoroughly investigated. Studies from the psychological literature indicate decision-making biases when information is uncertain. This study explores the effects of representing spatial uncertainty, through an examination of how decision-making may be affected by the introduction of thematic uncertainty and an investigation of the effects of different representations of positional uncertainty on decision-making. Two case studies are presented. The first of these considers the effects on decision-making of including thematic uncertainty information within the context of an airport siting decision task. An extremely significant tendency to select a zone for which the thematic classification is known to be of high certainty was observed. The reluctance to select a zone for which the thematic classification is of low certainty was strong enough to sometimes lead to decision-making that can only be described as irrational. The second case study investigates how decision-making may be affected by different representations of positional uncertainty within the context of maritime navigation. The same uncertainty information was presented to participants using four different display methods. Significant differences in their decisions were observed. Strong preferences for certain display methods were also exhibited, with some representations being ranked significantly higher than others. The findings from these preliminary studies demonstrate that the inclusion of uncertainty information does influence decision-making but does not necessarily lead to better decisions. A bias against information of low certainty was observed, sometimes leading to the making of irrational decisions. In addition, the form of uncertainty representation itself may affect decision-making. Further research into the effects on decision-making of representing spatial uncertainty is needed before it can be assumed that the inclusion of such information will lead to more informed decisions being made.
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ItemDuctility of one-way slabs constructed with class L mesh, Grade 500 steel, under support settlement( 2005)This study investigates the impact of new class L Grade 500 Australian steel on the behaviour of suspended reinforced concrete slabs. An experimental program consisting of two one-way full-scale slabs constructed with class L steel was carried out. The key focus of the test program was to examine the response of slabs under imposed support settlements, which could occur for various reasons in the life of a structure. The experimental results were compared with the numerical results obtained by using the computer software prepared by Dr. Rebecca Gravina at The University of Adelaide, SA. Two continuous one-way slabs, with spans more than 4 m and 5 m respectively, constructed with class L steel were tested under imposed support settlement. A typical value of support settlement was used to raise the intermediate support of one test slab and to lower the intermediate support of the other. The results recorded using various techniques were used to establish the load-deflection curves, moment-rotation curves, degree of moment redistribution, failure loads and crack patterns at different load stages during the tests. A comparison of the experimental results with the numerical study carried out by Dr. Rebecca Gravina using software developed in her PhD studies showed a good agreement between the two results. This study showed that the test slabs were able to resist a load higher than the design load, even when subjected to support settlements of a magnitude expected in practice. Also the test slabs developed significant cracking in the spans as well as over the intermediate support regions before failure. The load deflection curves showed little sign of ductility. Moreover, the failure in each case was in a catastrophic manner by fracture of steel in the negative moment region, with no sign of compressive concrete crushing. This study has provided a detailed experimental investigation about the behaviour of class L steel under support settlement effects. However, it is limited to one-way slabs and has used reinforcement provided one steel manufacturer. It can be further extended to two-way slabs and also to class N steel for comparison with class L behaviour.