Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

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Uptake of geothermal heat pump (GSHP) systems has been slow in some parts of the world due to the unpredictable operational performance, large installation space requirement and high installation costs. Therefore, design modification was searched in order to improve the feasibility. With regard to relatively small impact of the construction costs, efficient thermal energy collection was targeted in horizontal ground-loop systems with shallow underground construction. The research started with a sensitivity analysis of the underground heat collection system using computational fluid dynamics (CFD). The results indicated essential design parameters to enhance the performance. Strategies to improve one of the parameters, thermal conductivity of soil surrounding the heat exchanger, were investigated through lab experiments. Subsequently, further design optimisation with the CFD intended to select the most competitive modified design against the existing design. It was discovered that an indication to achieve economic and practical modifications for efficient heat collection was to increase the moisture content of sub-soil up to the optimum moisture content (OMC). Annual operation analysis with the CFD disclosed that additional costs for even simple design modifications could easily worsen the payback period. Consequently, solutions to improve the performance of the GSHP within reasonable payback period were proposed.

Building Information Modeling (BIM) has been in use in the Hong Kong Architecture, Engineering and Construction (AEC) industry as an Information and Communication Technology (ICT) tool for more than a decade. However, the increasing usage and rapid development in both the AEC industry and academia point to the potential multiple applications, impacts and much broader potential benefits that may be generated from BIM implementation. The current frequently used BIM applications have advanced the project performances levels and consequential benefits of relevant stakeholders in different dimensions. However, BIM development in the Hong Kong industry has not been smooth. Attention has been diverted from potential benefits to the barriers and constraints that retard BIM implementation. This has in turn limited the applications, hence not convincing industry participants of their potential benefits in quantitative terms. Furthermore, conflicts between BIM implementation and the existing project processes also retard the smooth development of BIM. A higher level of collaborative working is required for deriving more benefits from BIM. This research aims to develop possible feasible solutions to reduce the conflicts/barriers in BIM implementation and advance current BIM implementation towards more collaborative and integrated working arrangements (IWAs), with expected broader potential benefits in the context of the Hong Kong industry. IWAs in this research refer to: a) organization structures, b) information exchange mechanisms, and c) project processes. An inter-locking set of research methods were applied in this study to achieve the research goal. Literature reviews were conducted to extract and illustrate the basic concepts in BIM and lay the foundation for proposal development. Semi-structured interviews and a questionnaire survey were conducted to explore BIM implementation scenarios in the Hong Kong AEC industry. Two case studies helped to map out BIM implementation processes in real projects in Hong Kong. Finally, a focus group meeting was held to discuss, validate and improve the relevant research findings and improvement proposals. The main outcomes of this research are the proposed short term IWAs and long term IWAs for optimizing overall potential benefits of BIM implementation. The proposed short term IWAs consist of specific measures for participants to address the barriers and conflicts in BIM implementation within existing project processes. The proposed long term IWAs are based on a conceptual framework and processes to build an integrated working environment for BIM. The outcomes of this research can help industry practitioners to overcome current barriers and derive more benefits from BIM by developing specific measures targeting the current scenarios, as well as provide possible directions for moving further forward in the long term. The research outcomes also offer relevant contributions to knowledge by proposing fresh concepts and approaches to creating and developing collaborative working environment for BIM implementation based on relevant principles and guidelines that are in turn derived from Relational Contracting (RC) frameworks. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

Residential buildings under co-ownership are properties governed by mixed systems of communal and individual property rights. Their management demands a high level of organized cooperation and coordination among them. However, owners’ collective actions are never straightforward owing to their temptation to free ride. Without owners’ collective actions, management works can be delayed or even cancelled, which results in deteriorating building conditions. With the increasing number of people living in co-owned residential buildings, whether they can overcome collective action problems and effectively manage their properties becomes important to long-term management of building stocks. Therefore, this study aims to assess management performance of co-owned residential buildings and to explore the variations of the management performance from a collective action perspective. A rigorous tool for assessing management performance of co-owned residential buildings was developed in this study. The tool consisted of a hierarchy of key performance indicators which evaluate the capability of an owners’ group to make collective decisions, enforce management rules, and monitor its buildings’ condition. The application of the tool on a co-owned residential building generates a performance profile representing its management performance. The proposed tool was used to assess the management performance of 74 sampled buildings in Hong Kong. The survey data was collected from the sampled buildings through desk studies, face-to-face interviews, questionnaires by post, and on- site inspections. Multiple regression analyses were applied to investigate the effects of the exogenous factors on building management performance. The empirical results showed that large-size owners groups were more likely to perform well in managing their properties. Homogeneous owners groups were associated with a greater likelihood to achieve high management performance. More importantly, the empirical results revealed that the owners group of a co-owned residential building were more likely obtain high performance in managing the communal properties under the following circumstances: 1) well-defined boundaries of the communal properties; 2) a fair distribution of their rights and responsibilities to management; 3) a presence of effective mechanism to regulate their use of the communal properties; and 4) a way to rapidly resolve their disputes over management. The major contribution of this study is to the field of building management. The proposed tool in this study can used by owners, property managers, investors, and policy-makers to access to management information on co-owned residential buildings, which helps them make better decisions on buildings. In addition, findings of this study provided an explanation of the variations in building management performance, which has great implications for government policies that aim to encourage owners to cooperate in management of their properties. / published_or_final_version / Real Estate and Construction / Doctoral / Doctor of Philosophy

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Self-consolidating concrete (SCC) is an advanced type of concrete that can flow under its own mass without vibration, pass through intricate geometrical configurations, and resist segregation. SCC constituent materials and mixture proportions must be properly selected to achieve these flow properties. The effects of any changes in materials or mixture proportions on hardened concrete performance must be considered in evaluating SCC. A research project was conducted to investigate the role of aggregates in SCC. The objectives of this research were to evaluate the effects of aggregate characteristics and mixture proportions on the workability and hardened properties of SCC, to identify favorable aggregate characteristics for SCC, and to develop guidelines for proportioning SCC with any set of aggregates. The research indicated that although SCC can be proportioned with a wide range of aggregates, the selection of favorable aggregates can significantly enhance the economy and performance of SCC. The effects of aggregate grading; maximum size; shape, angularity, and texture; apparent clay content; and packing density were evaluated. The main effect of aggregates larger than approximately 75 [mu]m was found to be on the minimum required paste volume for achieving SCC workability. It was found that dust-of fracture microfines, defined as mineral material finer than approximately 75 [mu]m produced during the crushing of aggregates, could be an economical choice to comprise part of the paste volume. Based on the results of this research, a mixture proportioning procedure for SCC was developed. The procedure is based on a consistent, rheology-based framework and was designed and written to be accessible and comprehensible for routine use. In the procedure, SCC is represented as a suspension of aggregates in paste. Aggregates are selected on the basis of grading, maximum size, and shape and angularity. The paste volume is set based on the aggregate characteristics in order to achieve workability requirements. The paste composition is established to achieve workability and hardened property requirements. / text