Thesis (M. Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 82-85).

Thesis (M. Sc.)--University of Hong Kong, 2000. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 265-274). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Hong Kong, 1988.

Thesis (M.B.A.)--University of Hong Kong, 1981.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: quality construction documents; computers. Includes bibliographical references (p. 78-81).

Multi-span precast concrete segmental bridges are commonly constructed using the balanced cantilever method, which essentially involves sequentially extending precast segments outwards from each pier in a balanced manner. A gap of 100 to 200 mm wide is usually provided around the mid-span location between the last two approaching segments to facilitate erection. In-situ concrete is then cast to ‘stitch’ the segments together, thus making the bridge deck continuous. In the current practice, the in-situ concrete stitches are usually designed to be capable of sustaining considerable sagging moment but only minimal hogging moment. Failure of stitches may occur under exceptional circumstances that may potentially trigger a progressive collapse. However, relatively little research in this area has been carried out. In view of this, the author is motivated to undertake an extensive study of the behaviour of in-situ concrete stitches and the effects of their performance on the robustness of typical segmental bridges. Experimental study is carried out to examine the behaviour of in-situ stitches under different combinations of internal forces. Series of stitch specimens of different configurations are tested. Subsequent parametric studies are conducted numerically to examine the effects of various parameters on the load-displacement characteristics of the stitches. Formulae for strength estimation are proposed based on the results. A study of robustness involves analyzing the collapse behaviour of a structure in an extreme event and the analysis should be carried out up to and then well beyond the state of peak strength of structural members. A finite element programme for post-peak analysis is therefore developed for the present study. As the ability of a member section to sustain large inelastic deformation can ultimately affect the robustness of a structure, an investigation is conducted to examine the effects of steel content, yield strength and prestressing level on the ductility and deformability of prestressed concrete sections. Using the programme developed, the formation of collapsing mechanisms of a multi-span segmental bridge deck in an extreme event is examined. A typical bridge deck is subject to prescribed accidental load on its span in order to analyze the sequence of failure. Substantial redistribution of internal forces along the deck is observed as failures initiate, thus causing subsequent failures of other deck sections even though they have been designed to resist the internal forces at the ultimate limit state. The results indicate that any span of a multispan bridge may become a temporary end-span in the event of collapse of an adjacent span and the strength of the sections must be designed accordingly to prevent progressive failure. As a span becomes a temporary end-span, the in-situ concrete stitches may experience substantial moment and shear, and their failure could potentially trigger progressive collapse of the entire bridge deck. Towards the end of the thesis, important design considerations that can enhance the performance of in-situ concrete stitches and robustness of precast concrete segmental bridges are presented. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Building industry is one of the most influential economic sectors, which accounts for 10% of the gross domestic product (GDP) globally and 40% of the world energy consumption. To achieve the goal of sustainable development, it is necessary to understand the sustainability performance of building construction in the environmental, the economic and the social aspects. This study quantitatively evaluates impacts of building construction in the three aspects by using the recently developed life cycle sustainability assessment (LCSA) methodology, in which environmental life cycle assessment (ELCA), environmental life cycle costing (ELCC), and social life cycle assessment (S-LCA) are integrated. The scope of this research covers ‘cradle-to-site’ life cycle stages, from raw material extraction to on-site construction. Three life-cycle models are developed, namely the Environmental Model of Construction (EMoC), the Cost Model of Construction (CMoC), and the Social-impact Model of Construction (SMoC). EMoC is a comprehensive ELCA model that evaluates environmental impacts of building construction by considering eighteen impact categories. CMoC is an ELCC model that provides analyses on construction costs and externalities. SMoC is an innovative S-LCA model being able to quantify social impacts of building construction in thirteen social impact categories. The three models are then integrated into a newly proposed LCSA framework. In order to select an appropriate LCIA method for EMoC, the differences among existing life cycle impact assessment (LCIA) methods are investigated. It is found that LCIA methods are consistent in global impact categories, while inconsistent in regional impact categories. ‘ReCiPe’ is selected as the LCIA method to be used in EMoC. Midpoint and endpoint approaches of ‘ReCiPe’ can lead to different interpretations. Endpoint approach emphasizes on certain impact categories and can only be used when midpoint results are provided. A life cycle inventory is established for ready mixed concrete and precast concrete based on site-specific data from concrete batching plant and precast yard. EMoC is employed to compare environmental performance of precast and cast-in-situ construction methods. It is found that adoption of precast concrete can significantly improve environmental performance of building construction. SMoC suggests that adoption of precast concrete can have both negative and positive impacts on local employment. A case study is conducted to test the model performance. It demonstrates that environmental impacts of ‘cradle-to-site’ construction activities are mostly attributed to the material stage. The external cost due to carbon emission is about 2% of the total construction cost. Environmental-friendly on-site construction practices can significantly improve social performance of building construction. The major findings of this study are verified through interviews with the local experts in Hong Kong. These validation interviews confirm that the proposed LCSA framework and the developed models contribute to the building industry in Hong Kong. In particular, this study can be used as a supplementary to the building assessment scheme, HK BEAM Plus. Results from this study can improve the understanding of building sustainability. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

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