Infrastructure Engineering - Theses
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ItemPerformance of steel framed domestic structures subjected to earthquake loads( 1997)This thesis investigates the performance of cold formed steel framed domestic structures subjected to earthquake loads. These structures generally include one and two storey houses, comprising steel wall framing, exterior veneer cladding and internal lining. The dynamic, non-linear performance of such structures during earthquakes is simplified to static linear behaviour for design purposes using the structural response modification factor, Rµ. This factor is defined as the product of the structural ductility reduction factor, Rµ, and the over-strength of the system, Ω. This thesis develops a rigorous technique for the determination of Rµ and the application of this technique is demonstrated for a proprietary framing system. This is achieved using novel non-linear, transient dynamic finite element models of these structures subjected to earthquake loads. The model parameters are estimated from unique experiments conducted on representative structures using a shaking table. It is shown that the framing system considered is non-ductile (ie Rµ≈1). This result directly contradicts the assumed ductile behaviour of these framing systems as specified in the Australian earthquake loading standard, AS 1170.4. The significance of this is that current design practices are unconservative and therefore underestimate the earthquake loads on these structures.
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ItemA competitive estimating and tendering strategy model for use in the civil engineering construction industry( 1996)The Australian civil engineering construction industry does not have a formal methodology for setting margin (markup) on project tenders. A need exists to structure and formalise the decision-making process used in setting margin, since the margin-size decision is critical to a company's success in winning work and its subsequent profitability. Despite the number of software systems available for cost estimating, none has features to help in making the margin-size decision. Numerous competitive tendering strategy models for setting margin have been developed, but very few are used in practice. A number of disadvantages in the features of these models make them unsuitable and difficult to apply. The objective of this thesis is to improve the procedures and tools available for use in the competitive tendering process in the civil engineering construction industry. This objective is achieved primarily by the development of a competitive tendering strategy model. The competitive tendering strategy model uses fuzzy set theory, a modelling technique designed for handling linguistic and approximate information, to model the margin-setting process and provide recommendations of margin size. The use of fuzzy set theory allows assessments to be made in qualitative terms, which suit the subjective nature of the margin-size decision. The goal of the competitive tendering strategy model is to help a company achieve its objectives in tendering. The model provides over ninety factors that may influence the choice of margin size, and enables the company to assess the impact of those that are relevant to its tender situation. The competitive tendering strategy model formalises the decision-making process and provides a standard methodology for setting margin on civil engineering project tenders, which can be tailored to suit the individual practices of each company. The implementation of the model in the form of a software system, named PRESTTO, makes the model quick and easy to use. The PRESTTO software system can increase the efficient use of the brief time available for setting margin. The competitive tendering strategy model provides accurate recommendations of margin size, based on its validation with actual project tenders collected from a survey of the Australian construction industry. The model therefore reflects current sound decision-making practices in setting margin and can be used with confidence as a guide to setting margin. The objective of this thesis is also achieved by the development of a theoretical framework that defines a standard methodology for the integration of cost estimating, tendering, and cost control, for use by both clients (owners) and contractors. The competitive tendering strategy model is placed in the context of this overall framework, since the margin-size decision is not made in isolation. This framework provides the theoretical basis for the implementation of a fully integrated software system. The PRESTTO software system, which consists of a cost estimating module integrated with a tendering module, is a partial implementation of this fully integrated system. A major conclusion of this thesis is that fuzzy set theory can be applied successfully to model the margin-size decision. Fuzzy set theory is an enhancement on previous modelling techniques because it allows assessments to be made in qualitative and approximate terms, which suit the nature of the margin-size decision. The competitive tendering strategy model developed, which supports subjective judgement and experience, can help civil engineering contractors gain a competitive edge in tendering. By providing them with a standard methodology to improve the quality of their decision-making, this model can help contractors reduce the uncertainty associated with setting margin, resulting in a more competitive bid.
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ItemSeismic performance of concrete beam-slab-column systems constructed with a re-usable sheet metal formwork system( 2007)This report describes an investigation of seismic performance of a ribbed slab system constructed with an innovative re-usable sheet metal formwork system. Experimental results from quasi-static cyclic lateral load tests on half-scale reinforced concrete interior beam-slab-column subassemblages are presented. The test specimen was detailed according to the Australian code (AS 3600) without any special provision for seismicity. This specimen was tested up to a drift ratio of 4.0 %. Some reinforcement detailing problems were identified from the first test. The damaged specimen was then rectified using Carbon Fibre Reinforced Polymer (CFRPs), considering detailing deficiencies identified in the first test. The repaired test specimen was tested under a lateral cyclic load as per the original test arrangement up to a drift level of 4%. The performance of the repaired specimen showed significant improvement with respect to the level of damage and strength degradation. The results of the rectified specimen indicate that the use of CFRPs may offer a viable retrofit/repair strategy in the case of damaged structures, where this damage may be significant. Two finite element analysis models were created and results of the first test were used to calibrate the FE model. The second FE model was used to obtain detail information about stress and strain behaviour of various components of the beam-column subassemblage and to check the overall performance before carrying out expensive lab tests. It was concluded that finite element modelling predictions were reliable and could be used to obtain more information compared to conventional type laboratory tests. Time-history analyses show that the revised detailing is suitable to withstand very large earthquakes without significant structural damage.