Infrastructure Engineering - Research Publications
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ItemMulti-Criteria Analysis of a Developed Prefabricated Footing System on Reactive Soil Foundation(MDPI, 2021-11)The need for advancements in residential construction and the hazard induced by the shrink–swell reactive soil movement prompted the development of the prefabricated footing system of this study, which was assessed and compared to a conventional waffle raft using a multi-criteria analysis. The assessment evaluates the structural performance, cost efficiency, and sustainability using finite element modelling, life cycle cost analysis, and life cycle assessment, respectively. The structural performance of the developed prefabricated system was found to have reduced the deformation and cracking by approximately 40%. However, the cost, GHG emission, and embodied energy were higher in the prefabricated footing system due to the greater required amount of concrete and steel than that of the waffle raft. The cost difference between the two systems can be reduced to as low as 6% when prefabricated systems were installed in a highly reactive sites with large floor areas. The life cycle assessment further observed that the prefabricated footing systems consume up to 21% more energy and up to 18% more GHG emissions. These can significantly be compensated by reusing the developed prefabricated footing system, decreasing the GHG emission and energy consumption by 75–77% and 55–59% with respect to that of the waffle raft.
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ItemMicrostructural Investigation of High-Volume Fly Ash Composites Containing Nano-Calcium Silicate Hydrate Crystals(ASCE-AMER SOC CIVIL ENGINEERS, 2021-12-01)
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ItemComparative assessment of embodied energy of recycled aggregate concrete(Elsevier, 2017)Concrete waste can be recycled to produce an aggregate product; referred to as recycled concrete aggregate (RCA). While RCA is mainly used as a road base filler material, it has the potential to replace natural coarse aggregate (NA) in structural concrete. In determining the environmental performance of the resultant concrete product from this substitution, referred to as recycled aggregate concrete (RAC) against its counterpart, natural aggregate concrete (NAC), it is important to consider the effects of the entire life cycle including the upstream processes associated with each. This paper evaluates “cradle-to-gate” embodied energy (EE) of RAC received at a construction site, in comparison to NAC, using the input-output-based hybrid approach, using an Australian context. The paper constructs a model to evaluate EE of RAC and analyses the incremental energy of RAC as opposed to NAC, to identify what contribute to the difference out of four primary factors discussed in previous research. It was found that the EE of RAC is marginally different to that of NAC by +2.1 to −1.1%, and the variation was subject to the magnitude and direction of the four factors considered. The mix composition, primarily the binder composition, was found to have the highest contribution to the difference, significantly standing out from the direct energy difference between RCA and NA, difference of sourcing distance between RCA and NA and the difference of direct manufacturing energy between RAC and NAC.
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ItemMethodology for the integrated assessment on the use of recycled concrete aggregate replacing natural aggregate in structural concrete(Elsevier, 2017)Recycled concrete waste in the form of recycled concrete aggregate (RCA) is presently used mostly as a road base filler in Australia. However, instead of producing natural aggregate (NA) to manufacture natural aggregate concrete (NAC) to use in structural concrete, there is potential to use RCA to manufacture recycled aggregate concrete (RAC). While the material performance of RAC compared to NAC is analysed in the existing literature, it is not evident whether the use of RCA in structural concrete results in financial and environmental benefits. Previous literature analysing these aspects mostly focuses on a single area of investigation. This paper presents an integrated methodology for the assessment of the use of RCA replacing NA in structural concrete, considering technical, financial, environmental and social perspectives. Cost-benefit assessment (CBA) has been used to evaluate the internalised impacts as well as external costs concerning the use of both RAC and NAC. The scope of each discipline-focused assessment is presented demarcating the relevant scope for further study, and the specific tools and methodologies to be adopted are specified. Finally, amalgamating the different discipline-focused assessments, a unique approach for comparing a sustainable, alternative raw material for concrete, is presented in this paper.
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ItemIntegrated assessment of the use of recycled concrete aggregate replacing natural aggregate in structural concrete(Elsevier, 2018)The use of recycled concrete aggregate (RCA) replacing natural aggregate (NA) to produce concrete named as recycled aggregate concrete (RAC) has gained increased importance in the last few decades. Despite many visible advantages associated with the initiative, RAC is not manufactured at commercial scale to replace natural aggregate concrete (NAC) used as structural concrete in Australia presently. To identify whether the production of RAC should be favoured against NAC, an integrated assessment combining multiple criteria is essential as the previous research findings provide mixed outcomes on financial viability, product performance and environmental performance. This paper uses an integrated assessment methodology employing cost-benefit analysis (CBA) which combines the financial, direct and indirect environmental, social outcomes associated with the initiative to evaluate its suitability. By combining several qualitative and quantitative studies published by the author/s, an integral result to compare the use of RCA replacing NA in structural applications is conducted in this study. Net present value (NPV) to society associated with a unit volume of RAC is evaluated as a representative indicator to compare RAC against NAC in this paper. The results state that a unit volume of RAC results in a positive NPV of 4.2–6.0% of the price of NAC for 30% replacement (and 16.3–22.6% for 100%), prior to being used in a building r. Simulation of application of the RAC to two case study buildings indicate that the average price of concrete used in the buildings is decreased by 4.1–6.1%. The results indicate that, if the external benefit associated with the production of RAC is internalised and passed on to the purchaser of the product, production of RAC in structural buildings result in a positive NPV and saving of building material costs to the contractor.
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ItemNet incremental indirect external benefit of manufacturing recycled aggregate concrete(Elsevier, 2018-08-01)Concrete waste (CW) either reaches landfill with mixed waste or crushed to produce crushed concrete (CC) used as a road-base product in Australia. The coarse portion of CC, referred to as recycled concrete aggregate (RCA) has the potential to be used as an aggregate in structural concrete replacing natural aggregate (NA). The environmental performance of RAC has been studied in comparison to NAC, in terms of direct environmental implications (DEI) concerning the processes in the production chain of these products. However, when replacement at industry level is considered, the implications go beyond the DEI, and affect a series of other products/processes within a system boundary, referred to as indirect environmental implications (IEI). This paper quantifies the key IEI associated with the use of RCA in structural concrete and evaluates the external costs and benefits associated with it using economic evaluation methods. The net benefit associated with the avoidance of landfill of CW, extraction of NA, and transportation of waste and by-products are the major externalities identified and quantified in this paper. Evaluation of these suggest that there is a significant net benefit ranging from 9% to 28% of the price of natural aggregate concrete (NAC) with the production of recycled aggregate concrete (RAC), for RCA replacement rates between 30% and 100%.
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ItemDetecting structural damage to bridge girders using radar interferometry and computational modelling(JOHN WILEY & SONS LTD, 2017-10)The process for assessing the condition of a bridge involves continuously monitoring changes to the material properties, support conditions, and system connectivity throughout its life cycle. It is known that the structural integrity of bridges can be monitored by measuring their vibration responses. However, the relationship between frequency changes and structural damage is still not fully understood. This study presents a bridge condition assessment framework which integrates computational modelling and noncontact radar sensor techniques (i.e., IBIS-S) to predict changes in the natural frequencies of a bridge girder as a result of a range of parameters that govern its structural performance (e.g., elastomeric bearing stiffness, concrete compressive stiffness, and crack propagation). Using a prestressed concrete bridge in Australia as a case study, the research outcomes suggest that vibration monitoring using IBIS-S is an efficient way for detecting the degradation of elastomeric bearing stiffness and shear crack propagation in the support areas that can significantly affect the overall structural integrity of a bridge structure. However, frequency measurements have limited capability for detecting the decrease in the material properties of a bridge girder.
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ItemDesign and Development of Weatherproof Seals for Prefabricated Construction: A Methodological Approach(MDPI, 2018-09)Satisfactory weatherproofing of buildings is vital to maximise their design life and performance which requires the careful design of external sealing technologies. Systems commonly available have served well in conventional construction however with many prefabricated systems emerging in the building industry new and novel means of weatherproofing between panels and modules need to be developed purpose specific to this application. This paper presents a holistic and fundamental methodological approach to Design and Development of waterproof seals and has been applied specific for prefabricated panelised and modular systems. Two purpose specific weatherproof seals are finally presented. Flow charts of the overview of the suggested methodological approach and the processes within which include DfMA that have been incorporated into understanding and developing seals for this practical application. These strategies have enabled a resourceful and holistic set of processes that can be adapted and used for similar forms of product research in new and developing areas of construction such as prefabrication. The design and development process is thoroughly investigated and has resulted in an exploration of the technical challenges and potential solutions which take into consideration factors from installation limitations to building tolerances.
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ItemBone fracture healing under Ilizarov fixator: Influence of fixator configuration, fracture geometry, and loading(WILEY, 2019-06-01)This study aims to enhance the understanding of the relationship between Ilizarov fixator configuration and its effects on bone fracture healing. Using Taylor spatial frame (TSF) as an example, the roles of critical parameters (ie, TSF ring diameter, wire pre‐tension, fracture gap size, and axial load) that govern fracture healing during the early stages were investigated by using computational modelling in conjunction with mechanical testing involving an advanced 3D optical measurement system. The computational model was first validated using the mechanical test results and then used to simulate mesenchymal stem cell (MSC) differentiations within different regions of the fracture site under various combinations of TSF ring diameter, wire pre‐tension, fracture gap size, and axial load values. Predicted spatially dependent MSC differentiation patterns and the influence of each parameter on differentiations were compared with in vivo results, and good agreement was seen between the two. Gap size was identified as the most influential parameter in MSC differentiation, and the influence of axial loading and TSF configuration (ie, ring diameter and wire pre‐tension) on cell differentiation was seen to be gap size dependent. Most changes in cell differentiation were predicted in the external callus (periosteal), which is the crucial region of the callus in the early stages. However, for small gap sizes (eg, 1 mm), significant changes were predicted in the endosteal callus as well. The study exhibits the potential of computational models in assessing the performance of Ilizarov fixators as well as assisting surgeons in patient‐specific clinical treatment planning.