Infrastructure Engineering - Research Publications
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ItemThe value of water in storage: Implications for operational policies(Curran Associate Inc., 2018-01-01)With desalination plants becoming an increasingly common feature of water supply systems for major cities, the options for managing water security are now markedly different to past times when the short-term response to low water availability essentially revolved around reducing usage. The operation of desalination plants and other components of diversified water supply systems now enable operators to increase availability, essentially by producing water. The operation of such systems clearly impacts operational costs but, more subtly, also impacts future augmentation decisions. This can have major cost implications as there is a trade-off between the costs of operating a water supply system and the probability and timing of future augmentations that leads to important differences in the economics of reliably supplying water. This paper first summarises an economic analysis framework in which to explore the interaction of short (operational) and long (capital investment) term decisions towards maintaining water security. It then explores the implications of different operation approaches in Melbourne’s water supply system, assuming a planned augmentation pathway under conditions of low water availability. We assume augmentation decisions are prompted by critically low water availability events, rather than long-term reliability analysis. We show that the majority of the variation in cost of maintaining a reliable water supply is associated with impacts of operational rules on likely capital investment and that this results in a strong interaction between short and long-term decision making. The outcome of this work has implications for both operational decision making and augmentation planning for urban water supply systems. These implications are relevant to any water supply system where a climate independent water supply source, such as desalination, can be accessed.
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ItemNo Preview AvailableEquifinality and process-based modelling(American Geophysical Union, 2018-11-26)Equifinality is understood as one of the fundamental difficulties in the study of open complex systems, including catchment hydrology. A review of the hydrologic literature reveals that the term equifinality has been widely used, but in many cases inconsistently and without coherent recognition of the various facets of equifinality, which can lead to ambiguity but also methodological fallacies. Therefore, in this study we first characterise the term equifinality within the context of hydrological modelling by reviewing the genesis of the concept of equifinality and then presenting a theoretical framework. During past decades, equifinality has mainly been studied as a subset of aleatory (arising due to randomness) uncertainty and for the assessment of model parameter uncertainty. Although the connection between parameter uncertainty and equifinality is undeniable, we argue there is more to equifinality than just aleatory parameter uncertainty. That is, the importance of equifinality and epistemic uncertainty (arising due to lack of knowledge) and their implications is overlooked in our current practice of model evaluation. Equifinality and epistemic uncertainty in studying, modelling, and evaluating hydrologic processes are treated as if they can be simply discussed in (or often reduced to) probabilistic terms (as for aleatory uncertainty). The deficiencies of this approach to conceptual rainfall-runoff modelling are demonstrated for selected Australian catchments by examination of parameter and internal flux distributions and interactions within SIMHYD. On this basis, we present a new approach that expands equifinality concept beyond model parameters to inform epistemic uncertainty. The new approach potentially facilitates the identification and development of more physically plausible models and model evaluation schemes particularly within the multiple working hypotheses framework, and is generalisable to other fields of environmental modelling as well.
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ItemThe grass is greener on the other side: understanding the effects of green spaces on Twitter user sentiments(ACM Press, 2018)Green spaces are believed to improve the well-being of users in urban areas. While there are urban research exploring the emotional benefits of green spaces, these works are based on user surveys and case studies, which are typically small in scale, intrusive, time-intensive and costly. In contrast to earlier works, we utilize a non-intrusive methodology to understand green space effects at large-scale and in greater detail, via digital traces left by Twitter users. Using this methodology, we perform an empirical study on the effects of green spaces on user sentiments and emotions in Melbourne, Australia and our main findings are: (i) tweets in green spaces evoke more positive and less negative emotions, compared to those in urban areas; (ii) each season affects various emotion types differently; (iii) there are interesting changes in sentiments based on the hour, day and month that a tweet was posted; and (iv) negative sentiments are typically associated with large transport infrastructures such as train interchanges, major road junctions and railway tracks. The novelty of our study is the combination of psychological theory, alongside data collection and analysis techniques on a large-scale Twitter dataset, which overcomes the limitations of traditional methods in urban research.
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ItemActivity-based Mobility Profiling(ACM Press, 2018)Several studies have shown that the spatio-temporal mobility traces of human movements can be used to identify an individual. However, this work presents a novel framework for activity-based mobility profiling of individuals using only the temporal information. The proposed framework is conducive to model individuals' activity patterns in temporal scale, and quantifies the uniqueness measures based on certain temporal features of the activity sequence.
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ItemA web-based interface to visualize and model spatio-temporal variability of stream water quality(River Basement Management Society, 2018)Understanding the spatio-temporal variability in stream water quality is critical for designing effective water quality management strategies. To facilitate this, we developed a web-based interface to visualize and model the spatio-temporal variability of stream water quality in Victoria. We used a dataset of long-term monthly water quality measurements from 102 monitoring sites in Victoria, focusing on six water quality constituents: total suspended solids (TSS), total phosphorus (TP), filterable reactive phosphorus (FRP), total Kjedahl nitrogen (TKN), nitrate-nitrite (NOx), and electrical conductivity (EC). The interface models spatio-temporal variability in water quality via a Bayesian hierarchical modelling framework, and produces summaries of (1) the key driving factors of spatio-temporal variability and (2) model performance assessed by multiple metrics. Additional features include predicting the time-averaged mean concentration at an un-sampled site, and testing the impact of land-use changes on the mean concentration at existing sites. This tool can be very useful in supporting the decision-making processes of catchment managers in (1) understanding the key drivers of changes in water quality and (2) designing water quality mitigation and restoration strategies.
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ItemIntegrated modelling of spatio-temporal variability in stream water quality across victorian catchments(Engineers Australia, 2018-01-01)Degraded water quality in rivers and streams can have large economical, societal and ecological impacts. Stream water quality can be highly variable both over space and time, so understanding and modelling these spatio-temporal variabilities is critical to developing management and mitigation strategies to improve riverine water quality. However, there is currently limited capacity to model stream water quality due to the lack of understanding of the key factors driving spatio-temporal variability in water quality. To address this, a Bayesian hierarchical statistical model has been developed to describe the spatio-temporal variability in stream water quality across multiple catchments in the state of Victoria, Australia. We used monthly water quality monitoring data collected at 102 sites over 20 years. The modelling focused on three key water quality indicators: total suspended solids (TSS), nitrate-nitrite (NOx) and salinity (EC). It was found that both human-influenced catchment characteristics (land use) and other natural characteristics such as climate or topography are important drivers of spatial variabilities. The key drivers of temporal variability are changes in streamflow, climate and vegetation cover. These key drivers have been integrated into a spatio-temporal modelling framwork. These models can be applied at different spatial and temporal scales, and explain a reasonable proportion of spatio-temporal variation in the different water quality constituents. The extension and adaption of these models is currently underway to create an operational tool to forecast stream water quality responses to potential land use and climatic changes.
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ItemNo Preview AvailableA pilot study on users’ IEQ perceptions in a residential aged care facility in Melbourne(RMIT, 2018-11-29)The aged population in Australia is expanding rapidly. To cater for the Australia’s ageing population, there is a significant increase in demand for aged care facilities over the coming decades. The indoor environmental quality (IEQ) affects users’ physical health and psychological wellbeing. However, systematic research on the relationship between users’ perceptions and IEQ of aged care facilities has yet to be developed. In this pilot study, a residential aged care facility in Melbourne was selected as a case study for investigating the differences between the measured IEQ data and the users’ perceived individual comfort. A questionnaire survey was conducted to collect the perceptions of users on IEQ. Environmental sensors which enable web-based data monitoring were deployed. The measured data were then analysed together with the questionnaire survey results for drawing a comparison with the users’ perceptions. It was found that the measurements by environmental sensors are realistic and the survey questionnaires are appropriate for the study. For the future surveys, the language barrier needs to be considered for non-English speakers.
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ItemFragility Curves for Limited Ductile Reinforced Concrete Buildings(Australian Earthquake Engineering Society, 2018)Reinforced concrete buildings make up the majority of Australian building stocks. Structural elements of these buildings are often designed with limited to nonductile detailing. With a very low building replacement rate many of the Australian buildings are vulnerable to major earthquakes and pose significant risk to lives, properties and economic activities. This paper presents studies on seismic vulnerability assessments of limited ductile reinforced concrete buildings. Fragility curves have been developed for three types of buildings, buildings that are mainly supported by shear or core walls, buildings that are supported by shear walls and moment resisting frames and podium-tower buildings featuring a transfer structure. The studies form a part of a collaborative research under the Bushfire and Natural Hazards Cooperative Research Centre (BNHCRC) on “cost-effective mitigation strategy development for building related earthquake risk”.
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ItemDevelopment of a Soil Site Ground Motion Database for Australian Seismic Structural Design(Australian Earthquake Engineering Society, 2018)This paper presents the development of a ground motion acceleration database that is specifically established for seismic structural design purpose in Australia. The database particularly focuses on providing abundant accelerograms representing earthquakes with a 500-year and 2500-year return period based on the Australian code spectrum model. Typical soil profiles were derived from borehole records in Melbourne, Sydney and Brisbane to account for the sediment amplification effect on soil sites, considering the site natural period as the main classification parameter. Using the equivalent linear analysis, a suite of MATLAB programs referred to as SUA was validated by comparison with results from SHAKE91 and is applicable for quantity production. The development of this database aims at producing ground motion acceleration time histories that fit in code response spectrums and can be applied in Australia structural design, and is an early attempt for future work with ground motion attenuation models.
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ItemA Review of GMPEs that Have Been Proposed for Use in South-eastern Australia by Comparison with MMI Data(Australian Earthquake Engineering Society, 2018-11-16)Several ground motion prediction equations (GMPEs) have been adopted for use in Australia by Geoscience Australia (GA) as presented in its publication known as NSHA 2018. Five such adopted GMPEs have been evaluated with three developed locally and two “third party” GMPEs that were taken from external sources. GMPEs codenamed A12 and SGC09 in NSHA 2018 have been included in this evaluation study. The peak ground velocity values so predicted by these GMPEs have been used to infer Modified Mercalli Intensity (MMI) values for comparison with data recorded from the historical earthquake events. It is shown that ground motion intensities of some historical earthquakes (that were within 100 km from the epicentre) as inferred from the A12 and SGC09 model are lower than what has been recorded from the historical archives. The authors also made their own post-dictions by adapting seismological models that had been developed in Central and Eastern North America. These seismological models have been modified to consider crustal differences between the host and target regions. Ground motion intensities that are based on modifying the considered seismological models are in much better agreement with field observations than the GMPEs that have been adopted by GA previously.