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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ItemA Machine Learning Approach for the Performance Prediction of GCHPs with Horizontal Ground Heat Exchangers(IOS PRESS, 2019-01-01)This study aims to provide a machine learning approach to predict the performance of Ground Coupled Heat Pumps (GCHPs) with horizontal Ground Heat Exchangers (GHEs). Specifically, an ANN model was developed for this purpose which can potentially be generally applied to similar sites at different locations and climate conditions, with even limited types of input data. In this example, a TRNSYS model regarding a typical horizontal trench within a rural farm in Australia, has been developed and verified, covering over 50 different yearly loading patterns under 3 different climate conditions. The simulated performance data is then used to train the artificial neural network. As results, the trained ANN is able to predict the performance of GSHPs systems with identical GHEs even under climatic conditions (and locations) that has not been specifically trained for. With only limited input data, the presented ANN shows no more than 5% error in most cases tested.
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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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ItemNo Preview AvailableParametric study of the effect of thermal properties and ambient temperature on tensile stress and strength development in mass concrete(The International Federation for Structural Concrete (FIB), 2019-01-01)Thermal stress typically takes place at early ages when concrete is undergoing exothermic hydration reaction and is restricted from expansion and contraction by surrounding structural elements. In mass concrete structures, the relatively large temperature differences between the core and the surface produce differential dilation which leads to tensile stresses. Potential tensile cracks develop when the stress experienced by the concrete exceeds the concurrent strength of the maturing concrete. This effect in turn can lead to performance reduction, or in some instances, instability of structure and must be dealt with care. While published literature reports extensively on hydration based mechanical properties of concrete, only a few has considered investigating the in-situ performance of the material accounting for thermal stresses. In what concerns crack formation, consideration of the thermo-mechanical boundary conditions are important nuts that have not been investigated explicitly. This research aims to provide insight into the impacts of thermal related parameters on early age concrete crack formation through computational modelling.
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ItemAnalysis of an Ad-hoc Platoon Formation and Dissolution Strategy on a Multi-lane Highway.(University of Auckland, 2019-01-01)Vehicle platooning has become popular in the recent Intelligent Transportation System (ITS) research. The literature typically assumes a planned formation and dissolution of platoons, mostly at source and destination. In contrast, this research considers platoons that can be formed on the fly. We investigate a greedy type of platoon formation with no particular order of destinations of the platoon members. This greedy formation allows a quick formation of the platoon but imposes an overhead of platoon rebuild cost when platoon members leave. The question arises whether this greedy formation and dissolution of platoons can preserve the original fuel benefit of platooning. To investigate this question, this research implements such a strategy and provides a generic guideline for fuel-efficient ad-hoc platooning
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ItemModelling Uncertainty of Single Image Indoor Localisation Using a 3D Model and Deep Learning(ISPRS, 2019-05-29)Many current indoor localisation approaches need an initial location at the beginning of localisation. The existing visual approaches to indoor localisation perform a 3D reconstruction of the indoor spaces beforehand, for determining this initial location, which is challenging for large indoor spaces. In this research, we present a visual approach for indoor localisation that is eliminating the requirement of any image-based reconstruction of indoor spaces by using a 3D model. A deep Bayesian convolutional neural network is fine-tuned with synthetic images generated from a 3D model to estimate the camera pose of real images. The uncertainty of the estimated camera poses is modelled by sampling the outputs of the Bayesian network fine-tuned with synthetic images. The results of the experiments indicate that a localisation accuracy of 2 metres can be achieved using the proposed approach.
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ItemA multi-dimensional analytics platform to support planning and design for liveable and sustainable urban environment(International Society for Photogrammetry and Remote Sensing (ISPRS), 2019-09-23)New urban strategies encourage compact city and higher density urban development due to unprecedented city growth and rapid urbanisation. This has led to greater attention to multi-dimensional representation, modelling and analytics of urban settings among urban planners, decision makers, and researchers. Nowadays, urban planning and urban design practitioners and scholars leverage the advancements in computer technology and multi-dimensional visualisation in examining the development scenarios from physical, environmental, social, and economic aspects. However, many urban planners still rely on two-dimensional (2D) land information and urban designers use three-dimensional (3D) graphic-based engines to asses a proposed building or assess the impact of changing development regulations. This limits the decision makers from a holistic approach through integrating the urban systems with other application domains such as transport, environmental, and disaster management to ensure the liveability of cities. This paper describes the design, and development of a multi-dimensional and spatially enabled platform to support liveability planning in Singapore. A Quantitative Urban Environment Simulation Tool (QUEST), developed in Singapore, leveraged 3D mapping data captured under the Singapore Land Authority's (SLA) 3D National Topographic Mapping project. SLA's 3D data including Building Information Model (BIM), CityGML, and other geospatial data (building footprints and land use) were processed and adapted as a service for a series of urban analytics. The paper concludes that the prerequisites for any urban environmental simulation system to be integrated with other application domains are 3D mapping data and a digital urban model, which must be spatially accurate and based on open data standards.
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ItemNumerical simulation of single-sided natural ventilation: Impacts of balconies opening and depth scale on indoor environment (IOP Conference Series: Earth and Environmental Science (EES), 2019)Heating Ventilation and Air Conditioning (HVAC), including, Mechanical ventilation (MV) in the building sector accounts for around 40% of electricity consumption and a large percentage of Greenhouse Gas (GHG) emissions. Natural ventilation (NV), as an alternative method, assist in decreasing energy consumption as well as harmful emissions. Balconies, a common architectural element in high rise residential buildings, could enhance NV and reduce reliance on mechanical ventilation in cooling dominant climates. Indoor air velocity (IAV) and distribution due to NV is less predictable than MV, and the impacts of balcony geometry on IAV and distribution profile have not yet been classified. This study, focusing on single-sided ventilation apartments, seeks to determine to what extent balcony depth and door opening area impacts on the indoor environment of the attached living area. For this, 3D – steady-state Computational Fluid Dynamics (CFD) simulations were conducted using ANSYS Fluent. The simulation results were validated against measured data in a full-scale experimental study in a residential building in subtropical Brisbane, Australia. Five different openings and nine depth scenarios were modelled, with results showing variances in indoor mean air velocity and temperature. The outcomes suggest that further research on the indoor distribution of temperature and air velocity may provide further clarity on the impact of balcony geometry on occupant comfort through NV.
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ItemNumerical simulation of single-sided natural ventilation: Impacts of balconies opening and depth scale on indoor environment (SEGT 2019, 2019)Heating Ventilation and Air Conditioning (HVAC), including, Mechanical ventilation (MV) in the building sector accounts for around 40% of electricity consumption and a large percentage of Greenhouse Gas (GHG) emissions. Natural ventilation (NV), as an alternative method, assist in decreasing energy consumption as well as harmful emissions. Balconies, a common architectural element in high rise residential buildings, could enhance NV and reduce reliance on mechanical ventilation in cooling dominant climates. Indoor air velocity (IAV) and distribution due to NV is less predictable than MV, and the impacts of balcony geometry on IAV and distribution profile have not yet been classified. This study, focusing on single-sided ventilation apartments, seeks to determine to what extent balcony depth and door opening area impacts on the indoor environment of the attached living area. For this, 3D – steady-state Computational Fluid Dynamics (CFD) simulations were conducted using ANSYS Fluent. The simulation results were validated against measured data in a full-scale experimental study in a residential building in subtropical Brisbane, Australia. Five different openings and nine depth scenarios were modelled, with results showing variances in indoor mean air velocity and temperature. The outcomes suggest that further research on the indoor distribution of temperature and air velocity may provide further clarity on the impact of balcony geometry on occupant comfort through NV.
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ItemInitial Analysis of Simple Where-Questions and Human-Generated Answers(LIPIcs, 2019)Geographic questions are among the most frequently asked questions in Web search and question answering systems. While currently responses to the questions are machine-generated by document/snippet retrieval, in the future these responses will need to become more similar to answers provided by humans. Here, we have analyzed human answering behavior as response to simple where questions (i.e., where questions formulated only with one toponym) in terms of type, scale, and prominence of the places referred to. We have used the largest available machine comprehension dataset, MS-MARCO v2.1. This study uses an automatic approach for extraction, encoding and analysis of the questions and answers. Here, the distribution analysis are used to describe the relation between questions and their answers. The results of this study can inform the design of automatic question answering systems for generating useful responses to where questions.
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