Infrastructure Engineering - Theses
Now showing items 1-12 of 369
Multi-objective optimisation for multi-residential building retrofit: A method and an application
The building sector has been at the centre of the environmental protection policies of the European Union (EU). This is mainly due to its high energy consumption (40% of the total) among the EU Members. Residential buildings are responsible for two-thirds of that amount. Recently, the European Commission set radical targets for the reduction of greenhouse gas (GHG) emissions by 2030 (50-55% reduction compared with 1990 levels) and 2050 (climate neutrality) and the building sector, especially the existing building stock, is expected to play a critical role in achieving those goals. Special consideration should be given to multi-residential buildings. Compared to other building types, they have limited suitable space for the installation of renewable energy systems and are governed by a complex legal framework, imposing additional challenges on decision-making. Targeting multi-residential buildings, this study developed a method for the identification of optimal retrofit sets. It is a multi-objective simulation-based optimisation method for the performance assessment of ‘whole building’ retrofit interventions under two objectives: the minimisation of the operating GHG emissions and the life-cycle cost. The innovation in the method is the integrated approach, considering energy supply, energy demand-side technologies and energy-saving measures. A dynamic building systems’ modelling process was also introduced, based on part-load performances, to address the accuracy limitations of existing, monthly quasi-steady state methods. The functionality of the method was illustrated through an application. The case study building is a 6-storey multi-family building, constructed before 1980. The performance of several retrofit sets of measures was compared to the ‘base case’ building, which is a comparable version of the case study building. To identify the way that various parameters of the building environment affect the method application and the obtained results, four locations were considered, one for each Greek climate zone. It was found that for all Greek climate zones, the cost-optimal retrofit set consists of the roof and basement ceiling insulation, the installation of air-to-air heat pumps (HP) for heating and cooling and solar thermal panels for domestic hot water (DHW). This way, the operating GHG emissions could be decreased from 59% to 67%, compared to ‘base case’, depending on the building location. To achieve a retrofit that minimises the GHG emittions (almost 90% less operating GHG emissions compared to ‘base case’), the obtained solution sets included wall, roof, basement ceiling insulation and window replacement with double or triple-glazed windows, central biomass boilers (locations without natural gas) or gas condensing boilers (locations with natural gas) for heating, air-to-air HPs for cooling and photovoltaic-thermal (PV/T) panels for DHW and electricity production. Net-zero carbon retrofit solutions could not be achieved for any location. The findings of the study are in line with the observed market trends (envelope insulation, installation of double-glazed windows and air-to-air HPs, condensing gas boilers or biomass boilers). Gas absorption HPs and air-to-water HPs will be competitive alternatives when their purchase costs decrease. Similarly, solar thermal collectors for DHW are the common practice, however, when solutions that minimise GHG emissions are required, PV/T panels have great potential but limited market penetration. The results obtained are specific to the financial situation, fuel, renewable energy sources and systems availability of the considered locations. They can be used as a guide for retrofitting similar buildings and construction types in urban areas of the Mediterranean climate, assisting policymakers and homeowners.
Displacement based seismic assessment of earth retaining structures
The present study deals with the displacement based seismic assessment of earth retaining structures. Detailed shaking table experiment has been performed on two different scaled down retaining wall models. The first set of shaking table experiment has been performed on base restrained retaining wall model, and the second set of shaking table experiment has been performed on a rotational base retaining wall model. It was observed from the shaking table experiment that inertial forces from backfill profoundly influence the seismic displacement of the earth retaining structures. Different dynamic properties of scaled down retaining wall models have also been studied with the shaking table experiment results. Significant amplification of horizontal acceleration in the backfill has also been observed during all shaking table experiments. A detailed geotechnical investigation has also been performed on the backfill used for scaled down retaining wall model construction. Characterization of the backfill has been achieved based on different geotechnical experiments. The hardening/softening behaviour of backfill has also been studied from the consolidated drained (CD) triaxial test results and the Mohr Coulomb material model. A detailed process for the finite element (FE) modelling of seismic actions on earth retaining structures has been explained. Capability of the FE models has also been verified by replication of the shaking table experimental results. A detailed and rigorous FE investigation has been performed on different earth retaining structures. The base restrained retaining wall, the free straining retaining wall, and the cantilever retaining wall founded on rock-socketed pile foundation have been considered for the FE investigations. Earthquake induced displacement behaviour of the earth retaining structures has been studied against different synthetic and historical accelerograms. The effects of different backfill type on the seismic response of earth retaining structures has also been studied. Significant amplification of the horizontal acceleration in the backfill has been observed for all cases. Simplified hand calculations have also been proposed for estimating the seismic displacement of the base restrained retaining wall. It was observed that the earthquake induced displacement of earth retaining structures mainly depends on the severity of ground shaking, inertial forces from the backfill, and hardening/softening behaviour of the backfill. In the case of a free-standing retaining wall and a retaining wall founded on rock socketed pile foundation, granular backfill shows better seismic performance than natural sand backfill. In the case of a retaining wall founded on the rock socketed pile foundation, high displacement of the rock-socketed piles has been observed.
Overland flow scaling behaviour in a burned dry hillslope
The scale-dependency of overland flow is frequently observed in rainfall runoff measurements, (Wilcox et al., 1997, Wilcox et al., 2003, Van de Giesen et al., 2000, Sheridan et al., 2014), yet largely neglected in rainfall-runoff models (Bloschl and Sivapalan, 1995, Chen et al., 2016a). Overland flow scaling behaviours within a given hillslope have been attributed to the main factors controlling infiltration and runoff processes including spatial variability of soil hydraulic properties (Julien and Moglen, 1990), run-on effect (Wainwright and Parsons, 2002, Langhans et al., 2014), macropore flow (Nyman et al., 2010, Ritsema and Dekker, 1995, Wessolek et al., 2009, Nyman et al., 2014, Stoof et al., 2014a, Ritsema et al., 2005), and rainfall temporal properties (Joel et al., 2002, Li and Sivapalan, 2011, Wainwright and Parsons, 2002). These factors are nonlinear and vary in time and space causing uncertainties when averaging between scales. Wildfire may introduce higher spatio-temporal variability to the factors controlling soil infiltration by vast alteration in soil and vegetation, and as a result of that scaling effects on hydrological processes may be altered in burned landscapes (Moody et al., 2013). However, the impact of fire on scaling behaviours is poorly investigated and only few practical studies have measured runoffs scaling on burned hillslopes (Sheridan et al., 2014). There are significant knowledge gaps in understanding overland flow scaling effects in relation to post-fire soil, surface factors and rainfall properties (Moody et al., 2013). This study aimed to investigate overland flow scaling behaviours in relation to soil and rainfall properties on a burnt hillslope by observations, measurements, and simulations. This was obtained by i) collecting rainfall-runoff data from different plot lengths at a eucalyptus hillslope, Southeast Australia burned by wildfire in 2013, ii) quantifying the degree of runoff scale-dependency from empirical rainfall-runoff data, iii) conducting stepwise regression analysis to investigate scaling behaviours of the observed runoffs in relation to the rainfall characteristics, iv) simulating overland flow and scaling effects by coupling traditional infiltration theory, run-on process and rainfall temporal variations, v) investigating macropore flow contribution to runoff scaling behaviour by measuring vertical pathways of activated macropores with a blue dye experiment at the site, modelling macropore flow in relation to runoff depth, and accounting macropore flow into rainfall-runoff simulations. This is the first study to investigate isolated impact of spatial variability of soil hydraulic conductivity, rainfall parameters, and macropore flow on overland flow scaling behaviour in a burned hillslope. The outcome of this study was partly obtained from field and laboratory measurements and rainfall-runoff monitoring at the field. These measurements and monitoring data were used for rainfall-runoff models parametrisation and verifications. The empirical rainfall-runoff data were collected from multi-scale runoff plots under natural rainfall conditions. The instruments were installed on a severely burned hillslope of eucalyptus forest in southeast Australia. Forty-one rainfall-runoff events were extracted from data collected during the second year following the fire. Strong scaling behaviour was observed for all observed events, seasonally and the whole study period where the rate of runoff declined with increasing plot length. The data from multi-scale runoff plots were used in the stepwise regression models to investigate runoff scaling behaviour in relation to rainfall volumetric and temporal parameters. Stepwise multiple regression analysis showed that generated runoffs and scaling effects were mainly influenced by annual rainfall depth than other rainfall factors while the impact on runoff productions decreases with increasing plot length. Measurements and monitoring data were used for model setup, parameterisation, and verifications of rainfall-runoff models to simulate overland flow scaling effects. The rainfall-runoff simulations provided a very weak demonstration of scaling behaviours with underestimated scaling effects. The simulated scaling behaviours did not improve when spatial variability of soil hydraulic conductivity (CVKs) accounted for the models. This concludes that models with traditional infiltration coupled with run-on process paradigm, and rainfall temporal variability cannot explain the observed scaling behaviour, even where spatially variability of soil hydraulic conductivity (CVKs) is considered. Measurement of activated macropore, water repellency strength and soil water content conducted from the top edge of the hill to downslope on one occasion. No systematic evidence was found regarding reduction in soil water repellency, nor an increase in activated macropore, nor higher water content within distance from uphill. The outcome from these measurements did not support the hypothesis of runoff scaling behaviour to be a result of infiltration increase with distance from uphill. Macropore flow was modelled in relation to runoff depth satisfying pores pressure entry at the point, that is exceeded more frequently with distance downslope due to increased runoff depths. The model consisted of macropore network algorithm, macropore filling when runoff depth exceeded the macropore entry pressure head based on the Young Laplace and Bernoulli equations, and gravity driven vertical flow from fully saturated macropore based on Darcy Law. The macropore flow application was coupled with rainfall-runoff models with traditional infiltration theory, runoff-runon, and rainfall temporal variability. The proportion of simulated macropore flow increased with plot lengths. Simulated scaling effects from models with macropore flow application obtained a better prediction of overland flow scaling behaviour. This concludes that macropore flow is the main factor affecting runoff scaling behaviours in water repellent soil where infiltration mostly occurs through activated macropores and preferential flow. This study supports the theory that macropore flow is a dominant factor controlling overland flow scaling behaviours in burnt dry hillslopes where the soil is strongly hydrophobic. Young-Laplace and Bernoulli equations were found sufficient to calculate macropore filling process in relation to runoff depth, and Darcy Law equation demonstrated continuous flows from full saturated macropore to underneath soil (Hardie et al., 2013, Buttle and House, 1997, Nimmo, 2012, Podgorney and Fairley, 2008). The simulations showed that higher macropore flow is triggered in the longer distance when runoff depth satisfies pressure entry of activated pores. This also explains why the impact of rainfall parameters on runoff productions and scaling decreases with length. The findings of this study are in agreements with earlier findings (Muller et al., 2018, Stoof et al., 2014a, Jarvis et al., 2008, Jarvis et al., 2016, Nimmo, 2012).
Vision-based crowd congestion management in transportation hubs
Congestion in transport hubs has been a big issue in many population booming cities as the current transport systems are not able to accommodate the increasing surge in travel demand caused by ongoing urbanisation and growth of the world population. The ubiquitous Closed-Circuit Television (CCTV) cameras in transport hubs provide a means for automatic crowd surveillance by utilising accurate and robust image-based crowd analysis models. However, this is an active field of research due to the challenges of occlusion among a large number of individuals and environmental changes, such as lighting fluctuations and changes in context over time. The research presented in this thesis aims to understand and manage the station congestion from the macro and micro perspectives by presenting a framework enabling individual origin-destination estimation and crowd congestion map generation. The main contributions of the study can be outlined as: 1) development of spatial-temporal deep learning models for macro-scale crowd density map generation, and micro-scale pedestrian Origin-Destination (O-D) estimation based on person re-identification in the internet of cameras. 2) a multi-modal framework for crowd analysis under emergency scenarios, especially low visibility situation, using RGBD cameras. 3) linking models and application by developing a web-GIS platform for real-time processing and visualization, thereby demonstrating the applicability of the research in crowd congestion management. This research presents distinct interdisciplinary components with relevance to crowd dynamics as well as image processing and with practical implications for smart station management.
Climate change in the Arctic Ocean: Long-term variability of metocean conditions
The Arctic is responding to climate change more rapidly and intensely than any other region on Earth. Besides the temperature rise and sea ice retreat, surface gravity waves are becoming more energetic, leading to rapid coastal erosion, affecting wildlife, communities and coastal infrastructures. In response to these changes, this research aims to investigate the metocean parameters across the Arctic Ocean over the past decades by numerical modelling, evaluating their climate and long-term variability. It introduces a systematic assessment of sea ice concentration, winds, and waves by computing their monthly averages, higher percentiles and their long-term trends. The trend analyses demonstrated that the sea ice melting has major responsibility for the general increasing trends in significant wave heights across the Arctic Ocean, as trends in wind speeds were milder compared to trends in waves and sea ice concentration. Finally, non-stationary extreme value analyses were applied in order to assess wind and wave extremes taking into account climate change and seasonal cycles in the estimations. Such an approach becomes essential for the evaluation of extreme environmental variables in the Arctic, where the seasonal sea ice coverage and the ice retreat affect the stationarity of the sea state directly. The results show notable seasonal changes and a consistent increase in extreme waves with the largest increasing rates in the Beaufort and East Siberian seas of approximately 60% in areal-average of 100-year return period for significant wave heights over the past decades. At the same time, extreme winds have only increased by 4% in some regions. Therefore, the changes in extreme winds cannot explain the changes in extreme waves. These results make evident that the sea ice melting has primary responsibility for these dramatic changes in extreme waves.
Particle-scale study of heat transfer in granular geomaterials
The effective thermal conductivity of granular geomaterials is the one of the most important parameters in some geotechnical and reservoir engineering applications. Various effective thermal conductivity models have been developed over the years, aiming to predict effective thermal conductivity accurately. However, these models usually predict effective thermal conductivity that are different from the experimental measurements. This may be due to the limited access to the material microstructure and thus limited understanding of its effects on the macroscopic or ‘engineering’ effective thermal conductivity. With the advent of computed tomography and complex network theory, digital samples can be reconstructed based on high-resolution computed tomography images and then microstructure of the samples can be quantified at multiple length scales. At the microscale, three-dimensional sphericity and roundness are selected in this work to describe particle shape based on a critical examination of the literature. They are calculated for each particle in different sands using an in-house developed code. Mesoscale parameters, perhaps with the exception of ‘coordination number’, are still scarcely used in engineering. This issue is addressed by representing the granular materials as either contact networks or thermal networks and applying complex network theory to obtain new mesoscale parameters that characterise the granular assemblies. A network consists of nodes and edges. Specifically, in the contact network, a node represents a particle and an edge means an interparticle contact. Since heat transfers through not only interparticle contacts but also the ‘small’ gaps between adjacent particles, the contact network can be extended to a thermal network by considering the ‘small’ gaps as new edges. The complex network features extracted from these networks can capture the information of particle connectivity or/and contact quality which are essential to heat transfer. Results show that granular geomaterials with higher average sphericity or roundness can render a higher effective thermal conductivity because the two particle shape descriptors have a positive correlation with average coordination number and interparticle contact radius ratio (i.e., the ratio of the equivalent radius of interparticle contact area to the particle radius). Different types of network features can characterise the microstructure from diverse aspects. For examples, the degree is related to contact number, closeness centrality is about the average distance between particles, and betweenness centrality describes the role of a node or edge acting as a ‘bridge’. Many network features can be used as predictors of effective thermal conductivity, especially the features weighted by contact area in the contact network or by thermal conductance in the thermal network. In this work, a single weighted network feature that considers both particle connectivity and contact quality have shown a strong correlation with effective thermal conductivity of different granular materials either generated by discrete element method or digital sands. Some examples of these single features include weighted degree and weighted closeness centrality. The implementation of various advanced tools makes access to microstructure becoming readily and promote a data-driven approach to build effective thermal conductivity models automatically without subjective bias. The multiple characterisations and correlations determined through the thesis allow to rigorously select the input parameter(s) for an artificial neural network model with the capability of predicting the effective thermal conductivity with high accuracy and computational efficiency. The proved feasible data-driven framework from this thesis offers a new paradigm for effective thermal conductivity prediction.
Rigid Barrier with a Gabion Cushion Subjected to Boulder Impact
Protection against rockfalls occurring alongside landslides contribute to the major part of the disaster management budget in many counties like Switzerland, Japan and Hongkong. Protective structures are usually built over disaster trajectories to safeguard lives and properties. Reinforced concrete barriers that are fitted with gabions are one common form of installations to provide the protection. Few experimental investigations involving impact testings of a rigid reinforced concrete barrier which was fitted with a gabion cushion cover have been reported in the literature. But these investigations were limited to studying the localised actions of impact. The change of structural response behaviour of the barrier as a whole by the presence of a cushion layer is typically not within the scope of the reported investigations. Design methodologies that have been developed are typically limited to overly simplified calculations based on applying an equivalent static force to the barrier. To fill this knowledge gap full-scale pendulum tests have been conducted by the authors on a barrier that was fitted with a gabion cushion layer. The structural response behaviour of the barrier, contact force and tensile strains in the longitudinal reinforcement were of interests. Results recorded from the tests were compared with results from control experiments which were without the protection of any cushion materials. The introduction of a layer of cushion is shown to be able to have the deflection demand on the structure reduced by more than 70% when the amount of energy delivered by the impact is kept constant. An analytical procedure employing the Hunt and Crossley contact model, Swiss code model and two-degrees-of-freedom (2DOF) system modelling technique is presented for evaluating the flexural response demand behaviour of the cushioned barrier. The proposed analytical procedure is shown to be able to predict the reduced deflection demand with a reasonable degree of conservatism. At the end of the thesis, a simple hand calculation procedure featuring the use of design charts is presented for engineering applications. The procedure is illustrated by a worked example which is based on a realistic rockfall scenario.
Wind-wave extremes in a changing climate from atmosphere and wave model ensembles
Marine offshore structures and operations, as well as coastline defences, rely on accurate estimates of the design sea state, defined as the maximum significant wave height which can be expected over an N year period. To find design sea state estimates, Extreme Value Analysis (EVA) statistical approaches are commonly used. However, due to the paucity of data available for extreme sea states, and the consequent challenges in modelling such phenomena, design sea state estimates are characterized by large confidence limits, which further complicate strategies and policies for resilient design of marine structures and operations. Furthermore, an additional challenge is posed by a changing climate, which introduces further uncertainties in the prediction of future design sea states. The present work deals with the EVA statistical uncertainties of ocean surface wind speed and significant wave height, developing and testing a novel ensemble approach to EVA. It then applies this novel approach to estimate future changes in extreme significant wave height by the end of the 21st Century. In this way, the present thesis finds, for the first time, statistically significant changes in extreme wave height in distributed regions of the ocean. Such an approach has the potential to be further refined with higher resolution models and new climate model projections, which would significantly improve global estimates both from past and future model ensembles. In parallel, this work finds an inconsistency in the trends of wind and wave mean climate throughout the 20th Century from climate models and reanalyses, questioning our confidence level as to a possible climate change signal for ocean surface wind speed and wave height. However, the work finds general agreement between datasets and statistical approaches, for a Southern Ocean wind speed and wave height increase over the last part of the 20th Century, that is also projected to further increase by the end of the 21st Century.
Mechanobiological investigation of bone fracture healing under Ilizarov circular fixators
Ilizarov circular fixator (ICF) is an external bone fixation device used by orthopaedic surgeons in treating variety of bone defects. Despite the fact that ICFs are being used for over seven decades, the interplay between ICF mechanics and biology of fracture healing remains poorly understood. The roles of ICF configurations on processes within the fracture site during fracture healing such as cell differentiations, solute (e.g. cell, growth factors etc.) transport and angiogenesis have not been explained well yet. Furthermore, how the interplay between ICF and other mechanical factors such as fracture geometry and loading affect these processes remains unclear. This knowledge gap in the mechanobiology of fracture healing under ICF is a barrier to address clinical problems associated with ICFs. Consequently, treatment failures and complications are significant with ICF treatments (around 10 – 30 %). This thesis intends to address this knowledge gap by conducting systematic mechanobiological investigations of fracture healing under ICFs. In this research, various computational models to simulate various aspects of fracture healing under ICFs were developed. In developing the models, various novel methodologies and modelling techniques were adopted. Firstly, unlike in most previous studies, a fully coupled fracture healing prediction model of fractured bone stabilized with ICFs, including soft tissues and mechano-regulation was developed to simulate early stage mesenchymal stem cell (MSC) differentiations. Secondly, a model combining both mechano-regulation and bio-regulation was implemented to simulate healing of fractures stabilized with ICF under dynamic loading. Thirdly, a new regulatory model considering level of vascularity and local tissue strain was proposed and implemented to simulate angiogenesis and fracture healing under ICF. Finally, a methodology using computational modelling in conjunction with engineering reliability analysis was implemented to investigate the role of uncertainties in mechanical parameters on fracture healing under ICFs. All computational models were developed based on the theory of porous media and continuum mechanics. The models were first validated using experimental data and subsequently used for fracture healing predictions. Mechanical experiments involving measurement of bone interfragmentary movements (IFM) using an advanced 3D optical measuring system (ARAMIS) were conducted in this research for model validation purposes. Wherever possible, the predictions of the models were corroborated by experimental and clinical data. Through systematic analyses, this thesis contributes to the existing body of knowledge by providing new insights into the mechanobiology of fracture healing under ICFs. This thesis elucidates the following mechanobiological aspects of fracture healing under ICF that have not been systematically studied so far: 1. The effects of ICF configuration, loading and fracture geometry on the early stage mesenchymal stem cell (MSC) differentiations during fracture healing; 2. The roles of physiologically relevant dynamic loading on cell differentiations and cell / growth factors transport within the early stage fracture site; 3. The effects of subject specific factors (i.e. body weight, fracture geometry and ICF configuration) on angiogenesis and optimal time dependent weight bearing levels for bone fractures treated with ICFs; and 4. The effects of uncertainties in mechanical factors (i.e. fracture geometry, weight bearing and ICF configuration) on fracture healing under ICF. In addition, the models presented in this thesis could potentially be used for further systematic investigations and in clinical settings for designing and comparing ICF treatment strategies.
An integrated method for groundwater vulnerability assessment using a DRASTICL model and a green algae ecotoxicity test
The world population could reach 9.8 billion by the year 2050 (UN, 2019). The rising world population presents the challenge of water and food security for human development. As a result, excessive use of agricultural chemicals (both fertilisers and pesticides) which in most cases are toxic not only for the humankind but also for the environment, is putting significant stress on the groundwater levels and the water quality. Groundwater (GW) pollution from agriculture is particularly significant in partially and totally groundwater-dependent ecosystems, as these ecosystems provide habitat for various endangered flora and fauna. Even though the importance of GW systems is well recognised, groundwater pollution vulnerability assessment models and groundwater pollution quantification techniques have experienced slight changes over the last 10 years and in most cases, the use of agricultural chemicals is assumed to be safe in the absence of sufficient data and evidence. The existing models produce an annual GW Vulnerability map and there is little to no monitoring of groundwater for these chemicals due to difficulty with identifying the representative samples and the high analytical cost. Therefore, this thesis aims to develop a novel approach to understand the seasonal variations in groundwater vulnerability and used the modified model to identify the representative sampling bores and also explores an algal ecotoxicology test as for the pesticides in water, that can be used as a fast and inexpensive pre-screen to identify samples above a certain level of toxicity for detailed chemical analysis.
Shallow geothermal systems: individual and district applications
Worldwide energy use is expected to rise due to an increase in population and global warming. About half of this energy use is for space heating and cooling for buildings, where electricity (mostly derived from fossil fuels) and natural gas are the most common sources of energy. To achieve long term energy sustainability, electricity and natural gas consumption needs to be reduced. One way to achieve this reduction is by utilising shallow geothermal system or ground source heat pump (GSHP) system technology. This technology utilises the ground as a heat source or a heat sink to provide sustainable heating and cooling for buildings. The use of this technology has been growing worldwide. However, information and high-quality datasets of GSHP systems are still rare in Australia, leading to installations with low efficiency and high installation costs. This research aims to contribute to the understanding of GSHP systems under Australian climatic, cost and emission conditions, including how to improve their viability and uptake. The first part of this research aims to address this lack of availability of quality datasets. To do this, a full-scale monitoring project was undertaken. This thesis presents the performance data from 10 monitored residential and small commercial GSHP system installations in the greater Melbourne area. The measured data reveals that a GSHP system can perform well under Melbourne climatic condition, with an estimated coefficient of performance between 2 and 4.9. One common trend in all of the monitored properties is that they are used only around 10 to 20% of the year, which is much smaller compared to the expected usage based on typical design methods. For this reason, a more detailed comparison was conducted for two properties with the lowest and highest system usage. The comparison indicates that the differences in the usage patterns imposed by the occupiers can significantly impact the potential cost-effectiveness and environmental benefits of the GSHP system. This suggests that in general, a GSHP system can be an alternative heating and cooling options under Melbourne climatic and geological conditions, but they have to be designed, installed and used appropriately. Otherwise, this may lead to an inefficient system with a long payback period. One potential explanation behind the moderate GSHP system usage described above is the temperate climatic conditions of Melbourne, which requires only moderate heating and cooling. For these conditions, a hybrid combination between GSHP and conventional systems may be preferred to maximise the benefits from both systems. A hybrid GSHP (HGSHP) system means a GSHP system that is sized to provide the baseload thermal energy for a building and this system is supported by a conventional system during the hottest and coldest days of the year. This leads to the next part of this research where an HGSHP system design method is proposed with the objective that considers both costs and emissions by using a Pareto optimum approach. This analytical study is extended to cover different climatic, cost and emission conditions across several Australian cities. The results reveal that HGSHP systems can have a lower lifetime cost than GSHP or conventional systems. However, this hybrid system mix with the lowest lifetime cost is not necessarily the same as the one with the lowest lifetime emission. Overall, this research may provide a basis on which decisions about whether to install an HGSHP system with the objective to minimise their lifetime costs or emissions. A solution which considers both factors with equal weight is also provided herein. The last part of this research considers the possibility to combining several individual HGSHP systems into a district arrangement. This is called a district HGSHP system and this is possible because buildings are located close to each other in the urban area. The results indicate that district HGSHP systems can reduce capital and operational costs compared to individual HGSHP systems. The highest financial savings occur when buildings with significantly contrasting thermal load patterns are combined together, for example, combining heating dominant with cooling dominant buildings. Combining more buildings lead to higher financial savings, but this follows the law of diminishing returns. Altogether, the findings from each chapter are expected to contribute incrementally to improving our knowledge of GSHP system technology as well as providing more real-life performance data. The insights from this research may also be applicable to other locations with similar climatic, cost and emission conditions. Further, based on the outcomes of the work covered in this thesis, stakeholders may be able to make more informed decisions on design, installation and operation of GSHP systems. These should also allow the development of more appropriate public policy to encourage the growth of the shallow geothermal industry.
Development of Advanced Timber-based Prefabricated Panelised Systems
This thesis aims to develop advanced timber-based panelised prefabrication in an impactful manner. The research approach involved the establishment of close collaborative industry-partnerships which were then leveraged to best satisfy the critical needs faced in industry, resulting in targeted in-depth advancements across a range of areas. Five core areas for detailed advancement were identified, namely: manufacturing processes, waterproofing, wall systems, design methods (including optimal configuration selection) and floor systems. Within each core area, the pressing limitations of most immediate commercial need were investigated and addressed in detail. Consequently, the original contributions to knowledge are as follows: - Full evaluation and assessment of advanced automated manufacturing technologies and processes available for complete timber-based panelised systems; - Development and successful commercial adoption of a purpose specific prefabricated panel to panel waterproofing solution to replace on-site work; - Development and implementation of a significantly more material and cost-efficient panelised timber-based wall system for mid-rise buildings, namely stiffened engineering timber walls with post-tensioning; - Corresponding mathematical modelling via the computationally efficient exact finite strip method based upon the Wittrick-Williams algorithm with appropriate orthotropic material models and strength limits; - Development of associated design curves, configuration specific post-tensioned strength reduction factors and optimal configuration selection methods; - Development of a panelised stressed-skin timber floor system through reductive-design with increasing material efficiency whilst also reducing the number of manufacturing processes required for competitive commercial adoption. As a result, this development of knowledge, process and product innovations, is spurring and enabling the growth of research in, and industry adoption of, advanced timber-based panelised prefabrication.