Civil Engineering - Theses
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ItemNo Preview AvailableEffect of land surface heterogeneity on satellite near-surface soil moisture observations(University of Melbourne, 2009)This thesis develops a technique to reduce the error in near-surface soil moisture estimates from spacebome passive microwave sensors, by accounting for the heterogeneity of land surface conditions within the sensor field of view. Using experimental data collected in the course of this research, it is demonstrated that this technique will significantly reduce the error in satellite near-surface soil moisture retrieval. The technique has been developed specifically for the first dedicated passive microwave soil moisture satellite, the European Soil Moisture and Ocean Salinity Mission (SMOS), which will use L-band (1.4GHz) measurements to map nearsurface soil moisture globally at a near-daily time scale. The main steps taken to develop these techniques are the first evaluation of the core radiative transfer model of the SMOS soil moisture retrieval algorithm for the Australian conditions using airborne data, and an analysis of the land surface controls on near-surface soil moisture distribution at the satellite footprint scale. These initial steps provided the tools in order to test the accuracy of the soil moisture retrieval approach proposed for SMOS at the satellite footprint scale in the presence of spatial variability of the land surface, and to develop a new retrieval approach for SMOS which overcomes the shortfalls identified in the SMOS proposed approach.
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ItemAddressing uncertainties associated with water accounting(University of Melbourne, 2009)Water accounts provide information to a range of stakeholders who make decisions related to water. There are significant challenges in quantifying all of the information elements included in water accounts. Some information elements are measured while others are estimated. There is uncertainty associated with the information presented in water accounts, either due to measurement uncertainty or the assumptions made during the estimation process. The presence of uncertainties in water accounts poses two problems. Firstly, the decisions made based on information presented in the accounts may change if the associated uncertainties were disclosed. Secondly, due to the uncertainties associated with each element, the accounts rarely balance. At present the uncertainty in water accounts is not well understood and it is not systematically captured and reported in the accounts. This thesis identifies and quantifies the major sources of uncertainty in water accounts. Established techniques to quantify the uncertainties are only available for a few of the elements. A number of new techniques are developed to quantify the uncertainty associated with elements that include unmetered water use, net evaporation from storages, reservoir volumes and impacts of farm dams. A general framework to quantify uncertainties is developed and applied to a case study, the Werribee River basin (Victoria, Australia). The largest uncertainties in this catchment are associated with estimating rainfall runoff and surface water -groundwater interactions. A new method to constrain the uncertainty associated with each component of the water accounts and to create a balanced set of accounts, based on numerical data reconciliation, is presented. If the uncertainty surrounding each element is known, it is possible to improve the estimates and reduce the uncertainties by removing combinations of inflows and outflows that do not create a balanced set of accounts. Existing analytical techniques to perform the required calculations for data reconciliation are not suitable in water accounting because they assume that all uncertainties can be described using a Gaussian distribution. In order to incorporate other types of probability distributions, a numerical technique is developed. Overall, this thesis presents three new contributions: an identification of information elements which are useful to decision makers; a quantification of uncertainties associated with the elements reported in water accounts and methods are presented to quantify these uncertainties; a new numerical method, data reconciliation, to minimise the uncertainties by considering the joint probability of all inflows and outflows that create a balanced set of accounts.
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ItemA hybrid microsimulation model of freight transport demand(University of Melbourne, 2009)
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ItemA study of aerodynamic wind loads on tall buildings using wind tunnel tests and numerical simulations(University of Melbourne, 2009)
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ItemPricing carbon in power sector investment : a stochastic decision tree analysis(University of Melbourne, 2007)
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ItemIntersectoral water allocation : valuing water and the case for water property rights(University of Melbourne, 2006)
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ItemFurther understanding ground source heat pump system design using finite element methods and machine learning techniques( 2018)Ground-source heat pump (GSHP) systems can efficiently provide renewable energy for space heating and cooling. Even though these systems have shown great potential, contributing towards the continuously increasing energy demand and reducing greenhouse gas (GHG) emissions, our understanding of how they can be best utilised and designed can still be improved. This research adopts detailed numerical modelling and statistical approaches to provide further insights on these systems and contribute towards their worldwide adoption, focusing on three main areas. Firstly, due to the nature of their installation, there can exist disparities between the designed and installed systems. One such design-installation disparity, variable geothermal pipe separation, is addressed, aiming to reduce the gap between theory and practice. Secondly, due to the relatively recent emergence of energy geo-structures, such as energy piles or retaining walls, there currently exists little information on their utilisation/design. Therefore, an in-depth numerical analysis on energy geo-structure thermal performance is provided, focusing on the less well-researched energy retaining walls and providing suggestions on important factors such as the thermal demand, structure geometry and pipe configuration. Finally, two statistical approaches are presented that complement numerical modelling (often adopted for energy geo-structure analysis) and significantly reduce the computational time/resources associated, making numerical analysis and design of GSHP systems more accessible to engineering practice.
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ItemDesign optimisation for off-site manufacture and assembly of MEP systems( 2018)Modularisation and Standardisation for prefabrication of mechanical, electrical and plumbing (MEP) systems have become more prevalent during the last decade with the growth of the prefabricated construction industry. Speedy construction, minimum onsite labour, improved quality and waste reduction are the key benefits that make prefabrication superior to conventional construction. However, in MEP, modularisation and standardisation are currently applied only to smaller systems, where integrated packaged units are used in heating, ventilation and air conditioning (HVAC) and other building services installations. Modular prefabrication is rarely practiced when services are located within the building due to limitations during installation and difficulty in coordination. The term ‘optimum modularity’ is not accurately used in the field, and identification of modules is solely based on individual judgement than a structured method. The absence of a structured method for modularisation in MEP has made the identification of modules for prefabrication a time-consuming process, that often fails to achieve the optimum module division with minimum installation cost. In most cases, this has resulted in modular prefabrication of MEP being the same cost as conventional construction or even higher. This is one of the main reasons that impedes the use of modular prefabrication in the MEP industry. Therefore, this research has formulated an algorithm for optimum module identification in MEP systems, considering the installation cost and the functional requirements of the system. The structured modularisation process developed in the thesis, identifies the optimum module configuration to achieve minimum installation cost, while satisfying the installation and operation constraints of MEP systems. This method assists engineers and researchers to evaluate the benefits of a modular configuration compared to conventional site build strategy, prior to implementing prefabrication in MEP projects. In order to achieve these objectives, three case study project sites were visited during the construction period to identify the constraints in MEP construction and aspects to consider in the modularisation process. Chilled water central plants are chosen for the development of the modularisation algorithm, due to its complex installation process and popularity in the industry. This practical insight into the development of the method ensures that the configurations generated using the algorithm are practically constructable onsite. Structured modularisation methods practiced in various manufacturing industries such as Aerospace, Automotive, Shipbuilding and Consumer electronics were studied to identify their applicability to the construction industry. The developed structured modularisation method presented in this thesis is the only study available to date in literature, that takes an algorithmic approach to modularisation in the construction industry. An automated process of module identification, using a combination of fuzzy logic, Dependency Structure Matrix (DSM) and Hierarchical Clustering and Partitioning Algorithm (HCPA) have minimum human intervention, where input data is extracted from the Building Information Model (BIM). This leads to significant time and cost savings during the design and construction stages of MEP systems. Although the development of the algorithm was based around chilled water plant construction, the methods proposed in this thesis can be used for modularisation of other MEP central plants, such as generator, transformer and pumps, with further research on limitations and assemblies associated with a particular system. In addition to a structured method for modularisation, design engineers and researches would also require a model to evaluate the benefits of modular over conventional construction. In this regard, the output of the developed algorithm estimates the installation cost of the optimum configuration and compare the cost benefits with the conventional case, prior to implementing modular construction in MEP projects. This thesis provides a comparison of the modular approach to conventional construction, to identify a hybrid strategy to MEP plant construction. Furthermore, recommendations are provided to implement this research in other disciplines in the modular construction industry.
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ItemCollective movement of merging pedestrian crowds( 2018)Modelling pedestrian crowd movement and behaviour has emerged in the recent years in the literature as a new research topic. This topic has become important to an increasing extent due to the growth of populations of urban areas and mass events as well as an increase in the frequency of crowd-related incidents in venues that host a large number of people. Emergency incidents are considered as infrequent occurrences with safety-related ramifications and probable high effect. Although some attempts of modelling and simulating pedestrian movement have been around for decades, this field of research has recently received an apparent boost in attention in a variety of disciplines, notably in transport. The research on this subject eventually intends to develop forecasts tools that could assist in planning and optimisation for evacuation situations by providing measures including total evacuation times for each given circumstance. This would facilitate planners and authorities with the useful information required for evaluating the efficiency of their evacuation strategies in terms of time takes to vacate venues, placing potentially problematic locations and identifying weaknesses in their venues and recommend measures that can expedite the discharge of individuals should normal or emergency evacuation arise. Applications of these prediction tools could range vastly from merely guiding occupants as to in what way they should behave and manage themselves in case of occurrence of an incident, to assessing the safe density rate of venues especially in large special events and mass gatherings, too complicated optimising the design of the environments in ways that best increase the efficiency with which individuals move. The interdisciplinary problem has drawn the attention of researchers in numerous fields such as applied physics, fire safety, mathematics, ergonomics and transport engineering. The most critical element of this practice is potentially the accurateness of modelling that is inextricably linked with the behaviour of humans and extent to which their behaviour can be replicated by the proposed models. Considering implications of evacuation prediction tools and models in terms of safety, it is of major importance to reduce the possibility of imprecise estimates that could possibly culminate in inaccurate designs or misguided management policies. In order to address the challenges involved in reproducing pedestrian crowd motion, broad research has been undertaken. As stated by literature, however, most of studies has centred on understanding a class of models which we refer to as “walking-behaviour” or “next-step” models. In contrast, there has been very little knowledge as to the understanding of a higher scale of pedestrian decision making which we refer to as “route/exit” choice. Implementation of some plausible criteria which can reproduce peoples’ exit decision in an egress situation while taking into account the dynamic changes of the exit characteristics would be part and parcel of any simulated evacuation from a geometrically complex facility. I state that the experimental information in this field of research has dropped behind the mathematical progressions and model specifications. Therefore, more extensive empirical research and experimental studies in this topic are required in order to bridge this existing gap. Also, by exploring the current empirical literature, it can be concluded that the research in this field has been distributed in a comparatively unbalanced way in terms of addressing a variety of factors influencing on humans’ movements pattern. More empirical insights have been obtained related to the walking behaviour of individuals, particularly in simple experimental layouts. However, the impact of space particularly complex architectural settings on individuals’ interactions are relatively less explored. investigating this effect experimentally pose additional levels of difficulty for data collection, data extraction and drawing behavioural insights. Whereas, it is evident that acquiring a precise and comprehensive understanding of this impact and developing behavioural models that are capable of capturing this effect is of paramount importance. This research is proposed to address some of the knowledge gaps we identified with respect to the impact of space on movement dynamics of human crowds under the various level of stress. To our knowledge, the literature lacks an extensive understanding as well as robust models of the effect of geometrical features of movement area on movement pattern of individuals for egress situation. Therefore, this study primarily aims to provide an understanding of this effect particularly presence of merging corridors on egress behaviour through the provision of data obtained from a vast number of experimentations which is called for in the literature. Novel conditions and experimental layouts are to be considered as well as an advanced micro-level/ macro-level analysis are to be performed to elicit individuals’ behaviour. In addition, we analyse and present the observed interactions between occupants and their surrounding environment in a way that could be utilised for various mathematical models and simulation tools. I investigate the problem utilising two sources of experimental observations: data gained from non-human experimentation and data extracted from field-type experiments in controlled laboratory conditions with human subjects. Animal experiments data was collected by utilising panicked ants as experimental subject evacuating from various conflicting layouts. The impact of physical factors of movement environments on dynamics of the crowd was imitated in real actions where occupants were required to interact with their surrounding areas while evacuating under various levels of emergency. Their movement pattern was extracted at the level of individuals from raw footage of pedestrians. Data obtained from both sets of experiments were analysed undertaking macroscopic and microscopic measurements. While the above-mentioned problem is the primary purpose of this research, as a second question, this proposed study also intends to investigate the effect of the level of emergency on evacuees’ discharge behaviour in terms of observing “faster is slower “phenomenon. There are some merely simulated approaches as well as experimentation with non-human subjects proposed in the literature suggesting “faster is slower “ phenomenon under an emergency condition, validation of which have been primarily impeded by the scarcity of reliable explanatory data. Furthermore, to our knowledge, the impact of architectural design of egress area particularly presence of merging corridors on evacuation behaviour of the crowd has been barely examined in connection with the level of vigour to evacuate. Although the scarcity of pertinent data will still hinder us to address this problem under the extreme level of emergency situations, this study proposes some experiments under which the effect of extreme conditions is to be explored to bring to light any potential difference between the impact of space on evacuees’ behaviour under normal and emergency conditions The connection recognized between the findings obtained from experimentation with non-human organisms and humans also provided motivating insights into how the influence of the presence of conflicting layouts particularly merging corridors on the collective movement of non-human organisms is similar to that effect on the motion of human subjects. This connection led to findings that not only did offer insight into the possible relevance of collective behaviour of non-human subjects to what human occupants do in escape scenarios.
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ItemBuildings featuring irregularities in the gravity load carrying frames in low-to-moderate seismicity regions( 2018)The need of building to have column-free space at certain storeys due to architectural and aesthetical reasons, or a change in the functionality of adjacent storeys and building facility requirements, explain why many buildings feature irregularities in their gravity load carrying frames. However, discontinuities in the load-bearing system may result in unfavourable failure mechanisms under severe earthquake excitations. These buildings commonly exist in low to moderate seismic regions, like Australia; given that strict regulations do not exist with respect to earthquake resistant design of buildings. Furthermore, in these regions buildings typically have non-ductile detailing and are therefore prone to brittle and sudden failures. There is a growing need to assess the performance of vulnerable buildings in low to moderate seismic regions as it has been acknowledged that these regions are exposed to the risk of rare occurrence of devastating and damaging earthquakes. This research aims at investigating the seismic performance of a class of vertically irregular buildings in regions of low to moderate seismicity in order to provide a broad and comprehensive understanding of their response behaviour. Owing to the importance of vulnerability assessment of buildings featuring the use of transfer beams in the gravity load carrying frames (discontinuity or off-set in the load path), linear and nonlinear response behaviour of this class of buildings have been investigated thoroughly. Although “gravity frames” are assumed only to carry vertical loads, the effects of their lateral strength and stiffness need be taken into consideration in the seismic analysis. Results of studies revealed that the elastic response behaviour of vertically irregular buildings is consistent with regular buildings in terms of stiffness, modal periods, modal shapes, and lateral displacement and shear force profiles. Hence, stiffness irregularity (as a consequence of discontinuity) may not develop in the elastic range. An analysis method is known as the Generalised Force Method (GFM) which has been developed to remedy the shortcomings of the Equivalent Static Analysis method is introduced. This method is not subject to height range restrictions and is applicable to buildings that may have eccentricity, and/or transfer beam irregularity. A technique for the modelling of limited ductile beam/column components based on the concentrated plasticity modelling method has been proposed and used to develop the nonlinear models. Damage mechanism, failure patterns and weak regions of these buildings have been investigated using nonlinear analysis methods, and finally, response modification factors have been calculated for these buildings. It has been shown that a weak storey in the cases where the contributions from moment-resisting frames are high can be developed as a consequence of shear failure in the transfer beam. The behaviour of limited ductile shear walls or non-ductile columns governs the seismic behaviour of these buildings. Failure of walls due to the lack of boundary elements may occur as a result of poor detailing. However, shear failure in the transfer beams may also occur prior to the failure of walls in some cases. Hence, to avoid undesirable seismic performance behaviour such as weak storey collapse mechanism (due to the shear failure of transfer beams), more complicated methods of analysis might not necessarily result in a more desirable outcome. Ductility factors for the buildings investigated have been found to be less than 1.5. Hence, current detailing practice may not ensure a ductility value of 2.0 in compliance with AS117.4:2007, even for the regular buildings. The ductility factor for certain irregular buildings which typically has higher contributions from moment-resisting frames to the lateral stiffness have been found to be close to 1.0; which reveals the concentration of plasticity in the critical elements while elastic response behaviour is experienced with the other elements. Hence, the structure is almost entirely elastic at the onset of developing a mechanism. Guidelines and recommendations for the design of a new building in the form of designation of applicable analysis methods for these buildings and response modification factors are provided in the thesis. A straightforward method for the seismic assessment of limited ductile shear wall dominant buildings has been recommended. The method uses a rational approach to predict the nonlinear response behaviour of a given building by modifying the stiffness of individual members of an elastic model for the building structure. Moreover, a probabilistic rapid assessment tool for generating fragility curves is proposed for these buildings. This tool can be used for obtaining information for the risk assessment studies, by providing a simple and rapid method to assist global decision makers.