Civil Engineering - Theses

Permanent URI for this collection

Search Results

Now showing 1 - 10 of 37
  • Item
    No Preview Available
    Effect of land surface heterogeneity on satellite near-surface soil moisture observations
    Panciera, Rocco. (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.
  • Item
    Thumbnail Image
    Addressing uncertainties associated with water accounting
    Lowe, Lisa Diane. (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.
  • Item
  • Item
    Thumbnail Image
    A hybrid microsimulation model of freight transport demand
    Donnelly, Richard Ren�. (University of Melbourne, 2009)
  • Item
  • Item
    Thumbnail Image
    Intersectoral water allocation : valuing water and the case for water property rights
    Glennie, Paul Rog�r. (University of Melbourne, 2006)
  • Item
    Thumbnail Image
    Intersectoral water allocation : valuing water and the case for water property rights
    Glennie, Paul Rog�r. (University of Melbourne, 2006)
  • Item
    Thumbnail Image
    Evaluating and reducing exposure to indoor pollutants from volatile organic compounds
    Goodman, Nigel Byron ( 2019)
    Indoor air pollution now ranks as a top environmental health risk globally. Poor indoor air quality can detrimentally affect human health and the economy. Volatile organic compounds (VOCs) are pervasive indoor air pollutants. The major objectives of this research are to evaluate what is known about indoor VOCs, to understand what the typical VOCs people are exposed to within indoor environments, and to assess ways to reduce exposures and effects of indoor VOCs. First, this research systematically evaluates 25 years (1991–2016) of investigations of VOCs within indoor environments in Australia. Among 31 papers evaluated, the most frequently studied environment was domestic housing (61%), and the most frequently quantified compound was formaldehyde (81%). Active sampling techniques were used in 82% of studies of benzene, toluene, ethylbenzene, and xylene (BTEX), and in 38% of studies of formaldehyde and other carbonyls. New homes had the highest VOC levels among all studies of domestic housing. For nearly all pollutants, indoor levels were several times higher than outdoor levels. Among the most prevalent compounds indoors were terpenes, such as d-limonene and α-pinene. All studies were conducted at a regional or local level, and no study reported statistically representative indoor VOC data for the Australian population. The evaluation revealed a diversity of sampling approaches and techniques, pointing to the importance of a standard approach for collecting and reporting data. Second, this research investigates volatile organic compounds (VOCs) at a large Australian university, within locations of campus services, restrooms, renovated offices, a green building, meeting areas, and classrooms. Analysis of 41 VOCs across 20 locations revealed indoor concentrations higher than outdoor concentrations for 97% of all VOC measurements (493 unique comparisons). Hazardous air pollutants (formaldehyde, benzene, toluene, and xylenes) were up to an order of magnitude higher indoors than outdoors, and at the highest combined geometric mean concentrations in classrooms (51.6 µg/m3), renovated offices (42.8 µg/m3), and a green building (23.0 µg/m3). Further, d-limonene, ethanol, hexaldehyde, β-pinene, and isobutane were up to two orders of magnitude higher indoors than outdoors. The most prevalent VOCs (e.g., ethanol, d-limonene, and formaldehyde) have links with building materials, furnishings, and fragranced consumer products such as air fresheners and cleaning supplies. Highest indoor to outdoor concentration (I/O) ratios of formaldehyde (27), toluene (9), p-xylene (12), and m-xylene (11) were in a green building; highest of benzene (6) in renovated offices; and highest of o-xylene (9) in meeting areas. Although indoor concentrations of hazardous air pollutants (i.e., benzene, formaldehyde, toluene, xylenes) were higher indoors than outdoors, the indoor concentrations are nonetheless lower than applicable World Health Organisation guidelines. Results from this study are consistent with findings from similar international studies and suggest that university indoor environments may be important sources of pollutants. Third, this research investigates volatile emissions from six residential dryer vents, with a focus on d-limonene. It analyses and compares concentrations of d-limonene during use of fragranced and fragrance-free laundry products, as well as changes in switching from fragranced to fragrance-free products. In households using fragranced laundry detergent, the highest concentration of d-limonene from a dryer vent was 118 µg/m3 (mean 33.34 µg/m3). By contrast, in households using only fragrance-free detergent, the highest concentration of d-limonene from a dryer vent was 0.26 µg/m3 (mean 0.25 µg/m3). After households using fragranced detergent switched to using fragrance-free detergent, the concentrations of d-limonene in dryer vent emissions were reduced by up to 99.7% (mean 79.1%). This simple strategy of switching to fragrance-free products significantly and almost completely eliminated d-limonene emissions. Results from this study demonstrate that changing from fragranced to fragrance-free products can be a straightforward and effective approach to reduce ambient air pollution and potential health risks. In summary, this research identified primary indoor air pollutants and understudied locations. It evaluated indoor air quality at a university and provided evidence that green and renovated buildings may not necessarily guarantee improvements for indoor air quality. It assessed an approach to reduce VOC emissions in residences and demonstrated that significant reductions were possible. In conclusion, this research provides novel scientific findings that can help improve indoor air quality both in Australia and internationally.
  • Item
    Thumbnail Image
    Impact-resistance of Reinforced Concrete Structures
    Yong, Arnold Cheng Yee ( 2019)
    Reinforced concrete (RC) protective barriers such as rockfall barriers and vehicular barriers need to be designed to resist impact actions. However, there are uncertainties over the required stability of the barrier to withstand the impact forces predicted for the projected impact scenarios. A critical review of the literature covers a range of methods for estimating the impact action imposed by a hard impactor on RC members. Those methods providing estimates of the peak impact force occurring in a transient manner at the point of contact between the boulder and the surface of the RC member, or cushion material placed in front of the member, are classified as force-based (FB) methods, whereas methods providing estimates of the displacement of the target, or a quasi-static force corresponding to the estimated displacement demand, are displacement-based (DB) methods. The FB methods have gained useful insights into protection of the barrier from localised damage. However, the destabilising effects and other global effects (of bending and shear) of the impact action are preferably estimated by DB methods. Fundamental distinctions between the two classes of methods, and different types of forces generated by an impact have been explained in the literature review. Overly conservative estimates of the destabilising action of an impact can be resulted if the peak impact force is applied in a static manner to the model of the barrier (the target). The DB model that has been developed at the University of Melbourne is less conservative than existing codified models and has been verified by comparison with results from laboratory experimentation. The model has also been shown to give estimates of the bending moment of a simply supported beam that are consistent with recommendations by the CEB (Euro-International Concrete Committee) model. The primary objective of this project is to develop simple analytical models for assessing the global response behaviours of a RC rigid barrier when subjected to hard impact, including overturning, sliding and bending. These models were developed based on the same underlying DB methodology, but take different forms depending on the type of response. In a conventional FB design procedure wherein the impact action is represented by an equivalent static force, the demand on the stability of the barrier increases with its height because of the higher overturning moment that has to be resisted. There are significant costs implications associated with this design methodology and more so in cases where a deep (piled) foundation is required to resist the overturning moment transmitted from a tall barrier. An alternative design approach based on equal energy and momentum principles as proposed in this thesis predicts a higher factor of safety against overturning with a taller, free-standing, barrier when the base dimensions are kept the same. The free-standing approach to design saves costs as the need of a deep foundation is eliminated and stresses within the barrier is always lower when the base is free to rotate. This alternative design approach has been verified by results from systematic physical and simulated impact experimentation. When space is limited, sliding action of the barriers become a key design consideration. By employing the DB methodology, an analytical model in the form of a closed-form expression has been developed for estimating the amount of sliding displacement of a barrier when struck by an impactor at a lower height. Similar to the overturning action, ratio of barrier mass to impactor mass has been found to have significant effects on the overall stability of the barrier. The proposed DB model for flexural design of RC wall is based on designing the stem wall with sufficient longitudinal reinforcement (resulting in sufficient stiffness of the wall) in order that neither the steel nor the concrete would surpass the limit state of yield thereby ensuring linear elastic behaviour. This conservative design criterion serves to prevent the stem wall from accumulating flexural deformation following multiple impacts (e.g. by fallen boulders). It has been confirmed by numerical simulations using program LS-DYNA that a stem wall designed based on the proposed model was indeed responding within the limit of yield which is consistent with the design criterion. The LS-DYNA simulation of the example wall did not show any formation of cracks of a size which was visible (i.e. 0.1 mm) nor any permanent deformation to the wall other than in the vicinity of the point of contact at the top which is a localised damage phenomenon. Furthermore, the accuracy of the proposed method in predicting deflection of the stem wall forming part of the flexural stiffness method has also been validated by comparison with results recorded from physical impact experimentation as reported in the literature. The database employed in the validation comprises results from physical and numerically simulated testings covering a total of 18 impact scenarios. In summary, there is sufficient evidence in support of the use of the proposed DB model in practice for designing the stem wall to perform satisfactorily in bending. Given the robustness of the proposed design methodology, it was employed to design a RC wall specimen for a large-scale impact experiment. The experiment was fully instrumented to measure the bending response behaviour of the wall specimen and the corresponding material strains. As expected, the specimen did not exceed its yield limit within the scope of the experiment. The estimated results have been shown to be in good agreement with the experimental results. Importantly, it was found from both the experimental and predicted results that the inertial resistance developed in the target stem wall played a significant role in terms of the bending response behaviour of the wall. Such an effect is normally neglected in a conventional FB design procedure. The ultimate goal of this research project is that the analytical models presented will be useful for designers of impact-resistant structures aiming for undertaking a more rational and optimised design. The practical applications of the proposed models in designing a rigid rockfall barrier are illustrated at the end of this thesis. Quasi-static lateral load from debris flow has been incorporated to co-exist with the impact action of the boulder in the calculation procedure. Design checks to ensure stability from overturning and satisfactory performance of the barrier in sliding and bending of the stem wall are also presented at every stage of debris surge. The design example addresses all the requirements in engineering practices to well illustrate the application of the new design methodology.
  • Item
    Thumbnail Image
    Further understanding ground source heat pump system design using finite element methods and machine learning techniques
    Makasis, Nikolas ( 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.