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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Thermal-structural behaviour of inorganic intumescent system

Kang, Sungwook January 2016 (has links)
This work discusses the thermal-structural behaviour of an 'inorganic'based intumescent coating. On exposure to heat, this fire-retardant system undergoes particular physical phenomena: (i) Thermo-chemical decomposition reactions; (ii) Formation of numerous micro-scale pores in its internal structure; (iii) Geometrical volume (thickness) expansions; (iv) Variations in its thermal boundaries. These simultaneous occurrences interact with each other's progressions with time. In order to evaluate the coating's thermal insulation performance and to optimise its performance, this study aims to clearly interpret the combined thermal-structural behaviour. This research program is constructed in four stages: • To identify the thermo-kinetic and -physical characteristics of the polymer compound, this work analyses the experimental data, obtained from Thermogravimetric Analysis, Differential Scanning Calorimetry, Electronic Furnace, and Cone Calorimeter tests; • To accurately quantify the net heat absorbed by the swelling specimen tested with the cone calorimetry, this study investigates (i) the irradiance intensification on the sample's top surface moving toward the heater, (ii) the heat transfer through the surface area of its perimeter being progressively extended, (iii) the convective fluid motions driven in testing and the corresponding coefficients, and (iv) the radiant mechanism generated in testing and the corresponding radiative properties; • To quantitatively assess the thermal insulation performance of the coating, this work numerically simulates the heat transfer mechanism through its porous structure, and analyses individual contributions of the component modes of heat transfer, by adopting 'effective' thermal conductivity; • To comprehensively explain the thermal-structural behaviour of the coating, this study proposes a series of sequential steps of mass and volume changes as a function of temperature, and numerically simulates the process of intumescence. All the findings gained from the previous three stages are applied in this simulation, which is verified by comparison with the experimental data. From this work, it can be identified that the performance of this refractory product is significantly affected by (i) endothermic water vaporisation with dehydration and dehydroxylation, (ii) effective thermal conductivity of its multi-cellular structure, (iii) length of the heat penetration path across its expanding volume, and (iv) radiant heat emission on its heated surfaces. The interacting behaviour of the inorganic-based intumescent coating is systematically analysed, from microscopic thermo-kinetic characteristics to macroscopic behaviours in relation to heat transfer and thermal expansion, in this study. Hence, it can contribute to further studies on intumescent-type materials and their practical development.

A ground motion selection and modification method suitable for probabilistic seismic assessment of building structures

Theophilou, Artemis I. January 2013 (has links)
Probabilistic seismic assessment is of interest both in the design of new structures, and in the assessment of existing structures. An accurate prediction of the structural response distribution requires a large number of dynamic analyses, using a large number of ground motions. Such a task, however, requires substantial computational work, and, furthermore, is impeded by the scarcity of high intensity records. In this research a methodology is proposed for sampling optimized suites of ground motions, which methodology is comprised of a vector-valued intensity measure (IM), and a ground motion selection and modification (GMSM) method. Using the optimized suites, an optimized response prediction is obtained, which presents a compromise between the reduction in the number ground motions used, and the loss of accuracy. The proposed vector-valued IM is comprised of the spectral acceleration at the fundamental period, the Normalized Spectral Area (NSA) parameter, and, optionally, a measure of the nonlinearity level. NSA is defined as the area of the displacement response spectrum between the fundamental period and the ultimate elongated period, normalized to the spectral displacement at the fundamental period. In this way, it captures the effect of the excitation spectral characteristics (i.e. frequency composition) on the response. NSA is intended to have high correlation to various relative response parameters. With the proposed GMSM method, optimized suites are formed through stratified sampling on the NSA parameter, using datasets of ground motions normalized to the spectral acceleration at the fundamental mode, in order to replicate the IM true central tendency and true dispersion. Consequently, the response parameter true central tendency and true dispersion are also replicated. Stratified sampling results in a reduced standard error of the mean IM, contrasted to random sampling. The advantage of the proposed GMSM method is that when there is sufficiently high correlation between NSA and the relative response parameters, the standard error of the mean is also reduced.

Thermally activated building systems within building envelopes

Cotter, Donal Fergal January 2016 (has links)
The purpose of the work presented in this thesis is to investigate if an externally insulated cavity wall activated using a 'Thermally Activated Building System' (TABS) and linked to an environmental source can become an energy actuator~ balancing distribution within a building's thermal mass and reducing peaks in energy demand. Internal space conditioning is mainly responsible for high levels of energy consumption within most buildings. Many energy strategies strive to manipulate building physics and architectural design to exploit viable low energy heating and cooling systems that can maintain and balance envelope integrity and occupant thermal comfort. A common method of reducing energy consumption and improving performance is the application of external insulation to walls. This reduces dynamic transmission and creates a capacitive layer with the potential to provide a heat sink for environmentally generated heat and coolth for short-term usage. To exercise the distribution of heat from generation sources, TABS is embedded into the outer mass layer that is externally insulated. The large surface areas involved creates dynamic heat flows that positively influence structural integrity and the internal space. The ability to hydraulically circulate energy within this mass layer and other zones also provides reduced thermal elemental stratification and improved structural thermal equilibrium. This project used both steady-state and cyclical scientific methods to carry out experimental testing within a hot box calorimeter. Steady-state testing was completed and compared to calculated methods, validating the thermophysical properties of the wall. A parametric study using a hot box calorimeter was conducted (with and without TABS) across staged performance upgrades to the cavity wall and a comparative study completed based on the results. In this thesis, results from cyclical testing showed that elemental thickness and location was key to maximising the walls performance within winter and summer variations. The air-filled cavity wall with external insulation outperformed the full filled cavity with insulation (with and without activation), even though the full filled cavity wall had a lower U-value. A detailed analysis of thermal stratification in the vertical plane of the wall showed that increased thermal control was possible with an optimised wall configuration and thermal activation. The application of TABS increased thermal storage (heating and cooling) within the mass layers with redundancy to accommodate increased overall performance from the TABS and aggregated systems. The thesis concludes that overall the application of TABS to a cavity wall is an effective solution, increasing the performance potential of primary systems (heating and cooling) and reducing the effects of construction deficiencies.

Hygrothermic rehabilitation in the exterior panels of prefabricated buildings by external thermal insulation composite systems (ETICS) with rendering : (two 'case studies', located in the Lisbon metropolitan area - SAC and QM)

Reas Pinto, Alberto Cruz January 2001 (has links)
No description available.

Natural fibre insulation materials for retrofit applications

Holcroft, Neal January 2016 (has links)
Improving the thermal performance of existing domestic buildings can have multiple benefits: reducing greenhouse gas emissions, reducing the cost of heating and therefore fuel poverty, improving comfort and health. Solid wall buildings constitute around 30% of UK housing stock, and are among the least efficient. However, the installation of solid wall insulation, while improving thermal performance can significantly affect the moisture balance of the building. This can result in mould growth, which can cause structural damage and lead to health problems for the occupants. This thesis explores the use of Natural Fibre Insulation (NFI) materials for internal solid wall insulation. The hygrothermal properties of a range of NFI materials are characterised in order to assess their potential for retrofit applications. This is followed by large-scale testing, which compares three solid wall insulation systems in controlled conditions, the results of which are used to validate a heat and moisture transfer model to further assess performance. Experimental results showed that the risk of interstitial condensation is significantly reduced by the application of natural fibre insulation in comparison to a conventional rigid foam system. Simulation of a solid wall exposed to climatic conditions for the UK revealed that the relative humidity at the interface between the masonry and insulation layers remained at 69% when internally insulated with hemp-lime and 96% with rigid foam insulation, while average moisture content of the masonry was 48% lower when hemp-lime was used. Field tests were also conducted to determine the thermal performance of two solid walls internally insulated with 80 mm of hemp-lime when exposed to real weather conditions. The thermal conductivity of the hemp-lime was found to be 30% higher than when measured in dry stead-state laboratory conditions due to the high moisture content of the masonry. However, its application still resulted in 66% and 68% reductions in the U-value compared to the uninsulated wall from 2.73 and 2.65 W/m2K to 0.93 and 0.86 W/m2K.

iTFM : improved travelling fires methodology for structural design and the effects on steel framed buildings

Rackauskaite, Egle January 2017 (has links)
Accidental fire can be disastrous, especially in buildings. Most fire deaths occur due to the toxic effects of smoke before any structural collapse. However, the effect of fire on structural stability is critical in regard to safe evacuation and safe access for fire-fighters, financial losses, and lost business. This is particularly the case in tall buildings where extended evacuation times are required due to phased evacuation practises. The understanding of fundamental mechanisms of whole building behaviour in fire has significantly increased over the last decades, in particular after the full-scale tests of various multi-storey buildings carried out in Cardington between 1994 and 1999. However, most of the current understanding and consequently the design codes are based on the assumption of uniform fire conditions in a compartment. While this assumption may be suitable for small enclosures, fires in large open-plan compartments have been observed to travel. Examples of such fires include the World Trade Centre Towers 1, 2 & 7 (2001), Windsor Tower fire in Madrid (2006) and the recent fire at the Plasco building in Tehran (Jan 2017). All of these buildings ultimately either partly of fully collapsed. Current design standards do not account for travelling fires. The standard and parametric time-temperature curves are based on small scale tests, and assume uniform burning of fire and homogeneous temperature distributions in a compartment. In the recent years a new design concept of the Travelling Fires Methodology (TFM) has been developed by G. Rein to account for the travelling nature of fires in large compartments. This design methodology considers non-uniform temperature distribution in the compartment and a wide range of burning floor areas. In this thesis the Travelling Fires Methodology is improved to account for more realistic fire dynamics and then applied to investigate the structural response of a multi-storey steel frame using finite element software LS-DYNA. This thesis is presented in a manuscript style: each chapter takes the form of an independent paper, which has been published or submitted to a journal for publication. A final chapter summarizes the conclusions, and suggests potential areas of future research. Firstly, an improved Travelling Fires Methodology (iTFM) that accounts for better fire dynamics is presented in Chapter 2. Equations are introduced to reduce the range of possible fire sizes taking into account fire spread rates from real fires. The analytical equations used to represent the far-field temperatures are presented in continuous form. The concept of flame flapping is introduced to account for variation of temperatures in the near-field region due to natural fire oscillations. iTFM is then used to analyse the effect of non-uniform heating associated with travelling fires on the thermal response of structural members and identification of the location of peak temperature along the fire path. It is found to be mainly dependent on the fire spread rate and the heat release rate. Location of the peak temperature in the compartment is found to mostly occur towards the end of the fire path. Full-scale testing of real structures is complex, expensive and time consuming. This is especially the case for structures with large compartments. There has only been a limited number of full-scale tests on real buildings carried out worldwide (e.g. Cardington tests). As a result, computational tools are commonly used to assess the structural response of complex buildings under fire conditions. However, they have to be validated first. Therefore, in Chapter 3, prior to the study of the effects of iTFM on the structural response, explicit solver of finite element software LS-DYNA used for the analyses in Chapters 4-7 is benchmarked for structural fire analyses against other static numerical codes and experiments. Four canonical problems that encompass a range of thermal and mechanical behaviours in fire are simulated. The parameter sensitivity study is carried out to study the effects of various numerical parameters on the convergence to quasi-static solutions. The results confirm that when numerical parameters are carefully considered not to induce excessive inertia forces in the system, explicit dynamic analysis using LS-DYNA provide good predictions of the key variables of structural response during fire. Finally, the structural response of a two-dimensional multi-storey steel frame subjected to uniform design fires and iTFM (presented in Chapter 2) occurring on a single floor and multiple floors is investigated in Chapters 4, 5, & 7, and Chapters 6 & 7, respectively. Fire type and the location of the fire floor in the frame are varied. The analyses and comparison of structural response mechanisms is presented in Chapter 4. Uniform fires are found to result in higher compressive axial forces in beams compared to small travelling fires. However, results show irregular oscillations in member utilization levels in the range of 2 - 38% for the smallest travelling fire sizes, which are not observed for the uniform fires. Beam mid-span deflections are similar for both travelling fires and uniform fires and depend mainly on the fire duration, but the locations in the frame where these displacements occur are found to be different. Chapter 5 extends the study presented in Chapter 4 and compares the results in the terms of the limiting temperature criteria and various structural limit states. Critical fire scenarios are found to occur on the upper floors of the frame where column sections reduce in size. Also, results show that depending on the fire scenario higher level of fire protection for different members within the frame may lead to either enhanced or worse structural response and/or resistance. During previous fire events, e.g. the World Trade Centre Towers (WTC) 1, 2 & 7 in New York (2001), flames were observed to not only travel horizontally across the floor plate but also vertically to different floors. In this thesis, the effect of vertically travelling and multiple floor fires on the structural response of a two-dimensional multi-storey steel frame is investigated in Chapter 6. The number of fire floors, and horizontal and vertical fire spread are varied. Results show that the largest stresses develop in the fire floors adjacent to cool floors, and their behaviour is independent of the number of fire floors. All, the fire type, the number of fire floors, and the location of the fire floor, are found to have a significant effect on the failure time (i.e. exceeded element load carrying capacity) and the type of collapse mechanism (Chapter 7). In the cases with a low number of fire floors (1 to 3) failure is dominated by the loss of material strength, while in the cases with larger number of fire floors (5 to 10) failure is dominated by thermal expansion. Collapse is observed to be mainly initiated by the pull-in of external columns or swaying of the frame to the side of fire origin. Analyses presented in Chapters 4 to 7 highlight that in the structural design for fires it is important to consider more realistic fire scenarios associated with travelling fires as they might trigger previously unnoticed structural mechanisms. Results on the multi-storey steel frame indicate that, depending on the structural metric examined, both travelling fires and uniform fires can be more severe than the other. A single worst case fire scenario under which a structure could be designed and deemed to be safe cannot be established. For different fire exposures failure is found to occur on different range of floors subjected to fire. Therefore, in order to ensure a safe fire resistance design of buildings with large enclosures, a range of different fires including both travelling fires and uniform fires need to be considered.

Domestic air conditioning in Malaysia : night time thermal comfort and occupants adaptive behaviour

Bin Ja'afar, Mohamad Fakri Zaky January 2008 (has links)
This is the first study of night time thermal comfort in Malaysia as well as the first study of sleeping comfort level. The focus of the investigation, the use of air-conditioners in homes clearly indicates a problem. Evidences of overcooling (76% of the cases) and sleep interruptions (45% of cases) to adjust control are found. In around 38% of the cases, the internal thermal profiles never reached a stable condition instead they keep cooling throughout the night until the units are turned off in the morning. The act of putting on a thicker, comforter type blanket, more of a psychological choice than a physiological need, during air-conditioned occupancy, results in people operating their air-conditioners at lower than the optimum temperature level. A thermal comfort field survey was conducted by monitoring 29 air-conditioned bedrooms, investigating the environmental conditions, the corresponding comfort perceptions and occupants' adaptive behaviour. Thermal neutralities and thermal acceptability for night-time occupancy in air-conditioned homes are established. Statistically significant difference is found between the neutral air temperature of normal blanket users (27.5 °C) and that of comforter users (25.2 °C). Thermal acceptability and comfort range for each group have also been established. A simulation study was conducted and it shows that the choice of using a comforter as opposed to a normal blanket results in an increase of up to 52% in the cooling load of a bedroom. This finding suggests that adaptive behaviour does not always result in less energy being used for comfort provision when active cooling is employed.

Keeping cool in Cairo : thermal simulation of passive cooling in dwellings

Sheta, Wael A. M. January 2012 (has links)
Cairo is one of the World's mega cities, with associated problems of overcrowding and suffering from problems such as pollution, traffic congestion and a shortage of dwellings and services. The new suburbs and communities around Cairo playa vital role in decreasing these environmental, social and economic pressures upon the city. According to the national planning scheme, the main aim of these communities was to address problems associated with air pollution, traffic and a shortage of housing. In addition, these developments were planned to deliver sustainable communities and lifestyles for future generations. This research studies El-Tagammu' El-Khames, one of the new urban settlements developed around Cairo. It is considered to be the new premium residential district of Greater Cairo. Unfortunately, most of the properties in this development are poorly adapted to the prevailing climate and an understanding of what constitutes a sustainable community is still one of the missing links in the Egyptian planning process. This thesis describes a field study and a thermal simulation analysis carried out for a typical dwelling in El-Tagammu' El-Khames. Internal and external temperatures were recorded for two periods in summer and autumn. The recorded external temperatures were used to validate the weather file proposed to be used in simulation. The recorded internal temperatures were used to validate the internal temperatures predicted using the simulation tool. Thermal simulation (Design-Builder) was then used to simulate the effect of a number of passive cooling strategies on the thermal performance of the house during peak summer. These strategies included a range of orientations, thermal conductivity (U-value), thermal mass, night ventilation and shading devices, and these were investigated as they are simple steps that could be applied to new and existing dwellings. An incremental approach was adopted, starting from a basic house model, investigating variations of a particular parameter, and progressing the optimum for that parameter as the basis for the next set of analyses. It was found that three modifications would improve thermal comfort in the dwelling studied such that air conditioning should not be necessary. These were to extend the time at which night ventilation ended (i.e. windows were closed) from 5:00 am to 10:00 am; to insulate the external wall; and to provide solar shading. This impact of these proposals was validated by confirmation of the effect of surrounding buildings, by repeating the analysis for other periods of the year (i.e. winter season), Technical recommendations drawn by comparing the real case with proposed model through different periods of the year, enable appropriate solutions for architects, designers and engineers to be chosen at the early stages of a design for new dwellings and well as existing developments to achieve low energy thermal comfort and keeping buildings cool in Cairo.

A study of the causes of variation of the sound insulation properties of party floors in newly converted dwellings

Peyvandi, A. January 1992 (has links)
No description available.

Compartment fire analysis for contemporary architecture

Majdalani, Agustin Hector January 2015 (has links)
Understanding the relevant behaviour of fire in buildings is critical for the continued provision of fire safety solutions as infrastructure continually evolves. Traditionally, new and improved understanding has helped define more accurate classifications and correspondingly, better prescriptive solutions. Among all the different concepts emerging from research into fire behaviour, the compartment fire is probably the one that has most influenced the evolution of the built environment. Initially, compartmentalization was exploited as a means of reducing the rate of fire spread in buildings. Through the observations acquired in fires, it was concluded that reducing spread rates enabled safe egress and a more effective intervention by the fire service. Thus, different forms of compartmentalization permeated through most prescriptive codes. Once fire behaviour within a compartment was conceptualized on the basis of scientific principles, the compartment fire framework became a means to establish, under certain specific circumstances, temperatures and thermal loads imposed by a fire to a building. This resulted not only in improved codes but also in a scientifically based methodology for establishing the thermal input from which to assess structural performance. The last decades have however seen an evolution of the built environment away from compartmentalization while the classic compartment fire framework has remained. Within this framework, while Regime I corresponds to the idealised experimental setups adopted by many of the researchers, the usually ignored Regime II is characteristic of open spaces and volumes, typical of contemporary architecture. This research project commences, through a review of classic literature by those regarded as the fathers of fire safety engineering, by revisiting the knowledge underpinning this seminal approach, and initiating the discussion of its continued relevance and applicability to an increasingly non-compartmentalised built environment. Compartment fires are extremely complex processes. Nevertheless, when treating the theoretical problem with sufficient accuracy, simple mathematical approaches can be extremely informative and serve as the background to more complex methodologies. In this context, the project introduces the problem of the compartment fire in its full complexity before discussing some simplifications typically assumed when representing the actual problem for design purposes. Further, despite the detailed experimental and theoretical background behind analytical formulations in the classic compartment fire framework, their development is revisited to establish the extent to which they can be applied. In this way, the range of validity of the classic framework is characterized, clarifying the limitations of existing design methods based on this framework, and identifying the areas where further research and extension is necessary. Given the importance of counting on simple analytical formulations at the early design stage when dealing with atypical architectural designs in today’s fire safety practice, an elementary theoretical compartment fire framework is elaborated with the aim of enveloping traditional as well as contemporary architectural layouts. This gave way to the development of a new set of regime of behaviour definitions, in addition to – and falling in-between – the classic Regime I and Regime II fullydeveloped compartment fire behaviours. With the aim of filling this gap of knowledge empirically and characterizing these additional behaviours, a series of small and large-scale tests are presented. The results demonstrate complex behaviours that cannot be described in terms of the classic framework. This evidences the great need to conduct research that provides physical insight into the dynamics of a fire in spaces that deviate from the small quasi-cubic enclosure – the natural consequence of compartmentalization – that was typically adopted throughout the original work that resulted in the data which validated the classic compartment fire framework. Overall, this project aims to inform and encourage the discussion of the existence of a broader compartment fire framework, where the historical Regimes I and II are limiting cases of a vaster fire behaviour which is intimately linked to the geometry of the compartment, the ventilation conditions, and the available fuel. While the classic compartment fire framework is still a robust tool, it is only one piece in the puzzle of approaching and resolving the fire problem in a building in a holistic way. The relevance of this discussion is apparent in face of contemporary architecture and infrastructure.

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