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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.
11

A modelling study of segmentation of naturally ventilated tall office buildings in a hot and humid climate

Liu, Pei-Chun January 2012 (has links)
The prevailing paradigm in indoor environment control of office buildings often excludes natural ventilation, due to the fact that its dynamic nature may not be compatible with the close control of mechanical conditioning systems. The challenges will be greater in terms of the potential high magnitudes of wind and buoyancy forces at high levels of tall buildings. This research is concerned with the prospect of tall office buildings that are purely naturally ventilated. It is proposed that “segmentation” might offer the least risky approach for natural ventilation design of non-domestic tall buildings. Accordingly, the generic design procedure are proposed for investigating the influence of segmentation on ventilation air flows: firstly, the single-cell envelope flow model is adopted to evaluate the steady-state bulk flows through openings under a specified design condition; secondly, dynamic thermal modelling with an air flow network module is used, because of the particular importance of the coupling between the airflow and thermal process for evaluating the year-round ventilated cooling potential of targeted spaces. The chosen thermal model utilizes a multi-cell airflow network model (AFN) since the targeted buildings can no longer be described by a single-cell model; thirdly, computational fluid dynamics (CFD) simulation is suggested in the later design stage to cope with insufficient resolution of local airflow distribution in previous modelling stages; finally, the overall performance of comfort ventilation is then interpreted in relation to adaptive thermal comfort theory by the use of Building Bioclimatic Charts, which offers a way of rapidly testing whether or not natural ventilation is likely to produce comfortable conditions. The novelty of this work lies not in the methodology, which uses available modelling tools, but in the evaluation of naturally ventilated tall buildings with reference to segmentation in the climatic context of Taiwan. The effect of segmentation is evaluated by comparing the overall ventilation performance under three different building configurations, namely the isolated, segmented and non-segmented tall buildings. The overall objectives are to determine whether the magnitudes of air flow rates and the resultant flow velocity can achieve the desired comfort ventilation over a range of specified conditions. Potential scenarios where the design goals may not be ensured are identified. The feasibility for naturally ventilated tall office buildings in hot and humid climates is clarified accordingly.
12

Enhanced flame retardant polymer nanocomposites

Elbasuney, Sherif January 2013 (has links)
Fire is a continuous threat to life and property. The total annual UK fire loss is estimated to be 0.25% of its gross domestic product (GDP) (Goddard, 1995). According to fire statistics, more than 12 million fires break out every year in the United States, Europe, Russia, and China killing about 166,000 people and injuring several hundreds of thousands (Morgan and Wilkie, 2007). Polymers which take up 80% of the organic chemical industry, are known for their high flammability with the production of heat, corrosive toxic gases, and smoke (Bent, 2010). Improving the fire retardancy of polymeric materials is a major concern and also a major challenge. Nanotechnology could have a significant impact on polymeric materials through the achievement of polymer nanocomposites (PNs) with enhanced functional properties (Giannelis, 1996, Schartel and Batholmai, 2006). If this can be achieved, there will be an enormous increase in the use of improved flame retardant (FR) PNs in mass transportation, aerospace, and military applications where fire safety will be of utmost importance (Horrocks and Price, 2008). In this research project nanoparticles that could have a synergistic effect with traditional FR systems, or that could have a FR action (nano-fire extinguishers), were formulated and surface modified during continuous hydrothermal synthesis (CHS). The bespoke nanoparticles were developed in a structure that could be easily integrated and effectively dispersed into a polymeric matrix. A solvent blending approach for integrating and dispersing colloidal organic modified nanoparticles into polymeric matrices was developed. The impact of nanoparticles of different morphologies including nanospheres, nanoplates, and nanorods on epoxy mechanical, thermal, and flammability properties was evaluated. A laboratory based technique using a Bunsen, video footage, and image analysis was developed to quantify the nanocomposite's direct flame resistance in a repeatable fashion. A new self extinguishing epoxy nanocomposite was developed which showed an enhanced performance in extreme conditions and with good mechanical properties.
13

Numerical modelling of tunnel fires and water mist suppression

Hart, Robert January 2006 (has links)
Fires in mine tunnels and other underground space are a serious hazard, that can, if left unchecked, result in significant economic loss and human tragedy. In the UK, methods such as water deluge, foam application, and various types of handheld extinguishers have been used, but statistics show no improvement in the incidence of fire. Water mist has the potential to be an effective fire suppression system for tunnel spaces. Typical water mist systems utilise small droplets of around 100 micron that have a low terminal velocity and a high surface to volume ratio. This leads to behaviour distinct from that of traditional sprinklers. Various mechanisms of action have been identified: removal of heat; oxygen depletion; fuel cooling; attenuation of radiation; and disruption of air flow. The relative importance of each is case dependent. Current research has focussed almost exclusively on enclosures with minimal or no ventilation, and no data relevant to the application of mist in tunnels exists. In this thesis, a series of Computational Fluid Dynamics (CFD) simulations, based on published experimental data, are used to indirectly validate a CFD model of a hypothetical water mist system applied to a real tunnel fire, and to improve the understanding of how water mist performs in a strongly ventilated space. The water mist is represented by a Lagrangian-based particle-tracking model. This model is fully coupled to the continuous phase, accounting for transfer of momentum, heat, and mass. A 16m3 unventilated enclosure is used first to validate a pool fire model based on 0.3m square pools of methanol (27 kW) and hexane (115 kW). The behaviour of a thermal plume in a tunnel with forced ventilation is then validated, initially using a fixed volumetric heat source of 7.5kW in a small-scale tunnel, and then on a full-scale 3m square cross-section tunnel with a 3m diesel pool using the pool fire model. The water mist model is validated with the enclosure fire, and a sensitivity study assesses the effect of droplet diameter, spray velocity and angle, and water flow rate on the performance of the system. Finally water mist is applied to the tunnel fire At low ventilation, oxygen depletion and air-flow disruption are significant, whereas at high ventilation the only effect of the mist is to remove heat and reduce temperature.
14

Distributed IT for integration and communication of engineering information for collaborative building design

Fahdah, Ibrahim January 2008 (has links)
In recent years, the rapid development of new information technologies has significantly impacted on the product development process as strategic means to gain competitive advantage in a global market. In the engineering domain, powerful computer-based tools such as Computer Aided Design systems enable engineers to perform various design tasks and realise product concepts in the early phase of the product development process. However, the increasing complexity of modern products as well as the globalization of product development further necessitate distributed and collaborative design environments. This is where different computer systems and dispersed specialists in similar or different disciplines need to collaboratively be involved in shared design activities. Therefore, the integration and communication of engineering information are two of the most key technical factors in ensuring successful collaboration. The current application of information technology in supporting collaboration during the design process is limited to either a document-based or a common format-based exchange level. These methods provide relatively simple forms of collaboration compared with desired distributed and collaborative design environments that can deliver more effective ways of collaboration. The work detailed in this research investigates the advantages of using modern distributed information technologies alongside a suitable framework and a product model to support multi-disciplinary collaborative design. The work also involves exploring other important issues related to real-time collaborative design environments. These are design transaction management, access control, communication, and version management. The research work employs modern technology and distributed computing to enhance the processes of collaborative building design. The research proposes a framework and a product model to extend the functionalities of stand-alone and single-user design systems to facilitate synchronous collaborative design where distributed designers can work concurrently on a centralised shared model and carry out all necessary communication and data exchanges electronically. The implemented framework proposes a data transaction management approach that ensures efficient concurrent access to the model data and maintains data consistency. The framework also employs software agents to automatically access and operate on the information exchanged among the collaborators. The proposed product model in this work extends an adopted model to support access right control and version management. The work is implemented in an experimental software as a client-server model. .Net technology is used for implementing the framework and the product model and virtual reality technology is used to allow for intuitive interaction with the system. The research concludes that the utilisation of the modern distributed technologies can effectively induce change in the design process toward a more collaborative and concurrent design. As demonstrated within this work, these technologies with a suitable system design can meet the main requirements of a real-time collaborative building design system.
15

Performance analysis of ground source heat pumps for buildings applications

Omer, Abdeen Mustafa January 2012 (has links)
Geothermal heat pumps (GSHPs), or direct expansion (OX) ground source heat pumps, are a highly efficient renewable energy technology, which uses the earth, groundwater or surface water as a heat source when operating in heating mode or as a heat sink when operating in a cooling mode. It is receiving increasing interest because of its potential to reduce primary energy consumption and thus reduce emissions of GHGs. The main concept of this technology is that it utilises the lower temperature of the ground (approximately <32°C), which remains relatively stable throughout the year, to provide space heating, cooling and domestic hot water inside the building area. The main goal of this study is to stimulate the uptake of the GSHPs. Recent attempts to stimulate alternative energy sources for heating and cooling of buildings has emphasised the utilisation of the ambient energy from ground source and other renewable energy sources. The purpose of this study, however, is to examine the means of reduction of energy consumption in buildings, identify GSHPs as an environmental friendly technology able to provide efficient utilisation of energy in the buildings sector, promote using GSHPs applications as an optimum means of heating and cooling, and to present typical applications and recent advances of GSHPs. The study highlighted the potential energy saving that could be achieved through the use of ground energy sources. It also focuses on the optimisation and improvement of the operation conditions of the heat cycle and performance of the GSHP. It is concluded that GSHP, combined with the ground heat exchanger in foundation piles and the seasonal thermal energy storage from solar thermal collectors, is extendable to more comprehensive applications.
16

An investigation of the strength of brickwork walls when subject to flood loading

Herbert, Daniel Mark January 2013 (has links)
The main purpose of this programme of research was to establish characteristic water levels to which new and existing properties of masonry construction can be protected against flooding. Typical flood protection systems often rely on the structural strength of the building and in doing so generate significant lateral loadings. Current guidance appears to be based on the results of a single experimental study and no calculation technique is currently available to determine suitable characteristic levels. The research aim was addressed by conducting a series of experimental tests at model scale and by developing a theoretical analysis. Model scale masonry wall panels were successfully tested in a geotechnical centrifuge and were subject to hydraulic loading or uniform wind loading. Wind loading was considered to allow validation of the experimental procedure to results in the literature. Wall panels were constructed from both brick and block units and the effect of different mortar strengths, openings, vertical loadings and cavity construction were assessed. The experimental procedure showed very good repeatability in terms of ultimate load and generally a yield line type failure mode was observed. A theoretical analysis based on yield line analysis was developed using spreadsheet software and verified using the results from the experimental programme. The analysis gave a good approximation of the experimental ultimate loads, but the optimised failure mode was not always consistent with that observed in the tests. A parametric study was completed to assess the effect of varying parameters not considered in the experimental study and in addition a typical domestic property was modelled to assess its resistance against flood loading. The characteristic water level for the weakest wall of the property was found to exceed the value given in the guidance, of 0.6 m, by 38 % and signified the importance of completing the correct modelling procedure.
17

Developing a BIM-based methodology to support renewable energy assessment of buildings

Gupta, Apeksha January 2013 (has links)
Realising the benefits of implementing Building Information Modelling (BIM) tools and processes on projects worldwide, the architecture, engineering and construction (AEC) industry is rapidly moving towards BIM adoption. This calls for higher levels of interoperability amongst existing design and analysis tools used by various project team members. An approach to achieving higher levels of BIM maturity and interoperability is to adopt open, non-proprietary data exchange standards such as the Industry Foundation Classes (IFC). Efforts are currently underway to establish IFC-compliance in analysis tools. Establishing interoperability between architectural BIM models and energy analysis tools has been a challenging effort. With the industry chasing renewable energy targets for existing and new building stock, it becomes imperative to incorporate analysis tools for renewable energy systems (RES) in this effort. A plethora of tools are used by the project team to assess the performance of various RES in existing buildings or in post-design stages of new buildings. A holistic RES simulation tool is required that can assess various RES and their impact on the building’s energy consumption, carbon emissions and operational costs. Developing this tool’s interoperability with architectural BIM models would lead to higher adoption. The aim of this thesis is to develop a methodology to support renewable energy simulation by using architectural BIM models based on open data exchange standards thereby enhancing their interoperability. The research process involved a literature review of the existing RES analysis methods and approaches of developing IFC-compliant analysis tools. A methodology was developed that involved a standardised conceptual framework that can be used to establish compliance in RES analysis tools with open-data exchange schemas. The conceptual framework was implemented in a solar PV simulation model by means of a prototype. The prototype was validated against existing PV analysis tools and presented to industry experts to gain their feedback. It was concluded that the tool supported RES assessment of buildings in early design stages and could be widely adopted as a BIM tool by the AEC industry.
18

A conceptual collaborative engagement framework for road infrastructure management in Nigeria

Adetola, Alaba Ekekiel January 2014 (has links)
This study developed a conceptual collaborative engagement framework to overcome the challenges and contextual constraints associated with road infrastructure management in Nigeria.
19

Behavior of lightweight framing systems for buildings

Abbaker, Abdelfattah Elnur January 2006 (has links)
Presented in this thesis are the results from two distinct investigations on the behaviour of lightweight framing systems for buildings. One investigation concerns the characterisation of cold-formed steel sections of novel shape for the design of columns in modular construction, and this is reported in the first part of thesis. The second new investigation is for a theoretical analysis to determine the elastic critical buckling load for shear-flexible frames of fibre reinforced polymer sections. This work is detailed in the second part to the thesis. Modular 2000 Ltd. fabricated the column specimens that were characterized for the research on lightweight steel modular construction. To determine the reSistance of nine different column types a series of nominal concentric strength tests were conducted on specimens of 2.7 m length having a new E-section shape. The novelty to the shape is that it has no flat elements and is continuously curved in plan. Open E-sections are of S350 structural grade steel, are nominally 100x43 mm in plan, and have wall thicknesses of either 1.5 or 2 mm. Various bracket and enclosure combinations were the variables in the nine column types tested. These were connected to the E-sections by MIG plug-welding. Except for the 100x40x1.5 mm C-enclosure of S350, the other attachment components were of steel grade CR4, at 1.5 mm thickness. There were five column types with E-sections of 2.0 mm thickness and four with 1.5 mm thickness. Reported are the salient results from 54 strength tests, where the mode of failure was global buckling about the minor-axis of the E-column. To also determine the local buckling strength, and the effective area, a small series of stud column tests were performed on 200 mm long specimens of the 1.5 mm open E-section only. To support the understanding gained from the series of full-sized physical tests on E-columns, a programme of theoretical work is presented which is used to determine the design strengths of the column types and to predict the elastic and inelastic critical loads of a curved panel. Theory is also used to find a plasticity reduction factor for the E-section, which is required to "establish the effective area for local buckling. BS 5950-5: 1998 gives a code of practice for the design of cold-formed thin gauge sections. This current guidance is specific to steel sections comprising Simple shaped members that are of flat elements bounded either by free edges or by bends. The new results from the combined theoretical and eXperimental studies to characterise E-columns are evaluated and used to make recommendations on how SS 5950-5: 1998, and, in particular, Section 6 for members in compression, can be used with E-sections to design modular units. In the second part of the thesis the author shows how a static analysis for plane frames of shear-flexible members, written by a previous Warwick University PhD student, can be modified to calculate the elastic critical buckling load for overall instability. The modified sframe programme provides a practical analysis tool that, importantly, includes non-linearity by way of second-order P-L1 effects with shear-flexible functions and semi-rigid joint action. In conventional frame analysis shear-flexibility is ignored when members are of isotropic material (steel), and by way of a preliminary parametric study the author shows why the influence of shear deformation on reducing the buckling load of shear-flexible frames should not be neglected when the material is of fibre reinforced polymer. By studying the change in critical load in simple frame problems it is found that there is an interaction between shear-flexibility and the torsional stiffness given to the beam-to column joints. Moreover, the study on the instability of shear-flexible frames provides evidence to suggest that the relative stiffness values for joint classification boundaries are likely to be lower than those for steel frames by Eurocode 3 (BS EN 1993-1: 2005). This is an important finding for when a structural Eurocode or other code of practice is drafted for lightweight framed structures of fibre-reinforced polymer materials. Although the work presented in this thesis is from two distinct investigations the deliverables are important to the sustainable development of lightweight framing systems for buildings.
20

The use of passive damping to increase sound insulation in buildings

Yan, Feng January 2016 (has links)
This thesis examined the potential sound insulation benefit by using damping material to absorb vibrational energy along its transmission path. Statistical Energy Analysis (SEA) was used to evaluate the effect on system performance of adding damping globally, as well as its influence on individual transmission paths. Nine different theoretical models were studied using both bending only and three-wave SEA models to predict the system behaviour in different frequency regions. The results suggest that global damping treatment generally increases the sound insulation in buildings. Initial increases in the internal loss factor (a term used in SEA to describe material damping properties) were found to provide significant initial improvements in sound insulation and flanking paths as opposed to direct paths were found to benefit more from damping treatment. A simple approximation was proposed to predict the damping benefit of paths of specific order without the need to run a full SEA model. In the presence of heavily damped structural element, where SEA is less likely to provide accurate prediction, a forward ray tracing algorithm was proposed as a supplement. It enables one to predict the energy transmission through a heavily damped component coupling two or more lightly damped components (or SEA subsystems). The energy distribution along the edges of the damped component was studied. The contribution from the direct field was found to dominate the incident energy and resulting transmission, especially in areas close to the source when damping is high. Different passive damping treatment techniques were reviewed as well as the theoretical damping level that is achievable as a guidance for theoretical and experimental validation. Several damping measurement techniques were studied and experimental validation of the ray tracing code was undertaken.

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