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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.
291

Laboratory characterisation of pavement foundation materials

Edwards, Jonathan Paul January 2007 (has links)
Pavement foundations for major roads in the UK were historically designed on an empirical basis, related to a single design chart, restricting the incorporation of superior performing materials or materials for which the empirical data sets were not available. The adoption of performance based specifications was promoted as they are perceived to 'open up' the use of alternative materials (including 'local' sources of primary materials) or techniques, and allow for the incorporation of superior performance into the overall pavement design. Parallel developments to the performance based design of pavement foundations (allowing for superior performance) and in situ testing required the support of laboratory based performance tests. These laboratory based tests were required to determine material performance parameters (elastic modulus and resistance to permanent deformation) for both unbound and hydraulically bound pavement foundation materials. A review of the available laboratory apparatus indicated that they were either; unrealistic (and hence unable to provide the required material performance parameters), or overly complex and more suited to fundamental research. Therefore, the requirement for developmental research work was identified. The research reported herein details the development, manufacture and initial evaluation of simplified laboratory apparatus (the Springbox for unbound materials and static stiffness test for hydraulically bound mixtures) designed to produce the performance parameters of elastic modulus and relative resistance to permanent deformation for pavement foundation materials. The equipment and test procedure evaluation was undertaken across a range of materials, giving initial guidance on likely in situ performance. The innovative laboratory apparatus and materials guidance (including the potential to use recycled and secondary aggregates) was incorporated into key Highways Agency specification and guidance documents, which in turn influence construction practice outside of motorways and major trunk roads. This research concludes by outlining a number of recommendations for continued development and evaluation, including feeding back data sets from long term in situ performance testing for subsequent refinement of assumptions.
292

Mécanique des lits de silices granulaires pour l’optimisation des cœurs de panneaux isolants sous vide (PIV) / Mechanical study of highly nanoporous silica powder for vacuum insulation panels (VIP)

Kassou, Belynda 26 January 2018 (has links)
En Europe, le secteur du bâtiment représente près de la moitié de la consommation énergétique totale (dont 60 % pour le chauffage et la climatisation) et des rejets de CO2. Ainsi, une maîtrise de la consommation énergétique dans différents secteurs (bâtiment, transports et industrie) est nécessaire. L’utilisation de matériaux « super-isolants » thermiques tels que les panneaux isolants sous vide (PIV) dans la rénovation et dans de nouvelles constructions à très faible consommation énergétique sont prometteurs. Un PIV est composé d’un matériau de cœur thermoscellé dans une enveloppe hermétique mise sous vide. Le cœur est constitué d’un empilement de nano poudres de silices à très forte porosité (> 90%) et à très fine structure poreuse (< 200 nm). Deux types de silices sont utilisés : les silices pyrogénées (FS) avec lesquelles on obtient des PIV manipulables pour une densité de cœur de 160 kg/m3 après compaction contre 250 kg/m3 pour les silices précipitées (PS). Les PIV à base de silices FS sont plus efficaces thermiquement et mécaniquement que ceux à base de silice PS, mais restent plus coûteux. Cette étude propose de comprendre les différences de propriétés mécaniques entre les compacts de silice FS et PS. Ainsi, les comportements en compression œdométrique et en indentation sphérique d’une silice pyrogénée Konasil 200 et de deux silices précipitées Tixosil 43 et 365 ont été analysés. Ceux-ci sont complétés par des observations structurales en microscopie électronique à transmission (MET) et en diffusion de rayons X aux petits angles (SAXS). Le couplage de ces résultats à l’étude du vieillissement et de la structure multiéchelles des poudres permet d'identifier les causes des écarts des propriétés observées entre silices FS et PS. Ainsi, l’impact de la chimie de surface et de l’organisation multiéchelles entre les objets observés est mis en évidence pour expliquer les différences de propriétés mécaniques entre silices FS et PS. / Buildings account for almost the half of the total energy consumption (60% for heating and cooling) and CO2 emissions in Europe. Thus, the control of energy consumption in building appears as critical. In that perspective, "super-thermal insulating" materials such as vacuum insulation panels (VIP) are promising, both for buildings renovation, and for new energy-efficient constructions. A VIP is composed by a sealed core material in which vacuum is established. The core is made of an open nanoporous stack of silica powders with very high porosity (> 90%) and very fine porous structure (< 200 nm). Two types of silica are typically used: first fumed silica (FS) which enable to process panels with a sufficient compression strength for handling for a density as low as 160 kg/m3, second precipitated silica (PS) which enable to process denser panels with a minimal density of about 250 kg/m3. VIPs made of FS powders are more efficient in terms of thermal and mechanical properties as compared of VIP made of PS powders. However, their price is higher. This study aims at understanding the differences in mechanical properties noted between compacted FS and PS powders. Oedometric compression tests and spherical indentation test were carried out on compacts of Konasil 200 FS silica and on compacts of Tixosil 43 and 365 PS silica. In addition, structural observations of the powders were made using transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). These results permit to identify the parameters leading differences between FS and PS powders. Thus, surface chemistry, multiscale organization and interactions forces are highlighted to explain the differences in mechanical properties between compacts of FS and PS silica.
293

Economic and environmental input-output modeling: building material recycling

Choi, Taelim 14 November 2012 (has links)
A key dimension to improving urban economic and environmental sustainability is the efficient use of resources through recycling. A thriving recycling system requires not only effective institutional policies and community-wide diversion efforts, but also a competent local and regional recycling industry. Although the recycling industry has traditionally been recognized as a local service and fringe industry, it has noticeably transformed into an integral segment of industrial production systems as manufacturers have increasingly begun to adopt the principle of extended producer responsibility. Despite such changes, urban and regional theory and planning research has largely disregarded the industrial aspect of recycling, contributing to the dearth of information about the organizational and spatial patterns of the recycling industry and the impact of the establishment of recycling systems on local and regional scales. Given the knowledge gap, this dissertation addresses two questions: 1) What is the logic of the industry organization and spatial pattern of recycling industry in different institutional contexts? and 2) How is the economic and environmental impact of recycling systems determined in cases of construction and demolition waste recycling and waste carpet recycling? To answer the first question, this research develops a theoretical model that explains how recycling industrial activities are spatially distributed in light of institutional and organizational theories. The theoretical model characterizes organizational decisions pertaining to recycling functions and suggests spatial patterns of recycling systems. With respect to the second question, this research constructs a regional environmental input-output model on the metropolitan scale. It estimates regionalized energy use coefficients and greenhouse gas emission coefficients using various sources of data mainly compiled from the Manufacturing Energy Consumption Survey 2006, the State Energy Consumption Estimates, and the Commodity Flow Survey 2007. Based on regional input-output tables coupled with the regionalized environmental coefficients, this research quantifies, through simulations, the net economic and environmental impact of a localized construction and demolition waste recycling system in the San Francisco metropolitan area and regional carpet recycling systems in the Atlanta and Seattle metropolitan areas. Results of the simulations reveal that 1) the localized construction and demolition waste recycling system provides moderate economic benefits because of the limited job creation potential of mechanized recycling processes and yields relatively small environmental benefits with respect to the total weight processed; 2) wider adoption of the deconstruction technique expands job opportunities, increases energy savings, and reduces greenhouse gas emissions during the course of construction and demolition waste recycling; 3) regional-scale waste carpet recycling systems, in particular recycled nylon 6 production, create sizable new job opportunities and provides environmental benefits of energy savings and greenhouse gas emission reduction despite the long-distance transportation of waste carpet. These results suggest that policies that promote recycling industrial activities can significantly contribute to the economic and environmental sustainability of metropolitan areas.
294

Measuring sustainability perceptions of construction materials

Florez, Laura 24 May 2010 (has links)
As more owners seek to develop sustainable buildings, the construction industry is adapting to new requirements in order to meet owner's concerns. Material selection has been identified as an area where designers and contractors can have a significant impact on the sustainable performance of a building. Objective factors such as design considerations and cost constraints can play a role in the selection of materials. However, there may be subjective factors that could also impact the selection of materials. Building upon the potential impact of sustainability perceptions in an optimization model that can be used to help decision makers to select materials, this study defines and tests an instrument to identify and measure such perceptions. The purpose of this dissertation is to develop a conceptual instrument that measures the user-based assessment of product sustainability and validates decision-maker's perceptions in order to evaluate the contribution of subjective characteristics in materials selection. A survey of design and construction students and practitioners is carried out to capture the subjective factors included in the instrument. A Factor Analysis approach is used to refine and validate the measurement instrument and predict decision-makers' sustainability appraisal due to the factors considered.
295

Experimental testing, analysis, and strengthening of reinforced concrete pier caps by exterior post tensioning

O'Malley, Curtis John 17 May 2011 (has links)
Condition assessment of existing concrete bridge pier caps using the general shear provisions of the AASHTO LRFD Bridge Design Specification has caused the Georgia Department of Transportation (GDOT) to post a large number of bridges in the State of Georgia. Posting of bridges disrupts the free flow of goods within the region served by the bridge and has a negative economic impact. To prevent structural deterioration, diagonal cracking or failure of concrete pier caps in shear, the GDOT employs an in-situ strengthening technique that utilizes an external vertical post-tensioning system. However, the fundamental mechanics of this system and its effectiveness under service load have not been examined previously. This research examines the behavior of reinforced concrete pier caps that utilize the above strengthening system in a combined analytical and experimental program. In the experimental part of the study, two groups of full-scale reinforced concrete deep beam specimens were tested. The first group consisted of six deep beams with shear span/depth ratios of approximately 1.0, which is typical of bridge pier caps; of these six, two included the external post-tensioning system. In the second group, nine deep beam specimens that included a segment of the column representing the pier were tested; four of those tests included the external post-tensioning system. The tests revealed that the shear capacity computed using the AASHTO LRFD Bridge Design Specifications provided a conservative estimate of the specimen capacity in all but one case when compared to the experimental results. However, the AASHTO strut and tie provisions were found to provide a much closer assessment of the load carrying mechanism in the pier cap than the general shear provisions, in that they were able to predict the load at which yielding of the tension reinforcement occurred as well as the angle of the compression strut. The presence of the column segment in the second group had a significant impact on the failure mechanism developed in the specimen near ultimate load. The stress concentration at the reentrant corner between the pier cap and column interface served as an attractor for the formation of diagonal shear cracks, a mechanism not observed in previous deep beam tests in shear. The research has led to recommendations for improving the design of pier caps and the external post-tensioning system, where required, based on mechanics which are consistent with the results of the experimental program.
296

Mažų įmonių marketingo strategijos formavimas: statybinėmis medžiagomis prekiaujančių parduotuvių atveju / Small companies marketing strategy policymaking: building material stores that sell cases

Motiečiūtė, Vaiva 03 September 2010 (has links)
Baigiamajame magistro darbe nagrinėjami marketingo strategijos formavimo etapai, prekybos įmonės santykių su vartotojais aspektai, bei atlikta rinkos analizė. Dėl vis agresyvesnės prekybos centrų plėtros, smulkiesiems prekybininkams darosi vis sunkiau konkuruoti. Todėl atsirado poreikis išanalizuoti marketingo strategijas ir nustatyti, kokie veiksniai skatina vartotojus rinktis mažas parduotuves, o ne didžiuosius prekybos centrus ir sukurti efektyvią marketingo strategiją, tinkančią mažoms parduotuvėms. Atlikta mažų parduotuvių, prekiaujančių statybinėmis medžiagomis, klientų ir vadovų apklausa, kurios rezultatais remiantis, sukurtas marketingo strategijos modelis plėtojantis mažų parduotuvių, prekiaujančių statybinėmis medžiagomis, verslą. Ši marketingo strategijos formavimo analizė aktualiausia mažoms parduotuvėms, prekiaujančioms statybinėmis medžiagomis, nes atskleidžiami šiam įmonių tipui būdingiausi bruožai. / The thesis focuses on marketing strategy formulation stages, aspects of the marketing company relationships with consumer protection, along with market analysis. Due to more aggressive development of shopping centres’, the small traders are finding it increasingly difficult to compete. Thus, there is a need to analyze the marketing strategies and identify the factors that encourage consumers to choose small shops rather than supermarkets, and create an effective marketing strategy that is suitable for small shops. Survey results of clients and managers of small shops, dealing with building materials, were taken as a basis for the development of marketing strategies model for small shops dealing with building materials business. This marketing strategy formation analysis is especially relevant for small shops which sell building materials, as it reveals the features mostly characteristic for this type of companies.
297

Alkali-silica reaction in concrete containing recycled concrete aggregates

Adams, Matthew P. 09 January 2012 (has links)
Using recycled concrete aggregate (RCA) as a replacement for natural aggregate in new concrete is a promising way to increase the overall sustainability of new concrete. This has been hindered, however, by a general perception that RCA is a sub-standard material due to the lack of technical guidance, specifically related to long-term durability, on incorporating RCA into new concrete. The goal of this research project was to determine whether current testing methods could be used to assess the potential alkali-silica reactivity of concrete incorporating RCA. The test methods investigated were ASTM C1260 and ASTM C1567 for assessing natural aggregate susceptibility to alkali-silica reactivity (ASR), and the ability of supplementary cementitious materials (SCMs) to mitigate ASR, respectively. Seven different RCA sources were investigated. It was determined that ASTM C1260 was effective in detecting reactivity but expansion varied based on RCA processing. Depending on the aggregate type and the extent of processing, up to a 100% increase in expansion was observed. Replicate testing was performed at four university laboratories to evaluate repeatability and consistency of results. The authors recommend modification to the mixing and aggregate preparation procedures, when testing the reactivity of RCA using ASTM C 1260. This study also investigated the efficacy of replacing portland cement with supplementary cementitious materials (SCMs), known to mitigate alkali-silica reaction (ASR) in concrete with virgin aggregates, to control ASR in concrete incorporating reactive RCA. The SCMs investigated as part of this study included: fly ash (class F), silica fume, and metakaolin. The results of modified alkali-silica reactivity tests, ASTM C1260 and ASTM C1567 (AMBT), are presented for two different recycled concrete aggregates when using 100% portland cement, binary blends of portland cement and fly ash, and ternary blends of portland cement, fly ash and metakaolin or silica fume. The results indicate that SCMs can effectively mitigate ASR in concrete made with RCA. A 40% replacement of portland cement with class F fly ash was able to reduce expansions to below 0.10% in the AMBT for concrete containing 100% of a highly reactive recycled concrete aggregate. A ternary blend, however, of portland cement with a class F fly ash and metakaolin was most effective for both RCAs tested in this study. Higher levels of mitigation may be required for some RCAs, compared to the level required to mitigate ASR in concrete made with their original natural aggregates, depending on the age and composition of the RCA. / Graduation date: 2012
298

An examination of strategic challenges and opportunities in the wood-based building product industry

Tokarczyk, John A. 03 January 2011 (has links)
The wood-based building products industry has experienced significant turbulence over the past several decades as a function of multiple forces including among others globalization, product and process innovation, and shifting customer and consumer interest and demands. Collectively, these changes have challenged the historical tenets which have defined industry strategy and competition in the realm of basic products and contributed to consolidation and labor reductions. Consequently, an onus has been placed on industry participants to better understand and adapt to the new competitive landscape or risk loss of competitive advantages built on the practices suited to historical tradition. However, a limited range of work that considers the machinations of turbulence and resulting strategic implications has been directed toward the industry particularly where differentiation of products is limited. A contributing factor for this deficiency is the relative stability that has defined the industry for generations due in part to limited strategic variation beyond cost and production, limited cycles of technological and product innovation, commodity nature of many products, and passive manner of consumption. Accordingly, there is value in work that takes a critical and empirical view of industry changes in the context of both strategic and competitive implications, how participating firms address challenges, and what factors influence consumer purchase decisions. This work addresses this need through examination of each element, industry, firm, and consumer, in the context of turbulence, competition, and strategy and delineates previously unidentified considerations for competing in the new landscape. At the industry level, drivers of industry turbulence and subsequent strategic challenges, adaptations, and opportunities are identified and reviewed. Analysis suggests that improved strategy which considers organizational and product differentiation beyond cost and production efficiencies permits greater stability and increased leverage in the turbulent competitive environment. Recognizing a need for improved strategy, the firm level analysis employs a primary qualitative approach to isolate previously unidentified firm qualities analogous to successful deployment of a market orientation strategy using the resource based view of the firm as a framework for analysis. Connecting strategy to the consumer and product, theoretical consumer behavior constructs (consumption, behavior, and involvement) were connected to conceptualize dimensions of product differentiation capable of holding consumer appeal and acting as behavioral drivers in the passively consumed arena of primary wood-based building products. Taken together this work provides a view of strategic considerations within the wood-based building product industry that extends beyond previous work in several ways. First, by considering industry environment, firm strategy, and consumer behavior and product differentiation collectively in the manner described, this work provides a more vertically complete strategic perspective for industry participants. Second, within each chapter, findings and case based examples relevant to each element are presented. / Graduation date: 2012
299

Numerical simulation of strengthened unreinforced masonry (URM) walls by new retrofitting technologies for blast loading.

Su, Yu January 2009 (has links)
Terrorism has become a serious threat in the world, with bomb attacks carried out both inside and outside buildings. There are already many unreinforced masonry buildings in existence, and some of them are historical buildings. However, they do not perform well under blast loading. Aiming on protecting masonry buildings, retrofitting techniques were developed. Some experimental work on studying the effect of retrofitted URM walls has been done in recent years; however, these tests usually cost a significant amount of time and funds. Because of this, numerical simulation has become a good alternative, and can be used to study the behaviour of masonry structures, and predict the outcomes of experimental tests. This project was carried out to find efficient retrofitting technique under blast loading by developing numerical material models. It was based on experimental research of strengthening URM walls by using retrofitting technologies under out-of-plane loading at the University of Adelaide. The numerical models can be applied to study large-scaled structures under static loading, and the research work is then extended to the field of blast loading. Aiming on deriving efficient material models, homogenization technology was introduced to this research. Fifty cases of numerical analysis on masonry basic cell were conducted to derive equivalent orthotropic material properties. To study the increasing capability in strength and ductility of retrofitted URM walls, pull-tests were simulated using interface element model to investigate the bond-slip relationship of FRP plates bonded to masonry blocks. The interface element model was then used to simulate performance of retrofitted URM walls under static loads. The accuracy of the numerical results was verified by comparing with the experimental results from previous tests at the University of Adelaide by Griffith et al. (2007) on unreinforced masonry walls and by Yang (2007) on FRP retrofitted masonry walls. To study the de-bonding behaviours of retrofits bonded to masonry, and find appropriate solution to protect certain masonry walls against blast loading, various retrofitting technologies were examined. The simulation covers explosive impacts of a wide range of impulses. Based on this work, pressure-impulse diagrams for different types of retrofitted URM walls were developed as a design guideline for estimating the blast effect on retrofitted masonry walls. The outcomes of this research will contribute to the development of numerical simulation on modelling retrofitted URM walls, improving the technique for explosion-resistant of masonry buildings, and providing a type of guideline for blast-resistant design. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349719 / Thesis (M.Eng.Sc.) - University of Adelaide, School of Civil, Environmental and Mining Engineering, 2009
300

Environmental issues and house design in Australia : images from theory and practice / Helen Bennetts.

Bennetts, Helen January 2000 (has links)
Bibliography: leaves 172-182. / viii, 183 leaves, [96] p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Proposes that there are fundamental and inadequately recognised differences between architectural practice and the basis of much design advice about environmental issues in house design. Concludes by discussing the implications of these differences for understanding how environmental issues are currently addressed in house design in Australia. / Thesis (Ph.D.)--University of Adelaide, Dept. of Architecture, 2000

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