541 |
Simplified mechanical models for the nonlinear dynamic analysis of elasto-plastic steel structures impacted by a rigid bodyHeng, Piseth January 2017 (has links)
Buildings subjected to impact and explosion are usually studied using large scale and highly nonlinear finite element model which are time-consuming. The first part of the thesis deals with the development of simple and accurate models for evaluating the nonlinear inelastic behaviour of steel frame structures subjected to impact. The research work in this part has produced four simplified models. The first model concerns with a 4DOF model that reproduces the behaviour of the impacted column. The restraining effect from the rest of the structure is modelled by an elastic spring, a head mass and a static load applied at the top of the column. In the second model, the impacted column is then further simplified using a SDOF model. The behaviour of the SDOF model is governed by an analytical force-displacement expressions of the column loaded by a located force. The maximum displacement of the impacted column can also be determined explicitly by adopting an energy-equivalent approach. Afterwards, in an effort to model the whole structure, two finite element models are developed. For these models, a co-rotational super-element that consists of a beam element and two generalized elasto-plastic hinges is obtained by performing a static condensation. An elastic flexible beam element is used in the first finite element model, whereas a rigid beam element is considered in the second one. In these models, inelasticity is concentrated at generalized elasto-plastic hinges which are modelled by combined axial-rotational springs. The behaviour of the hinges is uncoupled in the elastic range while an axial-bending interaction is considered in the plastic range making it possible to reproduce a wide range of cross-sections and joints. In addition, unilateral contact between rigid point masses is considered and the energy loss during impact is accounted by means of a restitution coefficient following Newton’s impact law. Energy-momentum scheme is used to solve the equations of motion produced by these models. The second part of the thesis concerns with the performance of the connectors in composite steel-concrete slabs under explosion. The purpose is to determine residual capacities of the shear connectors after being damaged by explosion using large-scale pull-out and push-out experimental tests and finite element simulations. / <p>QC 20171106</p>
|
542 |
Internet Voting in Austria: History, Development, and Building Blocks for the FutureKrimmer, Robert 22 September 2017 (has links) (PDF)
This dissertation aims to investigate the origins of Internet voting, analyze several deployments of Internet voting technology in Austria and identify - based on these accumulated experiences - building blocks that can be useful in decision-making on and planning of future uses of Internet voting technology within Austria and throughout the world. In line with the goals of this thesis, it will address the following research questions: - How did Internet voting originate? - What experiences were noted in the process of implementing Internet voting in Austria? - What building blocks can be identified for developing future Internet voting both inside and outside Austria? Internet voting is part of a transformational movement that applies information and communication technologies to daily business activities. It is only logical that elections are also considered for applying electronic (remote) communication technologies. While early efforts were driven by the belief that elections could make easy use of the Internet, it was shown that while the principles have to be interpreted and consequently applied in a different way, the same principles can still be derived for Internet voting, like integrity, secrecy, transparency, accountability and public confidence. The need to have forms of decision making in electronic networks has been identified in its beginnings and has received continuous attention throughout its development. At the height of the excitement about the possibilities of the Internet, countries raced to become the first to run a legally binding election using electronic voting systems. While several candidates emerged (e.g., Costa Rica, Bosnia Herzegovina, Germany, United States), Estonia was victorious in 2005. To date, Estonia is the only country that has introduced this form of voting without any preconditions or other limitations. In Austria, the intentions to use information and communication technologies (ICT) in elections concentrated on parliamentary affairs. Spurred by the efforts around student elections in Germany, Austria sought to conduct Internet voting in 2000. In the years thereafter, considerable progress was made at WU Vienna University of Economics and Business (WU), and this progress spearheaded the debate in the early 2000s. At the beginning in the years 2001-2003, technical solutions were sought to verify voter eligibility and maintain voter privacy. Later, more sophisticated algorithms were developed, and functionalities like quotas in election commissions were added. The Federation of Students' elections in 2009 were a remarkable event that demonstrated highly contentious political debate around the topic. This debate continued after the elections, which were held in May 2009 and suffered from the intense debate and protests and consequential organizational shortcomings. The experiences also showed that accurate legal regulations are needed to show interaction with the constitutional legal texts and to ensure accountability to a remote electronic voting channel through legal means. International standards were a first step, but regulations based on actual experience were needed to show how remote electronic voting channels could be realized and how to avoid problems identified in pilot implementations. This practical knowledge also shows that sophisticated algorithms are not always the key to success. Rather, several key implementations make use of very basic technical means to realize the tasks given by law. One should not forget about the voters. They not only need to use such systems, but they also need to understand the processes in order to build trust. The constitutional court ruling lifted the election and ruled that the respective ordinance was not in line with the requirements of the law. Hereby, the court established higher requirements resulting barriers for offering Internet voting channels in future elections. While the election administration system, which was a pre-requisite for the Internet voting system, was discontinued in the election thereafter, it returned in recent elections where postal voting was offered. On the basis of the aforementioned experiences, twelve building blocks were compiled discovered. These include design decisions, such as the following: the form of electronic voting, adaptations of the legal base, the technical means for identification and secrecy, observation, control functions for the electoral commission, evaluation processes, transparency functions, ballot sheet designs, controlling the organizational context as well as providing options for planning and implementation. This framework therefore facilitates and eases the generation of feasibility studies and other analyses and decision making ahead of using Internet voting in an election. With little adaption it can also be used for the use of other voting technologies. This work utilizes theoretical work and knowledge from adaptations of legal texts. These texts cover a wide range of topics, including methods for implementing identification and anonymity functions in remote electronic voting as well as testing and certifying systems that require transparent procedures. The findings also show that implementing remote an electronic voting system is a complex topic. It requires trust in the election administration; otherwise, suspicion will arise when more technology is introduced and implemented in an election process. Remote electronic voting is one of the most challenging information technology (IT) projects.
|
543 |
Stiffness of reverse channel connections at room and elevated temperaturesHeistermann, Tim January 2013 (has links)
A frame structure exposed to fire undergoes two types of changes due to the resulting temperature fields. The first is the thermal expansion of the structural members and the second is the degradation of the material strength and stiffness as temperature rises. Initially the thermal expansion dominates the response and the structural member (beam) is exposed to compressive forces due to restrained expansion, thus precipitating flexural buckling. At higher temperatures the mechanical material properties degrade. This fact, together with the high compressive forces in the bottom flanges of the beam often results in local buckling, followed by the formation of a plastic hinge close to the support region. The combination of transverse loads and the rising temperature leads to the development of excessive deflections in the beam. When temperature rises enough for the bending resistance of the beam to become insufficient, catenary action is introduced. The result is that the beam transitions to a stage where tensile forces appear due to the catenary action. In these different stages of the response of the structure the beam-to-column connection plays a crucial role and its robustness will determine if the structure will be able to maintain its integrity.The robustness of a structure in a fire situation greatly depends on the rotational capacity of the connection region. High rotational capacity is required at elevated temperatures since the steel beams lose their bending stiffness and exhibit increasingly large deflections under constant load. Beam deflections result in increasing rotations at the supports and may lead to collapse due to connection failure. Other possible failure modes may occur in the structural members, for example due to yielding in tension of the beam. The reverse channel has been proposed as a practical alternative to assemble beams to tubular columns. In a simple implementation, the bending moment generated in the joint due to rotation of the beam may be neglected; however, research efforts are being attempted to quantify the level of constraint. The typical arrangement of the connection type consists of a reverse channel with its flanges welded onto the face of concrete-filled tubular columns and the web bolted to the endplate of a beam. Thicknesses and depths of the reverse channel determine the level of rotational restraint at high temperature. The reverse channel has the ability to undergo catenary deformation in the tensile zone due to the applied rotation at the support and similarly it is relatively ductile in the compression zone. Overall, the reverse channel connection response is rather ductile in terms of its ability to undergo large rotational deformation as long as bolt failure is avoided through proper design.Various tests have been performed to study the behaviour of this type of connection such as full scale buildings, sub-frames, isolated joints and individual sections. The aim of these tests was to capture the connection behaviour in relation to other structural components in fire. This thesis focuses on the tests carried out on the connection components and their finite element modelling. A comprehensive parametric study was performed to assess the influence of different parameters on the behaviour of the connection component at elevated temperatures. The results from the finite element analyses have been utilized to validate analytical models that describe the behaviour of this type of connection at ambient and elevated temperature. Insight into the analytical models provides proper background to a structural designer to estimate the initial stiffness and understand the behaviour of the reverse channel in the connection. / En ramkonstruktion utsatt för brand påverkas på två olika sätt av temperaturhöjningen. För det första blir det en längdutvidgning av temperaturhöjningen och för det andra tappar materialet styrka och styvhet med ökande temperatur. Inledningsvis dominerar effekten av temperatur-utvidgningen. Denna leder till tryckande tvångskrafter i konstruktionen vilka kan leda till knäckning.Vid höga temperaturer sjunker materialets styvhet och styrka. Detta kan tillsammans med de höga tryckkrafterna leda till att flytleder bildas vid stöd. De stora tryckkrafterna kan också orsaka knäckning i balken och transversallasterna kan med den minskade styvheten på grund av temperaturhöjning ge upphov till mycket stora deformationer och balkens bärförmåga blir vid tillräckligt höga temperaturer otillräcklig. Vid tillräckligt stora deformationer övergår det statiska verkningssättet från böjning till linverkan. Under denna övergång spelar förbanden mellan balkar och pelare en central roll, och hur dessa klarar att hantera laster och deformationer avgör om hela konstruktionen kan klara belastningen.Hur en konstruktion klarar en brandbelastning beror i hög grad på hur förbanden mellan balkar och pelare klarar rotationer. En stor rotationskapacitet krävs vid höga temperaturer eftersom stålbalkar då har låg bärförmåga och deformationerna kan bli mycket stora även om lasterna är oförändrade. Stora deformationer i balkarna leder till stora rotationer i knutpunkterna vilket kan leda till att förbanden brister och hela konstruktionen kollapsar. Andra möjliga brottmoder kan vara kollaps av balkarna på grund av plasticering under drag. U-profilen har föreslagits som ett praktiskt alternativ för att ansluta balk till pelare. Rotationskapaciteten för ett sådant förband kan bedömas som försumbar, men forskningsinsatser görs för att bestämma den. En föreslagen utformning är att svetsa U-profilens flänsar till den betongfyllda pelaren med slutet tvärsnitt och livet fäst med skruvar i ändplåten på en balk. Rotationsstyvheten vid höga temperaturer kommer att bero på dimensioner på U-profilen. En U-profil har möjligheten att genomgå omvandlingen till linverkan i den dragna delen när den utsätts för ändrotation med den tryckta delen intakt. I allmänhet har ett förband med en U-profil möjlighet att klara stora rotationer under förutsättning att skruvförbandet är utformat på rätt sätt.Ett antal försök har genomförts för att studera hur föreliggande förband kan fungera i en byggnad, en del av en ram, enskilda förband och i tvärsnitt. Försöken har gjorts för att nå förståelse för hur förbandet fungerar tillsammans med andra konstruktionsdetaljer när de utsätts för brandbelastning. Denna avhandling fokuserar på försöken med delar ur förbandet och finit element modellering. En omfattande parameterstudie har gjorts för att förstå hur olika parametrar påverkar förbandets egenskaper vid förhöjd temperatur. Från FE-beräkningarna har analytiska modeller tagits fram som beskriver förbandets egenskaper vid medelhöga och höga temperaturer och dessa ger konstruktören möjlighet att uppskatta den ursprungliga styvheten hos förbandet med U-profil och förståelse för dess uppträdande. / <p>Godkänd; 2013; 20131008 (timhei); Tillkännagivande disputation 2013-11-11 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen, dubbel doktorsexamen LTU och University of Coimbra, Portugal. Namn: Tim Heistermann Ämne: Stålbyggnad/Steel Structures Avhandling: Stiffness of Reverse Channel Connections at Room and Elevated Temperatures Opponent: Professor Darko Beg, Head of Steel Structures, Ljubljana University, Ljubljana, Slovenien Ordförande: Professor Milan Veljkovic, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Vice ordförande: Assistant Professor Rui António Duarte Simões, Civil Engineering Department, University of Coimbra, Coimbra, Portugal Tid: Tisdag den 3 december 2013, kl 09.00 Plats: F1031, Luleå tekniska universitet</p>
|
544 |
Prefabrication strategies in the timber housing industry : a comparison of Swedish and Austrian marketsNord, Tomas January 2008 (has links)
The functional-based building regulations issued in 1994/95, made it possible to once again build higher buildings with timber structures in Sweden. At the same time there was a need to make the traditional project- oriented construction process more efficient, with prefabricated building systems and products as one possible solution. Since then, a number of timber housing companies have established product strategies and developed system solutions to meet the demands from different markets. In other European countries, changes in rules and regulations have positively facilitated the development of timber building products and systems and established new companies and strategies. Austria is one example, where architecture and technology are in focus, developing different product strategies in the timber housing industry. External factors and their changing, affect the formulation of viable business strategies in the timber housing industry. This dissertation aims to describe and analyse the strategic development of timber housing companies in Sweden and Austria. Strategy theories on the alignment of internal elements and external factors to create competitive advantage are applied in this dissertation. The results are based on empirical data gathered in a multiple case-study with two cases from Sweden and Austria, respectively. Result show that the strategic development of the Austrian timber housing companies was determined by the established conditions in the construction process. Timber structures already had strong positions in specific market segments; hence, the strategic behaviour of timber housing companies progressed with an inside-out approach. The strategic focus was to develop efficient internal processes that focus on design skills, flexible production facilities and on-site assembly resources to improve competitive advantage. The strategic development of the Swedish timber housing companies was based on what was possible from the changes in basic conditions, which partly diverted from the common and shared understanding in the construction process; hence the strategic behaviour of timber housing companies have had an outside-in approach to create competitive advantage. They have developed product platforms of standardised modules or elements and where cooperation with technical and system design complementors have been important to offer competitive timber building system solutions. The results indicate a strong correlation between basic conditions - construction process - firm conduct. Changes in basic conditions will give raise to firm conduct, different from the normative behaviour in the construction process, by firms with resources and capabilities by the changing basic conditions. / Möjligheten att bygga höga byggnader med trästomme i Sverige kom som en följd av införandet av funktionsbaserade byggregler i mitten av 1990-talet. Samtidigt fanns ett behov av att effektivisera den traditionellt projektorienterade byggprocessen där industriellt förtillverkade systemprodukter sågs som en möjlig lösning. Detta utgjorde drivkraften till att ett antal träbyggnadsföretag har skapats och utvecklat produktstrategier och systemlösningar för högre hus i trä. Även i ett europeiskt perspektiv har det skapats ökade möjligheter för träbyggprodukter inom husbyggandet via regeländringar, vilket påverkat företagens strategier. Ett exempel är Österrike där arkitektur och teknik varit förtecken i utvecklandet av olika produktstrategier inom träbyggnadsindustrin. Omvärldsfaktorer och dessas förändring påverkar hur träbyggföretag skapar och utvecklar sina företagsstrategier. Denna avhandling syftar till att beskriva och analysera den strategiska utvecklingen av träbyggföretag i Sverige och Österrike. Avhandlingen har sin teoretiska bas i strategiteorier, där passningen mellan interna och externa förutsättningar ligger till grund för hur företag utvecklar konkurrensfördelar. Resultaten är baserade på data insamlade via en multipel fallstudie där två fall från Sverige respektive Österrike ingick.Resultaten visar att de österrikiska träbyggföretagens strategiska utveckling har skett inom ramen för vad som är givet av den etablerade byggprocessen. Träbyggnader har haft sina givna marknader och företagens strategiska agerande har varit med ett inifrån-ut-perspektiv. Det strategiska agerande har präglats av att utveckla effektiva interna processer med fokus på konstruktionskunnande, flexibla produktionsmetoder och byggplatsåtaganden för att öka konkurrensförmågan. De svenska träbyggföretagens strategiska utveckling har skett inom ramen för vad som är möjligt utifrån de förändrade grundförutsättningarna, och delvis avvikande från normen i byggprocessen. Träbyggföretagen har haft ett utifrån-in perspektiv och utvecklat träbyggsystem baserade på standardiserade modul- eller planelement. Samarbeten med olika projekteringsresurser har varit viktiga för erbjudanden med hetsåtagande.Resultaten visar att det finns ett starkt samband i kopplingen mellan grundförutsättningar - byggprocess - företagsagerande. När förändringar i grundförutsättningar sker som avviker från byggprocessens etablerade norm skapas möjligheter för företag med passande resurser och erbjudanden. / Godkänd; 2008; 20081105 (ysko)
|
545 |
CFRP Strengthening of Cut-Out Openings in Concrete Walls – Analysis and Laboratory TestsPopescu, Cosmin January 2017 (has links)
Redesigning buildings to improve their space efficiency and allow changes in use is often essential during their service lives to comply with shifts in living standards and functional demands.This may require the introduction of new openings in elements such as beams, walls, and slabs,which inevitably reduces their structural performance and hence requires repair or strengthening.However, there are uncertainties regarding both the effects of openings and the best remedial optionsfor them. Traditionally, two methods have been used to strengthen reinforced concrete (RC) walls with openings, these being either to create a frame around the opening using RC/steel membersor to increase the cross-sectional thickness. Currently, intervention in existing buildings must be minimal in order to minimise inconvenience caused by limiting the use of the structure during repairs. One option is to use externally-bonded fibre-reinforced polymers (FRPs). In this study, the author reports on an experimental investigation of the effectiveness of carbonFRP (CFRP)–based strengthening for restoring the axial capacity of a solid reinforced concretewall after cutting openings. Nine half-scale specimens, designed to represent typical wall panels in residential buildings with and without door-type openings, were tested to failure. The walls were tested in two-way action and subjected to axial loading with low eccentricity (defined as one sixth of the wall’s thickness) along the weak axis to represent imperfections due to thickness variation and misalignment of the panels during the construction process. An extensive instrumentation scheme was used to monitor the specimen’s behaviour during the loading cycles. In addition to classical approaches for measuring strains and displacements, optical 3D measurements were also acquired using the digital image correlation (DIC) technique. These provided better overviews of the failure mechanism by recording the crack pattern development and deformation of the walls throughout the loading history. Reducing the cross-sectional area by cutting out openings i.e. 25% (hereafter referred to as small opening) and 50% (hereafter referred to as large opening) led to 36% and 50% reductions in peak loads, respectively. In both situations the failure was brittle due to crushing of concrete with spalling and reinforcement buckling. The CFRP strengthening increased the axial capacity of walls with small and large openings by 34 – 50% and 13 – 27%, respectively. This partially restored theircapacities to 85 – 95% and 57 – 63% of their precutting capacity (i.e. solid wall), respectively. A procedure based on a rigid-plastic approach for evaluating the ultimate load of walls with cut-out openings that have been strengthened with FRPs was also proposed in this study. Predictions made using the proposed method agree closely with experimental results. / <p><strong>Examining Committee</strong>: Professor Karin Lundgren, Division of Structural Engineering, Department of Civil and Environmental Engineering, Chalmers University of Technology, Gothenburg, Sweden</p><p>Professor Henrik Stang, Section for Structural Engineering, Department of Civil Engineering, Technical University of Denmark, Lyngby, Denmark</p><p>Professor Mats Oldenburg, Division of Mechanics of Solid Materials, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden</p>
|
546 |
Platforms in industrialised house-building / Plattformar i industriellt bostadsbyggandeJansson, Gustav January 2013 (has links)
Demands for shorter lead times, customized buildings and high quality deliveries drive house-building firms to systematise work in their supply chains. A practice of reusing processes and technical solutions leads to the formation of platforms in industrialised house-building. Product platforms originate from industries employing a make-to-order strategy, where platforms are used to achieve efficient design and product development work. The house-building design phase, integrated in an engineer-to-order supply chain, has been identified as crucial for achieving an efficient production. In the design phase, design work combines platform predefinitions with project requirements. The aim of this thesis is to describe how house-building platforms are systematised, as well as propose a framework for the use and development of platforms over time.To expand the knowledge development and use of platforms in house-building design, case studies were conducted that collected data from interviews and observations as well as using archival data at two different companies. One was a Swedish industrialised house-building company, with many levels of platform predefinitions that use off-site production; the other was a Swedish company using several platforms employing industrialised methods for on-site production. The design work of over sixty building projects has been studied through following project managers, engineers and platform developers in their day-to-day work. The use in projects of predefinitions of functional requirements, components, processes and relationships has been compared and contrasted using platform and engineering design theories.The result of this research shows that, in an engineer-to-order production strategy, creative and systematic designs are combined. This combination is needed to create product uniqueness and thus it is important to understand and maintain the balance between commonality and distinctiveness within the platforms used in housebuilding projects. Continuously changing demands in construction hinder a fully predefined platform. Long cycle times in house-building demand a continuous flow of knowledge between platform and day-today work in projects. Hence, platform versions and product variants often become non-functional in an engineer-to-order supply chain, so methods to support the knowledge flow become necessary. The research findings show that design work, integrated into the supply chain of house-building, is a source of experience feedback for platformdevelopment.The conclusion is that a movement towards mass customization in house-building is possible using the product platform concept, if the platform is applied to projects using support methods with experience being continuously fed back to the platform from house-building projects. However, there is a risk that use of predefinition in platforms is made without considering the consequences. The reuse of predefined processes could limit innovation capability, increase the risk for imitation and organisational inertia. Too great a restriction of components in the house-building platform could limit the product offer and narrow the market segment. The study also shows that predefinitions might lead to an unbalanced focus on buildability instead of client satisfaction. / Krav på kortare ledtider, kundanpassat byggande och hög kvalitet på leveranser tvingar byggföretagen att systematisera arbetet i sina produktionsled. Genom att återanvända processer och tekniska lösningar kan det dagliga arbetet utvecklas inom plattformar för industriellt bostadsbyggande. Produktplattformar med syfte att stödja effektiv design och produktutveckling baseras på strategier för tillverka mot order produktion. Projekteringsfasen, som en integrerad del avbostadsbyggandets produktionskedja, har identifierats som avgörande för att erhålla en effektiv produktion. I projekteringsfasen kombineras fördefinitioner från plattformen med projektets krav. Syftet med denna avhandling är att beskriva hur bostadsplattformar kan systematiseras, och föreslå ett ramverk för användning och utveckling av plattformar över tid.För att fördjupa kunskapen om hur plattformar används och utvecklas i bostadsprojektering har fallstudier genomförts genom insamling av data via intervjuer, observationer och arkiv hos två olika företag. Ett svenskt industriellt bostadsbyggande företag med hög grad av fördefinering för prefabricerad produktion. Det andra företaget använder flera plattformar och industrialiserade metoder för platsbyggande produktion. Projekteringsarbete har studerats i över sextio bostadsprojekt genom att följa projektledare, ingenjörer och plattformsutvecklare i deras dagliga arbete. Användandet av fördefinierade funktionskrav, komponenter, processer och relationer har analyserats mot plattforms och designteorier.Forskningsresultatet visar att kreativt och systematiskt arbete kombineras i en konstruera-mot-order kontext. Kombinationen är nödvändig för produktens unikitet, och därför är balansen mellan repetition och variation viktigt för förståelse om och andvändande av plattformar i husbyggnadsprojekt. Ständigt föränderliga krav inom byggandet hindrar en fullt fördefinierad plattform. Långa cykeltider i bostadsbyggandet ställer krav på ett kontinuerligt flöde av kunskap mellan plattform och det dagliga arbetet inom byggprojekten. Plattformsversioner och produktvarianter blir ofta icke-funktionella i en konstruera-mot-order kontext, metoder behövs därför för att stödja flödet. Forskningsresultaten visar på att projekteringsarbete, integrerat i bostadsbyggandets leveranskedja, är en källa för erfarenhetsåterföring i utveckling av en plattform.Slutsatserna visar att en förändring mot effektivt kundanpassat bostadsbyggandet är möjlig om plattformar används tillämpade i projekt med stödjande metoder och kontinuerlig erfarenhetsåterföring från byggprojekten till plattformen. Däremot, finns det en risk att plattformar fördefinieras utan att reflektera över konsekvenserna. Användning av fördefinierade processer skulle kunna begränsa innovationsförmågan, öka risken för imitation och skapa förändringsmotstånd inom organisationer. Detaljering av komponenter i en bostadsplattform kan begränsa produktutbudet och minska marknadssegmentet. Studien visar också att fördefinitioner kan leda till obalanserad fokusering på byggbarhet istället för funktionalitet för kunden. / Godkänd; 2013; 20131003 (gusjan); Tillkännagivande disputation 2013-10-29 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Gustav Jansson Ämne: Träbyggnad/Timber Structure Avhandling: Platforms in Industrialised House-Building Opponent: Professor Brian Atkin, Project Management Academy, Queensland University of Technology, Brisbane, Australien Ordförande: Docent Helena Johnsson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Torsdag den 21 november 2013, kl 10.00 Plats: F531, Luleå tekniska universitet
|
547 |
Stommaterialets klimatpåverkan : En jämförande studie mellan stommaterialen trä och betong ur ett livscykelperspektiv applicerat på en passivhusförskolaAlmblad, Cecilia January 2017 (has links)
No description available.
|
548 |
A strategic decision making framework for organisational BIM implementationChen, Keyu January 2015 (has links)
Decision making during the adoption of Building Information Modelling (BIM) in current AEC projects is believed as a key element to improve both BIM performance and project outcome. In order to provide the most informed decision and strategic plan, two vital elements are required: a comprehensive set of decision making criteria and a reasonable priority system. The literature analysis has revealed that existing assessment frameworks have limitations concerning these two elements. Therefore, this research has been designed to develop a more effective BIM evaluation Framework (BeF), to assist new BIM users and also provide a more effective implementation approach for BIM. In order to accomplish this objective, research steps of theoretical and empirical nature have been adopted: (a) a multi-dimensional BIM implementation Framework (BiF) was proposed based on the literature review; (b) use of a case study to test the proposed BiF on a real-life project; (c) a questionnaire approach to test the comprehensiveness of the proposed BiF on an industry level; (d) applying the Delphi method to further refine the proposed criteria in a specific context; (e) using the Analytical Hierarchy Process (AHP) to develop a BeF and providing priority shifting for a more preferable strategic goal in Arup ShenZhen office (ASZ); (f) developing a validation system to prove the efficacy of the proposed BeF. The adoption priority and approach of BIM could be influenced by policies, culture, business structure, legislation etc. As a result, a specific context, China has been selected for this work. The research result could assist decision making in BIM management in the ASZ for a higher BIM performance. The framework by the Delphi method is suitable for the selected context: China. The proposed Delphi and AHP methodological framework can be replicated to assist decision making of BIM management in any AEC organisation.
|
549 |
Crack detection in frames using natural frequency degradationsLabib, Amr January 2016 (has links)
Crack detection at an early stage can prevent catastrophic structural failures. In this thesis, the inverse problem of crack detection in frames is studied. The direct problem of calculating the natural frequencies of beams and frames with multiple cracks is first tackled. A new method for natural frequency calculation is devised. The cracks are modelled as rotational springs. 4 × 4 dynamic stiffness matrices for beams are evaluated in a recursive manner, according to the number of cracks, by applying partial Gaussian eliminations. The resulting transcendental eigenvalue problem is solved using the Wittrick–Williams algorithm to extract the natural frequencies. Additional sign counts resulting from the partial Gaussian eliminations must be accounted for when applying the algorithm. The dynamic stiffness matrix of a frame with multiply cracked members is then assembled. The natural frequency calculation method forms a basis for detecting a single crack in a frame using only natural frequency measurements. Each frame member is discretised into a number of points. Selected natural frequencies are calculated accurately in the uncracked case and when the crack is placed individually at each discretisation point. The variation between the uncracked and cracked frequencies is normalised giving a number of curves corresponding to the selected frequencies. The normalisation is then applied on the measured frequencies. For noise free measurements, point crack locations are obtained. Applying the principles of interval arithmetic, noisy measurements give crack location ranges. Empirical probability distributions are used to graphically represent these ranges and their relative probabilities. Crack severity ranges are then obtained. The detection method is validated experimentally on a frame with scaled down dimensions. The fast Fourier transform is used to convert the time domain vibration signal into the frequency domain. Using higher order natural frequencies, two enhancement procedures for the detection method are devised and applied theoretically.
|
550 |
Produktsäkerställning av Deje trä´s bodunderlag : Hållfasthetsberäkningar, k-ritningar, monteringsanvisningar och kvalitetsmärkningSvensson, Emil, Häggblom, Kristoffer January 2017 (has links)
Byggbranschen står idag inför en förändring gällande bodetablering. På basen av ett prejudikat i mark- och miljööverdomstolen kan nu bygglov komma att krävas vid uppställning av byggmoduler. Byggloven medför ett större krav på bygghandlingar för grunden och modulerna. Deje trä är i dagsläget en stor tillverkare av ett beprövat etableringssystem, Dejegrunden. Kraven på handlingar medför att Deje träs produkt måste uppdateras med nya hållfasthetsberäkningar enligt EK05 och nya detaljerade konstruktionsritningar. I samband med arbetet att upprätta bygghandlingar görs även en säkerställning av produktens kvalitet genom en undersökning för att kontrollera om en P-märkning är möjlig. Märkningen är en stark symbol inom byggbranschen som ställer höga krav på tillverkningsprocess, materialanvändning och brukarens säkerhet. Monteringsanvisningar tillverkas för företagets och brukarens säkerhet vid etablering. Bodgrundens flexibilitet innebär att uppställningen kan variera, vilket medför att hållfastheten skiljer sig åt i olika grundsystem. Resultatet visar systemens maximala lastkapacitet som är högst 90 kN. Ritningar och anvisningar tillverkas enligt branschnormer och anvisningarna har inspirerats av tidigare upplägg från Deje trä. En P-märkningen bedöms vara möjlig och ett underlag för ett vidare arbete till att verkställa en dylik märkning är framlagd. / Today the building industry faces changes in regard to the establishment of building modules. A precedent was set in court which stipulates that building permits may now be required for the formation of building modules at construction sites. The permits entail a requirement of building documents for the base and modules. At present Deje trä is a leading production company of “Dejegrunden”, a base for building modules. The demand for documents require changes to be made to the product´s existing documentation, new strength calculations in accordance with the new euro codes, EC05 and new detailed construction drawings are needed. In conjunction with the new documentation a product quality assessment is done to assess the possibility of executing a P-marking of the product. The marking is a strong indicator within the building industry as it puts great demand on the production process, material and safety when used. The assembly instructions are made to ensure the users’ and the company’s liability when in use. The flexibility of the module base means that a variety of modules can be established and in turn a variety of calculations is needed. The result indicates that the maximum capacity of a single support, which is 90 kN. The drawings and instructions were made in accordance with the standards of the building industry and previous setups of the company. The documentation of the work is deemed sufficient for an execution of quality labeling of the product. / Hållfasthetsberäkningar, k-ritningar, monteringsanvisningar, kvalitetsmärkning
|
Page generated in 0.0363 seconds