Dissertations / Theses on the topic 'Shuar architecture'

A new version of EN 1992-1-1, Eurocode 2 for Design of Concrete Structures, is under development and one of the most discussed topics is shear capacity for prestressed concrete beams without shear reinforcement, partly because shear failure occurs suddenly and can have catastrophic consequences. For the new version of Eurocode, there are a total of three proposed equations to replace the two equations that currently exist in EN 1992-1-1 for shear capacity of prestressed concrete beams without shear reinforcement. One of the proposed equations is intended to replace the equation intended for beam regions where bending cracks do not occur. The other two equations are proposed for beam regions where bending cracks occur. One of the proposed equations for beam regions with bending cracks, is based on critical shear crack theory and takes the normal force in consideration, while the other equation for beam regions with bending cracks is like the one found today in Eurocode, an empirical equation, where the contribution of normal force is empirical. In this thesis, all equations have been set against each other and compared with the help of nonlinear finite element analyzes and experiments which Dr. De Wilder has done in his doctoral thesis. The impact of the prestressing force on the shear force capacity of beams has also been investigated. The results show that the equations for beam regions that do not have bending cracks give identical shear force capacities. While the equation which is based on critical shear crack theory takes the shear span into consideration and captures the effect of the shear span correctly, which the other proposed equation and the one found in Eurocode today do not and are on the unsafe side for increasing shear spans. Furthermore, it turned out that the equation which is based on critical shear crack theory was rather conservative, while the equation that exists today in Eurocode gives approximately the same shear capacity as the other proposed equation. Furthermore, it was found that if the amount of longitudinal reinforcement is reduced, at the same time as the prestressing force is unchanged, an insignificant reduction in the shear capacity on prestressed concrete beams is obtained.
En ny version av EN 1992-1-1, Eurokod 2 Dimensionering av betongkonstruktioner, är under utveckling och ett av de mest diskuterade ämnena är tvärkraftskapacitet för förspända betongbalkar utan skjuvarmering, bland annat eftersom huvudspänningsskjuvbrott uppstår plötsligt och kan få katastrofala konsekvenser. Till den nya versionen av Eurokoden finns det totalt tre föreslagna ekvationer för att ersätta de två ekvationer som för närvarande finns i EN 1992-1-1 för tvärkraftskapacitet för förspända betongbalkar utan skjuvarmering. En av de föreslagna ekvationerna är tänkt att ersätta ekvationen avsedd för balkregioner där böjsprickor ej uppstår. De andra två ekvationerna är föreslagna för balkregioner där böjsprickor uppstår. En av de föreslagna ekvationerna för balkregioner med böjsprickor är baserad på kritisk skjuvsprickteorin och tar hänsyn till normalkraftens bidrag till tvärkraftskapaciteten, medan den andra föreslagna ekvationen för balkregioner med böjsprickor är likt den som idag finns i Eurokoden, en empirisk ekvation, där normala kraftens bidrag är baserad på ett empiriskt tillägg. I detta examensarbete har alla ekvationer ställts mot varandra och jämförts med hjälp utav icke-linjär finit-elementanalyser samt experiment som Dr. De Wilder gjort i sin doktorsavhandling. Vidare har också förspänningskraftens påverkan på balkars tvärkraftskapacitet undersökts. Resultaten visar att ekvationerna för balkregioner som ej har böjsprickor ger identiska tvärkraftskapaciteter. Medan ekvationen som är baserad på kritisk skjuvsprickteorin tar hänsyn till skjuvspännvidd och fångar effekten av skjuvspännvidden korrekt, vilket den andra föreslagna ekvationen och den som finns i Eurokoden idag inte gör och är på den osäkra sidan för ökad skjuvspännvidd. Dessutom visade det sig att ekvationen som är baserad på kritisk skjuvsprickteori är tämligen konservativ, medan ekvationen som finns idag i Eurokoden ger ungefär samma tvärkraftskapacitet som den andra föreslagna ekvationen. Vidare visade det sig att ifall man minskar mängden längsgående armering, samtidigt som förspänningskraften är oförändrad, så fås en obetydlig minskning utav tvärkraftskapaciteten på förspända betongbalkar.

The shear failure mechanisms of flexural reinforced concrete (RC) members is highly complex; its precise details cannot be explained with simple analytical relationships, and are the topic of considerable scientific debate. The studies described and examined the three most used shear theories in the world – the fixed angle truss model (45°TM), the variable angle truss model (VAT), and modified compression field theory (MCFT). These three theories rest on the assumption that a beam loaded in shear behaves as a truss. However, this assumption is applied in different ways in various codes. In this thesis, three major standards, each of which uses a different implementation of these theories (CEN, 2005; ACI-318, 2008; CSA-A23.3, 2009), were used to predict the shear force capacity of a RC railway bridge that was strengthened in flexure with near surface mounted (NSM) carbon fibre reinforced polymers (CFRP) and then tested to failure. The data obtained in this test indicated that the codes underestimated the real shear behaviour of the bridge. There are some accepted reasons for such inaccuracies, namely the use of empirically derived equations in the ACI (2008) and CSA (2009) standards and the omission of the concrete contribution in CEN (2005). Moreover, the NSM reinforcement material used exhibits elastic behaviour until the point of failure; it was found that the use of such materials introduces further decreases the accuracy of the models’ predictions. The strains that developed in the area of the bridge where shear failure was expected were monitored throughout the test using a specially-developed photographic method. The results obtained with this method were promising, especially for research purposes, since it generated reliable data using relatively affordable tools.The use of FRP for shear strengthening introduces further complications to the problem of shear in reinforced concrete members because introduces two new failure modes: debonding at the concrete interface and fibre rupture of the FRP. Extensive research has been carried out on FRP shear strengthening around the world. Much of the data gathered in these studies has been compiled in a database. By analysing this large database, it was found that the effectiveness of FRP shear strengthening is influenced by many factors, including the properties of the FRPs, the FRP strengthening configuration used, the nature of the beam’s cross-section, the shear span to depth ratio, the presence of stirrups, and the nature of the tensile reinforcement. Analysis of this database also demonstrated that most of the studies reported in the literature had focused on investigating the influence of the properties of the FRPs and the different configuration systems, and that the other factors mentioned above have been sparsely investigated if not totally ignored. The strengthening configuration and the amount of fibres influence the failure mode of the FRP and the shear force that it can carry. It appears that the side-bonded and the U-wrapped configurations are most prone to failure by debonding. This is consistent with the findings of various small experimental programs, and was confirmed by analysis of the larger dataset. These findings are relevant because failure of the FRP by debonding is more complex mechanism than is the rupture of the fibres mechanism. As is shown in this thesis, the extent to which the FRP variables (properties and strengthening configuration) can affect the point at which failure occurs and the mode by which it happens is dependent on the quantity of stirrups and tensile reinforcement in the beam, to the position of the load in relation to the size of the cross section (shear span to depth ratio), the type of strengthening configuration, the concrete and FRP properties. For design purposes, it is important to predict the shear failure of FRP shear strengthened beams with as much accuracy as possible. Therefore, a design model for debonding of the shear strengthening of concrete beams with FRP was developed and the limitations of the truss model analogy were highlighted. The fracture mechanics approach was used to analyse the behaviour of the bond between the FRP composites and the concrete. In this model, of the parameters examined, the fracture energy of concrete and the axial rigidity of the FRP are considered to be the most important. The effective strain in the FRP when debonding occurs was determined and the limitations of the anchorage length over the cross section were analysed; ultimately, a simple iterative method for shear debonding was proposed. Since the model’s predictions were considered satisfactory but not really precise, an extensive review of the literature was conducted. All of the significant theoretical models for predicting the shear capacity of FRP strengthened RC beams that have been reported over the years were analysed and commented on, and their predictions were compared to the results recorded in a preliminary experimental database. The predictions of the models that are most widely used in design were compared to the experimental results reported in the database; the model developed by the author was evaluated alongside these more established models. All of the models, including that presented in this thesis, were found to generate inaccurate predictions, but two models have been calibrated so as to provide safe estimates of the FRP shear capacity. Finally a new model for FRP shear strengthening was proposed for use in engineering. The new model was developed on the basis of an analysis of the contents of the database of experimental findings. The model incorporates several design equations adopted from various models and is set up for engineering use. The predictions of the shear force carried by the FRP strengthening material are found to be conservative.
Godkänd; 2011; 20110328 (gabsas); DISPUTATION Ämnesområde: Konstruktionsteknik/Structural Engineering Opponent: Professor Giorgio Monti, University of Rome, Italy Ordförande: Professor Björn Täljsten, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Fredag den 29 april 2011, kl 13.00 Plats: F1031, Luleå tekniska universitet

This thesis presents results from testing of interlocking compressed earth block (CEB) masonry shear walls. CEBs are low strength earth masonry units sometimes stabilized with cement or lime. The interlocking compressed earth blocks (ICEBs) used in this experiment are dry stacked interlocking hollow units, which can be reinforced and grouted after they are laid. Although significant research has been undertaken to optimize the material properties of CEBs, little has been done to investigate the performance of structural systems currently being built using this technology. Test results are reported for three 1800 mm x 1800 mm wall specimens constructed with cement stabilized ICEBs and subjected to cyclic in-plane lateral loading. Wall specifications were varied to identify the shear performance of partial and fully grouted walls, and to observe the performance of a flexure dominated wall panel. It was determined that the shear strength of fully grouted walls is significantly higher than that of partially grouted walls and calculation of capacity based on current ACI 530-08 masonry provisions significantly overestimates the shear strength of ICEB wall panels. Based on the observed performance, recommendations are made for limiting the calculated nominal shear strength in design. Results also indicate that calculations based on simple bending theory conservatively predict the flexural strength of a fully grouted ICEB wall. Discussion of ICEB material properties and recommendations for design and construction procedures are included.

This study developed a nonlinear constitutive model for a sustainable orthotropic material. Existing methods for constitutive models of wood were improved upon to include the nonlinear stress-strain response not only in the two orthogonal axes but at any orientation to the strong axis of the material. This method also simplifies the nonlinear stress-strain relationships into bilinear stress-strain curves which can be valuable in hand calculations as well as finite-element analyses. The effectiveness of the proposed constitutive model is demonstrated by comparing bilinear stress-strain predictions to experimental data.

Historical accidents and experimental investigations have made apparent that blast loaded concrete members are prone to fail in brittle shear rather than a ductile flexure mode. Air blasts from accidental detonations or explosives may cause severe damage to buildings and infrastructure and it is of great importance that load carrying members can withstand the impulse that arise to avoid progressive collapses. The aims of this thesis are, through explanation of blast loads as dynamic loads acting on structures and measuring of the effects of blast loads on reinforced concrete beams with shear reinforcement, to understand the mechanisms governing shear failure. Two hypotheses are therefore tested: That for a reinforced concrete beam with shear reinforcement, the mechanism governing dynamic shear failure is similar to that of static shear failure and that blast induced shear failure in reinforced concrete beams can be prevented through a sufficient amount of shear reinforcement. To meet the stated aims and test the hypotheses, a literature study was conducted together with numerical simulations using explicit non-linear finite element analysis software LS-Dyna.Previous experimental investigations on blast loaded reinforced concrete beams have displayed a possible shift in failure mode from a ductile flexural failure at static loading to a brittle shear failure at dynamic loading. The shifting may be a property of higher exciting frequencies of blast loads, inducing modes of vibration with larger portions of shear energy. The results obtained from the numerical analyses indicated that an increased ratio of shear reinforcement reduces the risks of a brittle shear failure as well as decrease beam deflections and concrete strains, while increasing strains in the tensile reinforcement.Analysis of the shear capacity and shear reinforcement design through methods given in Eurocode 2 and FKR 2011 were considered as supplementary to the FE analysis. FKR 2011 provided accurate estimations of the maximum dynamic support reactions. Eurocode 2 uses a more conservative approach resulting in lower values of the design shear strength.The conclusions are that for the given beam and blast load, brittle shear failures may be prevented through reduction of the spacing and increase of the bar diameter of the shear reinforcement. The increased plastic strain of the tensile reinforcement as well as measurements of shear crack widths, support reactions and strains in the concrete suggests that the beams with large ratio of shear reinforcement exhibit more ductile behaviour without reaching failure.
Historiska händelser och experimentella undersökningar har gjort gällande att betongelement utsatta för luftstötvåg är benägna att gå till spröda skjuvbrott snarare än sega böjbrott. Luftstötvågor från oavsiktliga detonationer eller explosivt gods kan orsaka svåra skador på byggnader och anläggningar och det är därför viktigt att bärande strukturer kan motstå impulsen som uppstår för att fortskridande ras ska undvikas. Målen med detta examensarbete är att, genom att förklara det dynamiska beteendet hos luftstötvågor som belastar konstruktioner och mätning av de effekter som uppstår av luftstötvågor på armerad betong med tvärkraftsarmering, förstå de mekanismer som ligger till grund för skjuvbrott. Som påföljd testas två hypoteser: Att mekanismerna som ligger till grund för dynamiska skjuvbrott hos armerade betongbalkar med tvärkraftsarmering är liknande som för de som styr statiska skjuvbrott, och att skjuvbrott till följd av luftstötvågor kan förhindras genom att förse balken med tillräcklig tvärkraftsarmeringsinnehåll. För att nå målen och testa hypoteserna så genomfördes en litteraturstudie tillsammans med numeriska simuleringar med explicit icke-linjär finita elementanalys i kommersiella programvaran LS-Dyna. Tidigare experimentella undersökningar av armerade betongbalkar utsatta för luftstötvåg har visar på en förflyttning i brottmod, från sega böjbrott vid statisk belastning till spröda skjuvbrott vid dynamisk belastning. Förflyttningen kan härstamma från luftstötvågens frekvensinnehåll som framkallar högre vibrationsmoder med större andel skjuvenergi.De erhållna resultaten från de numeriska analyserna indikerar att ett ökat tvärkraftsarmeringsinnehåll minskar risken för spröda skjuvbrott, minskar utböjning och töjningar I balken samtidigt som töjningar i dragarmeringen ökar.Analyser av tvärkraftskapaciteten och dimensionering av tvärkraftsarmering genom metoder givna i Eurocode 2 och FKR 2011 användes som komplement till finita elementanalysen. FKR 2011 gav träffsäkra uppskattningar av de dynamiska störreaktionerna grundade i dynamisk jämvikt. Emellertid var Eurocode 2 det mer konservativa tillvägagångssättet, vilket resulterade i lägre dimensionerande tvärkraftskapacitet. Slutsatserna som drogs var att, för den givna balken och luftstötvågen så kunde spröda skjuvbrott motverkas genom minskning av avstånden mellan tvärkraftsarmeringen och ökning av stångdiametern. De ökade plastiska töjningarna i dragarmeringen tillsammans med mätningar av skjuvsprickornas bredd, stödreaktionerna och töjningarna i betongen föreslår att balkarna med högt tvärkraftsarmeringsinnehåll visar på ett segare beteende utan att gå till brott.

PERFORMANCE-BASED ANALYSIS OF A REINFORCED CONCRETE SHEAR WALL BUILDING Garrett Richard Hagen In this thesis, a special reinforced concrete shear wall building was designed per ASCE 7-05, and then the performance was investigated using the four analysis procedures outlined in ASCE 41-06. The proposed building was planned as a 6-story office building in San Francisco, CA. The structural system consisted of a two-way flat plate and reinforced concrete columns for gravity loads and slender structural walls for seismic loads. The mathematical building models utilized recommendations from ASCE 41-06 and first-principle mechanics. Moment-curvature analysis and fiber cross-section elements were used in developing the computer models for the nonlinear procedures. The results for the analysis procedures showed that the building met the Basic Safety Objective as defined in ASCE 41-06. The performance levels for the nonlinear procedures showed better building performance than for the linear procedures. This paper addresses previously found data for similar studies which used steel special moment frames, special concentric braced frames, and buckling restrained braced frames for their primary lateral systems. The results showcase expected seismic performance levels for a commercial office building designed in a high seismicity region with varying structural systems and when using different analysis procedures. Keywords: reinforced concrete structural walls, shear walls, performance-based analysis, ETABS, Perform-3D, flat plate, two-way slab.

After only two years of service, extensive cracking was found in the webs of two light-rail commuter line bridges in Stockholm, the Gröndal and Alvik bridges. Due to this incident it was found necessary to study the means available for analysing shear cracking in concrete structures subjected to in-plane stresses. The aim of this PhD project is to study shear cracking with these two bridges as reference. In this thesis, the first part aims to study the possibility of using finite element analysis as a tool for predicting shear cracking for plane state stresses. The second part is concerning how the shear cracks are treated in the concrete design standards.

Shear cracking in reinforced beams has been studied with non-linear finite element analyses. In these analyses the shear cracking behaviour was compared to experiments conducted to analyse the shear failure behaviour. Finite element analyses were performed with two different FE programs Abaqus and Atena. The material model used in Atena is a smeared crack model based on damage and fracture theory with either fixed or rotated crack direction. The material model used in Abaqus is based on plasticity and damage theory. The fixed crack model in Atena and the model in Abaqus gave good results for all studied beams. For the two studied deep beams with flanges the results from the rotated crack model were almost the same as obtained with the fixed crack model. The rotated crack model in Atena gave though for some beams a rather poor estimation of the behaviour.

The calculation of crack widths of shear cracks has been studied for the long-term load case in the serviceability state for the Gröndal and Alvik bridges, with the means available in the design standards. The methods based on the crack direction corresponding to the principal stress and do not include the effect of aggregate interlocking seems to be too conservative. Two of the studied methods included the effect of aggregate interlocking, it was made either by introducing stresses in the crack plane or implicitly by changing the direction of the crack so that it no longer coincide with the direction of principal stress. For calculations based on probable load conditions, these methods gave estimations of the crack widths that were close to the ones observed at the bridges. Continuous measurements of cracks at the Gröndal and the Alvik bridges have also been included. Monitoring revealed that the strengthening work with post-tensioned tendons has, so far, been successful. It also revealed that the crack width variations after strengthening are mainly temperature dependent where the daily temperature variation creates movements ten times greater than those from a passing light-rail vehicle. Monitoring a crack between the top flange and the webs on the Gröndal Bridge showed that the top flange was moving in a longitudinal direction relative to the web until the strengthening was completed. The crack widths in the sections strengthened solely by carbon fibre laminates seem to increase due to long-term effects.

Punching shear is a failure mechanism caused by concentrated loads, creating a crack pattern that resembles a cone shape or piece of pie starting from the top surface of the slab and prolongs downwards. When the total shear force is greater than the shear resistance of the slab, it may eventually lead to punching shear failure. It can be visualized as the column punches through the slab. Punching shear is very brittle and occurs all of a sudden. It is believed that the slab is subjected to hogging moments over the column in both directions, i.e. parallel and perpendicular to the free edge. Non-linear finite element analyses (NLFEA) has been used to study the cracking and failure mechanism for the reinforced slab. It is a slab over the edge support without clamping stiffness, therefore simulating the slab shear mechanism over a slender steel column is carried out in this study. The analyses has been performed using the software ATENA 3D Engineering developed by Červenka Consulting. Since the symmetry has been taken into account over an edge column, only one half of the cross-section has been modeled, with a symmetry line passing vertically through the slab and column. It can be summarized that the failure encountered around the column has a conical shape crack pattern similar to the ones encountered when punching shear occurs. However, it is important to note that this failure is not due to classic punching shear, but instead due to shear cracks developing around the column in both directions, both parallel and perpendicular to the free-edge. Three models (C1, C2, and C3) are studied to evaluate the impact that the length of the lower leg of the c-bar reinforcement has during failure. As mentioned earlier above, the crack propagation during punching shear begins from the upper surface of the slab and prolongs downwards diagonally towards the bottom of the slab and adjacent to the column. However, the crack propagation in the strip perpendicular to the free edge in all three models initiate from the bottom and propagate upwards. It can be concluded that the length reduction of the lower leg of the c-bars as a consequence reduced the shear strength capacity of the slab around the steel-plate. The reason for this is due to a reduction in maximum peak load when the lower leg of the c-bars were reduced. Consequently, this leads to a decrease in shear strength capacity of the slab and an earlier failure, where the inner-span was not able to take additional loads which could have led to greater deflections.
Genomstansning är en brottmekanism orsakad av koncentrerade laster, vilket skapar ett sprickmönster i likhet med en konfrom ellet en bit av paj som börjar från den övre ytan av plattan och förlängs nedåt. När den totala skjuvkraften är större än skjuvmotståndet i plattan , kan det så småningom leda till ett genomstansningsbrott. Det kan visualiseras som att pelaren stansar eller slår igenom plattan. Genomstansning är ett mycket sprött brott och inträffar helt plötsligt. Det antas att plattan utsätts för negativt moment ovanför pelaren i båda riktningarna, d.v.s såväl parallellt som vinkelrät mot den fria kanten. Icke-linjära finita elementanalyser (NLFEA) har använts för att studera sprickbildnings och brottmekanismen för den förstärkta plattan. Det är en platta över kantstödet utan någon fast inspänd styvhet, därför simuleras skjuvmekanismen för plattan över en slank stålpelare i denna studie. Analyserna har utförts med programvaran ATENA 3D Engineering som utvecklats av Červenka Consulting. Eftersom hänsyn har tagits till symmetrin över en kantpelare har endast halva tvärsnittet modellerats, med en symmetrilinje som går vertikalt genom plattan och pelaren. Det kan sammanfattas att brottet som påträffas runt pelaren har en konisk form med ett sprickamönster som liknar de som påträffas vid genomstansning. Det är dock viktigt att notera att detta brott inte orsakats av klassisk genomstansning, utan istället på grund av skjuvsprickor som utvecklast runt pelaren i båda riktningarna, såväl parallellt som vinkelrät mot den fria kanten. Som det tidigare nämnts ovanför börjar sprickan vid genomstansning från plattans övre yta och förlängs nedåt diagonalt mot bottenplattan och intill pelaren. Sprickmönstret i remsan vinkelrät mot den fria kanten i alla tre modellerna (C1, C2 och C3) initierar dock från botten och sprids uppåt. Slutsatsen kan dras att längdminskningen av c-stängernas underben minskade skjuvhållfastheten hos betongplattan runt pelaren. Anledningen till detta beror på en minskning av maximal toppbelastning när c-stängernas underben reducerades. Följaktligen leder detta till en minskning av skjuvhållfastheten och ett tidigare brott, där den inre spännvidden inte kunda ta ytterligare belastningar som kunde ha lett till större nedböjningar.

The construction industry is currently developing and evolving towards more automated and optimized processes in the project design phase. One reason for this development is that computational power is becoming a more precise and accessible tool and its applications are multiplying daily. Complex structural engineering problems are typically time-consuming with large scale calculations, resulting in a limited number of evaluated solutions. Quality solutions are based on engineering experience, assumptions and previous knowledge of the subject.The use of parametric design within a structural design problem is a way of coping with complex solutions. Its methodology strips down each problem to basic solvable parameters, allowing the structure to be controlled and recombined to achieve an optimal solution.This thesis introduces the concept of parametric design and optimization in structural engineering practice, explaining how the software application works and presenting a case study carried out to evaluate the result. In this thesis a parametric model was built using the Dynamo software to handle a design process involving a common structural engineering problem. The structural problem investigated is a reinforced concrete slab supported by a centre column that is exposed to punching shear failure. The results provided are used for comparisons and as indicators of whether a more effective and better design has been achieved. Such indicators included less materials and therefore less financial cost and/or fewer environmental impacts, while maintaining the structural strength. A parametric model allows the user to easily modify and adapt any type of structure modification, making it the perfect tool to apply to an optimization process.The purpose of this thesis was to find a more effective way to solve a complex problem and to increase the number of solutions and evaluations of the problem compared to a more conventional method. The focus was to develop a parametric model of a reinforced concrete slab subjected to punching shear, which would be able to implement optimization in terms of time spent on the project and therefore also the cost of the structure and environmental impact.The result of this case study suggests a great potential for cost savings. The created parametric model proved in its current state to be a useful and helpful tool for the designer of reinforced concrete slab subjected to punching shear. The result showed several solutions that meet both the economical and the punching shear failure goals and which were optimized using the parametrical model. Many solutions were provided and evaluated beyond what could have been done in a project using a conventional method. For a structure of this type, a parametric strategy will help the engineer to achieve more optimal solutions.
Just nu utvecklas Byggbranschen mot mer automatiserade och optimerade processer i projektdesignfasen. Denna utveckling beror till stor del på teknikutveckling i form av bättre datorprogram och tillgänglighet för dessa. Traditionellt sett löses komplexa konstruktionsproblem med hjälp av tidskrävande och storskaliga beräkningar, vilka sedan resulterar i ett begränsat antal utvärderade lösningar. Kvalitets lösningar bygger då på teknisk erfarenhet, antaganden och tidigare kunskaper inom ämnet.Användning av parametrisk design inom ett konstruktionsproblem är ett sätt att hantera komplexa lösningar. Dess metod avgränsar varje problem ner till ett antal lösbara parametrar, vilket gör att strukturen kan kontrolleras och rekombineras för att uppnå en optimal lösning.Denna avhandling introducerar begreppet parametrisk design och optimering i konstruktionsteknik, den förklarar hur programvaran fungerar och presenterar en fallstudie som genomförts för att utvärdera resultatet. I denna avhandling byggdes en parametrisk modell med hjälp av programvaran Dynamo för att hantera en designprocess av ett vanligt konstruktionsproblem. Det strukturella problemet som undersökts är en armerad betongplatta som stöds av en mittpelare, utsatt för genomstansning. Resultaten används för att utvärdera om en bättre design med avseende på materialanvändning har uppnåtts. Minimering av materialanvändning anses vara en bra parameter att undersöka eftersom det ger lägre kostnader och/eller lägre miljöpåverkan, detta undersöks under förutsättning att konstruktionens hållfasthet bibehålls. En parametrisk modell gör det möjligt för användaren att enkelt modifiera en konstruktionslösning med avseende på olika parametrar. Detta gör det till det perfekta verktyget att tillämpa en optimeringsprocess på.Syftet med denna avhandling var att hitta ett mer effektivt sätt att lösa ett komplext problem och att multiplicera antalet lösningar och utvärderingar av problemet jämfört med en mer konventionell metod. Fokus var att utveckla en parametrisk modell av en armerad betongplatta utsatt för genomstansning, som kommer att kunna genomföra optimering med avseende på tid som spenderas på projektet och därmed också kostnaden för konstruktionen och miljöpåverkan.Resultatet av denna fallstudie tyder på att det finns en stor möjlighet till kostnadsbesparingar och anses därför vara ett mycket hjälpsamt verktyg för en konstruktör. Resultatet visade flera lösningar som uppfyllde de konstruktionsmässiga kraven samtidigt som de gav en lägre materialanvändning tack vare optimeringen. Många lösningar tillhandahölls och utvärderades utöver vad som kunde ha gjorts i ett projekt med en konventionell metod. En parametrisk strategi kommer att hjälpa ingenjören att optimera lösningen för en konstruktion av denna typ.

Although rice straw and other grains have been used in building since pre-history, in the past two decades, there has been a move to utilize this rapidly renewable, locally available, agricultural byproduct as part of the sustainable construction movement. Up to this point, this has been done by simply stacking up the full straw bales. Stak Block, invented by Oryzatech, Inc., is a modular, interlocking block made of a composite of rice straw and binding agent that serves as an evolution in straw construction. This study investigates the feasibility of using these Stak Blocks as a structural system. The report was divided into four main parts: material testing, development of effective construction detailing, full-scale physical shear wall testing, and a comparison with wood framed shear walls. The first section investigated the feasibility of using the Stak Blocks in a load-bearing wall application. Constitutive properties of the composite straw material such as yield strength and elastic stiffness were determined and then compared to conventional straw bale. Next, the decision was made to prestress the walls to create a more effective structural system. Various construction detailing iterations were evaluated upon the full-scale shear wall testing using a pseudo-static cyclic loading protocol. Finally, the available ductility of the prestressed Stak Block walls in a lateral force resisting application is quantified along with an approximation of potential design shear forces. It was determined that the Stak Block material performed satisfactorily in gravity and lateral force resisting applications, in some respects better than conventional wood-framed construction, and has great potential as a seismically-resistant building material.

After the 2005 M7.6 Kashmir earthquake (Pakistan), field observations reported that several buildings manufactured with traditional techniques well resisted to this strong seismic event. Nonetheless, these techniques have never been deeply studied from a structural engineering point of view yet. This thesis reports a full analytical study on the static and seismic behavior of simple one-storey buildings made with a typical construction technique commonly named as “Bhatar” system, used for several centuries and widely diffused in rather remote areas of the Himalayan regions like India, Nepal and Pakistan. The Bhatar system consists of load-bearing walls made of common dry-stacked rubble stone masonry held together by horizontal wooden bands disposed at several levels (spaced at intervals of about 60 cm). It is widely adopted in developing countries due to its advantages from both economical and constructive point of view with respect to the conventional constructions techniques (i.e. brick masonry and concrete structures). In the present work, analytical analyses are conducted with reference to a one-storey building modulus characterized by a 3.6 m x 3.6 m square plan covered by an heavy wooden roof with 20 cm thick earth coverage, in order to investigate its response under both gravity and seismic inertial loadings. In detail, in-plane and out-of-plane response of a single wall under horizontal actions is discussed and particular attention is focused on the connections between the timber elements, which are fundamental for the transmission of the horizontal actions and for preventing overturning and other failure mechanisms. The main aim is twofold: (i) to provide a first insight into the actual seismic response of such construction technique, as a basis for the specific design of ad-hoc laboratory tests on full-scale models, and (ii) to give some rules of thumb for a proper dimensioning and construction of this kind of structures.

There are a great number of old structures around the world, some of which were designed for completely different purposes than in their current application. Swedish railway bridges were for example only designed for maximum axle loads of 200 kN in the beginning of the 20th century, while the highest axle loads of today are twice as high. The traffic intensities have also increased dramatically and the velocities are now higher than ever before. Reinforced concrete trough bridges were typically designed and built in the mid-20th century and it is still one of the most frequent railway bridge types in Sweden. The trough bridges were normally designed for traffic loads which were smaller than the loads today and in order to maintain an old structure as the loads increases, structural upgrading of the load bearing capacity might be necessary. Upgrading the load carrying capacity can be performed in two ways, namely administrative upgrading or strengthening. Administrative upgrading refers to refined design calculations, using real material data, geometry and loads, which provides a higher capacity than the original design and the bridge can thereby be upgrading with minor physical impact. Upgrading by strengthening on the other hand, refers to, often, larger physical alteration of the structure in order to enhance the original load carrying capacity.Upgrading methods for increased flexural resistance of concrete trough bridges has been developed and tested previously, but strengthening methods for increased shear resistance in the bridge deck are still absent. The objective of this thesis is therefore to find an existing- or develop a new strengthening method which can be applied in order to enhance the shear resistance of concrete trough bridge decks. The difficulties associated to strengthening of existing railway bridges include traffic during the strengthening work and concrete surfaces concealed by the ballast.The State-of-the-Art indicated that none of the existing strengthening techniques were sufficient for this application and internal unbonded post-tensioning in the transverse direction was nominated as the most promising method. The research was thereafter focused on testing the possibilities and strengthening effects of post-tensioning. Two laboratory investigations were performed during the research project and the method was finally tested in a field test on a 50 years old trough bridge in Haparanda, Sweden. The strengthening procedure of internal unbonded post-tensioning consists of four consecutive steps:1.Transverse drilling of the horizontal holes through the bottom slab.2.Installation of the prestressing system.3.Post-tensioning of the system.4.Sealing of the prestressing system.The laboratory and field tests were successful and the results proved that the internal steel reinforcement within the concrete was compressed when the trough bridge was post-tensioned. Due to the compression, a higher load could be carried by the bridge deck before the tensile reinforcement yields and the bridge fails. In other words, the flexural capacity of the bridge deck was increased. The field test actually showed that eight steel bars, post-tensioned with 430 kN per bar on the Haparanda Bridge, completely counteracted the tensile stresses caused by a train with 215 kN axle loads. The effect on the shear resistance was however not as easy to measure, but the laboratory test recorded a significant strain reduction in the tensile reinforcement which was bent up at the transition zone between the bridge deck and the main girders. The reduced strain might be interpreted as lower shear stresses and post-tensioning can thereby be considered to have a positive effect on the shear resistance of the bridge deck. Shear design according to the protocol of Eurocode 2 or BBK was however found to be restrictive in predicting the post-tensionings effect on the shear capacity and further research is proposed in chapter 8.
Det finns ett stort antal gamla konstruktioner runtom i världen och många byggdes för helt andra användningsområden än vad de numera används till. Som ett exempel kan nämnas att svenska järnvägsbroar i början av 1900-talet byggdes för att klara av att bära axellaster på maximalt 200 kN, medan några av våra nybyggda broar är konstruerade för dubbelt så stora axellaster. Även traffikmängden har mångdubblats och tåghastigheterna är nu högre än någonsin. Trågbroar i armerad betong är en typisk bro som byggdes i Sverige framförallt på 50-talet och den är fortfarande en av de vanligaste brotyperna i Sverige. Trågbroarna konstruerades normalt för att bära lägre laster än vad vi har idag och för att kunna ha kvar dessa broar när lasterna ökar kan det krävas någon form av uppgradering av bärförmågan. Det finns två sätt att förbättra bärförmågan på en gammal bro, nämligen administrativ uppgradering eller förstärkning. Administrativ uppgradering innebär att nya förbättrade beräkningsmetoder används tillsammans med verkliga materialhållfastheter, geometrier och laster för att mer noggrant räkna ut brons bärförmåga. Normalt visar det sig att bärförmågan är högre än vad de ursprungliga beräkningarna antydde. På så vis höjs kapaciteten med minimal fysisk åverkan på bron. Uppgradering genom förstärkning innebär däremot att konstruktionens bärförmåga höjs genom att förändra bron ur ett rent fysiskt perspektiv. Metoder för att öka böjkapaciteten på trågbroar i betong har utvecklats och testats tidigare, men förstärkningsmetoder för att höja tvärkraftskapaciteten saknas däremot fortfarande. Målet för denna avhandling ligger därför i att utveckla en förstärkningsmetod som kan användas för att förbättra tvärkraftskapaciteten för bottenplattan på trågbroar i betong. Det finns dock några svårigheter sammankopplade med förstärkning av befintliga järnvägsbroar, t.ex. tågtraffik under förstärkningsförfarandet och att viktiga betongytor är skyddade av ballast.Inga befintliga förstärkningsmetoder bedömdes däremot som lämpliga för det avsedda användningsområdet vid ”State-of-the-Art’’ studien. Invändig efterspänning av broplattan i tvärledd bedömdes som den bäst lämpade förstärkningsmetoden och efterföljande forskning fokuserades på att reda ut möjligheter för och förstärkningseffekter av efterspänning. Två olika laboratorieförsök genomfördes under forskningsprojektet och förstärkningsmetoden testades slutligen vid ett fältförsök på en 50 år gammal järnvägsbro i Haparanda.Själva tillvägagångssättet för förstärkningsmetoden består av fyra viktigaoch sammanhängande arbetssteg:1. Borrning av horisontella hål tvärs igenom trågbrons bottenplatta.2. Installation av själva försstärkningssystemet.3. Efterspänning av förstärkningssystemet.4. Förslutning av förstärkningssystemet.Både laboratorie och fältförsöken blev lyckade och resultaten visade att stålarmeringen inuti betongen trycktes ihop när trågbron efterspänndes. Tack vare denna kompression så kan broplattan bära högre laster innan dragarmeringen börjar flyta och bron slutligen går sönder. Med andra ord så höjdes brons böjkapacitet. Fältförsöket visade att de åtta spännstagen, efterspännda med 430 kN per stag, helt och hållet motverkade dragarmeringens påkänningar av ett tåg med axellasten 215 kN. Förstärkningsmetodens effekt på tvärkraftskapaciteten är däremot inte lika lätt att påvisa men laboratorieförsöken visade att töjningen reducerades betydligt i den uppbockade dragarmeringen, i zonen där plattan fäster i huvudbalkarna. De lägre töjningsnivåerna kan tolkas som lägre skjuvpåkänningar och efterspänningen kan därmed ha en positiv effekt på broplattans tvärkraftskapacitet. Laboratorieförsöken visade däremot att både Eurokod 2 och BBK är restriktiva när det gäller att uppskatta efterspänningens effekt på tvärkraftskapaciteten. En ny förstärkningsmetod för trågbroar i betong har därmed föreslagits i och med denna avhandling, men en del frågetecken kvarstår och i kapitel 8 ges därför förslag på fortsatta forskningsområden.
Godkänd; 2013; 20130107 (jonnil); LICENTIATSEMINARIUM Ämne: Konstruktionsteknik/Structural Enginering Examinator: Professor Björn Täljsten, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Professor Mohammad Al-Emrani, Chalmers tekniska högskola, Göteborg Tid: Tisdag den 5 februari 2013 kl 13.00 Plats: F1031, Luleå tekniska universitet

Tailings dams are constructed to store waste material from mining industry and usually these dams are raised with time depending upon production rate. Tailings material is sometimes used in construction of tailings dams. Tailings are artificial material and the behavior of tailings material upon loading is different compared to natural soil materials. The mechanical properties of tailings have influence on the performance of a tailing dam. Since the tailings dams are constructed to withstand for long times, it is essential to understand tailings materials in depth in order to assure safe existence of the dams in short term as well as in long term perspective. This licentiate thesis describes the present work carried out on sulphide rich tailings from one mine in Sweden. The material presented is based upon material from three different papers. The first paper describes the basic characteristics of tailings which includes; specific gravity, phase relationships, particle size, particle shape and direct shear behavior. The second paper discusses direct shear tests carried out on tailings from one Swedish mine. Shear strength parameters are evaluated and results from 27 tests (15 drained and 12 undrained tests) are discussed. This paper also describes the vertical height reductions observed during direct shear tests. The third paper focuses on the laboratory results from triaxial tests conducted on tailings materials. This paper shows the drained behavior of tailings under application of different consolidation pressures.The results from particle analysis showed that smaller particles were very angular and bigger particles were sub angular. The material was classified as silt and silty sand. The average particle density (ρs) is 2.83t/m3. The dry density and void ratios were found to be 1.18–1.65 t/m3 and 0.72–1.41 respectively. During direct shear tests vertical height reductions were observed with slight increment in pore pressures. The strain hardening behavior was observed in both drained and undrained conditions in direct shear tests. The strength parameters determined in triaxial test were higher than of those calculated in direct shear tests. Friction angle ϕ' in triaxial tests were found to be 39 to 41degrees and it did not showed any effect with relation to depth. The cohesion and friction angle in direct shear test at 0.15radian, in drained tests were found as in range of 9.7-33.7kPa and 12.5-18.3 degrees respectively. The same parameters for undrained tests were found as 7.1-16.1 kPa and 16.0-20.4 degrees for cohesion and friction angle respectively.
Godkänd; 2014; 20140818 (riabha); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Riaz Bhanbhro Ämne: Geoteknik/Soil Mechanics and Foundation Engineering Uppsats: Mechanical Properties of Tailings Basic Description of a Tailings Material from Sweden Examinator: Professor Sven Knutsson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Adjungerande professor Peter Viklander, Vattenfall AB, Luleå Tid: Torsdag den 18 septemebr 2014 kl 10.00 Plats: F1031, Luleå tekniska universitet

Les alliages à mémoire de forme Nickel Titane sont des matériaux aux propriétés remarquablesdues à une transformation martensitique réversible et sont largement utiliséspar l'industrie biomédicale et dans des dispositifs de type actionneurs. La première partiede cette étude porte sur une analyse de leur comportement thermomécanique basée surla réalisation de mesures de champs cinématiques (par corrélation d'images visibles) etthermiques (par caméra infrarouge). Une part importante du travail présenté concernel'amélioration des calculs de sources de chaleur à partir des champs de température. Pource faire, les capacités et conductivités thermiques des phases austénitique et martensitiqueont été estimées par différentes méthodes expérimentales. Ensuite, la méthode de calcul desource a été validée sur des données virtuelles obtenues numériquement et sur des donnéesexpérimentales obtenues lors d'une transformation martensitique induite par un refroidissementnaturel. Cette première partie se conclut par l'application des développements àdes mesures réalisées lors d'un essai de cisaillement. La seconde partie est une contributionà la réalisation de matériaux architecturés constitués d'empilement de tubes de NiTi liésentre eux ; notre étude concerne la réalisation et la caractérisation de liaisons de tubes deNiTi par soudage résistif.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.
Currently, there is an increase in the demand for tall buildings in the city of Lima. This research proposes to reduce the dynamic amplification factor through the seismic design of tall buildings based on the requirements of Peruvian code considering that they are regular in plan and height. Minimum base shear values according to the comparison of static seismic shear and dynamic shear from the spectral modal analysis were reviewed for cases of buildings larger than 120 m. The study of 28 reinforced concrete buildings was proposed, with different heights - varying from 24 to 36 floors, with different floor configurations, as well as the arrangement of the walls considering as a rigid core structural system. Additionally, the characteristics of the materials, the loads and combinations were defined. The responses of these buildings were determined by the response spectrum analysis (RSA) and then compared with those obtained by the lineal response history analysis (LRHA), for the last analysis, five Peruvian seismic records were used and scaled to 0.45 g. The seismic responses of the LRHA procedure were taken as a benchmark. The result of this study is the analysis and proposal of the C/R factor for high-rise buildings, as well as obtaining the base shear and drift verification. Minimum base shear values can be reduced for high or long-term buildings, being regular in plan and height.
Revisión por pares

La Chine est actuellement confrontée à de sérieux problèmes environnementaux et est listée parmi les pays qui contribuent le plus à la pollution et à la destruction de l'environnement mondial. En particulier, la Chine du Sud est une zone naturellement sujette aux glissements de terrain à cause de conditions tectoniques, climatiques et anthropiques particulièrement défavorables. Depuis la fin des années 1990, l'Etat chinois a mis en place des politiques de reforestation de grande envergure. mais il existe des lacunes de connaissances qu'il convient de combler. En particulier, le choix des espèces les plus adaptées n'est pas aisé parce que les processus par lesquels les plantes stabilisent les pentes ont besoin d'être mieux compris.En introduction, afin de mieux préciser les périmètres qui cadrent cette thèse, sont présentées la situation de la Chine du Sud au regard des glissements de terrain, la discipline d'éco-ingénierie et les solutions qu'elle peut apporter. Ainsi, ce travail (i) se concentre sur des espèces végétales locales, (ii) se limite aux glissements de terrain superficiels, et (iii) concerne à la fois les processus mécaniques et hydriques entre le sol et les racines. A l'intérieur de ces cadres, la thèse a pour objectif de répondre à la question scientifique : quels sont les propriétés racinaires qui influencent la stabilisation des pentes ? La réflexion est ensuite appliquée aux plantes de Chine du Sud afin d'identifier les meilleures espèces-outils. Pour répondre à cette question, à la fois les données de terrain (en Chine du Sud), les expériences de laboratoire (en France) et la formulation de concepts sont mobilisées. Les résultats sont organisés en deux chapitres. Le premier pose la question de l'efficacité de la présence de racines pour stabiliser les pentes, tous d'abord sous l'angle des processus mécaniques, puis sous l'angle des processus hydriques. Le deuxième chapitre permet d'identifier un panel de traits pertinents et non redondants évaluant l'efficacité d'une espèce pour la stabilisation des pentes puis s'appuie sur ce panel afin de sélectionner les espèces chinoises les plus efficaces. Enfin, la discussion aborde les limites de ce travail et propose de nouvelles pistes de recherche.Du point de vue mécanique comme du point de vue hydrique, c'est la conjonction des effets des racines de structure et des racines fines qui importe. Les racines de structure sanas racines fines ne sont pas optimales et peuvent même faire apparaître des lignes de fragilité. Plus précisément, les racines de structure sont particulièrement bienvenues vers l'aval de la pente pour des raisons à la fois mécaniques et hydriques. Les racines fines seules ne sont pas optimales non plus, elles peuvent faire apparaître localement des zones de faiblesse qui, si elles sont proches, participeront au déclenchement d'un glissement de terrain. Des ramifications racinaires denses améliorent la stabilité mécanique. Orientées vers l'aval de la pente, elles améliorent la stabilité hydrique. Les autres traits racinaires pertinents pour évaluer l'efficacité des racines à stabiliser le sol sont la contrainte et la déformation maximale en tension, la concentration en azote et la concentration en sucres solubles.

Les matériaux architecturés attirent de plus en plus d’attentions de par leur capacité à combiner différentes propriétés ciblées. Dans ce contexte, les matériaux enchevêtrés, et plus particulièrement les matériaux monofilamentaires enchevêtrés, présentent des propriétés intéressantes en terme de légèreté, de ductilité, et de facteur de perte. En raison de l’architecture interne complexe de ces matériaux, leur caractérisation et la compréhension des mécanismes de déformation nécessitent une méthodologie adaptée. Dans cette étude, l’enchevêtrement est réalisé manuellement pour différents fils d’acier et soumis à une compression oedométrique. De manière à étudier le comportement sous charge de ce type de matériaux, un dispositif de compression uniaxiale guidée a été mis en place dans le tomographe. Il est ainsi possible de suivre, à l’aide de mesures quantitatives, la déformation de l’échantillon et l’évolution du nombre de contacts pour différentes fraction volumiques. L’utilisation de ces données microstructurales a permis un meilleure compréhension du comportement mécanique de tels enchevêtrements. Une rigidité pouvant varier de 20 à 200 MPa en fonction des paramètres de mise en forme (diamètre et forme du fil, fraction volumique, matériau constitutif) a été déterminé. Un matériau homogène de rigidité plus faible a pu être obtenu en pré-déformant le fil sous forme de ressort avant enchevêtrement. Le facteur de perte du matériau a ensuite été mesuré à la fois sous chargement statique et dynamique. L’analyse mécanique dynamique a mis en évidence la capacité de ce matériau à absorber de l’énergie avec une valeur de facteur de perte d’environ 0.25. Les propriétés mécaniques du matériau ont tout d’abord été modélisées analytiquement par un modèle de poutres et un bon accord avec les résultats expérimentaux a pu être obtenu en définissant un paramètre d’orientation equivalent, spécifique à la compression oedométrique de matériaux enchevêtrés. En parallèle, un modéle éléments discrets a été developé afin de simuler le comportement en compression de matériaux monofilamentaires enchevêtrés. Ce modèle s’appuie sur une discrétisation du fil en éléments sphériques, acquise à partir de données de tomographie. Bien que seul le comportement élastique du fil constitutif ait été pris en compte, une bonne adéquation entre résultats numériques et expérimentaux a été obtenu en ajustant les coefficients de frottement du modèle
Playing with the architecture of a material is a clever way of tailoring its properties for multi-functional applications. A lot of research have been made, in the past few years, on what is now referred to as “architectured materials” (metal foams, entangled materials, steel wool, etc), mostly for their capacity to be engineered in order to present specific properties, inherent to their architecture. In this context, some studies have been carried out concerning entangled materials but only a few on monofilament entangled materials. Such a material, with no filament ends, could exhibit interesting properties for shock absorption, vibration damping and ductility. In this study, entanglements were manually produced, using different types of wire, and submitted to constrained (inside a PTFE die) in-situ compressive tests within the laboratory tomograph. This technique enabled a 3D, non destructive, microstructural characterization of the complex architecture of these materials, along with the analysis of their macroscopic mechanical properties. The stiffness of this material was found to be in a 20-200 MPa range and homogeneous samples could be obtained, while lowering their stiffness, by pre-deforming the initial wire as a spring. Damping measurements were performed using different types of entanglements (constitutive materials, volume fraction, wire diameter, wire shape) under both monotonic and dynamic loadings and directly linked to the measurements of the number of contacts. The Dynamic Mechanical Analysis underlined the great capacity of this material to absorb energy with a loss factor of about 0.25 and damping was found to decrease with the stiffness of the entanglement. The mechanical properties of this material were first modeled using an analytical “beam” model based on the experimental evolution of the mean distance between contacts and a good agreement was found with the experimental results. In parallel, a Discrete Element Method was used in order to model the compressive behaviour of Monofilament Entangled Materials. Although purely elastic properties were taken into account in the model, a very good agreement with the experimental results was obtained by adjusting the friction coefficients of the model. This tends to prove that the plasticity of these entangled materials is rather due to the structure (friction) than to the constitutive material itself

This thesis presents three methods to estimate and locate damage in framed buildings, simply-supported beams and cantilever structures, based on experimental measurements of their fundamental vibration modes. Numerical simulations and experimental essays were performed to study the effectiveness of each method. A numerical simulation of a multi-storey framed building, a real bridge and a real chimney were carried out to study the effectiveness of the methodologies in identifying damage. The influence of measurement errors and noise in the modal data was studied in all cases. To validate the experimental effectiveness of the damage estimation methods, static and dynamics tests were performed on a framed model, a simply supported beam, and a cantilever beam in order to determine the linear behavior changes due to the increase of the level of damage. The structural identification algorithms during this thesis were based on the knowledge type of the stiffness matrix or flexibility matrix to reduce the number of modal shapes and required coordinates for the structural assessment. The methods are intended to develop tools to produce a fast response and support for future decision procedures regarding to structures widely used, by excluding experimental information, thereby allowing a cost reduction of extensive and specific testing

Similar to many self-assembling materials such as surfactants or liquid crystals, block copolymers undergo mesophase transitions due to the changes of external fields. This thesis focuses on the effects of copolymer architecture, concentration fields, and external shear flow fields on the self-assembly of block copolymers. Theories of the morphology transition of diblock copolymers at equilibrium have been studied for more than two decades. However, relatively little work has been done on more complicated architectures. The first part of this thesis uses a combination of the density functional theory (DFT) and the theory of composition fluctuations to examine the morphology transition in block copolymers of topologically distinct architectures. The morphology diagrams and corresponding properties are calculated for A-B-A triblock copolymer with given architectural parameters. The second part of this thesis focuses on the phase behavior of polymer blends consisting of amphiphilic block copolymers and selective homopolymer solvents. Phase diagrams are calculated for binary and ternary systems and the formation of induced morphologies due to the change of concentration fields are studied. The effects of architecture and sizes of constituent blocks of copolymers and the sizes of homopolymers are investigated by comparing various systems. Also, the critical Lifshitz point is examined and discussed. The third part of the thesis focuses on the order-disorder transition (ODT) and order-order transition (OOT) of block copolymers induced by an external shear flow field. The presence of shear alters the microscopic evolution of fluctuations and leads to a suppression of the fluctuation field. Consequently, the effective potential caused by excitations of monomer densities is reduced, resulting in an apparent increase of the ODT temperature. The self-consistent equation of the fluctuation spectrum is solved numerically, and the transition curve with respect to the applied shear rate is computed. This result resolves the recent controversy between experimental data and the previous perturbation analysis and shows good agreement with experimental results.