The most used design approach for civil engineering structures is a trial and error procedure; the designer chooses an initial configuration, tests it and changes it until all safety requirements are met with good material utilization. Such a procedure is time consuming and eventually leads to a feasible solution, while several better ones could be found. Indeed, together with safety, environmental impact and investment cost should be decisive factors for the selection of structural solutions. Thus, structural optimization with respect to environmental impact and cost has been the subject of many researches in the last decades. However, design techniques based on optimization haven’t replaced the traditional design procedure yet. One of the reasons might be the constructive feasibility of the optimal solution. Moreover, concerning reinforced concrete beam bridges, to the best of the author knowledge, no study in the literature has been published dealing with the optimization of the entire bridge including both the structural configuration and cross-section dimensions. In this thesis, a two-steps automatic design and optimization procedure for reinforced concrete road beam bridges is presented. The optimization procedure finds the solution that minimizes the investment cost and the environmental impact of the bridge, while fulfilling all requirements of Eurocodes. In the first step, given the soil morphology and the two points to connect, it selects the optimal number of spans, type of piers-deck connections and piers location taking into account any obstacle the bridge has to cross. In the second and final step, it finds the optimal dimensions of the deck cross-section and produces the detailed reinforcement design. Constructability is considered and quantified within the investment cost to avoid a merely theoretical optimization. The wellknown Genetic Algorithm (GA) and Pattern Search optimization algorithms have been used. However, to reduce the computational effort and make the procedure more user-friendly, a memory system has been integrated and a modified version of GA has been developed. Moreover, the design and optimization procedure is used to study the relationship between the optimal solutions concerning investment cost and environmental impact. One case study concerning the re-design of an existing road bridge is presented. Potential savings obtained using the proposed method instead of the classic design procedure are presented. Finally, parametric studies on the total bridge length have been carried out and guidelines for designers have been produced regarding the optimal number of spans. / <p>QC 20190304</p> / Optimala betongbrolösningar med hänsyn till klimatpåverkan och investeringskostnad

Nowadays, the forestry industry still uses heavy machinery damaging both the forest and the soil. The start-up AirForestry is currently developing a sustainable way to thin and harvest trees. With their 6.2m wide electric drone carrying a harvesting tool, they can reach, thin, cut and carry trees without the need for access roads. Naturally, the drone needs to be as lightweight as possible to increase its endurance and operation range. Therefore, the first version of the drone was manufactured before the thesis with a carbon fibre laminate.  The purpose of this thesis is to study and optimize the composite structure of the drone. The first step is to characterize the existing design through experiments and simulations using the software ANSYS. Static bending loads, free vibrations, and forced vibrations are investigated against a set of predefined design requirements. This study shows that the contact surfaces between each arm and with the motor holders have high-stress concentrations compared to the rest of the arm. This means that most of the arm can be made thinner to lessen the weight with some extra reinforcement on those problematic areas.  The second step is to optimize the laminate to decrease the weight of the structure. A preliminary optimization was made and manufactured at the beginning of the thesis with strict limitations on the choice of the lamina or available thicknesses. Similar bending and vibration experiments and simulations are conducted on the new design to compare it with the older model. While the mass was expected to decrease by about 30 $\%$, the final measured weight of the arms indicates a drop of only 15 $\%$ of the mass. The model is then optimized further with more freedom in the design variables. Several variables are successively optimized: the material choice for the laminae, the thickness then of the laminae, and the angles of the plies. The mass of the structure with the final laminate has an expected decrease in mass of 45$\%$, saving more than 12kg in total / I dag använder skogsindustrin fortfarande tunga maskiner som skadar både skogen och marken. Det nystartade företaget AirForestry utvecklar för närvarande ett hållbart system för att gallra och skörda träd: en 6,2 meter breda elektriska drönare som bär ett avverkningsverktyg. Med den kan de nå, gallra, avverka och bära träd utan att behöva använda tillfartsvägar. Naturligtvis måste drönaren vara så lätt som möjligt för att öka dess uthållighet och räckvidd. Därför tillverkades den första versionen av drönaren före examensarbetet med ett kolfiberlaminat.  Syftet med detta arbete är att studera och optimera drönarens kompositstruktur. Det första steget är att karakterisera den befintliga konstruktionen genom experiment och simuleringar med hjälp av programvaran ANSYS. Statiska böjningsbelastningar, fria vibrationer och påtvingade vibrationer undersöks med avseende på en uppsättning fördefinierade konstruktionskrav. Det andra steget är att optimera laminatet för att minska strukturens vikt. En preliminär optimering gjordes och tillverkades i början av arbetet med strikta begränsningar för valet av lamina eller tillgängliga tjocklekar. Liknande böjnings- och vibrationsexperiment och simuleringar utförs på den nya konstruktionen för att jämföra den med den äldre modellen. Även om massan förväntades minska med cirka 30 $\%$, visar den slutliga uppmätta vikten på armarna att den endast minskat med 15 $\%$. Modellen optimeras sedan ytterligare med större frihet i konstruktionsvariablerna. Flera variabler optimeras successivt: materialvalet för lamellerna, lamellernas tjocklek och vinklarna på skikten. Strukturen med det slutliga laminatet får då en förväntad minskning av massan med 45 $\%$, vilket innebär en total besparing på mer än 12 kg.

No description available.

No description available.

Today's civil engineering structures are most often designed through a trial anderror approach, which means that the designer tests a design solution andevaluates whether all requirements are met. If any of the requirements are notmet, changes are made to the design until a feasible solution is obtained. It is atime-consuming process where the  nal design is not always optimal concerningmaterial consumption. In this study, a program has been developed in MATLAB®for the design of reinforced concrete retaining walls and by using optimizationalgorithms, the design process has been made automated and time-ecient. Theuse of optimization algorithms also allows for  nding a solution that is not onlyfeasible but also optimal. The developed program utilizes two objective functions,minimizing environmental impact or investment cost based on materialconsumption. In addition, the design calculations are developed according toEurocode and additional national requirements of Swedish standards.This thesis presents the background to the study, fundamental optimization theoryand how the developed program is designed. A case study is also presented whereexisting retaining walls have been examined to evaluate what savings could havebeen made using optimization algorithms in the design process. Lastly, guidelinesare also presented for designers to facilitate the choice of cross-sectional dimensionsand reinforcement bar dimensions when designing retaining walls.The results obtained in the case study show that using optimization algorithms inthe design process can make signi cant savings (10-20%) on investment cost andenvironmental impact. Moreover, the results show that an optimized retaining wallconcerning environmental impact also leads to a substantial reduction ininvestment costs and vice versa.

The reliability of a mechanical system containing electronic packages is highly affectedby the environment the system is stationed in. The difference and fluctuationsbetween the ambient temperature and the operating temperature of the electronicpackage cause accumulation of inelastic strains in the package components thusdecreasing the service life. The most common failure modes of an electronic packagehas been identified from inspection of malfunctioning machines as cracks in the solderjoint and delamination between the glue and the die. Knowledge regarding therelationships between parameters affecting these failure modes, which are importantand which are not, is of high interest when developing new and existing products. SAAB AB would like to develop a methodology using design exploration to allow forevaluation of electronic packages using nonlinear finite element methods. A surrogate model was created and parameterized with HyperMorph to be used forthree linear static variations of design of experiments, where both the performance ofthe methods themselves and the relative importance of the parameters were ofinterest. A connectivity condition was also implemented to allow for relativemovement between components while keeping the mesh intact. The designexploration was executed using a Taguchi design, a Modified extensive latticesequence design and a fractional factorial design where the three methods werecompared as well as the parameter significance analysed. An optimization was thenperformed to find the optimal parameter settings within the allowed bounds to beused where a nominal model and an optimized model are evaluated with animplemented creep law. The fatigue life of the two models were then estimated. / Tillförlitligheten hos ett mekaniskt system med elektroniska kretsar påverkas starkt av miljön systemet används i. Skillnader och fluktuationer mellan omgivningens temperatur och arbetstemperaturen för de elektroniska kretsarna orsakar ackumulering av inelastiska töjningar, därmed förkortas det mekaniska systemets livstid. Dem vanligaste fel-moderna för en elektronisk krets har identifierats genom inspektion av felande maskiner som sprickbildning i lödfogarna och delaminering mellan processorn och dess lim. Kunskap hur förhållandet mellan parametrar som påverkar dessa fel-moder, vilka som är viktiga och vilka som inte är viktiga är av högt intresse vid utveckling av nya och redan existerande produkter. SAAB AB vill utveckla en metodik som utnyttjar statistisk försöksplanering för analyserande av elektroniska kretsar med hjälp av olinjära finita element metoder för att kunna spegla dess beteende på ett realistiskt sätt. En surrogatmodell skapades och parametriserades med hjälp av HyperMorph för att användas inom tre statiskt linjära varianter av statistisk försöksplanering, där både metodens prestanda och den relativa påverkan från parametrarna var av intresse. Ett kontaktvillkor implementerades för att tillåta relativ rörelse mellan komponenter samtidigt som nätet av finita element hölls intakt. Försöksplaneringsimuleringar utfördes med en Taguchi design, en Modified extensive lattice sequence design och en fractional factorial design, där de tre metoderna jämfördes mot varandra samt analyserades vad gäller respektive parametersignifikansen. Med optimering fanns sedan en optimal modell för att kunna jämföras med en nominell modell där en kryplag implementerades i lödfogen. Livslängden beräknades sedan för båda modeller.

The most used design approach for civil engineering structures is a trial and error procedure; the designer chooses an initial configuration, tests it and changes it until all safety requirements are met with good material utilization. Such a procedure is time consuming and eventually leads to a feasible solution, while several better ones could be found. Indeed, together with safety, environmental impact and investment cost should be decisive factors for the selection of structural solutions. Thus, structural optimization with respect to environmental impact and cost has been the subject of many researches in the last decades. However, design techniques based on optimization haven’t replaced the traditional design procedure yet. One of the reasons might be the constructive feasibility of the optimal solution. Moreover, concerning reinforced concrete beam bridges, to the best of the author knowledge, no study in the literature has been published dealing with the optimization of the entire bridge including both the structural configuration and cross-section dimensions. In this thesis, a two-steps automatic design and optimization procedure for reinforced concrete road beam bridges is presented. The optimization procedure finds the solution that minimizes the investment cost and the environmental impact of the bridge, while fulfilling all requirements of Eurocodes. In the first step, given the soil morphology and the two points to connect, it selects the optimal number of spans, type of piers-deck connections and piers location taking into account any obstacle the bridge has to cross. In the second and final step, it finds the optimal dimensions of the deck cross-section and produces the detailed reinforcement design. Constructability is considered and quantified within the investment cost to avoid a merely theoretical optimization. The wellknown Genetic Algorithm (GA) and Pattern Search optimization algorithms have been used. However, to reduce the computational effort and make the procedure more user-friendly, a memory system has been integrated and a modified version of GA has been developed. Moreover, the design and optimization procedure is used to study the relationship between the optimal solutions concerning investment cost and environmental impact. One case study concerning the re-design of an existing road bridge is presented. Potential savings obtained using the proposed method instead of the classic design procedure are presented. Finally, parametric studies on the total bridge length have been carried out and guidelines for designers have been produced regarding the optimal number of spans. / <p>QC 20190304</p>

No description available.

This dissertation investigates the advantages of using curvilinear spars and ribs, termed SpaRibs, to design supersonic aircraft wing-box in comparison to the use of classic design concepts that employ straight spars and ribs. The intent is to achieve a more efficient load-bearing mechanism and to passively control aeorelastic behavior of the structure under the flight loads. The use of SpaRibs broadens the design space and allows for the natural frequencies and natural mode shape tailoring. The SpaRibs concept is implemented in a new MATLAB-based optimization framework referred to as EBF3SSWingOpt. This framework interfaces different analysis software to perform the tasks required. VisualDOC is used as optimizer; the generation of the SpaRibs geometry and of the structure Finite Element Model (FEM) is performed by MD.PATRAN; MD.NASTRAN is utilized to compute the weight of the structure, the linear static stress analysis and the linear buckling analysis required for the calculation of the response functions. EBF3SSWingOpt optimization scheme performs both the sizing and the shaping of the internal structural elements. Two methods are compared while optimizing the wing-box; a One-Step method in which sizing and topology optimization are carried out simultaneously and a Two-Step method, in which the sizing and topology optimization are carried out separately but in an iterative way. The optimization problem statements for the One-Step and the Two-Step methodologies are presented. Three methods to define the shape of the SpaRibs parametrically are described: (1) the Bounding Box and Base Curves method defines the shape of the SpaRibs based on the shape of two curves called Base Curves which are positioned into the Bounding Box, a rectangular region defined on the plane z=0 and containing the projection of the wing plan-form onto the same plane; (2) the Linked Shape method defines the shape of a set of SpaRibs in a one by one square domain of the natural space. The set of curves is subsequently transformed in the physical space for creating the wing structure geometry layout. The shape of each curve of each set is unique however, mathematical relations link their curvature in an effort to reduce the number of design variables; and (3) the Independent Shape parameterization is similar to the Linked Shape parameterization however, the shape of each curve is unique. The framework and parameterization methods described are applied to optimize different types of wing structures. Following results are presented and discussed: (1) a rectangular wing-box subjected to a chord-wise linearly varying load, optimized using SpaRibs parameterized with Bounding-Box and Base Curves method; (2) a rectangular wing-box subjected to a chord-wise linearly varying load, optimized using SpaRibs parameterized with Linked Shape method; (3) a generic fighter wing subjected to uniform distributed pressure load, optimized using SpaRibs parameterized with Bounding-Box and Base Curves method; (4) a general business jet wing subjected to pull-up maneuver loads computed using ZESt (ZONA Technology Inc. Steady Euler equations solver), optimized using SpaRibs parameterized with Independent Shape method; (5) a preliminary application of the Linked Shape parameterization to place SpaRibs into a high speed commercial transport aircraft wing-box characterized by high geometry layout complexity; and (6) an optimization of panels subjected to axial and shear loads using curvilinear stiffeners and grids of curvilinear stiffeners. The results for the optimization of the rectangular wing-box show 36.8% weight reduction from the baseline, when the Bounding Box and Base Curves parameterization is applied and the Two-Step framework is implemented. For the same structure the weight reduction amounts to 46.7% when the Linked Shape parameterization and the Two-Step framework are used. Similar results are obtained for the generic fighter wing-box structure. In this case, the weight saving is about 20%. Bounding Box and Base Curves parameterization and Two-Step framework are used. Finally, the weight reduction for the general business jet wing-box structure amounts to 17% of the baseline weight. In this case, the computation is carried out using the Independent Shape parameterization and the Two-Step framework. In general, the Two-Step optimization framework finds better optimal structure configurations as compared to the One-Step optimization framework. However, the computational time required to find to optimum with the Two-Step optimization is larger when a small number of particles are used in the particle swarm optimization method. For larger number of particles, the computational time for the two methods is comparable. Finally for very large number of particles the Two-Step optimization requires less computational time. It is also important to notice how the Two-Step framework consistently leads to a better optimum than the One-Step framework, for the same number of particles. / Ph. D.

In intelligent structures, structural deformation is generally controlled by either embedding or surface bonding the induced strain actuator to the structure. With bonded or embedded actuators used for inducing flexure, the developed in-plane force contributes indirectly through a locally-generated moment. Control authority in this configuration is thus limited by actuator offset distance. The focus of this research was to investigate a new concept in which the actuator, as opposed to being bonded, is attached to the structure at discrete points. This configuration is fundamentally different from the bonded/embedded configuration in that the actuator and the structure between the two discrete points can deform independently; and the in-plane force of the actuator, which contributes only indirectly in the case of bonded actuator, can directly influence out-of-plane displacements of the structure. Additionally, the actuator offset distance can be optimized with respect to actuator force/strain saturation for increased authority. Two implementations of this concept as applied to beam structures were investigated. In the first, the actuator (e.g., shape memory alloy actuator wire) does not possess any flexural stiffness; and therefore, remains straight between the two attachment points. In the second implementation, the actuator (PZT's and electrostrictive) possesses flexural stiffness, and bends with the structure. The formulation and experimental results for both implementations are presented. Enhanced authority is demonstrated by comparing the static response of the discretely attached actuator beam systems with their bonded counterpart systems. / Ph. D.