A Displacement Based Optimization (DBO) approach was applied to truss design problems with material nonlinearities, to explore feasibility and verify efficiency of the approach to solve such problem. Various truss sizing problems with holonomic (path-independent) elastoplastic laws were investigated. This type of material nonlinearity allows us to naturally extend the linear elastic truss sizing in the DBO setting to nonlinear problems. A computer program that uses the commercially available optimizer DOT by VR&D and IMSL Linear Programming solver by Visual Numerics was developed to solve this type of problems. For comparison, we chose an important class of minimum-weight truss design problems, where holonomic linear strain hardening behavior was used. Additional examples of optimum design of trusses with elastic perfectly plastic material response that could be easily solved by Limit Design approach using linear programming were investigated for comparison. All demonstrated examples were tested successfully using the DBO approach. Solutions of comparable examples were consistent with the available results by other methods. Computational effort associated with the DBO approach was minimal for all the examples studied. Optimum solutions of several examples proved that the DBO approach is particularly suited for truss topology design where removal of truss members is essential. / Master of Science

No / This paper presents a two-stage hybrid optimization algorithm based on a modified genetic algorithm. In the first stage, a global search is carried out over the design search space using a modified GA. The proposed modifications on the basic GA includes dynamically changing the population size throughout the GA process and the use of different forms of the penalty function in constraint handling. In the second stage, a local search based on the genetic algorithm solution is executed using a discretized form of Hooke and Jeeves method. The hybrid algorithm and the modifications to the basic genetic algorithm are examined on the design optimization of reinforced concrete flat slab buildings. The objective function is the total cost of the structure including the cost of concrete, formwork, reinforcement and foundation excavation. The constraints are defined according to the British Standard BS8110 for reinforced concrete structures. Comparative studies are presented to study the effect of different parameters of handling genetic algorithm on the optimized flat slab building. It has been shown that the proposed hybrid algorithm can improve genetic algorithm solutions at the expense of more function evaluations.

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.

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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>

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