Em geral, as formulações disponíveis na literatura para a análise de cascas laminadas reforçadas com fibras substituem o meio original heterogêneo por um homogêneo equivalente, que dificulta a identificação das tensões fibra-matriz, ou requerem que a malha de elementos finitos seja disposta de modo que os nós dos elementos finitos de fibra coincidam com os nós dos elementos finitos de casca, que é uma exigência bastante restritiva e que aumenta o número de graus de liberdade do sistema de equações resultante. Neste sentido, o objetivo geral desta tese consiste em desenvolver uma formulação para a inclusão de fibras longas e curtas aleatórias nas diversas lâminas de cascas laminadas anisotrópicas com não linearidade geométrica utilizando o método dos elementos finitos sem aumentar o número de graus de liberdade do sistema de equações resultante e sem a necessidade de coincidência de nós na discretização das fibras e da matriz. Nesta formulação, o elemento finito triangular de casca laminada utilizado para discretizar a matriz possui dez nós e sete graus de liberdade por nó, sendo três translações, três componentes do vetor generalizado e a taxa de variação linear da deformação ao longo da espessura. As fibras curvas, curtas aleatórias ou longas, são introduzidas, em qualquer camada do laminado, por meio de relações cinemáticas que garantem sua aderência à matriz sem a introdução de novos graus de liberdade no sistema de equações resultante. Para discretizá-las são utilizados elementos finitos unidimensionais de ordem qualquer com três graus de liberdade por nó e que consideram consistentemente a não linearidade geométrica. Todas as grandezas envolvidas são escritas em relação à configuração inicial do corpo, caracterizando a descrição Lagrangeana total ou material do movimento. Para modelar o comportamento do material adota-se a Lei Constitutiva de Saint-Venant-Kirchhoff que relaciona de forma linear o tensor de tensões de Piolla-Kirchhoff de segunda espécie e o tensor de deformações de Green-Lagrange. O equilíbrio é encontrado a partir do Princípio da Mínima Energia Potencial Total e o sistema não linear de equações resultante é resolvido utilizando-se o procedimento iterativo de Newton-Raphson. As ações externas podem ser introduzidas ao sistema de forma total ou incremental e a contribuição das fibras para a energia do sistema é adicionada na matriz global do problema. Os exemplos numéricos testados validam e demonstram as potencialidades da formulação proposta. / In general, the Finite Element (FE) formulations available in the literature for the analysis of fibre reinforced laminated shells replace the original heterogeneous medium by an equivalent homogeneous one, which makes difficult the identification of fiber-matrix stress distribution, or require that the finite element mesh is arranged in a way that the fibre finite element nodes coincide with the shell finite element ones, which is a very restrictive requirement and increases the number of degrees of freedom of the resulting system of equations. In this sense, the objective of this thesis is to develop a formulation for the inclusion of long and random short fibres in any layer of FE laminated anisotropic shells developing large displacement and rotations without increasing the number of degrees of freedom and the necessity of matching nodes in the discretization of the fibre and the matrix. In this formulation, the triangular laminated shell finite element used to discretize the matrix has ten nodes and seven degrees of freedom per node, that are, three translations, three components of a generalized vector and the linear rate of strain variation along the thickness. The curved fibres, long or random short, are introduced in any layer of the laminate shell by means of kinematic relation to ensure its adherence to the matrix without introducing new degrees of freedom in the resulting system of equations. To discretize them, any order one-dimensional finite elements with three degrees of freedom per node are used. These fibres elements are consistently considered by Geometric nonlinearity. All involved variables are written with respect to the initial configuration of the body, characterizing the Total Lagrangian description. To model the behavior of the material we use the Saint-VenantKirchhoff Constitutive Law that relates linearly the second Piolla-Kirchhoff stress tensor and Green-Lagrange strain tensor. The equilibrium is achieved from the Principle of Minimum Potential Energy and the non-linear system of equations is solved by the Newton-Raphson iterative procedure. External loads may be introduced to the system by one or various steps and the contribution of fibres to the energy of the system is added to the global matrix of the problem. The numerical examples validate and demonstrate the potential of the proposed formulation.

Cette thèse est une contribution à la résolution du problème d’optimisation sous contrainte de fiabilité. Cette méthode de dimensionnement probabiliste vise à prendre en compte les incertitudes inhérentes au système à concevoir, en vue de proposer des solutions optimales et sûres. Le niveau de sûreté est quantifié par une probabilité de défaillance. Le problème d’optimisation consiste alors à s’assurer que cette probabilité reste inférieure à un seuil fixé par les donneurs d’ordres. La résolution de ce problème nécessite un grand nombre d’appels à la fonction d’état-limite caractérisant le problème de fiabilité sous-jacent. Ainsi,cette méthodologie devient complexe à appliquer dès lors que le dimensionnement s’appuie sur un modèle numérique coûteux à évaluer (e.g. un modèle aux éléments finis). Dans ce contexte, ce manuscrit propose une stratégie basée sur la substitution adaptative de la fonction d’état-limite par un méta-modèle par Krigeage. On s’est particulièrement employé à quantifier, réduire et finalement éliminer l’erreur commise par l’utilisation de ce méta-modèle en lieu et place du modèle original. La méthodologie proposée est appliquée au dimensionnement des coques géométriquement imparfaites soumises au flambement. / This thesis is a contribution to the resolution of the reliability-based design optimization problem. This probabilistic design approach is aimed at considering the uncertainty attached to the system of interest in order to provide optimal and safe solutions. The safety level is quantified in the form of a probability of failure. Then, the optimization problem consists in ensuring that this failure probability remains less than a threshold specified by the stakeholders. The resolution of this problem requires a high number of calls to the limit-state design function underlying the reliability analysis. Hence it becomes cumbersome when the limit-state function involves an expensive-to-evaluate numerical model (e.g. a finite element model). In this context, this manuscript proposes a surrogate-based strategy where the limit-state function is progressively replaced by a Kriging meta-model. A special interest has been given to quantifying, reducing and eventually eliminating the error introduced by the use of this meta-model instead of the original model. The proposed methodology is applied to the design of geometrically imperfect shells prone to buckling.

This diploma thesis deals with problem of design and calculation of membrane structure of stadium roof. This is a complex engineering problem, which includes many partial problems: finding of initial form of membrane, statically and architecturally suitable arrangement of catenaries, economical solution of boundary conditions (foundations). All components affect each other and cannot be dealt without mutual coordination. It always greatly depends on the experience and intuition of engineer who design such structure. Task which cannot be resolved according to the theory of the first order. Equilibrium forces on the deformed structure, which in many projected structures gives satisfactory results, did not correspond to reality. It is therefore necessary to consider equilibrium of forces on the deformed structure according to the theory of large deformations. Diploma thesis was entered with regard to the intention of the companies Ing. Software Dlubal s.r.o. and FEM consulting s.r.o., working together to develop software RFEM. These companies plan to complement this program system with a module MEMBRANE for searching of initial shapes of membrane structures. This work is a contribution to the creation of this module.

The Mindlin-Reissner plate model is widely used for the elastic deformation simulation of moderately thick plates. Shear locking occurs in the case of thin plates, which means slow convergence with respect to the mesh size. The Kirchhoff plate model does not show locking effects, but is valid only for thin plates. One would like to have a method suitable for both thick and thin plates. Several approaches are known to deal with the shear locking in the Mindlin-Reissner plate model. In addition to the well-known MITC elements and other approaches based on a mixed formulation, hierarchical methods have been developed in the recent years. These are based on the Kirchhoff model and add terms to account for shear deformations. We present some of these methods and develop a new hierarchic plate formulation. This new model can be discretised by a combination of C0 and C1 finite elements. Numerical tests show that the new formulation is locking-free and numerically efficient. We also give an extension of the model to a hierarchical Naghdi shell based on a Koiter shell formulation with unknowns in Cartesian coordinates.:1 Introduction 2 Plate theory 3 Shell theory 4 Conclusion

Les structures en forme de tige sont omniprésentes dans le monde aujourd'hui. Désormais, prédire avec précision leur comportement pour l'ingénierie et les environnements virtuels est indispensable pour de nombreuses industries, notamment l'infographie, l'animation par ordinateur et la conception informatique. Dans ce mémoire, nous explorons un nouveau modèle de calcul pour les tiges élastiques qui exploite les données de simulation pour reproduire les effets de coque et de solide présents dans les tiges qui brisent les hypothèses de la théorie classique de la tige de Kirchhoff, présentant ainsi une voie d'amélioration possible pour de nombreux états de l'art techniques. Notre approche consiste à prendre un ensemble de données de simulations à partir de solides volumétriques ou de coques pour former un nouveau modèle d'énergie définie positive polynomiale d'ordre élevé pour une tige élastique. Cette nouvelle énergie élargit la gamme des comportements des matériaux qui peuvent être modélisés pour la tige, permettant ainsi de capturer une plus large gamme de phénomènes. Afin de proposer et tester ce modèle, nous concevons un pipeline expérimental pour tester les limites de la théorie linéaire des tiges et étudier les géométries d'interface entre les cas coque à tige et volume à coque pour observer les effets d'un modèle de matériau non linéaire et une section transversale non elliptique dans la déformation de la tige. Nous étudions également la relation entre la courbure de la tige et la déformation de la section transversale et la courbure pour introduire une modification sur le terme de flexion de l'énergie. Cela nous permet de reproduire à la fois le comportement de flexion asymétrique présent dans les poutres volumétriques minces et les poutres à coque avec des sections transversales non convexes. Des suggestions pour de nouvelles améliorations des modèles et des techniques expérimentales sont également données. / Rod-like structures are ubiquitous in the world today. Henceforth accurately predicting their behavior for engineering and virtual environments are indispensable for many industries including computer graphics, computer animation, and computational design. In this thesis we explore a new computational model for elastic rods that leverages simulation data to reproduce shell and solid-like effects present in rods that break the assumptions of the classical Kirchhoff rod theory, thus presenting a possible improvement avenue to many states-of-the-art techniques. Our approach consists of taking a data set of simulations from both volumetric solids or shells to train a novel high-order polynomial positive-definite energy model for an elastic rod. This new energy increases the range of material behaviors that can be modeled for the rod, thus allowing for a larger range of phenomena to be captured. In order to propose and test this model, we design an experimental pipeline to test the limits of the linear theory of rods and investigate the interface geometries between the Shell-Rod and Volume-Shell cases to observe the effects of a nonlinear material model and a non-elliptical cross-section in the rod deformation. We also investigate the relation between rod curvature and deformation of the cross-section and curvature to introduce a modification on the bending term of the energy. This allows us to reproduce both the asymmetric bending behavior present in thin volumetric solid and shell beams with non-convex cross-sections. Suggestions for further improvements in models and experimental techniques are also given.

Η Ηλεκτροεγκεφαλογραφία (ΗΕΓ) και η Μαγνητοεγκεφαλογραφία (ΜΕΓ) αποτελούν δύο από τις πλέον ευρέως χρησιμοποιούμενες μη επεμβατικές μεθόδους μελέτης της λειτουργίας του ανθρώπινου εγκεφάλου, κατά τις οποίες καταγράφονται εξωτερικά του κρανίου, το ηλεκτρικό και το μαγνητικό πεδίο, που οφείλονται στη διέργεση εγκεφαλικών νευρώνων. Oι κύριες βιοηλεκτρικές πηγές των πεδίων που καταγράφονται σ’ αυτά, είναι ομάδες νευρώνων, που προτυποποιούνται με ένα ηλεκτρικό δίπολο. Αρχικά επιλέγεται το πλέον ρεαλιστικό πρότυπο των τριών φλοιών. Δηλαδή ως αγωγός θεωρείται ολόκληρο το κρανίο, συμπεριλαμβανομένου του δέρματος, των κρανιακών οστών, του εγκεφαλονωτιαίου υγρού και του εγκεφαλικού ιστού – περιοχές διαφορετικής ηλεκτρικής αγωγιμότητας – και υπολογίζεται το ηλεκτρικό δυναμικό και το μαγνητικό πεδίο, επιλύεται δηλαδή τόσο το ευθύ πρόβλημα ΗΕΓ, όσο και το αντίστοιχο ΜΕΓ, στη σφαιρική και στην ελλειψοειδή γεωμετρία. Το δεύτερο πρότυπο αφορά στην επίλυση του ευθέος προβλήματος ΗΕΓ για την περίπτωση όπου ο εγκεφαλικός ιστός θεωρηθεί ως ένα σφαιρικός αγωγός, στο εσωτερικό του οποίου βρίσκεται είτε ομόκεντρα μια σφαιρική περιοχή υγρού, οπότε χρησιμοποιείται για την επίλυση το σφαιρικό σύστημα συντεταγμένων, είτε έκκεντρα, οπότε χρησιμοποιείται αντίστοιχα το δισφαιρικό. Τέλος, ως αγωγός θεωρείται μια ομογενής σφαίρα, περίπτωση όπου η ακριβής και πλήρης αναλυτική λύση για το πρόβλημα του Βιομαγνητισμού είναι γνωστή. Η συνεισφορά όμως της διατριβής για το πρότυπο αυτό είναι στη δημιουργία χρήσιμων εργαλείων για την μετατροπή των αναπτυγμάτων των λύσεων σε σειρές, στις αντίστοιχες κλειστές μορφές μέσω της άθροισης των σειρών, καθώς και στην εξαγωγή συμπερασμάτων σχετικά με το αντίστροφο πρόβλημα ΗΕΓ, τα οποία προκύπτουν από τη γραφική επεξεργασία της κλειστής λύσης του ηλεκτρικού δυναμικού, όπως αυτή προέκυψε από τη μέθοδο των ειδώλων. / Electroenchephalography (EEG) and Magnetoenchephalophy (MEG) are common non invansive methods for studying the function of the human brain. Considering that the data of the generated electric potential (Electroencephalogram) and the magnetic field (Magnetoenchephalogram), takes place on or in the surrounding the head, the entire head, including the skin, the bones, the cerebrospinal fluid and the cerebral, regions which are characterizing by different electric conductivity are including. For this model, the direct Bioelectromagnetism problem is solved in both spherical and ellipsoidal geometry. Specifically, the leading terms of the electric potential in the exterior of the conductor and everywhere in the interior, as well as the leading quadrupolic term of the multipole expansion of the exterior magnetic induction field in the ellipsoidal geometry, are obtained. The reduction of the the ellipsoidal results to the corresponding spherical case, which has brought up useful conclusions concerning these two geometrical models, is also presented. The direct EEG problem is described, for the case where the entire cerebral is considered as a spherical conductor, which surrounds a fluid spherical region of different conductivity. When the two spherical regions are concentric, the problem is solved with the spherical geometry, but when these are eccentric the problem is solved with the bispherical geometry. Finally, the exact and complete analytic solution for the forward EEG problem is produced by the Image Theory for the homogeneous spherical conductor and is elaborated graphically. In particular, some electric potential distributions are produced on the surface of the spherical brain, where the equipotential curves are represented by circles. Considering these distributions, a parametric analysis of the position and the orientation o the moment dipole is accomplished for the current dipole that has considered in this thesis. Consequently, when the source is near the surface, the orientation of the moment is directed vertically to the zero equipotential circle to the increase potential, since the position vector of the source tends to become vertical to the maximum equipotential curves. The existence of special position and orientation of the source, for which the contribution in the external magnetic field is zero - and for the spherical case, where the position and the orientation of the sources are parallel - corresponds to parallel equipotential curves.

There is a need for cleaner technology initiatives into the Bottom of the Pyramid (BoP) market to combat the effects of climate change. The difficulty of these initiatives lies in their business model innovation process, as those organisations struggle in finding adequate strategies to establish their business in the BoP market. The BoP market is characterised as highly uncertain, which makes the operation of businesses challenging. Hereby the thesis aims at answering the question on how organisational learning occurs in business model innovation in the BoP market. Through a case study approach, the thesis intends to understand the requirements to establish a functioning business model by analysing organisational learning under business model innovation within the BoP market. This has been realised through a three week field study in Northern Mozambique, observing the market introduction of a cleantech company operating in this context. Hereby the business model innovation process and the environment of operation was analysed. This research contributes to the current discussion of business model innovation in BoP markets by detecting organisational learning as a useful mechanism and adding relevant insights on how organisational learning occurs in this specific context. Therefore the study opens the discussion on organisational learning in business model innovation in the context of the BoP market by asking for further studies on the topic.

[ES] Las láminas de hormigón armado utilizan principalmente su forma como meca-nismo resistente. Son estructuras extremadamente eficientes y bellas. El desarrollo de este tipo de estructuras se inicia en torno a los años 20 del siglo XX alcanzando su esplendor cuantitativo y cualitativo en torno a los años 50 y 60. Su ocaso les llega en las décadas siguiente, fundamentalmente por motivos económicos. Su breve período de existencia hace que los ejemplos que tenemos de esta tipología sean muy limitados. Por cuestiones relativas a la durabilidad del hormigón armado, la protección de este singular patrimonio arquitectónico resulta necesaria y urgente, de modo especial en la Comunitat Valenciana (España) con un clima costero con cloruros agresivos para las estructuras de hormigón, especialmente para aquellas de escaso espesor y por lo tanto reducido recubrimiento del armado. El presente estudio pretende la caracterización histórica, constructiva y estructural de las estructuras laminares de hormigón armado en la Comunitat Valenciana. Para ello se ha realizado una labor previa de localización y documentación de die-cisiete estructuras para su completa catalogación. El objetivo final es la divulgación y puesta en valor, de esta tipología estructural en la Comunitat Valenciana con la esperanza de que administraciones y propietarios emprendan acciones para su conservación, rehabilitación y protección. Con su puesta en común podemos estudiar los distintos tipos de subcategorías de esta tipología, sus características comunes y diferenciadoras, el contexto histórico de su aparición, la evolución de su tecnología constructiva a lo largo de la historia, comparar los problemas que han afrontado en las fases de proyecto y ejecución o las lesiones que han sufrido a lo largo de su vida útil de cara a la prevención necesaria para una adecuada conservación. En la segunda parte de este trabajo, basada en tres artículos publicados, se estudia en detalle de la iglesia de San Nicolás del Grao de Gandía (España), de modo que sirva como primer paso para posteriores estudios en profundidad de los otros ejemplos de láminas en la Comunitat Valenciana. La iglesia de San Nicolás de Gandía (1962) es la obra póstuma del prestigioso ingeniero Eduardo Torroja Miret (1899-1961) en colaboración con el arquitecto Gonzalo Echegaray Comba y el ingeniero Jaime Nadal Aixalá. Torroja, fue pionero en el uso del hormigón pretensado, utilizándolo de modo variado e ingenioso en muchas de sus obras. Esta tecnología le permitió conseguir el estado tensional adecuado en el hormigón a la vez que garantizar su estanqueidad. Su intuición y experiencia le llevaron a asesorar en el desarrollo del método de tesado y anclaje patentado como "Método Barredo". La estructura de la iglesia de San Nicolás consiste en dos láminas plegadas de hormigón armado apoyadas en los pórticos testeros del edificio. Se trata de una solución innovadora, para salvar una luz de 29 m. El comportamiento de las láminas fue mejorado mediante una serie de costillas de rigidización y un sistema de tendones postesados que permitió minimizar los efectos de flexión esviada derivados de la sección asimétrica de dichas láminas. Los valores obtenidos de dos modelos informáticos de elementos finitos muestran una buena correspondencia con los cálculos realizados a manos por el ingeniero, reafirmando su excelente intuición estructural. Los resultados ayudan a comprender el funcionamiento de esta ingeniosa y compleja estructura. En 1996 se realizó un estudio detallado de la patología constructivas presentes en la iglesia, especialmente fisuras y desprendimiento del recubrimiento de hormigón por corrosión de las armaduras. Se describen también las lesiones presentes en el edificio y el proyecto y obras de rehabilitación que comenzaron en el año 2001 y culminaron en el año 2012, 50 aniversario de la iglesia. / [CA] Les làmines de formigó armat utilitzen principalment la seva forma com a mecanisme resistent. Són estructures extremadament eficients i belles. El desenvolupament d'aquest tipus d'estructures s'inicia al voltant dels anys 20 de segle XX aconseguint els seus any daurats quantitatius i qualitatius al voltant dels anys 50 i 60. El seu ocàs comença a la dècada següent, fonamentalment per motius econòmics. El seu breu període d'existència, és causa de que els exemples que tenim d'aquesta tipologia siguin molt limitats. Per qüestions relatives a la durabilitat del formigó armat, la protecció d'aquest singular patrimoni arquitectònic resulta necessària i urgent, de manera especial a la Comunitat Valenciana (Espanya) amb un clima de costa amb clorurs agressius per a les estructures de formigó, especialment per a aquelles d'escàs gruix i per tant reduït recobriment de l'armat. El present estudi pretén la caracterització històrica, constructiva i estructural de les estructures laminars de formigó armat a la Comunitat Valenciana. Per a això s'ha realitzat una tasca prèvia de localització i documentació de disset estructures per a la seva completa catalogació. L'objectiu final és la divulgació i posada en valor, d'aquesta tipologia estructural a la Comunitat Valenciana amb la esperança que administracions i propietaris emprenguin accions per a la seva conservació, rehabilitació i protecció. Amb la seva posada en comú podem estudiar els diferents tipus de subcategories d'aquesta tipologia, les seves característiques comunes i diferenciadores, el context històric de la seva aparició, l'evolució de la seva tecnologia constructiva al llarg de la història, comparar els problemes que han afrontat en les fases de projecte i execució o les lesions que han patit al llarg de la seva vida útil de cara a la prevenció necessària per a una adequada conservació. A la segona part d'aquest treball, basada en tres articles publicats, s'estudia en detall de l'església de Sant Nicolau del Grau de Gandia (Espanya), de manera que serveixi com a primer pas per a posteriors estudis en profunditat dels altres exemples de làmines a la Comunitat Valenciana. L'església de Sant Nicolau de Gandia (1962) és l'obra pòstuma de el prestigiós enginyer Eduardo Torroja Miret (1899-1961) en col·laboració amb l'arquitecte Gonzalo Echegaray Comba i l'enginyer Jaime Nadal Aixalá. Torroja, va ser pioner en l'ús del formigó pretesat, utilitzant-lo de manera variada i enginyosa en moltes de les seves obres. Aquesta tecnologia li va permetre aconseguir l'estat tensional adequat en el formigó a l'hora que garantir la seva estanquitat. La seva intuïció i experiència van portar a assessorar en el desenvolupament del mètode de tesat i ancoratge patentat com "Mètode Barredo". L'estructura de l'església de Sant Nicolau consisteix en dues làmines plegades de formigó armat recolzades en els pòrtics extrems de l'edifici. Es tracta d'una solució innovadora, per salvar una llum de 29 m. El comportament de les làmines és millorat mitjançant una sèrie de costelles de rigidització i un sistema de tendons posttesats que va permetre minimitzar els efectes de flexió esviada derivats de la secció asimètrica d'aquestes làmines. Els valors obtinguts de dos models informàtics d'elements finits mostren una bona correspondència amb els càlculs realitzats a mà per l'enginyer, reafirmant la seva excel·lent intuïció estructural. Els resultats ajuden a comprendre el funcionament d'aquesta enginyosa i complexa estructura. El 1996 es va realitzar un estudi detallat de les patologies constructives presents a l'església, especialment fissures i despreniment de el recobriment de formigó per corrosió de les armadures. Es descriuen també les lesions presents a l'edifici i el projecte i obres de rehabilitació que van començar l'any 2001 i van culminar en l'any 2012, 50 aniversari de l'església. / [EN] Shell concrete structures mainly use their shape as a resistant mechanism. They are extremely efficient and beautiful structures. The development of this type of structures began around the 20s of the 20th century, reaching its quantitative and qualitative golden years around the 50s and 60s. Its decline came in the following decades, mainly for economic reasons. The examples we have of this typology are very few because its short period of existence . The protection of this unique architectural heritage is necessary and urgent, especially in the Valencian Region (Spain) because durability of reinforced concrete in a coast environment with chlorides floating in the air attacking reinforced concrete structures, especially for those of fewer thickness and reduced coating of the reinforcement. The present study aims at the historical, constructive and structural characterization of the reinforced concrete shell structures in Valencian Region. At this point, a preliminary task of locating and documenting seventeen structures has been carried out for their complete cataloging. The final objective is the dissemination and enhancement of this structural typology in the Valencian Region with the hope that administrations and owners will undertake actions for its conservation, rehabilitation and protection. In the catalogue are exposed the different types of subcategories of this typology, their common and different characteristics, their birth historical context, the evolution of their construction technology throughout history, compare the problems they have faced in the design and execution phases or the injuries that they have suffered throughout their useful life with a view to the prevention necessary for proper conservation. In the second part of this work, based on three published articles, the church of San Nicolás del Grao in Gandía (Spain) is studied in detail, so that it serves as a first step for later in-depth studies of the other examples of shells in Valencian Region. The church of San Nicolás de Gandía (1962) is the last work of famous engineer Eduardo Torroja Miret (1899-1961) in collaboration with architect Gonzalo Echegaray Comba and engineer Jaime Nadal Aixalá. Torroja, was a pioneer in the use of prestressed concrete, using it in diferent and ingenious ways in many of his works. This technology allowed it to achieve the desired tension state in the concrete while its tightness is guaranteed. His intuition and experience led him to advise on the development of the patented tensioning and anchoring method "Barredo Method". San Nicolás' Curch's structure consists of two folded plates of reinforced concrete supported on the extreme concrete frames of the building. It is an innovative solution for a span of 29 m. The behavior of the plates was improved by means of a series of stiffening ribs and a post-tensioned tendon system that made it possible to minimize the effects of skewed bending produced by the asymmetric section the plates. The values obtained from two finite element computer models show a good correspondence with the calculations carried out by the engineer, reaffirming his excellent structural intuition. The results help to understand how this ingenious and complex structure works. In 1996 a detailed study of the construction pathologies present in the church was carried out. cracks and detachment of the concrete coating due to corrosion of the steel reinforcements, were specially studied. The project and rehabilitation works that began in 2001 and culminated in 2012, the 50th anniversary of the church, are also described. / Arnau Paltor, FA. (2021). Estudio y caracterización de las estructuras laminares de hormigón armado en la Comunitat Valenciana [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/174526

Different methods for the determination of cantilever properties in non-contact atomic force microscopy (NC-AFM) are under investigation. A key aspect is the determination of the cantilever stiffness being essential for a quantitative NC-AFM data analysis including the extraction of the tip-surface interaction force and potential. Furthermore, a systematic analysis of the displacement noise in the cantilever oscillation detection is performed with a special focus on the thermally excited cantilever oscillation. The propagation from displacement noise to frequency shift noise is studied under consideration of the frequency response of the PLL demodulator. The effective Q-factor of cantilevers depends on the internal damping of the cantilever as well as external influences like the ambient pressure and the quality of the cantilever fixation. While the Q-factor has a strong dependence on the ambient pressure between vacuum and ambient pressure yielding a decrease by several orders of magnitude, the pressure dependence of the resonance frequency is smaller than 1% for the same pressure range. On the other hand, the resonance frequency highly depends on the mass of the tip at the end of the cantilever making its reliable prediction from known cantilever dimensions difficult. The cantilever stiffness is determined with a high-precision static measurement method and compared to dimensional and dynamic methods. Dimensional methods suffer from the uncertainty of the measured cantilever dimensions and require a precise knowledge its material properties. A dynamic method utilising the measurement of the thermally excited cantilever displacement noise to obtain cantilever properties allows to characterise unknown cantilevers but requires an elaborative measurement equipment for spectral displacement noise analysis. Having the noise propagation in the NC-AFM system fully characterised, a proposed method allows for spring constant determination from the frequency shift noise at the output of the PLL demodulator with equipment already being available in most NC-AFM setups.