3-Phase Rectifier System with very demanding dynamic load: Architecture analysis and control strategy

A distributed power architecture for aerospace application with very restrictive specifications is analyzed. Parameters as volume, weight and losses are analyzed for the considered power architectures. In order to protect the 3 phase generator against high load steps, an intermediate bus (based in a high capacitance) to provide energy to the loads during the high load steps is included. Prototypes of the selected architecture for the rectifier and EMI filter are built and the energy control is validated.

A review of load models for the prediction of footfall-induced vibration in structures

Crowd induced dynamic loading in large structures, such as gymnasiums or stadium, is usually modelled as a series of harmonic loads which are defined in terms of their Fourier coefficients. Different values of these coefficients that were obtained from full scale measurements can be found in codes. Recently, an alternative has been proposed, based on random generation of load time histories that take into account phase lag among individuals inside the crowd. This paper presents the testing done on a structure designed to be a gymnasium. Two series of dynamic test were performed on the gym slab. For the first test an electrodynamic shaker was placed at several locations and during the second one people located inside a marked area bounced and jumped guided by different metronome rates. A finite element model (FEM) is presented and a comparison of numerically predicted and experimentally observed vibration modes and frequencies has been used to assess its validity. The second group of measurements will be compared with predictions made using the FEM model and three alternatives for crowd induced load modelling.

Evaluación del comportamiento mecánico de estructuras de hormigón armado utilizadas como elementos termoactivos

El objetivo de este trabajo es conocer las posibles modificaciones que puede producir en el comportamiento de las estructuras de hormigón armado (EHA) el hecho de que sean utilizadas como estructuras termoactivas, ya sea como intercambiadores en contacto con el terreno, o como sistema de distribución de calor utilizando la inercia térmica de los elementos de hormigón del edificio, basándose en el uso de energías renovables. Las EHA termoactivas se caracterizan por la incorporación en su interior de tubos de polietileno por los que circulan fluidos a temperaturas medias, que pueden incidir en el comportamiento mecánico de los elementos estructurales debido a dos efectos fundamentales: el incremento de temperatura que se produce en el interior de la EHA y la perturbación provocada por la incorporación de los tubos de polietileno. Con este fin, se ha realizado una campaña experimental de probetas de hormigón, estudiando los dos efectos por separado, por un lado se ha evaluado el comportamiento de probetas de hormigón tipo H-25 y tipo H-30 sometidas a cuatro temperaturas diferentes: 20ºC, 40ºC, 70ºC y 100ºC, ensayando la resistencia a compresión y la resistencia a anclaje/adherencia mediante ensayo “pull-out”; y, por otro lado, se ha evaluado el comportamiento de probetas de hormigón tipo H-25 y tipo H-30, elaboradas con dos tipos de molde (cilíndrico y cúbico), en las que se ha colocado tubos de polietileno en su interior en distintas posiciones, ensayando su resistencia a compresión. Los resultados de los ensayos han puesto de manifiesto que aunque se produce una disminución en la resistencia a compresión, y a arrancamiento, del hormigón, al ser sometido a aumentos de temperatura, esta disminución de la propiedades mecánicas es inferior al 20% al no superar esta tecnología los 70ºC; y respecto a la variación de la resistencia a compresión de probetas cilíndricas y cúbicas, debidas a la incorporación de los tubos de polietileno, se observa que si la posición de los mismos es paralela a la dirección de la carga tampoco se ven comprometidas las propiedad mecánicas del hormigón en valores superiores al 20%. ABSTRACT The aim of this project is to study the effects of using concrete structures as thermo-active constructions, either as energy foundations or other kind of thermo-active ground structures, or as a thermally activated building structure utilizing its own thermal mass conductivity and storage capacity to heat and cool buildings, based on renewable or “free” energy sources. The pipes, filled with a heat carrier fluid, that are embedded into the building´s concrete elements may bring on two different adverse effects on concrete structures. In one hand, the consequence of thermal variations and, on the other hand, because of the fact that the pipes are inside of the concrete mortar and in direct contact with the reinforcing steel bars. For this reason, different types of specimens and testing procedures have been proposed to discuss the effects of temperature (20º, 40ºC, 70ºC y 100ºC) on the performance of two different hardened concrete: H-25 and H-30, and the effects of having the pipes embedded in different positions inside of specimens made of two types of concrete, H-25 and H-30, and with two kind of cast, cylindrical and cubical. The experimental program includes the use of compressive strength test and also pull-out test, in order to investigate the interfacial adhesion quality and interfacial properties between steel bar and concrete. The results of the mechanical test showed that the increase of temperature in hardened concrete specimens lower than 70ºC, and the introduction of embedded pipes placed in parallel to the load, in cylindrical or cubic specimens, does not jeopardize the mechanical properties of concrete with strength decreases higher than 20%.

Mechanical behaviour of laminated functionally graded fibre-reinforced self-compacting cementitious composites

El hormigón autocompactante (HAC) es una nueva tipología de hormigón o material compuesto base cemento que se caracteriza por ser capaz de fluir en el interior del encofrado o molde, llenándolo de forma natural, pasando entre las barras de armadura y consolidándose únicamente bajo la acción de su peso propio, sin ayuda de medios de compactación externos, y sin que se produzca segregación de sus componentes. Debido a sus propiedades frescas (capacidad de relleno, capacidad de paso, y resistencia a la segregación), el HAC contribuye de forma significativa a mejorar la calidad de las estructuras así como a abrir nuevos campos de aplicación del hormigón. Por otra parte, la utilidad del hormigón reforzado con fibras de acero (HRFA) es hoy en día incuestionable debido a la mejora significativa de sus propiedades mecánicas tales como resistencia a tracción, tenacidad, resistencia al impacto o su capacidad para absorber energía. Comparado con el HRFA, el hormigón autocompactante reforzado con fibras de acero (HACRFA) presenta como ventaja una mayor fluidez y cohesión ofreciendo, además de unas buenas propiedades mecánicas, importantes ventajas en relación con su puesta en obra. El objetivo global de esta tesis doctoral es el desarrollo de nuevas soluciones estructurales utilizando materiales compuestos base cemento autocompactantes reforzados con fibras de acero. La tesis presenta una nueva forma de resolver el problema basándose en el concepto de los materiales gradiente funcionales (MGF) o materiales con función gradiente (MFG) con el fin de distribuir de forma eficiente las fibras en la sección estructural. Para ello, parte del HAC se sustituye por HACRFA formando capas que presentan una transición gradual entre las mismas con el fin de obtener secciones robustas y exentas de tensiones entre capas con el fin de aplicar el concepto “MGF-laminados” a elementos estructurales tales como vigas, columnas, losas, etc. El proceso incluye asimismo el propio método de fabricación que, basado en la tecnología HAC, permite el desarrollo de interfases delgadas y robustas entre capas (1-3 mm) gracias a las propiedades reológicas del material. Para alcanzar dichos objetivos se ha llevado a cabo un amplio programa experimental cuyas etapas principales son las siguientes: • Definir y desarrollar un método de diseño que permita caracterizar de forma adecuada las propiedades mecánicas de la “interfase”. Esta primera fase experimental incluye: o las consideraciones generales del propio método de fabricación basado en el concepto de fabricación de materiales gradiente funcionales denominado “reología y gravedad”, o las consideraciones específicas del método de caracterización, o la caracterización de la “interfase”. • Estudiar el comportamiento mecánico sobre elementos estructurales, utilizando distintas configuraciones de MGF-laminado frente a acciones tanto estáticas como dinámicas con el fin de comprobar la viabilidad del material para ser usado en elementos estructurales tales como vigas, placas, pilares, etc. Los resultados indican la viabilidad de la metodología de fabricación adoptada, así como, las ventajas tanto estructurales como en reducción de costes de las soluciones laminadas propuestas. Es importante destacar la mejora en términos de resistencia a flexión, compresión o impacto del hormigón autocompactante gradiente funcional en comparación con soluciones de HACRFA monolíticos inclusos con un volumen neto de fibras (Vf) doble o superior. Self-compacting concrete (SCC) is an important advance in the concrete technology in the last decades. It is a new type of high performance concrete with the ability of flowing under its own weight and without the need of vibrations. Due to its specific fresh or rheological properties, such as filling ability, passing ability and segregation resistance, SCC may contribute to a significant improvement of the quality of concrete structures and open up new field for the application of concrete. On the other hand, the usefulness of steel fibre-reinforced concrete (SFRC) in civil engineering applications is unquestionable. SFRC can improve significantly the hardened mechanical properties such as tensile strength, impact resistance, toughness and energy absorption capacity. Compared to SFRC, self-compacting steel fibre-reinforced concrete (SCSFRC) is a relatively new type of concrete with high flowability and good cohesiveness. SCSFRC offers very attractive economical and technical benefits thanks to SCC rheological properties, which can be further extended, when combined with SFRC for improving their mechanical characteristics. However, for the different concrete structural elements, a single concrete mix is selected without an attempt to adapt the diverse fibre-reinforced concretes to the stress-strain sectional properly. This thesis focused on the development of high performance cement-based structural composites made of SCC with and without steel fibres, and their applications for enhanced mechanical properties in front of different types of load and pattern configurations. It presents a new direction for tackling the mechanical problem. The approach adopted is based on the concept of functionally graded cementitious composite (FGCC) where part of the plain SCC is strategically replaced by SCSFRC in order to obtain laminated functionally graded self-compacting cementitious composites, laminated-FGSCC, in single structural elements as beams, columns, slabs, etc. The approach also involves a most suitable casting method, which uses SCC technology to eliminate the potential sharp interlayer while easily forming a robust and regular reproducible graded interlayer of 1-3 mm by controlling the rheology of the mixes and using gravity at the same time to encourage the use of the powerful concept for designing more performance suitable and cost-efficient structural systems. To reach the challenging aim, a wide experimental programme has been carried out involving two main steps: • The definition and development of a novel methodology designed for the characterization of the main parameter associated to the interface- or laminated-FGSCC solutions: the graded interlayer. Work of this first part includes: o the design considerations of the innovative (in the field of concrete) production method based on “rheology and gravity” for producing FG-SCSFRC or as named in the thesis FGSCC, casting process and elements, o the design of a specific testing methodology, o the characterization of the interface-FGSCC by using the so designed testing methodology. • The characterization of the different medium size FGSCC samples under different static and dynamic loads patterns for exploring their possibilities to be used for structural elements as beams, columns, slabs, etc. The results revealed the efficiency of the manufacturing methodology, which allow creating robust structural sections, as well as the feasibility and cost effectiveness of the proposed FGSCC solutions for different structural uses. It is noticeable to say the improvement in terms of flexural, compressive or impact loads’ responses of the different FGSCC in front of equal strength class SCSFRC bulk elements with at least the double of overall net fibre volume fraction (Vf).

On the layout of a least weight single span structure with uniform load. Some comments and improvements

Beghini et al (Struct Multidisc Optim doi:10.1007/s00158-013-1030-6, 2013) have published a very interesting paper arriving to practically the same nearly optimal solutions for the so named “bridge prob- lem” that the Writers published a year before, but using an alternative and remarkable approach to the problem. In spite of this general agreement, the Writers think that some details of the paper can be improved and there are results that can be given a clear and mean- ingful interpretation thanks to an old and practically unknown theorem on optimal slenderness.

Real-time Surveillance Application by Multiple Detectors and Compressive Trackers

A real-time surveillance system for IP network cameras is presented. Motion, part-body, and whole-body detectors are efficiently combined to generate robust and fast detections, which feed multiple compressive trackers. The generated trajectories are then improved using a reidentification strategy for long term operation.

Discrete element analysis for the assessment of the accuracy of load cell-based dynamic weighing systems in grape harvesters under different ground conditions

Dynamic weighing systems based on load cells are commonly used to estimate crop yields in the field. There is lack of data, however, regarding the accuracy of such weighing systems mounted on harvesting machinery, especially on that used to collect high value crops such as fruits and vegetables. Certainly, dynamic weighing systems mounted on the bins of grape harvesters are affected by the displacement of the load inside the bin when moving over terrain of changing topography. In this work, the load that would be registered in a grape harvester bin by a dynamic weighing system based on the use of a load cell was inferred by using the discrete element method (DEM). DEM is a numerical technique capable of accurately describing the behaviour of granular materials under dynamic situations and it has been proven to provide successful predictions in many different scenarios. In this work, different DEM models of a grape harvester bin were developed contemplating different influencing factors. Results obtained from these models were used to infer the output given by the load cell of a real bin. The mass detected by the load cell when the bin was inclined depended strongly on the distribution of the load within the bin, but was underestimated in all scenarios. The distribution of the load was found to be dependent on the inclination of the bin caused by the topography of the terrain, but also by the history of inclination (inclination rate, presence of static periods, etc.) since the effect of the inertia of the particles (i.e., representing the grapes) was not negligible. Some recommendations are given to try to improve the accuracy of crop load measurement in the field.

Induction of through-thickness compressive residual stress fields in thin Al2024-T351 plates by laser shock processing

Laser Shock Processing (LSP) has been demonstrated as an emerging technique for the induction of RS’s fields in subsurface layers of relatively thick specimens. However, the LSP treatment of relatively thin specimens brings, as an additional consequence, the possible bending in a process of laser shock forming. This effect poses a new class of problems regarding the attainment of specified RS’s depth profiles in the mentioned type of sheets, and, what can be more critical, an overall deformation of the treated component. The analysis of the problem of LSP treatment for induction of tentatively through-thickness RS’s fields for fatigue life enhancement in relatively thin sheets in a way compatible with reduced overall workpiece deformation due to spring-back self-equilibration is envisaged in this paper. The coupled theoretical-experimental predictive approach developed by the authors has been applied to the specification of LSP treatments for achievement of RS's fields tentatively able to retard crack propagation on normalized specimens. A convergence between numerical code results and experimental results coming from direct RS's measurement is presented as a first step for the treatment of the normalized specimens under optimized conditions and verification of the crack retardation properties virtually induced.

Limit load instabilities in structural elements

Este trabajo analiza distintas inestabilidades en estructuras formadas por distintos materiales. En particular, se capturan y se modelan las inestabilidades usando el método de Riks. Inicialmente, se analiza la bifurcación en depósitos cilíndricos formados por material anisótropo sometidos a carga axial y presión interna. El análisis de bifurcación y post-bifurcación asociados con cilindros de pared gruesa se formula para un material incompresible reforzado con dos fibras que son mecánicamente equivalentes y están dispuestas simétricamente. Consideramos dos casos en la naturaleza de la anisotropía: (i) Fibras refuerzo que tienen una influencia particular sobre la respuesta a cortante del material y (ii) Fibras refuerzo que influyen sólo si la fibra cambia de longitud con la deformación. Se analiza la propagación de las inestabilidades. En concreto, se diferencia en el abultamiento (bulging) entre la propagación axial y la propagación radial de la inestabilidad. Distintos modelos sufren una u otra propagación. Por último, distintas inestabilidades asociadas al mecanismo de ablandamiento del material (material softening) en contraposición al de endurecimiento (hardening) en una estructura (viga) de a: hormigón y b: hormigón reforzado son modeladas utilizando una metodología paralela a la desarrollada en el análisis de inestabilidades en tubos sometidos a presión interna. This present work deals with the instability of structures made of various materials. It captures and models different types of instabilities using numerical analysis. Firstly, we consider bifurcation for anisotropic cylindrical shells subject to axial loading and internal pressure. Analysis of bifurcation and post bifurcation of inflated hyperelastic thick-walled cylinder is formulated using a numerical procedure based on the modified Riks method for an incompressible material with two preferred directions which are mechanically equivalent and are symmetrically disposed. Secondly, bulging/necking motion in doubly fiber-reinforced incompressible nonlinearly elastic cylindrical shells is captured and we consider two cases for the nature of the anisotropy: (i) reinforcing models that have a particular influence on the shear response of the material and (ii) reinforcing models that depend only on the stretch in the fiber direction. The different instability motions are considered. Axial propagation of the bulging instability mode in thin-walled cylinders under inflation is analyzed. We present the analytical solution for this particular motion as well as for radial expansion during bulging evolution. For illustration, cylinders that are made of either isotropic incompressible non-linearly elastic materials or doubly fiber reinforced incompressible non-linearly elastic materials are considered. Finally, strain-softening constitutive models are considered to analyze two concrete structures: a reinforced concrete beam and an unreinforced notch beam. The bifurcation point is captured using the Riks method used previously to analyze bifurcation of a pressurized cylinder.

Development of a visual object tracking system using a compressive sensing framework for modeling the appearance

En el presente trabajo se aborda el problema del seguimiento de objetos, cuyo objetivo es encontrar la trayectoria de un objeto en una secuencia de video. Para ello, se ha desarrollado un método de seguimiento-por-detección que construye un modelo de apariencia en un dominio comprimido usando una nueva e innovadora técnica: “compressive sensing”. La única información necesaria es la situación del objeto a seguir en la primera imagen de la secuencia. El seguimiento de objetos es una aplicación típica del área de visión artificial con un desarrollo de bastantes años. Aun así, sigue siendo una tarea desafiante debido a varios factores: cambios de iluminación, oclusión parcial o total de los objetos y complejidad del fondo de la escena, los cuales deben ser considerados para conseguir un seguimiento robusto. Para lidiar lo más eficazmente posible con estos factores, hemos propuesto un algoritmo de tracking que entrena un clasificador Máquina Vector Soporte (“Support Vector Machine” o SVM en sus siglas en inglés) en modo online para separar los objetos del fondo de la escena. Con este fin, hemos generado nuestro modelo de apariencia por medio de un descriptor de características muy robusto que describe los objetos y el fondo devolviendo un vector de dimensiones muy altas. Por ello, se ha implementado seguidamente un paso para reducir la dimensionalidad de dichos vectores y así poder entrenar nuestro clasificador en un dominio mucho menor, al que denominamos domino comprimido. La reducción de la dimensionalidad de los vectores de características se basa en la teoría de “compressive sensing”, que dice que una señal con poca dispersión (pocos componentes distintos de cero) puede estar bien representada, e incluso puede ser reconstruida, a partir de un conjunto muy pequeño de muestras. La teoría de “compressive sensing” se ha aplicado satisfactoriamente en este trabajo y diferentes técnicas de medida y reconstrucción han sido probadas para evaluar nuestros vectores reducidos, de tal forma que se ha verificado que son capaces de preservar la información de los vectores originales. También incluimos una actualización del modelo de apariencia del objeto a seguir, mediante el reentrenamiento de nuestro clasificador en cada cuadro de la secuencia con muestras positivas y negativas, las cuales han sido obtenidas a partir de la posición predicha por el algoritmo de seguimiento en cada instante temporal. El algoritmo propuesto ha sido evaluado en distintas secuencias y comparado con otros algoritmos del estado del arte de seguimiento, para así demostrar el éxito de nuestro método.

Contribution to Load-Frequency Regulation of a Hydropower Plant with Long Tail-Race Tunnel

In this paper, a hydroelectric power plant with long tail-race tunnel has been modelled for assessing its contribution to secondary regulation reserve. Cavitation problems, caused by the discharge conduit length, are expected downstream the turbine where low pressure appears during regulation manoeuvres. Therefore, governor's gains should be selected taking into account these phenomena. On the other hand, regulation services bidden by the plant operator should fulfil TSO (Transmission System Operator) quality requirements. A methodology for tuning governor PI gains is proposed and applied to a Hydro power plant in pre-design phase in northwest area of Spain. The PI gains adjustment proposed provides a proper plant response, according to some established indexes, while avoiding cavitation phenomena.

Transversal load distribution on bridge decks

An orthotropic rectangular plate is analysed. The plate has been considered simply supported in two opposite edges and general boundary conditions along the remainder edges. Matrix formulation, very convenient for programming on a digital computer, is used through the text. This technique is applied to an actual bridge deck and the results are compared with those obtained by means of the Guyon-Massonet-Rowe method

Modelización de la respuesta de elementos estructurales lineales de vidrio plano : vigas y pilares pretensados

El vidrio se trata de un material muy apreciado en la arquitectura debido a la transparencia, característica que pocos materiales tienen. Pero, también es un material frágil, con una rotura inmediata cuando alcanza su límite elástico, sin disponer de un período plástico, que advierta de su futura rotura y permita un margen de seguridad. Por ambas razones, el vidrio se ha utilizado en arquitectura como elemento de plementería o relleno, desde tiempos antiguos, pero no como elemento estructural o portante, pese a que es un material interesante para los arquitectos para ese uso, por su característica de transparencia, ya que conseguiría la desmaterialización visual de la estructura, logrando espacios más ligeros y livianos. En cambio, si se tienen en cuenta las propiedades mecánicas del material se puede comprobar que dispone de unas características apropiadas para su uso estructural, ya que su Módulo elástico es similar al del aluminio, elemento muy utilizado en la arquitectura principalmente en las fachadas desde los últimos años, y su resistencia a compresión es muy superior incluso al hormigón armado; aunque su principal problema es su resistencia a tracción que es muy inferior a su resistencia a compresión, lo que penaliza su resistencia a flexión. En la actualidad se empieza a utilizar el vidrio como elemento portante o estructural, pero debido a su peor resistencia a flexión, se utilizan con grandes dimensiones que, a pesar de su transparencia, tienen una gran presencia. Por ello, la presente investigación pretende conseguir una reducción de las secciones de estos elementos estructurales de vidrio. Entonces, para el desarrollo de la investigación es necesario responder a una serie de preguntas fundamentales, cuyas respuestas serán el cuerpo de la investigación: 1. ¿Cuál es la finalidad de la investigación? El objetivo de esta investigación es la optimización de elementos estructurales de vidrio para su utilización en arquitectura. 2. ¿Cómo se va a realizar esa optimización? ¿Qué sistemas se van a utilizar? El sistema para realizar la optimización será la pretensión de los elementos estructurales de vidrio 3. ¿Por qué se va a utilizar la precompresión? Porque el vidrio tiene un buen comportamiento a compresión y un mal comportamiento a tracción lo que penaliza su utilización a flexión. Por medio de la precompresión se puede incrementar esta resistencia a tracción, ya que los primeros esfuerzos reducirán la compresión inicial hasta comenzar a funcionar a tracción, y por tanto aumentará su capacidad de carga. 4. ¿Con qué medios se va a comprobar y justificar ese comportamiento? Mediante simulaciones informáticas con programas de elementos finitos. 5. ¿Por qué se utilizará este método? Porque es una herramienta que arroja ventajas sobre otros métodos como los experimentales, debido a su fiabilidad, economía, rapidez y facilidad para establecer distintos casos. 6. ¿Cómo se garantiza su fiabilidad? Mediante el contraste de resultados obtenidos con ensayos físicos realizados, garantizando de ésta manera el buen comportamiento de los programas utilizados. El presente estudio tratará de responder a todas estas preguntas, para concluir y conseguir elementos estructurales de vidrio con secciones más reducidas gracias a la introducción de la precompresión, todo ello a través de las simulaciones informáticas por medio de elementos finitos. Dentro de estas simulaciones, también se realizarán comprobaciones y comparaciones entre distintas tipologías de programas para comprobar y contrastar los resultados obtenidos, intentando analizar cuál de ellos es el más idóneo para la simulación de elementos estructurales de vidrio. ABSTRACT Glass is a material very appreciated in architecture due to its transparency, feature that just a few materials share. But it is also a brittle material with an immediate breakage when it reaches its elastic limit, without having a plastic period that provides warning of future breakage allowing a safety period. For both reasons, glass has been used in architecture as infill panels, from old times. However, it has never been used as a structural or load‐bearing element, although it is an interesting material for architects for that use: because of its transparency, structural glass makes possible the visual dematerialization of the structure, achieving lighter spaces. However, taking into account the mechanical properties of the material, it is possible to check that it has appropriate conditions for structural use: its elastic modulus is similar to that of aluminium, element widely used in architecture, especially in facades from recent years; and its compressive strength is much higher than even the one of concrete. However, its main problem consists in its tensile strength that is much lower than its compressive strength, penalizing its resistance to bending. Nowadays glass is starting to be used as a bearing or structural element, but due to its worse bending strength, elements with large dimensions must be used, with a large presence despite its transparency. Therefore this research aims to get smaller sections of these structural glass elements. For the development of this thesis, it is necessary to answer a number of fundamental questions. The answers will be the core of this work: 1. What is the purpose of the investigation? The objective of this research is the optimization of structural glass elements for its use in architecture. 2. How are you going to perform this optimization? What systems will be implemented? The system for optimization is the pre‐stress of the structural elements of glass 3. Why are you going to use the pre‐compression? Because glass has a good resistance to compression and a poor tensile behaviour, which penalizes its use in bending elements. Through the pre‐compression it is possible to increase this tensile strength, due to the initial tensile efforts reducing the pre‐stress and increasing its load capacity. 4. What are the means that you will use in order to verify and justify this behaviour? The means are based on computer simulations with finite element programs (FEM) 5. Why do you use this method? Because it is a tool which gives advantages over other methods such as experimental: its reliability, economy, quick and easy to set different cases. 6. How the reliability is guaranteed? It’s guaranteed comparing the results of the simulation with the performed physical tests, ensuring the good performance of the software. This thesis will attempt to answer all these questions, to obtain glass structural elements with smaller sections thanks to the introduction of the pre‐compression, all through computer simulations using finite elements methods. In these simulations, tests and comparisons between different types of programs will also be implemented, in order to test and compare the obtained results, trying to analyse which one is the most suitable for the simulation of structural glass elements.

Bridge damage identification from moving load induced deflection based on wavelet transform and Lipschitz exponent

The wavelet transform and Lipschitz exponent perform well in detecting signal singularity.With the bridge crack damage modeled as rotational springs based on fracture mechanics, the deflection time history of the beam under the moving load is determined with a numerical method. The continuous wavelet transformation (CWT) is applied to the deflection of the beam to identify the location of the damage, and the Lipschitz exponent is used to evaluate the damage degree. The influence of different damage degrees,multiple damage, different sensor locations, load velocity and load magnitude are studied.Besides, the feasibility of this method is verified by a model experiment.

Optical sensing of the fatigue damage state of CFRP under realistic aeronautical load sequences

We present an optical sensing methodology to estimate the fatigue damage state of structures made of carbon fiber reinforced polymer (CFRP), by measuring variations on the surface roughness. Variable amplitude loads (VAL), which represent realistic loads during aeronautical missions of fighter aircraft (FALSTAFF) have been applied to coupons until failure. Stiffness degradation and surface roughness variations have been measured during the life of the coupons obtaining a Pearson correlation of 0.75 between both variables. The data were compared with a previous study for Constant Amplitude Load (CAL) obtaining similar results. Conclusions suggest that the surface roughness measured in strategic zones is a useful technique for structural health monitoring of CFRP structures, and that it is independent of the type of load applied. Surface roughness can be measured in the field by optical techniques such as speckle, confocal perfilometers and interferometry, among others.