Experimental and numerical study of cracking of concrete due to reinforcement corrosion

La corrosión del acero es una de las patologías más importantes que afectan a las estructuras de hormigón armado que están expuestas a ambientes marinos o al ataque de sales fundentes. Cuando se produce corrosión, se genera una capa de óxido alrededor de la superficie de las armaduras, que ocupa un volumen mayor que el acero inicial; como consecuencia, el óxido ejerce presiones internas en el hormigón circundante, que lleva a la fisuración y, ocasionalmente, al desprendimiento del recubrimiento de hormigón. Durante los últimos años, numerosos estudios han contribuido a ampliar el conocimiento sobre el proceso de fisuración; sin embargo, aún existen muchas incertidumbres respecto al comportamiento mecánico de la capa de óxido, que es fundamental para predecir la fisuración. Por ello, en esta tesis se ha desarrollado y aplicado una metodología, para mejorar el conocimiento respecto al comportamiento del sistema acero-óxido-hormigón, combinando experimentos y simulaciones numéricas. Se han realizado ensayos de corrosión acelerada en condiciones de laboratorio, utilizando la técnica de corriente impresa. Con el objetivo de obtener información cercana a la capa de acero, como muestras se seleccionaron prismas de hormigón con un tubo de acero liso como armadura, que se diseñaron para conseguir la formación de una única fisura principal en el recubrimiento. Durante los ensayos, las muestras se equiparon con instrumentos especialmente diseñados para medir la variación de diámetro y volumen interior de los tubos, y se midió la apertura de la fisura principal utilizando un extensómetro comercial, adaptado a la geometría de las muestras. Las condiciones de contorno se diseñaron cuidadosamente para que los campos de corriente y deformación fuesen planos durante los ensayos, resultando en corrosión uniforme a lo largo del tubo, para poder reproducir los ensayos en simulaciones numéricas. Se ensayaron series con varias densidades de corriente y varias profundidades de corrosión. De manera complementaria, el comportamiento en fractura del hormigón se caracterizó en ensayos independientes, y se midió la pérdida gravimétrica de los tubos siguiendo procedimientos estándar. En todos los ensayos, la fisura principal creció muy despacio durante las primeras micras de profundidad de corrosión, pero después de una cierta profundidad crítica, la fisura se desarrolló completamente, con un aumento rápido de su apertura; la densidad de corriente influye en la profundidad de corrosión crítica. Las variaciones de diámetro interior y de volumen interior de los tubos mostraron tendencias diferentes entre sí, lo que indica que la deformación del tubo no fue uniforme. Después de la corrosión acelerada, las muestras se cortaron en rebanadas, que se utilizaron en ensayos post-corrosión. El patrón de fisuración se estudió a lo largo del tubo, en rebanadas que se impregnaron en vacío con resina y fluoresceína para mejorar la visibilidad de las fisuras bajo luz ultravioleta, y se estudió la presencia de óxido dentro de las grietas. En todas las muestras, se formó una fisura principal en el recubrimiento, infiltrada con óxido, y varias fisuras secundarias finas alrededor del tubo; el número de fisuras varió con la profundidad de corrosión de las muestras. Para muestras con la misma corrosión, el número de fisuras y su posición fue diferente entre muestras y entre secciones de una misma muestra, debido a la heterogeneidad del hormigón. Finalmente, se investigó la adherencia entre el acero y el hormigón, utilizando un dispositivo diseñado para empujar el tubo en el hormigón. Las curvas de tensión frente a desplazamiento del tubo presentaron un pico marcado, seguido de un descenso constante; la profundidad de corrosión y la apertura de fisura de las muestras influyeron notablemente en la tensión residual del ensayo. Para simular la fisuración del hormigón causada por la corrosión de las armaduras, se programó un modelo numérico. Éste combina elementos finitos con fisura embebida adaptable que reproducen la fractura del hormigón conforme al modelo de fisura cohesiva estándar, y elementos de interfaz llamados elementos junta expansiva, que se programaron específicamente para reproducir la expansión volumétrica del óxido y que incorporan su comportamiento mecánico. En el elemento junta expansiva se implementó un fenómeno de despegue, concretamente de deslizamiento y separación, que resultó fundamental para obtener localización de fisuras adecuada, y que se consiguió con una fuerte reducción de la rigidez tangencial y la rigidez en tracción del óxido. Con este modelo, se realizaron simulaciones de los ensayos, utilizando modelos bidimensionales de las muestras con elementos finitos. Como datos para el comportamiento en fractura del hormigón, se utilizaron las propiedades determinadas en experimentos. Para el óxido, inicialmente se supuso un comportamiento fluido, con deslizamiento y separación casi perfectos. Después, se realizó un ajuste de los parámetros del elemento junta expansiva para reproducir los resultados experimentales. Se observó que variaciones en la rigidez normal del óxido apenas afectaban a los resultados, y que los demás parámetros apenas afectaban a la apertura de fisura; sin embargo, la deformación del tubo resultó ser muy sensible a variaciones en los parámetros del óxido, debido a la flexibilidad de la pared de los tubos, lo que resultó fundamental para determinar indirectamente los valores de los parámetros constitutivos del óxido. Finalmente, se realizaron simulaciones definitivas de los ensayos. El modelo reprodujo la profundidad de corrosión crítica y el comportamiento final de las curvas experimentales; se comprobó que la variación de diámetro interior de los tubos está fuertemente influenciada por su posición relativa respecto a la fisura principal, en concordancia con los resultados experimentales. De la comparación de los resultados experimentales y numéricos, se pudo extraer información sobre las propiedades del óxido que de otra manera no habría podido obtenerse. Corrosion of steel is one of the main pathologies affecting reinforced concrete structures exposed to marine environments or to molten salt. When corrosion occurs, an oxide layer develops around the reinforcement surface, which occupies a greater volume than the initial steel; thus, it induces internal pressure on the surrounding concrete that leads to cracking and, eventually, to full-spalling of the concrete cover. During the last years much effort has been devoted to understand the process of cracking; however, there is still a lack of knowledge regarding the mechanical behavior of the oxide layer, which is essential in the prediction of cracking. Thus, a methodology has been developed and applied in this thesis to gain further understanding of the behavior of the steel-oxide-concrete system, combining experiments and numerical simulations. Accelerated corrosion tests were carried out in laboratory conditions, using the impressed current technique. To get experimental information close to the oxide layer, concrete prisms with a smooth steel tube as reinforcement were selected as specimens, which were designed to get a single main crack across the cover. During the tests, the specimens were equipped with instruments that were specially designed to measure the variation of inner diameter and volume of the tubes, and the width of the main crack was recorded using a commercial extensometer that was adapted to the geometry of the specimens. The boundary conditions were carefully designed so that plane current and strain fields were expected during the tests, resulting in nearly uniform corrosion along the length of the tube, so that the tests could be reproduced in numerical simulations. Series of tests were carried out with various current densities and corrosion depths. Complementarily, the fracture behavior of concrete was characterized in independent tests, and the gravimetric loss of the steel tubes was determined by standard means. In all the tests, the main crack grew very slowly during the first microns of corrosion depth, but after a critical corrosion depth it fully developed and opened faster; the current density influenced the critical corrosion depth. The variation of inner diameter and inner volume of the tubes had different trends, which indicates that the deformation of the tube was not uniform. After accelerated corrosion, the specimens were cut into slices, which were used in post-corrosion tests. The pattern of cracking along the reinforcement was investigated in slices that were impregnated under vacuum with resin containing fluorescein to enhance the visibility of cracks under ultraviolet lightening and a study was carried out to assess the presence of oxide into the cracks. In all the specimens, a main crack developed through the concrete cover, which was infiltrated with oxide, and several thin secondary cracks around the reinforcement; the number of cracks diminished with the corrosion depth of the specimen. For specimens with the same corrosion, the number of cracks and their position varied from one specimen to another and between cross-sections of a given specimen, due to the heterogeneity of concrete. Finally, the bond between the steel and the concrete was investigated, using a device designed to push the tubes of steel in the concrete. The curves of stress versus displacement of the tube presented a marked peak, followed by a steady descent, with notably influence of the corrosion depth and the crack width on the residual stress. To simulate cracking of concrete due to corrosion of the reinforcement, a numerical model was implemented. It combines finite elements with an embedded adaptable crack that reproduces cracking of concrete according to the basic cohesive model, and interface elements so-called expansive joint elements, which were specially designed to reproduce the volumetric expansion of oxide and incorporate its mechanical behavior. In the expansive joint element, a debonding effect was implemented consisting of sliding and separation, which was proved to be essential to achieve proper localization of cracks, and was achieved by strongly reducing the shear and the tensile stiffnesses of the oxide. With that model, simulations of the accelerated corrosion tests were carried out on 2- dimensional finite element models of the specimens. For the fracture behavior of concrete, the properties experimentally determined were used as input. For the oxide, initially a fluidlike behavior was assumed with nearly perfect sliding and separation; then the parameters of the expansive joint element were modified to fit the experimental results. Changes in the bulk modulus of the oxide barely affected the results and changes in the remaining parameters had a moderate effect on the predicted crack width; however, the deformation of the tube was very sensitive to variations in the parameters of oxide, due to the flexibility of the tube wall, which was crucial for indirect determination of the constitutive parameters of oxide. Finally, definitive simulations of the tests were carried out. The model reproduced the critical corrosion depth and the final behavior of the experimental curves; it was assessed that the variation of inner diameter of the tubes is highly influenced by its relative position with respect to the main crack, in accordance with the experimental observations. From the comparison of the experimental and numerical results, some properties of the mechanical behavior of the oxide were disclosed that otherwise could not have been measured.

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).

Proposal of a new indicator to define ductility applied to corroded steel reinforcement on concrete structures = Propuesta de un nuevo indicador para definir la ductilidad aplicada a la corrosión del acero de refuerzo en estructuras de hormigón

The carbonation of concrete or the chlorides ingress in such quantity to reach the level of bars is triggers of reinforcement corrosion. One of the most significant effects of reinforcing steel corrosion on reinforced concrete structures is the decline in the ductility-related properties of the steel. Reinforcement ductility has a decisive effect on the overall ductility of reinforced concrete structures. Different Codes classify the type of steel depending on their ductility defined by the minimum values of several parameters. Using indicators of ductility associating different properties can be advantageous on many occasions. It is considered necessary to define the ductility by means of a single parameter that considers strength values and deformation simultaneously. There are a number of criteria for defining steel ductility by a single parameter. The present experimental study addresses the variation in the ductility of concrete-embedded steel bars when exposed to accelerated corrosion. This paper analyzes the suitability of a new indicator of ductility used in corroded bars.

Caracterización geométrica y lumínica de los atrios incorporados en los edificios de Santiago de Chile

El atrio incorporado en los edificios ha sido un recurso espacial que tempranamente se difundió a nivel global, siendo adoptado por las distintas arquitecturas locales en gran parte del mundo. Su masificación estuvo favorecida primero por la rápida evolución de la tecnología del acero y el vidrio, a partir del siglo XIX, y en segundo termino por el posterior desarrollo del hormigón armado. Otro aspecto que explica tal aceptación en la arquitectura contemporánea, es de orden social y radica en la llamativa cavidad del espacio describiendo grandes dimensiones y favoreciendo con ello, el desarrollo de una multiplicidad de usos en su interior que antes eran impensados. Al interior del atrio, la luz natural es clave en las múltiples vivencias que alberga y sea tal vez la condición ambiental más valorada, ya que entrega una sensación de bienestar al conectarnos visualmente con el ambiente natural. Por esta razón de acuerdo al método hipotético deductivo, se evaluaron los efectos de la configuración geométrica, la cubierta y la orientación en el desempeño de la iluminación natural en la planta baja, a partir un modelo extraído desde el inventario de los edificios atrio construidos en Santiago de Chile, en los últimos 30 años que fue desarrollado en el capitulo 2. El análisis cuantitativo de los edificios inventariados se elaboró en el capítulo 3, considerando las dimensiones de los atrios. Simultáneamente fueron clasificados los aspectos constructivos, los materiales y las características del ambiente interior de cada edificio. En esta etapa además, fueron identificadas las variables de estudio de las proporciones geométricas de la cavidad del atrio con los coeficientes de aspecto de las proporciones, en planta (PAR), en corte (SAR) y de la cavidad según (WI), (AR) y (RI). Del análisis de todos estos parámetros se extrajo el modelo de prueba. El enfoque del estudio del capítulo 4 fue la iluminación natural, se revisaron los conceptos y el comportamiento en el atrio, a partir de un modelo físico construido a escala para registro de la iluminancia bajo cielo soleado de la ciudad. Más adelante se construyó el modelo en ambiente virtual, relacionando las variables determinadas por la geometría de la cavidad y el cerramiento superior; examinándose de esta manera distintas transparencias, proporciones de apertura, en definitiva se evaluó un progresivo cerramiento de las aberturas, verificando el ingreso de la luz y disponibilidad a nivel de piso con la finalidad, de proveer lineamientos útiles en una primera etapa del diseño arquitectónico. Para el análisis de la iluminación natural se revisaron diferentes métodos de cálculo con el propósito de evaluar los niveles de iluminancia en un plano horizontal al interior del atrio. El primero de ellos fue el Factor de Luz Día (FLD) que corresponde, a la proporción de la iluminancia en un punto de evaluación interior respecto, la cantidad proveniente del exterior bajo cielo nublado, a partir de la cual se obtuvo resultados que revelaron la alta luminosidad del cielo nublado de la ciudad. Además fueron evaluadas las recientes métricas dinámicas que dan cuenta, de la cantidad de horas en las cuales de acuerdo a los extensos registros meteorológico de la ciudad, permitieron obtener el porcentajes de horas dentro de las cuales se cumplió el estándar de iluminancia requerido, llamado autonomía lumínica (DA) o mejor aún se permanece dentro de un rango de comodidad visual en el interior del atrio referido a la iluminancia diurna útil (UDI). En el Capítulo 5 se exponen los criterios aplicados al modelo de estudio y cada una de las variantes de análisis, además se profundizó en los antecedentes y procedencia de las fuentes de los registros climáticos utilizados en las simulaciones llevadas a cabo en el programa Daysim operado por Radiance. Que permitieron evaluar el desempeño lumínico y la precisión, de cada uno de los resultados para comprobar la disponibilidad de iluminación natural a través de una matriz. En una etapa posterior se discutieron los resultados, mediante la comparación de los datos logrados según cada una de las metodologías de simulación aplicada. Finalmente se expusieron las conclusiones y futuras lineas de trabajo, las primeras respecto el dominio del atrio de cuatro caras, la incidencia del control de cerramiento de la cubierta y la relación establecida con la altura; indicando en lo específico que las mediciones de iluminancia bajo el cielo soleado de verano, permitieron aclarar, el uso de la herramienta de simulación y método basado en el clima local, que debido a su reciente desarrollo, orienta a futuras líneas de trabajo profundizando en la evaluación dinámica de la iluminancia contrastado con monitorización de casos. ABSTRACT Atriums incorporated into buildings have been a spatial resource that quickly spread throughout the globe, being adopted by several local architecture methods in several places. Their widespread increase was highly favored, in the first place, with the rapid evolution of steel and glass technologies since the nineteen century, and, in second place, by the following development of reinforced concrete. Another issue that explains this success into contemporary architecture is associated with the social approach, and it resides in the impressive cavity that describes vast dimensions, allowing the development of multiple uses in its interior that had never been considered before. Inside the atrium, daylight it is a key element in the many experiences that involves and it is possibly the most relevant environmental factor, since it radiates a feeling of well-being by uniting us visually with the natural environment. It is because of this reason that, following the hypothetical deductive method, the effects in the performance of daylight on the floor plan were evaluated considering the geometric configuration, the deck and orientation factors. This study was based in a model withdrawn from the inventory of atrium buildings that were constructed in Santiago de Chile during the past thirty years, which will be explained later in chapter 2. The quantitative analysis of the inventory of those buildings was elaborated in chapter 3, considering the dimensions of the atriums. Simultaneously, several features such as construction aspects, materials and environmental qualities were identified inside of each building. At this stage, it were identified the variables of the geometric proportions of the atrium’s cavity with the plan aspect ratio of proportions in first plan (PAR), in section (SAR) and cavity according to well index (WI), aspect ratio (AR) and room index (RI). An experimental model was obtained from the analysis of all the mentioned parameters. The main focus of the study developed in chapter 4 is daylight. The atrium’s concept and behavior were analyzed from a physical model built under scale to register the illuminances under clear, sunny sky of the city. Later on, this physical model was built in a virtual environment, connecting the variables determined by the geometry of the cavity and the superior enclosure, allowing the examination of transparencies and opening proportions. To summarize, this stage consisted on evaluating a progressive enclosure of the openings, checking the access of natural light and its availability at the atrium floor, in an effort to provide useful guidelines during the first stage of the architectural design. For the analysis of natural lighting, several calculations methods were used in order to determine the levels of illuminances in a horizontal plane inside of the atrium. The first of these methods is the Daylight Factor (DF), which consists in the proportion of light in an evaluation interior place with the amount of light coming from the outside in a cloudy day. Results determined that the cloudy sky of the city has high levels of luminosity. In addition, the recent dynamic metrics were evaluated which reflects the hours quantity. According to the meteorological records of the city’s climate, the standard of illuminance- a standard measure called Daylight Autonomy (DA) – was met. This is even better when the results stay in the line of visual convenience within the atrium, which is referred to as Useful Daylight Illuminance (UDI). In chapter 5, it was presented the criteria applied to the study model and on each of the variants of the analysis. Moreover, the information of the climate records used for the simulations - carried out in the Daysim program managed by Radiance – are detailed. These simulations allowed the observation of the daylight performance and the accuracy of each of the results to confirm the availability of natural light through a matrix. In a later stage, the results were discussed comparing the collected data in each of the methods of simulation used. Finally, conclusions and further discussion are presented. Overall, the four side atrium’s domain and the effect of the control of the cover’s enclosure. Specifically, the measurements of the daylight under summer’s clear, sunny sky allowing clarifying the use of the simulation tool and the method based on the local climate. This method allows defining new and future lines of work deepening on the dynamic of the light in contrast with the monitoring of the cases.

La arquitectura de Víctor Eusa

El arquitecto Víctor Eusa (Pamplona, 1894-1990) es la figura central de la arquitectura en Navarra durante la mayor parte del siglo XX. Desde 1920, año en que termina sus estudios en Madrid, hasta 1973, año de su jubilación, produjo centenares de obras y proyectos en esta región española, con esporádicas intervenciones en otras zonas, como las provincias vecinas de Guipúzcoa, Vizcaya y Zaragoza. Su periodo activo coincide con el de la construcción del II Ensanche de Pamplona. La cantidad y calidad de su producción hacen posible establecer una identificación entre la obra de Eusa y la ciudad entonces existente. Sus obras principales son auténticos hitos urbanos que caracterizan el Ensanche. El archivo personal del arquitecto se perdió desgraciadamente en los años setenta del pasado siglo. Este trabajo de investigación ha partido de la recopilación de la documentación gráfica existente en archivos públicos y privados, que ha dado como fruto la catalogación de las obras y proyectos de Víctor Eusa, que constituye el tomo II de la tesis. En el tomo I se analiza la trayectoria del arquitecto y la evolución formal de su lenguaje, a partir de su formación académica y las sucesivas influencias que jalonan sus primeros años de profesión: sus viajes por Europa y Oriente, Otto Wagner y la Sezession vienesa, Perret y el hormigón armado, el Art-Déco y la Exposición de París de 1925, Dudok y la arquitectura holandesa, etc. Todo ello fructifica en una arquitectura expresionista muy personal, basada en la geometría de líneas rectas y quebradas, que combina el ladrillo y el hormigón como sus materiales preferidos. Su madurez se alcanza a finales de los años veinte y se prolonga hasta la guerra civil española. En este periodo se concentran sus obras más conocidas: Casa de Misericordia, Iglesia de los Paúles, Colegio de Escolapios, edificios de viviendas en plaza Príncipe de Viana y calle García Castañón, Seminario, Casino Eslava,… Después del 36, sus responsabilidades públicas sucesivas como arquitecto municipal de Pamplona y como arquitecto provincial de la Diputación Foral de Navarra introducen en su obra una nueva dimensión urbana. ABSTRACT The architect Víctor Eusa (Pamplona, 1894-1990) was the central figure in architecture in Navarra for most of the 20th century. From 1920, when he finished his studies in Madrid, to his retirement in 1973, he was responsible for hundreds of buildings in Navarra, as well as occasional projects in the neighbouring provinces of Guipúzcoa, Vizcaya and Zaragoza. His career as an architect developed in parallel with the second phase of urban expansion in Pamplona. In terms of both quantity and quality, this new district can be seen as an embodiment of Eusa's work, and his most outstanding buildings form the landmarks which give character to this area. Unfortunately, Eusa's personal archive was lost in the 1970s. By collecting and analyzing the graphic information available in public archives, the author of this dissertation was able to compile a catalogue of Eusa's work and projects, which is provided in volume II. Volume I focuses on Eusa's career and the formal development of his language, starting from his academic training and tracing the successive influences that were at work during his early years as an architect: his journeys through Europe and the East, Otto Wagner and the Vienna Secession, Perret and reinforced concrete, Art-Déco and the Paris Exhibition of 1925, Dudok and the Dutch architecture represented in the magazines Wendingen and De Stijl, and many others. All of this came together in Eusa's highly personal expressionist style, based on a geometry of straight and zigzag lines, combining his favourite materials, brick and concrete. His mature period consolidated by end of the 1920s and lasted until the Spanish Civil War. After 1936, Eusa's responsibilities as municipal architect for Pamplona and later as head of architecture for Navarra enabled him to develop his talents in the area of urban design.

Behaviour of FRP confined concrete in square columns

A significant amount of research has been conducted on FRP-confined circular columns, but much less is known about rectangular/square columns in which the effectiveness of confinement is much reduced. This paper presents the results of experimental investigations on low strength square concrete columns confined with FRP. Axial compression tests were performed on ten intermediate size columns. The tests results indicate that FRP composites can significantly improve the bearing capacity and ductility of square section reinforced concrete columns with rounded corners. The strength enhancement ratio is greater the lower the concrete strength and also increases with the stiffness of the jacket. The confined concrete behaviour was predicted according to the more accepted theoretical models and compared with experimental results. There are two key parameters which critically influence the fitting of the models: the strain efficiency factor and the effect of confinement in non-circular sections.

A Unique Prestressed Concrete Pedestrian Bridge in Spain

This paper describes the so-called Kiss Bridge. This structure resembles a kiss, a subtle touch of structures. The beams have been structurally designed to adapt the Japanese art of paper folding called "origami." The material used for constructing the floating beams is white reinforced concrete in the form of folded shells. The two geometrically different parts have distinct structural behaviors. The length of the main pathway of both structures is over 60 m. The pedestrian bridge crosses an artificial rainwater channel with a skew of 45° with respect to the referred channel. The joint between the cantilever structure and the Y-shaped one is located over the middle of the channel. Each stretch has different transversal sections. The pedestrian bridge is made with prestressed self-compacting reinforced concrete of 60 MPa. The foundation is shallow, comprising footings and footing beams made of 25 MPa conventional concrete. The cantilever structure with its foundations is designed as a semi-integral bridge whereas the Y-shaped one is an integral structure. The dynamic behavior of the structure was carefully studied to ensure that the dynamic loads generated by pedestrians do not cause excessive vibrations, especially to the cantilever structure, which could present dynamic interactions with the pedestrians walking. The bridge was recognized, in the 2014 edition of the fib Awards for Outstanding Concrete Structures, for having made a valuable contribution to the image and promotion of concrete structures.

Refugios antiaéreos de la Guerra Civil en Alicante: intervenciones arqueológicas en las plazas de Séneca y Dr. Balmis

El golpe militar de 1936 conducirá a una dura contienda civil. Durante la misma, la Aviación Legionaria Italiana y, en menor medida, la Legión Cóndor bombardeará duramente numerosas ciudades de la costa mediterránea. Para proteger a la población, las Juntas Locales de Defensa Pasiva llevarán a cabo un programa de construcción de refugios antiaéreos sin precedentes hasta entonces. En Alicante serán numerosos los refugios construidos, entre ellos los situados en las plazas de Séneca y del Dr. Balmis, ambas construcciones salen a la luz, tras años de olvido, a raíz de sendos proyectos de remodelación de las zonas en las que se encuentran enclavados.

Construction of Structures I in Moodle: a new teaching methodology in the Degree of Building Engineer

The subject of Construction of Structures I studies, from a constructive point of view and taking into account current legislation, reinforced concrete structures used in buildings, through the acquisition of knowledge and construction criteria required in the profession of a Technical Architect. The contents acquired in this course are essential for further professional development of technicians and are closely related to many of the subjects taught in the same or other courses of the Degree in Technical Architecture at the University of Alicante. The aim of this paper is to present, analyze and discuss the development of a new methodology proposed in the mentioned subject, as it supposed an important change in the traditional way of teaching Construction and Structures I. In order to incorporate new teaching tools in 2013-2014, the course has been implemented by using a Moodle software tool to promote blended learning with online exercises. Our Moodle community allows collaborative work within an open-source platform where teachers and students share a new and personalized learning environment. Students are easily used to the interface and the platform, value the constant connection with teachers or other fellows and completely agree with the possibility of making questions or share documents 24 hours a day. The proposed methodology consists of lectures and practical classes. In the lectures, the basics of each topic are discussed; class attendance, daily study and conducting scheduled exercises are indispensable. Practical classes allow to consolidate the knowledge gained in theory classes by solving professional exercises and actual construction problems related to structures, that shall be compulsorily delivered online. So, after the correction of the teacher and the subsequent feedback of students, practical exercises ensure lifelong learning of the student, who can download any kind of material at any time (constructive details, practical exercises and even corrected exams). Regarding the general evaluation system, goals achievement is assessed on an ongoing basis (65% of the final mark) along the course through written and graphic evidences in person and online, as well as a individual development of a workbook. In all cases, the acquisition of skills, the ability to synthesize, the capacity of logical and critical thinking are assessed. The other 35 % of the mark is evaluated by a complementary graphic exam. Participation in the computing platform is essential and the student is required to do and present, at least 90% of the practices proposed. Those who do not comply with the practices in each specific date could not be assessed continuously and may only choose the final exam. In conclusion, the subject of Construction of Structures I is essential in the development of the regulated profession of Technical Architect as they are considered, among other professional profiles, as specialists in construction of building structures. The use of a new communication platform and online teaching allows the acquisition of knowledge and constructive approaches in a continuous way, with a more direct and personal monitoring by the teacher that has been highly appreciated by almost 100% of the students. Ultimately, it is important to say that the use of Moodle in this subject is a very interesting tool, which was really well welcome by students in one of the densest and important subjects of the Degree of Technical Architecture.

Corrosion evaluation of epoxy-coated, metallic-clad and solid metallic reinforcing bars in concrete /

"December 1998."

A critical literature review of high-performance corrosion reinforcements in concrete bridge applications /

"HRDI-10/07-04(1M)E"--P. [4] of cover.

Corrosion protection : concrete bridges /

"September 1998."

Time-to-corrosion of reinforcing steel in concrete slabs.

Bibliography: p. 15.

Concrete-steel construction (Der Eisenbetonbau)

Includes index.

Recommended practices for welding reinforcing steel, metal inserts and connections in reinforaced concrete construction.

"AWS D12.1- 61."