Efectos sociales y urban��sticos generados por la implantaci��n del sistema de transporte masivo ���Transbarca��� en la ciudad de Barquisimeto, Estado Lara, Venezuela

El prop��sito principal de ��ste trabajo tiene que ver con los procesos de modelado del espacio social, utilizando como campo de estudio los efectos sobre la morfolog��a urbana generados por la implantaci��n del sistema de transporte Masivo Transbarca en la ciudad venezolana de Barquisimeto. La investigaci��n se apoya en buena medida en las teor��as de la morfolog��a social elaboradas por el soci��logo E. Durkheim y desarrolladas sobre todo en el campo del urbanismo por M. Halbwachs. En ellas se vincula la morfolog��a social con su sustrato material, la forma urbana, desde una perspectiva sociol��gica. De igual manera se consideran categor��as conceptuales como fragmentaci��n y segregaci��n, seg��n otros enfoques (M. Castells y Reales). El trabajo se desarrolla seg��n una metodolog��a emp��rica, realizando an��lisis cuantitativos de los fen��menos que se consideran indicativos (el mercado de vivienda, por ejemplo) y comprobando su relaci��n con la cualificaci��n del espacio urbano donde destacan los procesos de remodelaci��n de la centralidad que resultan de la implantaci��n del Transporte Masivo. Desde esta perspectiva, la soluci��n al transporte colectivo adquiere una dimensi��n que trasciende su papel como pieza fundamental para el buen funcionamiento de la ciudad moderna en crecimiento, con independencia de que sea capaz de ofrecer una soluci��n a ese desaf��o, para convertirse en un instrumento de ordenaci��n de la ciudad que afecta a la morfolog��a social y urbana, que supone profundas alteraciones del centro urbano propiamente dicho, que implica una redistribuci��n de los grupos sociales en el espacio reformado de la ciudad: un proceso de remodelaci��n y transformaci��n del espacio funcional y social, presentado como una soluci��n a los problemas de movilidad. Tambi��n en Venezuela, como en otras partes, la evoluci��n de la morfolog��a social est�� relacionada con profundos cambios ocurridos en los sustratos f��sico-estructurales de las ciudades, que a su vez se vinculan con la din��mica de los procesos de globalizaci��n que nutren la din��mica interna de construcci��n y reconstrucci��n de esos espacios. SUMMARY The main purpose of this work deals with modeling processes of social space, using as a field of study the effects on urban morphology generated by the implementation of the transport system Transbarca Mass in the Venezuelan city of Barquisimeto. The research was based largely on theories of social morphology developed by sociologist E. Durkheim and developed primarily in the field of urban M. Halbwachs. They linked the social morphology with its substrate material, urban form, from a sociological perspective. Similarly conceptual categories are considered as fragmentation and segregation, as other approaches (M. Castells and Royals). The work is developed as an empirical methodology, performing quantitative analysis of the phenomena that are considered indicative (the housing market, for example) and checking its relation to the qualification of urban space which include remodeling processes resulting from the centrality the implementation of mass transportation. From this perspective, collective transport solution acquires a dimension that transcends its role as a cornerstone for the functioning of the modern city growing, regardless of who is able to offer a solution to this challenge, to become an instrument of City management affecting the social and urban morphology, reflecting profound alterations in the city center itself, which implies a redistribution of social groups in the city renovated space: a process of renovation and transformation of social and functional space presented as a solution to mobility problems. Also in Venezuela, as elsewhere, the development of social morphology is associated with profound changes in the physical and structural substrates of cities, which in turn are linked to the dynamics of globalization processes that nourish the internal dynamics construction and reconstruction of these areas.

Vulnerabilidad s��smica en Puerto Pr��ncipe, Hait��. Escala Macros��smica Haitiana.

Hait��, es un pa��s claramente prioritario como receptor de cooperaci��n para el desarrollo. Tras el terremoto del 12 de enero de 2010, se ha desarrollado un Proyecto de Cooperaci��n Interuniversitaria entre la Universidad del Estado de Hait�� y la Universidad Polit��cnica de Madrid, financiado por la Agencia Espa��ola de Cooperaci��n Internacional para el Desarrollo.El proyecto consiste en la formaci��n y capacitaci��n de los t��cnicos Haitianos para reconstruir su pa��s. Se est�� trabajando en la creaci��n de una escala macros��smica Haitiana, partiendo como base de la Escala Macros��smica Europea 1998. En este sentido, se hace un an��lisis exhaustivo de toda la documentaci��n t��cnica y cient��fica existente hasta la fecha sobre tipos de edificios, clases de vulnerabilidad y grados de da��os dependiendo del tipo de edificio. Como caso de estudio se aplica en la ciudad de Puerto Pr��ncipe.En primer lugar se ha clasificado el parque inmobiliario de Puerto Pr��ncipe en diferentes tipolog��as constructivas, tras un trabajo de campo y teniendo en cuenta las gu��as de auto-construcci��n y reparaci��n de edificios publicadas por el Ministerio de Obras P��blicas, Transporte y Comunicaciones de Hait��. (MTPTC).En el estudio de la vulnerabilidad, adem��s del tipo de estructura de los edificios, se tiene en cuenta la habitabilidad b��sica que debe tener todo asentamiento humano, analizando no s��lo el edificio, sino todo el entorno externo de espacios p��blicos, infraestructuras, dotaciones y servicios que, en conjunto,conforman el n��cleo de cada poblaci��n y permiten el funcionamiento eficiente del sistema de asentamientos del territorio habitado; pues, en ��ltima instancia, dicho territorio construido es el que mejor acota los riesgos ante la vulnerabilidad material y m��s garantiza la vida saludable de las personas. Los par��metros estudiados son: urban��sticos (anchos de v��as, dimensiones de manzanas, trazado, infraestructuras,...), geol��gicos (estudios del efecto local e identificaci��n de las fallas activas respecto a la edificaci��n) y topogr��ficos (implantaci��n del edificio en zonas llanas, en laderas...). En ��ltimo lugar, con todos estos datos y los da��os registrados en el terremoto de enero de 2010, se hace una escala de intensidades macros��smica y un plano de ordenaci��n de la vulnerabilidad en Puerto Pr��ncipe, que sirva de base a las autoridades haitianas para la planificaci��n urban��stica y la reconstrucci��n, mitigando de esta manera el riesgo s��mico. SUMMARY Haiti is a clear priority country as a recipient of development cooperation. After the earthquake of January 12, 2010, an Inter-University Cooperation Project has been developed between the State University of Haiti and the Polytechnic University of Madrid, funded by the Spanish Agency for International Development.The project consists of training and qualifying Haitian technicians to rebuild their country. We are currently working on the creation of a Haitian Macroseismic Scale,based on the European Macroseismic Scale 1998.For the accomplishment of this goal, a comprehensive (deep) analysis is being held, going through all the scientific and technical documentation to date, related to building types, kinds of vulnerability and degrees/ levels of damage depending on the type of building. As a case study, this has been applied to the city of Port-au-Prince.First of all, we have classified the housing typology of Port-au-Prince in different construction types, after carrying on field work in this area and keeping in mind the guidelines for self-construction and repairment of buildings published by the Ministry of Work, Transport and Communications of Haiti. (MTPTC).Regarding the study of vulnerability, besides the type of structure of the buildings, we take into account the basic habitability every human settlement should have, analyzing not only the building, but all the external environment of public spaces,infrastructures, amenities and services, which, as a whole, shape the core of each population and allow the efficient functioning of the settlement system on the inhabited territory. It is this territory,ultimately, the one that better narrows the risks when facing material vulnerability and that better ensures a healthy life for people. The studied parameters are: urban (lane width, block dimensions, layout, infrastructure...), geological (studies focusing on local effects and identification of the active faults in relation to the building) and topographical (implementation of the building on flat areas, slopes...)Finally, with all this data (information) and the registered damages related to the earthquake occurred in 2010, we create a Macroseismic Intensity Scale and a Management Plan of the vulnerability in Port-au-Prince. They will serve as a guideline for Haitians authorities in the urban planning and reconstruction, thus reducing seismic risk.

El pensamiento creativo de Fernando Higueras

Para acercarnos al pensamiento creativo de Fernando Higueras como arquitecto, partimos del estudio de sus constantes creativas en evoluci��n cronol��gica divididas en 9 direcciones de investigaci��n. En ellas observamos la importancia de su obra NO CONSTRUIDA, como germen de las constantes creativas de su pensamiento y parte de ella la estudiamos, analizamos y reconstruimos gr��ficamente en 3D. Fernando Higueras aprend��a de sus obras o propuestas arquitect��nicas anteriores llegando a la madurez constructiva y formal colmada de Belleza a trav��s de la composici��n y combinaci��n de dichas constantes con pasmosa naturalidad. Adem��s es importante a��adir, para llegar a la comprensi��n de las constantes del pensamiento creativo del arquitecto, el componente de ���intuici��n��� de todo artista, de su modo de mirar y observar las cosas como fuente de inspiraci��n. El ���modo de mirar��� del arquitecto nos habla de su sensibilidad al h��bitat popular y vern��culo del hombre. Gracias a Antonio Mir�� en el per��odo 1963-1970, Fernando Higueras pudo dar marco real a gran parte de sus ideas constructivas. El objeto de estudio del presente trabajo es llegar a las ���invariantes��� del arquitecto para comprender su pensamiento creativo. Los objetivos del presente estudio han sido conocer mejor su pensamiento, su obra desde un punto de vista cronol��gico-evolutivo para poder llegar a entender las relaciones y conexiones creativas entre unas y otras, observar y constatar la evoluci��n de sus constantes creativas y compositivas, de analizar gr��ficamente parte de su obra no construida para llegar a la mejor comprensi��n de dichas constantes reconstruy��ndolas con los medios gr��ficos digitales actuales. La reconstrucci��n en 3D de parte de su obra no construida constata la magnitud de su pensamiento creativo. La metodolog��a empleada parte de la recopilaci��n de toda la informaci��n necesaria, escritos, art��culos en revistas o peri��dicos, cr��ticas, observaciones, planos, proyectos, memorias, fotograf��as de la ��poca, maquetas, opiniones de sus contempor��neos, familiares o amigos y visita de parte de su obra construida. A partir de ah�� se fijan 9 direcciones de investigaci��n para cada constante de su pensamiento creativo. En cada direcci��n se analiza desde dos puntos de vista diferentes. Un primer punto de vista te��rico o cronol��gico-evolutivo a partir de la selecci��n de algunas de sus obras construidas y no construidas. Y otro segundo punto de vista gr��fico bas��ndose en el estudio y reconstrucci��n de parte de su obra no construida. En resultado, se ha estudiado la evoluci��n de su obra viendo las conexiones y relaciones entre unas y otras llegando a la madurez de sus constantes creativas en sus obras, algunas construidas y otras no construidas. Fernando Higueras se perfecciona as�� mismo, intentando hacer las cosas cada vez un poco mejor, llegando a dominar sus propias constantes en total madurez y expresi��n formal y constructiva. La elaboraci��n de modelos tridimensionales en 13 proyectos de su obra no construida nos refresca la capacidad de su pensamiento creativo, adem��s de analizar en parte de ellas los g��rmenes constructivos y compositivos de muchas de sus ideas o constantes creativas. Finalmente, este trabajo ha contribuido a llegar a entender a Fernando Higueras en una dimensi��n m��s amplia, desde el frescor de su obra no construida hasta la capacidad de su pensamiento creativo, de la evoluci��n de sus constantes, del estudio de sus ��ltimos proyectos no construidos, de su sensibilidad a todas las artes y a todo lo que engloba Belleza. Las 360 l��minas de dibujos que se aportan inician el estudio y an��lisis de su vasta obra no construida. ABSTRACT The analysis of Fernando Higueras's creative thought as an architect begins with a study of his main creative themes and their chronological evolution, divided into nine directions of research. Here we see the importance of his UNBUILT work as the germ of the creative themes of his thought, part of which we study, analyse and reconstruct graphically in 3-D. Fernando Higueras drew on his earlier architectural works and ideas and reached an ultimate constructive and formal maturity that was infused with beauty through composition and the amazingly natural combination of these keynote themes. In order to gain a greater understanding of the key themes of the architect's creative thought it is also worth noting the element of artists' intuition, their way of seeing and observing the world as a source of inspiration. The architect's "way of seeing" reveals his sensitivity to the popular and traditional human habitat. Thanks to Antonio Mir��, in the period between 1963 and 1970 Fernando Higueras was able to provide a real framework for a large part of his constructive ideas. The object of study of the present work is to determine the architect's ���invariables��� as a means of understanding his creative thought. The aims of the present study are to explore his thoughts in greater depth, to examine his work from the chronological-evolutionary point of view for an insight into the relationships and the creative connections between them, to observe and apprehend the evolution of his main creative themes and compositional keynotes, to analyse graphically part of his unbuilt work in order to improve our understanding of these underlying themes through their reconstruction using the latest graphic digital resources. The 3-D reconstruction of part of his unbuilt work highlights the magnitude of his creative thought. The methodology used to collect all the necessary information includes an examination of his writings and articles in journals and newspapers, criticisms, observations, plans, projects, building specifications, period photographs, models, the opinions of his contemporaries, family and friends, and visits to some of his built work. Nine directions of research were then established for each main theme of his creative thought. Each direction includes an analysis from two different points of view: the first, theoretical or chronological-evolutionary aspect, based on a selection of some of his built and unbuilt works; and a second graphic aspect based on the study and reconstruction of part of his unbuilt work. The result is a survey of the evolution of his work with a view to establishing the connections and their interrelationships, through to the ultimate maturity of his creative themes in both his built and unbuilt work. Fernando Higueras is on a constant quest for excellence, a perpetual desire to do things a little better, until a point where he gains mastery over his own recurrent themes, in the fullness of maturity and of his formal and constructive expression. The creation of three-dimensional models in 13 projects of his unbuilt work offers a new look at the capacity of his creative thought, in addition to the analysis of the evidence in some of these projects of the constructive and compositional germs of many of his ideas and themes. Finally, this work has contributed to the understanding of Fernando Higueras in a broader dimension, from the freshness of his unbuilt work through to the capacity of his creative thought, the evolution of his main themes, the study of his final unbuilt works, his sensitivity to the arts as a whole and to everything beautiful. The 360 plates of illustrations provided form the basis of the study and analysis of his extensive unbuilt work.

Identification of intermediate debonding damage in FRP-plated RC beams based on multi-objective particle swarm optimization without updated baseline model

Fiber reinforced polymer composites (FRP) have found widespread usage in the repair and strengthening of concrete structures. FRP composites exhibit high strength-to-weight ratio, corrosion resistance, and are convenient to use in repair applications. Externally bonded FRP flexural strengthening of concrete beams is the most extended application of this technique. A common cause of failure in such members is associated with intermediate crack-induced debonding (IC debonding) of the FRP substrate from the concrete in an abrupt manner. Continuous monitoring of the concrete?FRP interface is essential to pre- vent IC debonding. Objective condition assessment and performance evaluation are challenging activities since they require some type of monitoring to track the response over a period of time. In this paper, a multi-objective model updating method integrated in the context of structural health monitoring is demonstrated as promising technology for the safety and reliability of this kind of strengthening technique. The proposed method, solved by a multi-objective extension of the particle swarm optimization method, is based on strain measurements under controlled loading. The use of permanently installed fiber Bragg grating (FBG) sensors embedded into the FRP-concrete interface or bonded onto the FRP strip together with the proposed methodology results in an automated method able to operate in an unsupervised mode.

Juan Bautista L��zaro y la restauraci��n monumental: su intervenci��n en la Catedral de Le��n (1892-1909)

La catedral de Le��n, debido al estado de ruina que presentaba a mediados del siglo XIX, se vio sometida a partir de entonces a una serie de intervenciones de conservaci��n, restauraci��n y reconstrucci��n que la transforma-ron significativamente. A pesar de encontrarnos con gran cantidad de documentaci��n escrita sobre este monumento y de existir varios estudios sobre los arquitectos restauradores que intervinieron en este a finales del siglo XIX, resulta sorprendente que todav��a existan per��odos de este lapso de tiempo en el que su an��lisis y profundizaci��n haya sido menor. Este es el caso del per��odo de Juan Bautista L��zaro como arquitecto director de las obras de la catedral leonesa, existiendo ��nicamente sobre toda su obra un estudio general que fue realizado por el director de este trabajo de investigaci��n, por lo que nos llev�� a considerar que era oportuno profundizar sobre la figura y obra de uno de los arquitectos m��s importante de la restauraci��n en Espa��a de este per��odo, no solo por su obra en s��, sino tambi��n por sus pos-turas significativas respecto a la intervenci��n en el patrimonio arquitect��nico: su respeto por los a��adidos hist��ricos, su preferencia por no aislar los monumentos, sus inter��s por los sistemas constructivos y su deseo de recuperar los oficios tradicionales que estaban completamente perdidos en la Espa��a decimon��nica. El objetivo principal de la tesis es, por tanto, el an��lisis descriptivo y arquitect��nico de los proyectos e intervenciones que L��zaro desarroll�� y ejecut�� para la catedral de Santa Mar��a de Regla de Le��n, para deducir los principios e ideas que guiaron su quehacer en este templo, y poder, tras estudiar sus diversas publicaciones escritas y los proyectos e intervenciones de restauraci��n acometidas en otros edificios de car��cter monumental, llegar a establecer sus criterios de intervenci��n en el patrimonio hist��rico y art��stico. De acuerdo con esto, la tesis se estructura en tres partes: una primera parte en la que se contempla el pensamiento arquitect��nico de L��zaro en su intervenci��n en el patrimonio hist��rico; una segunda, en la que se abordan directamente los proyectos e intervenciones de L��zaro en la pulchra leonina, previa aproximaci��n del citado arquitecto al proceso de restauraci��n que se acomet��a en dicho templo; y una tercera, en la que se realiza el estudio de las principales intervenciones de restauraci��n que ejecut�� en otros edificios del patrimonio arquitect��nico espa��ol. El presente trabajo de investigaci��n se ha servido de la documentaci��n escrita, gr��fica, planim��trica y fotogr��fica que sobre los temas tratados existe desperdigada en diversos archivos dependientes de distintos organismos oficiales civiles y eclesi��sticos. Adem��s, el hecho de haber podido acceder a los trabajos de conservaci��n y restauraci��n que en estos momentos se est��n llevando a cabo en las zonas en las que intervino L��zaro (vidrieras, rejas, puertas, f��bricas, cubiertas, etc.), y el poder intercambiar opiniones y criterios con la persona que actualmente es responsable de las obras de la catedral de Le��n, ha facilitado y complementado el desarrollo de la presente tesis al haber podido contrastar y tomar datos directamente en el monumento objeto de estudio. Tambi��n se ha llevado a cabo la consulta de las distintas revistas de arquitectura publicadas en aquellos a��os y de los m��ltiples libros que versaban sobre los edificios objeto de este trabajo o que guardaban relaci��n con ellos. Asimismo hemos logrado conocer el testimonio de algunos de los herederos de L��zaro y de varios de los descendientes de los operarios que trabajaron bajo sus ��rdenes. Como conclusiones generales, la tesis define por primera vez los criterios generales que guiaron su quehacer profesional en el patrimonio. Adem��s, en este trabajo se analizan pormenorizadamente los proyectos y actuaciones de L��zaro en la catedral de Le��n, abord��ndose tambi��n en profundidad el trabajo del mencionado arquitecto en el ��mbito de la restauraci��n arquitect��nica. Para lograr este objetivo, esta tesis no se ha limitado ��nicamente a analizar la informaci��n existente en los proyectos y en los in-formes de supervisi��n de los mismos, como tradicionalmente se hab��a hecho, sino que tambi��n se ha tratado de verificar si los datos contenidos en los diferentes documentos de un mismo proyecto y en los borradores de los mismos ten��an relaci��n y coherencia entre s��. Adem��s, se ha procurado realizar el an��lisis comparativo de la realidad construida con el contenido de los proyectos, liquidaciones y documentos de la fase de ejecuci��n de las obras. Este an��lisis comparativo no hab��a sido realizado hasta la fecha, siendo este, por tanto, una de las aportaciones del trabajo. Por ��ltimo, la tesis abre tres v��as de investigaci��n futuras (que ya se han tratado y avanzado en parte, pero que escapan a los l��mites de este trabajo). Estas se refieren al estudio de la evoluci��n de la representaci��n gr��fica de los planos de la catedral leonesa catalogados en este trabajo, de la actividad p��blica de L��zaro y su preocupaci��n por la defensa del patrimonio como diputado en las Cortes, arquitecto municipal de ��vila y arquitecto diocesano de ��vila y Toledo, y de c��mo sus actuaciones de restauraci��n en el patrimonio arquitect��nico influyeron en los proyectos de obra nueva que construy��. ABSTRACT Due to the state of ruin in mid-nineteenth century, the Cathedral of Santa Maria de Regla of Le��n was subjected to a series of interventions on conservation, restoration and reconstruction that transformed it significantly. There have been several studies on the architects who took part in the restoration during the mentioned century and despite abundant documentation and research on this monument, it is surprising to note the lack of deep analysis in some of the periods. In particular, the interventions accomplished by Juan Bautista L��zaro, as chief architect of the works of the Cathedral of Le��n, have not been documented and analysed in adequate depth, despite the outstanding recognition of his work nationally and internationally. Furthermore, up to date, only the director of this research had conducted a general research of all his architectural work. For these reasons, we felt it was appropriate to elaborate on the life and work of one of the most important architects of the restoration in Spain during that period, not only for his work itself, but also for his significant contribution to the debate on architectural interventions on heritage. He is notable for his respect to historical additions, his preference for not isolating the monuments, his interest in building systems and his continuous desire to re-cover the traditional crafts that were completely lost in the nineteenth century in Spain. The main aim of this thesis is therefore the descriptive and architectural analysis of L��zaro���s projects and interventions developed and executed for the Cathedral of Le��n. The thesis identifies the principles and ideas that guided his work in this temple and establish the criteria for intervention in the historical and artistic heritage architecture he applied after studying its various print publications, projects and restoration works undertaken in other buildings. Accordingly, the thesis is structured in three parts: the first part where it deals L��zaro���s architectural thinking in his interventions on heritage constructions; the second one, in which analyses the projects and interventions carried out by Lazaro in the ���pulchra leonina���, but this analysis is preceded by the description of L��zaro���s relationship with the Cathedral of Le��n before taking charge of its restoration in 1892; and the third and final section, in which the study of major restoration interventions implemented by L��zaro in other buildings of Spanish architectural heritage is made. This research has used available documentation (in written or graphic form, plans or photographs) scattered in a diverse range of archives de-pendent on various civil and ecclesiastical institutions. Moreover, we could access the conservation and restoration works, currently being carried out in areas where L��zaro intervened (stained glass windows, forged iron en-closures, gates, doors, masonry, covers, etc.). It has been possible to ex-change views and opinions with the person currently in charge of the referred restoration works which has facilitated and complemented the development of this thesis. It further, it has allowed contrasting and obtaining data directly from the monument under study. Consultation of various architectural journals published in those years has also been taken into account, as well as a diversity of books and articles which concerned the buildings assessed in this work, or related to them. Also, although not with the results expected, it has been obtained the testimony of some of L��zaro���s descendants as well as descendants of the workers who operated under him. As a general conclusion, the thesis defines the general criteria that guided his professional work in the heritage for the first time. Furthermore, Juan Bautista L��zaro���s projects and interventions in the Cathedral of Le��n are analysed in detail. Also, it has been studying in detail the Lazaro���s work in the architectural heritage. To achieve this goal, the thesis has studied not only the information from the official projects and technical reports of them, but also it has been tried to verify if the information contained in the different documents of the same project and in the drafts were related and consistent with each other. In addition, it has been attempted to per-form a comparative analysis of the execution of L��zaro���s projects and the entire projected content. This comparative study had not been done to date and this will be, therefore, one of the main contributions of this re-search. Finally, this thesis opens up three lines of investigation (that have already been discussed and partially advanced, but which fall beyond the scope of this research). These refer to the study of the evolution of the graphical representation of the plans of Leon Cathedral catalogued in this thesis, public activity of Lazaro and his concern for the defence of heritage as deputy in Parliament, municipal architect of Avila, and as diocesan architect ��vila and Toledo, and even more how its restoration actions in architectural heritage influenced his projects of new construction.

Comportamiento de pilares de hormig��n armado confinados con materiales compuestos sometidos a compresi��n centrada

En la actualidad muchas estructuras de hormig��n armado necesitan ser reforzadas debido a diversas razones: errores en el proyecto o construcci��n, deterioro debido a efectos ambientales, cambios de uso o mayores requerimientos en los c��digos. Los materiales compuestos, tambi��n conocidos como pol��meros reforzados con fibras (FRP), est��n constituidos por fibras continuas de gran resistencia y rigidez embebidas en un material polim��rico. Los FRP se utilizan cada vez m��s en aplicaciones estructurales debido a sus excelentes propiedades (elevadas resistencia y rigidez espec��ficas y resistencia a la corrosi��n). Una de las aplicaciones m��s atractivas es el refuerzo de pilares mediante confinamiento para incrementar su resistencia y ductilidad. El confinamiento puede conseguirse pegando capas de FRP envolviendo el pilar en la direcci��n de los cercos (con las fibras orientadas en direcci��n perpendicular al eje del elemento). Se han realizado numerosos estudios experimentales en probetas cil��ndricas peque��as confinadas con encamisados de FRP y sometidas a compresi��n axial, y se han propuesto varios modelos sobre el hormig��n confinado con FRP. Es sabido que el confinamiento de pilares de secci��n no circular es menos eficiente. En una secci��n circular, el FRP ejerce una presi��n de confinamiento uniforme sobre todo el per��metro, mientras que en una secci��n rectangular la acci��n de confinamiento se concentra en las esquinas. Esta tesis presenta los resultados de una investigaci��n experimental sobre el comportamiento de probetas de hormig��n de secci��n cuadrada confinadas con FRP y sometidas a compresi��n centrada. Se realizaron un total de 42 ensayos investig��ndose el comportamiento en las direcciones axial y transversal. Las variables del estudio incluyen: la resistencia del hormig��n, el tipo de fibras (vidrio o carbono), la cuant��a de refuerzo y el radio de curvatura de las esquinas. Los resultados de los ensayos realizados muestran que el confinamiento con FRP puede mejorar considerablemente la resistencia y ductilidad de pilares de hormig��n armado de secci��n cuadrada con las esquinas redondeadas. La mejora conseguida es mayor en los hormigones de baja resistencia que en los de resistencia media. La deformaci��n de rotura de la camisa de FRP es menor que la que se obtiene en ensayos de tracci��n normalizados del laminado, y la eficiencia del confinamiento depende en gran medida del radio de redondeo de las esquinas. Los resultados se han comparado con los obtenidos seg��n los modelos te��ricos m��s aceptados. Hay dos par��metros cr��ticos en el ajuste de los modelos: el factor de eficiencia de la deformaci��n y el efecto de confinamiento en secciones no circulares. Nowadays, many existing RC structures are in need of repair and strengthening for several reasons: design or construction errors, deterioration caused by environmental effects, change in use of the structures or revisions of code requirements. Composite materials, also known as fibre reinforced polymers (FRP), are composed of high strength and stiffness continuous fibres embedded in a polymer material. FRP materials are being increasingly used in many structural applications due to their excellent properties (high strength- and stiffness-toweight ratio, good corrosion behaviour). One of the most attractive applications of FRP is the confinement of concrete columns to enhance both strength and ductility. Concrete confinement can be achieved by bonding layers of hoop FRP around the column (fibres oriented perpendicular to the longitudinal axis). Many experimental studies have been conducted on small-scale plain concrete specimens of circular cross-sections confined with FRP and subjected to pure axial compressive loading, and several design models have been proposed to describe the behaviour of FRP-confined concrete. It is widely accepted that the confinement of non-circular columns is less efficient than the confinement of circular columns. In a circular cross section, the jacket exerts a uniform confining pressure over the entire perimeter. In the case of a rectangular cross section, the confining action is mostly concentrated at the corners. This thesis presents the results of a comprehensive experimental investigation on the behaviour of axially loaded square concrete specimens confined with FRP. A total of 42 compression tests were conducted, and the behaviour of the specimens in the axial and transverse directions were investigated. The parameters considered in this study are: concrete strength, type of fibres (glass or carbon), amount of FRP reinforcement and corner radius of the cross section. The tests results indicate that FRP confinement can enhance considerably the compressive strength and ductility of RC square columns with rounded corners. The enhancement is more pronounced for low- than for normal-strength concrete. The rupture strain of the FRP jacket is lower than the ultimate strain obtained by standard tensile testing of the FRP material, and the confinement efficiency significantly depends on the corner radius. 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.

Ku is associated with the telomere in mammals

Telomeres are specialized DNA/protein complexes that comprise the ends of eukaryotic chromosomes. The highly expressed Ku heterodimer, composed of 70 and 80 Kd subunits (Ku70 and Ku80), is the high-affinity DNA binding component of the DNA-dependent protein kinase. Ku is critical for nonhomologous DNA double-stranded break repair and site-specific recombination of V(D)J gene segments. Ku also plays an important role in telomere maintenance in yeast. Herein, we report, using an in vivo crosslinking method, that human and hamster telomeric DNAs specifically coimmunoprecipitate with human Ku80 after crosslinking. Localization of Ku to the telomere does not depend on the DNA-dependent protein kinase catalytic component. These findings suggest a direct link between Ku and the telomere in mammalian cells.

Expression of an ortholog of replication protein A1 (RPA1) is induced by gibberellin in deepwater���rice

Internodes of deepwater rice are induced to grow rapidly when plants become submerged. This adaptation enables deepwater rice to keep part of its foliage above the rising flood waters during the monsoon season and to avoid drowning. This growth response is, ultimately, elicited by the plant hormone gibberellin (GA). The primary target tissue for GA action is the intercalary meristem of the internode. Using differential display of mRNA, we have isolated a number of genes whose expression in the intercalary meristem is regulated by GA. The product of one of these genes was identified as an ortholog of replication protein A1 (RPA1). RPA is a heterotrimeric protein involved in DNA replication, recombination, and repair and also in regulation of transcription. A chimeric construct, in which the single-stranded DNA-binding domain of rice RPA1 was spliced into the corresponding region of yeast RPA1, was able to complement a yeast rpa1 mutant. The transcript level of rice RPA1 is high in tissues containing dividing cells. RPA1 mRNA levels increase rapidly in the intercalary meristem during submergence and treatment with GA before the increase in the level of histone H3 mRNA, a marker for DNA replication.

DNA polymerase �� isolated from Schizosaccharomyces pombe contains five���subunits

DNA polymerase �� (pol ��) plays an essential role in DNA replication, repair, and recombination. We have purified pol �� from Schizosaccharomyces pombe more than 103-fold and demonstrated that the polymerase activity of purified S. pombe pol �� is completely dependent on proliferating cell nuclear antigen and replication factor C. SDS/PAGE analysis of the purified fraction indicated that the pol �� complex consists of five subunits that migrate with apparent molecular masses of 125, 55, 54, 42, and 22 kDa. Western blot analysis indicated that the 125, 55, and 54 kDa proteins are the large catalytic subunit (Pol3), Cdc1, and Cdc27, respectively. The identity of the other two subunits, p42 and p22, was determined following proteolytic digestion and sequence analysis of the resulting peptides. The peptide sequences derived from the p22 subunit indicated that this subunit is identical to Cdm1, previously identified as a multicopy suppressor of the temperature-sensitive cdc1-P13 mutant, whereas peptide sequences derived from the p42 subunit were identical to a previously uncharacterized ORF located on S. pombe chromosome 1.

Syncytiotrophoblastic giant cells in teratocarcinoma-like tumors derived from Parp-disrupted mouse embryonic stem cells

The enzyme poly(ADP-ribose) polymerase (Parp) catalyzes poly(ADP-ribosyl)ation reaction and is involved in DNA repair and cell death induction upon DNA damages. Meanwhile, poly(ADP-ribosyl)ation of chromosome-associated proteins is suggested to be implicated in the regulation of gene expression and cellular differentiation, both of which are important in tumorigenesis. To investigate directly the role of Parp deficiency in tumorigenicity and differentiation of embryonic stem (ES) cells during tumor formation, studies were conducted by using wild-type J1 (Parp+/+) ES cells and Parp+/��� and Parp���/��� ES clones generated by disrupting Parp exon 1. These ES cells, irrespective of the Parp genotype, produced tumors phenotypically similar to teratocarcinoma when injected s.c. into nude mice. Remarkably, all tumors derived from Parp���/��� clones contained syncytiotrophoblastic giant cells (STGCs), which possess single or multiple megalo-nuclei. The STGCs were present within large areas of intratumoral hemorrhage. In contrast, neither STGC nor hemorrhage was observed in tumors of both wild-type J1 cells and Parp+/��� clones. Electron microscopic examination showed that the STGCs possess microvilli on the cell surface and contained secretory granules in the cytoplasm. Furthermore, the cytoplasms of STGCs were strongly stained with antibody against mouse prolactin, which could similarly stain trophoblasts in placenta. These morphological and histochemical features indicate that the STGCs in teratocarcinoma-like tumors derived from Parp���/��� clones belong to the trophoblast cell lineage. Our findings thus suggest that differentiation of ES cells into STGCs was possibly induced by the lack of Parp during the development of teratocarcinoma.

Regulation of Telomere Length by Checkpoint Genes in Schizosaccharomyces pombe

We have studied telomere length in Schizosaccharomyces pombe strains carrying mutations affecting cell cycle checkpoints, DNA repair, and regulation of the Cdc2 protein kinase. Telomere shortening was found in rad1, rad3, rad17, and rad26 mutants. Telomere lengths in previously characterized rad1 mutants paralleled the replication checkpoint proficiency of those mutants. In contrast, rad9, chk1, hus1, and cds1 mutants had intact telomeres. No difference in telomere length was seen in mutants affected in the regulation of Cdc2, whereas some of the DNA repair mutants examined had slightly longer telomeres than did the wild type. Overexpression of the rad1+ gene caused telomeres to elongate slightly. The kinetics of telomere shortening was monitored by following telomere length after disruption of the rad1+ gene; the rate was ���1 nucleotide per generation. Wild-type telomere length could be restored by reintroduction of the wild-type rad1+ gene. Expression of the Saccharomyces cerevisiae RCK1 protein kinase gene, which suppresses the radiation and hydroxyurea sensitivity of Sz. pombe checkpoint mutants, was able to attenuate telomere shortening in rad1 mutant cells and to increase telomere length in a wild-type background. The functional effects of telomere shortening in rad1 mutants were assayed by measuring loss of a linear and a circular minichromosome. A minor increase in loss rate was seen with the linear minichromosome, and an even smaller difference compared with wild-type was detected with the circular plasmid.

The Werner Syndrome Protein Is Involved in RNA Polymerase II Transcription

Werner syndrome (WS) is a human progeroid syndrome characterized by the early onset of a large number of clinical features associated with the normal aging process. The complex molecular and cellular phenotypes of WS involve characteristic features of genomic instability and accelerated replicative senescence. The gene involved (WRN) was recently cloned, and its gene product (WRNp) was biochemically characterized as a helicase. Helicases play important roles in a variety of DNA transactions, including DNA replication, transcription, repair, and recombination. We have assessed the role of the WRN gene in transcription by analyzing the efficiency of basal transcription in WS lymphoblastoid cell lines that carry homozygous WRN mutations. Transcription was measured in permeabilized cells by [3H]UTP incorporation and in vitro by using a plasmid template containing the RNA polymerase II (RNA pol II)���dependent adenovirus major late promoter. With both of these approaches, we find that the transcription efficiency in different WS cell lines is reduced to 40���60% of the transcription in cells from normal individuals. This defect can be complemented by the addition of normal cell extracts to the chromatin of WS cells. Addition of purified wild-type WRNp but not mutated WRNp to the in vitro transcription assay markedly stimulates RNA pol II���dependent transcription carried out by nuclear extracts. A nonhelicase domain (a direct repeat of 27 amino acids) also appears to have a role in transcription enhancement, as revealed by a yeast hybrid���protein reporter assay. This is further supported by the lack of stimulation of transcription when mutant WRNp lacking this domain was added to the in vitro assay. We have thus used several approaches to show a role for WRNp in RNA pol II transcription, possibly as a transcriptional activator. A deficit in either global or regional transcription in WS cells may be a primary molecular defect responsible for the WS clinical phenotype.

The ATM homologue MEC1 is required for phosphorylation of replication protein A in���yeast

Replication protein A (RPA) is a highly conserved single-stranded DNA-binding protein, required for cellular DNA replication, repair, and recombination. In human cells, RPA is phosphorylated during the S and G2 phases of the cell cycle and also in response to ionizing or ultraviolet radiation. Saccharomyces cerevisiae exhibits a similar pattern of cell cycle-regulated RPA phosphorylation, and our studies indicate that the radiation-induced reactions occur in yeast as well. We have examined yeast RPA phosphorylation during the normal cell cycle and in response to environmental insult, and have demonstrated that the checkpoint gene MEC1 is required for the reaction under all conditions tested. Through examination of several checkpoint mutants, we have placed RPA phosphorylation in a novel pathway of the DNA damage response. MEC1 is similar in sequence to human ATM, the gene mutated in patients with ataxia-telangiectasia (A-T). A-T cells are deficient in multiple checkpoint pathways and are hypersensitive to killing by ionizing radiation. Because A-T cells exhibit a delay in ionizing radiation-induced RPA phosphorylation, our results indicate a functional similarity between MEC1 and ATM, and suggest that RPA phosphorylation is involved in a conserved eukaryotic DNA damage-response pathway defective in A-T.

Antisense-mediated decrease in DNA ligase III expression results in reduced mitochondrial DNA integrity

The human DNA ligase III gene encodes both nuclear and mitochondrial proteins. Abundant evidence supports the conclusion that the nuclear DNA ligase III protein plays an essential role in both base excision repair and homologous recombination. However, the role of DNA ligase III protein in mitochondrial genome dynamics has been obscure. Human tumor-derived HT1080 cells were transfected with an antisense DNA ligase III expression vector and clones with diminished levels of DNA ligase III activity identified. Mitochondrial protein extracts prepared from these clones had decreased levels of DNA ligase III relative to extracts from cells transfected with a control vector. Analysis of these clones revealed that the DNA ligase III antisense mRNA-expressing cells had reduced mtDNA content compared to control cells. In addition, the residual mtDNA present in these cells had numerous single-strand nicks that were not detected in mtDNA from control cells. Cells expressing antisense ligase III also had diminished capacity to restore their mtDNA to pre-irradiation levels following exposure to ��-irradiation. An antisense-mediated reduction in cellular DNA ligase IV had no effect on the copy number or integrity of mtDNA. This observaion, coupled with other evidence, suggests that DNA ligase IV is not present in the mitochondria and does not play a role in maintaining mtDNA integrity. We conclude that DNA ligase III is essential for the proper maintenance of mtDNA in cultured mammalian somatic cells.

Direct DNA binding by Brca1

The tumor suppressor Brca1 plays an important role in protecting mammalian cells against genomic instability, but little is known about its modes of action. In this work we demonstrate that recombinant human Brca1 protein binds strongly to DNA, an activity conferred by a domain in the center of the Brca1 polypeptide. As a result of this binding, Brca1 inhibits the nucleolytic activities of the Mre11/Rad50/Nbs1 complex, an enzyme implicated in numerous aspects of double-strand break repair. Brca1 displays a preference for branched DNA structures and forms protein���DNA complexes cooperatively between multiple DNA strands, but without DNA sequence specificity. This fundamental property of Brca1 may be an important part of its role in DNA repair and transcription.