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The use of concrete-filled tubular composite members and composite beams has been implemented in many structural systems due to their robust structural performance, constructability, and inherent synergy when the steel and concrete components are properly designed and detailed together. While extensive research has been conducted on concrete-filled steel structural members, relatively little has been done regarding similar composite connections. Understanding how composite connections behave in structures and how they should be modeled during the design process is crucial to predict the actual structural behavior of these types of elements when subjected to different loading conditions. The goal of this research is to numerically evaluate CFTs or SRCs members and their connections subjected to axial, shear, and flexural load. Predicting composite connection behavior is exceptionally challenging due to the coupled behavior of the steel and concrete, the residual stresses in the steel, local buckling of the connection, and the sensitivity of the stress-strain response to the steel-concrete contact and confinement performance. To address these issues, a thorough literature search has been carried out and a state-of-the-art report on experimental and numerical models for composite connections is presented. The selected tests represent a range of geometries, materials, and governing failure modes. Initially, a generic connection modeling process was developed and calibrated against a classical test, then three more connections were modeled. To further the understanding of composite behavior, shear studs in steel-concrete composite beams were modeled next, taking as reference a recent experimental program that resulted in an unusual failure. Results indicate that the model can reproduce the most important behavioral aspects observed in the tests, tracking well the strength and stiffness of the samples up to ultimate. The load-deformation curves of the experimental specimens and the analytical models show very good agreement in their transitions and indicate that the behavior of the composite joints is controlled mainly by both the strength of the concrete and the confining effect of the steel tube in the joint. A data appendix containing 135 tests is described and the main characteristics of these tests are summarized in the text. / Doctor of Philosophy / Every day the population increase is more evident, and the main cities of the world are densifying. This implies the accelerated construction of all types of structures, especially tall residential buildings. For the design of these structures, architects design increasingly slender structures, which must be resilient under all types of forces. The foregoing is exerting pressure on structural engineers to design structures that have the capacity to be built in the shortest possible time without losing their functionality and safety. This is where steel and concrete composite construction plays an important role. The main advantage of composite construction is the synergy of both materials. Concrete is inexpensive and provides high stiffness, mass, and fire resistance. Structural steel has high strength, ductility, lightweight, and ease of construction. Composite construction has been used for a long time in tall buildings, and experimental and numerical research has been carried out, especially on the beam and column elements. However, comparatively little research has been done on composite connection behavior and design. This dissertation proposes a numerical evaluation of the composite connections in beams and columns under different types of loads in order to establish modeling parameters that facilitate the analysis and structural design of these elements. The important numerical models are validated with experimental investigations. The results show that the numerical models are capable of simulating the structural behavior of the tests, especially the damage mechanisms and the modeling of local behavior. This study contributes to the development of simulations of composite connections, determining modeling parameters, such as the contact resistance between steel and concrete and the distribution of shear studs in composite beams, among others.

Multi-pass fusion welding by a filler wire (welding electrode) is normally carried out to join thick steel sections used in most engineering applications. Welded joints in an installation, is the area of critical importance, since they are likely to contain a higher density of defects than the parent metal and their physical properties can differ significantly from the parent metal. Fusion arc welding process relies on intense local heating at a joint where a certain amount of the parent metal is melted and fused with additional metal from the filler wire. The intense local heating causes severe transient thermal gradients in the welded component and the resulting uneven cooling that follows produces a variably distributed residual stress field. In multi-pass welds, multiple thermal cycles resulted in a variably distribution of residual stress field across the weld and through the thickness. These complex thermal stresses generated in welds are undesirable but inevitable during fusion welding. Presence of such tensile residual stresses can be detrimental to the service integrity of a welded structure. In addition to a complex distribution of residual stress state, multi-pass welds also forms dendritic grain structure, which are repeatedly heated, resulting in segregation of alloying elements. Dendritic grain structure is weaker and segregation of alloying elements would result in formation of corrosion microcells as well as reduction in overall corrosion prevention due to depletion of alloying elements.

It is vital that Turkey keep abreast of developments in the world and build up its technology to become a developed country. Steel construction is one of these areas. In this context, the main purpose of this study was to define, analyze and evaluate the general characteristics of structural steel and steel construction with the purpose of throwing new light on its advantages and disadvantages. Within this framework, a literature survey was conducted on structural steel components and structures / and on steel construction in Turkey. Additionally, a case study was carried out on a steel office building in Ankara. In this, the T&uuml / rkiye Esnaf ve Sanatkar Kredi Kefalet Kooperatifleri Merkez Birligi (TESKOMB) Building was investigated in terms of the design and production criteria for steel structures and to determine problems faced during these processes. As a result of this study, the existing condition of the construction sector and the means to improve use of structural steel in Turkey were discussed more realistically.

Les aciers de construction au carbone manganèse (C-Mn) sont largement utilisés pour diverses applications mécaniques, et en particulier pour les tuyauteries de circuit secondaire des centrales nucléaires de type Réacteurs à Eau sous Pression (REP). La robustesse des composants des circuits sous pression des REP vis-à-vis de la fissuration doit être démontrée, tant au niveau de la conception que de l’exploitation. Les aciers au C-Mn sont sensibles au vieillissement sous déformation qui entraîne une chute importante de ductilité et de ténacité entre 150 et 350°C,températures de service des tuyauteries du circuit secondaire. Ce phénomène est dû à une interaction entre les atomes de solutés et les dislocations, et peut se traduire entre autres par une sensibilité négative de la contrainte à la vitesse de déformation, et des localisations de la déformation plastique (Lüders, Portevin – Le Chatelier). L’origine physique du vieillissement sous déformation a été beaucoup étudiée, surtout dans les métaux purs, en relation avec le phénomène Portevin-Le Chatelier (PLC), mais son influence sur les propriétés mécaniques et notamment la rupture reste très controversée. L’objectif de la thèse est de modéliser le comportement et la rupture d’un acier au C-Mn dans un large domaine de température compris entre 20 et 350°C, en tenant compte des phénomènes de vieillissement sous déformation, et en particulier des localisations de déformation. Le comportement et la rupture de l’acier au C-Mn étudié ont été caractérisés expérimentalement dans le domaine 20-350°C à l’aide d’essais de traction sur éprouvettes lisses, sur éprouvettes axisymétriques entaillées, et d’essais de déchirure sur éprouvettes CT. Le modèle d’Estrin Kubin McCormick, prenant en compte le vieillissement sous déformation, a été identifié dans cette même gamme de température et la plupart des effets du vieillissement sous déformation ont pu être simulés numériquement : sensibilité négative de la contrainte d’écoulement à la vitesse de déformation, bandes de Lüders, effet PLC, modification des propriétés mécaniques de traction… Le modèle ainsi identifié a été appliqué à l’étude de la rupture d’éprouvettes lisses, entaillées et CT. La baisse de l’allongement réparti est bien décrite en traction sur éprouvettes lisses. Pour prévoir la rupture des éprouvettes entaillées, l’approche locale de la rupture a été appliquée (modèle de Rice et Tracey). Cette étude a donc permis de disposer d’un modèle prenant en compte le vieillissement sous déformation de 20°C à 350°C et décrivant les localisations de déformation plastique de type Lüdersou PLC, pour différentes géométries d’éprouvettes. Ce modèle a été utilisé pour simuler la rupture des aciers au C-Mn, suscitant ainsi une vision nouvelle pour comprendre la baisse de ductilité associée au vieillissement dynamique. / Pas de résumé en anglais disponible.

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[ES] Esta tesis doctoral tiene por objetivo general expandir la escultura quiteña (de la ciudad de Quito), normalmente supeditada a convencionalismos sociales ampliamente difundidos y al conservadurismo académico local, ambos mayormente centrados en la noción de monumento. Para ello se ha desarrollado un proceso investigativo y creativo en bucle, definido en los objetivos específicos programados, a partir de los fundamentos teóricos, históricos, técnicos y tecnológicos de la escultura cinética, incluyendo la mención de sus principales practicantes, extranjeros y locales; así como de los conceptos de mediación, juego y público, y los recursos relacionados a estos, aplicados y aplicables a la escultura. De allí se ha establecido un método creativo para el diseño de las obras cinéticas propuestas. Método que se alimenta tanto del campo específico del arte como de otras disciplinas estudiadas; y que posibilita la creación de obras escultóricas cinéticas en acero estructural, sistematizando y documentando su proceso creativo. Finalmente, se ha evaluado la interactividad generada entre las esculturas realizadas y el público de las mismas. Con todo ello, cual objetivo superior, esta investigación-creación aspira a contribuir al campo del arte local proporcionando nuevas perspectivas y prácticas escultóricas mediante la inserción, cual intervención social en la esfera académica quiteña, de la escultura cinética corporal y semánticamente interactiva. / [CA] Aquesta tesi doctoral té per objectiu general expandir l'escultura quiteña, normalment supeditada a convencionalismes socials ámpliament difosos i al conservadorisme acadèmic local, tots dos majorment centrats en la noció de monument. Per a això s'ha desenvolupat un proce's d'investigació i creatiu en bucle, definit en els objectius específics programats, a partir dels fonaments teòrics, històrics, tècnics i tecnològics de l'escultura cinètica, incloent-hi l'esment dels seus principals practicants, estrangers i locals; així com dels conceptes de mediació, joc i públic, i els recursos relacionats a aquests, aplicats i aplicables a l'escultura. D'alli' s'ha establert un métode creatiu per al disseny de les obres cinètiques proposades. Mètode que s'alimenta tant del camp específic de l'art com d'altres disciplines estudiades; i que possibilita la creació d'obres escultòriques cine¿tiques en acer estructural, sistematitzant i documentant el seu procés creatiu. Finalment, s'ha avaluat la interactivitat generada entre les escultures realitzades i el públic d'aquestes. Amb tot això, com a propòsit superior, aquesta recerca-creació aspira a contribuir al camp de l'art local proporcionant noves perspectives i pràctiques escultòriques mitjancant la inserció, com intervenció social en l'esfera acadèmica quiteña, de l'escultura cinètica corporal i semànticament interactiva. / [EN] The general objective of this doctoral thesis is to expand the sculpture in Quito, normally conditioned by widely diffused social conventions and local academic conservatism, both mostly centered on the notion of monument. For this, a looping investigative and creative process has been developed, defined in the specific programmed objectives, based on the theoretical, historical, technical and technological foundations of kinetic sculpture, including the mention of its main practitioners, foreign and local; as well as the concepts of mediation, game and public, and the resources related to these, applied and applicable to sculpture. From there, a creative method has been established for the design of the proposed kinetic artworks. Method that feeds both on the specific field of art and on other studied disciplines; and that enables the creation of kinetic sculptural works in structural steel, systematizing and documenting their creative process. Finally, the interactivity generated between the sculptures and their public has been evaluated. With all this, as a higher objective, this research-creation aspires to contribute to the field of local art by providing new perspectives and sculptural practices through the insertion, as a social intervention in the Quito academic sphere, of kinetic and semantically interactive corporal sculpture. / García Moreno, MF. (2023). Escultura cinética en acero estructural. El movimiento como agente mediador entre obra de arte y espectador. Caso Quito-Ecuador [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/192893

This dissertation discusses the potential for using a conventional main lateral-force resisting system, combined with the reserve strength in the gravity framing, and or auxiliary collapse-inhibiting mechanisms deployed throughout the building, or enhanced shear tab connections, to provide adequate serviceability performance and collapse safety for seismic and wind hazards in the central and eastern United States. While the proposed concept is likely applicable to building structures of all materials, the focus of this study is on structural steel-frame buildings using either non-ductile moment frames with fully-restrained flange welded connections not specifically detailed for seismic resistance, or ductile moment frames with reduced beam section connections designed for moderate seismic demands. The research shows that collapse prevention systems were effective at reducing the conditional probability of seismic collapse during Maximum Considered Earthquake (MCE) level ground motions, and at lowering the seismic and wind collapse risk of a building with moment frames not specifically detailed for seismic resistance. Reserve lateral strength in gravity framing, including the shear tab connections was a significant factor. The pattern of collapse prevention component failure depended on the type of loading, archetype building, and type of collapse prevention system, but most story collapse mechanisms formed in the lower stories of the building. Collapse prevention devices usually did not change the story failure mechanism of the building. Collapse prevention systems with energy dissipation devices contributed to a significant reduction in both repair cost and downtime. Resilience contour plots showed that reserve lateral strength in the gravity framing was effective at reducing recovery time, but less effective at reducing the associated economic losses. A conventional lateral force resisting system or a collapse prevention system with a highly ductile moment frame would be required for regions of higher seismicity or exposed to high hurricane wind speeds, but buildings with collapse prevention systems were adequate for many regions in the central and eastern United States. / Ph. D.

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