Neste trabalho analisa-se a resistência à punção e a ductilidade das ligações laje-pilar em doze modelos de lajes-cogumelo de concreto armado, nas quais se efetuam combinações de emprego de concreto de alta resistência, diferentes volumes de fibras de aço e uso de armadura transversal na forma de conectores de aço tipo pino. Todas as lajes são quadradas com 1160 mm de lado e 100 mm de espessura. A armadura de flexão foi composta de barras de aço de 10 mm espaçadas de tal forma a resistir a um momento fletor único em ambas direções. Os conectores, quando utilizados, foram dispostos radialmente e compostos de barras de aço de 6.6 mm soldadas a segmentos de ferro chato nas duas extremidades. Para avaliar a capacidade resistente dos modelos de ligação laje-pilar e observar o ganho de ductilidade que as fibras proporcionam, foram ensaiados segmentos-de-laje, os quais representam uma faixa destes modelos de ligação laje-pilar. Foi utilizado um sistema de ensaio dotado de atuador hidráulico servo-controlado, programado para ensaio com deformação controlada e aquisição contínua dos dados, o que permitiu a avaliação do comportamento pós-pico de resistência e a realização de medições de resistência residual. Várias hipóteses de cálculo foram utilizadas para avaliar a resistência última das ligações laje-pilar. Empregou-se um critério de classificação para caracterizar o tipo de ruptura em: punção ou flexão predominante ou uma combinação de punção-flexão. Constatou-se que o emprego de concreto de alta resistência, juntamente com armadura transversal, aumenta substancialmente a resistência da ligação laje-pilar, e quando combinado com fibras de aço, consegue-se um considerável aumento da ductilidade. / This work analyses the punching shear resistance and ductility of slab-column connections on twelve concrete flat slab models. The model characteristics resulted from combinations of the application of high or ordinary strength concrete, different steel fiber volume fractions and use or not of shear reinforcement. All the slabs are square with 1,160 mm of side and 100 mm of thickness. The main flexural reinforcement was composed of 10 mm steel bars spaced in such a way to resist to the same bending moment in both directions. When used, the shear reinforcement of steel studs were disposed in radial directions and consisted of 6.6 mm steel bars welded to flat steel segments in their ends. To evaluate the resistant capacity of slab-column connection models and to observe the ductility that the fibers provide, they were rehearsed segments-of-slab, which represents a strip of these slab-column connection models. A testing system with a servo-controlled hydraulic jack was used and it was programmed for a controlled deformation test and continuous data acquisition. This method allowed the evaluation of the post-peak strength behavior and the measurement of residual resistance forces. Several calculations hypotheses were used to evaluate the ultimate strength of the slab-column connections. A classification criterium was applied to characterize the failure type as: predominant punching or flexure or a combination of punching-flexure. It was verified that the application of high strength concrete, together with shear reinforcement, increases substantially the slab-column connection strength, and, when combined with steel fibers, a considerable ductility increase is achieved.

Ce travail de thèse considère les modes de déformations des verres métalliques produits sous différentes formes (verres massifs, rubans et particules). La déformation hétérogène dans des échantillons massifs de verres métalliques à base de zirconium est étudiée par microscopie électronique à balayage. Le dégagement rapide de l'énergie élastique stockée sous forme de chaleur lors de la déformation est responsable de la fusion locale observée dans les bandes de cisaillement. Le calcul du profil de température autour d'une bande par un modèle analytique est cohérent avec les observations morphologiques et les rapports d'apparition de nano-cristaux dans la zone déformée. La mise en forme par recuit des rubans de verres métalliques a été étudiée. L'étude aboutit à la mise en forme sans fragilisation des rubans appartenant à différentes compositions de systèmes d'alliages dit métal-métal et métal-métalloïde. Un processus de traitement thermique est suggéré pour assurer la redistribution des contraintes imposées avant l'intervention de la fragilité thermique. Un brevet industriel basé sur ces résultats a été conjointement déposé avec un grand fabriquant de montres mécaniques. De nouveaux matériaux composites d'alliages légers commerciaux à base de Mg et d'Al renforcés par des dispersions de particules de verres métalliques ont été réalisés sans porosité. Une amélioration très nette des propriétés mécaniques est obtenue. / This thesis features the two modes of deformation of metallic glasses produced under different forms (bulk, ribbons and particles). Inhomogeneous deformation in bulk samples is studied by scanning electron microscopy. Heat generated by elastic energy release during deformation is responsible for the melting observed in shear bands, and calculations using an analytical model of the temperature profile around a band are consistent with morphological observations and reports of appearance of nano-crystals in or next to deformed areas. Shaping by annealing glassy ribbons was carried out. The study presents successful shaping without embrittlement of ribbons of different metal-metal and metal-metalloid compositions of glassy systems. A heat treatment process is suggested for redistribution of applied stresses before the intervention of thermal embrittlement. A joint patent for exploiting the findings has been filed with a major producer of mechanical watches. Development of new strong and light composite materials by dispersing glassy particles in aluminum and magnesium based matrices is presented and significant improvement in mechanical properties is obtained.

[pt] Estuda-se a consideração de comportamento inelástico do material na geração de espectros de resposta de projeto. Para tanto, trabalha-se sobre um sistema secundário simplificado acoplado a um pórtico de cinco andares com características dinâmicas ajustadas para modelar um sistema principal real, de uma usina nuclear. Faz-se um estudo paramétrico sobre estes sistemas acoplados onde são variados os parâmetros: fator de escoamento, a intensidade da excitação e o nível de amortecimento. É proposto um fator de dutilidade global formulado em termos de trabalho externo realizado sobre o sistema secundário. São obtidos espectros de dutilidade e de resposta. A análise de tais espectros fornece informações sobre o desempenho do sistema secundário e seus suportes e conclui por fatores de transposição entre os espectros elástico e inelástico. Propõe-se metodologia para obtenção de espectros de resposta elásticos e inelásticos que levam em conta o acoplamento entre os sistemas principal e secundário, o movimento relativo dos suportes e o compromisso probabilístico entre as ordenadas do espectro e a sismicidade da região expressa em termos de uma função densidade de espectro de potência objetivo para a aceleração do terreno. Um exemplo de obtenção de espectros de resposta acoplada de projeto uniformemente provável inelástico é apresentado. / [en] The authors concern includes two main points in the subject of design response spectra generation for secondary systems in nuclear power plant structures: the consideration of inelastic behavior in the secondary systems materials and the production of uniformly probable design response spectra. One works with a previously developed secondary system model attached to primary structure model tuned to the frequency range of a nuclear power plant building. A global ductility factor is formulated relating the plastic to the overall work done by the seismic external forces on the secondary system. This factor together with a particular definition of the yielding factor allows one to determine elastic to inelastic spectrum transpose factors. A methodology is proposed to generate uniformly probable coupled response spectra for multiply supported inelastic secondary systems. The seismic excitation is prescribed by a target power spectrum density function of the ground acceleration and an internal pressure condition is added to the seismic action. Examples illustrate the application of this proposed methodology.

Includes corrigenda (inserted at front) and list of publications published as a result of this research. Includes bibliographical references (leaves 192-199) Investigates the overload behaviour and modes of collapse of reinforced concrete flexural members containing 500MPa grade reinforcing steel and evaluates the adequacy of current ductility requirements for design according to AS 3600 to ensure strength and safety.

Includes corrigenda (inserted at front) and list of publications published as a result of this research. / Includes bibliographical references (leaves 192-199) / xxvii, 223 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the overload behaviour and modes of collapse of reinforced concrete flexural members containing 500MPa grade reinforcing steel and evaluates the adequacy of current ductility requirements for design according to AS 3600 to ensure strength and safety. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 2002

Shear-wall dominant multi-story reinforced concrete structures, constructed by using a special tunnel form technique are commonly built in countries facing a substantial seismic risk, such as Chile, Japan, Italy and Turkey. In 1999, two severe urban earthquakes struck Kocaeli and D&uuml / zce provinces in Turkey with magnitudes (Mw) 7.4 and 7.1, respectively. These catastrophes caused substantial structural damage, casualties and loss of lives. In the aftermath of these destructive earthquakes, neither demolished nor damaged shear-wall dominant buildings constructed by tunnel form techniques were reported. In spite of their high resistance to earthquake excitations, current seismic code provisions including the Uniform Building Code and the Turkish Seismic Code present limited information for their design criteria. This study presents experimental investigation of the panel unit having H-geometry. To investigate the seismic behavior of panel buildings, two prototype test specimens which have H wall design were tested at the Structural Mechanics Laboratory at METU. The experimental work involves the testing of two four-story, 1/5-scale reinforced concrete panel form building test specimens under lateral reversed loading, simulating the seismic forces and free vibration tests. Free vibration tests before and after cracking were done to assess the differences between the dynamic properties of uncracked and cracked test specimens. A moment-curvature program named Waller2002 for shear walls is developed to include the effects of steel strain hardening, confinement of concrete and tension strength of concrete. The moment-curvature relationships of panel form test specimens showed that walls with very low longitudinal steel ratios exhibit a brittle flexural failure with very little energy absorption. Shear walls of panel form test specimens have a reinforcement ratio of 0.0015 in the longitudinal and vertical directions. Under gradually increasing reversed lateral loading, the test specimens reached ultimate strength, as soon as the concrete cracked, followed by yielding and then rupturing of the longitudinal steel. The displacement ductility of the panel form test specimens was found to be very low. Thus, the occurrence of rupture of the longitudinal steel, as also observed in analytical studies, has been experimentally verified. Strength, stiffness, energy dissipation and story drifts of the test specimens were examined by evaluating the test results.

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In this thesis we look at one of the aging mechanisms that may have affected current aged Nuclear Power Plants (NPPs). Irradiation as an age-related degradation mechanism is studied for Reinforced Concrete (RC) in NPPs. This problem can be important for aged reactor buildings, radwaste buildings, spent nuclear fuel, research reactors, or accelerators that experience high levels of radiation close to existing thresholds. Mechanical properties of concrete are the most important parameters affected by radiation in NPPs. Compressive strength of concrete is reduced between 80 and 35 \% for radiation fluences between $2\times 10^{19}$ and $2\times 10^{21} n/cm^2$. Tensile strength reduction is more significant than compressive strength. It is reduced between 20 and 80 \% for a radiation fluence equal to $5\times 10^{19}$. We chose three radiation levels $2\times 10^{19}$, $2\times 10^{20}$, $2\times 10^{20}$ based on experimental results as the critical levels of radiation that RC structures in NPPs may be exposed to. Structures susceptible to the problem are mostly RC walls; so the RC panel is chosen as an appropriate representative scale element for the analysis. The effect of radiation on mechanical properties of concrete is considered to analyze degraded scale elements. Material properties, geometry, and loading scenarios of scale elements are selected to be close to actual quantities in existing nuclear power plant. Elements are analyzed under six types of loading combination of shear and axial loading conditions. A nonlinear finite element program, Membrane-2000, based on the Modified Compression Field Theory (MCFT) is used to solve scale elements numerically. Element behaviors are studied considering the factors influence ultimate strength capacity, failure mode, and structural ductility index of members. The results show that ultimate shear capacity of the elements subjected to combinations of shear and tension loading are reduced significantly for highly reinforced elements ($1.35<\rho<1.88$) in $2\times 10^{21} n/cm^2$ radiation. RC panels under shear-biaxial and uniaxial compression also show significant strength capacity reduction in radiation levels $2\times 10^{20} n/cm^2$ and $2\times 10^{21} n/cm^2$, respectively. Failure modes of the elements change from yielding of steel to shear failure by increasing level of degradation for the elements with reinforcement ratio between 0.9 and 1.88. Ductility of the RC panels is reduced significantly in the critical levels of radiation. Ductility of the elements became less than the allowable ductility value by increasing level of radiation.

The difficulty in developing bolted connection designs lies in the limitations in existing methods to characterize their strength and typically nonlinear response due to the complex interaction of the bolts and structural components. Yet it is necessary for the engineer to be able to determine the three main connection response characteristics: stiffness, strength, and ductility to account for their influence on the overall structural response behavior. The need for better connection response characterization becomes even more crucial in a performance based design approach or when designing partially-restrained moment frames. Several welded moment resisting frame connections were found to have serious failures following the 1994 Northridge earthquake leading to more interest and research on bolted connections as an alternative. In this study a refined three dimensional nonlinear finite element modeling approach to accurately simulate the response of bolted connections is presented. Sensitivity studies of modeling parameters are also performed. A nonlinear response dataset of over 400 connection cases is generated using this approach with a parametric bolted angle connection model. The use of a parametric Richard-Abbott type function and a neural network, calibrated using the response dataset, as practical tool to model the nonlinear stiffness response of bolted connections under monotonic loading is demonstrated and assessed. Failure criteria that can be practically used in conjunction with the refined three dimensional finite element models without any additional modeling requirements are developed. The stress modified critical strain (SMCS) criterion based on the void growth and coalescence mechanism initiating ductile fracture in steel is used for determining failure in the connection member. The bolt failure criterion developed is a mechanics based model using the elliptical interaction of the tensile and shear capacity envelope. The failure criteria and bolted angle response dataset is combined to assess in detail the impact of geometry and topography of the bolted angle connections on the following response characteristics: strength, initial stiffness, plastic stiffness, and absolute ductility or the displacement capacity. Finally, using the dataset of bolted angle connection response, along with their capacities and failure modes determined using the developed failure criteria, the prying strength models in the AISC LRFD Specifications, Eurocode, and a hybrid model are assessed and found to be very conservative for some cases. Based on these results a modified Eurocode and hybrid prying strength model is proposed which greatly improves the prying strength prediction. These prying models are assessed and verified using experimental data found in literature.