Shear behaviour of reinforced cconcrete slab under concentrated load: an investigation through non-linear and sequentially linear analysis

English: The assessment of safety in existing bridges and viaducts led the Ministry of Public Works of the Netherlands to finance a specific campaing aimed at the study of the response of the elements of these infrastructures. Therefore, this activity is focused on the investigation of the behaviour of reinforced concrete slabs under concentrated loads, adopting finite element modeling and comparison with experimental results. These elements are characterized by shear behaviour and crisi, whose modeling is, from a computational point of view, a hard challeng, due to the brittle behavior combined with three-dimensional effects. The numerical modeling of the failure is studied through Sequentially Linear Analysis (SLA), an alternative Finite Element method, with respect to traditional incremental and iterative approaches. The comparison between the two different numerical techniques represents one of the first works and comparisons in a three-dimensional environment. It's carried out adopting one of the experimental test executed on reinforced concrete slabs as well. The advantage of the SLA is to avoid the well known problems of convergence of typical non-linear analysis, by directly specifying a damage increment, in terms of reduction of stiffness and resistance in particular finite element, instead of load or displacement increasing on the whole structure . For the first time, particular attention has been paid to specific aspects of the slabs, like an accurate constraints modeling and sensitivity of the solution with respect to the mesh density. This detailed analysis with respect to the main parameters proofed a strong influence of the tensile fracture energy, mesh density and chosen model on the solution in terms of force-displacement diagram, distribution of the crack patterns and shear failure mode. The SLA showed a great potential, but it requires a further developments for what regards two aspects of modeling: load conditions (constant and proportional loads) and softening behaviour of brittle materials (like concrete) in the three-dimensional field, in order to widen its horizons in these new contexts of study.

<>: per una filosofia di liberazione dell'uomo in Alberto Manzi latinoamericano

This dissertation is aimed at analysing deeply and thoroughly the most significant topics and features reflected in the Latin American literary work of Alberto Manzi. His almost thirty years of travelling and volunteering in the indigenous communities of South America formed a background of knowledge and experiences, which turned out to be crucial for the genesis of his Latin American trilogy. In the light of this, not only are ‘La luna nelle baracche’, ‘El loco’ and ‘E venne il sabato’ a speaking testimony of Manzi’s life and inner development, but they also offer a privileged perspective on the social, historical and religious situation of the people of Latin America. For a better understanding of the books, chapter one provides an extensive historical and economic commentary stretching over a century, from the collapse of the Spanish Empire to the rise of modern dictatorships in the late ‘70s, and the long democratic transition of the ‘80s. As far as the religious background is concerned, it is important to mention the influence of the liberation theology in the shaping of Manzi’s revolutionary thought. Indeed, chapter two identifies the precursors of the liberation theology, considers the effects of the Second Vatican Council on Latin America’s Catholic Church, and presents the methodology and the most powerful intuitions of the liberation theology. Finally, chapter three employs a critical analysis of Manzi’s Latin American trilogy, which focuses on his personal journal of his time in the austral continent, and Sonia and Giulia Manzi’s testimony published in a book entitled ‘Non è mai troppo tardi’. Chapter three provides an in-depth analysis of the evolution of the author’s revolutionary thought and plot dynamics; it discusses the psychological profile of the characters, the cultural features of the indigenous traditions, and the author’s urge to involve the readership in a permanent process of self-questioning.