305,284 research outputs found
Bond slip model for generalized excitations
No full textCorrect evaluation for bond-slip effects is a crucial point when investigating progressive damage of reinforced concrete structures under random or earthquake excitations. For bridges, this aspect affects in particular the seismic response of piles' base and pier-deck joint in Integral Abutment Bridges as well. The need for a bond model, more accurate than those currently available in literature, without renouncing to ease of implementation, suggested to develop a new one. This model is defined by summing the effects of different bond resistance contributes (namely mechanical bond, friction bond and virgin bond) defined by means of continuous functions. This allows to fit, with reasonable precision, experimental monotonic and cyclic bond-slip paths, even along reloading branches. New relationships have been provided for updating the main law parameters at each load reversal. Moreover a specific progressive damage rule is introduced, able to account for generalized excitation. The proposed law has been validated by comparison with several existing pull-out cyclic data obtained from short-anchorage tests in good confinement conditions. © 2012 Taylor & Francis Group
Bridge Structural Optimization Through Step-by-Step Evolutionary Process
No full textIn this paper, the structural optimization process aiming to reduce the weight of the superstructure of a five span arch bridge, built in the Province of Venice, Italy, and spanning the Piave River in the town of San Donà, is presented. The original project, with a pre-stressed concrete superstructure, was re-considered during construction because of the following two unexpected events. First, the approved new seismic national regulation became effective when the bridge was already partially built. As a result, existing foundations became unable to withstand the prescribed new seismic action. Furthermore, the Venice Water Authority, responsible for the management of the river spanned by the bridge, declared that erection phases without any provisional supports and scaffolding , resting on the riverbed, as foreseen by the original project, should be preferred. Between the two possible identified design strategies able to deal with the mentioned problems, namely, the strengthening of the foundations or the lightening of the superstructure, the second option was chosen, on the basis of engineering judgement concerning the simplification of construction procedures, timing and budget. The search for the lightest possible solution, with the restraint given by the approved aesthetics of the original design and the need of keeping within the former budget, brought to the conclusion that an evolutionary structural optimization (ESO) process could be suitably applied to a composite steel and concrete superstructure
Degustação e avaliação sensorial de Vinhos.
No full textO vinho é uma bebida complexa pela sua composição físico-química, com grande variabilidade nos descritores sensoriais quanto aos parâmetros visuais, olfativos e gustativos nos mais diversos tipos de produtos. A qualidade e tipicidade de vinhos depende do potencial enológico das uvas na colheita, que é influenciado, por sua vez, pelos fatores naturais, clima e solo, e induzidos pelo fator humano, tanto no campo, ligados à vitivinicultura, como na vinícola, ligados à enologia. Esses fatores juntos, clima, solo e homem, formam o tripé da vitivinicultura e enologia chamado ?terroir?
An Application of Topological Optimization to Bridge Design
No full textRecently, structural optimization has become an important tool for structural designers, because it allows a better exploitation of material, thus decreasing a structure's self-weight and saving material costs. Moreover, structural optimization helps the designer to find innovative design solutions and structural forms that not only better exploit material but also give the structure greater aesthetic value from an architectural point of view. In this article, the seismic retrofitting of a bridge originally designed in reinforced concrete is illustrated, showing how lightening the bridge superstructure, rather than reinforcing the already completed foundations and abutments, allowed these latter features to resist greater seismic actions as required in the recent update of the Italian seismic code. Therefore, besides using the steel-concrete composite typology, the bridge superstructure was lightened through structural optimization. After having optimized the thickness of webs and flanges, it was necessary to further lighten the bridge superstructure by removing unexploited material from the bottom flange through the insertion of large cavities. For this purpose, topology optimization is shown to be a powerful tool that allowed the designer to find that the hole shape was basically elliptic, thus suggesting their regularization as ellipses. Comparisons were made between several design solutions, each characterized by a specific volume reduction of the bottom flange. Identification of the highest-performing solutions through computer-aided procedures led to a weight reduction of 40% with respect to the design solution in reinforced concrete. Retrofitting the already existing foundations and abutments to satisfy the updated provisions of the new seismic code was thus avoided by defining an innovative layout of arch bridges with holes in the bottom flange, which has never been used before
TOPOLOGY OPTIMIZATION OF BRIDGES SUPPORTED BY A CONCRETE SHELL
No full textA shell-supported footbridge was designed by shaping an anticlastic membrane in compression between deck and foundations. Since it would be subject to biaxial compression, it was appropriate to be made of concrete because concrete strength could be exploited and crack propagation prevented. With reference to Musmeci's work, a form-finding algorithm shaped the shell as a tension structure with same loads, restraint reactions and internal normal forces, but with the opposite sign. Using a finite element (FE) model of the shell, unwished bending moments (and therefore tensile stresses) were, however, found, because of second order displacements and (contrary to a tension structure) because of the bending stiffness of the reinforced concrete (RC) shell. Tensile stresses were progressively eliminated by removing material from the shell regions where unwished bending moments occurred. For this purpose, topology optimization with the Solid Isotropic Material with Penalization (SIMP) method was used, and different shell structures with cavities for different values of given volume reduction were obtained. Appropriate indexes for structural response were defined, and an optimization index was finally used to identify the most suitable pattern of cavities along the shell
follow-up a lungo termine ed outcome visivo in due fratelli affetti da sindrome di Alstrom con supplementazione di DHA
No full textAspetti oftalmologici funzionali nel cerebral visual impairment: studio longitudinale di 50 casi
No full textProdução de mudas de videira (Vitis spp.) por enxertia de mesa.
No full textA muda de videira é obtida através da multiplicação vegetativa, seja utilizandose estacas da produtora, em plantio direto, conhecida por ?pé-franco?, ou através do processo de enxertia. A muda de ?pé-franco? é utilizada somente para cultivares americanas (Vitis labrusca) e híbridas, conhecidas como uvas comuns, por apresentarem certa tolerância à filoxera (Daktylosphaera vitifoliae), enquanto que a muda enxertada é obrigatória para as uvas finas (Vitis vinifera) por serem muito suscetíveis a essa praga. A produção da muda por enxertia é mais recomendada, mesmo quando se trata de uvas comuns, pois a utilização do porta-enxerto, além de assegurar um controle mais eficiente da filoxera, pode agregar outras vantagens, como melhorar a qualidade da uva, conferir maior resistência a doenças de solo, maior adaptação a diferentes tipos de solos, maior precocidade, etc.Disponível também no formato online
Experimental and numerical investigation of the cyclic behaviour of an innovative prefabricated beam-to-column joint
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