Numerical models for the robustness assessment of reinforced concrete framed buildings

Cast in situ reinforced concrete frame is one of the most common options for civil buildings. Although earliest common usages of this solution date back to second half of 19th century, research activity is constantly developing to investigate several aspects, especially about nonlinear behaviour of reinforced concrete structures. Structural robustness of buildings is actually one of the key issues faced by the international scientific community. This expression is used to indicate a desirable property of a structure that allows it to withstand an accidental event, preventing progressive and/or disproportionate collapse. Interest in this topic has been growing rapidly after the collapse of Ronan Point Apartment Tower in Newham, East London, in 1968, when a gas explosion destroyed a loadbearing concrete panel causing the collapse of an entire corner of the building. Although the issue of progressive collapse of multi-storey frames has been widely studied in the last decades, according to the literature review, the actual structural response after a localised failure has not yet been fully understood. Besides, many design guidelines for preventing progressive collapse denote a lack of adequate theoretical supports. Several technics have been developed to evaluate the response after an accidental situation. In Europe, EN1991-1-7 has introduced the notional removal design strategy. This approach establishes that a building should be checked to ensure that upon the notional removal of each column or each beam supporting a column, or any nominal section of load-bearing wall, one at a time in each storey of the building, the structure remains stable exhibiting only localised failure. Currently one of the main solution to ensure robustness consists in tying together structural members by using continuous reinforcement. In this context, the designer is required to evaluate the global structural response, then the role played by the floor-system becomes crucial. However, this operation involves longer times for modelling and analyses. The study here presented is articulated through several points. The initial intent is to develop simplified models of the floor-system able to simulate its behaviour, to obtain accurate results through a more efficient modelling. Different numerical models will be presented. These will focus on distinct simplification levels, depending on the finite elements adopted. The codes used for nonlinear numerical analyses have been previously tested and validated on experimental tests on 2D and 3D specimens and both static and dynamic analyses. The second aim is to evaluate the effectiveness of different floor-system typologies on the global behaviour of reinforced concrete frames. Two typical reinforced concrete solutions are tested: the first exploits a bidirectional slab, while the second uses monodirectional joists with a collaborating slab. To compare the results, a structure with features common to most of the reinforced concrete buildings has been chosen as reference test. The considered scenarios involve the removal of four distinct columns: two internal ones with different boundary conditions, an edge column and a corner column, all the elements are placed at the ground floor level. The third aim is to evaluate the influence of several parameters on global response, to identify their possible influence on the phenomenon and to highlight which among these have a determining impact on the structural response. The factors investigated are: primary beams depth, columns depth, presence of bracing systems, continuous reinforcement amount and seismic detailing. The achieved results provide precise information on the overall structural behaviour, highlighting the key role played by certain factors such as the percentage of continuous reinforcement in the beams and the importance of seismic detailing. At the same time the analyses have highlighted the marginal influence exerted by other parameters like the stiffening contribution given by a bracing system or stiffer columns, whose effects may be considered negligible

Effect of concrete tensile strength in non linear analyses of 2D structures - a comparison between three commercial finite element softwares

Non-linear finite element method (FEM) allows to take into account material and geometrical non-linearities in the simulation of the behaviour of reinforced concrete structures. However, the accuracy of the numerical solution with respect to experimental tests is often questionable, especially in the case of 2D and 3D structures. Several competitions showed in the past significant scatter of the predicted results with respect to the correct ones. Even though internationally well-known computer softwares can be used to predict the structural response, the uncertainty of the numerical simulation cannot be neglected. Therefore, the application of finite element models to the assessment of concrete structures requires a proper investigation of the uncertainty related to the results of the simulations. This paper presents a comparison of numerical simulations of sixteen case studies taken from past experimental tests and modelled with three commercial non-linear softwares. The purpose of the investigation is to show how significant could be the difference between the experimental and numerically evaluated failure load and displacement in function of the code used and the variation of only one material parameter

Comparison between non-linear numerical models for R.C. shear walls under cyclic loading

The non-linear behaviour of concrete structures is the result of a series of phenomena, as material non-linear constitutive law and cracking process. As a consequence, in order to understand the behaviour of reinforced concrete members from elastic field to ul-timate condition, is necessary to use instruments able to simulate the material damaging evolution under growing loads. Commer-cial non-linear finite elements codes are generally able to simulate concrete behaviour with good approximation when a progressive incremental load is applied. However, the same result could not be reached under a cyclic loading. In this work two commercial non-linear finite element codes have been considered in order to assess the skill of these codes to simulate non-linear concrete be-haviour under cyclic loading. The results of six laboratory tests on shear walls have been compared with the ones obtained by means of numerical models and some conclusions on the numerical predictions are presented. / Il comportamento non lineare delle strutture realizzate in calcestruzzo è il risultato di una serie di fenomeni, come la non linearità della legge costitutiva del materiale ed il processo di fessurazione. Al fine di comprendere il comportamento degli elementi struttura-li in calcestruzzo armato è necessario disporre di strumenti in grado di simulare il progressivo danneggiamento del materiale in pre-senza di carichi crescenti. In generale, i codici di calcolo presenti in commercio sono in grado di cogliere abbastanza bene il compor-tamento delle strutture in cemento armato soggette a carichi monotoni crescenti. Risulta invece più complesso seguire il compor-tamento strutturale in presenza di un carico ciclico. In questo lavoro sono stati considerati due diversi codici di calcolo non lineare agli elementi finiti al fine di verificare la loro capacità nel simulare il comportamento di pareti a taglio soggette a un carico ciclico. Sono stati considerati i risultati di sei prove di laboratorio disponibili in letteratura; tali risultati sono stati confrontati con quelli otte-nuti numericamente per trarre delle conclusioni sull’affidabilità dei modelli numerici

a comparison between 3d printing and milling process for a spar cap fitting wing fuselage of uav aircraft

Abstract Topology optimization is playing an important role in the aircraft design. The demand of lower fuel consumption reflects on the optimization of the airframe of flying vehicles to reduce the structure weight, therefore improving the fraction of the payload. This work focuses on the replacement of an existing part (spar cap fitting) with the new topologically optimized part to be manufactured with 3D printing (Selective Laser Sintering -SLS). The manufacturing constraints (minimum dimension, growth orientation) influence on the optimal results is evaluated to compare traditional milling process' performance with the new SLS technique

Geochemical tracers in complex hydrogeological settings: the Roccamonfina volcanic vs. mt. massico sedimentary aquifers (southern Italy)

Volcanic aquifers, sedimentary basins, hydrogeochemistry, hydrogeology, isotopic composition

Intuitive Robot Teleoperation through Multi-Sensor Informed Mixed Reality Visual Aids

© 2021 The Author(s). This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/.Mobile robotic systems have evolved to include sensors capable of truthfully describing robot status and operating environment as accurately and reliably as never before. This possibility is challenged by effective sensor data exploitation, because of the cognitive load an operator is exposed to, due to the large amount of data and time-dependency constraints. This paper addresses this challenge in remote-vehicle teleoperation by proposing an intuitive way to present sensor data to users by means of using mixed reality and visual aids within the user interface. We propose a method for organizing information presentation and a set of visual aids to facilitate visual communication of data in teleoperation control panels. The resulting sensor-information presentation appears coherent and intuitive, making it easier for an operator to catch and comprehend information meaning. This increases situational awareness and speeds up decision-making. Our method is implemented on a real mobile robotic system operating outdoor equipped with on-board internal and external sensors, GPS, and a reconstructed 3D graphical model provided by an assistant drone. Experimentation verified feasibility while intuitive and comprehensive visual communication was confirmed through a qualitative assessment, which encourages further developments.Peer reviewe

Impacto da conquista hispânica na humedal do Paraná Inferior (Argentina). Uma perspectiva histórica e genética mitocondrial

Para indagar sobre el impacto genético que habría generado la conquista hispánica en los grupos nativos asentados en el Paraná Medio e Inferior se analizaron muestras de individuos pre y posthispánicos de la región. Se identificaron los haplogrupos de ADN mitocondrial empelando Polimorfismos de Longitud de Fragmentos de Restricción (RFLP). Los datos obtenidos se compararon con los de otros sitios arqueológicos pre y posthispánicos y con muestras contemporáneas. Se observó mayor prevalencia del haplogrupo nativo B en las muestras posthispánicas, aunque sin diferenciación significativa con el grupo prehispánico de la región del Paraná Medio e Inferior. Ambos grupos presentan frecuencias de haplogrupos similares a muestras modernas provenientes del Gran Chaco y la provincia de Córdoba. Esto se corresponde con datos arqueológicos y de fuentes documentales de la reducción de Santiago del Baradero (provincia de Buenos Aires), con la prohibición de la salida de mujeres de la reducción y la escasez de individuos foráneos.In order to investigate the genetic impact that the Hispanic conquest would have generated in the native groups settled in the Middle and Lower Paraná, samples of pre and post-Hispanic individuals of this region were analyzed Mitochondrial DNA haplogroups were identified using Restriction Fragment Length Polymorphism (RFLP). The data were compared with those from other pre- and post-Hispanic archaeological sites and with contemporary samples. We observed a higher prevalence of native B haplogroup, in the post-Hispanic samples, without significant difference with the pre-hispanic group of the lower and middle Parana region. Both groups present similar haplogroup frequencies of those found in samples from Gran Chaco and the Córdoba province. This corresponds with archaeological data and the documentary sources about the Santiago del Baradero reduction (Buenos Aires province), with the prohibition of the departure of women from the reduction and the shortage of foreigners.Para investigar o impacto genético que a conquista hispânica teria gerado nos grupos nativos assentados no Médio e Baixo Paraná, amostras de indivíduos pré e pós-hispânicos da região foram analisadas. Os haplogrupos de DNA mitocondrial foram identificados usando Polimorfismos de Comprimento de Fragmento de Restrição (RFLP). Os dados obtidos foram comparados com os de outros sítios arqueológicos pré e pós-hispânicos e com amostras contemporâneas. Uma maior prevalência do haplogrupo B nativo foi observada nas amostras pós-hispânicas, embora sem diferenciação significativa em relação ao grupo pré-hispânico da região do Médio e Baixo Paraná. Ambos grupos apresentam freqüências semelhantes de haplogrupos que aquelas amostras modernas do Gran Chaco e da província de Córdoba. Isto se correlaciona con os dados arqueológicos y de fontes documentais sobre a redução em Santiago del Baradero (província de Buenos Aires), com a proibição de mulheres para sair da redução e a escassez de indivíduos estrangeiros

Salvage stereotactic body radiotherapy for isolated lymph node recurrent prostate cancer : single institution series of 94 consecutive patients and 124 lymph nodes

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