3,167 research outputs found
Seismic response of extended pile shafts considering nonlinear soil-pile interaction
No full textIl sistema pila-palo è largamente diffuso nelle strutture da ponte grazie ai suoi vantaggi
economici e tecnici. Tuttavia questo sistema è fortemente influenzato dagli effetti
dell’interazione dinamica terreno-palo-struttura. In aggiunta all’allungamento del periodo
fondamentale della struttura, la cedevolezza della fondazione induce una componente
rotazionale del moto sismico sul sistema globale che non può essere considerata mediante
le comuni procedure di progettazione sismica. Sebbene siano stati sviluppati modelli
avanzati per considerare l’interazione terreno-palo-struttura sia in campo lineare e non
lineare, i modelli alla Winkler rappresentano uno degli approcci più versatili.
In questo lavoro, un modello nonlineare di trave su suolo alla Winkler è stata utilizzato per
indagare l’effetto sulla risposta della struttura dei principali aspetti legati al comportamento
nonlineare del sistema terreno-fondazione, come ad esempio la plasticizzazione del terreno
, la formazione di distacco all’interfaccia palo-terreno, il collasso delle pareti del foro e il
degrado o incrudimento ciclico del terreno in prossimità del palo.
Sono state eseguite analisi dinamiche incrementali per valutare gli effetti della durata del
moto sismico e le non linearità del terreno sulle prestazioni della pila-palo in vari profili di
terreno omogeneo e bistrato sia di argilla satura che di sabbia nello stato asciutto o saturo
considerando differenti livelli di compattazione.
Si è stabilita una procedura per eseguire le analisi dinamiche incrementali considerando gli
effetti sia sulla risposta sismica locale sia sulle prestazioni strutturali. Gli effetti
dell’interazione cinematica ed inerziale in campo non lineare sono stati analizzati mediante
un’ampia indagine parametrica. Le analisi hanno evidenziato il ruolo determinante della
componente rotazionale e della durata del moto sismico sulla risposta sismica della pilapalo.
I risultati ottenuti sono inoltre stati confrontati con quelli ottenuti mediante un
modello lineare. Infine, vengono fatte alcune considerazioni evidenziando le aree grigie
della comune pratica di progettazione.Single column bents on extended pile shafts are widely used in bridges for their economical
and technical advantages. Nevertheless, this system is strongly affected by Dynamic Soil-
Pile-Structure Interaction. In addition to the lengthening of the fundamental period of the
structure, the compliance of the foundation induces a rocking component of the seismic
motion experienced by the overall system that cannot be considered by following the
procedures of a common seismic design practice. Although advanced models have been
developed in order to account for Soil-Pile-Structure Interaction both in the linear and
nonlinear range, Winkler-type models represent one of the most feasible approaches.
In this work, a Beam on Nonlinear Winkler Foundation model is used to investigate the
importance of features typical in soil nonlinear behaviour such as yielding, gapping, soil
cave-in and cyclic hardening/degradation effects on the performance of extended pile
shafts. A procedure to estimate the model parameters from geotechnical soil
characterization is presented.
Incremental Dynamic Analyses are performed to evaluate the effects of Ground Motion
Duration and soil nonlinearity on the performance of extended pile shafts in various
homogeneous and two-layered soil profiles, including saturated clay and sand in either fully
dry or saturated state with different levels of compaction. A procedure to perform
Incremental Dynamic Analysis, including effects on both site response analysis and on the
structural performance, is established. Nonlinear kinematic and inertial interaction effects
are analyzed by means of an exhaustive parametric investigation. The significant effects of
the rocking component and the Ground Motion Duration on the seismic response of
extended pile shafts are demonstrated. Comparisons with results obtained with a linear
model are also presented. Finally, some considerations are drawn pointing out grey areas of
the common design practice
Hybrid fuzzy – stochastic 1D site response analysis accounting for soil uncertainties
Full text linkThe analysis of the seismic site response is conventionally carried out by the study of the one-dimensional amplification of vertically propagating shear waves through a horizontal soil profile with equivalent-linear elastic properties. Site response analysis requires the specification of the input ground motion and the dynamic characterization of the soil deposit. Whilst the stochastic approach is commonly used to model seismic excitations, the use of probability density functions for describing the soil properties is consistent only when precise information based on a large amount of data from soil surveys are available. Conversely, a non-probabilistic approach based on fuzzy set theory would be more appropriate for dealing with uncertainties that are just expressed by vague, imprecise, qualitative, or incomplete information supplied by engineering judgment. In this paper, we address a hybrid fuzzy-stochastic 1D site response analysis approach: we consider probability models for the seismic input and fuzzy intervals for dealing with soil uncertainties; the problem boundary values are defined as convex normal fuzzy sets and described by means of membership functions. Zadeh’s extension principle, in combination with an efficient implementation of the Differential Evolution Algorithm for global minimization and maximization, is used to perform fuzzy computations. Results are presented as fuzzy median value of the largest peaks of the peak ground acceleration at the surface by considering four types of soil classified in accordance with the European seismic building code. Finally, elastic response spectra defined in terms of gradual functions are proposed in order to evaluate the influence of the soil uncertainties on the seismic response of structures
Describing objects using edge-pixel-feature descriptors
No full textDuring a description technique (100), a local descriptor for an object (300) is generated (122) by computing a 2-dimensional histogram (600) of pairs of angles (514, 516) between pairs of line segments (510, 512) that are aligned with edge pixels associated with the object (300). The pairs of line segments (510, 512) belong to a subset of k neighboring or proximate line segments (310). Moreover, this 2D histogram (600) may represent the relative displacement and the relative orientations of the pairs of line segments (510, 512) in the subset as weights in bins or cells defined by angular quantization values, and the 2D histogram (600 may exclude lengths of the line segments. Subsequently, the generated 2D histogram (600) may be compared (210) to predefined sets of descriptors in a model library that are associated with a set of objects, and the object may be identified (212) as one of the set of objects based on a group of match scores determined in the comparisons
A Fuzzy Logic Approach to Stochastic 1D Site Response Analysis accounting for Soil Uncertainties
Full text linkSite response analysis, namely the analysis of the wave propagation of shear waves through a soil deposit, requires the specification of the input ground motion and the dynamic characterization of the soil deposit. While the stochastic approach is commonly used for modelling seismic excitation, the use of probability density functions for describing the soil properties is consistent only when precise informations based on a large amount of data from soil surveys are available. Conversely, a non-probabilistic approach based on fuzzy set theory would be more appropriate for dealing with uncertainties that are just expressed by vague, imprecise, qualitative, or incomplete information and supplied by engineering judgement. In this paper, a hybrid fuzzy-stochastic 1D site response analysis approach for dealing with soil uncertainties defined as convex normal fuzzy sets is addressed. Zadeh's extension principle, in combination with an efficient implementation of the Differential Evolution Algorithm is used for global minimization and maximization. Results are presented as fuzzy median value ofthe largest peaks of the peak ground acceleration at the surface by considering four types of soil classified in accordance with the European seismic building code
A imagem de Alessandro Baricco no Brasil
Full text linkDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2013.Com a intenção de delinear o modo pelo qual o escritor italiano Alessandro Baricco se inseriu no sistema literário brasileiro e os caminhos percorridos pelos seus livros traduzidos, esta dissertação dá voz às experiências tradutórias de seus tradutores. A inserção de Bariccono Brasil tem seu início em 1997, através de uma proposição da Profa. Dra. Roberta Barni à editora Iluminuras da tradução de Oceano Mare. A partir daí, outras sete obras foram publicadas no Brasil, sendo três delas traduzidas por Roberta Barni e as outras quatro por quatro tradutores diferentes. De um lado, considera-se o tradutor como figura principal namediação entre culturas, e, de outro, se analisa a realidade desta figuradentro do sistema literário, sua invisibilidade, seus limites e o exercíciode sua profissão. A pesquisa conta, ainda, com críticas e resenhas referentes ao autor italiano publicadas em jornais consagrados no Brasil, considerando estas como parte constituinte da imagem de Baricco refletida em território nacional. Abstract : Intending to delineate the way the Italian writer Alessandro Baricco has been inserted in the Brazilian literary system and the paths his translated books have followed, this thesis gives voice to the translating experiences of his translators. Baricco's insertion in Brazil began in 1997, through a personal project of Dr. Roberta Barni, with her translation of Oceano Mare. Since then, seven other of his works have been published in Brazil, three of which were translated by Roberta Barni and the other four by four different translators. On the one hand,the translator is considered as the main figure in mediation betweencultures and, on the other, this figure's reality is analyzed within theliterary system: its invisibility, its limits and its professional practice. Criticisms and reviews of this Italian author published in well established Brazilian newspapers are also considered, with the understanding that they are part of Baricco's image reflected here
Soil-structure interaction in the seismic response of an isolated three span motorway overcrossing founded on piles
Full text linkThe effects of soil-structure interaction on the seismic response of an isolated three span motorway overcrossing founded on piles are investigated by considering a real bridge located along the A14 Motorway in central Italy. The dynamic and mechanical properties of the soils are obtained from a comprehensive geotechnical characterization of the sites. Ten triplets of real accelerograms, defined at the outcropping bedrock, are adopted and processed by local response analyses to capture the site amplification effects and the free-field motions within the deposits. The soil-structure interaction
effects are evaluated by means of the substructure method by comparing the seismic response of the structures with those obtained from conventional fixed base models. Analyses demonstrate that the soil-foundation dynamic compliance as well as the energy loss due to radiation damping dot not modify significantly the overall behaviour of the isolated bridges, while soil-structure interaction may increase deformations and forces on the isolation devices with respect to those obtained with fixed base models
Rheological effects related to neo-fracturing processes in rock masses
Full text linkRockfall hazard is one of the main natural hazards in mountainous areas and along transportation routes. Roads and railways interruptions, as well as damages of buildings, are among the main inconveniences due to the detachment of unstable sectors of highly jointed rock masses. Rockfalls are the result of the combined action of the rock mass creep and of the natural and anthropic solicitations, which lead to the accumulation of inelastic strain within the rock mass and to the formation of new fractures or to the extension and movement of the pre-existing ones (rock mass damaging phenomena). The understanding of rock damaging processes through the microseismic monitoring of rock slopes predisposed for instabilities events can help in defining proper risk mitigation strategies. With the aim of assessing rock mass damaging phenomena, this PhD thesis proposes an analysis of the damping ratio associated with the microseismic emissions recorded in two test sites located in central Italy. Three monitoring campaigns have been conducted: two at the Acuto quarry test site, where the vibrational behaviour of a 12 m3 rock block partially detached from the back rock wall has been investigated; one at the Terni-Giuncano railway test site, where a rock mass close to a railway was studied to analyse the effects produced by the repeated trains transit. A STA/LTA event detection algorithm has been implemented for the recognition of the microseismic emissions from the seismic datasets acquired in continuous mode and with a sampling frequency of 2400 Hz. The damping ratio of the microseismic emissions, filtered in monofrequential waveforms, was evaluated; in the following, the daily mean damping values for each frequency were compared in respect to the environmental parameters monitored on site. No irreversible trend variations were observed, but significant variations related to transient processes were detected. It is deemed that the proposed approach can be applied on yearly seismic dataset and environments exposed to natural and anthropic forcing actions, to be furtherly tested and validated. Additional analyses were carried out on the train transit recordings. Each train passage was analysed in terms of: a) RMS value of the recording; b) cross-correlation between couples of sensors. The observation of the RMS and cross-correlation time series over time confirmed the unvaried long-term vibrational behaviour of the rock mass, according to the results of the damping analysis. In addition, the seismic noise was investigated by computing the average noise in one-minute intervals filtered at specific frequency bands. The cumulative of the filtered intervals allowed to determine the main energised frequency band, which resulted to be the one comprised between 500 and 1000 Hz. The derivative of the averaged noise was compared with the environmental parameters recorded in the two test sites. A marked correlation between the variation of air and rock mass temperature and the derivative of the noise in the frequency band comprised between 0.5 and 30 Hz was noted, while the correlation is feeble or lost for the other frequency bands considered. The correlation observed between thermal cycles and ambient noise variations is in agreement with previous bibliographical studies; moreover, a differentiation in the vibrational response for the different frequency bands has been detected
La maturità di Alessandro Fei del Barbiere, in bilico tra Maniera e Riforma
No full textThis article studies the mature career of the Florentine painter Alessandro Fei del Barbiere (1537-1592), beginning with the rediscovery of the 'Ascension' altarpiece formerly in the Albizi Chapel in the destroyed church of San Pier Maggiore, Florence. Studying this painting and others recorded in 1584 by the biographer Raffaello Borghini, such as the two altarpieces for Santa Maria delle Grazie and the Madonna dell'Umiltà in Pistoia, the author reconstructs a body of works showing how in the 1580s Fei gradually went beyond the archaic style of his apprenticeship - he had been trained by Ridolfo del Ghirlandaio and Pierfrancesco Foschi, but was also marked by the Maniera of Vasari - evolving towards naturalism in both mimesis and pictorial handling. In Florence, his development partly parallels that of Santi di Tito and his circle, but Fei was also influenced by a probable sojourn during the early part of that decade in Rome, where he could have been inspired by Girolamo Muziano and the painters working for Pope Gregory XIII. Among other proposals, the author suggests that the artist was responsible for decorating the chancel of Fiesole Cathedral (c. 1584-1589), which consisted of an altarpiece, only rarely discussed by scholars, and a cycle of frescoes hitherto attributed to Nicodemo Ferrucci
Query-guided networks for few-shot fine-grained classification and person search
No full textFew-shot fine-grained classification and person search appear as distinct tasks and literature has treated them separately. But a closer look unveils important similarities: both tasks target categories that can only be discriminated by specific object details; and the relevant models should generalize to new categories, not seen during training. We propose a novel unified Query-Guided Network (QGN) applicable to both tasks. QGN consists of a Query-guided Siamese-Squeeze-and-Excitation subnetwork which re-weights both the query and gallery features across all network layers, a Query-guided Region Proposal subnetwork for query-specific localisation, and a Query-guided Similarity subnetwork for metric learning. QGN improves on a few recent few-shot fine-grained datasets, outperforming other techniques on CUB by a large margin. QGN also performs competitively on the person search CUHK-SYSU and PRW datasets, where we perform in-depth analysis
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