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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
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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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