1,720,998 research outputs found
Derivation, Validation, and Web Application of Dimensionless Analytical Solutions for Equivalent Period and Damping Ratio of Soil-Foundation-Structure Systems
No full textThe paper proposes closed-form solutions to estimate the period lengthening and the damping ratio of buildings considering the effects of the dynamic soil-foundation-structure interaction. They were derived by introducing analytical solutions of the impedance functions in the equation of the displacement of the so-called “replacement oscillator.” The obtained expressions depend on well-established and ad-hoc defined dimensionless parameters and are applicable to several configurations of subsoil and shallow foundations, even accounting for the cross-interaction among footings and the foundation flexibility. The proposed approach was successfully validated against well-known solutions available in literature and against the period and damping ratio experimentally measured on (1) the steel–concrete prototype Europroteas (Greece); and (2) masonry buildings founded on soft clay in the city of Matera (south of Italy). To promote their widespread application, the closed-form solutions were implemented into a web application 0D-In, exploited to execute a sensitivity analysis. The outcomes of this study highlighted that the period increases more significantly for structures founded on flexible or interacting foundations. The soil hysteretic contribution is maximum for rocking prone structures. For ordinary buildings, the radiative damping ratio prevails, due to the considerable length of rectangular footings. Again for ordinary buildings, the effect of the embedment appears of secondary importance both on the period lengthening and on the damping ratio
VALUTAZIONE PRELIMINARE DEGLI EFFETTI DELL'INTERAZIONE DINAMICA TERRENO-STRUTTURA SULLE TORRI MONUMENTALI
No full textA simplified approach to account for through-soil interaction between two adjacent shallow foundations
No full textNeighbouring buildings, even though disconnected from the structural viewpoint, may interact through the underlying soil especially when they are founded on very soft soils. Despite some pioneering studies since the early 1970’s, structure–soil–structure interaction has yet to be further investigated to reveal the effects that could be exerted on both the static and dynamic response of nearby structures. The present work aims at expanding the theoretical knowledge on this phenomenon through an extensive parametric study based on a truly 3D continuum approach solved through the Flac3D finite difference software. The impedance functions of two closely-spaced shallow foundations have been numerically calculated by varying the distance between the nearby footings and the subsoil configuration (homogeneous or layered). The numerical results have elucidated important effects of cross interaction between two neighbouring foundations. The static stiffness reduces, and this effect is increasingly significant as the foundations are closer whatever the subsoil conditions are. The dynamic coefficients increase with respect to those corresponding to the single footing over halfspace. Such effect is less important for the layer-over-halfspace soil configuration, for which the dynamic coefficients are mainly affected by the frequency response of the stratum. Finally, in the realm of the sub-structure approach, a novel simplified design approach, based on group factors for closely-spaced shallow foundations, was proposed to compute the soil-foundation impedance matrix englobing the foundation–foundation interaction in addition to the soil–foundation interaction
Time-dependent interaction coefficients to quantify the settlement of energy pile groups
No full textThe use of energy piles is facing an exponential growth due to the increasing need of exploiting sustainable energy sources.
Their design implies the estimation of the displacement induced by the combined thermo-mechanical interaction between
piles belonging to the same group. In this regard, the work at hand derives sets of interaction coefficients for piles subjected
to thermal load in not stationary conditions, using finite difference numerical analyses. These involved pile pairs embedded
in different soil types at multiple spacing, namely 2, 4, 6, 8, 10 times the pile diameter. A new dimensionless parameter is also
introduced to describe the evolution with time of the interaction coefficients accounting for pile-to-pile spacing, soil thermal
diffusivity, pile–soil stiffness ratio, and time. The numerical results demonstrate a strict time-dependence of the interaction
coefficients that is worthy to be considered in the design practice. To this aim, a practice-oriented approach is proposed allowing
to evaluate the interaction effects and thereby derive the settlement of each pile in a straightforward manner. This requires as
only ingredient the settlement of the isolated energy pile at the considered time instant. The simplified approach is successfully
validated against full 3D thermo-mechanical numerical analyses on pile groups including conventional and energy piles with
different layouts
PREDICTIONS ON THE SEISMIC RESPONSE OF MONUMENTAL TOWERS ON SOFT SOIL
No full textAfter the damages to the cultural heritage caused by the most recent earthquakes, the protection of ancient buildings is an urgent and relevant theme in Europe, especially in the Mediterranean countries, characterized by high seismic hazard. The fine tuning of the seismic protection requires analyses on refined models in order to catch the dynamic behaviour of the soil–foundation– structure system in a lifelike way. Neglecting soil structure interaction effects, in fact, may be conservative or not, depending on the structural pattern and the nature of the subsoil. Focusing on the historical towers, the most symbolic building among monuments, a method is here proposed for preliminary predictions on the variation of natural period and damping ratio due to the dynamic interaction between soil and structure. The simplified approach is then applied to three cases of monumental towers on soft soil, located in three European cities, characterized by high seismic hazard
Influenza delle caratteristiche di terreno e struttura sull' interazione in campo dinamico
No full textSoil-structure interaction effects on out-of-plane seismic response and damage of masonry buildings with shallow foundations
Full text linkA significant amount of damage and casualties induced by several strong-motion earthquakes which recently stroke South-East Mediterranean area is due to the major seismic vulnerability of residential buildings. In small villages and mid-size towns, those buildings very often consist of two- to four-story, unreinforced masonry (URM) structures not designed for earthquake resistance, with direct foundations usually corresponding to an in-depth extension of load-bearing walls. For such structures, especially when founded on soft soils, site amplification and soil-foundation-structure interaction (SFSI) can significantly affect the seismic performance; conversely, such phenomena should be investigated through methods that allow a trade-off between accuracy and computational effort, hence encouraging their implementation in engineering practice. This paper provides a comprehensive updated description of the studies carried out in the last years by the authors, which are based on both linear and nonlinear, parametric, dynamic analyses of complete soil-foundation-structure (SFS) models representative of existing residential building configurations on different soils. Specifically, the parametric study investigated SFS models with different masonry types, aspect ratios, and code-conforming homogeneous and heterogeneous soil profiles. The methodology and analysis results allowed for reaching the following objectives: (i) predicting the elongation of the fundamental period and the variation of equivalent damping of the SFS system with respect to fixed-base conditions, through a simplified approach based on an equivalent simple oscillator; and (ii) estimating the probability of exceeding increasing damage levels associated with out-of-plane overturning of URM walls, through fragility functions that take into account SFS interaction. The effectiveness of these simplified tools was successfully validated against well-documented case studies, at the scales of both single instrumented buildings and urban area
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
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