112,061 research outputs found
Homogenization of the heterogeneous beam dynamics: The influence of the random Young's modulus mixing law
No full textThis paper concerns the homogenization of the dynamic response of Euler Bernoulli's beam with random Young's modulus. Considering the eigenvalue problem, special attention is dedicated to the homogenization residuals (correctors) analysis, i.e. the difference between the random heterogeneous solution and the homogenized solution. Several correlation (mixing) laws of the Young's modulus are considered and a dimensionless characteristic scale length, based on the correlation length, is introduced. The effects of the mixing law on the residuals are analyzed using numerical approaches both for sampling the random Young’ modulus and for examining the beam eigenvalue problem. Two measurements are introduced to estimate the residuals between apparent and effective solution: the normalized difference of the Young's modulus and the normalized difference of the modes' shape. The effect of the mode's order is also highlighted with reference to forced vibrations
Il comportamento sismico del duomo di Parma
No full textLe recenti “Linee Guida per la valutazione e la riduzione del rischio sismico del patrimonio culturale” [1] indicano chiaramente come il comportamento sismico delle chiese e di tutte le strutture con grandi aule possa (o meglio debba) essere interpretato attraverso la loro scomposizione in porzioni architettoniche (macroelementi), caratterizzate da una risposta strutturale sostanzialmente autonoma rispetto alla chiesa nel suo complesso (facciata, aula, abside, campanile, cupola, arco trionfale, ecc.). L'identificazione di questi macroelementi è quindi un primo passo essenziale per valutare la sicurezza sismica di un monumento di questo tipo ed eventualmente progettare un intervento di consolidamento. I macroelementi devono essere individuati attraverso un apposito studio sulla storia sismica dell'edificio, che metta in evidenza i danni subiti in occasione dei principali terremoti e li metta in relazione ai meccanismi di danno.
Il presente lavoro presenta lo studio della storia sismica del Duomo di Parma [2], realizzato mediante la ricerca dei documenti di archivio, la lettura delle tracce lasciate direttamente sul monumento e l'analisi dei dati del sistema di monitoraggio strutturale automatico. Si è potuto così verificare che i meccanismi di danno cui questo edificio è più sensibile sono rimasti immutati nei secoli: le stesse arre interessate da crolli nel 1117, sono anche state soggette a piccoli spostamenti, rilevati dai fessurimetri, durante un recente lieve terremoto. Per ridurre il rischio sismico del monumento sarà quindi sufficiente inserire presìdi che impediscano l'innesco di questi meccanismi, nell'ottica della compatibilità e del minimo intervento
Effects of the thickness and angle of embrace uncertainties on the limit equilibrium of masonry arches under horizontal loads
No full textEstimation of masonry texture and mechanical characteristics by means of thermographic images
No full textDynamic response of masonry arch with geometrical irregularities subjected to a pulse-type ground motion
No full textAncient masonry structures often rely on the masonry arch as a load bearing element. The understanding of its response under seismic actions is a first fundamental step towards the comprehension of the behaviour of more complex structures. It is well known that the stability of masonry arches is primarily related to the geometry. The safety assessment under seismic actions is usually carried out by considering known deterministic geometrical parameters, such as thickness, rise and span, and the voussoirs are assumed with equal dimensions. However, many factors, like defects or irregularities in the shape of the voussoirs and imprecise construction, produce variations of the geometry with respect to the nominal one and, as a consequence, may effect the ability of the arch to resist seismic actions. In this paper, the effect of geometrical irregularities on the dynamic response of circular masonry arches is considered. Irregular geometries are obtained through a random generation of the key geometrical parameters, and the effect of these irregularities is quantified by analysing the dynamic response to ground motion. The masonry arch is modelled as a four-link mechanism, i.e. a system made of three rigid blocks hinged at their ends. The position of the hinges at the instant of activation of the motion is determined through limit analysis. Lagrange’s equations of motion have been written for the generated irregular geometries and solved through numerical integration. The results are summarised by a fragility surface that quantify the extent to which geometrical uncertainties can alter the dynamic response of the masonry arch and increase its seismic vulnerability
Riparazioni e trasformazioni di architetture danneggiate da terremoti in Sicilia e Calabria (1783-1908)
No full text
Estimation of residuals for the homogenized solution of quasi-periodic media
No full textIn this work we analyze the convergence of the elastic coefficients in terms of the residuals as the dimensions of the sample of a random two-dimensional medium vary. In particular, the case of the masonry material which can be considered a heterogeneous solid with two phases (stones or bricks and mortar) is taken into account. In particular, we consider a masonry which presents a quasi-periodic micro-structure. A procedure of numerical generation of wall portions has been developed which takes into account not only the scale ratio but also the mechanical ratio and the geometrical ratio. The convergence of residuals has been highlighted in terms of probability density function and statistical moments, up to the second order, of the stiffness coefficients and of the log-Euclidean distance between the masonry samples and the closest isotropic material
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