1,720,998 research outputs found
Effects of the thickness and angle of embrace uncertainties on the limit equilibrium of masonry arches under horizontal loads
No full textConfined vs. unreinforced masonry: Construction and shaking table tests of two-storey buildings
No full textConfined masonry (CM) is a simple, convenient and effective building construction technology in seismic areas. Although a large background of experimental testing aimed to study the behavior of CM walls to vertical and in-plane lateral loads is available in literature, only a few experimental studies about the CM buildings behavior to seismic loads have been carried out. In this work, the results of a series of shaking-table tests carried out on two-storey unreinforced (URM) and confined masonry (CM) buildings are presented. Two structural systems with the same geometry were built and tested on a shaking table, in order to compare the dynamic response of the two different construction systems. The structures were subjected to seismic accelerations of increasing intensity yielding performance states ranging from minor damage to near collapse. The paper describes both the dynamic response using intensity measures, drift and acceleration profiles, and the observed damage evolution. The obtained results highlight the better performance of CM vs URM to withstand dynamic loads and provide crucial information to be used for numerical models calibration and response estimation
An integrated approach for the numerical modeling of severely damaged historic structures: Application to a masonry bridge
No full textThis paper presents an integrated approach that combines advanced survey procedures, such as close range photogrammetry based on high resolution images provided by Unmanned Aerial Vehicles, and Ambient Vibration Tests to develop accurate Finite Element models of severely damaged historic masonry structures. The proposed methodology is applied to a masonry arch bridge located in Todi, Central Italy, characterized by severe damage conditions involving diffuse material degradation and structural damages. Two numerical models are developed starting from the digital geometric survey: the first accurately describes the irregular actual geometry due to damage; the second regularizes the boundary surfaces as standard procedure in common practice when detailed survey is not available. The crucial role of the geometric irregularities given by the severe damage state on the dynamic properties of the masonry bridge is demonstrated by comparing the modal parameters of the two models. Furthermore, sensitivity analysis is carried out in order to assess the combined effect of different mechanical characteristics and geometric configurations on the modal properties and to select suitable updating parameters. The overall methodology is completed by a final model updating procedure targeting the experimental modal parameters estimated from Ambient Vibration Tests
The Effect of the Associative Friction in the Seismic Limit Analysis of Masonry Arches with Uncertain Geometry
No full textCharacterization of elastic properties of masonry through digital imaging techniques applied to thermographic images
No full textFragility analysis of masonry arch with geometrical uncertainties under sine pulse base motion
No full textIn this paper, the dynamic response of circular masonry arch subjected to a sine pulse ground motion is analysed, taking into account geometrical uncertainties related to shape defects. In order to generate the irregular geometry of the arch, the main geometrical parameters, i.e.The radius, the angle of embrace of the voussoirs and the thickness, are considered as random variables with uniform probability density functions. The dynamic analysis is performed by referring to an equivalent SDOF system made of three blocks hinged at their ends, whose equation of motion is derived from Lagrange's equations. Incremental Dynamic Analyses are carried out considering the arch with nominal geometry or geometrical uncertainties. The results are showed by means of a fragility curve, which attempts to quantify to what extent geometrical uncertainties modify the failure of the arch under sine pulse base motion
Effect of shape uncertainties on the collapse condition of the circular masonry arch
No full textHeritage buildings, worldwide, are marked by the presence of masonry structural elements often affected by shape irregularities if compared with their initial condition. The trigger factors of such geometrical uncertainties can be ascribed to the over centuries deformation processes, to environmental factors or upstream to the constructive methods. The aim of the present paper is the evaluation of the influence of shape irregularities on the collapse condition of circular masonry arches in presence of horizontal seismic actions. In order to take into account a more reliable estimation of the arches bearing capacity a random generative model is developed considering shape uncertainties. A limit analysis based procedure, referring to Heyman’s theory, is used in order to evaluate the horizontal loads multiplier. Then the collapse condition is studied through a probabilistic approach, by analysing the statistical moments up to second order of the results obtained by a Monte Carlo simulation
La ricostruzione delle crociere della sala colonnare del castello Maniace di Siracusa dopo il terremoto del 1693
No full textCostruito nella prima metà del XIII secolo per conto dell’imperatore Federico II, il castello Maniace di Siracusa concentra il suo enigma nella vasta sala colonnare (che era composta da venticinque crociere quadrate) e nei criteri costruttivi adottati per la sua realizzazione. Recenti ricerche sul campo e un’attenta rilettura documentaria del “progetto di restauro” post terremoto del 1693 hanno offerto nuovi strumenti utili a comprendere specifiche tecniche e procedure esecutive dell’intero organismo. Si è potuto così dimostrare che la differenza materica delle coperture (pietra calcarea bianca e lavica) è, in realtà, prodotto degli interventi di ricostruzione.
Il nodo costruttivo, che la storiografia ha considerato scontato, appare oggi determinante: le testimonianze documentali dei restauri del dopo terremoto messe a confronto con i materiali riscontrati in situ, offrono chiavi interpretative per decodificare genesi e procedure della grande struttura realizzata cinque secoli prima, poiché permaneva una continuità nel bagaglio di conoscenze empiriche e forse anche nella nomenclatura tecnica tramandatasi fino alle maestranze settecentesche.
Si propone di offrire pertanto una risposta su come e con quali accorgimenti sia stata costruita la sala ipostila siracusana e sui criteri adottati nei “restauri”. Ulteriori ragionamenti si possono sviluppare in relazione a singoli aspetti costruttivi - come la conformazione del tas-de-charge o il tipo e la funzione di archi e costoloni - che risultano testimonianze utili per ricostruire il quadro delle relazioni e dei rapporti che l’architettura federiciana manifesta con il mondo mediterraneo e con il gotico francese
Dynamic monitoring and nonlinear analysis of the dome of the basilica of S.Maria degli Angeli in Assisi
No full textDuring the last years, the application of Structural Health Monitoring (SHM) systems to heritage constructions has received a great interest due to the low invasiveness and low-cost of the necessary equipment. When applied to monumental structures and, more in general, to cultural heritage ones, such SHM systems represent an effective solution for preventive conservation against both material degradation and damages derived by natural hazards, such as earthquakes. Among the various technical solutions currently available for SHM, vibration-based systems deserve a special attention, but their application in the context of historical constructions is still quite rare and challenging, with very few documented applications, mostly limiting to masonry towers and bell-towers for their slenderness properties. In this work, the first months of continuous vibration monitoring of the dome of the Basilica of Santa Maria degli Angeli in Assisi are presented. At first, a dynamic identification has been carried out using five high-sensitivity accelerometers, three of them installed at the base of the drum and two at the base of the dome. Then, a fully automated identification technique has been used to extract time series of natural frequencies during the monitoring period. Moreover, some statistical tools have been applied in order to select the best configuration, in terms of number and position of sensors, necessary to obtain a continuous frequency tracking of the first natural modes in view of the use of this information for rapid post-earthquake structural assessment. Moreover, a preliminary investigation about the seismic assessment has been carried by means of a Finite Element (FE) nonlinear dynamic analysis. The damage map obtained by the numerical simulation has been compared with the actual crack scenario present on the structure, giving further information about the structural dynamic response
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