Abstract
This paper deals with the force-based assessment of collapse mechanisms and strengthening interventions of the historic masonry castle “Bussi sul Tirino” (Abruzzi, Italy) using rigid block limit analysis (RBLA). The structure, which is a fortified palace dating back to the 11th century, has experienced severe earthquakes over the centuries and was hit once again in 2009 by the L’Aquila earthquake. Based on the historical analysis and the results of in situ investigations, a spatial rigid block model of an entire structural unit was generated using the in-house software LiABlock_3D. The software is a MATLAB® based tool for three-dimensional RBLA, which provides as outputs collapse failure modes and collapse load multipliers. In addition, a specific routine was developed for the purpose of the study to compute the participating mass ratio and the spectral acceleration that activated the failure mechanisms. The results of the numerical analysis were used to address three different retrofitting interventions, based on the use of connection elements and ties that, according to the minimum intervention principle, progressively enhanced the seismic capacity. Comparisons in terms of seismic safety indices are finally provided in order to give a quantitative measure of the effectiveness of the adopted retrofitting strategies.
Highlights
Is the country with the highest number of cultural heritage structures in the world
Among the different methods and modeling approaches for the assessment of historic constructions subjected to seismic actions [15,16,17,18,19,20,21,22,23,24,25,26,27], this study focused on force-based assessment (FBA) and computational rigid block limit analysis (RBLA) [28,29,30,31,32]
In order to provide a reliable characterization of the main structural features of the castle, the information gained from the historical analysis about the construction material and techniques was integrated with the findings of focused visual inspections and non-destructive tests
Summary
Is the country with the highest number of cultural heritage structures in the world. It is worth noting that the major advantages of the proposed approach and software code compared are (i) the use of few input data to build the numerical model—essentially related to the geometry of the construction and few properties of the material; (ii) the possibility of reproducing specific features of the construction, as for any kind of discrete model, e.g., the bonding condition of orthogonal walls, the recesses in the walls, and others; (iii) the automatic detection of collapse mechanisms that are not defined a priori, but rather are the results of numerical analysis; (iv) the possibility of identifying very complex mechanisms, which simultaneously may involve in-plane and out-of-plane collapses, triggering the failure of large parts of the construction; (v) the computational efficiency of the software that, to similar rigid-block-based models, has a low computational demand, which is recognized to be the main limitation for the large-scale employment of RBLA [22].
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