PSI - Issue 11

Sonia Boschi et al. / Procedia Structural Integrity 11 (2018) 169–176 Author name / Structural Integrity Procedia 00 (2018) 000–000

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in complex aggregates, being the result of an historic process of evolution and saturation of free spaces among existing structural units, often presenting different materials and construction techniques (Carocci and Tocci 2007, Bernardini et al. 2018). These structures are particularly susceptible to local or global collapses in case of seismic loading, due to their intrinsic vulnerability - absence of adequate connections between orthogonal walls, poor mechanical characteristics of the materials, signifi cant deterioration due to existing crack pattern or inappropriate maintenance - and their reciprocal interactions. Indeed, historic masonry buildings showed high damage levels during past and recent Italian earthquakes (D’Ayala and Paganoni 2011, Borri et al. 2017), once again evidencing the need of operational strategies for evaluating their seismic vulnerability and defining effective retrofitting techniques capable of increasing the safety level and preserving their historical identities and artistic values. For large-scale vulnerability assessment, expeditious methods make use of qualitative parameters (Lagomarsino 2006, Lourenço and Roque 2006, Boschi et al. 2017) to classify the buildings and defining ranks useful to identify the constructions more susceptible to damage and immediately in dire of retrofitting. However, it is still through detailed analyses and numerical accurate models that seismic upgrading interventions are commonly designed. Thanks to the high level of knowledge - geometrical, architectural, materical and structural - acquired through the in situ process of investigation, numerical models are implemented, keeping attention on the evaluation of both local and global collapse mechanisms of significant structural units (Roca et al. 2010, Lagomarsino and Cattari 2015, Betti et al. 2017 and Castori et al. 2017,to cite just a few), as suggested by the current Italian Building Code (M.I.T. 2008 and 2009) and the Guidelines of the Ministry for Cultural Heritage (D.P.C.M. 2011). In this framework, the paper discusses the seismic vulnerability of the masonry aggregate of Civitali Insitut, located in the city center of Lucca (Italy). A multidisciplinary procedure has been used: firstly, a careful and complete knowledge of the structure has been acquired, based also on partially destructive onsite tests of double flat jacks; then, the static and seismic assessment of the complex has been conducted by analyzing both local mechanisms and global behavior and assuming different structural configurations accordingly to what observed in the cognitive phase. Particular attention has been paid to the study of the vaults that cover the ground floor of the building, one of the most vulnerable structural elements in the construction. The results have highlighted some critical issues such as the weak connections of the wall and the poor quality of the masonry typology. The case study is a complex masonry building in aggregate that includes two high schools and a kindergarten and it is located in San Nicolao Street, in the city center of Lucca (Italy). The complex is the ex-monastery of San Nicolao Novello, with annexed San Nicolao Church. The aggregate fills an urban block (Fig. 1a). It dates back to 1330 and hosted the Augustinian nuns of Santa Maria della Croce. The buildings was rebuilt between the sixteenth and seventeenth centuries and, more recently, has undergone different architectonical and structural interventions giving it its actual configuration. The aggregate has a main body with an almost square plan, inscribed in a rectangle with dimensions of approximately 76×62 m and it has an internal cloister, with a square plan too, entering in a rectangle of indicative dimensions 38×34 m (Fig. 1b). On the East side, the main building is in continuity with two other structural bodies, of elongated rectangular shape that develop longitudinally along Via San Nicolao, Fig. 1c. In particular, the northern appendix is the Church of San Nicolao (30×14 m), while on the South side, there is an appendix of approximately 32×18 m. On the West side, there is an L-shaped one-level structure (12×10 m). The main body mostly develops on two levels above ground, while on the East side, along Via San Nicolao, it is constituted by three levels, as the South Appendix. The cloister develops for two levels as well as the Church. When a complex building have to be analysed, the results of numerical analyses of the global modelling of the structure may be unreliable, as the behaviour of each single structural units may be different from that of the whole building and therefore must be studied separately. The procedure used for this case study is based on a knowledge approach, in line with what already done by Lagomarsino et al. (2014) and Caprili et al. (2017) for the analysis of Podestà Palace and La Sapienza Palace in Pisa, respectively. A detailed knowledge process is conducted for the building complex, paying attention to its 2. Knowledge process of the building complex 2.1. The adopted procedure