PSI - Issue 28

M.L. Puppio et al. / Procedia Structural Integrity 28 (2020) 330–343 Puppio M.L. et al/ Structural Integrity Procedia 00 (2020) 000–000

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1. Introduction Recent failures occurred in the last years recalled expertise attention on the collapse of historical urban walls. The general way to analyse the static and dynamic behavior of historic walls are the kinematic and rocking approaches [1][2][3]. In the last ten years, several failures of historical city walls occurred in Tuscany (Italy) as summarized in Fig.1 and Tab.1. The lessons from these failures are that the common triggering cause is a rainfall event, sharpened by the presence of moisture due to water leaks from sewers, as well as poor maintenance and absence of monitoring programs. The effect of climate events like rainfalls is well known in the scientific community, professional and political contexts [4]. The current technical codes, like Eurocodes, provide adequate indication for the natural actions induced by wind, earthquakes, temperature etc.; although the presence of moisture in terms of weakening of masonry structures is still not well treated. Historical urban walls are infrastructures frequently found in Europe and mainly in Italy: they essentially are the external perimeter of many city centers. They were constructed with both commercial and military functions. Moreover, they ensure the structural role of retaining walls supporting the soil against excessive slope. It is recurrent to have an articulate planimetric path in addition to a considerable altimetric complexity, due to the progressive modification of the city centers. The need of a systematic and quick procedure of survey and analysis is of primary importance. The proposed method is tested on the case of the historical urban walls of Volterra (Italy).

Fig. 1. Failure cases in Tuscany in the period 2011-2020.