HISTORIC MILITARY ARCHITECTURES IN THE PROVINCE OF MANTUA: THE EFFECTS OF THE 2012 EARTHQUAKES

The research concerns the evaluation of the structural performance of the defence heritage in the Mantua area after the seismic sequence of May 20 and 29, 2012. The earthquake highlighted the high vulnerability of this heritage in the neighbouring Emilia-Romagna region where several brittle collapses of towers and fortification walls occurred. Over the centuries, the area was military strategic due to the complex hydrologic configuration be-tween the rivers Po, Mincio, Secchia and several artificial canals and ditches, so that since Middle Ages, the fixed courses were fortified by an imposing net of defensive structures. Nev-ertheless, the changes of the political equilibrium and configuration of Italy over time, led to the progressive loss of importance of those defensive structures till their almost complete dismantling during the Austrian dominion. Most of the building materials were reused in new hydraulic structures. The survived structures, mostly donjons, were transformed over time in civic towers or in public buildings, such as town halls or museums. Despite collapses did not occur, several recursive damages were documented after the 2012 earthquakes: especially cracks located in the supported top structures as well as in the upper part and in the main body of the towers, due to in plane and out plane seismic actions. The masonry discontinuities due to the building evolution and the lack of structural connection between the load bearing walls increased the vulnerability. At present, progressive interventions are planned according to the preservation of historic architecture; the design has to be based on the deep knowledge of the building, including features, materials properties, structural layout, building technique, damages. In this context, the Municipality of Mantua planned interesting activities of control of the main towers. The paper explores the recursive damages, the present situation and fu-ture intervention strategies for an important architectural heritage.