Influence of the annex on seismic behavior of historic churches A. Dal Cin ⇑ , S. Russo IUAV University of Venice, Dept. of Design and Planning in Complex Environments, Dorsoduro 2206, 30123 Venice, Italy article info Article history: Received 21 January 2014 Received in revised form 3 July 2014 Accepted 6 July 2014 Available online 16 July 2014 Keywords: Historical church Annex Interface Damage identification Modal analysis abstract In May 2012, two major earthquakes occurred in Emilia Romagna region in Northern Italy, causing widespread damage. The hypocentre of the second one, strokes Mirandola where is located the Gesù Church investigated in this research. The church has a long and important annex to the south built during the same period of the church. This paper addresses how the important annex influenced the seismic response of this historical church and how, more generally, this kind of asymmetric mass can influence the behavior of historic churches. The final considerations are based on the comparison between the structural damage pattern survey and modal and seismic FE analysis. A FE model was constructed considering four different configurations: (i) isolated church, (ii) the church with the pres- ence of the real annex with a perfect connection, (iii) the church with the presence of the same annex but with an interface between the church and the annex and (iv) this last con- figuration with the stiffness degradation of the interface. Firstly the dynamic modal anal- ysis and subsequently the seismic spectral analysis were performed. The results indicate that the annex’s presences play a significant role in the dynamic response of the church and affect the distribution of damages for the whole building. The results of the seismic simulation are in agreement with the observed damage. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The recent earthquakes that hit Italy in the last century proved the high vulnerability of cultural heritage, with particular reference to churches. These particular monumental buildings cannot be reduced to any standard structural scheme and this makes it difficult to evaluate their seismic reliability. To overcome this problem, the macro-element approach has been pro- posed a few years ago and since then repeatedly used to recognizing the collapse mechanisms in the different macro- elements of the church [1,2]. The common collapsing configurations are shown in PCM-DPC-MiBAC M.-A.-D. [3]. The historical centers often occur as the result of an uncontrolled constructive evolution, whose complex configurations lead the structures to strongly interact with each other when are subjected to seismic action [4]. As a matter of fact, several historic churches are not isolated from the urban context but are often characterized by the presence of adjacent buildings, usually named annex (convents, sacristy, tower, minor constructions, etc.) at the same time of the church or subsequently constructed as we have seen in other case studies (Fig. 1). Besides the monitoring of historical constructions in seismic areas is a predominant issue also in Europe and especially in Italy because of the richness of its inestimable architectural heritage [5,6]. In the last century the seismic events stroked severely the cultural historic heritage and in particular the 49% of the damaged structures are churches highlighting their http://dx.doi.org/10.1016/j.engfailanal.2014.07.004 1350-6307/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: adalcin@iuav.it (A. Dal Cin), russo@iuav.it (S. Russo). Engineering Failure Analysis 45 (2014) 300–313 Contents lists available at ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal