Issue 45

F. Brandão et alii, Frattura ed Integrità Strutturale, 45 (2018) 14-32; DOI: 10.3221/IGF-ESIS.45.02 16 za, the capital city, and, since 2008, an intense seismic activity has been observed in Sobral region where, according to [21], at 05/21/2008 an earthquake of 4.2 m b magnitude was registered. The city of Sobral preserves a large number of heritage constructions in its historic center, which is one of the biggest and most important of Brazil with more than 1,200 build- ings listed by the National Historic and Artistic Heritage Institute (IPHAN). Thus, aiming to contribute to preservation and safety of Sobral heritage constructions under seismic actions, this paper presents a seismic behavior assessment of a very important heritage construction from Sobral historic center, namely Nossa Senhora das Dores Church, a structure dating back the beginning of the 19 th century, built in solid bricks masonry and located near Acaraú River. In a first part of the paper, few remarks about the Brazilian seismicity and the geometric and constructive features of the Nossa Senhora das Dores Church are reported. Subsequently, the FE model of the church and the numerical linear time-history analyses performed employing two real earthquakes are discussed. The analyses were developed assuming the masonry mechanical behavior as a linear one; this means that the results herein described do not account for the cracking and the crushing phenomena that may be activated during the seismic event. A more refined analysis should be made taking into account the non-linear behavior of masonry, after a refined experimental investigation aimed at evaluating the material properties needed to implement the non-linear material laws [22, 23]. The seismic analysis herein reported was hence aimed at a pre- liminary evaluation of the potential effects induced by seismic loading, assessing the structural elements that require a de- tailed and specific investigation. THE B RAZILIAN SEISMICITY : REGIONAL AND NORMATIVE ASPECTS map of the South America seismic hazard, produced by United States Geological Survey (USGS), is shown in Fig. 1.(a): Peak Ground Accelerations (PGA) are reported both in m/s 2 and as a fraction of g (the acceleration due to gravity) with a 10% probability of being exceeded in 50 years [24]. This figure shows that there is a large part of Brazil where there is not seismic activity or it is practically null (white area), however, in the northeast region of the country is possible to observe a small area seismically active, more precisely, the area between the states of Ceará, Rio Grande do Norte and Paraiba, that have considerable values of PGA, ranging between 0.02 g and 0.25 g . Fig. 1.(b) shows the Brazilian seismic catalog which, according to [19] indicates all the earthquakes already cataloged in the country from 1720 to 2016. The map includes ancient and recent earthquakes, and only superficial earthquakes are shown (i.e. depth <50 km). The blue circles are epicentres of historical earthquakes with magnitude estimated from the macrosimic effects. The red circles are epicentres of earthquakes recorded by seismographic stations. The empty circles - in the Andes - are epicentres of earthquakes in which the seismic waves have caused the oscillation of tall buildings in some Brazilian cities. Fig. 1 confirms that the northern part of the Ceará State, where the city of Sobral is located, has been affected by an intense seismic activity. Figure 1 : Brazilian seismicity: (a) map of the seismicity of South America [24] and (b) Brazilian Seismic Catalog [19]. As reported above, the city of Sobral is located in the north region of the Ceará State, and the Ceará State is located in the northeast region of Brazil. Sobral City is 230 km away from the capital city, Fortaleza. The Ceará State is located in a seis- A (a) (b)