Almost half of the housing buildings of Barcelona were built before 1940. In the Eixample district, approximately the 65% of the buildings fit the main features of a building design based on unreinforced masonry (URM) without any consideration of the seismic action. The buildings of the Eixample district are not isolated, quite the opposite, they are built as a part of a squared aggregate (113,3m per 113,3m) which includes approximately 22 buildings. Since 1960, the major part of the demolished URM buildings has been substituted by reinforced concrete (RC) buildings. As a consequence of this substitution, we expect a change in the seismic vulnerability of the buildings aggregate. In order to evaluate changes in the dynamic behavior of an aggregate, we performed different pushover analysis using the TreMuri software. A comparison of results corresponding to aggregates of URM-buildings and aggregates including RC-buildings is presented.