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This paper summarizes a study whose primary objectives were to develop a model for nonlinear static analysis of unreinforced masonry (URM) buildings, considering the flexibility of the floor system and analyzing the influence of stiffening the floor system on the overall seismic response of such buildings. With this aim, a six-story building typical of the Eixample-Barcelona district was used as a case study. All the macro-elements, those that constitute the walls and the floor system, were developed with one-dimensional spring elements. The influence of stiffening the floor system was analyzed by applying conventional stiffening interventions to the two-floor systems common in the Eixample-Barcelona district. The overall seismic response was evaluated in terms of modal parameters, the characteristics of the pushover curves and the deformed shape of the floors. The outcomes are discussed in relation to recent studies and explained in the context of previous studies. Finally, in the two unstiffened cases of the prototype building, the stiffening of the floor system slightly increases in fundamental periods, slightly to moderately increases in base shear capacities, and significantly decreases in displacement capacities. [ABSTRACT FROM AUTHOR]

Most of buildings and structures are usually projected according to two main axes. However, the geographical position of these buildings varies randomly. Such random distributions of the azimuthal positions of structures, in most of the cities, generally, are not accounted for when assessing their seismic risk; certainly, the direction of the seismic loads is another highly random variable. Moreover, an additional important source of uncertainty is related to the structural response, mainly due to the random character of the mechanical properties. There is a consensus that uncertainties must be considered for adequately assessing the seismic risk of structures, but these directionality effects have not been deeply explored so far. In this article, the influence of the high uncertainty involved in these input variables on the expected seismic damage is analysed. Thus, an actual earthquake, which affected the southern part of Spain, is studied. Notably, damages on a group of affected buildings, located close to the epicentre, are analysed and discussed in detail. The results show that the influence of the random azimuthal position of structures is an important source of uncertainty and that it should be taken into account when estimating the expected seismic risk in urban areas. [ABSTRACT FROM AUTHOR]