High-rise unreinforced masonry buildings: influence of the floor system on the global seismic response

The studies about the effects of the flexibility of the floor diaphragm on the seismic behavior of unreinforced masonry buildings (URM-buildings) have focused on low-rise buildings. It should be borne in mind, however, that high-rise residential buildings have become the most mainstream housing pattern in European cities. Generally, the plan of this type of buildings is stretched and exhibits a high degree of symmetry. In this context, this paper summarizes a study whose primary objectives were: 1) develop a model for nonlinear static analysis of high-rise URM-buildings considering the flexibility of the floor system, and 2) analyze the influence of the stiffening of the floor system on the global seismic response of such buildings. To this aim, a six-story building with a composite floor of iron beams and brick vaults (IBBV-floor), typical of the Eixample-Barcelona district (prototype-building), was adopted as a case study. The floor system was modeled as aggregation of diaphragm macro-elements. All macro-elements, those that constitute the walls as well as the floor system, were developed with spring-elements. The construction of the model followed a strategy of modeling and validation by stages, from the 2D equivalent frame model until the integral model of the prototype-building. The analysis of the influence of the stiffening of the floor system was based on the application of conventional stiffening methods on the IBBV-floor. On the basis of a sensitivity analysis, the study focused on three cases: 1) unstiffened original variant, 2) a selected stiffened variant, and 3) variant with rigid floor. The global seismic response was evaluated in terms of characteristics of pushover curves and the displaced configuration of the floors. The stiffening of the floor system induces on the prototype-building slight increases in the fundamental periods, slight to moderate increases in the base shear capacities and significant decreases in the displacement capacities. Finally, these outcomes are discussed and located in the context of the most recent works.This research has been partially funded by the Ministry of Economy and Competitiveness (Ministerio de Economía y Competitividad-MINECO) of the Spanish Government and by the European Regional Development Fund (Fondo Europeo de Desarrollo Regional-FEDER) of the European Union (UE) through projects referenced as: CGL2011-23621 and CGL2015-65913-P (MINECO/FEDER, UE). Mr. Juan Jiménez Pacheco, sponsored by the University of Cuenca, obtained a scholarship from the Ministry of Higher Education, Science and Technology, SENESCYT, Government of Ecuador, for doctoral studies in the Earthquake Engineering program of the UPC-Barcelona Tech.Postprint (published version