Browsing by Author "Ferreira, Tiago Miguel"
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- Analysis of the Out-Of-Plane Seismic Behavior of Unreinforced Masonry: A Literature ReviewPublication . Ferreira, Tiago Miguel; Costa, Alexandre A.; Costa, AníbalAlthough the issue of the out-of-plane response of unreinforced masonry structures under earthquake excitation is well known with consensus among the research community, this issue is simultaneously one of the more complex and most neglected areas on the seismic assessment of existing buildings. Nonetheless, its characterization should be found on the solid knowledge of the phenomenon and on the complete understanding of methodologies currently used to describe it. Based on this assumption, this article presents a general framework on the issue of the out-of-plane performance of unreinforced masonry structures, beginning with a brief introduction to the topic, followed by a compact state of art in which the principal methodologies proposed to assess the out-of-plane behavior of unreinforced masonry structures are presented. Different analytical approaches are presented, namely force and displacement-based, complemented with the presentation of existing numerical tools for the purpose presented above. Moreover, the most relevant experimental campaigns carried out in order to reproduce the phenomenon are reviewed and briefly discussed.
- Experimental characterization of the out-of-plane performance of regular stone masonry walls, including test setups and axial load influencePublication . Ferreira, Tiago Miguel; Costa, Alexandre A.; Arêde, António; Gomes, Ana; Costa, AníbalStone masonry is one of the oldest and most worldwide used building techniques. Nevertheless, the structural response of masonry structures is complex and the effective knowledge about their mechanical behaviour is still limited. This fact is particularly notorious when dealing with the description of their out-of-plane behaviour under horizontal loadings, as is the case of the earthquake action. In this context, this paper describes an experimental program, conducted in laboratory environment, aiming at characterizing the out-of-plane behaviour of traditional unreinforced stone masonry walls. In the scope of this campaign, six full-scale sacco stone masonry specimens were fully characterised regarding their most important mechanic, geometric and dynamic features and were tested resorting to two different loading techniques under three distinct vertical pre-compression states; three of the specimens were subjected to an out-of-plane surface load by means of a system of airbags and the remaining were subjected to an out-of-plane horizontal line-load at the top. From the experiments it was possible to observe that both test setups were able to globally mobilize the out-of-plane response of the walls, which presented substantial displacement capacity, with ratios of ultimate displacement to the wall thickness ranging between 26 and 45 %, as well as good energy dissipation capacity. Finally, very interesting results were also obtained from a simple analytical model used herein to compute a set of experimental-based ratios, namely between the maximum stability displacement and the wall thickness for which a mean value of about 60 % was found.
- In situ Out-of-Plane Cyclic Testing of Original and Strengthened Traditional Stone Masonry Walls Using AirbagsPublication . Ferreira, Tiago Miguel; Costa, Alexandre A.; Arêde, António; Varum, Humberto; Costa, AníbalThis article presents a field experimental campaign carried out on an existing one-story stone masonry building, aiming at characterizing the out-of-plane behavior of its walls. A bidirectional test set-up based on a self-equilibrated airbag system was developed and used on three similarmasonry walls under distinct conditions: original, retrofitted, and strengthened. The results obtained and the main advantages and shortcomings found in the test set-up are discussed. Finally, some of the most popular retrofitting and/or strengthening techniques applied during the 1998 Azores reconstruction process are critically analyzed, aiming at suggesting quantifications for future interventions on existing unreinforced masonry buildings.
- A simplified four-branch model for the analytical study of the out-of-plane performance of regular stone URM wallsPublication . Ferreira, Tiago Miguel; Costa, Alexandre A.; Vicente, Romeu; Varum, HumbertoDuring the last years, several studies have been made aiming to assess the out-of-plane seismic response of unreinforced stone masonry structures. This fact led to the development of a wide variety of models and approaches, ranging from simple kinematic based analytical models up to complex numerical simulations. Nevertheless, for the sake of simplicity, the out-of-plane seismic response of a masonry wall pier may be obtained by means of a simple single-degree-of-freedom system while still providing good results. In fact, despite the assumptions associated with such a simple formulation, it is also true that the epistemic uncertainty inherent with the selection of appropriate input parameters in more complex models may render them truly ineffective. In this framework, this paper focuses on the study of the out-of-plane bending of unreinforced stone masonry walls (cantilevers) by proposing a simplified analytical approach based on the construction of a linearized four-branch model, which is used to characterize the linear and nonlinear response of such structural elements through an overturning moment-rotation relationship. The formulation of the four-branch model is presented and described in detail and the meaningful parameters used for its construction are obtained from a set of experimental laboratory tests performed on six full-scale unreinforced regular sacco stone masonry specimens. Moreover, a parametric analysis aiming to evaluate the effect of these parameters’ variation on the final configuration of the model is presented and critically discussed. Finally, the results obtained from the application of the developed four-branch model on real unreinforced regular sacco stone masonry walls are thoroughly analysed and the main conclusions obtained from its application are summarized.