Prior in-plane damage on the out-of-plane response of masonry infills

Although the masonry infills are assumed as non-structural elements, their vulnerability during past earthquakes resulted in huge economical costs and life losses. The out-of-plane collapse of the infills is assumed as a common collapse mechanism. One important parameter on the out-of-plane collapse of the infills, is a presence of prior in-plane damage which in the present paper will be studied in detail. In this scope, the main objective of this study is to analyze the out-of-plane experimental behavior of masonry infilled frames that are characteristic of Portuguese buildings and can be seen in other south European countries. In the experimental program, four half-scale specimens were constructed; one reference specimen and three specimens with different prior inplane damage related to the in-plane drifts of 0.3%, 0.5% and 1%. The out-of-plane loading was applied uniformly to the brick infills by means of an airbag to simulate the effect of earthquakes. The results show that presence of prior in-plane damage affects the out-of-plane response of the specimens and a formula was derived to predict the out-of-plane stiffness and resistance of the infills taking into account the effects of prior in-plane damage

Seismic performance of Portuguese masonry infill walls: From traditional systems to new solutions

The use of masonry infill walls in reinforced concrete structures are a common solution in Portugal and other European countries for more than 50 years. These walls are used as exterior enclosures to build the envelope of the buildings, or as interior partitions to divide the different spaces of the houses. In the building construction practice these walls are built only after the hardening of the reinforced concrete elements. For that reason, they are assumed as non-structural elements, and not considered in the structural design of the building. However, when buildings are subjected to seismic action, these walls assume a structural behavior. This leads in many cases to the existence of an unsatisfactory behavior of infill walls, resulting in damage of the walls, which put human lives in dangerous and cause extensive economic losses. This seismic vulnerability of masonry infill walls is well recognized by the scientific community and has been observed in many works carried out in the last decades, as well as the recent earthquakes in southern Europe. In the case of a seismic event of high intensity in Portugal, it is expected that similar problems will occur in the Portuguese masonry infill walls, given the similarity of the construction typologies, in southern Europe. It is therefore important to study the masonry infill walls used in Portugal over the years, to fully understand their seismic behavior, and thus be able to propose and study reinforcement systems for existing walls and new masonry infill systems for new construction. Thus, in this paper is made a characterization of masonry infill walls typologies used in Portugal over the years. A review of the mechanical behavior of masonry infill walls is carried out using several In-Plane and Out-of-Plane tests performed at the University of Minho and other studies carried out in Portugal. Several strengthening techniques possible to be used in this type of walls are presented, as well as some mechanical characterization tests of these strengthening solutions applied on Portuguese infills walls. Finally, are presented two proposals for new systems of masonry infill walls to be used in new construction, with the objective of present a better seismic behavior in this type of elementsEuropean Union’s Seventh Framework Program for research, technological development and demonstration under grant agreement No 606229, which support this work. This work was also supported by FCT (Portuguese Foundation for Science and Technology, within ISISE, project UID/ECI/04029/2013, and through a doctoral scholarship reference SFRH/BD/125094/201