The 14 th World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China EXPERIMENTAL INVESTIGATION ON THE BEHAVIOR OF SPANDRELS IN ANCIENT MASONRY BUILDINGS N. Gattesco 1 , I. Clemente 2 , L. Macorini 3 and S. Noè 4 1 Associate professor, Dept. of Architectural and Urban Design, University of Trieste. Italy 2 Research fellow Dept. of Civil and Environmental Engineering, University of Trieste. Italy 3 Research fellow Dept. of Civil and Environmental Engineering, University of Trieste. Italy Email: macorini@dica.units.it 4 Associate professor, Dept. of Civil and Environmental Engineering, University of Trieste. Italy ABSTRACT : The paper presents the main outcomes of experimental tests carried out to analyze the structural behaviour of masonry spandrels. They play a significant role in masonry walls of ancient buildings, as they guarantee an effective coupling between adjacent masonry piers so as to assure high in-plane strength and stiffness for the walls. The main aim of the research is to point out the actual response of such structural components under seismic loads. Two spandrels with different lintels are considered in the study, they have been subjected to a controlled vertical displacement history so as to simulate their response under seismic actions. Moreover the effect of a strengthening intervention for spandrels that consider the coupling between the masonry beams and steel ties has been pointed out. The results achieved make up for the lack of experimental data on the behaviour of these structural elements and constitute a valid reference to calibrate nonlinear numerical models for the assessment of the ancient masonry buildings seismic performance. KEYWORDS: ancient buildings, masonry spandrel, experimental tests. 1. INTRODUCTION Ancient masonry buildings (AMB) constitute a significant portion of existing buildings around the world. Many of these structures have a historical and cultural value and are considered as architectural heritage. Such buildings are composed of brick or stone masonry load bearing walls and of wooden floors or masonry vaults that usually form the horizontal structural system. A large number of these traditionally-built structures are located in earthquake prone regions and have shown poor seismic performance under past earthquakes, which resulted in heavy damage and collapse causing many casualties (Tomaževič 2000). An accurate structural assessment as well as the development of effective strengthening techniques is therefore of paramount importance for AMB. In fact, a rough analysis may lead to either underestimate or overestimate the safety of these structures. In the former case serious risks for human beings can be met, while in the latter case excessive strengthening measures, that cause high intervention costs and important changes in the original structures, could be employed. In any case, after strengthening the floor systems in order to prevent the out-of-plane displacements of the masonry walls so as to avoid the early collapse of some masonry piers affected by dangerous out-of-plane bending moments, the seismic performance of AMB is governed by the in-plane structural behaviour of the shear walls. These are bi-dimensional elements with openings of different dimension so as to allow for windows and doors. In general, a masonry wall may be considered as an assembly of vertical cantilevers of different dimensions connected together, at floor level, through spandrels (masonry beams). The spandrels in AMB, that normally have the depth comparable with the length, considerably increase both in-plane strength and stiffness of the walls, so that they play a very important role in the AMB earthquake resistance. In the last years a big effort has been devoted to defining effective analytical and numerical models tailored for AMB seismic assessment and for the strengthening design, as their seismic response dramatically differs from that of the modern structural systems (e.g. steel or concrete structures). So several models according to different theoretical approaches have been developed so far. Many of such models are used for research and, being based on complex finite element formulations (Lourenço 1996), are high computationally demanding so that they cannot be employed