EVALUATION OF SHEAR STRENGTH OF MASONRY PANELS THROUGH DIFFERENT EXPERIMENTAL ANALYSES Prof Antonio Borri, Giulio Castori & Marco Corradi University of Perugia Dept of Civil and Environmental Engineering Via Duranti, 93 - 06125 Perugia, Italy mcorradi@strutture.unipg.it KEYWORDS: Masonry panels, shear tests, shear strength. ABSTRACT The paper addresses the problem of evaluation of strength of masonry walls, within the context of seismic assessment of existing buildings. In-plane behaviour of full scale stone and brick masonry panels has been studied under monotonic diagonal-compression and shear-compression loading in quasi-static test facility. The experimental research was carried out in Abruzzi and Umbria since the 1990s, and it represents an important database for mechanical characterization of some widely used masonry walls in these seismic regions. The monotonic shear-compression and diagonal compression tests were performed under load control and experimental data have provided information about in-plane behaviour of un- reinforced masonry (URM) walls. Failure modes, shear strength, displacement capacity and post-peak performance are discussed. A presentation is also given of the results of a F.E. investigation for shear strength evaluation of masonry walls. F.E. modeling non-linear procedure (available in code Lusas) was used for the representation of masonry panels. The numerical simulations are compared with experimental results and the reliability of the different finite element models is discussed. These models are used for the simulation of diagonal compression and shear-compression tests on masonry panels. INTRODUCTION Historic masonry buildings in urban centres have not been conceived to resist seismic loads. They have been built in materials and systems that resist the compression caused by the gravity loads but not the tensile and shear resulting from earthquake ground motion. These disadvantages associated with many historic masonry walls have recently led researchers to the development of testing methods in order to calculate the shear strength of masonry panels. The reconstruction work is now underway in the area struck by the 2009 earthquake in Abruzzi, but many difficulties could be eliminated if better technical information regarding the mechanical characteristics of masonry structures typical of this part of Italy are available. In their calculations structural engineers and technicians have often referred to not well-identified parameters for different kinds of masonry walls found in scarce bibliography studies. Double-leaf stone masonry walls are commonly encountered in Italy and Mediterranean countries in historic buildings dating back to ancient times and up to the beginning of 20 th century. Developing reliable mathematical models to predict and analyze the behaviour of this type of masonry under horizontal forces is known to be a difficult task. The classification and the analysis of historical masonry typologies were conducted in the past with different purposes in mind. However these contributions have rarely included an experimental part regarding the mechanical characteristics of masonry due to the uncertainty in the determination of mechanical characteristic from in-situ test. Masonry walls have been classified with regard to the constituting materials, section dimensions, texture and mortar types, but very rarely with regard to their shear strength and shear elastic modulus. Since the mechanical data of masonry relevant for the assessment of seismic behavior of historic masonry buildings was lacking, a substantial amount of experimental and analytical research has been carried out in the last decade to investigate their seismic behavior.