GLOBAL DAMAGE IDENTIFICATION BASED ON VIBRATION SIGNATURES APPLIED TO MASONRY STRUCTURES LUÍS F. RAMOS † , PAULO B. LOURENÇO † , GUIDO DE ROECK * , ALFREDO CAMPOS-COSTA ** † University of Minho, ISISE, Portugal, e-mail: lramos@civil.uminho.pt * Catholic University of Leuven, Department Civil Engineering, Belgium ** Laboratório Nacional de Engenharia Civil, Portugal SUMMARY The present paper aims at damage assessment of masonry structures in an early stage. Two replicates of historical constructions were built in virgin state, one arch with 1.5 m span and one shear wall of 1 m 2 . Afterwards, progressive damage was applied and sequential mo- dal identification analysis was performed in each damage stage, aiming at finding adequate relations between changes in dynamical behaviour and internal crack growth. During the dy- namic tests, accelerations and strains were recorded in many points of the replicates. Com- parisons between different techniques based on vibrations measurements were made to evalu- ate which methods are the most suitable for identifying damage in masonry constructions. INTRODUCTION Preservation of the architectural heritage is considered a fundamental issue in the cultural life of modern societies. Modern requirements for an intervention include reversibility, unobtru- siveness, minimum repair and respect of the original construction, as well the obvious func- tional and structural requirements. In the process of preservation of ancient masonry structures, damage evaluation and monitor- ing procedures are particularly attractive, due to the modern context of minimum repair and observational methods, with iterative and step-by-step approaches. High-priority issues re- lated to damage assessment and monitoring include global non-contact inspection techniques, improved sensor technology, data management, diagnostics (decision making and simulation), improved global dynamic (modal) analysis, self-diagnosing / self-healing materials, and im- proved prediction of early degradation. This paper focus on improved global (dynamic) modal analysis for damage detection. DAMAGE IDENTIFICATION PROCESS The present paper deals with the problem of damage identification by using Global and Local damage identification techniques. It is advantageous to have two categories of damage assess- ment methods: (a) the vibration based damage identification methods, currently defined as Global methods, because they do not give sufficiently accurate information about the extent of the damage, but they can identify its presence and define its precise location (e.g. Chang et al., 2003); and (b) the methods based on visual inspections or experimental tests, such as