5 th World Conference on Structural Control and Monitoring 5WCSCM-10322 A F AST METHOD FOR STRUCTURAL HEALTH MONITORING OF STRATEGIC BUILDINGS F. C. Ponzo, G. Auletta, R. Ditommaso DiSGG, University of Basilicata, Potanza, Italy fcponzo@libero.it , gianluca.auletta@tiscali.it , r.ditommaso@unibas.it Abstract The demand of a widespread health monitoring of strategic buildings in seismic areas has emphasized the need to realize studies in order to verify the feasibility of economic and fast procedures to detect anomalous vibrations on a large number of buildings, to perform post earthquake monitoring and to define first damage scenarios. Structural health monitoring systems are usually realized with a large number of sensors, suitably distributed on the structure, often involving complex elaborations of big amounts of data. When applied on a large number of buildings these systems can hardly result to be realizable for the necessary long time and the high cost to extract useful information. Within the Italian research RELUIS project, funded by the Italian Department of Civil Protection, a specific task deals with the possibility of applying a fast procedure to determine the damage evolution on a large number of structures after seismic events. The method developed and presented in this paper is based on a statistical approach that uses the most significant data recorded on the top floor of the building, with the purpose of extracting the value of the maximum inter-story drift expected along the building height, adopted as damage indicator. The parameters considered in the method are the maximum top acceleration, the modal frequencies variation and the equivalent structural viscous damping variation. Experimental tests carried out on scaled R/C models and several numerical non linear dynamic analyses have been considered to verify the feasibility of this approach. Introduction The assessment of an increasing number of aged structures and infrastructures requires a huge effort, especially if the purpose is to provide a faithful evaluation of seismic risk. The current practice of periodic visual inspections, for the safety evaluation appears more and more inadequate. During the past two decades, a significant amount of researches (Ditommaso et al. 2010; Picozzi et al., 2010a; Picozzi et al., 2010b; Ponzo et al., 2010) have been carried out in the field of non-destructive damage evaluation (NDE) utilizing the changes in the dynamic response of a structure. The NDE methods can be classified into four levels [Stubbs et al. 2000], according to the specificity of the information provided by a given approach [Rytter 1993]: (i) Level I methods that only detect if damage has occurred; (ii) Level II methods that detect if damage has occurred and simultaneously determine the location of damage; (iii) Level III methods that identify if damage has occurred, determine the location of damage as well as estimate the severity of damage; (iv) Level IV methods that identify if damage has occurred, determine the location of damage, estimate the severity of damage, and evaluate the impact of damage on the structure. Each level of damage identification described above requires a gradual increasing amount of data and more complex algorithms, with a consequent rising of the costs, elaborations time and error probability. A specific task of the RELUIS project 2005-08, funded by the Italian Civil Protection Department (DPC), deals with devising and implementing effective and fast procedures to get useful information on the damage evolution on a large number of strategic buildings during and after seismic events. The damage detection procedure developed within RELUIS project and described in this paper is a simplified 1 st level procedure based on a statistical approach, to continuously check the safety and reliability of strategic buildings. The feasibility and the cost optimisation are the most important goals of the simplified procedure in order to favour a widespread diffusion of such systems. The method detects the damage evolution by comparing the dynamic response of the building before, during and after the earthquake. The procedure is designed in order to use only few sensors located on the top floor of the monitored building by which it extract some dynamic parameters (i.e. maximum top acceleration, modal frequencies variation and equivalent structural viscous damping variation). These parameters opportunely combined through a non linear relationship obtained by statistic evaluation, allow to evaluate the Damage Index. The main 1