Proceedings of the Third European Conference on Structural Control, 3ECSC, 12-15 July 2004, Vienna University of Technology, Vienna, Austria LONG-GAUGE FIBER-OPTIC SENSORS: A NEW APPROACH TO DYNAMIC SYSTEM IDENTIFICATION Fabio Casciati 1 , Marco Domaneschi 2 , Daniele Inaudi 3 , Angelo Figini 4 , Branko Glisic 5 , Akhilesh Gupta 6 1,2 Department of Structural Mechanics, University of Pavia, Via Ferrata 1, 27100 Pavia, Italy 3,4,5,6 SMARTEC, Via Pobiette 11, TI 6928 Manno, Switzerland An innovative approach to the measurement of dynamic variables and damage detection by fiber-optic sensors is being developed and presented in this paper. Initial results from the dynamic laboratory tests carried out on a single-storey frame model placed on a shaking table suggest practical applications of fiber-optic sensors on real structures. The goal consists of acquiring dynamic variables from two approaches: the traditional one based on accelerometers installed on the storey and the basis of the frame structure, and the innovative one using SOFO dynamic system which is based on long-gauge fiber-optic sensors installed on the columns of the frame structure. A comparison between the results from the two approaches shows that some limitations associated with traditional dynamic measurement methods can be overcome by the use of better performing fiber-optic sensors. In addition, the use of long-gauge strain sensors allows the detection of local damage that is hardly visible in the global frequency response of the structure. In particular the fiber-optic sensors show a very high sensitivity and extend the frequency range (1mHz-1KHz). Keywords: fiber-optic sensors, traditional accelerometers, dynamic-laboratory tests, damage detection 1 Introduction New and emerging opportunities in the field of building control system and the necessity of reduction of structural maintenance costs have increased the importance and the applications of structural monitoring and assessment systems. An innovative technique of structural monitoring through the usage of long-gauge fiber-optic sensors [1] is presented in this paper. 1 Professor, fabio@dipmec.unipv.it 2 Ph. D. Student, marcodom@dipmec.unipv.it 3 CTO, inaudi@smartec.ch 4 Area Manager, figini@smartec.ch 5 Solution and Services Manager, glisic@smartec.ch 6 B. Tech. Student, gupta@smartec.ch 2 Laboratory-Testing Facilities The testing environment, where the simulations were conducted, composed of a shaking table to induce the external forces on a structural system. This structural system is a physical model of single-storey frame structure (presented in Figure 1) based on shear type model with single degree of freedom. Two acquisition systems are installed on the structure. A traditional one, with mono-axial accelerometers installed on the shaking-table (basis) and the single storey, and an innovative SOFO dynamic system, which uses long-gauge fiber optic sensors installed on the columns of the physical model. In Figure 1 it is possible to identify the different sensor systems. Figure 2 shows the acquisition and processing unit of SOFO dynamic system. Figure 1: Structural model on the shaking table