Abstract
Structural health monitoring systems are being recognized as effective tools to minimize maintenance costs for civil infrastructures. Recently, many damage evaluation methods for the systems have been proposed. In this paper, a novel monitoring system that uses a hybrid sensor and a new damage detection algorithm is proposed. At first, a hybrid FBG sensor for monitoring strain and acceleration is proposed. The sensor consists of an FBG element and a mass to form a vibration system. Performance evaluation was carried out through the strain and acceleration measurement experiments using the prototype sensor. Then, a new damage detection algorithm based upon combined use of natural frequency and strain as damage indexes is proposed. Strain information was used as a substitute for natural frequencies of higher modes. Many damage scenarios for a moment-resistant frame were tested for verifying the performance of this algorithm. The results show that the sensitivities of strain and natural frequency are significantly different. Based on this finding, damage position identification was carried out with the help of support vector machines (SVM). It is confirmed that combined use of natural frequency and strain measurement enhances the performance of the SVMs.
