Structural Damage Identification Using Strain Frequency Response Function (SFRF) Based Method

The increasing load level and ever-growing transportation add to the extension of service time in bridge structures, make most existing bridges can not satisfy modernized transportation demand. In this regard, structural damage detection has been the hottest topic in civil engineering; however, it is of great significance in theory development and realistic application.Research has been implemented on the computational comparison regarding newly presented indicators as well as several traditional counterparts using numerical methods. Also, several uncertainties, such as measurement noise, different force location, incomplete measurement information, and frequency ranges, are involved in consideration. Specific progresses which have been made in this paper are listed chapter by chapter as below:In the first chapter, the purpose and significance of this paper are discussed with the involvement of the latest development in Structural Health Monitoring (SHM), home and abroad. More importantly, problems existing in the current methods are presented as a guide for further research in the paper.In the second chapter, a review is figured out including structural static load tests, vibration excitation method and dynamic parameter measurement techniques. Furthermore, several crucial questions, in terms of optimal transducer placement and incomplete modal data for damage detection, are proposed. Especially the byproduct of incomplete measurement regarding transmission zeros are deduced to some extent. In addition, modal based detection and testing techniques, and damage types are well summarized and categorized.In the third chapter, damage identification theories using modal data, flexibility matrix, residual force vector, and frequency response function are presented, incorporating three novelty indicators (MAC_sfrf COMAC_sfrf, and Strain Frequency Response Function Curvature Ratio). Subsequently, frequency response function of Multi-DOF systems and their formulas are particularly derived.In the fourth chapter, various conventionally used damage detection techniques, together with the newly proposed three methods (MAC_sfrf, COMAC_sfrf, and Strain Frequency Response Function Curvature Ratio) are compared in a fundamental sense, in which issues such as measurement noise, different force location, incomplete measurement information, and frequency ranges etc. are included in the numerically simulated plane model under various damage cases.In the fifth chapter, conclusions of this paper are systematically made. Also, a guideline of further research on this topic is summarized.