A new algorithm and damage index for detection damage in steel girders of bridge decks using time-frequency domain and matching methods

Abstract

Damage identification, especially in the early stages, is one of the most important factors in preserving and maintaining structures and infrastructures. Structural Damage can lead to adverse and unwanted changes in the system. Unless these damages are identified and fixed on time, they gradually worsen, which may eventually lead to negative effects on the mechanism of the structure. For example, one of the most common types of damage in all types of structures is cracks causing changes in the characteristics and qualifications of the structures including reducing the stiffness and increasing the damping. The structure may experience significant problems if the crack extension increases. Changes and reductions in the cross-sectional area, changes in the characteristics and qualifications of the materials used, damage in the connections, or boundary conditions are considered to be among the other structural damages. Changes in the construction of the structure can cause changes in the dynamic behavior of the structure, too. In this research, a new algorithm to identify damages in the steel girders of the bridge decks has been presented. Based on this algorithm, the response signals of the steel girder are recorded and the reported signals are processed by Bern-Jordan time-frequency distribution and, finally time-frequency matrices are calculated. Then, the damage is identified and its location is determined by using the proposed damage index (C-Index). In addition, the proposed algorithm has been evaluated on the College Bridge. The analytical model of the College Bridge was designed based on the as-built details, field inspections, and material strength tests. To conduct a comprehensive evaluation, 10 different damage scenarios were considered. The results obtained from this research show that the proposed damage index can identify the damage and its location in steel girders with a high level of accuracy.