19. Elasto-dynamic Damage Evaluation of Bridges

This chapter introduces two elasto-dynamic damage evaluation methods for bridge structures without traffic blocking. The first method identifies damage parameters from natural frequencies and mode shapes. Since this is an ill-posed problem, the identified damage parameters from all measurements could be unreliable due to measurement noises. A feasible solution to this problem is using only part of natural frequencies and mode shape points in damage identification. For this purpose, an algorithm based on well-posedness analysis is proposed to select the optimal combination of natural frequencies and mode shape points. Another method is called the Tap-scan damage detection method, which is featured by extracting bridge damage information from the acceleration of a passing vehicle mounted with a well-controlled tapping device. The theoretical basis and hardware setup are presented in detail. In addition, several on-site experiments are given to illustrate its application potential to real bridge structures.

The main advantage of these two methods is not requiring traffic blocking during bridge evaluation. Besides, since they extract damage information from the self-comparison of bridge properties among different sections, they do not require the reference state of the intact bridge. These two features are crucial to their practical implementations.