VIBRATION TESTING FOR NONDESTRUCTIVE EVALUATION OF BRIDGES .1. THEORY

For nondestructive evaluation of the structural integrity of a bridge, a set of frequency-response functions is used as signatures. The signatures are obtained by controlled vibration tests. A number of methods are presented here that are candidates for objective and effective examination of bridge signatures. These methods are based on techniques of digital signal processing and pattern recognition. A ''smoother'' that may be used to preprocess signatures is presented. To examine robustness of a technique, synthetic noise is added to signatures. To evaluate the effectiveness of different interrogation procedures, the method of minimum crack sensitivity measure is introduced. In this first part of the paper, the theoretical bases of the previously mentioned methods are presented. In the second part, details of bridge structures that were investigated, sample signatures, and results of interrogation using candidate methods are presented.