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 sign atures are obtained by controlled vibration tests. A number of methods are presented here that are candidates for objective and effective ex amination of bridge signatures. These methods are based on techniques of digital signal processing and pattern recognition. A ''smoother'' t hat may be used to preprocess signatures is presented. To examine robu stness of a technique, synthetic noise is added to signatures. To eval uate the effectiveness of different interrogation procedures, the meth od of minimum crack sensitivity measure is introduced. In this first p art of the paper, the theoretical bases of the previously mentioned me thods are presented. In the second part, details of bridge structures that were investigated, sample signatures, and results of interrogatio n using candidate methods are presented.