A Comparison of Dynamic Testing Methods for Evaluating a Truss Bridge

Bridges can be characterized through either full-scale static or dynamic testing methods to obtain a more reliable description of their in-service characteristics than is often available from idealized analytical models. The results obtained from a full-scale characterization can be used to support decisions related to serviceability problems, retrofits, and maintenance of a structure. A number of different dynamic testing methods are available for characterizing in-service bridges including ambient vibration testing, forced-vibration testing, and free vibration testing. The authors recently conducted a field testing program on an aged truss bridge. The bridge was dynamically characterized by ambient vibration and forced vibration testing methods. The objective of this paper is to compare the global characterization results obtained from each test method and to evaluate the advantages and limitations associated with each approach for characterizing similar structures.