Structural damage identification from dynamic-test data

The paper deals with a methodology for the use of dynamic response as an inspection and surveillance tool for concrete structures (mainly bridges). The method is based upon a finite-element analysis for identification of stiffness characteristics (related to cracking) starting from modal dynamic parameters (natural frequencies and mode shapes) derived from dynamic tests. The use of dynamic data is convenient because acceleration transducers can be easily mounted in the structure instead of displacement transducers, mainly when the bridge to be tested overpasses a river, high valley, or traffic road. Several damage-identification examples are performed with groups of reinforced concrete beams with different and well-defined cracking patterns. Dynamic response is measured by acceleration transducers. This experimental verification clearly shows the effectiveness of the proposed method in the identification of location, extension, and amount of cracking when some important requirements concerning the dynamic data recorded are taken into account. In particular, more than the first natural frequency must be evaluated.