AN EXPERIMENTAL-STUDY ON THE USE OF DYNAMIC TESTS FOR SURVEILLANCE OF CONCRETE STRUCTURES

A method is presented for the use of dynamic response as an inspection and surveillance tool for the long term monitoring of concrete structures (mainly bridges) and for the analysis of these dynamic experimental data to ensure their correct use to this end. The method is based upon the definition of a finite element model for the structure, for the identification of stiffness characteristics (related to cracking) starting from modal dynamic parameters (natural frequencies and mode shapes) derived from dynamic tests. Some advantages can be obtained when compared with static tests: mainly, the recording of dynamic data is readily achieved because acceleration transducers can be mounted easily in the structure instead of displacement transducers. In order to check the feasibility and accuracy of the method presented, several damage identification tests were performed in the laboratory on groups of reinforced concrete beams with different and well defined cracking patterns. Dynamic response was measured by acceleration transducers. This experimental verification clearly shows the effectiveness of the proposed method in tire identification of location extension and amount of cracking wizen some important requirements concerning the dynamic data recorded are taken into account. In particular, more than the first natural frequency must be evaluated.