Ultrasonic Damage Measurement in Reinforced Concrete Beams
In several situations the failure of a reinforced concrete structure is preceded by a gradual deterioration of the materials which can be recognised by measuring the change of their physical properties . The main purpose of the destructive tests described in the present paper was to obtain an evaluation of the damage evolution in a reinforced concrete beam, submitted to harmonic displacements imposed by means of a shaking table. A reinforced concrete beam, with two different spans, was designed to sustain a static load of a mass located at the centre of the longer span. Ten identical specimens were prepared and tested at the LNEC (National Laboratory for Civil Engineering, Lisbon) shaking table facility . This paper presents tests, which have been performed in the frame of the European Commission programme ECOEST/PECO (European Consortium of Earthquake Shaking Tables / Central and Eastern European Countries extension). The beams were fixed to the shaking table and submitted to a sinusoidal displacement in the vertical direction, with a pre-established duration and constant amplitude. The tests were carried out by successive stages of increasing amplitudes, until the collapse of each beam was reached. The tests aimed to give an evaluation of the loading history influence on the occurrence of the critical state. During the tests, displacements and accelerations were continuously recorded at several points of the structures, along with ultrasonic measurements taken at different directions, before and after each successive stage. In the present paper the design of the specimens is given. The instrumentation plan, the test setup and the test procedure are also described. Finally, the most relevant results are shown followed by the formulation of a global damage law to predict the limit state of the beams.
W.M. Ostachowicz, J.M. Dulieu-Barton, K.M. Holford, M. Krawczuk and A. Zak
R. Bairrao et al., "Ultrasonic Damage Measurement in Reinforced Concrete Beams ", Key Engineering Materials, Vols. 293-294, pp. 695-702, 2005