Crack control in concrete using shock wave techniques

This paper focuses on further development of the non-destructive shock wave method used in structural engineering to control the state of reinforced concrete (RC) structures subjected to loading, which frequently leads the formation of cracks in these structures. Our version of this method implies registration of wave processes occurred in concrete due to impact loading and comparison of these processes for undamaged and cracked structures. The parameters of elastic shock waves are recorded at instants when they are practically independent of fastening conditions and responded best to the presence of a crack. Numerical simulations provide a means of analyzing parameter changes in the wave front passing through the region of cracking. A qualitative criterion is formulated to assess whether the examined concrete is undamaged or there are cracks in it and how the structure condition changes at increased load and during the elimination of cracks. This criterion is defined as the ratio of acceleration amplitudes of first half-waves registered in areas on both sides of the crack. A comparison of computational results and experimental data supports the validity of the criterion. Analysis of the results obtained from a series of numerical experiments makes it possible to compute optimal points for applying impulse loading and to determine sensor positions for recording accelerations needed to compute the criterion.