Shock wave method for monitoring crack repair processes in reinforced concrete structures

A nondestructive method for monitoring the crack state in reinforced concrete structures based on the recoding of wave processes in these structures under shock actions is proposed. The essence of the method and its possibilities are demonstrated by an example of the study of the behavior of a reinforced concrete beam with a crack at various stages of crack development and repair. Numerical simulation was used to study variations in the wave front characteristics in the crack area. A quantitative criterion was formulated, which permits estimating the concrete integrity or the existence of crack in it and monitoring the variations in the crack state in the process of loading the structure and the crack repair. The criterion is determined as the ratio of the amplitudes of the first half-waves of the acceleration wave front registered in regions on the opposite shores of the crack. The criterion value is independent of the amplitude of the shock action and the beam fixation conditions and is solely determined by the mechanical state of the material used to repair the crack. The criterion adequacy was demonstrated by comparing the results of numerical simulation with experimental data. A cycle of numerical experiments were carried out, which, for each duration of the shock action, permits determining the optimal values of the distance between the pulse application point and the acceleration recording points at which the criterion is most sensitive to the crack state.