Dynamic deformation interaction of elements of the "drummer-gasket-reinforced concrete beam" system

The use of automated monitoring systems ensures the deformation safety of structures. Deformation control systems are supplemented with the tools which allow evaluating the criticality of the structure state on the basis of vibration measurements. Vibration-based damage detection of the reinforced concrete structures allows detecting the presence of defects in the structure, determining their localization, as well as promptly tracking their development. The results obtained in this study are directly related to the shock-wave vibrodiagnostics of reinforced concrete structures. Special attention is paid to the diagnostics in a “sparing mode”, which does not cause inelastic deformations in the elements of the structure under study. The vibration process in a concrete beam, caused by a local impulse action, is considered. The purpose of this study is to find the parameters of the impulse that forms an elastic wave with the desired frequency spectrum or required wavefront characteristics. One of the main parameters determining these characteristics is the impulse duration. A mathematical model of the dynamic elastic interaction of the elements of the “drummer - gasket - reinforced concrete beam” system was constructed and a series on numerical experiments on the bases of this model was carried out. According to the results of these experiments the dependence of the impulse duration on a number of factors is obtained. These factors are the velocity, mass and dimensions of the striker and the thickness and elasticity of the gasket. These parameters are chosen because they can be varied in a real experiment. It is shown that the impulse duration is most sensitive to the changes in striker velocity and gasket elasticity. Within the selected range of control parameters, it is possible to change the impulse duration from 0.25 to 2.8 ms. Since the impulse duration determines the dominant vibration frequency, one may conclude that in this case frequencies will vary in the range from 200Hz to 1500Hz.