Nonlinear Acoustic Diagnostics of Defects and Damages of Buildings and Engineering Constructions
V.Robsman, N.V.Ershova (Transport Building Research Institute, Moscow, Russia)
A large experience was accumulated during last decade in the application of nonlinear methods of acoustic diagnostics of bridges, tunnels, thermal power stations, new high-rise buildings and historically valuable architectural objects. Most detailed information was obtained at the investigation of the contact zone of basement and surrounding ground. This contact problem plays the principal role for the new building up when the new house is surrounded by tumbledown houses, and the subway is laid under it. Nonlinear spectral transformations were observed at large-scale measurements, devoted to active acoustic probing and to processing of acoustic emission signals. It is stated both experimentally and theoretically, that nonlinear phenomena grow if the number of defects increases in materials and constructions. Defect structure develops with increase in external applied load, and it leads to the amplification of distortion of both spectra and probability distribution of amplitudes of acoustic signals. Variation in spectra are similar to the finite number of discrete transitions analogous to .order-chaos. transition. Nonlinear transformation of probability can be presented by the set of known S-Jonson distribution.
Section : 11