Abstract |
Nonlinear Acoustic Diagnostics of
Defects and Damages of Buildings and Engineering Constructions
V.Robsman, N.V.Ershova (Transport
Building Research Institute, Moscow, Russia)
e-mail:
robsman@mail.ru
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