TY JOUR TI Change in the Natural Vibration Frequency Spectrum of the Steel Pipe Mathematic Model Depending on Sizes, Location, and Number of Local Defects KW defect KW natural vibration frequency KW frequency spectrum KW genetic nonlinearity KW vibrations KW monitoring KW limit state KW threshold value KW facilities KW defect KW damage. JO Safety in Technosphere AU Suslonov, A.. AU Samarin, V.. AU Sushchev, S.P. AU Novgorodova, A.. PY 2015 IS 4 PB INFRA-M Academic Publishing LLC.