Transmissibilities And Its Application In Operational Modal Analysis

Transmissibility-based operational modal analysis (TOMA) is a kind of novel technique proposed recently, which use single-reference transmissibility function (STF), multi-/poly-reference transmissibility function (MTF), power spectrum density transmissiblity (PSDT), or multivariable power spectrum density transmissibility (MPSDT) as the primary data to extract modal parameters in operational case. Transmissibility-based technology can fundamentally solves the harmonic input problem widely existing in traditional methods, so it shows a new direction for the development of operational modal analysis.Although having significant benefits and broad application prospect, TOMA is just in its start-up step up to now. The unified and orderly theory system of TOMA has not formed. Some key issues has not been discussed, such as the way to get transmissibility, the relation among transmissibilities, and properties of transmissiblities, etc. This thesis is for the purpose of showing the theory system of TOMA by generalize existing conclusions and discuss some key issues have not bee researched. The main contents of the thesis are summarized in the following:(1) Definition and expression in various load conditions of transmissibilities be used as the primary data of operational modal analysis, including MTF, STF, PSDT and MPSDT, as well as that of transmissibilitis in single degree-of-freedom (SDOF) system are discussed. The development and inheritance relations of transmissibilities are revealed.(2) Methods to calculate MTF, STF and PSDT are discussed. The syntheticism of STF is proposed, and the validity of which is proved by numerical study. The syntheticism of PSDT is also proposed, and the validity of which is proved by numerical study and experimental study. The results of transmissiblity syntheticism provide a basis for evaluating the validity and effectiveness of transmissibility estimators.(3) The properties of MTF, STF and PSDT are discussed. The invariability of STF, and the correctness of conclusions are proved by numerical study and experimental study. Some properties of PSDT in different load conditions are also discovered, and the correctness of conclusions are proved by numerical study and experimental study.(4) The relation between MTF and modal parameters. STF and modal parameters, as well as PSDT and modal parameters are discussed systematically. The action principle of using PSDT as the primary data of operational modal analysis is explored from system perspective, and the correctness of conclusions are proved by numerical study and experimental study.(5) The principle, characters and implement method of most existing operational modal analysis methods with transmissibilities as primary data are elaborated. The development and inheritance relations of transmissibility-based operational modal analysis are revealed.(6) The relation between MTF and STF, as well as STF and PSDT are discussed, and the correctness of conclusions about the latter are proved by numerical study and experimental study.