Operational Structural Modal Identification Of Buildings Based On Hilbert Vibration Decomposition

Operational modal parameter identification of building's structures under ambient excitations is popular research focus.In this paper,studies operational modal parameter identification methods of structures under ambient excitation based on Hilbert Vibration Decomposition(HVD)are studied,and the technical analytical procedures for operational modal parameter identification of building's structures based on HVD are devolped.The main research contents are as follows:(1)Inverse method to realize the zero-phase infinite impulse filter(IIR)filter and adaptive continuation algorithm to reduce the influencers of boundary effect of HVD on the modal parameters identification are proposed.With both of them,the structural modal parameters identification by HVD and least-squares complex exponential method is improved,by which the structural modal parameters are efficiently identified.(2)Modal parameter identification method is proposed based on HVD and random decrement method under the ambient excitation by any single point of the vibration response signal.Operational modal frequencies and damping ratios are identified by the least squares method with free-vibration decay signals which are obtained by random decrement technique(RDT)from modal signal components extracted by HVD from dynamic response signals of structures under ambient excitation.Modal parameters of a 5-dofs framework are identified by the proposed method.The results show that modal frequencies identified are reliable and the error is within 5%.It has nothing to do with the excitation wave.The result of structure damping ratios for Stationary response signals has a higher degree of accuracy and the error is within 5%.Modal parameters of a 12-story framework experimental structure are identified,and compared with other identifying methods,the results show that modal frequencies identified are reliable.The result of structure damping ratios has acceptable degree of accuracy.(3)Modal parameter identification method based on HVD and Natural excitation technique is proposed,using the signal analysis to deal with any two-point vibration response signal of a building structure under ambient excitation.Operational modal frequencies and damping ratios are identified by the least squares method with free-vibration decay signals which are obtained by the natural excitation technique(NExt)from modal signal components extracted by HVD from dynamic response signals of structures under ambient excitation.Modal parameters of a 5-dofs framework are identified by the proposed method.The results show that modal frequencies identified are reliable and the error is within 2.5%.It has nothing to do with the excitation wave.The result of structure damping ratios has acceptable degree of accuracy regardless of the waveform excitation.Modal parameters of a 12-story framework experimental structure are identified,and compared with other identifying methods,the results show that modal frequencies identified are reliable.The result of structure damping ratios has acceptable degree of accuracy and lies between other methods.(4)Based on HVD and stochastic subspace modal parameter identification method,the vibration response signal of structures is dealed with,under ambient excitation,by Hilbert vibration decomposition to decompose vibration signal into several signal which contains structure modal information.Operational modal frequencies ? damping ratios and mode shapes are identified by stochastic subspace based on HVD.Modal parameters of a 5-dofs framework and a 12-story framework experimental modal are identified by stochastic subspace and stochastic subspace based on HVD respectively and the error of modal frequencies is within 2.5%,but the former does not exist false mode.The results show that modal frequencies and mode shapes identified are reliable and consistent.There are some differences between the two methods.