Effect of noise on output-only structural identification of beams

Abstract

Output-only structural identification is conducted by output data of the structure. These data usually include structural response together with some noise. Success of output-only methods in determining the vibration parameters of a structure depends on the signal to noise ratio (SNR) of the output data. In this paper, the vibration parameters (Natural frequency and Mode shape) of a contilever beam have been obtained using output data which have different signal to noise ratios. The vibration parameters of the beam were determined using modal analysis of finite element model and considered as reference parameters. Then, appropriate input was applied to the beam and the acceleration signal was obtained. To generate noisy data, noise with different powers compared to signal powers were added to acceleration signal. The modal parameters of the beam were obtained using two output-only methods, Peak Picking (PP) and Stochastic Subspace Identification (SSI). The vibration parameters having signal-to-noise ratios greater than 25 (lower noise level) for all considered modes were identified properly. At a signal-to-noise ratio of 0.25 to 25 (higher noise level), it was not possible to identify the modal parameters of the first mode of the beam, but the parameters of the higher modes were identified with good accuracy.

Keywords

• structural identification
• output-only method
• contilever beam
• signal to noise ratio peak picking
• stochastic subspace identification