This paper presents the wet damping estimation of the segmented hull model using the random decrement technique together with the continuous wavelet transform. The tested 16 sea states are grouped together based on the speed of the ship in order to figure out the possible influence of the ship speed on the damping ratio. The measured time histories of vertical bending moment for each tested sea state were processed with random decrement technique to derive the free decay signal, from which the damping ratios are estimated. Also, the autocorrelation functions of the filtered signal were calculated and comparison was made with the free decay signal obtained from the random decrement technique. Then the wet damping ratios for each sea state group, as well as precise wet natural frequencies, are estimated by using continuous wavelet transform. It turned out that the wet natural frequencies derived from the measured signal did not show any significant discrepancy compared with those obtained by wet hammering test, whereas the damping ratio did. It was considered that the discrepancy of the damping ratio between in calm and moving water may be attributed to the viscous effects caused by dramatically different flow pattern and relative velocity between the vibrating structure and surrounding fluid particles.

A method for the direct identification of vibration parameters from the free response

랜덤 감쇠기법을 이용한 분할모형의 접수 감쇠계수 추정

http://www.theglobaljournals.com/ijar/file.php?val=July_2014_1404450836__189.pdf

The Use of Modal Analysis to Examine the Bricks in the Saline Environment

Identificação modal de uma estrutura aeronáutica via algoritmo de realização de sistemas

Identification of dynamic structural characteristics in engineering by means of their responses to measured vibration is an important step for the correct characterization and monitoring of real structures. This article presents the results of a dynamic load test performed on the PG oil platform, located at Talara, Peru. The work included measurements of vibration in twelve positions on the platform, located on the floors of the structure. As excitation source, it was mainly due to wind action and wave motion, and thus the measurements were made without interruption of the structure operation. The collected data were analyzed using non-parametric technique of digital signal processing, which provided the main dynamic parameters of the structure. From there, we proceeded to the elaboration of a numerical model of the structure, based on the Finite Element Method, which represents accurately its structural behavior.

methods

Characterization of jacket-type offshore structure by operational modal analysis

/pdf/medidas-de-deslocamento-e-vibracoes-atraves-de-imagens-de-4n5fj3aajm.pdf

A method for the direct identification of vibration parameters from the free response

Citations

랜덤 감쇠기법을 이용한 분할모형의 접수 감쇠계수 추정

The Use of Modal Analysis to Examine the Bricks in the Saline Environment

Identificação modal de uma estrutura aeronáutica via algoritmo de realização de sistemas

Characterization of jacket-type offshore structure by operational modal analysis

Medidas de deslocamento e vibrações através de imagens de

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