Operational modal analysis of harbor crane under ambient excitation

GONG Lingzhu1, YANG Xiaoxiang2, ZHONG Shuncong2*,
GUO Jinquan2, XV Zhongfu1, LIANG Chongzhong1
(1.Fujian Institute of Special Equipment Inspection, Fuzhou 350001, China;
2.School of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350108, China)

Abstract: Aiming at solving the excitation problems of a 40 t harbor crane, operational modal analysis using natural excitation technique (NExT) were investigated. Ambient excitation, such as that caused by wind, was employed to excite the crane. With the unknown input (excitation) signal, only the response signals were recorded. Taking one of the response signals as the reference, the cross power spectra of response signals were calculated and used for modal identification of the crane. The first four lower modal parameters (frequencies, damping ratios and mode shapes) were obtained. The results indicate that operational modal analysis of harbor cranes using NExT is applicable. Therefore, NExT could be recommended in modal testing and analysis of other special equipments.
Key words: ambient excitation; operational modal; modal analysis; harbor crane; natural excitation technique(NExT)