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Modal parameters estimation plays an important role for structural health monitoring. Accurately estimating the modal parameters of structures is more challenging as the measured vibration response signals are contaminated with noise. This study develops a mathematical algorithm of solving the partially described inverse singular value problem (PDISVP) combined with the complex exponential (CE) method to estimate the modal parameters. The PDISVP solving method is to reconstruct an L 2 -norm optimized (filtered) data matrix from the measured (noisy) data matrix, when the prescribed data constraints are one or several sets of singular triplets of the matrix. The measured data matrix is Hankel structured, which is constructed based on the measured impulse response function (IRF). The reconstructed matrix must maintain the Hankel structure, and be lowered in rank as well. Once the filtered IRF is obtained, the CE method can be applied to extract the modal parameters. Two physical experiments, including a steel cantilever beam with 10 accelerometers mounted, and a steel plate with 30 accelerometers mounted, excited by an impulsive load, respectively, are investigated to test the applicability of the proposed scheme. In addition, the consistency diagram is proposed to exam the agreement among the modal parameters estimated from those different accelerometers. Results indicate that the PDISVP-CE method can significantly remove noise from measured signals and accurately estimate the modal frequencies and damping ratios.

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Under the complex marine environment load and the role of the upper wind turbine load, deep sea floating wind turbine support structure would suffer fatigue damage, which often endangers the safety of the wind turbine system. This paper chose the "5 MW baseline" wind turbine model which published by the US National Renewable Energy Laboratory (NREL) as the design basis. The paper uses the OC4-DeepC wind semi-submersible offshore wind turbine model for the verification of offshore floating wind turbines. According to the characteristics of stress and the distribution of stress, the paper selects seven key parts which are prone to fatigue damage are screened, respectively established local finite element models and carried out grid encryption. Based on the SESAM hydrodynamic analysis software and FAST wind motor dynamic load calculation procedure, the fatigue damage of the target node under the action of wind turbine load is studied. The results show that the structural fatigue damage occurs mainly at the horizontal connection of the upper part of the neutral column and the diagonal connection of the lower part of the neutral column. The fatigue damage degree of the crown and the saddle point is relatively large at the connecting rod position.

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