MTMD to increase fatigue life for OWT jacket structures using Powell's method: Fid-Bau Portal

MTMD to increase fatigue life for OWT jacket structures using Powell's method

Ju, Shen-Haw / Huang, Yu-Cheng

Abstract The Powell's method was developed to determine the optimal stiffness and damping of multi-tuned mass dampers (MTMD) in offshore wind turbine (OWT) support structures under fatigue loads. Numerical examples indicated that the Powell's method results are always better than those using MTMD formulations. With the exception of the blade passing (3P) frequency, it was found in this work that a positive integer (n) multiple of the 3P frequency will also result in a large wind-induced vibration, which can be excited by the frequency of the first structural vertical rotation mode and will cause significant fatigue damage. The first translation mode TMD installed at the tower top is efficient to increase fatigue life at the tower and brace connections, but it cannot reduce fatigue damage at the column and brace connections below the platform. The second translation mode TMD can reduce fatigue damage resulting from large wave loads and thus increase the fatigue life of the braces and columns. The mode-3 TMD with a reduction in the 3(3P) vertical rotation can effectively increase the fatigue life of the braces and columns. Thus, the appropriate use of these TMDs can be effective for the fatigue problem of OWT support structures.

Highlights • Powell's method results are always better than those using MTMD formulations. • The first mode TMD can increase fatigue life at tower and brace connections. • The second mode TMD can reduce fatigue damage resulting from large wave loads. • The TMD to reduce 3(3P) vertical rotation can increase brace and column fatigue life. • The use of TMDs can be effective for the fatigue problem of OWT support structures.