H₂-norm optimization and performance assessment of a jacket offshore platform under coupled wind-wave-seismic excitations via track mono-, bi- and tri-stable nonlinear energy sink cells

Track nonlinear energy sinks (TNESs) have been proven to be an effective vibration reduction measure. However, the dimensions and weights of traditional TNESs limit its practical engineering application. This paper makes different types of TNESs including track monostable nonlinear energy sinks (TMNESs), track bistable nonlinear energy sinks (TBNESs) and track tristable nonlinear energy sinks (TTNESs) cellular. In addition, TMNES cells, TBNES cells and TTNES cells are distributedly or centrally applied to a jacket offshore platform to mitigate structural response. Firstly, the analytical models of a jacket offshore platform coupled with TMNES cells, TBNES cells and TTNES cells are derived. Secondly, the spectrum model and numerical simulation of wind, wave and seismic are, respectively, established and conducted. Then, the multi-objective frequency domain optimization designs based on H₂-norm criteria of a jacket offshore platform coupled with TMNES cells, TBNES cells and TTNES cells are carried out. Finally, the vibration reduction performance and robustness performance of different types of TNES cells are compared under multi-hazard excitations. The results show TNES cells can effectively mitigate adverse horizontal vibration of a jacket offshore platform. The multi-modal control performances of distributed TNES cells are superior to centralized TNES cells. In addition, the robustness performances of TBNES cells and TTNES cells are superior to TMNES cells against the change of coupled excitations. In a word, distributed TNES cells are a better choice when subjected to natural hazards. This research provides the necessary theoretical basis for designing and applying the distributed or centralized TMNES cells, TBNES cells and TTNES cells.