Sensitivity Analysis of Modal Parameters of a Jacket Offshore Wind Turbine to Operational Conditions

Round 1

Reviewer 1 Report

Authors have analyzed modal parameters of offshore wind turbine under operation. The study is interesting and valuable, but the following issues should be considered:

Regarding section 2.2, it is unclear how is the effect of water considered in the simulations? This is important because you discuss this topic in the Discussion.

Discussion is more a Conclusion now, but somewhat lengthy. It would be better to have separate Discussion and separate Conclusion chapters. 

Abbreviation DAQ is used before the full phrase is introduced for the first time.

"The first FA and SS natural frequencies and damping ratios identified from the measurements are plotted versus wind speed..." but these are not natural frequencies, are they? Wind is providing continuous excitation, no?

In general, "damping ratio" is mentioned many times but defined in only in section 3.1.4.1, why that late? 

"Moreover, the damping ratio of the first SS mode is identified at approximately 1% and the damping ratio of FA mode varies between 0 and 15%..." it is not mentioned how are these value determined? I assume it is sec 3.1.4.1 again.

Author Response

Please see attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

The title of the paper is too long. Modelling can be removed as Analysis already implies the existence of a model. The Block Island is not a relevant aspect of the study so it can be omitted from the title. The work addresses a fixed wind turbine and this should be reflected in the title and abstract.

 References about the modelling and analysis of fixed offshore turbines is too brief eventually not covering the spread of results available as for example:

http://dx.doi.org/10.1016/j.engstruct.2015.07.038

The same applies to the references on sensors in platforms, where it is missing specific references of platforms such as for example:

https://doi.org/10.1016/j.oceaneng.2018.10.014

 The study is an interesting one and the analysis covers different relevant parameters and provides conclusions related to them. The conclusions however include aspects that can be considered of general nature and others that may be more platform specific. It would be useful if the two different types of conclusions are clearly identified and separated.

 Finally the study addresses fixed structures but no consideration is given to the effect of the uncertainties in soil conditions on the dynamic behaviour as discussed for example in:

 

https://doi.org/10.1016/j.apor.2018.10.014

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The paper has been somewhat improved

Many references have incomplete author lists and other details are missing

Author Response

Thank you for this suggestion. The references are revised to include the full list of authors.