Studying the Settlement of OWT Monopile Foundations Using a T-Z Spring with the Torsional Effect
Round 1
Reviewer 1 Report
Summary:
This study investigates the vertical settlement of offshore wind turbine (OWT) monopile support structures, for 5, 10, 15, and 20 MW. For the monopile foundation, the shear resistance of soil may be less than the shear stress generated by the combination of the vertical load and the vertical-direction torsion, that causes large vertical and rotational displacements resulting in the failure of the structure. This situation will be worse when the natural frequency of the first vertical-direction rotation is close to the integer multiples of the 3P frequency. This study analyzes several kinds of OWTs with monopile foundations and develops a t-z spring with the shear and torsional degrees of freedom to simulate the shear stress along the pile and soil surface. This article includes an intriguing research study that can be published in a top journal like Processes. However, a few improvements and enhancements must be performed in order to raise the caliber of this manuscript:
Major Issues:
· The objective of this study is not clear in the abstract of the original version. The investigation, objective, and motivation of this study and research have to be stated explicitly and supported in the abstract of the revised version. As a result, the abstract has to be completely revised and rearranged to make the goal, and objective of this study clear.
· In the introduction section of the updated version, clearly state and describe the paper's contribution. The updated version has to include a sufficient number of references of recent scholarly publications on the same subject of the research study. Please make an effort to compare your results to those of published studies on other renewable resources. Moreover, please try to demonstrate your improvements and contributions in your case study. Please have a look at the following references in the same area of your research:
Stathopoulos T. et.al. (2018), Urban wind energy: some views on potential and challenges, Elsevier Journal of Wind Engineering, and Industrial Aerodynamics, 179: 146-157.
Al-Quraan A. et. al. (2016), Comparison of wind tunnel and on site measurements for urban wind energy estimation of potential yield, Elsevier Journal of Wind Engineering and Industrial Aerodynamics, 158: 1-10
https://doi.org/10.3390/en14164849
Radaideh A. et. al. (2021), Active and Reactive Power Control for Wind Turbines Based DFIG Using LQR Controller with Optimal Gain-Scheduling, Journal of Electrical and Computer Engineering, Hindawi
Radaideh A. et.al. (2021), Rolling horizon control architecture for distributed agents of thermostatically controlled loads enabling long-term grid-level ancillary services, International Journal of Electrical Power & Energy Systems, Elsevier, 179: 106630
Malkawi AMA. et. al. Extending DC Bus Signaling and Droop Control for Hybrid Storage Units to Improve the Energy Management and Voltage Regulation. Inventions. 2022; 7(3):55.
.Al-Masri H. et.al. (2019), Optimal coordination of wind power and pumped hydro energy storage. MDPI Journal of Energies, 12(22): 1-15.
https://doi.org/10.3390/pr10010105
https://doi.org/10.3390/su14106077
https://doi.org/10.3390/su14053075
· The conclusion section has to be consistent with the evidence and arguments presented in the paper. It has to be rewritten in a proper way such that a general idea of your research subject should be initially defined then the achievements and results have to be presented sequentially to achieve the contribution of your research hypothesis.
· The reference section has to be modified significantly with a sufficient number of references.
· The English language has to be checked and revised throughout the manuscript.
Minor Issues:
Please add a list of acronyms since the manuscript has a sufficient number.
· Please try to re-organize Table 3 in a readable manner.
Author Response
Please see my Word file.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper mainly studies the vertical settlement of single pile foundation of offshore wind turbine, which is a meaningful article. There are some minor problems that need to be supplemented and improved by the authors.
The t-z spring proposed by the author considers the influence of torque on the settlement of single pile foundation, which is innovative, but There are some efforts for further improvement in the details of the article, such as Figure 6 shows the settlement of 10MW single pile foundation, but it is indicated in the article as 20MW; and It is suggested that some descriptions of material parameters in Section 2.2 should be added which can increase the persuasiveness.
Author Response
Please see my Word file.
Author Response File: Author Response.docx
Reviewer 3 Report
The paper proposes a t-z spring model with the shear and torsional degrees of freedom to simulate the shear stress along the pile and soil surface. The model could be easily incorporated in to finite element code. The work is of scientific significance. However, considerting the poor presentation, it could not be accepted before the following comments are addressed.
1) The title and the abstract of the paper do not reflect its content. I think the scientific contribution of the paper is the modified t-z spring model, which is supposed to be highlitened in the title. And the settlement investigation of large-scale offshore wind turbines with monopile foundations seems to be the application of the model. But the settlement investigation is rarely introduced in the abstract.
2) In section 2.2, the proposed theoretical model is validated against FEM analysis. However, some details are missed in the manuscript. The FEM model detail is not introduced. And the how the values of those parameters in Line 153-154 are determined is not introduced. It is suggested to add more information to make readers easier to understand.
3) In section 3, finite element analysis of OWT is conducted to demonstrate the effectiveness of the proposed t-z model. However, details of the finite element model is not introduced, and how the proposed modified t-z model is incorporated into the FEM code is neither introduced. It is suggested to add some detail information to make readers easier to understand.
4）Formatting of the paper is very poor. Format of Page 6 should be well checked and corrected.
5) The English writing should be well checked and improved. Such as line 84, 173.
Author Response
Please see my Word file.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The manuscript has been revised based on the provided comments. No further comments.
Reviewer 3 Report
The authors have properly addressed the proposed issues.
