The Anti-Overturning Response of Tripod Bucket Foundation for Offshore Wind Turbines
Round 1
Reviewer 1 Report
The article entitled "The anti-overturning response of tripod bucket foundation for offshore wind turbines" was reviewed. In this article overturning capacity of tripods (used for installing wind turbines in offshore areas) against shear forces has been investigated experimentally and numerically. The subject of the research is very practical. But there are shortcomings in the way of implementing experimental modeling and numerical calculations. I think the following suggestions can improve the article:
1- In the abstract please briefly mention the numerical method and software name.
2- In the abstract, the result of the research is mentioned in a general form, such as: "It is also shown that varying bucket diameter or skirt length (i.e., aspect ratio) has a prominent impact on load bearing characteristics"
The most important achievements of the research should be presented in the abstract. These achievements should be clear and specific. The mentioned achievement should be specific to this research (not a repetition of the topics raised in previous research). If this research aims to confirm outcoming of previous research (e.g. Refs [12,13]), it should be clearly mentioned in the abstract.
3- The review of the literature is not sufficient in terms of quantity and quality, and the previous references are mentioned in a general and vague way. In the literature review, at least for the most relevant references, it should be stated: 1- which researchers, 2- for what purpose, 3- with what method, 4- did what, and finally 5- what result was concluded.
4- In lines 51 and 52, it is mentioned that "Limited model tests were reported in the literature with a focus on the overturning moment-rotation response of tripod bucket foundations under lateral loads"
What is the point of this model test that was not achieved in previous research such as references 9 to 11? And what was the reason for conducting the model experiment (other than validating calculation results, that could be performed with the field data presented in Refs [7] and [32])?
5- In lines 65 and 66 it is said "very little literature is available on comparison studies of anti-overturning responses for tripod bucket foundations both in sand and clay" But the related references are not mentioned at all. After all, The innovation of this research and its difference from previous research has not been determined.
6- In this study, the mechanical properties of the seabed material have an essential role in the anti-overturning resistance of the tripod. For this reason, why model experiment doesn't perform with seabed materials (e.g. soft clay and sand) directly?
7- In Table 3 please add the mechanical properties of the seabed materials.
8- It is stated in line 76 that: a "well-calibrated numerical model in engineering scale was adopted”
Calibrating a numerical model means that its empirical coefficients have been adjusted to reduce its mismatch with experimental data. In this article, no calibration has been performed. If this calibration is done in another reference, cite it directly after the sentence.
9- It is stated in line 124 that: "The horizontal force was loaded in 5 N increments and maintained for 10 minutes." in line 140 it is stated that: "The ultimate capacity of the foundation is 54.2 Nm under TBT and 39.2 Nm". Considering that the results obtained from the laboratory model can have a practical aspect:
What is the ratio of the forces applied to the experimental model to the shear force that can be applied to the prototype by water currents or wind (or a combination of both) in the sea? The resultant of aerodynamic and hydrodynamic shear force enters which part of the wind turbine (base or mast) and as a result, what is the amount of overturning moment for the prototype of three legs? If this calculation has been done, what dimensionless numbers have been used for hydrodynamic and aerodynamic calculations?
10- No standard was mentioned in off-shore wind turbine foundation design and its over-turning moment bearing capacity. (especially in the literature review).
11- Please show the dimensions of the computing domain in Figure 10.
12- For the numerical method, the results of domain study and mesh study should be presented.
13- The weight of the turbine structure (mast, rotor, etc.) can affect the resistance of the tripod against overturning moments. It is suggested to include this force in modeling and calculations.
This reviewer appreciates the authors' efforts. Looking forward to your reply.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Line 32: Is GW the correct unit ?
Lines 81 to 94:
Given the geometrical scale 1:100, wat are the scaling laws for masses and weights, stiffnesses, etc.
And explain the weight 7.36 kg for the model and 700 tons for the prototype.
Is there any scale effect on the sand grain sizz?
Line 91: “bucking” should be “buckling”.
Line 156 to 168 and Equations (3) and (4):
It should be stated that the results are first order results obtained for small displacements and that v1>0 upward(z<0) and v2>0 downward(z>0).
Could you please check formula (3), numerator is (v1*l1+v2*l2) or (v2*l1-v1*l2) ?
Line 172: please include an article “the rotation center”.
Line 221: “coupled with two model buckets rigidly” or “rigidly coupled with two model buckets”?
Line 246: “in in” should be “in”.
Figure 11: the steepness of the numerical and experimental curves looks very different at rotation angle <0.25 degrees. What could be the explanation?
Lines 293-294: introduce a reference for Figure 5
“The ultimate anti-overturning bearing capacity of a tripod foundation was determined by the tangent intersection method mentioned above (Figure 5), as illustrated in Figure 13b.”
Line 425: ?′and s_u should be clearly defined. Why two different non-dimensional variables are used for sand and soft clay for comparison?
Question: Considering figures 13 and 14, it appears that L/D = 0.75 seems favourable. In this case the support polygon looks maximum in size.
Could the support polygon of the overall geometry be a leading parameter?
General comment:
The pictures and photos qualities are not good. (Figure 1, 2, 4.b, 4.c, 9, 10).
A list of variables could be introduced.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
There is no need for further comments of the reviewers.
