Round 1

Reviewer 1 Report

1-Major corrections: 

1.1-You should have a reference point to compare your ''optimized model'' against. You have not provided this. this is a major issue. 

1.2-In addition, the paper structure, and presentation shall be enhanced (methods are too long, results are too brief).

1.3- Lines 121-124, From where did you get this and what are those values? You have not provided this!! this is a major point.

1.4-References?!!!! without them, your method cannot be accepted. 
Reference assumptions, equations, and raw data (annual average wind speed, nominal wind speed, cut-out wind speed, and 123
extreme wind speed.)

-------------------

2-Minor comments

2.1- ''Results show that the optimized PCSH wind turbine tower can be an economic alternative for wind farms with lower LCOE requirements. In addition, compared with the traditional particle swarm optimization (PSO) algorithm..." Please give numbers 

---------

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper concerns design process of a hybrid prestressed concrete (PC) and steel tower for wind turbine. The design formulas for determination of loads values, assessing resistance of the steel and PC sections and serviceability ultimate states are clearly presented. Finally, the design of the tower is optimized using a meta-heuristic algorithm, i.e. the parallel up- dated particle swarm algorithm. The paper is well-written and can be interesting to other researchers. In my opinion, it suites profile of the journal very well, since the innovative approach was applied in the design process of important structure. However, I have a few more and less important remarks and doubts.

• line 17 – What are “mechanical costs”? The sentence is rather poor in terms of the language style due to double “and”.
• line 53 – I am not sure whether the statement “servicing life of PC is much longer than steel” is always true. It is a complex issue, since the durability of PC strongly depends on execution quality and proper maintenance.
• line 82, 539 and others different names are used for the same function. I think “objective function” is correct name.
• line 100, 313 – I think that “displacement” would be better than “deformation”.
• (1)-(3) – Is the unit correct? F = C V^2 Pi R^2 = [1*(m/s)^2 * m^2 =! N]. Do the coefficients C have a unit?
• line 163 – How factor beta is calculated or what value is assumed? In Eurocodes procedure of calculation such factor is quite complex.
• line 222 and others – I am not sure whether the word “strength” suits context well. In my opinion, “strength” is mechanical parameter of material (like concrete tensile strength). I believe the authors mean “load capacity” or “resistance”.
• line 225 – Maybe “compressive stress f_cu” instead of “compression f_cu”?
• 43 – Units shall be given in such types of equation.
• line 316 – What is interpretation of the angle theta? Is this the angle thetha slope of the tower, i.e. angle between the horizontal direction and the line which connect the base and the top of the tower? Or is it the rotation angle of the top section? The former angle is not characteristic of the top deformation, but the whole structure, so in this situation the heading is misleading.
• line 327 – c(x) is vector of constraints functions? It is not clearly stated.
• line 491 – I am quite confused with the statement “minimum concrete compressive stress is larger than zero”. If the stress is larger than zero, concrete is subjected to tension, which is not desired in PC structures. In Fig. 9(b) is the red line connected with criterion given by equation (36)? In equation (36), there is the limitation that sigmac>0. It makes sense, since PC sections shouldn’t be subjected to tension. I can be wrong – in such situation, I would like ask the authors to discuss this issue wider.
• line 516 - Maybe “natural frequency” instead of “the first order frequency”?
• Lots of contributions in the field of meta heuristic optimization algorithms and their applications to structural designing were done by Prof. Ali Kaveh. Maybe it is worthy to cite some of his paper or his book from 2018?

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have addressed all of my comments successfully. I don't have any other comments. My recommendation (Accept in present form). 

Author Response

Response to Reviewer 1 Comments

Point 1: The authors have addressed all of my comments successfully. I don't have any other comments. My recommendation (Accept in present form).


Response 1: Thanks for the positive comment from the reviewer on the revised version of the manuscript.

Reviewer 2 Report

The authors responded to all my remarks. In my opinion, the paper is of good quality and can be published in "applied sciences". I have one small doubt concerning negative utilization ratio. 

I suppose that for windware side, the condition, which is checked is as follows: sigma<f_ctm (concrete tensile strength). But I couldn't find such condition in section 3.2. Probably, that is why, I was confused after first reading. I would like the authors to add such condition, if I am right. 

Besides, if the whole section is subjected to compression the condition fc<sigma is still valid. I think, that when we allow the possibility of tension in PC section, an additional condition concerning crack width should be checked. Or we can assume, that no tension is allowed, but in such situation we are not able to obtain negative utilization ratio. 

I have no further remarks.

Author Response

Please see the attachment.

Author Response File: Author Response.docx