Behaviour of Concrete-Filled Double Skin Tubular Short Column with Plate Stiffeners Welded Intermittently under Axial Compression

Round 1

Reviewer 1 Report

A performance of concrete-filled double skin tubular column under axial compression was discussed in this paper. 20 column specimens were tested applying monotonic compression with parameters of the shape of column cross-section, the size of stiffener and the weld spacing of the stiffener to outer tube. Finite element analyses were conducted to examine the test results and additional parameters. And discussion was made on effects of the size of stiffener, the weld spacing, and the column shape.

 

I think that the experiment results and the examination based on FE analysis in this paper are useful for developing the CFST columns. However, I have some questions and comments as follows.

 

Page 5, Lines 154-159:

Regarding the strength of concrete and Poisson's ratio of concrete and steel, please make clear whether those are test results or predictive values.

 

Page 8, Lines 211, 215, and 216:

Please explain what "the average displacement length" is. How do I find that the lengths are 15mm and 30mm?

 

Page 11, Line 292:

Please explain what "fcu" is.

 

Page 12, Line 295:

Please explain what "A0" is.

 

Page 21, Lines 438-440:

“The strength of the CFDST increases because the additional steel stiffener increases the total cross-sectional area of steel, leading to higher ductility and confinement effect to the CFDST.”

I cannot understand because the strengths of CFDSTs are almost the same even if the thicknesses of stiffeners are different in Figures 15 and 16. I think that increasing of the thickness of stiffener makes the total cross-sectional area of steel large.

 

Page 23, Line 468; Page 24 Line 470:

In Figures 17 and 18, the results of specimens with 2.8 mm of stiffener’s thickness are larger than those with 2.3mm. But, the strengths are almost the same even if the stiffener’s thickness are different in Figures 15 and 16. I think there is a lack of consistency in your consideration.

 

Page 25, Line 511; Page 26; Page 27, Lines 514-516:

In Figures 19 and 20, and Table 10, the load of square column is compared with the load of circular one. But the cross-sectional area of the square column is larger than that of circular one. Because you are discussing the effect of shape here, it is better to examine the strength per unit cross-sectional area.

 

Page 27, Lines 526-531:

There are the ratios of 57.49 %, 44.96 %, and so on. I think that these are calculated by using the values of “Pu,Exp” a digit of which is three in Table 5. Please consider a significant digit in calculation of the ratios.

Author Response

I've attached all my answers based on the reviewer's comments in MS Word format. Thank you.

Author Response File: Author Response.pdf

Reviewer 2 Report

1. Too many grammar and language errors. For example :

• line 41: will reduce change to will be reduced
• line 151: the heading of the table specification change to should be specifications.
• Line 180: The linear change to linear.
• Line 254: the aim is to do change to the aim is to perform.

2. The advantages and disadvantages of the studied column system are not mentioned. The author should add a detailed description of the aspects of this system and the difference between this system and the filled tube column system. The potential of using this system. You should also add a historical background of this system.
3. The abstract section is not clearly written, the number of samples is misleading as you mention eight, and in the other parts of your paper, ten for each group which I think is the right number.
4. In the introduction section, you mention for example “hollow ratio” which is not explained.
5. Some comments given in the introduction section are not clear, for example in line 74: which has extra inner steel with a shorter length.
6. In the experimental program, you did not give any details of the specimens' material properties, manufacturing details, photos during casting, casting direction, welding thickness, and so on. (fy, fc’,……) material proportions, curing process,……….
7. Some abbreviations are not explained as CFST in line 103.
8. In table 1, you are using “the heading flat bar”, which is not mentioned in any other part of your paper. You should be consistent. Also, too much-repeated data in Table 1.
9. What are the longitudinal dimensions of the stiffeners, is it continuous.
10. You should explain how you calculate the stiffener forces and how you design the weld size. I think the welding is not enough in these specimens.
11. Captions should be followed by tables or figures on the same page. Check Table 2 for example.
12. You should explain and comment on the place of buckling in each column.
13. What about concrete inside the tube, what about the inner tube.
14. The weld spacing variable should be based on the forces induced in the welding.
15. The presentation of the results is not clear.
16. The details of the finite element should be tabulated and figures of the model should be given to show all the elements, contacts, and so on.
17. Equations are given in a confusingly way, please rearrange.
18. You mention that the data used in your analysis are based on the experimental data you collect and you should give these data in a table.
19. Again the number of specimens is different, in line 383: you are talking about 18 and 5 ??????
20. How did you identify buckling in your work? The curves you are showing do not show any buckling failure.
21. Also, the buckled photos of the columns in Figures 13 and 14 are not matching with the smooth curve you are showing. I think you need to check all the aspects of the model.
22. The obtained conclusion should be limited to these specimens.
23. You should add an equation for the load capacity of this column type.
24. One of the main conclusions is not justified right and should be checked, “From the parametric study, the closer the weld spacing, the stronger the stiffened The thickness of the plate stiffener is significant in the ultimate strength of the stiffened CFDST. For the optimum strength of CFDST, the stiffener’s width is advised to use 18 mm stiffener out of the choice of 12 mm, 18 mm, and 25 mm.”, the authors mentioned that this is due to due to the reduction of the concrete area. This needs to be checked and the authors should find a logical explanation for this.

Comments for author File: Comments.pdf

Author Response

I've attached all my answers based on he reviewer's comments in MS Word format. Thank you.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments to the author

1. Still some language and usage errors. For example :

• In the abstract and generally, you have to explain abbreviation when they first appear

 in the text.( as line 11 in the abstract)

• line 52: by welding it with stiffeners change to by welding stiffeners to it.

3. In the introduction section, Still the meaning of hollow ratio is not given, you to explain hollow ratio.
4. Explain what you mean by ductility in the introduction.

 

 

Author Response

The response to all comments from Reviewer 2 is shown in the list of comments and responses and attached revised manuscript. In conclusion, we appreciate all the insightful comments. We have done our best to make the recommended amendments. Thank you for the time and effort to help us improve the writing of this paper. We hope that you will give kind consideration of the revised version of this paper.

Thank you.

 

Point 1: Still some language and usage errors. For example:

• In the abstract and generally, you have to explain abbreviation when they first appear in the text (as line 11 in the abstract)

Response 1: The author has rectified concrete-filled steel tubular (CFST) in line 11-12.

 

Point 2: line 52: by welding it with stiffeners change to by welding stiffeners to it.

Response 2: The author has rectified it in line 60.

 

Point 3: In the introduction section, Still the meaning of hollow ratio is not given, you to explain hollow ratio.

Response 3: The author has added a line of description for hollow ratio in line 43-44.

 

Point 4: Explain what you mean by ductility in the introduction.

Response 4: The author has added explanation in line 54-58.

Author Response File: Author Response.docx