Experimental Studies on Seismic Performance of UHPSFRC-Filled Square Steel Tubular Columns

Round 1

Reviewer 1 Report

• How to confirm the 1/2 scaled specimens can be represented the actual full scale results?
• Update the citation to the more recent references year.
• How author choose 3% volume ratio of steel fiber? Is there any reference?
• How author obtain 8 MPa for the tensile strength of concrete? Normally, the value for tensile strength is about 10% lower than compressive strength.
• How author design UHPFSRC specimen? Is there any specific standard to be referred? Eg: Eurocode, BS, etc
• Unit for the dimensions of specimens in Figure 1 must be clearly stated. Eg: m, cm, mm
• Failure modes in Figure 6a can be categorized as bulging failure. Buckling failure occurs in long columns where the columns displaced laterally or horizontally. Please use consistent term in the paper.
• How author define the severe buckling rate for specimen S2 and S5?
• Check spelling for the subtitle in 3.5 and 3.6. Do author mean Strength degradation?
• How author treat the linear softening for concrete constitutive models? What is the coefficient or parameters that used to degrade the concrete stiffness during softening?
• It is suggested to state all the values of the parameters, coefficient that used to simulate the UHPSFRC in the table form.
• Check label in Figure 15. What is UHPCFST? What is section mash? Is it section mesh?

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Manuscript ID: buildings-1730003  

The article presents the experimental studies and numerical analysis on seismic performance of ultra-high performance steel fiber reinforced concrete (UHPSFRC) filled square steel tubular columns.  

The article is well written and clear.   Few comments are given below;  

Abstract need to modify with quantitative results.  

Introduction is well written, however there is still need to improve the latest literature on analysis part.  Following articles are suggested as well.  

Shabani, A., & Kioumarsi, M. (2022). A novel macroelement for seismic analysis of unreinforced masonry buildings based on MVLEM in OpenSees. Journal of Building Engineering, 104019.  

“Strengthening of Shear-Critical RC Columns by High-Strength Steel-Rod Collars”, Eng. J., vol. 24, no. 3, pp. 107-128, May 2020.    

Scientific reasons are missing for the selected specimens.  

Line 149 and 150, no reasons are provided for the observed failures. 

Line 345 and 346, how the element sizes were selected.  

Figure 17, the stiffness of FEm results is higher, there is need to discuss this point in the text.          

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

REVIEW

on article

 

Experimental studies on seismic performance of UHPSFRC-filled square steel tubular columns

 

Yunbiao Luo, Yucai Zhao, Yuebo Chen, Jiabao Yan and Xuchuan Lin

 

SUMMARY

The presented article is devoted to the actual topic. In particular, the article presents experimental studies and numerical analysis of the seismic characteristics of ultra-high-performance steel fiber-reinforced concrete filled with square, steel, tubular columns. This is a very urgent task in view of the development of modern construction and hard conditions in various parts of the world.

The results of the study can be useful for construction in a wide variety of conditions and areas of the globe. The article attracts attention from a positive point of view. A good methodological apparatus and a logical sequence of the studies performed, a large number of visualization elements are noted. Obviously, the authors have good experimental capabilities and deep skills in conducting research on the topic of the article.

The results obtained by the authors are also useful and can be applied practically in applied construction. From the point of view of novelty, the article is also original and deserves attention, and may also interest readers of Buildings.

However, with all the advantages of the article, it also has some drawbacks that need to be corrected and will be discussed below.

 

COMMENTS

1. The Abstract presented by the author does not fully reflect the content of the article. In particular, it is presented very sparingly and should be supplemented with the problem that the study solves, and it should also be done in accordance with the requirements of the Journal in terms of the Abstract structure.
2. Also noteworthy is not only the size of the Abstract and its lack of completeness, but also the lack of a quantitative expression of the results achieved. This should be reflected in the Abstract.
3. The section "Introduction" is rather concise and, based on such an introduction, it is impossible to draw an unambiguous conclusion about the expediency and necessity of conducting the study. The section "Introduction" needs to expand the literature review, increase the number of sources, and first, it is necessary to give preference to sources whose year of publication is not earlier than the last 5 years, devoted to the current state of the issue of fiber-reinforced concrete for seismically hazardous areas. In this regard, the "Introduction" section needs some improvement both in terms of the quality of content and in terms of the number of analyzed sources. Only after that it is possible to talk about the specific novelty of the study.
4. In Section 2, attention is drawn to a sharp transition to the description of the experiment, while the program of the experiment is missing. It would be necessary to make a smoother transition from Section 1 to section 2 and add an experiment program.
5. Table 1 presents the design parameters and material properties for manufacturing prototypes; however, it is not entirely clear why these particular design parameters and material properties were taken. A more detailed explanation is needed, describing Table 1. Then it will become clearer to the reader why these samples were chosen for manufacturing high quality columns for seismically special conditions.
6. Figure 1 looks somewhat difficult to read due to the large number of dimensions applied to it. Perhaps the drawing should have been enlarged, and the dimensions applied in more detail. Some of them are superimposed on each other and look unnecessarily compressed. In principle, for a clear understanding of the process in terms of the design and technology of the columns under study, it might not be necessary to provide such detailed drawings. It would be enough to insert a photograph or a 3D model, or to fulfill the specification of the elements and dimensions presented in the drawings.
7. Figure 3 deserves special attention. Of course, it is presented in sufficient detail, however, it may also need to be scaled up due to the poor visibility of the fragments of the figure.
8. The photograph shown in Figure 4 probably needs to change the captions depicted in the figure itself. It may be worth placing numbers in the figure and transfer the designations of numbers to the caption under the figure to clarify the fragments of the image in the figure.
9. Figure 5 looks very small and needs to be scaled up a bit, as well as improving its quality.
10. Figure 6 deserves special attention. The authors quite interestingly approached the presentation of the stepwise process of changes occurring in the failure mode of square, steel, tubular columns filled with high-performance concrete. It would probably be possible to include the most characteristic stages in the figure caption. Then the drawing would become even more perceptible for readers. However, this can be left to the discretion of the authors since the figure is already presented in detail.
11. There are quite a lot of graphic elements in subsection 3.2, but their decoding requires more textual interpretation. The same remark applies to subsections 3.3 and 3.4.
12. The finite element method given in section 4 is presented rather succinctly and requires more detailed analysis.
13. In the figure captions to Figures 7 and 17, it is necessary to add the decoding of parts (a), (b), (c), (d), (e).
14. The unacceptable absence of the "Discussion" section is noteworthy. The fact is that due to the absence of the "Discussion" section, it is impossible to evaluate the comparison of the results obtained with the results of other authors. The authors of the article need to complete and add the specified section. Without this, the article cannot be assessed in terms of novelty and significance.
15. The 'Conclusions' are succinctly presented and, in principle, perhaps only need to be more reflective of the prospects for future research on the topic, as well as the development of existing insights received.
16. Noteworthy are the small number of shortcomings that are present in the article and small errors in the English language, which in principle is not critical.
17. In general, the reviewer's conclusion on the article is mostly positive, but these shortcomings must be corrected, and the manuscript should be submitted for re-reviewing.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

All my comments were considered and corrections made in the article's text. I recommend the article for publishing.