Effects of Cross-Section Type and Degree of Utilization on Failure Time and Temperature of Cold-Formed Steel Column under ISO Fire

Round 1

Reviewer 1 Report

The title of the manuscript does not clearly show this work is for fire resistance

The first eight (8) sentences in the abstract read like a general intro providing well-known information. Starting with “An investigation…..”, the abstract technically started. Not very significant information is provided after that. The whole abstract needs to be re-written.

Section “2. Steel Column Fire Test” should be part of the introduction and lit review. This section title should be eliminated.

Grammar – a few grammatical and spelling errors were found. Please review the English again.

It is not clear how the BU section was built-up. Figure 1 is not sufficient. Additional figures are needed to show the column set-up and loading

It is not clear how the vertical load was applied. Also, was there any lateral loads?

The abstract states, “The results showed that shape did not give any significant effects on the critical temperature of the CFS columns,” whereas line 128 states, “Column shape could give a significant effect on the temperature and failure time of a column.” Plese clarify/re-write.

Figure 3(b) is not clear. Not sufficient information/discussion is provided on how it was developed and its relation to Figure 3(a).

Line 215 - inadequate and conservative ?? the reviewer is not clear what the authors mean by this. it sound like it is contradictory to itself.

this reference was utilized heavily in this manuscript - Craveiro et al., 2014): Craveiro, H. D., Rodrigues, J. P. C., & Laím, L. (2014). Cold-formed steel columns made with open cross sections subjected to fire. Thin-Walled Structures, 85, 1–14. It not clear to the reviewer how much of this manuscript repeated what was already concluded in this reference. especially since it was referenced a few times in the Experimental Results section. Authors need to clearly show what is new in their manuscript, especially in relation to Ref # 1.

Figures and discussion need improvement.

References 2 and 5 are incomplete.

Author Response

The all answer of the reviewers are attached in the file.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper presents outcome of a study carried out to investigate fire response of channel sections made of cold formed steel. This study gives particular emphasis on the geometrical effects and magnitude of applied loading upon fire resistance of such channels. For this paper to be suitable for publication, the following items need to be considered.

1)     Line 37, used “in estimation” as opposed to “in estimated”

2)     Line 40, “Cold-formed steel (CFS) is a very sensitive material due to its thinner thickness that it is perceived to have no resistance when on fire”. This statement is not correct and needs to be revised. In fact, fire resistance ratings for CFS are available in industrial reports and codal provisions in some countries (i.e. Canada, Russia, Europe etc.).

3)     The introduction is very short and lacks information on studies carried out on fire resistance of CFS as well as on the problem of fire in buildings in general. Please strength the introduction by carrying out a proper literature review. Some of these articles can be used and the authors are encouraged to loo for other studies as well.

a.      https://doi.org/10.1016/S0263-8231(03)00002-8

b.     https://doi.org/10.1016/j.engstruct.2018.06.030

c.      https://doi.org/10.1016/j.tws.2018.12.030

d.     https://doi.org/10.4028/www.scientific.net/AMM.353-356.2313  

4)     What were the properties of the fire coating? What is limiting maximum temperature/withstand duration?

5)     Is the acceptable limit for furnace to follow standard fire 15%?

6)     What were the boundary conditions of the columns? Fixed-fixed? Or pinned-pinned?

7)     Is the time (x-axis) in Fig. 2 in seconds or minutes?

8)     Did the authors carry out any testing on coupons to measure mechanical properties of CFS at ambient or at elevated temperatures? If so, please discuss the outcome of such tests.

Author Response

The answer of the reviewer is in the file attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Review Comments on Manuscript Metals-540378

“Effects of Cross-section Type and Degree of Utilisation on Failure Time and Temperature of Cold-formed Steel Column under ISO Fire” by F. Muftah et al.

This paper investigates the possible impact of the cross-section geometry on the buckling behavior of cold-formed steel columns when subjected to ISO Fire. This is a topic of interest to researchers and practitioners when addressing the behavior of cold-formed steel structures exposed to fire.

While this paper addresses an important topic, the assumptions, testing approaches and conclusions in this paper are unclear in several cases. The unique contribution of this work in providing insight into the important problem of performance of cold-formed steel columns subjected to fire is also not clearly specified. In addition, the quality of English language usage is not at an acceptable level for a research journal.

While the English language usage can certainly be fixed by a thorough editing (which should preferably be done before the paper is submitted for review in the first place), in the opinion of this reviewer, this paper can only be published if the authors provide clear and comprehensive details of their experimental study of cold-formed steel columns in fire and address the following comments.

In the opinion of this reviewer, the goal of reporting the results of a unique experimental study is twofold: 1) to present carefully the experimental data for future verification and calibration of computational tools, and 2) to place the findings in perspective with regard to observations from past studies. The authors have spent the entire paper addressing the first goal of presenting the test data and the observations (even though they have left many useful and important details about their testing program), but have not properly addressed the second goal. The authors should provide a clear discussion on how the observations from their column tests compare with those from simplified tests conducted under either standard fire or constant temperature conditions. This discussion enhances the value of the paper to the readership. The authors should revise the introduction section for both clarity and accuracy of the content. For example, it is not clear why the authors referenced literature on stainless steel in fire. The authors should also provide more in-depth discussions about previous relevant research. It seems that the conclusions/observations cited in the abstract/conclusion section are pretty much the same as observations from past studies. The authors should mention conclusions/observations that differentiate the findings of their study from those of the previous ones. In other words, the authors should try to focus on what they observed in their test that could not be seen from other tests in past studies. More importantly, authors should indicate if the observations from their experiments confirm those from tests conducted under simplified/uniform temperature conditions. The authors should provide more details about their experiments on cold-formed steel columns in fire (For instance, there is no clear information on the location of thermocouples along the height of the columns or how thermocouples were attached to the column specimens during fire tests). Unfortunately, the authors have only provided very general and incomplete information about the experiments. More in-depth discussions about different assumptions and difficulties/problems encountered in conducting the experiments can help the reader to better understand/interpret the experimental results. The authors should provide information on the chemical composition of the cold-formed steel used in the experiments since chemical composition can have a significant influence on the thermal and mechanical properties of cold-formed steel shapes. This is a very essential information that is currently missing from the paper. The authors should also present more information/details on how the stress-strain curves shown in Fig. 3 were obtained (e.g. experiment type, duration of each test, etc.). The authors included pictures of failure modes observed for cold-formed steel columns following the fire tests (Fig. 9). These pictures are shown without reference to the location of thermocouples. The authors should also present the temperature history of the column specimens during each test along with the location where these histories were recorded. Again, such information is really useful for future studies and adds value to the paper.

Author Response

Thank you for your comment and review. It really helps to produce a good and quality works. 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Thank you for addressing all comments; this helped. 

Author Response

Thank you for your comment and review. 

Author Response File: Author Response.pdf

Reviewer 3 Report

This reviewer would like to thank authors for addressing his/her suggestions for improvement.