Seismic Design Procedure for Low-Rise Cold-Formed Steel–Special Bolted Moment Frames

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper considers the problem of extending the using of CFS-SBMF to multi-storey low-rise buildings. It focuses on an experimental and numerical verification of a new moment connection between beams and columns that can be utilized in multi-storey building frames. The presented experiments and analyses are interesting and manuscript is well written. Therefore I can recommend it for publication in Applied Sciences after including some comments that could improve the quality of the article:

-        The content of the article shows that the experimental and numerical tests were carried out for one bolted joint configuration in the connection as shown in Figure 6. Were other bolted joint configurations also verified? How does the change in bolted joint configuration affect the obtained results? It would be good to post a comment on this matter. 

-        The content of the columns: "Column", "Beam", "Plate" in table 1 regarding samples is confusing and it would be good to change the table layout. The symbols used in the columns, if I understand correctly, are constant for all samples, but their notation is misleading because each element of the description is in a separate line, which may be difficult to understand for a potential reader. 

-        The descriptions in the photos in Figures 4, 5, 12, 13, 14, 15 are illegible and should be corrected. 

-        Figure 16 - The value of the displacement in slip&bearing and in beam is over 10 cm. This seems to be a lot for the analyzed beam span. It should be provided with an additional comment. 

-        Line – 345 - The term "DBE level" was explained in the introduction in line 64, but I suggest repeating it here for better understanding. 

-        Lines 354-358 - In this paragraph, it is not entirely clear how the overstrength factor system was determined. The equation appears only in table 6. Introducing the formula also in this paragraph would dispel doubts. 

-        The article does not provide all data values ​​that were taken into analysis, e.g. the value of elastic stiffness (line 386). It makes replication of the results by other researchers challenging.

Comments on the Quality of English Language

The paper should be proofread again to improve the English language, eg.:

-        in some paragraphs, individual sentences are separated by a semicolon instead of a full stop, which makes it a bit difficult to analyze the text. It would be good to correct this.

-        there are a few typos in the article, e.g. lines: 434, 441.

Author Response

Attached, please find the responses to the comments.

Thank you very much.

Atsushi

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The study proposes a new moment connection detail and a design procedure to ensure bolted connections, rather than beams or columns, have the capacity to withstand seismic forces. Full-scale cyclic testing verifies the proposed design procedure for bolted connections. A comprehensive evaluation, including nonlinear dynamic analysis and Incremental Dynamic Analysis (IDA) per FEMA P695, assesses the system's performance under seismic excitation in multi-story low-rise CFS-SBMF buildings.

The research was meaningful and enriching, but revisions are required before the paper is published.

1.      The introduction of the article does not fully explain the shortcomings of the current research, the author should explain in detail so as to reflect the significance and innovation of this paper.

2.      To better illustrate the improved connection method, it is recommended to zoom in on specific details in the 3D schematic in Figure 2.

3.      The text mentions experimental parameters such as connection type, surface grade, and beam position. What criteria were used to select these parameters, and were the real working conditions and environment of the structure taken into account?

4.      For the bolt strength used in the specimens, it's important to explain the rationale behind selecting this particular strength and whether it aligns with the requirements of the actual structure.

5.      The assumption of a 4.0% drift ratio as an acceptable value for interstory drift in determining the gap between the column and beam ends needs to be evaluated by the author for its reasonableness.

6.      Discussion of the test results may require further elaboration. For example, analyzing the reasons behind phenomena such as lateral torsional buckling and local buckling of the beam; comparing the advantages and disadvantages of different types of bolt connections and their impacts on structural performance and load response.

Author Response

Attached, please find the responses to the comments.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Recommend to accept.