Progressive Collapse of the Base-Isolated Frame Structures Supported by Stepped Foundation in Mountainous City
Round 1
Reviewer 1 Report
The paper presents the continuous collapse resistance performance of base-isolated frames under the two-directional coupled dynamic excitation. While the paper seems to treat a subject of interest and importance, the following issues must be addressed before it can be further considered for publication.
- This paper has numerous grammar and language issues. It is suggested to carefully revise the English for clarity.
- Line 91-94, please clarify this sentence.
- Line 115 “satisfying the assumption of flat section”, do you mean the plane section assumption?
- Line 150-151, “The axial compressive strength and elastic modulus of concrete are measured or standard values. “, please explain how the compressive strength and elastic modulus are measured and what are the standard values?
- Line 171-173, “After the concrete cracks and fails, the flexural bearing capacity of the beam ends is basically lost, that is, the simulation effect after the suspension cable is in good agreement with the test curve, and the error is very small.”, please explain what the suspension cable is.
- Line 186-188, “Using PKPM structural design software, in accordance with the "Code for Seismic Design of Buildings" (GB50011-2011), using a separate design method, a seismic isolation structure model 187 was established and the horizontal damping coefficient was determined”, please clarify this sentence.
- Line 206-207, please explain what C30, HRB400 and HPB300 stand for and the corresponding properties.
- Line 222, should be “DL” and “LL”.
- Figure 6, please explain what alpha, t0, and tp are.
- Line 241, “high-hertz spectrum.” Do you mean high frequency?
- Line 337, Figure 9, missing (a), (b), (c).
- Figure 13, what are the differences between the three subfigures?
- Was the vertical seismic load effect considered in the analysis? How would it affect the results?
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
In the present study a base isolated structure under Two- directional Coupled Dynamic Excitation is examined. The structure is supported by Stepped Foundation in Mountainous. The manuscript is not well written, while the scope, the results and the contribution of the study are not clear. Also there are many typos, while The English used throughout the manuscript needs substantial improvement.
I have a list of some of the comment that should be addressed:
Citations such as “Tsai et [2] al” are written incorrect.
The reference list should be enriched.
Citations such as “LSDYNA”, “Park and Paulay”, “PKPM structural design software”, "Code for Seismic Design of Buildings" and “Pacific Earthquake Research Center” should be added.
Fig 4 demonstrates an elevation view?
The equations are not written in a common way.
The problem presented in section 1.2 is pseudo-static and not a dynamic one. The algorithm using in the verification is the same as in the dynamic analyses that are performed to the following results;
In section 1.2 “Document 8” is referred; Can you explain what document 8 is?
In section 2.2 the steps adopted are presented. It is mentioned that the failure of the supporting bearing is modeled by unloading the internal force Fo in a very short time and then the seismic action is added. This case of analysis what realistic phenomena demonstrates; i.e. the almost instant dynamic failure of a bearing just at the beginning of the seismic action. It should be clarify the differences of the numerical approach steps with the real problem which as I anticipate is different.
A definition of Gauge spectrum is needed.
In section 3.1 is written: “two-story three-span seismic isolation structure…”. However a six story building is studied in the manuscript. Moreover in Figure 5 a 5 storey frame is depicted.
When referring to Supports A, B and F the Figure 5 should be cited.
The captions of the subfigures of all the figures should be clearer.
The name of the frame structure C2K3 is not required because only one stepped frame is considered. Moreover, it may be confusing.
In Figure 9 the axial forces are presented, however the flexural moments may be more indicative for the demands of the beams. Moreover, the subfigures are not number. Furthermore, the last two subfigures of the elevation views of the frame in which case correspond; A legend for the contour is also needed.
What is the main difference of the analysis between the bearing failure and the column failure? Based on what is written the two cases seems exactly the same computationally: “First, adjust the PGA of the ground motion to 0.7g, and then remove the support at 1.5s while inputting the horizontal seismic wave to the X-direction node of the seismic isolation support of the remaining structure” this phase is both used in 3.1 and 3.2.
The comparison of the results, except of section 4, is not clear enough.
Which is the “ordinary ground motion”?
Although it is an interesting problem the manuscript needs substantial improvement in order to be considered for publication. Overall, I cannot support this manuscript for publication of further revision.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The present work conducted the Research on the Progressive Collapse of the Base-isolated Frames Supported by Stepped Foundation in Mountainous subjected to Two-directional Coupled Dynamic ExcitationUgandan region. It can be considered for further process. However, the following points need to be clarified:
- Abstract: Using long sentences complicates the reading of the manuscript. Abstracts should be written in short sentences and easy to understand.
- There are many mistakes in English grammar, word usage, punctuation, and formatting.
- Figures and tables have blurry legends and contents.
- In Figure 7, unit of vertical axis should be the same for comparison. Another, reviewer guess the spectral acceleration is defined as “a”. The authors should be careful for using this nomenclature.
- Why two-dimensional ground motion is applied for a plane frame? This may get some confusions. Please clarify this.
- Time history response given in Figure 8, 9, is of which ground motion? If they are the average value, please carefully consider. Is there any regulation of using the set of these GMs?
- How to design the main parameters of isolated bearing? A detailed explaination is missing.
- Failure condition is missing in this study. Is there any relevant references?
- The fiber element with plastic approach is popular used to model the behavior of the frame structure due to the earthquake loadings. There are some unquoted publications on effects of ground motions on structural performance.
- Tran, T. T., Salman, K., & Kim, D. (2021). Distributed plasticity approach for nonlinear analysis of nuclear power plant equipment: Experimental and numerical studies. Nuclear Engineering and Technology.
- Tran, T. T., Hussan, M., Kim, D., & Nguyen, P. C. (2020). Distributed plasticity approach for the nonlinear structural assessment of offshore wind turbine. International Journal of Naval Architecture and Ocean Engineering, 12, 743-754.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
The paper aims to compare the performance of different base-isolated
structural configurations. The idea is good and reasonable but the manuscript
is written and organized very bad. In this actual state, it is very far from
a pubblication. Only some advices to improve the manuscript are listed below:
1) The title is too long and usually it never begin by "Research on...".
Try to change in more scientific way.
2) The abstract is too long and it should better be written in english.
Moreover, is often used the way of collapse "anti-continuous".
Such term is not conventional, please the authors should be more clear.
3) Also the introduction is very difficult to be followed. The concept of
anti-continuous mechanism and mountains buildings are unclear yet. Please
the authors should try to organize better the introduction.
First: what are the anti-continuous collapses and mountains buildings,
second: what is actually shown in the literature, third: what the paper propones.
4) paragraph 1.2: what is "Document 8"?
5) The description of Figure 1 has to be improved as well as its definition.
6) Paragraph 2.2 maybe could be explained by a flow chart. It is little bit unclear.
For this reviewer it is not evident what is the real objective of the procedure.
7) All equations have not been numbered. Please correct.
8) Figure 7 should be wider described and commented. The input characterists
have been very poor analysed. Try to improve this section.
9) Figure 8 should be better organized. Maybe could be convenient separates
the response under two-way dynamic coupling (black) and the vertical
unbalanced load (red). The unit of measure in the ordinate is missing.
10) In Table 2 the unit of measure is missing.
11) Figure 9 same observation of Figure 8. The legends of the two contour plots,
visualized in the two frames, are missing.
12) For the Figures 10 and 11 same observations of the Figure 8.
13) Unit of measure missing in the Tables 3 and 4.
14) The references have not been written in the correct format.
15) The overall organization and above all the english writing
have to be strongly revised.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The manuscript has been improved after addressing previous comments. It can be considered for possible publication.
Author Response
Thank you for your review. The following revisions have been made to the manuscript: at the beginning of Section 3.2, additional comments have been made on column failure and isolation mount failure; The flow chart for the design of the isolation structure is added. Four references have been added to provide a clearer description of the arch pressing mechanism and the catenary mechanism during the continuous collapse of structures. Some details of the manuscript have been corrected, including the number of subgraphs, some language errors, etc.
Reviewer 2 Report
The response to the reviewer is not very informative as many of the answers are not highlighted in the manuscript. However, the manuscript has been improved after the changes that have been made. There are few more comments that have to be addressed.
1)The response to my previous comment about the difference of the analysis between the bearing failure and the column failure should be added also to the manuscript if it is not added already.
2)The subfigures are not numbered in every figures.
3)In the two last subfigures of Figures 12 and in Figure 15 a color bar should be added.
4)The reference list should be enriched.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
- Check Figure 7a-b, unit should be the same. A better comparison can be achieved by plotting all ground motions in one figure.
- A simplified process of isolated bearing design should be included. Here, which seismic base isolation is considered and how to design.
It look like the Lead Rubber Bearing (LRB) is adopted in this study. Based on the structural characteristics, the relevant formula to determine the global stiffness of the system should be provide?
- The reviewer can not find the updates
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
The paper has been sufficiently improved based on the observations raised by this reviewer. It can be tentatively accepted for a possible publication.
Author Response
Thank you for your review. The following revisions have been made to the manuscript: at the beginning of Section 3.2, additional comments have been made on column failure and isolation mount failure; The flow chart for the design of the isolation structure is added. Four references have been added to provide a clearer description of the arch pressing mechanism and the catenary mechanism during the continuous collapse of structures. Some details of the manuscript have been corrected, including the number of subgraphs, some language errors, etc.
