Experimental and Numerical Investigation for Seismic Performance of a Large-Scale LNG Storage Tank Structure Model

Round 1

Reviewer 1 Report

The work contains many deficiencies and inadequacies and cannot be accepted in this condition.

The title does not correspond to the content of the work. Liquefied gas storage will only appear in the literature review and in the calculation of the equivalent mass (line 172).

There are two main parts to the work:
1)experimental study of the rescaled (reduced) model and its MES analysis
2) MES analysis of the unscaled object
The second main objection is that the two parts do not connect in any substantive way.

There is a lack of basic data on the MES analysis, e.g. what material model was adopted for the concrete, what for the seismic isolation elements? How was the subsoil modelled? What pile lengths were adopted for the analysis?

There are no drawings showing the placement and numbering of the transducers. Without this, it is not possible to qualitatively assess and compare experimental and computational results.

There is no definition of what is meant by " overturning bending moment".

 

Author Response

Dear Editor,

 

Manuscript ID: applsci-1846107

 

Type of manuscript: Article

 

Title: Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model

 

Authors: Zengshun Chen ¹, Zhengang Xu ^{1, *}, Lingxiao Teng ², Jun Fu ^{1, 3}, Tao Xu ^{1, 4}, Zhihang Zhao ^{1, *}

 

 

Submitted to section: Civil Engineering, Seismic Performance of Concrete Structures: Theory, Modeling and Applications

 

Please find attached a revised version of our manuscript, 'Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model', which we resubmit for the consideration of publication in Applied Sciences.

 

Thank you and the reviewer for the valuable comments, which enabled us to greatly improve the quality of our manuscript. According to the comments, we have made extensive modifications to the original manuscript. The modified texts were highlighted in the revised manuscript. Enclosed with this letter, in the following pages, are our point-by-point responses to each reviewer comment. We sincerely hope this manuscript will be finally accepted for publication.

 

Thank you for coordinating the review processes of this manuscript.

 

Yours truly,

 

Zhengang Xu

 

School of Civil Engineering,

Chongqing University

Shapingba District

Chongqing 400045, China

Tel.: +852 23588763,

Fax: +852 23581534.

E-mail: [email protected]

 

Point-to-point response: Reviewer 1

1. The title does not correspond to the content of the work. Liquefied gas storage will only appear in the literature review and in the calculation of the equivalent mass (line 172).

Response: Thank you for your comments. Firstly, the title of this article is "Experimental and Numerical Investigation for Seismic Perfor-mance of a Large-scale LNG Storage Tank Structure Model". The content of this article includes shaking table test and numerical simulation, this title can reflect the main research content of this article. Secondly, this paper studies the seismic performance of large LNG storage tanks under earthquake action, and the full article focuses on the seismic response of LNG storage tanks rather than the seismic response of LNG. Therefore, this paper only mentions LNG in the literature review and isolation bearing design. Finally, the research object of this article is the LNG storage tank. The impact of liquefied natural gas (LNG) on LNG storage tanks was not considered in the study. On the whole, the authors believe that this title fits well with the research content of this article.

 

2. There are two main parts to the work:

1)experimental study of the rescaled (reduced) model and its MES analysis

2) MES analysis of the unscaled object

The second main objection is that the two parts do not connect in any substantive way.

Response: Thanks a lot for your kind comments.  The main work of this article is experimental study and numerical simulation study. The objects of numerical model research are divided into rescaled model and unscaled model. The research idea of this article is to design the storage tank model to carry out the shaking table test, then compare and analyze the test results of the seismic storage tank and the isolation storage tank, and study the effect of the isolation bearing. Then, the numerical model is used to simulate the results of the experimental model, and the validity and rationality of the finite element model are verified by comparing the experimental results and the finite element results. Finally, an actual LNG storage tank is taken as the research object to study the dynamic response pattern of the LNG storage tank after seismic isolation measures are adopted. The connection between Part I and Part II is threefold: (a) The main purpose of this study is to explore the seismic performance of large LNG storage tanks. To this reason, we carried out a shaking table test of a scaled model of a large LNG storage tank. Through the results of the shaking table test, it is verified whether the large-scale LNG storage tank has the seismic isolation effect after the seismic isolation measures are taken; (b) There is no way to do a shaking table test for a large LNG storage tank, but in practical engineering we need to obtain its dynamic response. Therefore, we can only use the scale method to conduct shake table tests on LNG storage tanks. For this reason, we can only verify that the numerical simulation method is correct through the results of the shaking table test, and then use the same numerical simulation method to conduct seismic time history analysis of large LNG storage tanks; (c) the validity and rationality of the numerical model are verified by the results of the shaking table test, so the numerical model of the unscaled storage tank can be established in the same way; On the whole, We believe that Part I and Part II are very closely related, and the research analysis of the first part provides a practical approach to the second part.

 

3. There is a lack of basic data on the MES analysis, e.g. what material model was adopted for the concrete, what for the seismic isolation elements? How was the subsoil modelled? What pile lengths were adopted for the analysis?

Response: Thank you for your suggestion. We are very sorry that we forgot some basic data in this article, we have added a description of the relevant basic data in the article.

The material model of the concrete used the bilinear kinematic hardening model. (lines 270-271)

 In the original manuscript, there is a paragraph dedicated to describing how spring elements (COMBIN14 and COMBIN40) can be used to model isolation bearings. (Lines 273-279 in the original manuscript) Maybe our description is not detailed so you didn't see this part of the description. We have re-described how the spring elements are used to model the isolation bearings. (lines 286-312)

In this paper, we did not consider the effect of soil mass on the storage tank, and regard the foundation of the storage tank as a rigid foundation. In some articles about pile-soil coupling interaction, such as “Experimental study of the effect of a flexible base on the seismic response of a liquid storage tank”, “Seismic resilience of extra-large LNG tank built on liquefiable soil deposit capturing soil-pile-structure interaction”, their research shows that the dynamic response of the storage tank will be reduced after considering the influence of soil, but the magnitude of the reduction is not very obvious.

Since the foundation of the storage tank is regarded as a rigid foundation in this paper, so the pile length calculated is from the ground to the bottom of the cap. In this paper, there are two types of pile lengths for unscaled storage tanks, the length of the outer pile foundation is 2m, and the length of the inner pile foundation is 2.3m. (lines 368-371)

 

4. There are no drawings showing the placement and numbering of the transducers. Without this, it is not possible to qualitatively assess and compare experimental and computational results.

Response: Thanks a lot for your kind comments. The placement and number of accelerometer sensors have been plotted in Figures 1(a) and (b), lines 143-147 are further descriptions of the arrangement  of accelerometer sensors.  

 

5. There is no definition of what is meant by " overturning bending moment".

Response: Thank you for your comments. We have added a description of "overturning bending moment" to the article. (lines 385-387)

 

All the modified texts were highlighted in the revised manuscript. The authors thank this reviewer again for the insightful and valuable comments, which enable us to greatly improve the quality of the manuscript.

 

Author Response File: Author Response.docx

Reviewer 2 Report

This paper examines the shaking table test and numerical simulation analysis of the LNG storage tank structure model. The seismic storage tank's acceleration response roughly increases linearly in the direction of height, and the seismic isolation bearing significantly affects the seismic isolation of the storage tank's acceleration. The outcomes of the numerical simulation demonstrate consistency between the numerical model's seismic responses and the shaking table test's spectral characteristic curves. In order to prevent damage to the auxiliary pipeline brought on by excessive displacement, it is also advised to concentrate on the storage tank's displacement. The paper is interesting and some specific comments on the paper are as follows:

 

 

1.       It is required to provide some details for calculating the equivalent stiffness of a single lead core rubber bearing.

2.       Section 3.3 must include a note on the convergence of the mesh size for the storage tank's finite element model. Details of the lead-rubber bearing finite element modelling must also be provided.

3.       In the caption of figure 8, seismic storage tank, should be LNG storage tank.

4.       The performance of the lead rubber bearings for the liquid storage tanks under long duration and near fault motions was studied in the papers, i.e., “Earthquake response of base-isolated liquid storage tanks for different isolator models”, Journal of Earthquake and Tsunami, 2014, 8(5), 1450013; and “Response of base-isolated liquid storage tanks to near-fault motions”, Structural Engineering and Mechanics, 2006, 23(6), 615–634. A discussion in this regard, taking into account the paper mentioned above and others, would be extremely beneficial to the researchers.

5.       The presentation of the paper needs to be further improved to the level of international journal standards.

Author Response

                         School of Civil Engineering, Chongqing University

 

Dear Editor,

 

Manuscript ID: applsci-1846107

 

Type of manuscript: Article

 

Title: Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model

 

Authors: Zengshun Chen ¹, Zhengang Xu ^{1, *}, Lingxiao Teng ², Jun Fu ^{1, 3}, Tao Xu ^{1, 4}, Zhihang Zhao ^{1, *}

 

Submitted to section: Civil Engineering, Seismic Performance of Concrete Structures: Theory, Modeling and Applications

 

Please find attached a revised version of our manuscript, 'Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model ', which we resubmit for the consideration of publication in Applied Sciences.

 

Thank you and the reviewer for the valuable comments, which enabled us to greatly improve the quality of our manuscript. According to the comments, we have made extensive modifications to the original manuscript. The modified texts were highlighted in the revised manuscript. Enclosed with this letter, in the following pages, are our point-by-point responses to each reviewer comment. We sincerely hope this manuscript will be finally accepted for publication.

 

Thank you for coordinating the review processes of this manuscript.

 

Yours truly,

 

Zhengang Xu

 

School of Civil Engineering,

Chongqing University

Shapingba District

Chongqing 400045, China

Tel.: +852 23588763,

Fax: +852 23581534.

E-mail: [email protected]

 

Point-to-point response: Reviewer 2

1. It is required to provide some details for calculating the equivalent stiffness of a single lead core rubber bearing.

Response: Thank you for your suggestion. The parameter of the equivalent stiffness of the lead-core rubber bearing are provided by the manufacturer of the isolation bearing, and we have not conducted experiments to test its equivalent stiffness.

 

2. Section 3.3 must include a note on the convergence of the mesh size for the storage tank's finite element model. Details of the lead-rubber bearing finite element modelling must also be provided.

Response: Thank you for your suggestion. Section 3.3 has added a description on the convergence of the mesh size for the storage tank's finite element models, which gives the detailed information about grid settings and mesh element selection. (lines 275-285).

In Section 3.3, there is a paragraph dedicated to describing the finite element modeling of lead-rubber bearings. Perhaps the description of this paragraph is not clear enough. Therefore, we re-describe how to use ansys software to simulate lead-rubber bearings. (lines 286-312)

 

3. In the caption of figure 8, seismic storage tank, should be LNG storage tank.

Response: Thank you for your comments. We have revised the title of Figure 8 according to your comments. (line 314 )

 

4. The performance of the lead rubber bearings for the liquid storage tanks under long duration and near fault motions was studied in the papers, i.e., “Earthquake response of base-isolated liquid storage tanks for different isolator models”, Journal of Earthquake and Tsunami, 2014, 8(5), 1450013; and “Response of base-isolated liquid storage tanks to near-fault motions”, Structural Engineering and Mechanics, 2006, 23(6), 615–634. A discussion in this regard, taking into account the paper mentioned above and others, would be extremely beneficial to the researchers.

Response: Thanks a lot for your kind comments. We have refined the literature review based on your suggestions. (lines 58-59 and lines 67-69)

 

5. The presentation of the paper needs to be further improved to the level of international journal standards.

Response: Thanks a lot for your kind comments. The authors have adjusted the content of the article to bring it up to the level of an international journal.

 

All the modified texts were highlighted in the revised manuscript. The authors thank this reviewer again for the insightful and valuable comments, which enable us to greatly improve the quality of the manuscript.

 

Author Response File: Author Response.docx

Reviewer 3 Report

The paper “Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model” reports an interesting work about the evaluation of the seismic behaviour of LNG storage tanks through the execution of laboratory tests and numerical analyses. The topic of the manuscript is current and not fully covered by existing literature. In general, the manuscript is well organized in its different sections and the results obtained from the shaking table tests and from the numerical analyses are clearly presented and discussed in the text. For these reasons it is opinion of this reviewer that the manuscript can be considered for the publication on Applied Sciences Journal after the following minor corrections/improvements:

      add the U.M. in Figures 1 and 11

-        in Table 2 change the “K” of “kN” in lowercase

-        Figure 16  make the legend of the results more readable

-        Section 5: in the conclusions better highlight the original aspects of the work

-        Add in the text the reference of the Equation 1

Author Response

                         School of Civil Engineering, Chongqing University

 

Dear Editor,

 

Manuscript ID: applsci-1846107

 

Type of manuscript: Article

 

Title: Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model

 

Authors: Zengshun Chen ¹, Zhengang Xu ^{1, *}, Lingxiao Teng ², Jun Fu ^{1, 3}, Tao Xu ^{1, 4}, Zhihang Zhao ^{1, *}

 

Submitted to section: Civil Engineering, Seismic Performance of Concrete Structures: Theory, Modeling and Applications

 

Please find attached a revised version of our manuscript, 'Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model ', which we resubmit for the consideration of publication in Applied Sciences.

 

Thank you and the reviewer for the valuable comments, which enabled us to greatly improve the quality of our manuscript. According to the comments, we have made extensive modifications to the original manuscript. The modified texts were highlighted in the revised manuscript. Enclosed with this letter, in the following pages, are our point-by-point responses to each reviewer comment. We sincerely hope this manuscript will be finally accepted for publication.

 

Thank you for coordinating the review processes of this manuscript.

 

Yours truly,

 

Zhengang Xu

 

School of Civil Engineering,

Chongqing University

Shapingba District

Chongqing 400045, China

Tel.: +852 23588763,

Fax: +852 23581534.

E-mail: [email protected]

 

Point-to-point response: Reviewer 3

1. add the U.M. in Figures 1 and 11.

Response: Thank you for your suggestion. We have added the U.M. in Figures 1 and 11. (lines 138 and 376)

 

2. in Table 2 change the “K” of “kN” in lowercase.

Response: Thank you for your suggestion.  We have changed "K" to "k" in Table 2. (lines 183-184)

 

3. Figure 16 make the legend of the results more readable.

Response: Thank you for your comments. We have made changes to Figure 16 so that the legend of the results are now more clearly readable. (line 424)

 

4. Section 5: in the conclusions better highlight the original aspects of the work.

Response: Thanks a lot for your kind comments. We have made changes to Section 5 in accordance with your comments. (lines 426-461)

 

5. Add in the text the reference of the Equation 1.

Response: Thanks a lot for your kind comments. We have added literature citations to Equation 1 in accordance with your comments. (line 173)

 

All the modified texts were highlighted in the revised manuscript. The authors thank this reviewer again for the insightful and valuable comments, which enable us to greatly improve the quality of the manuscript.

 

Author Response File: Author Response.docx

Reviewer 4 Report

As non-native English speaker, I would kindly suggest to make English native check before submitting papers. In the paper. Many unusual expressions were used in the article, for example: scholars, physical diagram etc. Therefore, it is necessary to improve English before publishing.

 

Some comments have been added to the pdf file.

 

Comments for author File: Comments.pdf

Author Response

                         School of Civil Engineering, Chongqing University

 

Dear Editor,

 

Manuscript ID: applsci-1846107

 

Type of manuscript: Article

 

Title: Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model

 

Authors: Zengshun Chen ¹, Zhengang Xu ^{1, *}, Lingxiao Teng ², Jun Fu ^{1, 3}, Tao Xu ^{1, 4}, Zhihang Zhao ^{1, *}

 

Submitted to section: Civil Engineering, Seismic Performance of Concrete Structures: Theory, Modeling and Applications

 

Please find attached a revised version of our manuscript, 'Experimental and Numerical Investigation for Seismic Performance of a Large−scale LNG Storage Tank Structure Model', which we resubmit for the consideration of publication in Applied Sciences.

 

Thank you and the reviewer for the valuable comments, which enabled us to greatly improve the quality of our manuscript. According to the comments, we have made extensive modifications to the original manuscript. The modified texts were highlighted in the revised manuscript. Enclosed with this letter, in the following pages, are our point-by-point responses to each reviewer comment. We sincerely hope this manuscript will be finally accepted for publication.

 

Thank you for coordinating the review processes of this manuscript.

 

Yours truly,

 

Zhengang Xu

 

School of Civil Engineering,

Chongqing University

Shapingba District

Chongqing 400045, China

Tel.: +852 23588763,

Fax: +852 23581534.

E-mail: [email protected]

 

Point-to-point response: Reviewer 4

1. How many piles? What kind of support is the connection between the piles and the tank structure?

Response: Thank you for your suggestion. There are 13 pile foundations in the model tank. For the seismic storage tank, the pile foundation and the bearing platform of the storage tank are directly connected. For the seismic storage tank, lead-core rubber bearings are arranged between the pile foundation and the bearing platform of the storage tank. We have added a description of this part to the article. (lines 134-138)

 

2. Add specification of accelerometers.

Response: Thank you for your comments. We have added the specifications of the accelerometer in accordance with your comments. (lines 153-156)

 

3. Why were the accelerograms of these earthquakes chosen?

Response: Thank you for your suggestion. In the article, we have added an explanation about the selection of seismic waves. (lines 160-166)

 

4. 'scaled' is better.

Response: Thank you for your comments. We have made changes based on your comments. (line 169)

 

5. As non-native English speaker, I would kindly suggest to make English native check before submitting papers. In the paper. Many unusual expressions were used in the article, for example: scholars, physical diagram etc. Therefore, it is necessary to improve English before publishing.

Response: Thank you for your comments. We have checked the article in native English based on your suggestion. (line 63, 64, 105, 107, 152, 157)

 

All the modified texts were highlighted in the revised manuscript. The authors thank this reviewer again for the insightful and valuable comments, which enable us to greatly improve the quality of the manuscript.

 

Author Response File: Author Response.docx