Lateral Buckling of Pipe-in-Pipe Systems under Sleeper-Distributed Buoyancy—A Numerical Investigation

Round 1

Reviewer 1 Report

The manuscript presents a numerical and analytical study on the lateral buckling of pipe-in-pipe systems under sleeper-distributed buoyancy method. Firstly, a finite element model is setup to study the effect of different parameters on the critical buckling load. The results are presented and discussed. Then, based on the obtained numerical results, an analytical method is presented to predict the critical buckling load. The derived formula is checked against the numerical results, where good agreement is observed.

The topic that is developed in the article is interesting. The authors have produced a good research, which can constitutes a guide for future researches and also for steel pipeline systems design.

I made some comments in order to improve the manuscript. The authors should take the comments into account and revise their manuscript.

 

 

Specific Comment 1

The reading of the manuscript needs to be improved. Some sentences are confusing and must be rewritten.

 

Specific Comment 2

Please revise the article to correct typos. Just one example: at line 48, delete “2. Materials and Methods”.

 

Specific Comment 3

The title should be modified to “Numerical and Analytical Study on …”

 

Specific Comment 4

Some formatting issues must be corrected:

- All tables and figures must be referred in the text before they appear;

- Many references are incomplete and do not follow the rules of the journal. Please refer to the instructions for authors.

 

Specific Comment 5

Section 1

In the introduction section, the literature review must be improved and the references updated with more studies related with the specific topic of the manuscript. The findings from these studies should be summarized and discussed. Also, please clarify in the end of this section what is the novelty of your study when compared with previous ones from the literature review.

 

Specific Comment 6

Sections 2.1 +  2.2

The description of the FE model is somewhat poor and should be complemented with more details (mesh density; how the seabed was modeled?; what are the materials properties?; more figures with details of the FE model; …)

 

Specific Comment 7

Section 3

The tile of the section should be “Parametric analysis”

 

Specific Comment 8

Line 155

Please define what “stress reprogram” is.

 

Specific Comment 9

Section 3

In addition to Figures 3 to 9, a table should be also included with the numerical values of parameters of interest (critical buckling load and analyzed parameters) for better comparison with the figures. Also, the captions of the referred figures should be rewritten. For instance, for Figure 4, it should be “Influence of the buoyancy density in the axial force – lateral displacement graph”.

 

Specific Comment 10

Please correct “Data Availability Statement” and “Conflicts of Interests” paragraphs.

Author Response

Some formatting issues must be corrected:

- All tables and figures must be referred in the text before they appear;

Thank you. We have corrected this.

- Many references are incomplete and do not follow the rules of the journal. Please refer to the instructions for authors.

We have modified the references.

 

Specific Comment 5

Section 1

In the introduction section, the literature review must be improved and the references updated with more studies related with the specific topic of the manuscript. The findings from these studies should be summarized and discussed. Also, please clarify in the end of this section what is the novelty of your study when compared with previous ones from the literature review.

The literature review is improved and added references related to the buoyancy method. The last paragraph of this section has been rewritten

 

Specific Comment 6

Sections 2.1 +  2.2

The description of the FE model is somewhat poor and should be complemented with more details (mesh density; how the seabed was modeled?; what are the materials properties?; more figures with details of the FE model; …)

We have added the detail of the FE model in the section 2.2.

 

Specific Comment 7

Section 3

The tile of the section should be “Parametric analysis”

Thanks，we have modified this.

 

Specific Comment 8

Line 155

Please define what “stress reprogram” is.

We have modified it as “Mises stress”

 

Specific Comment 9

Section 3

In addition to Figures 3 to 9, a table should be also included with the numerical values of parameters of interest (critical buckling load and analyzed parameters) for better comparison with the figures. Also, the captions of the referred figures should be rewritten. For instance, for Figure 4, it should be “Influence of the buoyancy density in the axial force – lateral displacement graph”.

We have modified the captions form and added the tables from Table 3 to Table 8.

 

Specific Comment 10

Please correct “Data Availability Statement” and “Conflicts of Interests” paragraphs.

Than you, we have corrected this.

Reviewer 2 Report

The manuscript has the following title : "Numerical study on the lateral buckling of pipe-in-pipe systems under sleeper-distributed buoyancy method". 

The title is too long. It should be shortened to something like: "Lateral buckling of pipe-in-pipe systems under sleeper-distributed buoyancy - a numerical investigation". 

Some basic issues should be defined.

1. Define global buckling of the pipe .

2. Define local buckling of the pipe.

3. How are the buoyancy forces applied on the pipe ? Add an adequate FE drawing showing the model, the boundary condition and the applied forces.

4. Ch. 2.3 Model validation shows only the parameters in the literature. What are the parameters in [21] ? A proper table should be added comparing the present results to the results from [21].

Author Response

Dear reviewer， Thank you for your review and give us very valuable advice.

1. Define global buckling of the pipe .

Under the action of high temperature and high pressure, due to the thermal expansion and Poisson effect of pipeline materials, the pipeline inevitably has an elongation trend. However, the pipeline cannot expand freely due to the restriction of surrounding soil and rockfill. With the continuous increase of temperature and pressure, the pressure in the pipe gradually increases until a certain critical pressure, and the global buckling will happen

2. Define local buckling of the pipe.

If the global buckling is not controlled, it is likely to cause excessive bending deformation and damage of the pipeline or induce local buckling propagation.

3. How are the buoyancy forces applied on the pipe ? Add an adequate FE drawing showing the model, the boundary condition and the applied forces.

We have added the detail of FE model in the Fig.3.

4. Ch. 2.3 Model validation shows only the parameters in the literature. What are the parameters in [21] ? A proper table should be added comparing the present results to the results from [21].

We have added the parameters in [21] in Table 1.

Round 2

Reviewer 1 Report

I received and read the revised version of the article “Lateral Buckling of Pipe-In-Pipe Systems Under Sleeper-Distributed Buoyancy - a Numerical Investigation”. I´m generally satisfied with the authors’ replies to my comments and I also consider that most of my suggestions and concerns have been properly considered by the authors to improve the article. I consider that the revised article submitted by the authors can be accepted to be published after a final review to improve the reading.

Reviewer 2 Report

The authors improved their manuscript by correctly answering the issues raised by the reviewers. The present form of the paper is suitable for publication.