Study on Earthquake Failure Mechanism and Failure Mode of Cable-Stayed Pipeline Bridge Considering Fluid–Structure Coupling

Round 1

Reviewer 1 Report

Dear authors,

The paper has good potential and deals with a very interesting topic. In order to make the paper even better, I have some comments and suggestions.

In the analysis, you used 77,582 nodes and 14,414 units. Why did you choose that size of the elements? Did you use a different size of elements for comparison? How would the size of the elements affect the results of the analysis? Please explain this a little.

In Table 1, the modulus of elasticity is not well written. The number 105 is written instead of 10^5.

Picture 3 is of very poor quality. Each image needs to be enlarged. In addition, deformation values are barely visible.

In Table 3, the deformation parameter is incorrectly described in the third column. It is necessary to throw it out.

The same applies to Figure 4.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors,
thank you for your paper focused on pipeline bridge structures under earthquake loading. My comments are:
- line 45, there is written "Fluid-structure coupling (FSI)" - shouldn't it be the abbreviation FSC? What does "I" mean?
- line 47, there is given "Muller [3] - in References is "Mueller", not Muller, what is valid? One name needs to be corrected.
- if literature with more than two authors is cited, "et al." should also be mentioned, e.g. Fei et al. [7], not only Fei [7], correct throughout the document,
- line 80, there is given "Dos [12]", it is "Dos Santos et al. [12]", not only Dos,
- after formulas use "where" with no capital "W", the sentence continues,
- chapter 2.2, lines 233-234 - it is not entirely clear from the text whether it is a real bridge construction used somewhere in practice, or it is only a theoretically chosen bridge construction. Is it a real bridge?
- chapter 2.2 - some information is not clear from the text - where is the bridge deck supported? I assume that on the middle pylon (tower) - and then where? At the ends? Where is fixed support? It is not clear how the pipes on the bridge deck are stored - via bearings (cast iron) - are they all fixed (fixed to the bridge deck every 3.0m)? Or are they sliding? Sliding only in the longitudinal direction, or also in the transverse direction? It affects the stiffness and interaction with the supporting structure. What are the boundary conditions applied to pipes? Are there also supports at the end of the pipes in the longitudinal direction simulating the continuation of the pipes outside the bridge?
- line 243, tab. 1 - use "strand" or "cable" not "rope" (from wires is made strand, from strands is made cable),
- tab. 1, there is (kg/m3) - "3" is superscript (upper index),
- tab. 1, values of densities, there is "105" - "5" is superscript (upper index), otherwise the value has no meaning,
- line 263, there is mentioned code (GB/T50407-2017) - I recommend quoting the code also in References,
- tab. 3 - the name must be modified, the name cannot say that tab. 3 shows ..., I recommend changing the title to "Table 3. Preview of the maximum ...",
- chapter 3.1, it is stated here that the construction is actually not suitable for seismic stress, because the stresses are exceeded (lines 356-358), and what now? Was such a construction deliberately chosen? A real construction could not fail.
- lines 434-439 - the condition that the structure must meet the deformation of 1/100 and exceeding it does not mean a failure of the structure, it means a violation of the serviceability limit state (SLS), not the ultimate limit state (ULS). The violation will occur if the ULS is over-wound - resistance, e.g. bending moment, or shear forces, etc. Failure of the structure can occur by exceeding the voltages mentioned in chapter 3.1.2 - the occurrence of plasticization, the resistance must be verified.
- tab. 5 and text under tab. 5 (lines 479-480) - values of the displacements of the supports are from 0.134m to 0.325m - are these not very large values? Do steel bearings allow such large displacements to be transferred? Does this mean that the bearings between the bridge deck and the pipes are sliding - how are the pipes relieved at the ends? How is it agreed that the pipes continue beyond the bridge? Can such shifts occur at all if the pipes are fixed behind the bridge?
- English needs to be corrected.

Best regards.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The article

Study on earthquake failure mechanism and failure mode of cable-stayed pipeline bridge considering fluid-structure coupling,

By Xiyu Zhu and Guangyuan Weng,

investigates the failure mode of a cable-stayed pipeline bridge when subjected to earthquake actions with a magnitude M=9. The study focuses on the structural system of an oil and gas cable-stayed pipeline bridge as the research object. To accomplish this, the authors establish a full-scale finite element calculation model of the oil and gas cable-stayed pipeline bridge using ANSYS Workbench finite element software, based on the stress and structural characteristics of the oil and gas pipeline.

The paper is well written and the results are almost always explained in detail, with overall good and fundamental considerations.

Nevertheless, before full acceptance can be granted, the following points need to be assessed by the Authors.

 

MAJOR (conceptual) REMARKS

1.      The Authors specifically used the commercial software ANSYS Workbench for their investigations. Is there any specific reason for this choice?

2.      The main limitation of this work is, arguably, that only one seismic wave has been used for the numerical simulations (the El Centro Seismic Wave).

3.       The authors also take into consideration the influence of the medium inside the oil and gas pipeline, leading them to create a fluid-structure coupling effect finite element model. This model is used to analyze the deformation, stress, strain, and other responses of the oil and gas pipeline under the seismic waves' action from different directions. However, from Equations 1 to 5, it is not clear how much of the theoretical background is actually a novelty introduced by the Authors and how much, instead, is retrieved from the already-existing scientific and technical literature.

4.       The results of the calculations indicate that the overall damage to the pipeline is relatively consistent, with the maximum deformation, stress, and strain concentrated at the inlet and outlet ends and side spans of the pipeline. Arguably, this is quite well expected, thus, it does not seem to introduce any particular novelty.

5.      The FEM is supposedly nonlinear, however, judging from Figure 8, it seems almost as linear, with the response almost scaling up linearly for an increasing input amplitude.

6.      The Authors did provide a quite comprehensive state-of-the-art review for what concerns Fluid-structure coupling (FSI) but the part related to failure and damage in steel pipelines is instead a bit limited. Some recent studies, such as https://doi.org/10.3390/app11135773, should be included.

MINOR (editorial) REMARKS

1.      The font size of the equations seems to be larger than for the rest of the text. Please uniform.

2.      Table 1, second-to-last column: is it a typo? i.e. 2.06x10^5 instead of 2.06x105

3.      Table 3, third column: are four (or even five) decimal digits necessary? The same remark applies to Table 4, second-to-last column, Table 5, second column, and Table 6 (both the second and the last columns).

 

4.      All subplots in Figure 4 seem to have been ‘squeezed’ inside the page width.

The English is overall good.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors acted according to the remarks of the reviewer. The paper can be published.

Author Response

Thank you for your decision and constructive comments on my manuscript.

Reviewer 2 Report

Dear Authors,
thank you for incorporating the reviewers' comments and improving the paper. I have no further comments
Best regards.

Author Response

Thank you for your decision and constructive comments on my manuscript.

Reviewer 3 Report

This Reviewer is overall satisfied with the reply to the major remarks. Regarding the minor (editorial) remarks, for what concerns the previous point 7: in some in-line equations and mathematical notations (e.g. lines 199 and 238-239) the font is yet dissimilar from the rest of the text (seems slightly larger)

Furthermore, in Table 4, second column, since the measurement unit ([s]) is already declared in the top line, it is not necessary to recall it for all entries in the lines below.

 

Apart from these minor details, this Reviewer is satisfied with the current content of the paper.

The English is overall good.

Author Response

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Author Response File: Author Response.pdf