Durability Assessment Method of Hollow Thin-Walled Bridge Piers under Rockfall Impact Based on Damage Response Surface

Round 1

Reviewer 1 Report

The manuscript entitled "Durability assessment method of hollow thin-walled bridge piers under rockfall impact based on damage response surface" presents an interesting simulation study regarding the impact of rocks on bridges' durability. However, the rationale for choosing the parameters of the model designed by the authors wasn’t presented, and other issues must be addressed. The paper needs minor revisions before it is processed further, some comments follow:

Rockfall-HTWBP impact model Section

“A 72+120+120+72 m continuous rigid frame bridge on the highway from Longshan” What was the rationale for choosing this bridge? Why is it relevant for the readers/researchers?

“As reported by previous studies, the diameter of rockfalls is normally 1.5 m to 2.5 m” – please provide corresponding citations.

„, 1.5 m, 2.0 m and 2.5 m are established in this research” the dimensions range of the rocks is very important for both the model and a real situation. Why only these three dimensions were considered? To make this study relevant to the literature the rock size distribution should be conducted and much more models should be introduced.

Moreover, the model considers the effect of the impact of one spherical rock on the beam's integrity. However, what about multiple rocks that hit at the same time?

Discussion section. The discussion section is missing. In the discussions section, clear correspondence and comparison between the results of this study and those from the literature should be provided. Please improve, compare the obtained results with those from the literature and make qualitative and quantitative appreciations.

Limitation: The study is based on very few parameters. A much more relevant model could be obtained by increasing the number of spheres that hit at the same time and the range of the size of the rock.

The whole work is based on a very limited model. Please provide a separate section with future directions and limitations of the study. 

English grammar suggestions:

increase increasingly – please replace with suitable terms.

Author Response

Dear reviewer 1#, please see the attachment "response to reviewer 1#".

Author Response File: Author Response.pdf

Reviewer 2 Report

This article investigated the durability assessment method of hollow thin-walled bridge piers under rockfall impact based on damage response surface. The article needs some major revisions before it can be accepted for publication.

1. Abstract: the description of the current investigation is very shallow. It should be explained in detail.

2. The sentence can be revised “ China is a mountainous country. With the continuous improvement of the construction of transportation infrastructure, the number of large-span bridges across valleys also increase increasingly.” With the continuous improvement of transportation infrastructure construction, the number of large-span bridges across valleys increased.

3. The literature section is sufficiently written and the novelty of the work is also discussed enough.

4. The actual picture of a continuous rigid frame bridge on the highway from Longshan to Yongshun in Hunan Province can be included.

5. Section 2.1: I suggest adding the citation for this sentence, “As reported by previous studies.”

6. Why are the three rockfall models with different diameters, i.e., 1.5 m, 2.0 m and 2.5 m, established in this research? Explain the scientific reason in section 2.1.

7. What is the reason for verifying the drop weight test of reinforced concrete beam?. The research objective is the durability assessment method of hollow thin-walled bridge piers under rockfall impact based on damage response surface. It is not an appropriate comparison of the behavior of the drop weight test of a reinforced concrete beam with hollow thin-walled bridge piers. Since the end condition for the beams and the hollow thin-walled bridge piers are different, falling mass impacts, the verticle and lateral direction doesn't exhibit the same behavior since end conditions are different. Hence section 2.3 is inappropriate for the current objective.

8. Figure 14. Since the hollow thin-walled bridge piers with deck slab are the cantilever action. Figure 14; why is the displacement maximum at 40 m height? Please justify this.

9. Is the effect of the deck slab considered in this study?

10. More key findings can be included in the conclusion section.

11. The English language should be checked throughout the manuscript.

Author Response

Dear reviewer 2#, please see the attachment "response to reviewer 2#".

Author Response File: Author Response.pdf

Reviewer 3 Report

The author established a damage assessment method of damage zoning map based on response surface method. The following comments are given to the authors for the revision.

1.      How are the material parameters of rockfall determined according to the previous studies?

2.      How is the contact algorithm implemented?

3.      In Figure 9, the peak data should be marked in the figure to show the difference between two peaks.

4.      Section 2.3.2. The grids shown in Figure 10 are 25 mm, 50 mm, and 75 mm, respectively, while a description of 20 mm appears in the body. Why?

5.      Chapters 3.1 and 3.2 should be revised.

6.      In Figure 15 (d), it should provide more sufficient discussion on the conclusion.

7.      Table 10 is missing in the manuscript.

Author Response

Dear reviewer 3#, please see the attachment "response to reviewer 3#".

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear authors,

We have done an excellent job in improving your manuscript. I have only one more suggestion. Please separate the opportunities and limitations from the conclusion section, i.e. provide the limitations in a separate section.

Best regards,

Author Response

Dear reviewer, thank you for your kind reminder, we have provided the limitations in a separate section. Please refer to Section 7 of the revised manuscript. The modifications in the revised manuscript are highlighted in yellow. 

Reviewer 2 Report

Authors have addressed all the comments with proper explaination.

Author Response

Dear reviewer, thank you for your kind help in improving our manuscript.  A spell check has been conducted on the whole manuscript. The modifications in the revised manuscript are highlighted in yellow. Please refer to the revised manuscript.

Reviewer 3 Report

All the comments have been addressed.

Author Response

Dear reviewer, thank you for your kind help in improving our manuscript.