Earthquake Damage Index and Fragility Analysis of Steel Damper for Seismic Isolation Bridge

Round 1

Reviewer 1 Report

The manuscript provides experimental and fragility analysis results related to bridge damping devices that can enrich the literature. The following comments are provided to improve this manuscript:

1- The last section in the introduction should highlight the study objectives rather than discuss the manuscript's contents.

2- More details should be added to Figure 1 to help the reader comprehend the different dampers and specimens considered in this study (i.e., Cylindrical and E-shaped dampers). Also, confirm that the dimensions of Cylindrical Specimens #1 & #2 and E-shaped specimens #1 & #2 are identical.

3- Provide more discussion related to Table 1 for different specimens tested in this study.

4- Please confirm the longitudinal and transverse directions of the bride model in Figure 9.

5- Elaborate on the natural seismic and artificial ‘waves’ used in this study and the database used for selecting the natural earthquake records.   

6- Elaborate on the following for clarification: ‘seismic intensity of 7 degrees (PGA=0.15 g)’ & ‘seismic intensity of 9 degrees (PGA=0.4 g)’; Why PGA of 0.4 g corresponds to intensity 9?

7- Provide more discussion in Figures 11 and 12 related to other performance limit states, such as D1, highlighting that slight damage is expected at a low PGA level (i.e., 0.15 g).

Text can be improved; please conduct a thorough review to shorten long sentences and correct grammatical mistakes.

Author Response

Dear Reviewer:

Thank you for your comments concerning our manuscript entitled “Earthquake Damage Index and Fragility Analysis of Steel Damper for Seismic Isolation Bridge.” Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research. We have studied the comments carefully and have made corrections which we hope meet with approval. For revisions to this paper and replies to review comments, please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

This study conducted loading tests on two types of steel dampers to evaluate the fatigue damage of those dampers under earthquakes. The damage index combined the effect of cumulative energy dissipation and maximum deformation. Fragility analysis of the steel dampers adopted in a seismically isolated bridge was carried out by incremental dynamic analysis. The paper is well written in general. Below are several comments:

 (1)   The reason for choosing the cylindrical and E-type steel dampers should be strengthened.

(2)   The working mechanism, including the connection methods of the E-type steel damper should be explained in detail.

(3)   The design of the loading scheme should be explained with references. For instance, why the design displacement was 300? How were the average velocities and number of cycles chosen? What are the relationships between the loading scheme and the requirement in relevant design standards?

(4)   The cylindrical dampers fractured at the middle portion but not at the end. Is this the desired fracture form? Is there any design requirement on the fracture form to improve the fatigue performance of this type of damper?

(5)    The reason for taking beta as 2 in Equation (7) should be explained in detail because it is an essential variable for this study. Although the reference [9] is referred to, but it is written in Chinese.

(6)   Units should be added in Table 1.

(7)   Figure 4 (d) should be E-shape #2.

(8)   The exponent part in Equation (1) is difficult to recognize.

Some Chinese characteristics remain, such as Equations (3) and (5). Please change them to English.

Author Response

Dear Reviewer:

Thank you for your comments concerning our manuscript entitled “Earthquake Damage Index and Fragility Analysis of Steel Damper for Seismic Isolation Bridge.” Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research. We have studied the comments carefully and have made corrections which we hope meet with approval. For revisions to this paper and replies to review comments, please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The Authors have addressed all Reviewer’s comments and, in my opinion, the manuscript is worth publishing now

Reviewer 2 Report

The reviewer's comments have been well addressed in the revised manuscript.