A Study on the Direct Application of the Gaussian Kernel Smoothing Filter for Bridge Health Monitoring

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1         This paper primarily addresses the localization and quantification of bridge damage in noisy environmental conditions. However, the introduction lacks a comprehensive review of the current state of research on damage localization and quantification. Therefore, a more focused literature review is recommended.

 

2         What is the fundamental principle behind noise reduction using GKSF? You should provide additional explanation.

3         What do the 'Dynamic modal parameters' mentioned in line 201 specifically refer to?

4         The quantification of damage is dependent on the slope of the intersection points of the DI-spline curve. However, the article fails to clearly define the theoretical relationship between this slope and the extent of damage, such as crack length. Has a physical model been established to correlate the extent of damage with the slope, potentially through a linear or nonlinear mapping?

5         The computation of the normalized energy damage index is based on the smoothed signal of the acceleration response. However, this energy index may demonstrate inadequate sensitivity to localized damage and is vulnerable to interference from global stiffness variations, such as those caused by settlement. Have any comparative experiments been carried out to assess the performance differences between this index and other damage indicators?

6         What is the underlying mechanism that leads to the double peak observed in the case of N6 in Figure 7c?

7         In the paper, the span of the GKSF is defined as the inverse of the bridge's first natural period. However, actual bridges may encounter multi-modal coupling or frequency shifts resulting from environmental factors, such as variations in temperature and load. If the first natural frequency experiences minor changes due to these environmental influences, should the span of the GKSF be adjusted dynamically? Furthermore, how can we ensure the robustness of the span selection?

8         What is the significance of the normalization factor within the overall methodology? In line 279 of the paper, it is mentioned that the normalization factor remains constant across all velocities. Does this suggest that it is not a critical parameter?

 

Author Response

The response file for the esteemed reviewer is attached

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study presentes a Gaussian Kernel Smoothing Filter based approach to implement structural health monitoring for bridge systems. The methodology is validated through a numerical model of simply supported bridge under a moving sprung mass. Although the manuscript lays a solid foundation, it beckons for a more in-depth exploration of specific aspects, meticulous adjustments to content, and a thorough revision to address identified issues.

1.   This study lacks novelty as it relies solely on existing methods. The authors will have to clarify what are the new elements of the work compared to existing literature.

2.     Please summarize the contributions of this study and add them to the introduction section.

3.    Regarding the damage quantification index in Section 4.5, this study simulates the damage locations at Nodes 3 and 6, thereby obtaining a intersection point and quantifying the damage by calculating the relative slope. However, the applicability of the index needs to be evaluated if the damage node is changed to any two nodes. Please add some explanations or validations related to the universality of the quantification index.

4.   In conclusion section, please provide a description of the limitations of the proposed method. And please also add a discussion to the application of real bridge structural health monitoring using the proposed method.

 Minor comments:

1.       Improve the language for conciseness and brevity across the manuscript.

2.       In Table 3, the “crack depth to beam height ratio” in Scenario-6 should be 20%.

3.       Lines 290 and 292, the numbers of Figures 6a, 6b and 6c, 6d are mistaken.

4.       Lines 341-345, this paragraph is a bit redundant and there is no logical connection with the previous text.

Comments on the Quality of English Language

Please improve the language for conciseness and brevity across the manuscript.

Author Response

The response file for the esteemed reviewer is attached

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The article is devoted to the actual problem of damage detection in bridge structures based on measurement data. Vibration responses (obtained numerically) are smoothed using the proposed Gaussian Kernel Smoothing Filter, then energy parameters are calculated for each point with a placed sensors. Comparing these parameters for the damaged and undamaged structure allows to localize the location of the damage. The article is of interest in the field of Structural Health Monitoring for readers of the journal. However, there are several important questions:

1. The research carried out is theoretical without experiment. Is it possible to detect damage from experimental data using this method?

2. The calculation of responses (vibrations) using the numerical model is not sufficiently described. what software was used.

3. application of spline intrapolation was performed on the basis of data in 7 Nodes? Is this number of points sufficient for a spline?  If we take 2 times more Nodes (e.g. 15), will spline7 be significantly different from spline15?  Why are zero values taken for L= 0 and L=25 ?

4. In Fig. 1, the axes are not labeled. Perhaps we should label them according to formula (1)?

5. The first natural frequency of simply supported beam is pi/2 * sqrt ((EI) / (µ*L^4)).  (or online - https://calcdevice.com/frequency-of-simply-supported-beam-id192.html). According to the data from the article the frequency should be about 4 Hz (adding car mass equal to 1/30 of the beam mass will not change this estimate much), in the article the natural frequency is 2.933 Hz. How can this difference be explained?

Also, there is typo in the article, e.g.:

- Table 1 shows the first natural period, but should be frequency, similar error on page 6 line 186.

 

In my opinion, the paper needs to be improved. The article can be published after major revision

 

Author Response

The response file for the esteemed reviewer is attached

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

• In the introduction, the author has included a paragraph that mentions the first author's name, which is unrelated to the research presented in this paper. Please remove this section.

Author Response

Thanks to the esteemed reviewer for re-considering our manuscript and provide us minor comment. We removed the mentioned paragraph in the revised version

 

Regards

Authors

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors, after the revision the article is much improved and in my opinion it can be published in its current form.

Author Response

We are happy that the esteemed reviewer accepted our manuscript. Thank you

 

Regards

Authors

Reviewer 3 Report

Comments and Suggestions for Authors

After revision, the article has been improved and can be published.

In Table 1 there is a typo in the column unit of first natural frequency  (should be Hz)

Author Response

Thanks the esteemed reviewer for accepting this manuscript. The mentioned typo was corrected in the revised manuscript

 

Regards

Authors