Dynamic Simulation and Seismic Analysis of Hillside RC Buildings Isolated by High-Damping Rubber Bearings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

Dynamic simulation and seismic analysis of hillside RC buildings isolated by high-damping rubber bearings

In the introduction section some works can be more criticized not just mentioning what is done in their paper, so, What is that the paper did not tackle, how beneficial is that work wrt your research about simulation and analysis of seismic effect e.g. Halkude et al. [6] employed response 55 spectrum analysis to compare the seismic performance of step-back and step-back-setback 56 frames on sloping ground, determining that the latter exhibited superior performance.

In the section of numerical modelling, you stated “The study includes three structural configurations: a flat isolated structure (FIS),” why specifically 3 structural configurations are included.

Add a source of these data, Table 2. Cross-sectional details of numerical models also for table 3.

Introduction

The introduction provides a comprehensive background on the seismic vulnerability of hillside buildings and the need for seismic isolation.

It includes relevant references to past earthquakes (e.g., 1994 Northridge, 2008 Wenchuan) and studies on structural irregularities.

The novelty of the study (focus on HDRBs for hillside buildings) could be highlighted earlier to better frame the research gap.

Some references (e.g., [6]–[13]) are grouped densely; expanding on key studies would improve clarity.

Research Design

     The study compares five numerical models (flat/hillside, isolated/non-isolated), which is rigorous.

Nonlinear time history (NTH) analysis and DHI modeling are well-justified for capturing HDRB behavior.

Clarify why only six earthquake records were selected and how they represent typical seismic hazards.

Justify the choice of PGA scaling range (0.2 g to 0.8 g) with respect to regional seismic codes.

Methods

The DHI model and HDRB design process are described in detail, including equations and parameters (Table 1).

ETABS modeling and FNA method are appropriately selected.

Provide more details on the validation of the DHI model (e.g., comparison with experimental data).

Explain the rationale behind the 20-mode Ritz vector analysis (why 85% mass participation was chosen).

Results

Results are extensive, covering hysteresis behavior, energy dissipation, accelerations, drifts, and forces (Figures 6–21).

Key findings (e.g., 90% reduction in roof acceleration) are clearly stated.

Include error bars or confidence intervals for repeated simulations (if applicable).

Discuss limitations (e.g., assumptions in material behavior or soil-structure interaction).

Conclusions

Conclusions align with results, emphasizing HDRB effectiveness (e.g., 80% drift reduction).

Practical implications for hillside building design are noted.

Add a brief paragraph on future work (e.g., experimental validation or cost-benefit analysis).

Figures and Tables

Figures (e.g., hysteresis curves, displacement spectra) are clear and support the text.

Tables (e.g., DHI parameters, HDRB properties) are well-organized.

Label subfigures (e.g., Figure 7a, 7b) directly in captions for easier reference.

Use consistent units (e.g., kN vs. kN/m) in Table 3.

English Language

Generally well-written but minor improvements needed:

        Fix typos (e.g., "need to be conducted" → "needs to be conducted").

       Avoid passive voice where possible (e.g., "It was observed that" → "We observed").

Originality/Novelty

High novelty: Focus on HDRBs for hillside buildings is underexplored.

DHI modeling adds methodological innovation.

Significance of Content

Highly relevant for seismic-prone regions with hillside construction.

Scientific Soundness

Robust methodology but could address limitations (e.g., model assumptions).

Interest to Readers

Appeals to engineers, seismologists, and policymakers.

Overall Merit

Good paper with minor revisions needed.

Ethical Checks

Plagiarism: None detected.

Self-citations: Appropriate; no excessive self-promotion.

Conflicts of Interest: Authors declare none.

Recommendation

Accept with Minor Revisions (address clarity, methodological details, and language edits).

Comments on the Quality of English Language

English Language

Generally well-written but minor improvements needed:

        Fix typos (e.g., "need to be conducted" → "needs to be conducted").

       Avoid passive voice where possible (e.g., "It was observed that" → "We observed").

Originality/Novelty

Author Response

Thank you for taking the time to review our manuscript. I’ve carefully considered your feedback and have prepared a detailed response to address your comments. You’ll find my comprehensive reply in the attached file. I appreciate your insights and hope this response fully clarifies the points raised.

Thank you again for your valuable input!

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1- While the manuscript addresses an important topic, it would further strengthen the paper to clearly articulate the specific novelty and added value of this research. In particular, it would be helpful to highlight what is new or unique in your study regarding the implementation of HDRBs on hillside RC structures with dropped layers, and how these findings can benefit both academic researchers and construction industry.

2- It could briefly mention the limitations of the study (e.g., modeling assumptions, lack of experimental validation, fixed soil conditions) to provide a balanced overview.

3- References [15–28] are listed, but it is not clear how each specifically relates to your study. I recommend briefly explaining the relevance of these references in the introduction to establish clear context or consider removing some that are not directly connected to your research focus.

4- The assumed effective period of 2.75 s and damping of 20% should be justified with reference to typical ranges for HDRB systems under comparable configurations in the literature to support your design choices.

5- You may consider adding a brief explanation of why the specific HDRB types (HH060X6R, HH065X6R, HH070X6R) were chosen and what design needs or constraints guided this selection, to help readers better understand your design choices.

6- Consider comparing the 0.28 m HDRB design displacement with the actual displacements recorded under high PGA to confirm it stays within safe limits.

7- Adding 1–2 lines on future research directions (e.g., experimental validation, inclusion of soil-structure interaction, cost-benefit analysis) would enhance the conclusion and demonstrate continuity of this research topic.

8-  Figure 3 appears to be repeated twice, resulting in the shifting of all subsequent figure numbers. This has caused a mismatch between figure numbers and their in-text references and needs correction for clarity.

9- In Figure 6, for PGA = 0.2g, the legend in the second row incorrectly lists "DIS"; it should be "DIIS." Please correct the figure.

10- You may consider briefly explaining why RSN1100 showed different energy dissipation results compared to the other records, as this would help readers better understand the findings.

11- In line 448, “Figure. 16 (a,b)” is referenced, but the figure does not display “a” and “b” labels. Please add these to the figure for consistency.

12- In Figure 14, the DIS data is not shown or may be overlapping with another line. This should be addressed to ensure all data are clearly shown.

13- In lines 484–485, it is stated that “the shear force is lowest at the base,” but to me, this is not clear from the figure. You may consider clarifying this point or adjusting the figure and text for consistency.

14- The conclusion currently reiterates known findings about the effectiveness of base isolation. To increase the impact of your manuscript, please clarify what specific findings of this study are novel and how they advance the understanding of HDRBs in hillside RC structures

Author Response

Thank you for taking the time to review our manuscript. I’ve carefully considered your feedback and have prepared a detailed response to address your comments. You’ll find my comprehensive reply in the attached file. I appreciate your insights and hope this response fully clarifies the points raised.

Thank you again for your valuable input!

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dynamic simulation and seismic analysis of hillside base-isolated RC buildings are the topic of the paper, considering high-damping rubber bearings (HDRBs). The authors provide five structural models analysed using nonlinear time history analysis (NLTH). The topic is of great interest to the scientific community, and the paper is suitable for publication in this journal after the revisions listed below.

- In the Introduction, the part ranging from rows 88 and 90 should be enlarged to discuss briefly the cited references; it would be preferable to add other references on the various types of isolation bearings, also for hospital buildings. To this end, some suggestions are reported below, reminding that the authors are free to use them and/or add other relevant ones:
[1] Mazza F. and Labernarda R. Concave Surface Base-Isolation System Against Seismic Pounding of Irregular Adjacent Buildings. WCCM-ECCOMAS2020. https://www.scipedia.com/public/Mazza_Labernarda_2021a 
[2] Ishii, K., M. Kikuchi, T. Nishimura, and C. J. Black. 2017. Coupling behavior of shear deformation and end rotation of
elastomeric seismic isolation bearings. Earthquake Engineering & Structural Dynamics 46 (4): 677–94.
[3] Gesualdi, G., D. Cardone, and G. Rosa. 2018. Finite element model updating of base-isolated buildings using experimental results of in-situ tests. Soil Dynamics and Earthquake Engineering. doi: 10.1016/j.soildyn.2018.02.003.
[4] Mazza F., Donnici A. and Labernarda R. Seismic Vulnerability of Fixed-Base and Base-Isolated Hospitals: Blind Comparison between Shaking Table and Numerical Tests. Procedia Structural Integrity. (2023); 44:147-154. doi: 10.1016/j.prostr.2023.01.020

- In section 2, in rows 119 to 121, the authors could describe other mechanical models for the nonlinear behaviour of HDRBs, accounting for the nonlinearity of vertical and horizontal stiffnesses and damping, as reported in [5] Mazza F. and Labernarda R. Internal pounding between structural parts of seismically isolated buildings. Journal of Earthquake Engineering (2021); doi: 10.1080/13632469.2020.1866122.
As before, the authors are free to use this suggestion and/or cite different references, with the aim of discussing other kinds of mechanical models for HDRBs. They should also discuss why the vertical axial load acting on the bearings has not been taken into account on the mechanical behaviour, considering that it represents a notably important factor affecting the mechanical response of the bearing, both in the horizontal and in the vertical directions (as in [6] Mazza F., Braile A. and Labernarda R*. Wavelet analysis for the vertical isolation ratio of RC hospital structures subjected to near-fault earthquakes. In: ECCOMAS 2024. doi: 10.23967/eccomas.2024.132).

- In section 2, the time step (t+1) is present in equations (6), (7), and (8); please check it since this time step is unknown during the analysis.

- Figure 2 should be provided in a better quality to make it more readable.

- Table 1 should be discussed, explaining how all the parameters are obtained.

- In section 3, Figure 4 is not correctly cited in the text. Please check.

- In section 3.2, the authors should explain why an effective period ranging from 2.5 to 3.5 s has been chosen.

- In section 3.2, in row 222, the percentage symbol should be deleted from "0.20% equivalent damping".

- In section 3.2, in the last sentence of page 7, the authors assume the superstructure as an elastic element;  this assumption should be justified properly, since nonlinear behaviour of the superstructure have been demostrated by many authors (as in [7] Mazza F. and Labernarda R. Internal pounding between structural parts of seismically isolated buildings. Journal of Earthquake Engineering (2021); doi: 10.1080/13632469.2020.1866122), habing a detrimental influence on the overall building behaviour.

- Figure 4 should be recalled in the text, since it seems not to be cited in the text.

- In section 3.3, Table 4 should also contain the excited masses (in percentage of the overall one) for each vibrational mode.

- In section 3.4, on page 10, Figure 5 should be recalled in the text instead of Figure 6 (row 308).
In this section, the authors should clarify why 6 natural ground motions are selected for obtaining the mean spectrum. Additionally, they should explain what kind of spectral compatibility criterion has been assumed in this paper.

- On page 10, in row 332, Figure 6 should be recalled instead of Figure 5.

- From page 11 to the end of the manuscript, the number of figures cited in the text should be reduced by one. Please check all the figures and use the correct number.

- All the figures of section 4 should be provided in a better quality, and the x-axis and y-axis scales should be the same to make it easier to compare the comparison of results.

- The story shear force should be normalised to the total seismic weight of the building, to better comprehend the differences among the structural configurations.

- The overturning moments should be normalised to the stabilising ones, to make it easier to compare the various structural configurations, giving a rapid indication of the structural safety.

- The base shear force should be normalised to the total seismic weight of the building to make it easier to compare results of different structural configurations. 

- All the figures of the same type should have the same scale for the x- and y axes, for a better visual comprehension. 

 

Author Response

Thank you for taking the time to review our manuscript. I’ve carefully considered your feedback and have prepared a detailed response to address your comments. You’ll find my comprehensive reply in the attached file. I appreciate your insights and hope this response fully clarifies the points raised.

Thank you again for your valuable input!

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This manuscript investigates the effectiveness of high-damping rubber bearings in enhancing the seismic behavior of hillside structures, utilizing nonlinear time history analyses on five building configurations. While the study presents simulation results, with great quality of presentation, it is my assessment that this paper does not add to the state of knowledge in the field and does not warrant publication. The vulnerability of hillside structures due to vertical irregularities and asymmetrical distribution of mass and stiffness is already a well-recognized problem in existing literature. The core conclusions, of improved seismic performance with use of rubber isolators, are consistent with the known benefits of seismic isolation systems. The authors themselves state that seismic isolation systems have demonstrated significant effectiveness in enhancing the seismic resilience of structures in experimental and numerical modeling studies. The paper primarily offers a detailed application and quantification of the expected efficacy of base isolation, rather than introducing any new fundamental knowledge.

Author Response

Thank you for taking the time to review our manuscript. I’ve carefully considered your feedback and have prepared a detailed response to address your comments. You’ll find my comprehensive reply in the attached file. I appreciate your insights and hope this response fully clarifies the points raised.

Thank you again for your valuable input!

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

This manuscript attempts to investigate the effectiveness of High-Damping Rubber Bearings (HDRBs) in enhancing the seismic resilience of hillside structures using nonlinear time history (NTH) analysis. Analysis results possesses practical significance in engineering, revealing significant positive effect of HDRBs on key response parameters (e.g. peak roof acceleration and maximum inter-story drift). However, there are some issues that need to be further clarified. A minor revision is recommended.

Q1. It is recommended to supplement the description of the representativeness of six earthquake ground motions in the manuscript, thereby enhancing the applicability of conclusions.

Q2. What are the economic or performance advantages of HDRBs proposed in the manuscript compared to other isolation techniques?

Q3. The influence of key design parameters of HDRBs on the seismic resilience of hillside structures warrants further discussion in the manuscript.

Author Response

Response to Reviewer #5

Thank you for coordinating the review process. We are grateful to Reviewer #5 for their insightful and constructive comments, which have helped us improve the quality of our manuscript. We have addressed each point raised carefully, and our point-by-point responses are detailed below.

Comment Q1: It is recommended to supplement the description of the representativeness of six earthquake ground motions in the manuscript, thereby enhancing the applicability of conclusions.

Response: As requested, we have expanded Section 3.4 to provide a detailed rationale for the six selected records.

We now explicitly state that the records were selected and scaled to be consistent with the target design spectrum per Chinese seismic design code GB50011 guidelines. Furthermore, we have included Table 5 that lists key characteristics of each motion.

Comment Q2: What are the economic or performance advantages of HDRBs proposed in the manuscript compared to other isolation techniques?

Response: This is an excellent point. While the current study focused primarily on the seismic performance advantages of High-Damping Rubber Bearings (HDRBs), we acknowledge that a comprehensive economic analysis is crucial for practical adoption. In terms of performance, HDRBs offer significant advantages, including their simplicity (providing isolation and damping in a single component), stable mechanical properties under varying loads, and excellent durability and environmental resistance compared to systems with lead cores. However, it is often noted that the material and manufacturing costs for HDRBs can be higher than for Lead-Rubber Bearings (LRBs) for certain applications. Therefore, a detailed life-cycle cost analysis (LCA) that weighs the initial investment against long-term benefits—such as reduced repair costs, lower downtime, and superior longevity—is essential to fully justify their economic viability. We concur with the reviewer that this constitutes a valuable direction for future research to complement these performance-focused findings.

Comment Q3: The influence of key design parameters of HDRBs on the seismic resilience of hillside structures warrants further discussion in the manuscript.

Response: The influence of key HDRB design parameters has been further discussed in the revised manuscript (Section 5). The analysis confirms that the selected properties a 2.75s isolation period and 20% damping ratio—were highly effective for this hillside structure. The 2.75s period successfully decouples the building from the dominant energy content of the earthquake ground motions, which is the primary mechanism behind the substantial reductions in acceleration responses (up to 90%). Concurrently, the 20% damping ratio provided optimal energy dissipation, effectively controlling bearing displacements while still mitigating force-based demands, as evidenced by the up to 78% reduction in inter-story drift and 70% reduction in base shear. The discussion now explicitly analyzes this interplay between period lengthening and damping, highlighting how these specific parameters are central to the enhanced seismic resilience demonstrated in the results.

Thank you once again for your time and effort.

 With best regards

Round 2

Reviewer 4 Report

Comments and Suggestions for Authors

The reviewer appreciates the author's response. However, he maintains the initial impression that this paper primarily offers a detailed application and quantification of the expected efficacy of base isolation, rather than introducing any new fundamental knowledge. Despite the updates, it does not warrant publication in this journal. 

Author Response

We thank the reviewer for their feedback. We respectfully disagree with the comment but have chosen an open review to maintain a fair and professional dialogue between the authors and reviewers.