Towards Sustainable Structure of Tall Buildings by Significantly Reducing the Embodied Carbon

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper presents the life-cycle assessment analysis on the steel and concrete structures through five different structural options, and comments the combination of steel-concrete composite and adoption of recyclable materials on the carbon-emission reduction. Overall, this paper is well-written, but following comments should be addressed before further consideration.

 

1. The authors mention that steel and concrete are the two primary materials used in high-rise building, note the cementitious materials. e.g. ECC are also employed in some structural component, which is made of supplementary cementitious materials. e.g. Fly ash to reduce the cement consumption, so it could be regarded as the sustainable material. suggest the author supplement addition reference on these materials. e.g, https://doi.org/10.1016/j.jobe.2025.112007;
2. Some statements are repeated in Abstract and Introduction, please rephrase or delete the repeated sentences.
3. In introduction, the author state “Park et al. studied the optimal design of steel-reinforced concrete columns in high- rise buildings, optimizing the weight of steel and concrete used to minimize construction costs and CO2 emissions”, this is true. Note that steel-reinforced concrete columns with high strength materials can further reduce the member size and hence further minimize construction costs and CO2 emissions, there are substantial research available confirm this: e.g. https://doi.org/10.1016/j.jobe.2023.107886; https://doi.org/10.1016/j.engstruct.2021.112507;
4. Prior to conduct the life-cycle assessment of the five structure options, did the author ensure the safety of these structures, are they appropriately designed against seismic hazard, wind……
5. The author may illustrate why the five structural alternatives "provide functionally equivalent structural performance”
6. In conclusion, the author states “The analysis revealed that although the RC structure consumed over 600% more total material mass than steel structures with equivalent structural performance, the difference in embodied carbon intensity between the steel and RC cases was less than 20%”. Please explain this. Concrete is much more carbon-intensive than steel, why the embodied carbon intensity between steel and RC structures is so small.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The authors are  encouraged to seek the assistance of a colleague proficient in professional written English to improve the manuscript's clarity and readability.

Author Response

1. The authors mention that steel and concrete are the two primary materials used in high-rise building, note the cementitious materials. e.g. ECC are also employed in some structural component, which is made of supplementary cementitious materials. e.g. Fly ash to reduce the cement consumption, so it could be regarded as the sustainable material. suggest the author supplement addition reference

• The suggested reference has been reviewed and added to the literature review due to its high relevance to the study.

2. Some statements are repeated in Abstract and Introduction, please rephrase or delete the repeated sentences.

• The entire introduction section has been revised for better clarity and scientific writing while maintaining key content.

3. In introduction, the author state “Park et al. studied the optimal design of steel reinforced concrete columns in high- rise buildings, optimizing the weight of steel and concrete used to minimize construction costs and CO2 emissions”, this is true. Note that steel-reinforced concrete columns with high strength materials can further reduce the member size and hence further minimize construction costs and CO2 emissions, there are substantial research available confirm this:

• One of the suggested references has been added to the literature review due to its high relevance to the study.

4. Prior to conduct the life-cycle assessment of the five structure options, did the author ensure the safety of these structures, are they appropriately designed against seismic hazard, wind……

• These structural systems have been well-established as we mentioned in the manuscript. Many tall buildings have been designed and built according to these systems. As such, they are always in accordance with the requirements of the code that imply safety and constructability. In addition, the objective of this paper, as we stated, is to show that well designed structural systems using the existing well established structural systems can reduce their environmental impacts due to efficiency, optimized horizontal and vertical structural elements, and more.

5. The author may illustrate why the five structural alternatives "provide functionally equivalent structural performance

• To clarify this, 1.2. motivations & objectives has been added and the 2.1 Structural Systems Development and Analysis has been revised.

6. In conclusion, the author states “The analysis revealed that although the RC structure consumed over 600% more total material mass than steel structures with equivalent structural performance, the difference in embodied carbon intensity between the steel and RC cases was less than 20%”. Please explain this. Concrete is much more carbon-intensive than steel, why the embodied carbon intensity between steel and RC structures is so small.

• To clarify this question, additional paragraphs have been added to p. 15 (blue-highlighted section), and the conclusion section has also been revised.

 

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

The paper titled (manuscript ID sustainability-3490720), “Towards sustainable structure of tall buildings: By significantly reducing the embodied carbon,” is sufficiently attractive from an academic and scientific perspective, and is succinctly described in relation to its background and previous studies.

Similarly, the design of the research study, its methodology, objectives, and proposals have been adequately and precisely defined.

However, I believe the discussion presented needs to be clarified, particularly in the proposed cases in the different comparative emission analyses and how they correlate with the cradle-to-grave case analysis. It is confusing.

1. Can you expand these correlations, relating them to the bibliographic data shown?

The representation of results is adequate but appears complex and inconclusive in some cases. It is cluttered, and in some instances, more confusing than clarifying.

2. In the case of Figure 7, there are no noticeable differences that justify the presence of this illustration. Either expand it in detail, on an ascending and justified scale, or fragment the presented cases. Could a more academic approach be provided in this particular case?

Finally, the conclusions do not seem to be well correlated-supported by the vast amount of results. Nor is there a clear alignment of the conclusions with the bibliographic references included in the article. They are not conclusive.

3. Could the conclusions be established more forcefully and ordered in a hierarchical index that shows the greater or lesser amount of “achievements” obtained throughout the empirical phase and its results?

Sincerely.

Author Response

I believe the discussion presented needs to be clarified, particularly in the proposed cases in the different comparative emission analyses and how they correlate with the cradle-to-grave case analysis. It is confusing.

1. Can you expand these correlations, relating them to the bibliographic data shown?

• In order to refine the results and discussion section, the entire section has been updated with an emphasis on the key focuses of both the cradle-to-grave and cradle-to-cradle approaches. Moreover, beyond presenting the LCA results, the manuscript has been revised to illustrate their correlations with structural development and LCA analysis.

2. In the case of Figure 7, there are no noticeable differences that justify the presence of this illustration. Either expand it in detail, on an ascending and justified scale, or fragment the presented cases. Could a more academic approach be provided in this particular case?

• Figure 7 has been updated.

3. Could the conclusions be established more forcefully and ordered in a hierarchical index that shows the greater or lesser amount of “achievements” obtained throughout the empirical phase and its results?

• The conclusion section has been revised to clearly highlight and summarize the findings from both the cradle-to-grave and cradle-to-cradle analyses, along with key research questions related to the proposed structural system development. Previously vague or irrelevant text has been reviewed and removed.

Reviewer 3 Report

Comments and Suggestions for Authors

In this paper the authors present the building embodied carbon through case LCA assessment. Generally, this is well-grounded case analysis related to the important construction carbon neutrality. The paper is carefully written, in the introduction section most of the previous studies are discussed and the goal of the study is explicitly stated. Having in mind that the research paper should be of wider academic concern is related to the lack of scientific contribution - there are no new methodology and analysis. The available structural analysis and building LCA evaluation have been analyzed using basic tool and handy platform statistics and the results have confirmatory nature. As a result, paper's style is more of a case outcomes report (which is very useful having significant practical value for local tall building than what would be considered a scientific paper. Thus, I recommend the authors to think a little bit about scientific contribution.
Please find below several suggestions which might be considered before publishing:
1. Having in mind the concerned urban environment, building type, scale and materials. Why embodied carbon should be mainly investigated, compared to other LCA indicators or factors.
2. What are the key scientific questions for the regional case study?
3. Please discuss the representativeness of the chosen 60-story high-rise building. How about the influence of carbon emission standards or construction level codes and benchmark comparison worldwide.
4. Provide a strong justification for the chosen database and platforms of LCA tool or why they are particularly suited to this study over alternative approaches.
5. What could be the different impact mechanisms behind building structures and materials, on embodied carbon.
6. Re-structure the content in a more inductive and scientific manor. For instance, integrate the literature review and objective sections into introduction with sub-section headings. Add keywords, and refine and conclusion part with several short bullets depicting main findings as well as limitations.
7. Clarify the novelty and research value with the study? I cannot see the significant contribution of the present study that could make to the enrichment of the case building, or application reference for other places.

Author Response

1. Having in mind the concerned urban environment, building type, scale and materials. Why embodied carbon should be mainly investigated, compared to other LCA indicators or factors.

• The early parts of the introduction section and 3.2. Life Cycle Assessments Focusing on Embodied Carbon have been revised to clearly address this question.

2. What are the key scientific questions for the regional case study?

• Please find the newly updated 1.2 Motivations & Objectives, which include the key scientific questions of the study.

3. Please discuss the representativeness of the chosen 60-story high-rise building. How about the influence of carbon emission standards or construction level codes and benchmark comparison worldwide.

• We chose a 60-story building because it is a good representative of what we are looking for in choosing the five structural systems introduced in the paper.

4. Provide a strong justification for the chosen database and platforms of LCA tool or why they are particularly suited to this study over alternative approaches.

• Please find the newly added paragraph on p.10, which explains why this particular tool was selected for this study, along with additional references.

5. What could be the different impact mechanisms behind building structures and materials, on embodied carbon.

• The updated conclusion section now includes responses to this question, outlining the study's limitations and suggestions for future research.

6. Re-structure the content in a more inductive and scientific manor. For instance, integrate the literature review and objective sections into introduction with sub-section headings. Add keywords, and refine and conclusion part with several short bullets depicting main findings as well as limitations.

• Please find the fully reconstructed introduction section. The remaining parts of the manuscript have also been reviewed and updated for greater cohesion and scientific clarity.

7. Clarify the novelty and research value with the study? I cannot see the significant contribution of the present study that could make to the enrichment of the case building, or application reference for other places.

• To address this question, we have added Section 1.2, Motivations & Objectives, which outlines the key research questions and contributions of this study.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors,

After the second review, I consider that the revised version of the article is well-prepared. The suggested modifications have been addressed, making the article suitable from the perspective of this review.

Sincerely

 

Author Response

The manuscript has been carefully reviewed, and we have corrected any grammatial errors and enhanced the clarity of the paper. Additionally, the abstract has been polished.

Reviewer 3 Report

Comments and Suggestions for Authors

After careful check the revised version and author response, I suggest paper accepted for publication, since authors have addressed the last review comments and made significant improvement.

Comments on the Quality of English Language

 The English could be improved to more clearly express the research.

Author Response

The manuscript has been carefully reviewed, and we have corrected any grammatial errors and enhanced the clarity of the paper. Additionally, the abstract has been polished.