An Off-Site Construction Digital Twin Assessment Framework Using Wood Panelized Construction as a Case Study

Round 1

Reviewer 1 Report

This paper presents an innovative concept (Digital Twin) with offsite construction. 

Even though, the paper presents a concept of the model, that would be great if the authors can include a couple of cases to verify it. 

Abstract needs to be revised to include the key components of an abstract, such as key findings, summary of the method, etc. At present, the background part is too long. 

As presented in Section 2, there are five steps of research method. I reckon it can be further improved to add a part of validation/verification of the developed framework. Thus, it will help your Section 6.3. 

7 Discussion, the authors finished this manuscript with a discussion. However, an article has to have a conclusion. What can be concluded through your framework development and reviews?   

Author Response

Point 1: This paper presents an innovative concept (Digital Twin) with offsite construction. Even though, the paper presents a concept of the model, that would be great if the authors can include a couple of cases to verify it.

Response 1: This is an induction reasoning process, we draw conclusions from specific cases. The framework is designed for organization performance measurement and improvement. The higher-level framework is validated through interviews in which we reviewed ACQBuilit’s construction and production processes. The framework can be further developed for projects. 

Point 2: Abstract needs to be revised to include the key components of an abstract, such as key findings, a summary of the method, etc. At present, the background part is too long.

Response 2: The Abstract is rewritten. Some irrelevant information is abridged from the Introduction.

Point 3: As presented in Section 2, there are five steps of the research method. I reckon it can be further improved to add a part of the validation/verification of the developed framework. Thus, it will help your Section 6.3.

Response 3: We have re-designed the four steps and added a validation step (lines 74 – 90).

Point 4: 7 Discussion, the authors finished this manuscript with a discussion. However, an article has to have a conclusion. What can be concluded through your framework development and reviews?

Response 4: Now the Discussion and Conclusion are separated into two sections (lines 567-606).

Reviewer 2 Report

This study is interesting, but many sections are unclear, and there is no strong logic behind some sections. The authors should improve the quality of the paper significantly.

Off-site construction processes were identified in this study, and four components of an Off-site Construction Digital Twin were defined. These processes, parts, and other maturity assessment tools are used to determine the Off-site Construction Maturity Level. A case study with ACQBuilt, an off-site construction company in Edmonton, Canada, is used to validate and evaluate this assessment framework. This study aims to set the basic framework for future Off-site Construction Digital Twin research.

1. The abstract of the paper is not appropriate. The authors devoted more than half of the abstract to the purpose of the study, while research methodology, findings, research implications, and the paper's originality have not been stated adequately.
2. The keywords should be revised. More appropriate keywords should be selected.
3. The reference style should be changed based on the MDPI reference style.
4. Please use appropriate references for lines 34 to 38.
5. The first paragraph of page 2 explores the research gaps. However, a more comprehensive approach is needed to conclude that there is a considerable research gap in this research area.
6. The last paragraph of section 1 is too long. It should be divided into two or more paragraphs.
7. The proposed goals and the approach are very messy. They should be stated systematically.
8. One of the biggest problems of this research is the literature review. While the authors stated there is no overlap between off-site construction and digital twin, at least they can provide two separate sections to review the related studies to these concepts. Many sections that have been reviewed in section 3 can be moved to the literature review section. Please address the following papers:

• Akbarieh, A., Jayasinghe, L.B., Waldmann, D., Teferle, F.N., 2020. BIM-based end-of-lifecycle decision making and digital deconstruction: Literature review. Sustainability (Switzerland) 12.
• Ayinla, K., Vakaj, E., Cheung, F., Tawil, A.R.H., 2021. A semantic offsite construction digital Twin-Offsite Manufacturing Production Workflow (OPW) ontology, CEUR Workshop Proceedings.
• He, R., Li, M., Gan, V.J.L., Ma, J., 2021. BIM-enabled computerized design and digital fabrication of industrialized buildings: A case study. Journal of Cleaner Production 278.
• Salari, S.A.-S., Mahmoudi, H., Aghsami, A., Jolai, F., Jolai, S., Yazdani, M., 2022. Off-Site Construction Three-Echelon Supply Chain Management with Stochastic Constraints: A Modelling Approach. Buildings 12, 119.
• Tran, H., Nguyen, T.N., Christopher, P., Bui, D.K., Khoshelham, K., Ngo, T.D., 2021. A digital twin approach for geometric quality assessment of as-built prefabricated façades. Journal of Building Engineering 41.
• Yazdani, M., Kabirifar, K., Fathollahi-Fard, A.M., Mojtahedi, M., 2021. Production scheduling of off-site prefabricated construction components considering sequence-dependent due dates. Environmental Science and Pollution Research, 1-17.

9. The first paragraph of page 3 needs further clarification.
10. The logic and flow of figure 2 seem not very logical. Please recheck all stps. In addition, this research methodology should be briefly explained in this section. Furthermore, the caption of figure 2 is not appropriate.
11. Figure 4 is a bit confusing. Please provide a more appropriate figure.
12. I strongly suggest revising the structure of the paper and revising the headings! After heading number 5 there is heading 6.1?!
13. Section 4 is very brief and unclear.
14. Section 5 is suffering from support by appropriate references.
15. Figures 5 and 6 are very unclear. They should be revised. The authors should work on the presentation of the paper.
16. Figure 7 is not a figure; It is a table!
17. Section 6.2 is very hard for a reader to follow. The objective of this section is not clear.
18. The validation of the study is under question.
19. A managerial insight should be added to this paper.
20. While a wide range of limitations is associated with this study, the authors didn’t discuss the limitations of this study in conclusion.

Author Response

Point 1: The abstract of the paper is not appropriate. The authors devoted more than half of the abstract to the purpose of the study, while research methodology, findings, research implications, and the paper’s originality have not been stated adequately.

Response 1: The authors have added the research methodology, outcomes, and implications in the Abstract

Point 2: The keywords should be revised. More appropriate keywords should be selected.

Response 2: We have added some keywords.

Point 3: The reference style should be changed based on the MDPI reference style.

Response 3: We have modified the reference style.

Point 4: Please use appropriate references for lines 34 to 38.

Response 4: The authors have added two references for it. Now, this part is between line 38-42.

[3]           W. Kritzinger, M. Karner, G. Traar, J. Henjes, and W. Sihn, “Digital Twin in manufacturing: A categorical literature review and classification,” IFAC-PapersOnLine, vol. 51, no. 11, pp. 1016–1022, Jan. 2018, doi: 10.1016/j.ifacol.2018.08.474.

[4]           M. Grieves, “Digital Twin: Manufacturing Excellence through Virtual Factory Replication,” Mar. 2015.

Point 5: The first paragraph of page 2 explores the research gaps. However, a more comprehensive approach is needed to conclude that there is a considerable research gap in this research area.  

Response 5: We added a paragraph to clarify research problems from lines 47 to 55.

Point 6: The last paragraph of section 1 is too long. It should be divided into two or more paragraphs.

Response 6: We have deleted some parts and moved the elaboration of the difference between the manufacturing industry and construction industry in section 5.

Point 7: The proposed goals and the approach are very messy. They should be stated systematically.  

Response 7: The goals and approach are rewritten from line 56 - 72. Hope that helps clarify things!

Point 8: One of the biggest problems of this research is the literature review. While the authors stated there is no overlap between off-site construction and digital twin, at least they can provide two separate sections to review the related studies. Many sections that have been reviewed in section 3 can be moved to the literature review section. Please assess the following papers:

• Akbarieh, A., Jayasinghe, L.B., Waldmann, D., Teferle, F.N., 2020. BIM-based end-of-lifecycle decision making and digital deconstruction: Literature review. Sustainability (Switzerland) 12.
• Ayinla, K., Vakaj, E., Cheung, F., Tawil, A.R.H., 2021. A semantic offsite construction digital Twin-Offsite Manufacturing Production Workflow (OPW) ontology, CEUR Workshop Proceedings.
• He, R., Li, M., Gan, V.J.L., Ma, J., 2021. BIM-enabled computerized design and digital fabrication of industrialized buildings: A case study. Journal of Cleaner Production 278.
• Salari, S.A.-S., Mahmoudi, H., Aghsami, A., Jolai, F., Jolai, S., Yazdani, M., 2022. Off-Site Construction Three-Echelon Supply Chain Management with Stochastic Constraints: A Modelling Approach. Buildings 12, 119.
• Tran, H., Nguyen, T.N., Christopher, P., Bui, D.K., Khoshelham, K., Ngo, T.D., 2021. A digital twin approach for geometric quality assessment of as-built prefabricated façades. Journal of Building Engineering 41.
• Yazdani, M., Kabirifar, K., Fathollahi-Fard, A.M., Mojtahedi, M., 2021. Production scheduling of off-site prefabricated construction components considering sequence-dependent due dates. Environmental Science and Pollution Research, 1-17.

Response 8:  The literature review is re-organized. We added a couple of references. It comprises of two sections dedicated to the two topics respectively.

Point 9: The first paragraph of page 3 needs further clarification.

Response 9: This paragraph was dedicated to providing information on the company we work with. It was weakly connected to research methodologies. We have merged this paragraph into the previous one, to establish stronger connections between the company and our research design. (lines 74 – 90)

Point 10: The logic and flow of figure 2 seem not very logical. Please recheck all steps. In addition, this research methodology should be briefly explained in this section. Furthermore, the caption of figure 2 is not appropriate.  

Response 10: Figure 2 is redone based on the “goals” stated in the last paragraph of the Introduction. We have also modified the caption.

Point 11: Figure 4 is a bit confusing. Please provide a more appropriate figure.  

Response 11: We have changed the presentation of this figure.

Point 12: I strongly suggest revising the structure of the paper and revising the headings! After heading number 5 there is heading 6.1?!

Response 12: We have revised the headings and modified the structure of the paper.

Point 13: Section 4 is very brief and unclear.  

Response 13: We have added a figure to illustrate the off-site construction steps of ACQBuilt. Also have modified the paragraph to clarify the logic.

Point 14: Section 5 is suffering from support by appropriate references.

Response 14: We have added references to the statements.

Point 15: Figures 5 and 6 are very unclear. They should be revised. The authors should work on the presentation of the paper.

Response 15: Figure 5 is represented. Figure 6 is replaced.

Point 16: Figure 7 is not a figure. It is a table!

Response 16: The mistake is corrected.

Point 17: Section 6.2 is very hard for a reader to follow. The objective of this section is not clear.

Response 17: This section is dedicated to explaining the design of the questionnaire, and how to use Table [1] as a reference. Figure 7 now helps explain section 6.2.

Point 18: The validation of this study is under question.

Response 18: This is an induction reasoning process, we draw conclusions from specific cases. The framework is designed for organization performance measurement and improvement. The higher-level framework is validated through interviews in which we reviewed ACQBuilit’s construction and production processes. The framework can be further developed for projects.  

Point 19: A managerial insight should be added to this paper.

Response 19: The idea of an Assessment Framework comes up from Quality Management, and how the framework is organized referenced a couple of assessment tools (Section 6.1).

Point 20: While a wide range of limitations is associated with this study, the authors didn’t discuss the limitations of this study in the conclusion.

Response 20: Now the discussion and conclusion are separated into two parts. The limitations are stated in the Discussion.

Reviewer 3 Report

The title of the manuscript is actually interesting but does not reflect what the paper produced. Below are my comments for every section:

• Abstract: The abstract does not reflect a clear rationale with sufficient background. The authors need to identify the gap clearer, and highlight the contributions.
• Introduction: the narrative is quite weak and research gap is not identified clearly. Many arguments are not supported by dated references.
• Methodological Approach: this part should be the backbone of this research, and it requires significant changes and restructuring to portray clearer understanding of process followed. It is not clear "how" and "why" authors have followed the process they outlined in the paper.
• Findings: This seems to be blended across different sections in the paper, and it needs to be separated under different section.
• Discussion: the practical implications of this research are not clear, and authors need to expose hoe this research adds to body of knowledge. 

Author Response

Point 1: Abstract: The abstract does not reflect a clear rationale with sufficient background. The authors need to identify the gap clearer, and highlight the contributions.

Response 1: We have rewritten the Abstract so it now identifies the gap and highlights the contributions.

Point 2: Introduction: the narrative is quite weak and the research gap is not identified clearly. Many arguments are not supported by dated references.

Response 2: Some redundant information is deleted. The research gap, research goal, and motivation are rewritten (lines 45 – 72).

Point 3: Methodological Approach: this part should be the backbone of this research, and it requires significant changes and restructuring to portray a clearer understanding of the process followed. It is not clear “how” and “why” authors have followed the process they outlined in the paper.

Response 3: The methodology is redesigned. Now it is a four-step process (lines 74 – 90).

Point 4: Findings: This seems to be blended across different sections in the paper, and it needs to be separated into different sections.

Response 4: We have revised it in the conclusion (lines 563 – 591).

Point 5: Discussion: the practical implication of this research are not clear, and the authors need to expose how this research adds to a body of knowledge.

Response 5: Current application is done in a fragmented fashion, and organizations are suffering from toggling between different systems, jargon, and software. This assessment framework is a knowledge tool that cooperates with both industry experiences (process mapping) and academia (concept of digital twin, and the Off-Site Construction Digital Twin Model). The questionnarie is designed for easy use by organizations to identify performance measurement and improvement.

Round 2

Reviewer 2 Report

the authors could significantly improve the quality of the paper. Just pl3ease double-check the headings, it seems there are two "section 7".

Author Response

Thank you for your valuable feedback, and we have reviewed the headings and done cross-proofreading.

Reviewer 3 Report

Dear Authors,

Many thanks for amending the manuscript and improving the quality across various sections, but there are some fundamental issues that need to be addressed so that the work can be seamlessly publishable:

Introduction: whilst the narrative has improved, it is still not clear where the gap is, in other words, why digital twin? why for Wood Panelised? what is the main contribution?

Literature review: I think that this side of the manuscript is fine, but it may need some re-structuring to ensure that flow of the argument is logical.

Methodology: The methodological approach need to be more clarified as you have made many drastic jumps from data, to findings to analysis, so I would suggest that the diagram you have on methodology to be changed or improved to provide more clarity.

Results and analysis: this section is good, and logical, but needs revisiting to ensure that the structure is logically correct.

Discussion: this section requires major amendments, and in fact highlighting what is the significance of this study, why did you do research, who is benefiting, how your research is going to inform future work.

Author Response

Point 1: Introduction: whilst the narrative has improved, it is still not clear where the gap is, in other words, why digital twin? Why for Wood Panelized? What is the main contribution?

Response 1: We have added more information to explicitly answer the questions raised in Point 1. (Lines 37 – 48, 55 - 60, 74 – 76). This section is also restructured.

Point 2: Literature review: I think that side of the manuscript is fine, but it may need some restructuring to ensure that flow of the argument is logical.  

Response 2: Heading 3.2.1 is moved to a proper place. (Line 190) The part reviewing Virtual Design Construction is merged into Section 3.2.2. We have deleted some redundant information in the review of VDC so the remainder can smoothly merge into the main flow.

Point 3: Methodology: The methodological approach need to be more clarified as you have made many drastic jumps from data to findings to analysis, so I would suggest that the diagram you have on methodology be changed or improved to provide more clarity.

Response 3: We have elaborated on the process we have gone through when moving from one step to the next, to establish a stronger connection between steps. We have elaborated figure 2, and modified the text from lines 78 – 87.

Point 4: Results and analysis: this section is good, and logical, but needs revisiting to ensure that the structure is logically correct.

Response 4: We have restructured this part. (Lines 495 – 504, 544 – 561)

Point 5: Discussion: this section requires major amendments, and in fact highlighting what is the significance of this study, why did you research, who is benefiting, how your research is going to inform future work.

Response 5: We have added some information in section 8 Conclusion to address questions raised in Point 5 (Lines 564 – 579). Discussion is now merged into Section 7: Results and Discussion to reduce confusion.

Round 3

Reviewer 3 Report

Dear authors,

So many thanks for responding to the suggested comments. Below are few more details that are required to do before publication:

1. Introduction: try to justify the rationale behind focusing on Wood Panelized, as this is still weak.
2. Literature review: sufficient review is provided but make sure that english/grammer check is appropriate.
3. Methodology: improved and clear
4. Results and Discussion: Similar comments to the introduction, please make sure that the findings refer back to Wood Panelized, and clearly outline how this research can support advancing on existing body of knowledge.
5. Conclusion: make sure that it is clear and logical. 

Author Response

Point 1: Introduction: Introduction: try to justify the rationale behind focusing on Wood Panelized, as this is still weak.

Response 1: We have added more information to explicitly answer the question raised in Point 1. (Lines 54 - 63).

Point 2: Literature review: sufficient review is provided but make sure that english/grammer check is appropriate.

Response 2: We have proofread the manuscript.

Point 3: Methodology: Improved and clear

Response 3: Thank you for your comments.

Point 4: Results and Discussion: Similar comments to the introduction, please make sure that the findings refer back to Wood Panelized, and clearly outline how this research can support advancing on existing body of knowledge.

Response 4: We have added this information. (Lines 565-571)

Point 5: Conclusion: make sure that it is clear and logical.

Response 5: The first and second paragraph is merged together and restructured. (Lines 575 – 595).