Numerical Analysis of the Creep and Shrinkage Experienced in the Sydney Opera House and the Rise of Digital Twin as Future Monitoring Technology
Round 1
Reviewer 1 Report
The subject matter of the paper is within the scope of the journal and has a good technical quality. The article draws attention to the phenomenons of creep and shrinkage of concrete occuring in the Sydney Opera House. To solve the scientific problem numerical analysis were used. The authors carried out a wonderful work, however there are some observations and comments raised which the authors needs to address or correct:
(1) For the enrichment of the article it would be good to show a current photo of the Opera House.
(2) Please specify how the important parameter t0 was determined. After so many years since putting the construction into service certainly it was not easy. Are there any historical data on this topic?
(3) How can the salinity from the ocean affect the rheology and the weakening of concrete in the Sydney Opera House structure. Please discuss this particular problem.
(4) Significant impact on the rheological parameters of the concrete, mainly shrinkage, has the type of cement used. Does the assumption that rapid hardening high strength cement has been used to perform the Sydney Opera has some confirmation in the preserved projects, or is it just an assumption of the authors.
(5) The description of the used numerical procedure (Section 4.2.3) are not sufficiently presented and only basic results of simulations are mentioned. For example, it is required to summarizes information about types of elements and numbers of nodes used in numerical calculations.
(6) The article presents an analysis of the assessment of concrete wear in a structure based on 2 rheological parameters. The full analysis should also include an assessment of the structure of the material in the light of the occurring microcracks. Are such tests planned?
In this field, I think, the authors must strengthen the References section with the references that use this experimental technique. It is therefore required to discuss and cite these papers:
“An assessment of microcracks in the Interfacial Transition Zone of durable concrete composites with fly ash additives”, Composite Structures, 2018.
“Evaluation of morphology and size of cracks of the Interfacial Transition Zone (ITZ) in concrete containing fly ash (FA)”, Journal of Hazardous Materials, 2018.
Author Response
Reviewer’s comments ( First Reviewer ) | Authors’ reply |
(1) For the enrichment of the article it would be good to show a current photo of the Opera House.
| A recent photo of the Opera House was added to the article. |
(2) Please specify how the important parameter t0 was determined. After so many years since putting the construction into service certainly it was not easy. Are there any historical data on this topic? | Of course, t0 is one of the significant factors. However, determination of the t0 is very complicated. Also, we did not have access to the historical data. In the current analysis , an arbitrary number was assumed as t0. |
(3) How can the salinity from the ocean affect the rheology and the weakening of concrete in the Sydney Opera House structure? Please discuss this particular problem.
| This is a unique question. Definitely, the salinity from the ocean can crucially influence on the time deponent analysis as well as deformation of the casted concrete in the Opera House. This is an individual problem and it needs to allocate a spate research paper to that topic. At the moment, the evaluation the effect of the salinity from the ocean is out of the scope of the current paper. However, as indicated, this is very interesting and important topic. This topic can be suggested for future research. |
(4) Significant impact on the rheological parameters of the concrete, mainly shrinkage, has the type of cement used. Does the assumption that rapid hardening high strength cement has been used to perform the Sydney Opera has some confirmation in the preserved projects, or is it just an assumption of the authors.
| Having access to the some key technical parameters form Opera House is currently a significant patent. Refer to the current link, https://sydney.edu.au/news-opinion/news/2016/09/06/conserving-a-concrete-masterpiece.html, it is almost impossible or should be very expensive to request for collecting some data which are relevant to the major parameters in creep and shrinkage. At the moment, some reasonable assumptions by authors were assumed to comprehensively undertake the simulations. |
(5) The description of the used numerical procedure (Section 4.2.3) are not sufficiently presented and only basic results of simulations are mentioned. For example, it is required to summarizes information about types of elements and numbers of nodes used in numerical calculations.
| I would like to appreciate for the suggestion. A further explanations regarding to how to develop the finite element models as well as defining some initial input parameter were added to the article. |
(6) The article presents an analysis of the assessment of concrete wear in a structure based on 2 rheological parameters. The full analysis should also include an assessment of the structure of the material in the light of the occurring microcracks. Are such tests planned? In this field, I think, the authors must strengthen the References section with the references that use this experimental technique. It is therefore required to discuss and cite these papers: “An assessment of microcracks in the Interfacial Transition Zone of durable concrete composites with fly ash additives”, Composite Structures, 2018. “Evaluation of morphology and size of cracks of the Interfacial Transition Zone (ITZ) in concrete containing fly ash (FA)”, Journal of Hazardous Materials, 2018.
| The suggested references were added to the article.
Currently, there is a substantial research plan is under way in the Opera House ( https://pacetoday.com.au/robots-sensors-sydney-opera-house/), which is very capital intensive.
Professor Gianluca Ranzi, University of Sydney said: “The project has provided the next generation of engineers with a real-world opportunity to develop their skills and increase their understanding of heritage-building conservation.“The use of advanced technology has provided the basis for the development and prototyping of an effective inspection strategy applicable to twentieth century concrete buildings.” Located in a harsh marine environment the Opera House requires vigilant maintenance and active conservation practices to ensure its beauty and integrity are safeguarded. Three primary areas of the Opera House concrete were studied, based on their heritage and structural significance: the Sails structure; the Roof Pedestals; and the Northern Broadwalk under-structure However, the suggested references were added to the article.
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Reviewer 2 Report
This paper needs some revisions, which should be considered:
Introduction is incomplete. It is required to add some references to show which types of shrinkage creates some problems and in the research topics what solutions have been proposed for concrete. Therefore, its recommended to use the following references as simple solutions to control shrinkage in the buildings and what the fundamental concept of shrinkage is:
https://www.sciencedirect.com/science/article/pii/S0950061818323043
https://ascelibrary.org/doi/abs/10.1061/(ASCE)MT.1943-5533.0001918
In Table 3, it is required to report elastic modulus
It is required to explain more about the constitutive model used for modeling of materials. This reference (https://www.sciencedirect.com/science/article/pii/S026382231630695X) could be useful for understanding the concept and modeling of the shells.
In figures 2 and 3, it is recommended to use Von Mises stresses.
Author Response
Reviewer’s comments second Reviewer’s | Authors’ reply |
Introduction is incomplete | A further explanation and clarification was added. Individually, a separate statement was indicated why this research is significant in the introduction. |
It is required to add some references to show which types of shrinkage creates some problems and in the research topics what solutions have been proposed for concrete. Therefore, its recommended to use the following references as simple solutions to control shrinkage in the buildings and what the fundamental concept of shrinkage is: https://www.sciencedirect.com/science/article/pii/S0950061818323043 https://ascelibrary.org/doi/abs/10.1061/(ASCE)MT.1943-5533.0001918 https://link.springer.com/article/10.1007/s12205-017-1714-3 https://www.icevirtuallibrary.com/doi/abs/10.1680/jcoma.16.00077
| I would like to thank about the suggested references. The relevant references were considered. |
In Table 3, it is required to report elastic modulus | The elastic modulus was already provided. |
It is required to explain more about the constitutive model used for modelling of materials. This reference (https://www.sciencedirect.com/science/article/pii/S026382231630695X) could be useful for understanding the concept and modelling of the shells.
| I would like to thank about the suggested references. The relevant references were considered. |
In figures 2 and 3, it is recommended to use Von Mises stresses. | The presented results are based on the major principal stresses ( or governed stresses), Von Mises stresses is based on the combination of the principal stresses, thus, an individual stress at a particular govern direction can be more precise rather than using a combination of the stresses. |
Reviewer 3 Report
1.The motivation of doing this numerical simulation is not clear in this paper. 2. How the authors decided dead load? 3. Mesh quality section need reference for mesh selection and its affect on final results 4. Authors can propose some future work using BIM analysis. It will improve the accuracy of obtain results. 5. Some typos mistakes are there. in section 4.
Author Response
Reviewer’s comments (The Third Reviewer ) | Authors’ reply |
The motivation of doing this numerical simulation is not clear in this paper. | The main motivation of the current research is to determine a cost-effective method to evaluate the time-dependent deformation of the structural elements in the Opera House. Currently, there is a substantial research plan is under way in the Opera House ( https://pacetoday.com.au/robots-sensors-sydney-opera-house/), which is very capital intensive. The current numerical method can be extended to have a cost-effective replaced solution against the current field measurement project which is very expensive. |
2. How the authors decided dead load? | The dead load is the calculated self-weight of the structural and non-structural elements by the Finite Element Package (STRAND 7). |
3. Mesh quality section need reference for mesh selection and its affect on final results. | The relevant explanation about the mesh quality was broadly discussed. |
4. Authors can propose some future work using BIM analysis. It will improve the accuracy of obtain results. | The current research is relevant to maintaining the icon/heritage building. Thus, it is relevant to structural protect a historical building, thus, this is not relevant to the future building as well as the future design that we could take into account the BIM analysis. Sydney Opera House Director, Building Greg McTaggart said: “The complexity of the Sydney Opera House structure called for a creative response to its conservation. The timing of the Getty grant aligned with the near-completion of the Opera House’s Conservation Management Plan (4th Edition) and advances in our Building Information Management system. What is unique and innovative about this project is that we will be able to seamlessly integrate heritage policies with the day-to-day management of the building fabric.”
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5. Some typos mistakes are there. in section 4.
| I would like appreciate for the comment. The section 4 was revised. |
Round 2
Reviewer 1 Report
The required corrections have been made. Thus, I suggest to accept the manuscript in its current form
Reviewer 2 Report
Most comments were considered in the revised version.