Fire Resistance in Screwed and Hollow Core Wooden Elements Filled with Insulating Material
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis manuscript presents a study on the thermal responses of timber wall considering the fire protection systems. The manuscript could be accepted if the following questions can be addressed:
1. Fig.3, it seems that the convection inside the cavity is not well considered. Instead, the model adopted the simplified method. Is the temperature in the cavity same?
2. The numerical model is not verified by the experimental studies although the numerical studies are comprehensive.
3. Regarding to the case HOLL, the GP board is bonded with the rib or using the screw?
Author Response
Comments and Suggestions for Authors
This manuscript presents a study on the thermal responses of timber wall considering the fire protection systems. The manuscript could be accepted if the following questions can be addressed:
- Fig.3, it seems that the convection inside the cavity is not well considered. Instead, the model adopted the simplified method. Is the temperature in the cavity same?
ANSWER – The authors thank the reviewer for his time detailed review and constructive comments and suggestions. Changes to the article have been identified and highlighted in blue.
Figure 1 represents the representative meshes and element types used in all simulations. In chapter 3.3 ‘’ The boundary conditions’’ are written and explained. Inside the cavity, radiation and convection are imposed with the temperature evolution through the curves FG_HOL_ST, FG_HOL_TS, or FG_HOL, as represented in the models in Figure 4.
- The numerical model is not verified by the experimental studies although the numerical studies are comprehensive.
ANSWER – The authors thank the reviewer. The numerical model was previously developed and experimentally validated by another author as identified in research [6-7], as referred to in ‘’1. Introduction’’.
- Regarding to the case HOLL, the GP board is bonded with the rib or using the screw?
ANSWER – In models HOLL and FG_HOLL the GP board are bonded with ribs. This information was included in the manuscript, thank you. The models with designations ST or TS include the screws elements.
Reviewer 2 Report
Comments and Suggestions for Authors1. This study explores the fire resistance of hollow wood walls protected by gypsum boards and filled with insulation materials under fire conditions. This research direction has practical application value, especially in building energy conservation and fire safety.
2. This paper briefly discusses the changes in thermal conductivity of insulating materials (such as fiberglass boards) and the influence of internal structures.
3. This paper's analysis of the influence of steel screw threads on fire resistance is relatively simple. It is not clear how to replace steel screw simulation in numerical simulation, and the physical mechanism behind it and its specific performance in practical applications are not discussed in depth. The physical mechanism of the influence of steel screw threads on fire resistance should be explored in depth, and more practical suggestions should be provided in combination with the specific performance in practical applications.
4. The writing and expression logic of the article are not clear, especially the abstract writing cannot grasp the key points, and the text expression is poorly readable.
5. The introduction lacks the evolution of the focus theme;
Comments on the Quality of English LanguageThe writing and expression logic of the article are not clear, especially the abstract writing fails to grasp the key points and the readability of the text is poor.
Author Response
Comments and Suggestions for Authors
- This study explores the fire resistance of hollow wood walls protected by gypsum boards and filled with insulation materials under fire conditions. This research direction has practical application value, especially in building energy conservation and fire safety.
- This paper briefly discusses the changes in thermal conductivity of insulating materials (such as fiberglass boards) and the influence of internal structures.
- This paper's analysis of the influence of steel screw threads on fire resistance is relatively simple. It is not clear how to replace steel screw simulation in numerical simulation, and the physical mechanism behind it and its specific performance in practical applications are not discussed in depth. The physical mechanism of the influence of steel screw threads on fire resistance should be explored in depth, and more practical suggestions should be provided in combination with the specific performance in practical applications.
ANSWER 1/2/3– The authors thank the reviewer for the time spent and the review, as well as for the constructive comments made. The authors rewrote the manuscript including more explanation in chapter ‘’4.2. The temperature in the models at the fire resistance’’ with more studies [25-27] to the fire performance of the use of screws for wooden connections, the use of high-strength steel screws, and the significant structural changes in the steel material strongly dependent on the temperature reached.
- The writing and expression logic of the article are not clear, especially the abstract writing cannot grasp the key points, and the text expression is poorly readable.
- The introduction lacks the evolution of the focus theme.
ANSWER 4/5– The authors rewritten the Introduction and the Abstract to give more relevance to the key points of the work, focus on the subject, and present many other applications in the use of the wall partitions. Also, the manuscript was carefully revised to increase its quality.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe study is interesting and well-written however the size of the work is not sufficient enough to publish it as an article. I recommend publishing it as a technical note.
Author Response
The study is interesting and well-written however the size of the work is not sufficient enough to publish it as an article. I recommend publishing it as a technical note.
ANSWER – The authors thank the reviewer for his time and detailed review. As a recommendation, the authors included the proposed publication as a technical note, page 1 at the top.
Reviewer 4 Report
Comments and Suggestions for Authors1. In Figure 2, there should be no solid line on the gypsum board (except the dimension marking line).
2. The specific heat capacity data in Table 2 is wrong, it should be one thousandth of the current data. Are the results of the simulation based on the current data accurate and valid?
3. What is the meaning of Density ratio in Table 3?
4. In Table 5, the specific heat capacity of gypsum board at 135 ℃ is 25kJ/KgK. Is it correct?
5. What is the meaning of the FG_HOLL (1) curve, and why is it set up?
6. In Figure 8, why is the temperature distribution on the upper surface of FG_HOL facing the fire source significantly different from other surfaces? There are no displays of temperature distributions in the interior containing fiberglass insulation filler，why?
Author Response
- In Figure 2, there should be no solid line on the gypsum board (except the dimension marking line).
ANSWER – The authors thank the reviewer for his time and detailed review, constructive comments, and suggestions to improve our manuscript. Figure 2 was fixed.
- The specific heat capacity data in Table 2 is wrong, it should be one thousandth of the current data. Are the results of the simulation based on the current data accurate and valid?
ANSWER – The authors thank a lot the reviewer. It was only a mistake in the written manuscript. All values in Table 2 were corrected.
- What is the meaning of Density ratio in Table 3?
ANSWER – The wood density is a function of the moisture content, as a ratio presented in Table 3, of an initial moisture content of 12%, referred to in [12]. Density ratio is a value that is multiplied by the density of 480 kg/m3 at 20 °C.
- In Table 5, the specific heat capacity of gypsum board at 135 ℃ is 25kJ/KgK. Is it correct?
ANSWER – Yes, the value of 25kJ/kgK is correct, representing one of the peaks where the water dissociates from gypsum, as referred to in [4,12,20].
- What is the meaning of the FG_HOLL (1) curve, and why is it set up?
ANSWER – FG_HOL (1) model represents the insulation material as a solid mesh in the cavity. In this model, the temperature field was obtained until the fiberglass degradation. Then, the combination with the internal temperature calculated in the HOLL model (with additional SURF and LINK elements) allows the final combination to be used for temperature cavity evolution in model FG_HOLL (without any internal solid mesh).
- In Figure 8, why is the temperature distribution on the upper surface of FG_HOL facing the fire source significantly different from other surfaces? There are no displays of temperature distributions in the interior containing fiberglass insulation filler.
ANSWER – In Figure 8 all temperature field images were displayed in the same range of maximum and minimum values of temperatures, to give the real proportion of color changes. This means, that for the FG_HOLL model and for time resistance of 223 min the temperature field distribution in the model is lower than the others. In this model, the incorporated temperature curve FG_HOLL was introduced to be considered in the boundary conditions of the cavities, where this curve previously was combined with the fiberglass insulation effect.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe article has been revised according to the review comments, and there are no further comments.
Comments on the Quality of English LanguageThe quality of the English expression is moderate.
Author Response
The article has been revised according to the review comments, and there are no further comments. The quality of the English expression is moderate.
ANSWER – The authors appreciate the time and effort of the reviewer in all provided constructive comments that have helped us revise the paper, making it more readable and useful to the community. Thank you for your decision.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe recommendation set previously by the reviewer has been applied. No further actions are recommended.
Author Response
Comments and Suggestions for Authors
The recommendation set previously by the reviewer has been applied. No further actions are recommended.
ANSWER - The authors appreciate the time and effort of the reviewer in all provided constructive comments that have helped us revise the paper, making it more readable and useful to the community. Thank you for your decision.
Reviewer 4 Report
Comments and Suggestions for AuthorsIn Figure 8, why is the temperature distribution on the upper surface of FG_HOL significantly different from the same upper surface of FG_HOL_TS and FG_HOL_ST ?
Author Response
In Figure 8, why is the temperature distribution on the upper surface of FG_HOL significantly different from the same upper surface of FG_HOL_TS and FG_HOL_ST ?
ANSWER – The authors thank the reviewer for the time spent in the review process. In the article, the text identified in green answer to this question.
In Figure 8 all temperature field images were displayed in the same range of maximum and minimum values of temperatures, to give the real proportion of color changes. This means, that for the FG_HOLL model and for time resistance of 223 min the temperature field distribution in the model is lower than the others. In models, FG_HOL_ST and FG_HOL_TS the screws have the effect of producing and spreading heat neighboring to the constructive model, which represents lesser calculated time fire resistance and reaching higher temperatures, even in the upper surface. The behavior is similar when compared with models HOLL HOL_ST and HOL_TS, obviously for different time fire resistances, because of the internal boundary conditions in the cavities.
