Nonlinear Thermo-Structural Analysis of Lightweight Concrete and Steel Decking Composite Slabs under Fire Conditions: Numerical and Experimental Comparison

Round 1

Reviewer 1 Report

This paper analyzes thermo-structural behavior of LWC composite slabs with trapezoidal steel decking subjected to fire and a constant load. Numerical models were developed to predict the thermal and structural performance of the research LWC composite slabs in terms of temperature and time-displacement.

This manuscript presented FE simulated results and experimental results on the thermo-structural behavior, but, there are changes that must be brought to the manuscript, and it is not suitable for publication in its current state.

 The following aspects must be improved and revised:

1.      The state of the art is extensive, the authors analyzed 41 works. However, the papers below are not analyzed. The papers have the same research theme. The last paper contains very interesting results for the studied field.

·        Piloto PA, Balsa C, Santos LM, Kimura ÉF. Effect of the load level on the resistance of composite slabs with steel decking under fire conditions. Journal of Fire Sciences. 2020;38(2):212-231. doi:10.1177/0734904119892210

·        Piloto, P.A.G., Balsa, C., Macêdo Gomes, F.M. and Matias, B. (2021), "Fire resistance of composite slabs with steel deck under natural fire", Journal of Structural Fire Engineering, Vol. 12 No. 4, pp. 522-540. https://doi.org/10.1108/JSFE-02-2021-0009

·        Filho, M.M.A.; Piloto, P.A.G.; Balsa, C. Thermal Behaviour of Rebars and Steel Deck Components of Composite Slabs under Natural Fire. J. Compos. Sci. 2022, 6, 232. https://doi.org/10.3390/jcs6080232

Please analyse and differentiate the research from those published in the work:

Filho, M.M.A.; Piloto, P.A.G.; Balsa, C. Thermal Behaviour of Rebars and Steel Deck Components of Composite Slabs under Natural Fire. J. Compos. Sci. 2022, 6, 232. https://doi.org/10.3390/jcs6080232

2.      The differences in temperature in the steel decking between zones C and D are negligible, but temperatures in zone E are higher than those measured in zone F. A much stronger discussion and analysis are warranted. The experimental results should be correlated with the theoretical relations related to heat transfer. The results of this study do not compare the performance of LWC composite slabs with the NC composite.

3.      The images of the mesh must be presented. Is the mesh size uniform of 5 cm? Is the mesh size differentiated by area? or is it global? How many nodes does the model have in total?

4.      The efficiency of the numerical model is very important. Computational times for the simulation must be specified. Computational time is related to the mesh and the computing power of the machine. The characteristics of the machine must be specified.

5.      How were the values of the thermal contact conductance coefficient Kcc determined depending on the temperature, values presented in table 3?

6.      How was the emissivity constant established? 0.7 is recommended in EUROCODE 4, and 0.78 was used in the paper [14].

7.      The numerical results presented in figures 12 and 13 are not analyzed. A much stronger discussion and analysis are warranted.

8.      Comparing the errors of numerical against experimental results is of paramount importance in order to assess the performance of the numerical model. The percentages of error (%) between experimental and numerical analyses are presented in table 4. The authors affirm that the difference between the experimental and numerical values, in each of the simulations, is less than 15%, but in table 4 there are differences of 62.48%.

9.      The conclusions briefly present new research directions. A much stronger discussion and analysis is warranted. At the same time, it would be useful to present in the conclusions section how the numerical model will be used in future research.

10.   Variable symbols that describe the heat transfer and others should be moved to Nomenclature. It is enough to list them on paper, without specifying the symbol and the units of measurement.

11.   Figure 2c is not clear. A new capture is required. The text is not readable. The authors are talking about table 5, but it does not exist (row 509).

 

In view of the above, I cannot recommend acceptance now. While I am unable to recommend publication at this time, I suggest that the paper be major revision.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The issues discussed in the paper are valid for analysis of the behavior of lightweight concrete and steel deck composite slabs under fire conditions. There is a sufficient number of references (41). The article is well written, however I have demands on authors for improvements of this paper. I explain my suggestion and comments in more detail below:

Remark 1.  Indicate detailed composition of concrete mixes that have been used in the tests.

Remark 2.  Chapter 2 should include the number of specimens tested in each series.

Remark 3.  Why the composite slabs were tested with 640 days of age? Please explain it in the text.

Remark 4.  Indicate the static scheme and boundary conditions of the slabs. This remark applies to both experimental and numerical analysis.

Remark 5.   To what range of the analysis does Table 5 refer? Please, complete the caption of the table.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear authors,

Thank you for the answers.

At this point, I consider that you have completed the manuscript taking into account my observations. I didn't understand why you didn't include fig. 3 of the cover letter in the original manuscript

The manuscript is well written and organized. In conclusion, I appreciate the work done and recommend the publication of the paper in Applied Sciences.