Analysis of Measured Temperature Field of Unpaved Steel Box Girder

Round 1

Reviewer 1 Report

General Comment

The manuscript presents an experimental study on the temperature field due to sunshine of a unpaved steel box girder which constitutes the rail beam of a small straddle-type monorail transportation train for tourism located in Pingyao, province of Shanxi, in China. For this, a segment of the steel box girder is considered as the test specimen and located abroad under natural meteorological conditions. The temperature values were recorded daily through sensors located at several points of the outer perimeter of the steel specimen during more than 1 year. Based on the long-term recorded data, the temperature change behavior of the test specimen is presented and discussed. Then, based on a GEV distribution and numerical results using FEM, representative values of the temperature for different return periods, as well as a temperature gradient model, are proposed for design.

The topic of the manuscript is very interesting since temperature gradient is a very important loading to be considered for the design of steel box girders beams. The results from the presented study, as well as the presented methodology, could be useful for practice and also for future code’s revisions.

I made some comments in order to improve the manuscript. The authors should take the comments into account and revise their manuscript.

Specific Comment 1

Please carefully revise the entire manuscript to improve the reading. Several sentences need to be rewritten for better understanding. This includes the verbal tense. The authors should seek for professional help to improve the article.

Specific Comment 2

Some formatting issues need to be corrected. Please refer to the mdpi instructions for authors. Some examples:

- Reference number between brackets should appear right after the name of the cited authors;

- A new section should no start with a figure;

- Figures must appear only after they are referred in the text;

- …

Specific Comment 3

Section 1, line 31-32

Instead of “… affecting the structural damage, …” it would be better ““… affecting the structural design and damage, …”.

Specific Comment 4

Section 1

The literature review on the topic is somewhat poor and must be improved. The number of related references must also be updated.

Specific Comment 5

Section 2

This section is very poor and must be improved. For instance:

- Describe the location, as well as the geographical environment and meteorological conditions, of the site where the measurements were made;

- Justify the small the length of the test specimen with respect to its height and how the temperature in the surface of the top sections influences the measured data at the central section;

- Provide the steel/section properties with interest for this study;

- Provide information about the orientation of the test specimen with respect to the daily sun position;

- …

Specific Comment 6

Section 3

In the article, please add a physical explanation on why the temperature in the steel specimen is usually higher that the environmental temperature.

Specific Comment 7

Section 3, Figure 3

Please indicate in the text which days the results in the graphs refer to (unless they represent average values for some time period, which must be referred in the text).

Specific Comment 8

Figures 8 and 9

These figures have the same caption. Please correct this.

Specific Comment 9

Tables 3 and 4

Please add units for the temperature.

Specific Comment 10

Section 4.4

Please add more information about the FE model, namely: used software, used FE families, mesh sensitivity analysis, mesh density, boundary conditions, properties of steel, applied loadings (temperature field), …

Also, please provide some graphical results from the FE model.

Specific Comment 11

Section 5

A sentence is missing before the point-by-point conclusions.

Author Response

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Reviewer 2 Report

The research topic is quite interesting and overall the manuscript has good quality. The manuscript is well organized and written. However, there are some aspects that can be improved, hence at this stage the reviewer recommends "Major Revision". The reviewer would like the authors to consider the following points:

1. The motivation for this study must be improved, presenting more information concerning the impacts of such temperature gradients in the structural design of such structures.

2. Some preliminary discussion should be provided in terms of the possible thermal stresses, thermal elongation of steel and how it can affect the structural performance of steel girders.

3. Did the authors considered possible global-warming impacts due to climate change? How can existing climate models impact the temperature for the different return periods of 50 and 100 years.

4. Chapter 2 is starting with Figures and it does not seem appropriate. A sentence must be used in the beginning of the chapter.

5. Explanations and details about the finite element modelling are quite poor. The used techniques, the assumptions and even the thermal properties are not presented. Also, no calibration of the numerical model is presented, hence the relevance of the information in Chapter 4.4. is difficult to understand.

6. Line 299 - some problem with spacing.

7. No discussion about the impacts of the monitored thermal gradients is presented, for instance in terms of structural performance.

Author Response

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Reviewer 3 Report

Reviewer:

The authors studied the temperature change law of the steel rail beams and the distribution characteristics of the sunshine temperature field in the straddle-type monorail tourist transportation system employing field test and numerical simulation based on measured data during the whole test period. Overall, it does not contain sufficiently novel material for a publication in this journal.

1.There is not too much novelty in this investigation, similar studies on analysis of sunshine temperature field of steel box girder have been done by researchers in [1,2]. To name but a few.

[1]. Lu, Hailin, et al. "Analysis of sunshine temperature field of steel box girder based on monitoring data." Advances in Civil Engineering 2020 (2020).

[2]. Ding, Youliang, et al. "Thermal field characteristic analysis of steel box girder based on long-term measurement data." International Journal of Steel Structures 12.2 (2012): 219-232.

Therefore, I would not recommend the manuscript for publication.

Author Response

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Round 2

Reviewer 1 Report

I received and read the revised version of the manuscript with title “Analysis of Measured Temperature Field of Unpaved Steel Box Girder”. I´m very satisfied with the authors’ replies to my comments and I consider that all the recommendations were considered to highly improve the manuscript. I consider that the revised manuscript submitted by the authors can be accepted to be published.

Reviewer 3 Report

The authors have modified their manuscript following all suggestions made by the reviewer. The reviewer support the publication of the manuscript.