Long-Term Behavior of RC Beams Strengthened with Hybrid Composite Beam

Round 1

Reviewer 1 Report

Please find attached a PDF file with my comments and suggestions for authors.

Comments for author File: Comments.pdf

Author Response

Thanks for your valuable advices for higher quality paper.

please see the responses.

Thanks

<Reviewer 1>

Comments and Suggestions for Authors

This manuscript includes an interesting research about the long‐term behavior of RC beams strengthened with hybrid composite beam. In my opinion, the topic is very interesting, and the manuscript is complete and very well‐done.

Nevertheless, I have some suggestions in order to improve the manuscript before being published in Applied Sciences Journal.

The introduction section is fine, although I suggest to clarify the aim and the novelty of the study improving the text of the paragraph in lines 88‐94.

-      We added more detailed aim or why we did for this work at the Introduction-

I congratulate the authors for the good experimental program section. The different drawings and photos included in that section are very good and detailed. They are very useful for clarifying the research performed.

-      We changed Fig.  2 by adding HCB section under RC beam. -

Regarding the results and discussion section, I think that it is generally adequate, but I suggest to discuss the results with more depth and detail, because the majority of abovementioned section is used for describing the results, and the discussion of each one is relatively short. I also suggest to include more references in the discussion of results. The conclusion section is also fine. I like the idea of using bullet points or numbers for emphasizing the most important findings of the manuscript, because it makes the conclusions clearer.

-       We added more related references and mentioned in the text- -

Regarding the references, please include more references for supporting the discussion of the results.

Finally, I want to encourage the authors for continuing working in this interesting topic, and I think that the manuscript can be accepted for publication in Applied Sciences Journal, after including the proposed minor changes.

-      We revised summary part in each section and conclusions- -

Reviewer 2 Report

1.       Figs. 1 and 2 need clarification: In figure 1, the external reinforcing has a different geometry and shape than the one used in Fig. 2 for the RC beam. The section in Fig. 2 should be revised to show the external reinforcement at the bottom of the section,

2.       It is misleading to call the external reinforcement a ‘beam’. It should be called external FRP reinforcement or strengthening FRP reinforcement.

3.       The authors mentioned they used power pins. There is no sketch of figure that shows where these pins where applied. Also what was the purpose of these power pins.

4.       Did the authors record humidity levels for the long term tests? Can the authors’ comments on that and the effect of humidity on the performance of the strengthened beams?

5.       Can the authors comment on how the area of the external reinforcement was determined?

6.       Did the authors run tests with different areas of FRP? different types of FRP? This would improve the study.

7.       I understand the authors did not do fatigue testing, but I believe FRP external reinforcement need to be evaluated for fatigue loads. Although RC beams in buildings may not experience fatigue loads compared to bridges or industrial buildings, but moving live load in schools (hallways and classrooms) may produce fatigue loads and that can affect the bonding on the FRP to the concrete beams. Can the authors comment on that?

8.       Can the authors comment on the long term deflections and main reasons for the long term deflection and the effects of the FRP on the long term deflections? I was surprised not seeing  ‘control beam(s)’ in this study so that comparisons can be made with the externally reinforced beams?

9.       Conclusion (3) should only be restricted to the tested beams and can’t be generalized to include other parameters that were not evaluated in this study.

Author Response

<Reviewer 2>

Thanks for your valuable advices,

1. Figs. 1 and 2 need clarification: In figure 1, the external reinforcing has a different geometry and shape than the one used in Fig. 2 for the RC beam. The section in Fig. 2 should be revised to show the external reinforcement at the bottom of the section,

We changed Fig.  2 by adding HCB section under RC beam. -

 2. It is misleading to call the external reinforcement a ‘beam’. It should be called external FRP reinforcement or strengthening FRP reinforcement.

- We unified the term as external strengthening in this paper except mentioned in other researchers -

3. The authors mentioned they used power pins. There is no sketch of figure that shows where these pins where applied. Also what was the purpose of these power pins.

-To improve the bond between the hybrid composite beam and concrete in this study, commercially available power pins were used in the lips of hybrid composite beams- in lines of 121-124.

4. Did the authors record humidity levels for the long term tests? Can the authors’ comments on that and the effect of humidity on the performance of the strengthened beams?

- This experiment done in outside under big tent through almost 1 year, actually we did not check the humidity inside the tent.

5. Can the authors comment on how the area of the external reinforcement was determined?

 - The length of HCB strengthening was 5,400mm and 260mm of width of HCB, we did external strengthening under the RC beam width of 400mm-

6. Did the authors run tests with different areas of FRP? different types of FRP? This would improve the study.

- No, we did not, because company only produced this type-

7. I understand the authors did not do fatigue testing, but I believe FRP external reinforcement need to be evaluated for fatigue loads. Although RC beams in buildings may not experience fatigue loads compared to bridges or industrial buildings, but moving live load in schools (hallways and classrooms) may produce fatigue loads and that can affect the bonding on the FRP to the concrete beams. Can the authors comment on that?

- it will be tried further test for another thesis-

8. Can the authors comment on the long term deflections and main reasons for the long term deflection and the effects of the FRP on the long term deflections? I was surprised not seeing ‘control beam(s)’ in this study so that comparisons can be made with the externally reinforced beams?

- Under two sustained loads of 33% and 50%, we did un-strengthened RC beam (this will be considered as control beam) and HCB strengthened RC beam-

 9. Conclusion (3) should only be restricted to the tested beams and can’t be generalized to include other parameters that were not evaluated in this study.

- we revised conclusions based on the results in the present work with other investigations.

10. Please reviews the attached paper !

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have addressed my comments