Experimental and Numerical Study of Adhesively and Bolted Connections of Pultruded GFRP I-Shape Profiles

Round 1

Reviewer 1 Report

Thank you for submitting your paper. The work done here draws attention to a significant subject in assembly of composites. I have found the paper to be interesting. However, several issues need to be addressed properly before the paper is being considered for publication. My comments including major and minor concerns are given below:

1. Please consider reviewing the abstract and highlight the novelty, major findings, and conclusions. I suggest reorganizing the abstract, highlighting the novelties introduced. The abstract should contain answers to the following questions:
2. What problem was studied and why is it important?
3. What methods were used?
4. What conclusions can be drawn from the results? (Please provide specific results and not generic ones).
5. The abstract must be improved. It does not read well at all. Please use numbers or % terms to clearly shows us the results in your experimental work. Please expand the abstract.
6. Please consider reporting on studies related to your work from mdpi journals.
7. The introduction must be expanded, please consider improving the introduction, provide more in-depth critical review about past studies similar to your work, mention what they did and what were their main findings then highlight how does your current study brings new difference to the field.
8.  
9. The title of the article should be improved.
10. Experimental program change to Materials and Methods.
11. Figure 1 the authors say it is an FRP then in the title it says GFRP, which one is it, please be consistent and specific in your wording across the article.
12. “It was expected that bolted connection had more deformability but better durability in high moisture environment respect to adhesive connection” why? This is a claim not followed by an reasonable justification or scientific facts to support it?
13. Table 3 did the authors measure these values or were they taken from other sources? If yes, then please reference the table as necessary.
14. Figure 2 add some arrows and text to show the readers what they are looking at in this image, also consider adding a scale bar.
15. Tables 6 and 7 need references?
16. Finite element modelling something is missing here, did the authors use a user defined subroutine? You claim to use solid elements and 3D dimensional model. What was the subroutine model criteria based on?
17. FE model needs more work, boundary conditions, number of elements, mesh convergence study and model limitations/improvements compared to previous models reported in the open literature.
18. What is S23 exactly in figure 7? You must specify the direction of stress? You are only showing one of them but there are others in S12 and S13?
19. Figure 7 what is the unit of shear stress? Is it MPa or not, because if not in the model it looks like the part fails at a very low load!
20. The results are merely described and is limited to comparing the experimental observation and describing results. The authors are encouraged to include a more detailed results and discussion section and critically discuss the observations from this investigation with existing literature.
21. Conclusion can be expanded or perhaps consider using bullet points (1-2 bullet points) from each of the subsections.
22. What is the point of the FE model? it is not clear the link between it and between the experimental tests, just showing that you can model the tests is not something novel of siginificant in my opinion. please elaborate furthe about this point. 

Author Response

Please check the attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

Please describe the main steps that you followed and the main outstanding outcomes in the abstract.

Please further elaborate on the novelty of your work in abstract.

Please include a brief but critical review regarding the conducted research studies in the introduction.  It is recommended to add a section “research significance” and highlight the main contribution of your findings.

Please include the latest research studies related to your work preferably between 2019 and 2022.

Please include a brief summary of using noble grooving methods such as EBR and EBROG on improving the performance of structures using GFRP materials. Accordingly, please include the article titled “Effect of EBR-and EBROG-GFRP laminate on the structural performance of corroded reinforced concrete columns subjected to a hysteresis load”

Please analyze the bond response between the concrete and rebar against corrosion using the article titled “Probabilistic model for rebar-concrete bond failure mode prediction considering corrosion”

Please include a review on applications of the recycled material and GFRP on improving the structural resistance of structures using the article titled “Effect of fiber reinforced polymer tubes filled with recycled materials and concrete on the structural capacity of pile foundations”

Please include a subsection in the introduction as “research significance” and discuss the novelty and main contribution of your work.

Please reason on using the CFRP as flange connectors instead of GFRP material.

Please further elaborate on the numerical simulation by ABAQUS. Verify the reported experimental outcomes against the performed simulation.

State the boundary conditions and main assumptions on performing the simulation.

Please state the outcomes in a quantitative manner.  For example, please revise the following statement “was that the load-bearing capacity of adhesively connections was far lower than for bolted ones” How much lower?

Please mention the definition of the “best economic mechanical balance” in the statement “The best economic-mechan-ical balanced performance was achieved with web bolted connectors.”

Please include statistical characteristics such as standard deviation and R square on the presented graphs.

Please add a discussion and elaborate on the main parameters that can considerably affect the reported outcomes.

Please revise the conclusion and present a quantitative approach on reporting the outcomes.

Author Response

Please check the attached file

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors provided the answers to the comments from the first round of review and made sufficient changes in the manuscript according to these comments. I recommend this manuscript for a publication in its present form.

Reviewer 2 Report

The authors have addressed the raised concerns well.