Experimental and Analytical Investigations on Glass-FRP Shear Transfer Reinforcement for Composite Concrete Construction

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review this interesting manuscript investigating the use of GFRP as shear transfer reinforcement. The experimental program is generally well-conceived. However, several points require clarification and correction before the manuscript can be considered for publication.

 

1. Abstract: The abstract is currently too detailed, including excessive background information. It should be concise, focusing on the study's objectives, primary methodology, key findings, and the proposed model. Background context is more appropriate for the introduction.
2. Experimental Simulation Validity (Figure 3): The interface formation process, where the second L-block is cast after only 3 days of moist curing of the first block, raises a question regarding its representativeness of real-world conditions. In practice, precast girders typically require higher strength for demolding and handling, often achieved through steam curing, resulting in a fully hardened state before the cast-in-place slab is added. Casting the second block after only 3 days, while the first block's concrete is still undergoing early-stage hydration, might create an interface with co-hydration across the joint. This could differ significantly from the "cold joint" interface between fully hardened and fresh concrete encountered in actual composite construction. Please justify this methodological choice or discuss its potential implications.
3. Axial Stiffness Increase in Group A2 (Section 2.2): The manuscript states that reducing the interface area in Group A2 led to a 33.3% increase in axial stiffness (E_f * ρ_v) for the same transverse reinforcement ratio. This is conceptually unclear. Since the axial stiffness parameter is defined as the product of the elastic modulus (E_f) and the reinforcement ratio (ρ_v = As / Ac), and both E_f and ρ_v would remain constant, the axial stiffness should not change. Please clarify how the reinforcement ratio was calculated and defined in this context, as this point is currently confusing and seems to contradict the given definition.
4. Missing Post-Peak Behavior (Figure 11): For specimens with sufficient axial stiffness, such as FS3-50 in Figure 11, the load-slip curve appears to lack a distinct post-peak branch. This is unexpected, as one of the highlighted advantages of adequately reinforced GFRP interfaces is their ductile post-ultimate behavior. Please explain the reason for the apparent sudden failure of this specimen. Was the test stopped prematurely, or is there another explanation?
5. Figure 1: The label "Figure 1(b)" is missing from the figure.
6. Section Numbering and Headings: The organizational structure needs adjustment. Sections like "2.2. Effect of the Reinforcement Stiffness Parameter" and "2.3. Effect of the Reinforcement Type," which present and discuss results, should logically fall under a main "Results and Discussion" section (e.g., Section 3), with subsequent sections renumbered accordingly.
7. Cylinder Specimen Dimensions (Line 243): The dimension "102 × 203 mm" is ambiguous. Please specify whether this refers to "Diameter × Height" – the standard notation for concrete cylinders.
8. Stiffness Threshold in Conclusions: The value for the minimum required GFRP stiffness parameter is inconsistently reported as both "200 N/mm²" and "203 N/mm²" in the conclusions. Please standardize this value throughout the manuscript.

 

I believe addressing these points, particularly the major comments regarding the experimental simulation and the definition of axial stiffness, will significantly strengthen the manuscript.

Author Response

Please see the attachment

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is well-written and thoughtful; its only flaw is the limited interest. It refers to ASTM standards, which aren't a global standard, but rather only for the Anglo-Saxon world. Perhaps in the future, the audience of those who might draw inspiration from it could be expanded. The title should be more consistent with the research and experimental part, so that it's immediately clear that concrete with GFRP bars is being studied, also specifying, if possible, why glass fibers (weak acid) can be used in concrete (strong alkaline) without chemically reacting and therefore degrading fibers. Figure 1 doesn't have a complete label; it appears to be taken from a textbook and also contains an error: zirder instead of girder. Figure 6 is too didactic: the research paper isn't a textbook from which to learn theory.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf