Uplift Behaviour of External Fibre-Reinforced Polymer Wrapping on RC Piles in Dry and Submerged Sandy Soil
Round 1
Reviewer 1 Report
See reviewer's comment attached.
Comments for author File: 
Comments.docx
Author Response
The authors thank the reviewer for the kind comments to improve the manuscript. The comments of the reviewer along with the response by the authors are provided below.
This paper deals with the uplift load carrying capacity or resistance of piles wrapped with Basalt fiber-reinforced polymer (BFRP) and Glass fiber-reinforced polymer (GFRP) sheets through experiments. Experiments focus on the effects of BFRP and GFRP wraps on the mechanical strength properties of concrete piles embedded in dry and submerged soils.
This experimental study mentioned above is well written. Also, the two results between the experiment and the finite element (FE) software Plaxis agree very well with each other. This manuscript is accepted for publication after minor revisions.
240 line: ‘where’ is required to outdent.
Response: Corrected as per the reviewer's advice.
242 line: 2.1 kg/cm2 21 N/cm2 kg may be , i.e. and SI units are required.)
as per per unit width
Response: Corrected to 21 N/cm2
Table 1 of [35]: In Table 1, there is no co-efficient of subgrade reaction.
Response: The content represents Table 1 mentioned in Indian Standard code IS2911. It is corrected to “Table 1 of IS2911 (Part 1) [40]”.
Reviewer 2 Report
The work presented is interesting and adequately presents the results and conclusions.
It seems to me that it is of current interest in the field of the study of composite materials.
Author Response
The authors would like to thank the reviewer for the compliments on our work. Thank you for your support.
Reviewer 3 Report
The paper investigated the uplift load carrying capacity or resistance of piles wrapped with Basalt fibre reinforced polymer (BFRP) and Glass fibre reinforced polymer (GFRP) sheets by experiments and simulation. The results are important to promote the application of RC piles strengthened by FRPs. However, some expression or writing should be further improved by considering the following comments.
1. The part of the abstract should present on more research results. In addition, the uplift resistance mechanism of the piles structures after the wrapping should be analyzed. In addition, the failure mode of concrete pile is also important information.
2. In the introduction part, the introduction of basic information on FRPs should be further clarified based on the fiber type. For example, CFRP has higher mechanical properties, excellent corrosion resistance, fatigue resistance and creep resistance, especially in chemicals and corrosive environments and loading. In contrast, the Si-O skeletons of BFRP and GFRP may react with the alkaline solution of concrete, resulting in long-term performance degradation. Therefore, different FRPs may be used according to different needs, such as cost-performance, service environment, bearing capacity. To clear this information, the authors are encouraged to consider the above comments to make necessary supplements by reviewing the following research. Composite Structures, 2022, 293, 115719. Construction and Building Materials, 2023, 363: 129845. Engineering Structures, 2023, 274: 115176.
3. The research on the uplift resistance or ultimate uplift capacity of piles strengthened by FRPs should be enriched, such as uplift mechanism, failure mode, bearing capacity, stress distribution, etc.
4. The basic properties of FRP plates are given in Table 2. It can be found that the tensile properties have a large change range, and the specific tensile properties parameters of the plates should be specified in the present paper. This is because these values have a significant impact on the performance of the strengthened RC pile.
5. The clarity of the picture 2-4, 6 should be further improved. Please also check other pictures. In addition, picture 7 should be further specialized with same size.
6. The contents expressed in Table 5 and Figure 8-10 are repetitive, and corresponding adjustments are recommended.
7. Please provide relevant analysis and summary on the enhancement mechanisms for different properties, as shown in Table 5. In addition, the failure mode of the sample should be further provided.
8. Please provide the simulation process in the method section. At the same time, please provide the agreement degree between the finite element simulation and the experimental results.
Author Response
The authors thank the reviewers for their kind comments. The authors have incorporated the necessary corrections as per the comments/suggestions given by the reviewer and the authors feel that the paper has undergone significant improvement because of the comments provided by the reviewer.
The paper investigated the uplift load carrying capacity or resistance of piles wrapped with Basalt fibre reinforced polymer (BFRP) and Glass fibre reinforced polymer (GFRP) sheets by experiments and simulation. The results are important to promote the application of RC piles strengthened by FRPs. However, some expression or writing should be further improved by considering the following comments.
- The part of the abstract should present on more research results. In addition, the uplift resistance mechanism of the piles structures after the wrapping should be analyzed. In addition, the failure mode of concrete pile is also important information.
Response: The authors thanks the reviewer for pointing out this mistake. The abstract is included with additional information of the major research results. The discussion on the mechanism behind the uplift behavior of piles after fibre wrapping is included.
- In the introduction part, the introduction of basic information on FRPs should be further clarified based on the fiber type. For example, CFRP has higher mechanical properties, excellent corrosion resistance, fatigue resistance and creep resistance, especially in chemicals and corrosive environments and loading. In contrast, the Si-O skeletons of BFRP and GFRP may react with the alkaline solution of concrete, resulting in long-term performance degradation. Therefore, different FRPs may be used according to different needs, such as cost-performance, service environment, bearing capacity. To clear this information, the authors are encouraged to consider the above comments to make necessary supplements by reviewing the following research. Composite Structures, 2022, 293, 115719. Construction and Building Materials, 2023, 363: 129845. Engineering Structures, 2023, 274: 115176.
Response: The author thanks the reviewer for encouraging the inclusion of the above information in the introduction section. The authors have successfully incorporated the above corrections with the references for literature support.
- The research on the uplift resistance or ultimate uplift capacity of piles strengthened by FRPs should be enriched, such as uplift mechanism, failure mode, bearing capacity, stress distribution, etc.
Response: Based on the comment of the reviewer, the uplift behavior of the piles strengthened by FRP is discussed based on the failure envelope obtained for the unconfined and FRP-confined piles. The failure envelope is presented in Figure 17 and the uplift mechanism along with the diameter of the wedge and the wedge angle are discussed in Section 3.3. Moreover, the interfacial friction behavior of the FRPs with dry and wet soil is provided in Section 3.2.
- The basic properties of FRP plates are given in Table 2. It can be found that the tensile properties have a large change range, and the specific tensile properties parameters of the plates should be specified in the present paper. This is because these values have a significant impact on the performance of the strengthened RC pile.
Response: The author thanks the reviewer for this comment. The range of specific values pertaining to the tensile strength and elastic modulus are changed to the specific values of the used FRPs.
- The clarity of the picture 2-4, 6 should be further improved. Please also check other pictures. In addition, picture 7 should be further specialized with same size.
Response: The clarity of the mentioned figures is improved by changing the monochromatic images to colored images and by increasing their dpi. The size of the pictures in Figure 7 is made identical as per the advice of the reviewer.
- The contents expressed in Table 5 and Figure 8-10 are repetitive, and corresponding adjustments are recommended.
Response: Table 5 presents the mechanical properties with their percentage increase with respect to the unconfined specimen. Whereas, Figure 8-10 provides a pictorial representation of the respective mechanical properties with the variation between the sample in the form of Error bars. It is to note that the tests were conducted on three samples for each mix and the average values are reported.
- Please provide relevant analysis and summary on the enhancement mechanisms for different properties, as shown in Table 5. In addition, the failure mode of the sample should be further provided.
Response: The analysis and discussion on the mechanical properties of the specimen with wrappings are provided in section 3.1. Also, the failure mechanism of the samples is explained in detail in section 3.1 as suggested by the reviewer.
- Please provide the simulation process in the method section. At the same time, please provide the agreement degree between the finite element simulation and the experimental results.
Response: Thank you for pointing out this error. The degree of agreement between the finite element simulation and experimental results is provided in Table 7 in the form of Pexp/Pfea.
Reviewer 4 Report
This study is aimed at determining the uplift load carrying capacity or resistance 13 of piles wrapped with Basalt fibre reinforced polymer (BFRP) and Glass fibre reinforced polymer 14 (GFRP) sheets by experiments.
Some following comments should be considered when revised.
1. Only showed the flow chart in Figure 4? Some photos and details in process are needed.
2. Detailed and in-depth analysis of test results are needed.
3. What the model simulation for？Only for comparison of uplift capacity? Other influence factor analysis are needed.
Author Response
The authors thank the reviewer for their kind comments. The authors have incorporated the necessary corrections as per the comments/suggestions given by the reviewer and the authors feel that the paper has undergone significant improvement because of the comments provided by the reviewer. The comments of the reviewer along with the response by the authors are provided below.
This study is aimed at determining the uplift load carrying capacity or resistance 13 of piles wrapped with Basalt fibre reinforced polymer (BFRP) and Glass fibre reinforced polymer 14 (GFRP) sheets by experiments.
Some following comments should be considered when revised.
- Only showed the flow chart in Figure 4? Some photos and details in process are needed.
Response: Figure 4 shows the flow chart pertaining to the casting and testing of the FRP-wrapped piles. The pictures of the casted piles and the test setup can be seen in Figure 7 which provides a sequence of the major processes carried out.
- Detailed and in-depth analysis of test results are needed.
Response: The author thanks the reviewer for this comment to make a detailed analysis. As suggested by the reviewer, Section 3 is included with a detailed discussion of the test results. The failure of the specimen subjected to mechanical strength tests is included. Further, the failure envelope of the piles is also discussed along with the inclusion of Figure 17 which gives the failure envelope during uplift. Also, the comparison of the experimental test results and the finite element analysis are included in Table 7 and are discussed in Section 3.4 for understanding the agreement of the results.
- What the model simulation for？Only for comparison of uplift capacity? Other influence factor analysis are needed.
Response: In the scope of the current paper, model simulation is carried out only to investigate the limited parameters considered in the work. However, the other parameters are to be used for validating future experiments and to propose a detailed parameter validation which is outside the scope of the present work.
Round 2
Reviewer 3 Report
Accepted.
Author Response
The authors thank the reviewer for recognizing our work and accepting our manuscript.
Reviewer 4 Report
Some specific comments are as follows,
1. During the test, all the piles are located in the same geotechnical box. After the test of one pile, will the disturbance of soil around the pile have an impact on the other piles?
2. In 2.1.1 Material properties, the material properties of cement and fine aggregate may be listed in tables.
3. In figure 4. casting and testing of FRP wrapped piles. Some pictures during the process should be provided.
Author Response
The authors thank the reviewer for the kind comments to improvise the manuscript. As per the comments of the reviewer, we have made improvements to the manuscript.
Some specific comments are as follows,
- During the test, all the piles are located in the same geotechnical box. After the test of one pile, will the disturbance of soil around the pile have an impact on the other piles?
Response: The authors thank the reviewer for asking this interesting question. In this study, the piles were kept in the test tank at a spacing of not less than 3 times the diameter of the pile as per section 6.6.2 of Indian Standard code IS 2911. The piles were placed in sandy soil with the aid of adequate compaction. During the test, the piles were pulled out gradually and not abruptly. Owing to this, the soil did not reorient considerably and does not change its density. This was confirmed by us during the course of the experiment using the field density test done after conducting tests on each pile.
- In 2.1.1 Material properties, the material properties of cement and fine aggregate may be listed in tables.
Response: The authors thank the reviewer for pointing out this error. Table 1 (cement properties) and Table 2 (Properties of aggregates) are included as per the reviewer suggestion.
- In figure 4. casting and testing of FRP wrapped piles. Some pictures during the process should be provided.
Response: The authors thank the reviewer for the comment. Figure 5 is provided with casting pictures namely a) Placement of reinforcement and concreting; b) Curing with wet gunny bags; c) FRP Wrapping d) Coating of Epoxy above FRP and Figure 7 is provided with pictures of test setup namely (a) Welding of reinforcement; (b) Installation of reaction girder; (c) Installation of dial gauges; (d) Final Setup in dry state (e) Final setup in submerged state.
Round 3
Reviewer 4 Report
It can be accepted in present form.
