Effects of Grout Compactness on the Tensile Behavior of Grouted Splice Sleeve Connectors

Round 1

Reviewer 1 Report

The effect of grout compactness on the performance of grouted splice sleeves (GSS) is investigated and an assessment method on tensile bearing capacity of GSS in case of imcompact grouting is proposed.

A better description of the test equipment and instruments would be of importance to improve the overall quality of the paper.

It is necessary to add a table containing all the main results from the experimental campaing, so to improve readability and facilitate the analysis of the obtained results.

It should be clarified how raw data from sensors have been manipulated to obtain results recorded in the tables and shown in the graphs.

By reading Section 2, it is not clear at which the testing plan is aimed. In particular, several graphs are shown, the results of the mesurements are plotted but it is not clear what is the main aim of the experimental activities. Please, modify this section to improve its readability.

It is not clear the correlation between the experimental activity described in Section 2 and the theoretical formula derived in Section 3. It is not clear how such formula can be used to determine whether reinforcing remedies or re-grouting is required. Please, modify section 3 to improve its readability and clarify these points.

 

Minor remarks

It would be of interest to estimate the uncertainty in the degree of compactness of the formed samples.

Please, add the definition of elongation ratio.

Section 2.2: “the loading process was controlled by load …..after the yielding of the spliced rebar”. Is the first part of the test load-controlled and the second part displacement-controlled? Please, clarify.

Figure 3. The image resolution is poor. It should be improved so to properly show what cross sections are instrumented.

Table 3. Stadard deviation is a dimensional parameter. Please, add the unit of measure. Probably, it would be more interesting to show the results in terms of Coefficient of Variation.

End of § 2.3.1 “It is not until….slowly pulled out”. Please, rephrase this sentence to clarify the point.

Author Response

Replies to Reviewer’s Comments (Reviewer 1) on

paper No. applsci-1687225

 

Effects of Grout Compactness on the Tensile Behavior of Grouted Splice Sleeve Connectors

Zhangrong Zhang ¹, Shaofei Jiang^1,*, Wanxia Cai¹, Chunming Zhang²

 

The authors wish to thank the reviewer for their constructive comments. All the comments are addressed in the new revision. Modifications and corrections are marked with special colors. A summary is given below:

 

1. A better description of the test equipment and instruments would be of importance to improve the overall quality of the paper.

Answer: The authors agree with the reviewer’s comments and appreciate to the valuable suggestion. The new manuscript has been revised. More details can be seen in section 2.1 and 2.2.

 

2. It is necessary to add a table containing all the main results from the experimental campaign, so to improve readability and facilitate the analysis of the obtained results.

Answer: The authors really appreciated the reviewers’ constructive suggestions. Relevant revision has been made, as shown in Table 2 and Table 5.

 

3. It should be clarified how raw data from sensors have been manipulated to obtain results recorded in the tables and shown in the graphs.

Answer: The authors agree with the reviewer’s comments and appreciate to the valuable suggestion. The new manuscript has been revised. More details can be seen in Section 2.3.2 and 2.3.3.

 

4. By reading Section 2, it is not clear at which the testing plan is aimed. In particular, several graphs are shown, the results of the measurements are plotted but it is not clear what is the main aim of the experimental activities. Please, modify this section to improve its readability.

Answer: Thanks for the reviewer’s suggestion. The new manuscript has been revised, and the main aim of the graphs has been explain in Section 2. More specifically, the bond-slip failure mode includes the grout-pipe bond slip and the bar-grout bond slip. When the stress of the rebar is small than the strength of the bar-grout bond slip, the failure mode can be considered as the grout-pipe bond slip. To clarify the type of slip without breaking the sleeve, the bond strength was calculated and compared with the stress of rebar. Thus, the stress of the rebar was calculated and shown in Figure 10 and 11.

 

5. It is not clear the correlation between the experimental activity described in Section 2 and the theoretical formula derived in Section 3. It is not clear how such formula can be used to determine whether reinforcing remedies or re-grouting is required. Please, modify section 3 to improve its readability and clarify these points.

Answer: The authors agree with the reviewer’s comments and appreciate to the valuable suggestion. On the basis of Reference [26] and test data such as P_{u, avg} and ε_t,sl from Section 2, the formula for tensile capacity of the grouted splice sleeve was proposed in Section 3. The new manuscript has been revised. More details can be seen in Section 3.

 

Minor remarks

 

1. It would be of interest to estimate the uncertainty in the degree of compactness of the formed samples.

Answer: The authors agree with the reviewer’s comments. To test the uncertainty in the degree of compactness of the formed samples, we proposed a t-distribution-based ultrasonic probability method suitable for the grouted sleeve compactness detection. The word has been done and the relevant paper titled “Ultrasonic testing method of grouting sleeve compactness” has been finished and published in “Journal of Vibration and Shock”.

 

2. Please, add the definition of elongation ratio.

Answer: The authors agree with the reviewer’s comments and appreciate to the valuable suggestion. The definition of elongation ratio has been added in Section2.2.

 

3. Section 2.2: “the loading process was controlled by load …, after the yielding of the spliced rebar”. Is the first part of the test load-controlled and the second part displacement-controlled? Please, clarify.

Answer: The authors agree with the reviewer’s comments. The loading process was divided into two stages. The first stage adopted force loading until the spliced rebar yielded. Subsequently, the second stage adopted displacement control loading. Relevant revision has been made.

 

4. Table 3. Standard deviation is a dimensional parameter. Please, add the unit of measure. Probably, it would be more interesting to show the results in terms of Coefficient of Variation.

Answer: The authors agree with the reviewer’s comments. The unit of measure has been added for standard deviation.

 

5. End of § 2.3.1 “It is not until…, slowly pulled out”. Please, rephrase this sentence to clarify the point.

Answer: The authors really appreciated the reviewers’ constructive suggestions. Relevant revision has been made, as shown in End of § 2.3.1.

 

Author Response File: Author Response.docx

Reviewer 2 Report

1. The test results should be combined with theoretical analysis. For example, the strain values of sleeve and rebar could be referred into the setup course of formula derivation.

 

2. The test data were already used to fit the coefficient in Fig. 15 and then make the Formula(8).  But it is not appropriate to use the original test data again for the verification of these formulas in Table 4.

 

3. The component characteristics of D18-50%, D18-70% and D18-90% in Table 4 did not meet the third assumption of the model in Fig.14, as whichdescribed “The bonding stress of rebar-grout ub is uniformly distributed in the range of the anchorage length of rebar”. Then It is not suitable for the calculation and verification of the formula derived from the model. The author can collect more relevant experimental data to verify the model formula.

Author Response

Thank for the reviewer's comments.we have revised the manuscript according the review reports at this moments.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors presented an interesting and well-written paper. The following minor comments should be incorporated in the revised manuscript

1) explain in more details the specimen preparations and experimental set-up

2) can you develop bond-slip models, if not recommend for a future research study

3) why you did not install strain gauges to measure slip and compute bond experimentally. 

Author Response

Replies to Reviewer’s Comments (Reviewer 2) on

paper No. applsci-1687225

 

Effects of Grout Compactness on the Tensile Behavior of Grouted Splice Sleeve Connectors

Zhangrong Zhang ¹, Shaofei Jiang^1,*, Wanxia Cai¹, Chunming Zhang²

 

The authors wish to thank the reviewer for their constructive comments. All the comments are addressed in the new revision. Modifications and corrections are marked with special colors. A summary is given below:

 

1. Explain in more details the specimen preparations and experimental set-up

Answer: Thanks for the reviewer’s suggestion and the authors give the detailed descriptions in the revision, as shown in Section 2.1 and 2.2.

 

2. Can you develop bond-slip models, if not recommend for a future research study

Answer: The authors agree with the reviewer’s comments and appreciate to the valuable suggestion. Just as the reviewer’s saying, bond-slip models is one of crucial tool to describe the deformation characteristics of grout sleeves. A bond-slip model presented for grout sleeves needs huge of experiments and numerical simulation to validate its efficiency. However, the main purpose of this paper is to study effects of grout compactness on the tensile behavior of grouted splice sleeve, and proposes the formula for tensile capacity of the grouted splice sleeve. The experiments were designed for this purpose. Thus, there were not enough experimental data as the basis to develop bond-slip models.

 

3. Why you did not install strain gauges to measure slip and compute bond experimentally. 

Answer: Thanks for the reviewer’s suggestion. Actually, we set up two LDVT at both side of the grout sleeve to monitor the total vertical deformation and two strain gauges to monitor the deformation of the rebar. When the failure mode is the bond-slip, the slip can be calculated by the difference between the total vertical deformation and the deformation of the rebar.

 

 

Author Response File: Author Response.docx

Reviewer 4 Report

This work reports the effects of grout compactness on the tensile behavior of grouted splice sleeve connectors. The authors designed GSS with different compactness and tested the tensile behaviors of the GSS with different rebars. Later, the authors calculated the tensile capacity based on classic models. Overall, the work has certain significance in the sense of engineering applications, but it has great shortages in writing, data validity, and mechanisms discussion. Specific comments are given below.

1, The English should be improved.

2, The authors said that the grout material os C80, but did not take any test. It is better to provide the mechancial properties of the grout material.

3, In Figure 8, why is the stress-strain curve of D22-100% different from the others? A rapid stress rise can be seen for D22-100%, what is the reason. Is the test repeatable?

4, InFigure 9, D18-70% showed different stress-strain curve from the others, what is the reason?

5, In the present work, almost no profound discussions on the validity of data and findings were performed. This is important for a scientific paper.

Author Response

Replies to Reviewer’s Comments (Reviewer 3) on

paper No. applsci-1687225

 

Effects of Grout Compactness on the Tensile Behavior of Grouted Splice Sleeve Connectors

Zhangrong Zhang ¹, Shaofei Jiang^1,*, Wanxia Cai¹, Chunming Zhang²

 

The authors wish to thank the reviewer for their constructive comments. All the comments are addressed in the new revision. Modifications and corrections are marked with special colors. A summary is given below:

 

1. The English should be improved.

Answer: The authors agree with the reviewer’s comments and appreciate to the valuable suggestion. The new manuscript has been done a double check by a native English scholar before it is submitted.

 

2. The authors said that the grout material is C80, but did not take any test. It is better to provide the mechanical properties of the grout material.

Answer: The authors agree with the reviewer’s comments and appreciate to the valuable suggestion. The mechanical properties of the grout material have been provided in the new manuscript.

 

3. In Figure 8, why is the stress-strain curve of D22-100% different from the others? A rapid stress rise can be seen for D22-100%, what is the reason. Is the test repeatable?

Answer: Thanks for the reviewer’s comments. The early stage of the stress-strain curve of D22-100% showed a larger elastic modulus. The main reason is that the force data acquisition system is different from the strain data acquisition system. In the test, the strain collection of D22-100% was not synchronized with the force collection in time.  Subsequently, this will cause the stress-strain curve of D22-100% different from the others. However, the failure mode of these four specimens was the rebar rupture failure mode. The error of data acquisition in the early stage will not affect the final results.

 

4. In Figure 9, D18-70% showed different stress-strain curve from the others, what is the reason?

Answer: Thanks for the reviewer’s comments. The main reason is that the bond-slip of D18-70% occurred at the both end of the specimen, while the bond-slip of D18-50% just occurred at one end of the specimen. Slip at both ends will significantly decrease the measured stress of the rebar. This causes the D18-70% showed different stress-strain curve from the others.

 

5. In the present work, almost no profound discussions on the validity of data and findings were performed. This is important for a scientific paper.

Answer: Thanks for the reviewer’s suggestion and the authors give the detailed descriptions in the revision, as shown in Section 2.3.

Round 2

Reviewer 1 Report

Authors have modified the submitted paper on basis of reviewer comments; the overall quality of the manuscript is improved.

Author Response

We appreciate for the reviewer’s warm work earnestly. The comments are very helpful for revising and improving our paper. Once again, thank you very much for your comments and suggestions.

Reviewer 2 Report

As the question and answer before mentioned.

3. The component characteristics of D18-50%, D18-70% and D18-90% in Table 4 did not meet the third assumption of the model in Fig.14, as which described “The bonding stress of rebar-grout ub is uniformly distributed in the range of the anchorage length of rebar”. Then It is not suitable for the calculation and verification of the formula derived from the model. The author can collect more relevant experimental data to verify the model formula.

 

Answer: Thanks for the reviewer’s comments. The incompactness will only reduce the volume of grout material, and thus decrease the anchorage length of the rebar. The grout area of the section still remains constant. Thus, the bonding stress of rebar-grout u_b is uniformly distributed in the range of the anchorage length of rebar.

 

But how to explain the "Figure 3. Schematic diagrams of different grout compactness  "  as the words described?

 

 

Author Response

Replies to Reviewer’s Comments on

paper No. applsci-1687225

Effects of Grout Compactness on the Tensile Behavior of Grouted Splice Sleeve Connectors

Zhangrong Zhang ¹, Shaofei Jiang^1,*, Wanxia Cai¹, Chunming Zhang²

The authors wish to thank the reviewers for their constructive comments. We have revised the paper based on the comments from reviewers. In the new revision, modifications and corrections are marked with special colors. A summary is given below:

Point. 1 The component characteristics of D18-50%, D18-70% and D18-90% in Table 4 did not meet the third assumption of the model in Fig.14, as which described “The bonding stress of rebar-grout ub is uniformly distributed in the range of the anchorage length of rebar”. Then It is not suitable for the calculation and verification of the formula derived from the model. The author can collect more relevant experimental data to verify the model formula.

earlier answer: Thanks for the reviewer’s comments. The incompactness will only reduce the volume of grout material, and thus decrease the anchorage length of the rebar. The grout area of the section still remains constant. Thus, the bonding stress of rebar-grout u_b is uniformly distributed in the range of the anchorage length of rebar.

But how to explain the "  Figure 3. Schematic diagrams of different grout compactness "  as the words described?

Answer: We apologize for our thoughtless answers earlier, and appreciate for the reviewer’s warm work earnestly. The incompactness does cause the inhomogeneous distribution of the bond stress u_b of rebar-grout in the range of the anchorage length of rebar. Thus, to solve this problem, the fifth assumption was proposed, which described the derivation is based on a fully compact connector, the derived formula is used in the compact and incompact connectors. And an incompact connector is considered as a compact connector with a lower bearing capacity. However, the fifth assumption will enhance the transversely tensile force of spliced sleeve T_t,sl and then increase u_n, when the grout exists incompactness. From the formulas, we know that u_b is derived by the restraint stress of grout material acting on rebar u_n,b, which is mainly determined by the constraint stress u_n. Thus, u_b is considered as the uniform distribution when the fifth assumption was proposed, and the value of u_b will be overestimate. To fill this gap, the anchorage length of rebar l_b is thought to be reduce by the incompactness. On this basis, the u_b can be calculated by considering the influence of incompactness.

Author Response File: Author Response.docx

Reviewer 4 Report

All my questions have been coarsely addressed. I feel that this manuscript may be acceptable for publication.

Author Response

We appreciate for the reviewer’s warm work earnestly. The comments are very helpful for revising and improving our paper. Once again, thank you very much for your comments and suggestions.

Round 3

Reviewer 2 Report

The author should emphasize the  content  in the manuscripts， and give the details about how to consider the incompactness of grout in connector through the anchorage length of rebar l_b .

Thanks a lot.

 

Author Response

Replies to Reviewer’s Comments on

paper No. applsci-1687225

Effects of Grout Compactness on the Tensile Behavior of Grouted Splice Sleeve Connectors

Zhangrong Zhang ¹, Shaofei Jiang^1,*, Wanxia Cai¹, Chunming Zhang²

The authors wish to thank the reviewers for their constructive comments. We have revised the paper based on the comments from reviewers. In the new revision, modifications and corrections are marked with special colors. A summary is given below:

Point. 1 The author should emphasize the content in the manuscripts, and give the details about how to consider the incompactness of grout in connector through the anchorage length of rebar l_b.

Answer: The authors agree with the reviewer’s comments and appreciate to the valuable suggestion. The details about how to consider the incompactness of grout in connector through the anchorage length of rebar l_b were given in the new manuscript. More details can be seen in Section 3.

We sincerely hope that this revised manuscript has addressed your comments and suggestions. We appreciated for reviewers’ warm work earnestly, and hope that the correction will meet with approval. Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.docx