Testing the Shear Strength of Mass Concrete Lift Lines: A Comparison of Procedures

Round 1

Reviewer 1 Report

The paper concerns the subject of using a novel method of concrete direct shear testing to characterize the shear strength of lift lines and concrete in the particular existing reinforced structure. According to the authors, the presented and applied test method gives better results than tests carried out according to the procedure described in ASTM D5607, as the standard method testing results in underestimated values of sliding friction angles and overestimated values of apparent cohesions. Moreover, the authors discuss the effect of the concrete specimens size (various core diameter) on the results of the performed tests.

The manuscript presents original testing, research results and modelling. In general the manuscript after some corrections (remarks are listed below) is suitable for publication in the "Infrastructures" journal.

Remarks (including editorial notes):

1) The figures and tables should appear later than the mention because otherwise manuscript is illegible for the reader. Please rearrange the manuscript in this regard.

2) Not all figures are mentioned in the text or there are mistakes in numbering. For example, Figure 3 is not mentioned in the text at all, although it seems that line 195 should read "Figure 3." instead of "Figure 4." Please revise the manuscript in this context.

3) The tables lack the units in which the presented values were expressed (the units should be clearly showed in the table not only mentioned in its caption).

4) In the section “2. Materials and Methods” there is no information about the tested material – the concrete - e.g. material composition, compressive strength class (tested on the concrete cores), age, etc. (Although the time of constructing of the dame was mentioned in the introduction part, it would be good to summarize information about the tested material in this particular section). The reviewer knows that the main purpose of the paper was to demonstrate the utility of the proposed method, but basic information about the tested concrete is needed for its identification also in order to be able to assess the correctness of the obtained test results. E.g. there is no information about the origin, type or grading of the aggregate, although further (in the text and in the conclusions) there are some references to the aggregate and its effect on the results. Meanwhile, different effect will be presented by natural aggregates and crushed aggregates made of different rocks. More detailed information about the tested concrete would enable development of the conclusions.

5) The work refers to a very small number of scientific sources - only 10 items are cited (including three ASTM standards and two auto-citations). Perhaps a more thorough analysis of the influence of the material composition of concrete on the tested properties would be helpful in the context of the analysis of the obtained results and conclusions summarizing this particular case.

6) In terms of reading comfort, it does not seem appropriate for words to be hyphenated at the end of a line. Moreover, review and correct the manuscript in terms of formatting - some text is not justified and there are multiple spaces.

7) It would be also advisable to use fewer colloquial wording and to use vocabulary more consistently - for example, the term "sample" appears in some parts of the text, and "specimen" in others (according to the reviewer these are not exactly synonyms).

Author Response

Please see the attached cover letter for a point-by-point response to all reviewer comments.

We very much appreciate the detailed review and feel the manuscript has been improved significantly.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors have modified an existing ASTM testing methodology of shear under normal stress. The manuscript presents new experimental data which increases the value of the manuscript. However, following shortcomings obstruct the publication of the manuscript in its current form.

1- The proposed methodology is not clear. Steps 3 and 4 should be explained in detail. Is it unloading or sliding shear force?

2- Provide figures for the steps of both test procedures.

3- Provide test results of shear force-slip displacement curves for all specimens.

4- Describe how values of the normal forces during tests were selected.

5- Line 154: What is selected by the lab engineer?

6- Provide a failure criretion from the presented test results.

Without these explanations, the manuscript is not expected to have much of scientific impact.

Author Response

Please see the attached cover letter for a point-by-point response to all reviewer comments.

We very much appreciate the detailed review and feel the manuscript has been improved significantly.

Author Response File: Author Response.docx

Reviewer 3 Report

The title is too general and one would expect rather pre-produced lab specimens, wherefore other literature is available directly matching the topic. Therefore the title should be adjusted, like: "Testing the shear strength of concrete lift lines: A comparison of procedures".

The introduction is lacking some aspects. In detail, the problematic nature of direct shear tests should be discussed.
Moreover, at least a quick overview of other test setups should be provided. A reference that could be provided is: Espeche, Leon: Estimation of bond strength envelopes for old-to-new concrete interfaces based on a cylinder splitting test, Construction and Building Materials 25 (2011) 1222–1235

The Authors are asked to provide schematic sketches of the exact test setups that were used and, based on these and referring to, explain the differences and the possible reasons for different results.

Results sections 3.1/3.2: The authors should discuss a bit deeper (or at least mention a bit more detailed) non-linear Mohr-Coulomb based approaches (envelopes). The following literature, which could be referred to, provides some hints on such Mohr-Coulomb envelopes: Randl, Zilch, Müller: Bemessung nachträglich ergänzter Betonbauteile mit längsschubbeanspruchter Fuge, Beton- und Stahlbetonbau, Vol. 103 / 7, p. 482 – 497, July 2008, https://doi.org/10.1002/best.200800627

Typo: line 141 - correct: "specimens"

Results - 3.2: If possible, please reflect more thoroughly the differences in the test results and mention the potential reasons therefore.

Author Response

Please see the attached cover letter for a point-by-point response to all reviewer comments.

We very much appreciate the detailed review and feel the manuscript has been improved significantly.

Author Response File: Author Response.docx

Reviewer 4 Report

This paper uses a new method concrete direct shear testing to characterize the shear strength of concrete. This method improves upon the typical direct shear procedure outlined in ASTM D5607 by varying normal loads in a matrix-oriented approach which accounts for the effects of shear strength degradation with sliding displacement. This research work has certain value for directly obtaining the shear strength of concrete. However, the detailed introduction of the method is lacking, so other researchers cannot reproduce this experiment. Therefore, the current version is not suitable for publication in infrastructure.

1)      In the Introduction, the review of the current research situation is not enough, and relevant research summary needs to be added.

2)      In the paper, the working principle and corresponding graphics of the test equipment are not found, and the test plan and detailed process are also missing.

 

3)      The test results are relatively discrete, what is the reason and how to reflect the advantages of the new method.

Author Response

Please see the attached cover letter for a point-by-point response to all reviewer comments.

We very much appreciate the detailed review and feel the manuscript has been improved significantly.

Author Response File: Author Response.docx

Reviewer 5 Report

In their manuscript "Concrete direct shear testing: A comparison of procedures", the authors compare the ASTM methodology to evaluate shear interface in concrete specimens with a modified proposed method. The experimental program and the methodology are interesting, but some improvements are demanded:

 

Major comments:

 

The introduction must be improved, including similar recent studies that evaluated direct shear in concrete specimens.

Lines 33 and 34 describe a numerical analysis not presented in this manuscript.

The paragraph at line 55 does not fit in this manuscript.

The difference between matrix procedure and ASTM must be explained better, as in the abstract.

The experimental procedure must be explained: a. The specimen's designation, what do 55A, 110A, and 220A in Table 1 mean? b.Why do stresses vary between slides 1 to 3 in random order? c. In table 3, the specimens are named Type A, B, and C, but why is different from specimens labeled 55, 110, and 220.

Line 126: "normal load schedules" but table 3 presents stresses values, review, how stresses were calculated?

Line 155: "where failure was selected by the laboratory engineer", based on what the laboratorist defined the failure? How this can influence the results?

In Table 5, I suggest to present all results, and at Figure 3, it seems to have just 5 data from 10.2 tests.

Line 202: "statistically, this difference is insignificant" which test determines this?

Based on the results discussed in lines 201 to 205, does the quality of lift lines is less influenced in bigger specimens? Is there a specific size for specimens?

Item 3.3 presents the results from compressive and tensile strength. How could these results be related to the sliding shear test results?

Minor comments:

The use of SI units is mandatory.

 

References numbers should be in crescent order.

 

Line 141: diamter speciemns

 

 

Author Response

Please see the attached cover letter for a point-by-point response to all reviewer comments.

We very much appreciate the detailed review and feel the manuscript has been improved significantly.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Most comments have been thoroughly tackled by the Authors. Concerning the linear vs. non-linear Mohr-Coulomb criterion, the Authors could add the following international literature to back up their discussion:

Are concrete-concrete bond tests comparable?, Cement and Concrete Composites, Volume 99, May 2019, Pages 80-88

 

 

Author Response

Thank you very much for the review.  All comments have been incorporated and are detailed in the attached cover letter.

Author Response File: Author Response.pdf

Reviewer 5 Report

The manuscript has been completely reviewed and is adequate. I recommend reducing the title in Figures 3, 5, 10, and 11. The explanation of the figures must at the text.

Author Response

Thank you very much for the review.  All comments have been incorporated and are detailed in the attached cover letter.

Author Response File: Author Response.pdf