Experimental Investigation of ECC Jackets for Repair of Pre-Damaged R.C. Members under Monotonic Loading

Round 1

Reviewer 1 Report

REVIEW

on article

Experimental Investigation of ECC jackets for repair of pre-damaged R.C. Members Under Monotonic Loading

 

SUMMARY.

The article is devoted to experimental studies of the technology of repairing pre-damaged reinforced concrete elements by applying deformation-hardening cement composites. The authors have manufactured a power plant for testing prototypes that simulate the operation of a column and cross beams. A static load is considered, which was applied monotonically under the control of displacement. The centre bar, which simulates the foundation part of the half-column, is lowered and the two crossbeams connected to the column are continuously sheared.

Thus, the authors investigated the strength of the structure. This problem is often encountered in construction practice and is an interesting scientific problem.

The reference list contains 21 items.

At the same time, the article has several inaccuracies.

 

COMMENTS.

1. The authors have to redo the Abstract and bring it in line with the requirements of the Buildings journal. Editors strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a broad context and highlight the purpose of the study; (2) Methods: Describe briefly the main methods or treatments applied; (3) Results: Summarize the article's main findings; and (4) Conclusions: Indicate the main conclusions or interpretations. The abstract should be an objective representation of the article.
2. The primary level of loading of prototypes has not been determined, at which there was damage to inclined sections from the action of a transverse force. What were the stresses (deformations) in the shear reinforcement clamps? Did the stresses in the reinforcement reach the yield point and fracture of the section, or were they less?
3. In table 2, the designation of the sample M3.1F10L35 does not correspond to the markings in table 1.
4. In section 2.4, after Table 2, there is a description of the fracture pattern (Figure 5), but in the text, Figure 5 is devoted to testing concrete and reinforcement to determine the strength characteristics.
5. In Fig. 6, 4 types of destruction of samples should be presented, and only 2 are presented.
6. 5 and 8, the dimension of the relative deformations of concrete 3000 mm / mm is not clear
7. In Table 4, ultimate tensile deformations of concrete ε_tu = 0.0092 (9.2x10-3) exceed the tensile deformability of standard concrete by an order of magnitude. This does not correspond to those given in the "Stress-strain" test diagram in Fig. 8 - 1500 mm / mm
8. 10 and section 2.7, the diagram does not clearly show the arrangement of the measuring equipment (13 LVDTS or DT). What are these devices?
9. The text of the article lacks data on the quantitative parameters of destruction. What is the opening width and crack length during initial loading and after reinforcement with fiber-reinforced concrete composite?
10. The article is missing a Discussion section. Authors need to conduct an in-depth analysis of the results obtained and compare them with the data obtained by other authors.
11. In the Conclusion, there is no computational analysis of the achieved effect of strengthening damaged inclined sections.

 

 

Author Response

1.Done:  The Abstract was revised as per the editor's template style. The series of abstract sentences correspond to the relevant article’s paragraphs discussion.  

2.Done: The following explanation has been included in the paper:

 

The loading level where damage was observed is shown in Table 5 and Figure 12. A brittle failure was observed (longitudinal reinforcement slip from the anchorage, intense diagonal cracking in the region adjacent to the support over a length of 2d, where d is the effective depth of cross section.  Longitudinal reinforcement yielded – but no bar fractures occurred.

3.Thanks for pointing out this typing error

4. Thanks for pointing out this typing error 

5.All four were presented in the original Fig. 6.  They were visible again in the left column of Fig. 11 where they were compared side by side with the retrofitted ones.  It is possible that something may have happened with the files’ pdf that reached the reviewer; please check again this point in the revised copy.  Samples of all specimens have been provided 

6.Thanks for pointing out this typo.  The value is multiplied by 10^-6. 

In the revised document Figures 5 and 8 have been redrawn. 

7.The tensile strain capacity of Strain Hardening Cementitious Composites (SHCC) is orders of magnitude higher than that of conventional concrete.  This is their true advantage. To measure the strain capacity in tension, prisms are bent in flexure and the tensile stress strain response is obtained from inverse analysis.  This analysis is presented in the Appendix according with the Annex 8 of the Canadian Bridge Design Code (CSA – S6 – 2019), and it leads to an estimated tensile strength, of 5 MPa, that can be sustained without collapse up to a strain of 0.0092 as listed in Table 4. 8.Figure 10 formatting has been revised, and all the measuring equipment is defined. LVDTs and DTs are defined in paragraphs 2.6 and 2.7 accordingly. The value with compared to by the reviewer is the circumferential strain of a cylinder tested under compression, at the point of attainment of peak axial compressive stress.  I.e., the value cited by the reviewer is the lateral strain due to Poisson’s effect.  This is a totally different stress state, not to be compared with that of tension stress-strain response.   9.Crack widths and the extent of cracking was marked on the specimen surfaces by the drift levels where they occurred (Figs. 6 and 11) – the values are visible when zooming into the pictures.  A paragraph discussing the details of damage has been added in line (353-361) of the document.  10.Currently there are only few studies of similar scope; usually even thin jackets contain some form of reinforcement.  We have enhanced Section 3.3. by discussing similar studies that we were able to locate in the literature and also our own results to a greater extent (430-500). 11.The quantitative effects of the intervention are summarized in the conclusions section of the revised document.  See lines 472-500

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper shows an experimental test on Rc member reinforced with ECC jacket. English needs to be improved. I suggest a revision by a mather tongue reviews. Figure and Table are precise. Overall it is a good paper, although it needs to be improved in several aspects. The introduction section needs to be improved to cover the following aspects:
1) About the retrofitting methods, I suggest discussing  papers about:
SRG system: 10.3390/cryst11030265
FRP system: 10.3390/FIB8060042
Etc.
2) At the end of the introduction section, the authors shall address the gap that they want to cover with the present research and provide an outline of the paper as well.
3) The paper provided for the review has serious editorial issues. Some pictures are not visible etc.
4) The plotted curve 13 and 14 seems to be generated by sampling to low points. I suggest increasing the sampling.

Author Response

1. The recommended references have been added and discussed in the review of the relevant retrofitting methods, see lines (32-35 & 41-43) of the revised document.

2. The objective of the present work is to investigate the contribution of ECC material in shear strength and confinement of existing, damaged reinforced concrete columns through concrete cover replacement.

   Discussion about the objectives pursued by the paper, and the methodology followed are discussed in (79-88).
3. In preparing the revised version, every effort has been made in adhering to the formatting requirements of the journal.
4. The sampling rate from the experimental data shown in Fig.13 and Fig. 14 was increased and the figures redrawn.  

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All my comments were reviewed and corrected by the authors in the text of the article. The graphic part has been corrected and supplemented with new, more informative graphs and diagrams. The article looks much better and will undoubtedly attract the interest of readers. I recommend the article for publication.

Reviewer 2 Report

The manuscript may be published in the present form