Flexural Behavior of Post-Tensioned Concrete Beams with Multiple Internal Corroded Strands

Round 1

Reviewer 1 Report

 

1. Experiment scope is too narrow (only 4 beams and 1 control beam are tested). Three beams had corrosion at supports, one had corrosion at the middle of span. The corrosion of strands could lesser adhesion between concrete and reinforcement, but not the withstand of bending moment. Therefore, there was no reason to test strands. The reduction of strands cross section in the middle of beam (where moment of bending is maximum) reduced holding capacity of the beam and moment of occurrence of cracks – it is obvious without the experiment (theoretically and practically). Experiment itself is not logical.
2. A) Theoretical part of the article is sufficient. Suggested methodology could be adapted for analyses of experiments.
3. B) Chosen limit of 5 % of beam corrosion raises serious doubts (second conclusion), where transition from bilinear material model to brittle material model is made;
4. Illogical statement in the second conclusion: „Based on the tensile test results of the corroded strands, the ultimate properties of corroded 348 strands were defined. Because the ultimate strain decreased sharply after section loss of 5% “. Ultimate strain of metal cannot decrease due to partial corrosion of experimental strand cross section.
5. It would be appropriate to waive experimental part of the article and edit the theoretical part with better argumentation. Edited theoretical part of this article could become a good quality article itself.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

1. Line 36. This sentence seems to be unnecessary since the elaboration of the topic began in the first paragraph of this chapter.
2. Figure 1. Please add measurement units.
3. Table 1. Please elaborate more on the differences between specimens CB2, CB3 and CB4 since these are not quite clear from the table concerned. This circumstance together with a small number of identical specimens (very important for concrete elements testing) makes it very hard to have strong conclusions.
4. Can you please be more precise regarding the values indicated in Table 2. Namely, are the indicated values average values, were the tests concerned performed according to standards etc.
5. Line 216. Figures 6b and 6c instead of 5b and 5c.
6. Table 4. Section loss column is missing a measurement unit.
7. Reference 1 has been partially written in uppercase letters.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper presents the results of experimental research carried out to investigate the effects of corrosion on the flexural behavior of post-tensioned concrete beams with multiple internal corrode strands. Five prestressed concrete beams with strands having different levels of corrosion and position were fabricated and tested, to evaluate strength reduction with increasing of corrosion level. Also, to evaluate the reduced elongation of PC beams, a wide analysis with OpenSEES software is carried out.

The paper is well written, and the experimental campaign is carried out thoroughly. Overall, it is a good work with scientific soundness.

Authors are invited to address the following minor remarks for improving the quality of the manuscript:

     - the introduction can refer to some more generic literature studies about the effect of steel corrosion in RC structures.  For example the following references can be added

Campione, G., Cannella, F., & Minafo, G. (2016). A simple model for the calculation of the axial load-carrying capacity of corroded RC columns. Materials and Structures, 49(5), 1935-1945.

Malumbela, G., Alexander, M., & Moyo, P. (2009). Steel corrosion on RC structures under sustained service loads—A critical review. Engineering Structures, 31(11), 2518-2525.

• Line 106: authors propose to use Eqn. (1-3) for the determination of area losses due to pitting corrosion. In my opinion, a comparison with models presented in the literature can be useful. For example, authors could refer to:
  • Lu Z., Li F., and Zhao Y. 2016. “An investigation of degradation of mechanical behaviour of prestressing strands subjected to chloride attacking.” Paper presented at 5th International Conference on Durability of Concrete Structures, Shenzen University, Shenzhen, Guangdong Province, P.R. China, June 30-July 1.
• Line 216: please correct “5b & 5c” with “6b & 6c”.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

ok

Reviewer 2 Report

Dear Authors,

thank you for your answers, you have made some things clearer.

However, from an experimentalist's point of view, there is a lack of experimental data for the validation of your models. That is the main reason for rejecting this paper.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

1. The author need to indicate how many cross-sectional loss measurement of each corroded strands were taken. Is the cross-sectional loss a average value or Max. value along the strands? How can author discuss the failure of PC beam specimens without such detail cross-sectional loss data.
2. Are all the concrete beam specimens have the same strength? Can the strength of the concrete affect the beam test results?
3. Line 132-134, no corrosion strand concrete beam test result cannot be used as a control set for comparison. Therefore, it is very difficult to verify the influence of the degree of corrosion to the strength of the specimens.
4. In Table 4, a wide range of section loss were found for each wire in a strand. How can author correlate section loss with the beam test results?
5. For the discussion of Flexural strength evaluation of corroded PC beam, it seems has no correlation with the corroded strand concrete beam test results.

Reviewer 2 Report

1. Experiment scope is too narrow (only 4 beams and 1 control beam are tested). Three beams had corrosion at supports, one had corrosion at the middle of span. The corrosion of strands could lesser adhesion between concrete and reinforcement, but not the withstand of bending moment. Therefore, there was no reason to test strands. The reduction of strands cross section in the middle of beam (where moment of bending is maximum) reduced holding capacity of the beam and moment of occurrence of cracks – it is obvious without the experiment (theoretically and practically). Experiment itself is not logical.
2. A) Theoretical part of the article is sufficient. Suggested methodology could be adapted for analyses of experiments.
3. B) Chosen limit of 5 % of beam corrosion raises serious doubts (second conclusion), where transition from bilinear material model to brittle material model is made;
4. Illogical statement in the second conclusion: „Based on the tensile test results of the corroded strands, the ultimate properties of corroded 348 strands were defined. Because the ultimate strain decreased sharply after section loss of 5% “. Ultimate strain of metal cannot decrease due to partial corrosion of experimental strand cross section.
5. It would be appropriate to waive experimental part of the article and edit the theoretical part with better argumentation. Edited theoretical part of this article could become a good quality article itself.