Revisiting Cracking in Reinforced Concrete Beams: An Updated Analysis
Round 1
Reviewer 1 Report
The manuscript explored 18 experiments on 27 reinforced concrete beams to investigate crack location, cracking moment, corresponding deflection, and crack width values as sag increases. The experiments in this manuscript is clearly introduced and thus I recommend publishing it with minor reversions.
1. Experiments are clearly introduced but the main disadvantage of this manuscript is that it lacks novelty. The experiments are repeated again and again and the conclusion is too obvious. The authors have to deal with the problem. a) Specify the novelty and innovation parts more. b) Provide more theoretical descriptions for the experimental results.
2. It would be better if the authors could provide more information about beam choices in table 1. The current description is not clear enough.
3. If it is possible, put some figs from fig11 -20 together and thus it is easy to compare some results.
4. Please rewrite the discussion part to make this part more conclusive.
Author Response
Author's Reply to the Review Report (Reviewer 1)
The authors are grateful for the time spent and the work of the reviewer. As a consequence, the article has improved. Response to the reviewer’ comments follows:
General:
Reviewer: The manuscript explored 18 experiments on 27 reinforced concrete beams to investigate crack location, cracking moment, corresponding deflection, and crack width values as sag increases. The experiments in this manuscript is clearly introduced and thus I recommend publishing it with minor reversions.
Authors:
Response: The authors are grateful for the reviewer's recommendation.
Action on the article: n.a.
Reviewer: Experiments are clearly introduced but the main disadvantage of this manuscript is that it lacks novelty. The experiments are repeated again and again and the conclusion is too obvious. The authors have to deal with the problem. a) Specify the novelty and innovation parts more. b) Provide more theoretical descriptions for the experimental results.
Authors:
Response: In an experimental investigation, or even in numerical work, when one more result is presented about a well-known parameter (for example, the compressive strength fc), 5 or 6 specimens could be considered as sufficient. Knowing the composition of the concrete, one knows how to theoretically estimate the fc value. If the experimental value coincides with the theoretical value, 5 to 6 specimens are sufficient. What if it's different? What to do if we have a deviation of 10 to 20%? Well, in this case more results are needed (say, 10 samples, 15?). What should be the strategy if we have a ground-breaking result? How many results are needed? The reviewer writes “The experiments are repeated again and again and the conclusion is too obvious”. This is true, but we believe that it is necessary due to the ground-breaking aspect of the issue. When the reviewer writes “lacks novelty”, the authors respond that this article is not only original; it is ground-breaking. And why is it ground-breaking? Let's see: it has always been assumed that the crack width is determined from a product in which one of the terms is the crack spacing. And all researchers, and all codes of practice and technical standards, establish equations (theoretical and experimentally) for this crack spacing. Now, the authors appear to say it's not like that; this spacing depends on the position of the stirrups. Isn't it ground-breaking? For a normal reader, the reaction could be of some surprise. As senior researchers, we are very cautious in accepting new explanations that contradict well-established theories. Therefore, we need a large number of test cases to convince ourselves of the new findings, and therefore, we believe that this amount of work would help to convince the readers.
Action on the article: The authors added several sentences in the discussion section to provide more theoretical descriptions and the conclusions point at the end of the article where the ground-breaking is shown.
Reviewer: It would be better if the authors could provide more information about beam choices in table 1. The current description is not clear enough.
Authors:
Response: Reviewing the previous answer, what the authors intended was to find a way that does not offer doubts regarding the positioning of the cracks. And therefore, in the authors' idea, the number of examples was the most important.
Action on the article: A sentence has been added at the end of old point 3.1 (new point 3.2; new Line 371) addressing this concern.
Reviewer: If it is possible, put some figs from fig11 -20 together and thus it is easy to compare some results.
Authors:
Response: Would it be possible to join figures? Yes, it would be possible, but the authors believe that they have reached a limit for the clarity of the figures with the number of figures they presented. Too much lines would highly increase the confusion. The authors apologize for not having answered affirmatively in this point, but they do believe that the original choice is just about right.
Action on the article: n.a.
Reviewer: Please rewrite the discussion part to make this part more conclusive.
Authors:
Response: The authors agree with the comment. In fact, the origin of the commentary lies in the humility of the authors in presenting these conclusions. Being ground-breaking, they need to be well founded and justified.
Action on the article: The authors added several sentences to the point of discussion in order to make this point more substantiated and justified.
Author Response File: 
Author Response.docx
Reviewer 2 Report
1. In line 63, the word 'form' seems to be not correct in the context. It is recommended to use a sinonimous as 'appear' or rewrite the paragraph and use 'formation'. It is just a recommendation
2. In line 119, the words 'consider the crack spacing' seem to be out of context becauses of th dot before 'By'.
3. Between lines 139-140, the words 'And complete' have a lack of subject (Piyasena I guesss)
4. It is recommended to avoid the 1st person (line 181, 189, 322, 361,364)
5. In line 185, wrong use of capital letter 'Another'
6. In general terms, a very interesting research. I have no comments about the results, and they seem to be correct and reflect the huge information about cracking. One comment about the conclusions of the axial confinement (line 707) in order to reduce crack widths, can the authors give some explanation about this phenomenon?, it seems to me that it is similar to the confinement in shear walls which is related to horizontal spacement of steel reinforcement increasing the confined core, and if this is applied to beams, it implies a reduction of stirrups spacement, decreasing the possible crack widths.
7. Another comment, why the autors cited ACI 318-08 instead ACI 318-19?. ACI 318-19 has a lot of modifications related to shear and cracking. For instance, cracking moment is compare no more to Mcr, instead it is now 3/4Mcr, and also Icr has a modification in order to accurate the deflections, and also, incorpores several information about Timoshenko beams (deep beams).
Author Response
Author's Reply to the Review Report (Reviewer 2)
The authors are grateful for the time spent and the work of the reviewer. As a consequence, the article has improved. Response to the reviewer’ comments follows:
Reviewer: In line 63, the word 'form' seems to be not correct in the context. It is recommended to use a sinonimous as 'appear' or rewrite the paragraph and use 'formation'. It is just a recommendation
Authors:
Response: The reviewer is right. Thank you.
Action on the article: Word “form” was changed by “appear”.
Reviewer: In line 119, the words 'consider the crack spacing' seem to be out of context becauses of th dot before 'By'.
Authors:
Response: The authors has revised this sentence. Thank you.
Action on the article: “Consider the crack spacing. By this time (the 1990s), many …” was changed by “Considering the crack spacing, by this time (the 1990s), many …”.
Reviewer: Between lines 139-140, the words 'And complete' have a lack of subject (Piyasena I guesss)
Authors:
Response: Of course. The authors have revised this sentence. Thank you.
Action on the article: “And complete: …” was changed by “And Piayasena complete: …”.
Reviewer: It is recommended to avoid the 1st person (line 181, 189, 322, 361,364)
Authors:
Response: The authors have revised this issue. Thank you.
Action on the article:
- Old Line 181; new Line 181: “The authors” instead of “we”;
- Old Line 189; new Line 190: “As it will be seen later …” instead of “As we will see later …”;
- Old Line 237; new Line 238: “the” instead of “our”;
- Old Line 322; new Line 332: “we” was removed;
- Old Line 361; new Line 377: “the” instead of “our”;
- Old Line 364; new Line 380: “the” instead of “our”;
- Old Line 397; new Line 404: “the” instead of “our”.
Reviewer: In line 185, wrong use of capital letter 'Another'
Authors:
Response: The authors do not agree with the reviewer.
Action on the article: n.a.
Reviewer: In general terms, a very interesting research. I have no comments about the results, and they seem to be correct and reflect the huge information about cracking. One comment about the conclusions of the axial confinement (line 707) in order to reduce crack widths, can the authors give some explanation about this phenomenon?, it seems to me that it is similar to the confinement in shear walls which is related to horizontal spacement of steel reinforcement increasing the confined core, and if this is applied to beams, it implies a reduction of stirrups spacement, decreasing the possible crack widths.
Authors:
Response: Thank you. “some explanation about this phenomenon?” Of course. This is another matter to be dealt with shortly; in another article. In the laboratory, in a usual test of a beam, the axial deformation of the beams is free, the axial force is zero. In real of structures (building frames) this does not happen. That is, among columns and slabs, the beams are subjected to some axial restraint; this mean that they are subjected to axial compressive forces. Therefore, taking laboratory results of non-axially restricted beams into actual beams of building frames lacks consideration of this phenomenon. In the laboratory, we have already recorded axial deformations greater than 1% long after the yielding of the reinforcement bars. This is a deformation which, if it were to occur in reality, in the plastic hinges, would lead to the non-use of the constructions. This does not happen, exactly because the other parts to which the beam is connected guarantee some axial confinement of the beam. And this axial compressive stress induces negative axial strains in the beam, which contribute to the reduction of crack widths. This is a subject that reserves a full paper to be well described and, obviously, cannot be added in the current manuscript, which already has itself a big amount of information.
Action on the article: The authors have introduced a small sentence in discussion point referring this issue. New Line 737.
Reviewer: Another comment, why the autors cited ACI 318-08 instead ACI 318-19?. ACI 318-19 has a lot of modifications related to shear and cracking. For instance, cracking moment is compare no more to Mcr, instead it is now 3/4Mcr, and also Icr has a modification in order to accurate the deflections, and also, incorpores several information about Timoshenko beams (deep beams).
Authors:
Response: Of course. The authors must follow current regulations. Thank you. But, ACI 318-19 still continues to determine the Mcr from equation (1), as before. Check equation (24.2.3.5) of ACI 318-19. What ACI 318-19 does (theoretically) is to consider that state I of the behavior of beams and slabs ends when M=3/4Mcr. That is to say, that the cracked phase must be started when M=3/4Mcr, considering effective moment of inertia (Ie) according to the equation indicated in Table 24.2.3.5.
Action on the article: n.a.
Author Response File: Author Response.docx
Reviewer 3 Report
Dear authors,
You can find my comments on your manuscript in attached file.
Regards
Comments for author File: 
Comments.pdf
Author Response
New Reviewer 3: Author's Reply to the Review Report
The Comments of this reviewer arrived very late and the authors only had time to change the manuscript considering the suggestions but did not have time to prepare a text with a detailed response to the reviewers’ suggestions.
Author Response File: Author Response.docx
Reviewer 4 Report
10 March 2023
Review of the manuscript 2294472
“Revisiting cracking in reinforced concrete beams: An updated analysis”
I understand that authors experimental data about cracking in reinforced concrete. However, as a mechanical designer I have some questions about this manuscript as follows.
1. This manuscript has no conclusion, so please clear some conclusions at the end of the manuscript as a section 6.
2. Page 1, Introduction, line 31 and line 40: Abbreviations ACI and EC2 need full spells of “American Concrete Institute” and “European Concrete Design Standard” at the first of manuscript.
3. Line 67, equation (1), Table 1, Table 2, Author uses the symbols L, h, b before Figure 2. Therefore, Figure 2 should move at first of Experimental Procedure (line 318).
4. Line 342-344: Author explains about the steel positioning by using the symbol like “af10, f6@60”, but I cannot understand. Please add some schematical figure to help understanding the beam positions.
5. Page 9, 3.2 Materials: I think the strength and crack propagation of used concrete are strongly affected by the mixture rate of cement elements like a sand, aggregate and water. Please add the data of mixture rate in the research by using additional Table.
6. Page 10, line 386-389, Figure 5 b); Author explains “In fact, the cracks occur in the position of the stirrups.”. I understand the phenomenon. However, I think that the stirrups act as the starter of clacking, so existence of stirrups is dangerous for design of concrete structure.
7. Table 4; I understand the values of M*cr /Mcr is (the cracking initiation moment)/(applied testing moment), so the value is one of the safety factor. The range of value is very low level of 0.6 to 1.34. I don’t use this data because I design machine structure with a safety factor of 5 to 10. Please show the meaning of these data to design a concrete structure.
8. Figure 10-19; I understand these data are process of constant growing of multiple cracks in concrete beam. As a designer point of view, if a crack occurs, I make an effort to stop propagation and reinforce it. The author should show useful conclusions for concrete design from these data.
That all my opinions.
Comments for author File: Comments.docx
Author Response
Author's Reply to the Review Report (Reviewer 4)
The authors are grateful for the time spent and the work of the reviewer. As a consequence, the article has improved. Response to the reviewer’ comments follows:
General:
Reviewer: I understand that authors experimental data about cracking in reinforced concrete. However, as a mechanical designer I have some questions about this manuscript as follows.
Reviewer: This manuscript has no conclusion, so please clear some conclusions at the end of the manuscript as a section 6.
Authors:
Response: The authors agree with the commentary. Thank you.
Action on the article: Conclusion point has been added and discussion point has been changed in order not to be only conclusions.
2.
Reviewer: Page 1, Introduction, line 31 and line 40: Abbreviations ACI and EC2 need full spells of “American Concrete Institute” and “European Concrete Design Standard” at the first of manuscript.
Authors:
Response: The reviewer is right. Thank you. These regulations are usual in construction and structural fields.
Action on the article: Abbreviation “ACI” was changed by “American Concrete Institute (ACI)” and Abbreviation “EC2” was changed by “Eurocode 2 (EC2)”. Old Lines 31 and 40.
3.
Reviewer: Line 67, equation (1), Table 1, Table 2, Author uses the symbols L, h, b before Figure 2. Therefore, Figure 2 should move at first of Experimental Procedure (line 318).
Authors:
Response: The authors agree. Thank you.
Action on the article: Subpoint 3.3 was placed at the beginning of point 3 and readjusted.
Reviewer: Line 342-344: Author explains about the steel positioning by using the symbol like “af10, f6@60”, but I cannot understand. Please add some schematical figure to help understanding the beam positions.
Authors:
Response: These technical designations are usual in draws of construction industry.
Action on the article: The Lines 342-344 (new Lines 352-355) was rewritten in order to clear this issue and Fig 2 shows “2 leg stirrups”.
Reviewer: Page 9, 3.2 Materials: I think the strength and crack propagation of used concrete are strongly affected by the mixture rate of cement elements like a sand, aggregate and water. Please add the data of mixture rate in the research by using additional Table.
Authors:
Response: The reviewer is right. However, each group of beams are concreted separately and each concrete is provided by a particular ready-mixed concrete company. For this reason, the authors do not have this information, which, incidentally, is secret. Companies use privileged information about additives. In these beams we have 5 different types of concrete (unknown composition), and a mortar (made by us; composition in weight cement=1 : sand=4.5 : water=0.55; SikaViscocrete 20HE superplasticizer was added in the amount of 0.9% of the cement weight). In the construction area, and with regard to concrete, there are rules and procedures to which these companies are subject in order to guarantee the quality of the product supplied. And then the compression tests, carried out by us, allow us to know the strength characteristics of the material. We know a little more, for the sake of ordering. We know that the maximum dimension of the aggregates was 10mm (gravel D10). And we also know that the w/c ratio was the lowest possible (additives) in order to guarantee resistance while saving on cement.
Action on the article: n.a.
Reviewer: Page 10, line 386-389, Figure 5 b); Author explains “In fact, the cracks occur in the position of the stirrups.”. I understand the phenomenon. However, I think that the stirrups act as the starter of clacking, so existence of stirrups is dangerous for design of concrete structure.
Authors:
Response: The reviewer is not right. In ultimate limit states, stirrups are necessary to ensure safety against the shear forces of the beams. In addition, by regulation, it is mandatory to have a minimum of stirrups (Asw,min and limited longitudinal and transverse spacing). For example, beams such as “B05”, or “B11” are not allowed in practice.
Action on the article: n.a.
Reviewer: Table 4; I understand the values of M*cr /Mcr is (the cracking initiation moment)/(applied testing moment), so the value is one of the safety factor. The range of value is very low level of 0.6 to 1.34. I don’t use this data because I design machine structure with a safety factor of 5 to 10. Please show the meaning of these data to design a concrete structure.
Authors:
Response: The authors do not want to express themselves in the field of mechanical engineering, obviously. Anyway, taking into account our general knowledge of mechanics, we can always say that these are 2 areas with different problems to solve. If in the “machine structure area” dynamics are a crucial phenomenon, in the “structural building area” statics are sufficient (we also consider dynamic phenomena such as wind, earthquakes, explosions, etc.). And then the fatigue that limits service stresses. If in machines, the service stress ranges between smin=-s and smax=s, along n*106 or n*109 times, it is not surprising that smax < fy/10. With regard to the M*cr /Mcr quotient, the authors only intend to draw attention to the way (sometimes insecure, other times conservatively) in which the theoretical value (any safety factor is included in tests) has been calculated in practice. In design, the safety factor will appear defining fc=fcd.
Action on the article: n.a.
Reviewer: Figure 10-19; I understand these data are process of constant growing of multiple cracks in concrete beam. As a designer point of view, if a crack occurs, I make an effort to stop propagation and reinforce it. The author should show useful conclusions for concrete design from these data.
Authors:
Response: At beginning, the reviewer is right. But for economic reasons, reviewer is not right. Let's see. The cracking strain of the concrete is ~0.1‰. For this strain level, the stress in the steel is ~20 MPa ~4%fy. That is, from an economic point of view, it is not possible to use only 4% of the strength of steel. Cracking for civil construction is a shortcoming similar to the “errors” of numerical analysis: they are inevitable and have to be controlled. Hence the regulatory restrictions for the crack widths, that is, it is necessary to know how to calculate the crack widths.
Action on the article: The authors added a sentence to the discussion point: old Line 685; new Line 693.
Author Response File: Author Response.docx
