- Email: [email protected]
Peer review report 2 on “Investigation on fracture parameters of concrete through optical crack profile and size effect studies”
Engineering Fracture Mechanics 133 Supplement 1 (2015) 221–222
Contents lists available at ScienceDirect
Engineering Fracture Mechanics journal homepage: www.elsevier.com/locate/engfracmech
Peer Review Report
Peer review report 2 on ‘‘Investigation on fracture parameters of concrete through optical crack profile and size effect studies” Original submission Recommendation Major amendments required Comments to the author General remarks: 1. Why is the method called OCP but not the Digital Image Correlation (DIC) technique? Why is DIC not listed in the paper? 2. What is the precision of the OCP method? What is the influence of different parameters on the results (length resolution, search patch, distance between search patch centres – see the paper Skarzynski and Tejchman, Strain, 2013)? 3. The results on FPZ should be compared with the work by Skarzynski and Tejchman (Strain, 2013) and works by Alam et al. 4. Section 2: The concrete properties should be given in detail. What was the elastic modulus, tensile strength? Were two different concrete mixes used in the experiments? 5. The displacement profiles have to shown to in order detect a macro-crack (displacement jump). 6. The results OCP were shown for one beam only. What is the effect of the beam size and aggregate size on FPZ? Other remarks: 1. Nomenclatures: a) w – crack opening displacement b) B_f t = empirical parameter to be identified by optimum fitting of measured r_Nu c) P_c = peak/maximum load of beam d) r_b = bridging stress e) r_Nu = nominal strength 2. Page 1, line 12: ... and Jenq-Shah are also ... and Jenq-Shah model are also ... 3. Page 1, line 25: ... measurements are extremely important because it helps ... measurements are extremely important because they help ... 4. Page 2: line 22: There are many methods for pattern application ... Which method was used here? (the answer was given in page 5). 5. Page 3, line 7: ... maximum load P_c having the dimension of stress ... P_c has the dimension of force 6. Page 4, line 3, Figs. 2 and 9b, Table 2: There are two fracture energies: initial G_f and total G_F. Only one symbol is used in the text to define these both quantities.
DOI of published article: http://dx.doi.org/10.1016/j.engfracmech.2015.08.027
http://dx.doi.org/10.1016/j.engfracmech.2015.08.033
222
Peer Review Report / Engineering Fracture Mechanics 133 Supplement 1 (2015) 221–222
7. Page 4, line 4: Using the concept shown in Fig. 2, the r-w relation at various stages of crack growth along the projected ligament is established through OCP technique. How are you able to retrieve stresses using OCP? You may only obtain displacement w, and then calculate stress from the assumed relationship. 8. Page 4, line 11: ... (3) through the displacement jump across the two sides of the crack [5] from OCP technique. How is it exactly performed? How do you detect the displacement jump with the critical opening w_c? At which load level? 9. Fig. 8: One should expect that the largest horizontal displacements are just above the notch. Then the largest horizontal strains should occur also there. 10. Page 6, line 17: Crack openings can be obtained from the displacement jump across the two sides of the crack Describe in detail how the crack is detected by OCP? 11. Page 10, line 17: Jenq and shah => Jenq and Shah (capital letter) 12. Fig. 10: improve the description. Is the contour of the horizontal strains presented? In the post-peak region, a crack occurs. The show of the horizontal strain from the continuum bulk has no sense if there is a displacement jump. 13. Page 11, line 22: where FPZ becomes prominent, is observed to be 810 l In Table 2 the value 1101 is given. Explain this difference. 14. Page 12: horizontal displacement profiles should be shown. How was the macro-crack determined? 15. Page 12: The FPZ width is found to be in range 2533 mm (very large). It should be determined at the peak. Compare it with the values in the literature. Note that the localized zone is curved but the sections for describing its width are horizontal. 16. Fig. 14a: how was the stress (vertical axis) calculated? In which point? Note that the horizontal axis is the integral of strains over a segment. 17. Fig. 14b: what is the interpretation of the very strong dependence of the fracture energy on the point location/height? Is it physical? 18. Page 13, line 5: How was the critical w_c determined in the experiment? 20. Page 13, line 9, Table 4: The values given are not from OCP (which criterion), but they were calculated from the assumed analytical softening laws. 21. Page 13, line 21, Fig. 17.: ... failure load is found to be zero. There is no elastic deformation in the point ’2’?. Improve the caption of Fig. 17. 22. Fig.18b: dimension D of the marked points does not agree with the tabular data. The maximum size is 750 mm (not smaller than 600 mm) 23. Page 14: conclusions from the analysis using different regression methods are missing. 24. Tables 1 and 8: correct the discrepancies of the dimension D: 95 and 190 versus 94 and 188. 25. Page 16, line 1: The fracture energy values are observed to be in range ... Does the fracture energy depend so strongly on the notch size (even by about 50%)? 26. Page 16, line 3: The sentence is not clear: The range of process zone length is found be 1 3 mm, 6.5 12 N/m and 7.6 14 N/m . . .. . ... 27. Figs. 21b and 22b: how was the tensile strength determined? What is its value (it influences the position of the straight lines). 28. Sub-section 6.4 should be better described. 29. Reference Unify the bibliography style. Anonymous reviewer
Contents lists available at ScienceDirect
Engineering Fracture Mechanics journal homepage: www.elsevier.com/locate/engfracmech
Peer Review Report
Peer review report 2 on ‘‘Investigation on fracture parameters of concrete through optical crack profile and size effect studies” Original submission Recommendation Major amendments required Comments to the author General remarks: 1. Why is the method called OCP but not the Digital Image Correlation (DIC) technique? Why is DIC not listed in the paper? 2. What is the precision of the OCP method? What is the influence of different parameters on the results (length resolution, search patch, distance between search patch centres – see the paper Skarzynski and Tejchman, Strain, 2013)? 3. The results on FPZ should be compared with the work by Skarzynski and Tejchman (Strain, 2013) and works by Alam et al. 4. Section 2: The concrete properties should be given in detail. What was the elastic modulus, tensile strength? Were two different concrete mixes used in the experiments? 5. The displacement profiles have to shown to in order detect a macro-crack (displacement jump). 6. The results OCP were shown for one beam only. What is the effect of the beam size and aggregate size on FPZ? Other remarks: 1. Nomenclatures: a) w – crack opening displacement b) B_f t = empirical parameter to be identified by optimum fitting of measured r_Nu c) P_c = peak/maximum load of beam d) r_b = bridging stress e) r_Nu = nominal strength 2. Page 1, line 12: ... and Jenq-Shah are also ... and Jenq-Shah model are also ... 3. Page 1, line 25: ... measurements are extremely important because it helps ... measurements are extremely important because they help ... 4. Page 2: line 22: There are many methods for pattern application ... Which method was used here? (the answer was given in page 5). 5. Page 3, line 7: ... maximum load P_c having the dimension of stress ... P_c has the dimension of force 6. Page 4, line 3, Figs. 2 and 9b, Table 2: There are two fracture energies: initial G_f and total G_F. Only one symbol is used in the text to define these both quantities.
DOI of published article: http://dx.doi.org/10.1016/j.engfracmech.2015.08.027
http://dx.doi.org/10.1016/j.engfracmech.2015.08.033
222
Peer Review Report / Engineering Fracture Mechanics 133 Supplement 1 (2015) 221–222
7. Page 4, line 4: Using the concept shown in Fig. 2, the r-w relation at various stages of crack growth along the projected ligament is established through OCP technique. How are you able to retrieve stresses using OCP? You may only obtain displacement w, and then calculate stress from the assumed relationship. 8. Page 4, line 11: ... (3) through the displacement jump across the two sides of the crack [5] from OCP technique. How is it exactly performed? How do you detect the displacement jump with the critical opening w_c? At which load level? 9. Fig. 8: One should expect that the largest horizontal displacements are just above the notch. Then the largest horizontal strains should occur also there. 10. Page 6, line 17: Crack openings can be obtained from the displacement jump across the two sides of the crack Describe in detail how the crack is detected by OCP? 11. Page 10, line 17: Jenq and shah => Jenq and Shah (capital letter) 12. Fig. 10: improve the description. Is the contour of the horizontal strains presented? In the post-peak region, a crack occurs. The show of the horizontal strain from the continuum bulk has no sense if there is a displacement jump. 13. Page 11, line 22: where FPZ becomes prominent, is observed to be 810 l In Table 2 the value 1101 is given. Explain this difference. 14. Page 12: horizontal displacement profiles should be shown. How was the macro-crack determined? 15. Page 12: The FPZ width is found to be in range 2533 mm (very large). It should be determined at the peak. Compare it with the values in the literature. Note that the localized zone is curved but the sections for describing its width are horizontal. 16. Fig. 14a: how was the stress (vertical axis) calculated? In which point? Note that the horizontal axis is the integral of strains over a segment. 17. Fig. 14b: what is the interpretation of the very strong dependence of the fracture energy on the point location/height? Is it physical? 18. Page 13, line 5: How was the critical w_c determined in the experiment? 20. Page 13, line 9, Table 4: The values given are not from OCP (which criterion), but they were calculated from the assumed analytical softening laws. 21. Page 13, line 21, Fig. 17.: ... failure load is found to be zero. There is no elastic deformation in the point ’2’?. Improve the caption of Fig. 17. 22. Fig.18b: dimension D of the marked points does not agree with the tabular data. The maximum size is 750 mm (not smaller than 600 mm) 23. Page 14: conclusions from the analysis using different regression methods are missing. 24. Tables 1 and 8: correct the discrepancies of the dimension D: 95 and 190 versus 94 and 188. 25. Page 16, line 1: The fracture energy values are observed to be in range ... Does the fracture energy depend so strongly on the notch size (even by about 50%)? 26. Page 16, line 3: The sentence is not clear: The range of process zone length is found be 1 3 mm, 6.5 12 N/m and 7.6 14 N/m . . .. . ... 27. Figs. 21b and 22b: how was the tensile strength determined? What is its value (it influences the position of the straight lines). 28. Sub-section 6.4 should be better described. 29. Reference Unify the bibliography style. Anonymous reviewer