Lattice Fracture Model for Concrete Fracture Revisited: Calibration and Validation

Round 1

Reviewer 1 Report

The authors should better highlight in the abstract and introduction the RESEARCH SIGNIFICANCE of the manuscript.

The authors should improve section 5 (discussion) of the manuscript, providing further details on the analysis made.

Author Response

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Reviewer 2 Report

COMMENTS ON APPLSCI-846930

TITLE: Lattice Fracture Model for Concrete Fracture 2 Revisited: Calibration and Validation

In this paper, a calibration procedure, which depends on a combination of two uniaxial tensile tests, is presented in order to determine the input parameters of lattice elements - tensile strength, elastic modulus and bending influence factor

The reviewer believes that the paper is well written and organized. An interesting calibration procedure for numerical analysis is proposed and a lot of experimental-numerical comparisons are presented.  According to the reviewer opinion the paper merits publication on condition that the following minor revisions are addressed.

 

1. In the Abstract, what do authors mean by “Delft lattice fracture model”?
2. Section 2, line 101. The W definition should be indicated as an equation.
3. Are the two uniaxial tensile tests, used for the calibration procedure, standardized? If yes, please indicate the standard.
4. Section 3, line 131: “the uniaxial tensile test performed by van Vliet and his co-workers”. Please, indicate the literature reference.
5. Section 3, line 151: “the numerical results show brittle behaviour than the experimental data”. Can the authors justify such discrepancy?
6. Section 3, line 152: “With respect to the crack patterns, a typical failure mode can be found and the main crack occurs in the middle of the specimen, which agrees well with the experimental results”. Can the authors provide an image to support such statement?
7. Section 4, line 166: “other experiment”. The reviewer suggests referring to experimental literature results.
8. In all tables Poisson's ratio and Normal force factor should be added.

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Reviewer 3 Report

The manuscript entitled "Lattice Fracture Model for Concrete Fracture Revisited: Calibration and Validation" presents the Delft lattice fracture model based fracture analysis and a method to calibrate input parameters of the lattice fracture model.

The manuscript is well prepared but it has the following issues that should be addressed.

1. The manuscript suffers from excessive language deficiencies. 
2. What is the reason for disagreement in Figure 8 (b)? The authors explain that the inaccuracy in the case of smaller diameter is due to the relatively large element size compared to specimen size and boundary condition. It does not explain the inaccuracy in the case of the largest diameter, 152 mm.
3. If the numerical results are sensitive to the cell size, the effect of cell size should be demonstrated. How did the authors select 2.5 mm as the cell size?

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Reviewer 4 Report

The main work of this paper is to use the lattice beam network model (LBM), which was published by Schlangen and van Mier, for reviewing several published works based on a proposed systematic calibration procedure. The reviewer realizes that there are no interesting simulation results through the calibration procedure compared to the existing works since the post-peak behavior is still brittle in the model. This still results in a big discrepancy between experiment and numerical load-displacement curves.

Besides, in the LBM, authors used Timoshenko beam to calculate shear deformation with considering the ratio of length and cross section for the beam. Please clarify the chosen parameter of the above ratio as 0.2 (randomness) in this study?

In the equation (2), author mentioned to some input parameters for simulating concrete fracture using LBM such as Elastic modulus (E), the normal force and bending influence factor (α_N and α_M), etc…Please clarify the chosen E value (0.18) instead of 0.2 as usual? The author just focusses on determining the α_M based on the proposed procedure and assumed α_N= 1.0 as other works have done. The reviewer believes that such assumption leads the proposed calibration procedure to the same drawbacks as the previous works encountered. This made reviewer feel that there is no novelty in this study.

Finally, reviewer wants authors to bring more new thought and underpin the novelty in this work before publishing. Please carefully check whether there is any new study in this review recently published by other research groups and apply the proposed calibration procedure into the newly published results to see what happens then.

Reviewer is concerned about the repeatability of this numerical calibration. Did author used particular software code or develop your own code ? If software is used, author should provide the input data or model for reader to review and verify the result. The research results are meaningless if it cant be replicated. 

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Round 2

Reviewer 3 Report

Your corrections and improvements are appreciated. Proofreading by a native speaker or an experienced language professional is still needed.

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Reviewer 4 Report

I think author tried to address the comments resonably.

This is still an old topic, where I think the benefits would be how people can use this numerical model for their work. 

Modelling time is not mentioned here, to see how practical and painful it is. How it is novel and more insightful compared to current commercial or ope sourced software. 

Ii highly recommend author to submit the models they use and open source for reader to use.

Author Response

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