An Assessment of the Bearing Capacity of High-Strength-Concrete-Filled Steel Tubular Columns Through Finite Element Analysis

Reviewer #1:

Comments

Response

Comment1:
The current literature review lacks sufficient depth and breadth. It is recommended that the authors incorporate a comprehensive review of relevant studies, including, but not limited to, the following: “Behavior and Reliable Design Methods of Axial Compressed Dune Sand Concrete-Filled Circular Steel Tube Columns,” “Axial Compression Behavior and Reliable Design Approach of Rectangular Dune Sand Concrete-Filled Steel Tube Stub Columns,” and “Unified Prediction Models for Mechanical Properties and Stress-Strain Relationship of Dune Sand Concrete.” Integrating these sources will significantly enhance the manuscript’s analytical foundation and contextual depth.

Response to comment 1:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted by adding new references. We believe that these new references better contextualize the topic of the introduction.

Comment2:
In the survey flowchart (Fig. 3), the author mentions a parametric analysis in the final stage. However, the manuscript does not provide a detailed discussion or presentation of this analysis. It is necessary to either include a comprehensive parametric analysis or remove this reference from the flowchart for consistency.

Response to comment 2:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted by removing that reference from the flowchart.

Comment3:
In section 2.1, titled Constitutive Model, the title should be revised for clarity to “Constitutive Model of Materials” to accurately reflect the content discussed within the section.

Response to comment 3:

Dear reviewer, we appreciate your comment and have adopted your suggestion by updating the title in Section 2.1.

Comment4:
The subsection title “2.2. Finite Element” appears ambiguous, as the following paragraph discusses mesh sensitivity. It is suggested that this title be modified to either “Finite Element Model Establishment” or “Mesh Sensitivity Analysis” for clarity and alignment with the content.

Response to comment 4:

Dear reviewer, we appreciate your comment and have adopted your suggestion by updating the title in Section 2.2.

Comment5:
The manuscript does not specify the type of mesh used. It is advisable to use a structured mesh and perform a detailed mesh sensitivity analysis for the proposed model. It is also recommended to consult recent literature for guidance, such as the following references: doi:10.3389/fmats.2021.630774 and doi:10.1016/j.cscm.2022.e01115.

Response to comment 5:

Dear reviewer, we appreciate your comment, and we explain that:

The ABAQUS software features a mesh generator, and a free mesh was adopted for the work. It is in the reference:

Doi: 10.1016/j.jcsr.2013.07.001

Comment6:
It is recommended to merge Figures 6 and 7, providing a detailed representation of both mesh and boundary conditions for circular and square sections in a single figure. Additionally, the authors should generate their own models rather than using those from other researchers to ensure originality and clarity.

Response to comment 6:

Dear reviewer, we appreciate your comment, and we explain that:

These topics are being presented separately in the work. Fig. 6 is original, and Fig. 7 is sourced from a relevant reference in the field: doi: 10.18057/IJASC.2021.17.2.6.

Comment7:
The title of section 4, currently “Validation Study,” should be reconsidered for clarity. A more precise option could be “Validation of Finite Element Model” to accurately represent the section's content.

Response to comment 7:

Dear reviewer, we appreciate your comment and have adopted your suggestion by updating the title in Section 4.

Comment8:
The title and parameters presented in Table 7 are unclear and potentially confusing; for example, “Experimental (kN) = 1.006.” It is suggested that the mean and coefficient of variation for each column be included. The authors should follow references such as “Behavior and Reliable Design Methods of Axial Compressed Dune Sand Concrete-Filled Circular Steel Tube Columns” and “Axial Compression Behavior and Reliable Design Approach of Rectangular Dune Sand Concrete-Filled Steel Tube Stub Columns” for clearer presentation and consistency.

Response to comment 8:

Dear reviewer, we appreciate your comment, and we explain that:

The confusion may have been caused by a typo mistake in Table 7.  We corrected the title and implemented your suggestions by adding the mean, coefficient of variation and standard deviations.

Comment9:
In the discussion of results (lines 340–344), it is essential to reference the relevant figure or table associated with the outcomes discussed for clarity and traceability.

Response to comment 9:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted. The results mentioned in these lines refer to Table 7. Therefore, we have moved this section of the text to before Table 7 (lines 299-304) to improve clarity.

Comment10:
The limitations of the proposed approximation coefficient should be explicitly discussed, emphasizing any potential constraints or conditions under which it may not be valid.

Response to comment 10:

Dear reviewer, we appreciate your comment, and we explain that:

The global slenderness of the CFST columns was not considered in the analysis, which is a limitation of the coefficient (β). Future studies that include these analyses or the use of reduction factors due to column instabilities may solve the prediction of the ultimate load. We have added these considerations in lines 395–399.

Comment11:
When presenting the results after multiplying the proposed coefficient (β) by the axial bearing capacity of standards, these should be captured in a table or figure. Furthermore, a comparative analysis should be conducted to showcase the impact of this coefficient.

Response to comment 11:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted by adding Table 8.

Comment12:
The conclusion should be concise yet impactful, guiding readers toward future research opportunities. A more focused and conclusive ending will help create a lasting impression and encourage further exploration in this area.

Response to comment 12:

Dear reviewer, we appreciate your comment and have rewritten the conclusions with these suggestions (lines 402-425).

Comment13:
It is recommended to incorporate additional experimental results in the validation of the finite element analysis model. A comparison between the axial bearing capacity derived from experimental results and that obtained from finite element analysis and standards would significantly strengthen the validation process.

Response to comment 13:

Dear Reviewer, thank you for your comment. We appreciate your feedback and would like to explain that this is a perspective for future research.

Comment14:
It is advisable to employ consistent terminology, replacing frequently repeated terms with varied synonyms or phrasing to enhance readability while maintaining an academic tone.

Response to comment 14:

Dear reviewer, we appreciate your comment.

This suggestion has been adopted.

Comment15:
It is recommended that the authors review recent high-impact publications from the past five years on finite element analysis of axially compressed concrete-filled steel tube columns for improved structure and clarity. This would assist in refining the manuscript’s structure and making it more informative.

Response to comment 15:

Dear reviewer, we appreciate your comment.

This suggestion has been adopted by adding new references.

Comments on the Quality of English Language

The English language used in the manuscript is generally clear and understandable. However, there are a few areas that require refinement for clarity and alignment with academic standards. Minor revisions, such as ensuring consistent terminology and refining section titles for precision, would enhance readability and professionalism. Overall, the quality is adequate but could benefit from these adjustments for improved clarity.

Dear reviewer, we appreciate your cooperation, and we are extremely grateful. Thank you for reviewing our article. We accepted all comments for the correction of the article and believe the revised manuscript is improved because of those suggestions.

Reviewer #2:

Comments

Response

Geral Comments

The paper is generally well-written and well-structured, with findings that are relevant and contribute to current research. It has the potential to be accepted; however, major revisions are recommended to enhance clarity and address key issues.

Dear reviewer, we appreciate your cooperation, and we are extremely grateful. Thank you for reviewing our article. We accepted all comments for correcting the article and believe those suggestions improved the revised manuscript.

Comment1:

The authors should construct the abstract by highlighting the purpose of the study methodology, main findings, and implications separately. This will enhance clarity and focus for the reader.

Response to comment 1:

Dear Reviewer, thank you for your feedback. We would like to clarify that the information you mentioned is already included in the abstract, where we outline the study's purpose, methodology, main findings, and implications. Specifically, we highlight how our findings contribute to “safer and more efficient design practices in structural engineering.” (lines 21-22).

Comment2:

The authors should provide a brief explanation in the manuscript for why High-Strength Concrete (HSC) was selected for this study. Why does this study focus solely on conventional CFST columns, considering there are other types of CFST? What implications does this choice have on the applicability of the findings?

Response to comment 2:

Dear Reviewer, we appreciate your insightful comment. We would like to clarify that we have addressed this point in lines 100-106, where we explain.

Comment3:

There are many similar studies to your research, what is the difference between your studies and the existing study carried out?

Response to comment 3:

Dear Reviewer, we appreciate your comment, and in response, we have added lines 142-152 to the text to provide further justification on this matter.

Comment4:

The authors should ensure the consistent numbering in section and subheadings throughout the manuscript. This will improve the overall readability and organization.

Response to comment 4:

Dear reviewer, we appreciate your comment.

This correction has been made.

Comment5:

The authors should check for order flow in the methodology into clear sub-sections such as "Numerical Modeling Approach," "Finite Element Analysis Parameters," and "Validation Process." This will make the reader to understand.

Response to comment 5:

Dear reviewer, we appreciate your comment and have adopted your suggestion by updating the title in Sections 2.1, 2.2, and 4.

Comment6:

The authors should provide a more detailed explanation of how key parameters, like the dilation angle and other coefficients, were selected. Justify these choices taken with the literature review support.

Response to comment 6:

Dear reviewer, we appreciate your comment, and we explain that in the following:

·         Regarding the dilation angle, a value of 25° was considered for circular sections and 40° for rectangular sections (lines 289-293), by the sensitivity analysis and literature: doi: 10.1016/j.jcsr.2013.07.001.

·         The calibration coefficient for the support varies with each experiment (lines 285-286).

Comment7:

The authors should explain the advantages of using solid elements C3D8R for both steel and concrete in the context of this analysis?

Response to comment 7:

Dear reviewer, we appreciate your feedback and would like to clarify that. We have added lines 212-216 to the text to explain the advantages of using solid elements C3D8R.

Comment8:

The authors are requested to explain why the Concrete Damage-Plasticity (CDP) model was selected for analysis, based on applied loads. Provide the clarification, why the Menetrey-William model was not selected for the analysis.

Response to comment 7:

Dear reviewer, we appreciate your feedback and would like to clarify that when choosing a concrete damage model, the CDP model is often preferred for several reasons:

·         Versatility: Effectively handles various loading scenarios, including monotonic and cyclic loads, making it suitable for diverse structural analysis.

·         Plasticity Framework: It incorporates plasticity theory, allowing for the analysis of permanent deformations and post-peak behavior, which are crucial for structures under heavy loads.

In contrast, the Menetrey-William model is less favored due to:

·         Complexity: It requires more calibration and input parameters, making it less practical for some analyses.

·         Specificity: The model primarily addresses compressive failure and lacks a comprehensive approach for tensile failure compared to the CDP model.

·         Computational Demand: It has higher computational requirements, which can lead to longer analysis times without a significant accuracy benefit for specific applications.

Additionally, the research group's expertise is focused on using the CDP model.

Comment9:

The authors suggested to provide the significance of the differences observed in ultimate load predictions between the models calculated using NBR 6118 and strength class C50? Why is this distinction important in practical applications?

Response to comment 9:

Dear reviewer, we appreciate your feedback and would like to clarify that NBR 6118 provides specific guidelines and safety factors for structural design in Brazil. Differences in ultimate load predictions can affect compliance with these standards, impacting the safety and reliability of structures. Understanding how different models predict performance using this strength class helps ensure that designs accurately reflect the material’s capabilities.

Comment10:

The authors should ensure all figures are high-resolution and properly labelled with proper captions. For example, Figure 8 give only as sensitivity analysis, need to have elaborate captions.

Response to comment 10:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted to improve the resolution of the figures and refine the caption of Figure 8.

Comment11:

The authors are advised to elaborate on the implications of sensitivity analysis findings, especially focusing on the varying impacts of key parameters. Clarify why certain values were more optimal than others.

Response to comment 11:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted. We have added lines 291-293 to the text.

Comment12:

The authors are advised to include a brief explanation of why deviations occurred between numerical and experimental comparisons.

Response to comment 12:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted. We have added this explanation in lines 299-304.

Comment13:

The authors are advised to provide summary of the differences in predictions among various codes and standards before diving into detailed discussions. Reader is getting confusion without an overview.

Response to comment 13:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted. The results mentioned refer to Table 7. Therefore, we have moved this section of the text to before Table 7 (lines 291-298) to improve clarity.

Comment14:

The authors should discuss in detail the types of errors observed between the numerical and experimental results and their potential limitations in the studied carried out for HSC CFST. And furthermore, the manuscript does not address the effects of deformation in CFST columns

Response to comment 14:

Dear reviewer, we appreciate your comment and have improved the discussion about the errors observed. Regarding the effects of deformation, we explain that output data of the numerical model were given in loads and displacements.

Comment15:

The authors as cited some design codes with old version. For instance, update AISC 360 to its most current version, AISC 360-22, suggested to update the version used for the analysis.

Response to comment 15:

Dear reviewer, we appreciate your comment.

This correction was made in the current version.

Comment16:

The authors suggested to condense the conclusion to focus on the key findings, implications, and recommendations for future research. Avoid repeating points from earlier sections.

Response to comment 16:

Dear reviewer, we appreciate your comment and have rewritten the conclusions with these suggestions (lines 396-419).

Reviewer #3:

Comments

Response

General Comments

The paper investigates the accuracy level of existing analytical models for predicting the bearing capacity of concrete-filled steel tubes and proposes an enhanced approach. The authors used the finite element analyses to extend the database of test results within the intended range after validation of the numerical models. In general, the papers present an adequate method and are well-described for investigating the problem. The figures and the text were well-structured and prepared. Based on this, my recommendation is to accept after minor revisions

Dear reviewer, we appreciate your cooperation, and we are extremely grateful. Thank you for reviewing our article. We accepted all comments for correcting the article and believe those suggestions improved the revised manuscript.

Title: 

The title summarizes the content of the paper well.

Comment1:

In the sentence “with a relative error less than 10%.” Change the preposition to “with a relative error of less than 10%

Response to comment 1:

Dear reviewer, we appreciate your comment.

This correction has been made.

Comment2:

Please correct the sentence “An approach coefficient? is proposed.” It sounds a typo mistake.

Response to comment 2:

Dear reviewer, we appreciate your feedback and would like to clarify that it is a typo mistake that has been corrected.

Comment3:

What is the purpose of the proposed approach¿ Please consider linking better this sentence in the abstract.

Response to comment 3:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted. We have added this explanation in lines 21-22.

Comment4:

In the sentence “Additionally, the lateral confinement provided by the tube significantly enhances the column's strength [4]. Therefore, experiments involving short columns with circular sections subjected to axial compression are commonly employed by researchers in the field.” It seems to me that "cause" and "consequences" are not adequately structured in this phrase. Please review.

Response to comment 4:

Dear reviewer, we appreciate your comment.

This correction has been made.

Comment5:

The motivation of the proposed paper is not highlighted based on the presented literature review. Please consider improving the description of the motivation, highlighting the gaps in the literature or the practical relevance of the proposed study.

Response to comment 5:

Dear reviewer, we appreciate your comment, and this suggestion has been adopted. We have added these explanations in lines 100-107 and 142-152.

Comment6:

 In the sentence "The curve described through the presented equations is represented in Fig. 4. model captures the confinement effect through residual stress." It seems to me (I am not sure) that the CDP, using solid elements and the parameters related to the triaxial behavior, should already be capable of considering the confinement effect on concrete without changing the uniaxial behavior. Consider reviewing the literature on this aspect.

Response to comment 6:

Dear reviewer, we appreciate your feedback and would like to clarify that your question is indeed valid; however, we would like to underscore that this model has been designed explicitly for confined concrete applications, as discussed in this reference:

doi: 10.1016/j.jcsr.2013.07.001.

Comment7:

Please, consider citing the reference from Equation 10.

Response to comment 7:

Dear reviewer, we appreciate your comment, and this correction has been made to the reference from Equation 10.

Comment8:

In the sentence “Circular sections are more sensitive to this parameter; for rectangular sections, there is a consensus in the literature that this parameter is 40”. Please, consider citing the references that support this statement.

Response to comment 8:

Dear reviewer, we appreciate your comment, and this correction has been made to the reference in line 291.

Comment9:

Please, improve the description of Table 7. Are the authors showing the ratio between tested and predicted resistances with the Finite Element Models in the Table?

Response to comment 9:

Dear reviewer, we appreciate your feedback. We corrected the title to Table 7.

English writing:

In general, the manuscript is written in good English. Minor revisions on this aspect are sufficient.

Thank you for reviewing our article.

Figures and tables.

In general, most figures were well-prepared by the authors

Thank you for reviewing our article.

Reviewer #1:

Comments

Response

Comment1:
In your response to Comment 1, you mentioned that new references were added to enhance the depth of the literature review. However, the specific studies I recommended in my initial review were not included: “Experimental and Finite Element Method Investigation of Axial Load Carrying Capacity of Concrete Filled Circular Steel Tube Columns According to Different Slenderness Ratios” (https://doi.org/10.1007/s13296-024-00842-7), “Behavior and Reliable Design Methods of Axial Compressed Dune Sand Concrete-Filled Circular Steel Tube Columns” (https://doi.org/10.3390/app14166939), “Axial Compression Behavior and Reliable Design Approach of Rectangular Dune Sand Concrete-Filled Steel Tube Stub Columns” (https://doi.org/10.1016/j.dibe.2024.100437), and “Unified Prediction Models for Mechanical Properties and Stress-Strain Relationship of Dune Sand Concrete” (https://doi.org/10.12989/cac.2023.32.6.595), and “Experimental and numerical study on axial compressive behaviors of reinforced UHPC-CFST composite columns”

 (https://doi.org/10.1016/j.engstruct.2022.115315). Incorporate these specific references into the literature review to provide a more comprehensive context and align the manuscript with recent advancements in the field.

Response to comment 1:

Dear Reviewer,

Thank you for highlighting these valuable references and for your guidance in strengthening the literature review. We appreciate your attention to ensuring the manuscript reflects recent advancements. We apologize for the oversight in including the specific studies you recommended.

Following your suggestion, we have now incorporated each of these references into the literature review to provide a more comprehensive context and align our work more closely with the latest developments in this field.

Comment2:
Figure 9 combines data for both circular and rectangular sections. However, the plot does not differentiate between these section types, making it difficult for readers to interpret the results accurately. It is suggest using distinct markers or labels for each section type to enhance clarity and improve the interpretation of the data.

Response to comment 2:

Dear Reviewer,

Thank you for your thoughtful feedback. We have made the suggested adjustments to Figure 9, adding distinct markers to differentiate between circular and rectangular sections. This change aims to enhance clarity and facilitate the interpretation of the presented results.

Comment3:
The manuscript does not specify the formula used for calculating the relative slenderness ratio (λ) presented in Table 6. Based on standard methods, the slenderness ratio (λ₀) is typically calculated using the formula λ₀ = √(Np/Ncr). Please clarify whether this formula was used and provide the necessary explanation in the text to ensure consistency with the equations outlined in Table 3.

Response to comment 3:

Dear Reviewer,

Thank you for bringing this to our attention. We apologize for the omission. The relative slenderness presented in Table 6 was indeed calculated following the formula D/t or B/t. To ensure clarity and consistency with the equations outlined in Table 3, we have now included an explanation of this calculation in the manuscript.