Survey on the Role of Beam-Column Connections in the Progressive Collapse Resistance of Steel Frame Buildings

Round 1

Reviewer 1 Report

In this study, the role of the connections in the steel frame structure is critically reviewed and the factors that may adversely affect progressive collapse resistance are evaluated. The writing of the paper is good. However, the following issues need to be addressed before the paper is published.

1. This paper is a review article, but it is difficult to see from the title. It is recommended to modify the title.

2.  In introduction section, the author did not clearly articulate the current research issues and the motivation for writing this literature. It is recommended that the author further highlight the motivation for writing this literature.

3.     Please provide literature references for Figures 1, 3 and 4.

4.     In section 3.2, it is very good that the author has commented on the commonly used configurations of test specimens. Some researchers often make unreasonable choices when adopting. Please provide further comments on how to reasonably select substructures, such as when considering joint forms, considering beam weakening or strengthening, considering composite floors, and so on.

5.     In section 4.2, the author comment the pseudo-static response representation of the substructure. Please further clarify the similarities and differences between this method and the dynamic method, as well as the limitations of this method. This is because some scholars currently unreasonably use this method to evaluate the collapse resistance performance of substructures. For example, can this method be used to determine the ultimate displacement of failure, etc.?

6.   In section 5, the author listed some literatures on improving novel approaches. Please further comment on the common characteristics of those literatures and potential future research of on improving the anti-collapse performance of steel frame structures.

7.    The conclusion section is too lengthy, please simplify it.

8.  For double-span substructures, boundary conditions also have a significant influence on their anti-collapse performance. Please supplement the relevant content.

Author Response

See attachment

Author Response File: Author Response.docx

Reviewer 2 Report

1.      Page 1, lines 26-27: “The traditional methods available in current design codes for assessing resistance of building structures to progressive collapse …” the authors are recommended to provide specific/brief details about the traditional methods or the design codes being referred to. This would help the readers to fully understand the extent and limitations of these methods.

2.      The bibliography should be updated with references recently published on the progressive collapse resistance of steel frame structures. The contributions by Xinheng Huang and co-workers, together with the contributions of Sidi Shan and co-workers should also mention.

3.      The study focused on a specific structural idealization by indicating the significance of the double-span beam mechanism in studying the behavior of beam-column connections during progressive collapse. However, I recommend the authors to provide a brief justification for why this specific mechanism was chosen and how it contributes to the overall understanding of progressive collapse resistance.

4.      The authors are also recommended to clearly stating the scope and objectives of the study in the introduction section as they mentioned that (page 2 lines 68-69) the main characteristics of connection behavior in progressive collapse are identified. However, it does not explicitly state what these characteristics are, leaving the reader without a clear understanding of what will be evaluated in the subsequent analysis.

5.      The authors are recommended to provide further discussion regarding the simplified idealizations employed in the column removal approach for assessing the response of frame structures. The impact of these simplifications on the accuracy and reliability of the analysis should be thoroughly discussed.

6.      I agree with the authors' recognition of the significance of simulating the interaction with the surrounding structure through appropriate boundary conditions. However, critical assessment of the challenges and limitations associated with accurately modeling these boundary conditions should be further discussed. Furthermore, the authors suggests that the stability of the remaining columns may not be a critical factor for the overall structural resistance. However, to strengthen this assertion, the basis for this statement should be explained, and supporting evidence should be provided to enhance the credibility of the argument.

7.      Regarding the simplified idealizations employed in the column removal approach, the authors propose the concept of a grillage structure and suggests that each beam system can be analyzed individually by ignoring the contribution of the slab. However, However, the potential consequences of disregarding the slab's role in the overall behavior and load distribution of the structure are not addressed. The authors should consider discussing the implications and limitations of this simplification.

8.      In section 5: the authors indicated that the failure of frame systems with reduced beam sections is typically triggered by fracture of the beam tension flanges. I suggest that authors may underline the causes and factors contributing to flange fracture and also it would be valuable to discuss the limitations of reduced beam sections and their potential impact on structural behavior and performance.

Author Response

See attachment 

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript presents a survey focusing on the role of steel beam-column connections in progressive collapse scenarios. The topic is highly intriguing as, thus far, no comprehensive review has been dedicated to this subject. Overall, the manuscript is well-written, and the subject matter aligns with the scope of the journal. However, there are several points that need to be addressed attentively before considering it for publication.

1.    Please revise the manuscript to ensure that the concept of "structural robustness" is more prominently addressed. Although the keyword "structural robustness" is listed, it is currently not mentioned in the abstract or emphasized sufficiently throughout the text.

2.    If Figure 1 has been adopted from Izzuddin et al. [20], it is crucial to provide a proper citation for it. Please ensure that the manuscript includes appropriate references to acknowledge the source of the figures.

3.    Dynamic progressive collapse tests and simulations (sudden column removal) are becoming very popular these days. Such studies usually have some focus on the connections behavior too. However, such studies did not receive enough attentions in the current manuscript. Please update the manuscript accordingly.

4.    It is crucial to consider that primary designs typically prioritize gravity and seismic design rather than extreme loading conditions. Therefore, it is essential to ensure that any progressive collapse-resisting connections are also consistent with the seismic design requirements. This significant issue should be discussed somewhere within the manuscript. The following reference can be consulted to provide further insights on this topic;
https://doi.org/10.1016/j.engstruct.2022.114274   

5.    The manuscript appears to aim to provide a comprehensive review of the role of beam-column connections in progressive collapse scenarios. However, upon considering the manuscript's structure and cited references, it seems that the emphasis is predominantly placed on experimental studies. If the main focus of the manuscript is to review the experimental literature, it would be appropriate to reflect this in the title and abstract. On the other hand, if the goal is to encompass a broader range of studies, it would be beneficial to enrich the manuscript by incorporating numerical studies as well. In such a case, several relevant studies can be found in the aforementioned review paper, which can serve as a valuable resource.

6.    To provide a more comprehensive view of the topic, it is necessary to place greater emphasis on the general aspects of progressive collapse at the beginning of the manuscript. This will help establish a solid foundation and context for the subsequent discussions. Please ensure that the manuscript incorporates a more focused and thorough exploration of the general aspects of progressive collapse.

7.    Given the current popularity of techniques that enhance both progressive collapse resistance and seismic performance, it is essential to explicitly focus on these aspects within the manuscript. These techniques have garnered significant attention and should be given due consideration in the discussions. Please ensure that the manuscript explicitly addresses these techniques and highlights their relevance and significance in enhancing both progressive collapse resistance and seismic performance. The following papers can be consulted;
https://doi.org/10.1016/j.engstruct.2019.02.006   
https://doi.org/10.1016/j.soildyn.2020.106370
       
8.    It is important to note that a review paper is more than just a collection of categorized literature. It should also provide valuable insights into future needs and research directions. The main aim of a review paper is to highlight research gaps and limitations, providing guidance for future researchers. The current manuscript lacks in this area as it does not explicitly address future needs. To address this issue, it is recommended to update and enrich the manuscript by either adding a new section or enhancing Section 6. This will allow for a more comprehensive discussion on the research gaps and limitations, providing valuable insights for future studies in the field.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The author have addressed all the comments from the origin review.

Reviewer 3 Report

The manuscript is sufficiently improved to justify acceptance.