Knowledge-Based Investigation of Seismic Vulnerability Assessment and Compatible Strengthening Design of an Existing Masonry Building

Round 1

Reviewer 1 Report

This paper deals with seismic vulnerability assessment and compatible strengthening design of an existing masonry building, but it does not make any contribution to new knowledge in the discipline or the application of the knowledge. The manuscript does not address any (significant) research question; the analysis is weak and at an early stage to make the publication of the study meaningful. In its present form, the paper cannot compete with the high quality of other papers submitted to the Journal.

Author Response

Rewiever 1

Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	(x)	( )	( )	( )
Are all the cited references relevant to the research?	(x)	( )	( )	( )
Is the research design appropriate?	(x)	( )	( )	( )
Are the methods adequately described?	( )	( )	(x)	( )
Are the results clearly presented?	( )	( )	(x)	( )
Are the conclusions supported by the results?	( )	( )	(x)	( )

Comments and Suggestions for Authors

This paper deals with seismic vulnerability assessment and compatible strengthening design of an existing masonry building, but it does not make any contribution to new knowledge in the discipline or the application of the knowledge. The manuscript does not address any (significant) research question; the analysis is weak and at an early stage to make the publication of the study meaningful. In its present form, the paper cannot compete with the high quality of other papers submitted to the Journal.

The authors thank the reviewer for the comments. The work has been revised based on the different comments pointed out during the revision process. The text has been implemented and the manuscript has been improved for publication.

Author Response File: Author Response.docx

Reviewer 2 Report

Please see the attachment.

Comments for author File: Comments.pdf

Author Response

Rewiever 2

Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	( )	(x)	( )
Are all the cited references relevant to the research?	( )	( )	(x)	( )
Is the research design appropriate?	( )	( )	(x)	( )
Are the methods adequately described?	( )	( )	(x)	( )
Are the results clearly presented?	( )	( )	(x)	( )
Are the conclusions supported by the results?	( )	( )	(x)	( )

Comments and Suggestions for Authors

Please see the attachment.

This is a well written paper targeted the issues of strengthening masonry structures. This paper is written in simply understandable language, tables and figures. State of the art is suitably presented; the research method is well explained and supported by a real case study implementation. However, there are significant issues to be responded and rectified. Therefore, this paper earns the recommendation to be published when the following comments are addressed.

The authors thank the reviewer for the comments. The work has been revised based on the different comments pointed out during the revision process. The text has been implemented and the manuscript has been improved for publication.

 

1. Abstract could be improved. It is suggested to highlight the aim or purpose and content of the study clearly with defining the novelty of this study. It is also suggested to present some quantitative conclusions and statistical data in the abstract.

The abstract has been revised

2. The article's introduction section deals with the importance of research, whereas the literature review in this field of study is ignored. The issues or challenges with construction and strengthening of masonry structures needs to be addressed comprehensively compared to any other conventional methods. Furthermore, the references given in this section need to be strengthened. The literature review should be updated adding more recently published papers related to your study.

A literature review concerning the strengthening solutions for masonry buildings has been added to the text.

3. It is better to insert a paragraph of highlighting the limitations and challenges of the study.

A general review of the introduction has been done. The revised version of the section set the contributions of the manuscript within a line of research addressed at evaluating not only the critical aspects of the confidence factors and the knowledge levels but in particular the potential strengthening solutions consequent to these levels.

4. Justify your selection of case study (the project selection criteria) for this study and explain the reliability of the results using just one study. Or support your selection by referring to the literatures. Is there a source stating that a building’s performance may be judged based on its utility and applicability?

As implemented in the introduction, the building represents a standard regular masonry construction with architectural features similar to many other structures addressed at schools of representative palaces all over Italy. Therefore, the authors believe it may be a representative construction of a series of medium-size buildings presenting common characteristics. Further comments have been added in the conclusions of the manuscript, setting the contribution of this paper within a more comprehensive research on the current knowledge levels defined according to national and international codes.

5. This paper has been analyzed from several points with case study. However, the final integration instructions still need to be included. Conclusion section must explain how the purpose is achieved by the study and if possible add the main findings in bullet points.

Conclusions have been revised with the main findings in bullet points. The research has been framed within a more general research on the effects of achieving different knowledge levels to the proposal of strengthening interventions.

6. In the conclusion section, future directions and limitations are not covered.

This part has been added in the text.

7. Since you have added lots of notations in the manuscript, better to add them as nomenclature. It is essential to introduce every acronym before using it in the text. For the first time, put the acronym in parentheses after the full term. There is an instance in the section 2 when the acronym RSA and RC are introduced without being defined first. (Line 92,93 in page 2)

Nomenclatures have been added to the text. Also the acronyms have been defined every first time.

8. Authors should have a look on formatting the paper structure throughout the paper. Eg. Figure axis names and numbering, usage of same font for figures, have consistent spacing between lines, and sections. (Figures could have been added as 1(a); 1(b) etc. rather using on the left and right, Grpah axis are not defined)

Figures and tables have been formatted according to the Journal style

9. Authors must consider improving the language and read the article properly for tense consistency.

A general review of the English of the manuscript has been done

Author Response File: Author Response.docx

Reviewer 3 Report

The submitted manuscript is an interesting work, with practical values and treats present issues of modeling and structural analyzing of existing masonry structures.

There are some drawbacks of the current manuscript, which is very localized in the context of Italian practice. Here by I do not only to highlight the case study, but even as a practice of how is proceeded in such cases. Taken out of this context, it is very difficult to highlight the benefits that this article could provide to the scientific community.

-          The literature review is very poor.

-          Explain all the abbreviations.

-          Regarding the numerical approach, the macroelements do not represent the most advanced approach, however, the authors should highlight that the context of the research is based on the Italian code of practice. Thenceforth, the numerical method suitable for structural verification is the one based on a macroelement behavior of the masonry. It is essential to better highlight this main axis of investigation, conformity with the Italian guideline of existing masonry structures.

-          It is important to represent the most relevant simulations and results. The authors have used different approaches to simulation thenceforth could be interesting to see the most relevant results, especially when it is noted a difference between different approaches.

-          Is it considered the single brick wall as a structural wall, resisting lateral loads? Generally speaking, it is not recommended to be considered. In any case, should be justified.

-          After section 3, there is confusion in the organization of the information. It looks like the authors have shortened to much their text.

-          Section 3. Compatible strengthening interventions is very generalistic, do not reflect the solutions for the considered case study. More insight of the retrofitting solutions is required, especially for the different levels of knowledge. The author's considerations are very superficial. Generally speaking, the concept transmitted is similar to: “by increasing the knowledge level, we decrease the confidence factor and respectively the mechanical properties are higher, thenceforth, it is trivial to obtain a safer structure. However, more aspects should be considered during modeling, and generally speaking, the overall approach is very simplistic. To be precise, should not be expected a linear correlation because the solution of the problem would be very trivial (banal) ”

-          Why are the reduction coefficients considered only for the KL2 case?

-          The mechanical properties from the experimental campaign should be better elaborated and presented.

-          The conclusion parts do not present essential information.

-          What does it mean that: “based on the bad performances of the mortar, the increasing of the knowledge acquisition does not correspond to an increase of the seismic performances”? Worth highlighting that the applied approaches do not correlate the mechanical properties of the mortar with the mechanical properties of the masonry, while the seismic performance is correlated to the mechanical properties of the masonry.

-         Is the structure a modern masonry structure or an existing masonry structure? What's the difference?

Author Response

Rewiever 3

Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	( )	(x)	( )
Are all the cited references relevant to the research?	( )	( )	(x)	( )
Is the research design appropriate?	( )	( )	(x)	( )
Are the methods adequately described?	( )	( )	(x)	( )
Are the results clearly presented?	( )	( )	(x)	( )
Are the conclusions supported by the results?	( )	( )	(x)	( )

Comments and Suggestions for Authors

The submitted manuscript is an interesting work, with practical values and treats present issues of modeling and structural analyzing of existing masonry structures.

The authors thank the reviewer for the comments. The work has been revised based on the different comments pointed out during the revision process. The text has been implemented and the manuscript has been improved for publication.

There are some drawbacks of the current manuscript, which is very localized in the context of Italian practice. Here by I do not only to highlight the case study, but even as a practice of how is proceeded in such cases. Taken out of this context, it is very difficult to highlight the benefits that this article could provide to the scientific community.

To the authors’ opinion, the procedures to investigate the existing structures are internationally recognized, as they are available not only in the Italian code but still in the European EC8-3 and FEMA 356. Furthermore, the Italian code is often applied in different areas of the world outside the Italian peninsula because of its advances in the evaluation of the existing constructions (e.g. doi:10.1016/j.engstruct.2019.110050). Hence, we believe that some benefits for the worldwide scientific community in the practice-oriented assessment of construction can be highlighted by this contribution. The research conducted in this paper is a first application to a case study to investigate the effects of different knowledge levels to masonry constructions. Not only to determine the structural capacity of a building, but especially to propose suitable strengthening interventions. The authors believe that, although the structural specificities of the construction, the investigated case study may be a representative medium-size building as many other representative palaces located in Italy (e.g. municipalities, schools). The manuscript has been implemented in the introduction and the conclusions in order to highlight this aspect. In addition, it has been set within a more comprehensive research where further analyses on different case studies and evaluating multiple configurations will be proposed.

-          The literature review is very poor.

Literature has been improved

-          Explain all the abbreviations.

The abbreviations have been clarified in the text

-          Regarding the numerical approach, the macroelements do not represent the most advanced approach, however, the authors should highlight that the context of the research is based on the Italian code of practice. Thenceforth, the numerical method suitable for structural verification is the one based on a macroelement behavior of the masonry. It is essential to better highlight this main axis of investigation, conformity with the Italian guideline of existing masonry structures.

In the text, the following explation has been added to the text:

“Both strategies follow a phenomenological approach where the masonry is discretized according to the experienced damage of the bearing walls. The equivalent frame is conceived for the in-plane behavior of structures, discretizing the masonry panels be-tween piers, spandrels and rigid nodes; this approach been validated by the contribu-tion of different authors especially in case of regular constructions (Marques and Lourenço 1998, Cattari et al. 2017, Siano et al. 2018; Aşıkoğlu et al. 2020, Valluzzi et al. 2021). Concerning the macroelement approach, the latter follows the assumption that masonry panels behave as rigid block connected through kinematic chains. Although the more of less refined available procedures, the methodology is a reliable approach to investigate the structural performance of masonry constructions when structural of historical discontinuities are pointed out (Gilbert et al. 2006, Lagomarsino 2014, Ferreira et al. 2015, Giordano et al. 2020, Grillanda et al. 2020, Cardinali et al. 2021).”

-          It is important to represent the most relevant simulations and results. The authors have used different approaches to simulation thenceforth could be interesting to see the most relevant results, especially when it is noted a difference between different approaches.

In the work two approaches have been used, targeted at evaluating two complementary behaviors of a masonry construction: the out-of-plane and the in-plane ones. Of course, considering an univocal construction, the two approaches are alternative, as they investigate reciprocal possibilities. The two methods have been adopted in order to extensively assess the structural performance of the construction. In fact, the uncertainty in the selection of the most suitable approach to investigate a building is given by the lack of knowledge of the investigator, which is not able to determine the real grade of connection between the structural elements of a masonry building. Nevertheless, the research has pointed out that both approaches indicate poor capacities of the structure. Hence, this allows obtaining a general appraisal on the construction and its performance under seismic motion.

-          Is it considered the single brick wall as a structural wall, resisting lateral loads? Generally speaking, it is not recommended to be considered. In any case, should be justified.

These walls have been considered as in some part of the building they constitute the only bearing walls inside the construction. The slabs gravitate on them, and they are full-fledged part of the structural system of the construction. This way of realizing the internal bearing panels with a single-brick layer is typical from the Tuscany region, although it nowadays represents a weak point both for vertical as for seismic verifications.

In section 2.2 the following sentence has been added: “The internal structural walls are made of one single brick layer, leading to particularly slender panels.”

-          After section 3, there is confusion in the organization of the information. It looks like the authors have shortened to much their text.

The text is a ex-novo text and it has not been shortened. Further information have been added concerning the strengthening results on the case study.

-          Section 3. Compatible strengthening interventions is very generalistic, do not reflect the solutions for the considered case study. More insight of the retrofitting solutions is required, especially for the different levels of knowledge. The author's considerations are very superficial. Generally speaking, the concept transmitted is similar to: “by increasing the knowledge level, we decrease the confidence factor and respectively the mechanical properties are higher, thenceforth, it is trivial to obtain a safer structure. However, more aspects should be considered during modeling, and generally speaking, the overall approach is very simplistic. To be precise, should not be expected a linear correlation because the solution of the problem would be very trivial (banal) ”

The main targeted of the research is to assess the proposal of strengthening interventions on the basis of different knowledge levels. A further flowchart explaining the aimed procedure has been added to the text. in the text we evaluate the proposal of strengthening solution that could be follow the achievement of KL1 and KL2. In particular for KL1, the absence of specific information determines that the sensibility of the technician is the aspect that can orient toward effective or ineffective strategies. In the text we analytically compute a solution following this consideration. On the other side, based on the bad mortar qualities, the achievement of KL2 would address towards suitable solutions. These conclusions can point out general outcomes extendable to other case studies. However, further information have been provided in the introduction and conclusion of the work including these research within a more wide research framework where other studies will follow

-          Why are the reduction coefficients considered only for the KL2 case?

The reduction coefficients have been considered for KL2 and for KL3. This is specified in section 2.3 Seismic vulnerability assessment and multilevel evaluation: “In the computation, due to the outcomes of the mortar characterization, the det-rimental coefficient equal to 0.80 for the elastic moduli and 0.70 for the resistances have been applied, in order to consider on the effects of the bad mortar qualities.”

Later, doing the stepback evaluations on the possible assessment based on lower KLs, the detrimental coefficients have been applied for KL2 but not for KL1.

-          The mechanical properties from the experimental campaign should be better elaborated and presented.

The authors avoided specific presentations of the different conducted experimental campaigns as they do not constitute the central topic of the article. Further information have been provided concerning the double flat-jack tests and the uni-axial compressive tests on the clay elements. Two additional figures have been inserted in the text

-          The conclusion parts do not present essential information.

The conclusion has been revised

-          What does it mean that: “based on the bad performances of the mortar, the increasing of the knowledge acquisition does not correspond to an increase of the seismic performances”? Worth highlighting that the applied approaches do not correlate the mechanical properties of the mortar with the mechanical properties of the masonry, while the seismic performance is correlated to the mechanical properties of the masonry.

As explained in the following part of the sentence, this mean that although the confidence factors adopted during the different knowledge levels are reduced, the poor mechanical values of the building decrease from an other side the features to be adopted for the analysis. “since the effects of the confidence factors is mitigated by the poor mechanical properties of the masonry typologies.”

The bad capacity of the mortar has been considered in the characterization of the masonry panels adopting the detrimental coefficients 0.8 for the elastic moduli and 0.70 for the resistances.

-         Is the structure a modern masonry structure or an existing masonry structure? What's the difference?

Modern is referred in architectural way, to recall the historical period of the Modern movement, which has started in the first decades of the XIX century (20-30’s up to the 50’s). As a building has been realized in that time, it can be considered an existing structure as well.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Paper has been revised according to the comments provided. Therefore it may be considered for the publication.

Author Response

The authors thank the reviewer for the comments.

Reviewer 2 Report

It could be seen that most if the comments given were addressed. However, the discussion and conclusion parts could be improved.

Author Response

The authors thank the reviewer for the comments. The work has been revised based on the comment pointed out during the revision. The text has been implemented and the manuscript has been improved for publication.

Reviewer 3 Report

The authors have addressed all the raised comments.

The article is publishable in the revised form.

Author Response

The authors thank the reviewer for the comments.