Architectural, Constructional and Structural Analysis of a Historic School Building in the Municipality of Agia, Greece

Round 1

Reviewer 1 Report

In this paper a case study, an existing school building in Greece, is analyzed from architectural, constructional and structural point of view.

In general, the paper is well structured and there are some valuable aspects. Therefore, it is opinion of the Reviewer that it may be considered for the publication. However, a revision should be made according to the following comments.

 

Point 1. Recently multi-level approaches for seismic assessment of several types of masonry  existing structures have been published in literature. This aspect should be at least mentioned in in the introduction. Among the others, please consider the following works:

 

·       D'Amato, M.; Gigliotti, R.; Laguardia, R. Comparative Seismic Assessment of Ancient Masonry Churches. Frontiers in Built Environ- 569 ment, 5, 2019. doi:10.3389/fbuil.2019.00056

·       Lourenço, P. B., and Roque, J. A. (2006). Simplified indexes for the seismic vulnerability of ancient masonry buildings. Construct. Build. Mater. 20, 200–208. doi: 10.1016/j.conbuildmat.2005.08.027

 

 

Point 2. Reviewer does not understand from where the table 2 values were taken. Which NDTs were done? Please better specify this.

 

Point 3. Quality of figure 9-12 should be improved. In addition, Reviewer suggests of improving the readability of the figure 10 (may be a transparency should be adopted). Authors use terms ‘eigenperiod’ and ‘eigenmode’. It should be more appropriate to use the terms periods and mode shape.

 

 Point 4. Truly speaking, a seismic assessment is missing within the paper. Authors just report some results of a stress analysis (Figure 11 and Figure 12, check the caption). Therefore, Reviewer suggest of improving this part, better commenting the results considering the seismic demand assumed (missing in the paper).

 

Point 5. What is the correlation among architectural, constructional and structural analysis conducted in this study? How the knowledge level achieved influences the results obtained? This aspect should be commented in the paper for boosting the work within the scientific literature.

 

Point 6. Conclusions should be revised reporting just the main outcomes of the work presented.

 

Point 7. English revision should be made.

Author Response

With the present we would like to thank the reviewers for their fruitful comments on the present article. All questions/comments/suggestions were carefully studied and taken into account by the authors. The corresponding answers are located underneath each reviewer’s comment and all the changes are highlighted in the body text, including the references.

However, since the majority of the comments referred to the finite element modeling and its application to the structural assessment of the building, the authors should have clarified some corresponding issues. Therefore, the following paragraph(s), which is included in the body, clarifies a major misunderstanding and substantiates some of the most important assumptions of the study.

The primary steps of any structural assessment studies refer to the investigation and documentation of the existing structure in extent and in depth as well, in order to ensure the reliability of the data on which any further analysis will be based. Therefore, the following tasks must be accomplished: (i) detailed architectural drawings; (ii) description of the building’s history and possible previous interventions; (iii) investigation of interconnections between walls; (iv) detailed description of the structural bearing system; (v) description of the present state including pathology issues; (vi) conduction of in situ and laboratory experiments in order to determine type/strength of materials, etc.; (vii) investigation of foundation and subsoil type. Referring to the present study, taking into account the limited financial and technical means available at the present state, the structural assessment is restricted in the detection of the most vulnerable areas of the masonry building under persistent and seismic loading conditions. In addition to the aforementioned, KADET 2022-draft (see reference below) recommends a preliminary structural analysis in order to: (i) detect the most vulnerable zones; and (ii) define the possible failure modes. The results will enable the design of a targeted program of investigational surveys.

Furthermore, the very good present state of the masonry buildings, which is documented by the absence of cracks in the masonry body, enables the assumption of a linear analysis.

Therefore, the structural assessment is fulfilled in terms of exceedance of masonry strength at certain points/nodes, corresponding to the vulnerable areas of the structure.

KADET 2022, Draft – “Regulation for valuation and structural interventions of masonry”, Greek Organization of Earthquake Design and Protection (OASP).

 

Reviewer #1

Comments and Suggestions for Authors

In this paper a case study, an existing school building in Greece, is analyzed from architectural, constructional and structural point of view.

In general, the paper is well structured and there are some valuable aspects. Therefore, it is opinion of the Reviewer that it may be considered for the publication. However, a revision should be made according to the following comments.

The authors would like to deeply thank Reviewer #1, for the review of the manuscript, positive and encouranging comments, as well as all suggestions aiming at its improvement. All comments were taken into account and relevant revision was made, highlighted with red color in the text.

 

Point 1. Recently multi-level approaches for seismic assessment of several types of masonry  existing structures have been published in literature. This aspect should be at least mentioned in in the introduction. Among the others, please consider the following works:

• D'Amato, M.; Gigliotti, R.; Laguardia, R. Comparative Seismic Assessment of Ancient Masonry Churches. Frontiers in Built Environ- 569 ment, 5, 2019. doi:10.3389/fbuil.2019.00056
• Lourenço, P. B., and Roque, J. A. (2006). Simplified indexes for the seismic vulnerability of ancient masonry buildings. Construct. Build. Mater. 20, 200–208. doi: 10.1016/j.conbuildmat.2005.08.027

The reviewer is correct. All the aforementioned references regard seismic assesment studies  that should have been included in the referenced literature. The reviewer’s recommendation was carefully taken into account and therefore, the  two proposed references were included in Section 2.

 Point 2. Reviewer does not understand from where the table 2 values were taken. Which NDTs were done? Please better specify this.

 As reported in section 2 Materials and Methods, ‘…Schmidt hammer rebound testing was applied for estimating the materials’ strength, as well as profometer measurements, for detecting the existence of reinforcement in concrete elements.’ The results from the Schmidt hammer test were documented in a clearer way in lines 305-319, while Table 2 with the corresponding values was added.

Point 3. Quality of figure 9-12 should be improved. In addition, Reviewer suggests of improving the readability of the figure 10 (may be a transparency should be adopted).

The quality of figures depicting deformed shapes and stresses has been improved as suggested by the reviewer.

Authors use terms ‘eigenperiod’ and ‘eigenmode’. It should be more appropriate to use the terms periods and mode shape.

 According to the authors’ point of view the term period is a general term that may refer to excitation period or natural period of vibration. Therefore, the second term is used in the revised text. Furthermore, the term eigenmode has been changed to mode shape, according to the review’s suggestion.

 Point 4. Truly speaking, a seismic assessment is missing within the paper. Authors just report some results of a stress analysis (Figure 11 and Figure 12, check the caption). Therefore, Reviewer suggest of improving this part, better commenting the results considering the seismic demand assumed (missing in the paper).

 The reviewer is correct. The seismic structural assessment in terms of forces or deformations must be a comparison between developed variables and corresponding limit values. However, as mentioned in the common to all reviewers authors’ response paragraph and as it has been highlighted in the revised manuscript, structural assessment in general was not the main scope of the present study. Therefore, stress exceedance can be considered as a quick criterion to detect the most vulnerable zones of the building.

Point 5. What is the correlation among architectural, constructional and structural analysis conducted in this study? How the knowledge level achieved influences the results obtained? This aspect should be commented in the paper for boosting the work within the scientific literature.

 The correlation reported was assessed in detail in a new subsection added, entitled as 3.3. General remarks.

Point 6. Conclusions should be revised reporting just the main outcomes of the work presented.

 Conclusions were accordingly revised.

Point 7. English revision should be made.

Extensive english revision was conducted in the whole manuscript

 

Reviewer 2 Report

The submitted manuscript presents a multidisciplinary study, considering architectural aspects, state of conservation material and construction investigation, and numerical analysis.

Generally speaking, the case study could be interesting however the organization of the text and the research is not adequate. The most notable is the lack of an adequate terminology, particularly related to the structural analysis aspects. The scientific soundness is very poor.

1-      Regarding the material properties, the provided information should be more accurate. Normally, either is referred to the literature or normative recommendations of the mechanical properties, or an advanced set of tests is performed. Schmidt hammer rebound testing results is for homogeneous like material, and in my knowledge, is not prescribed for masonry material as a recommended test.

2-      The soil-structure interaction is not very clear. There are some aspects that the provided information leads to a wrong model. For modal analysis, it is recommended to have fixed restraints. Spring-like interaction is recommended for full nonlinear dynamic analysis, in this case, it is also mimicked the lack of tensile strength of the soil.

3-      The description of the model is not very clear. The images should be more clear and should be accompanied with legends. What does the colors express, different materials or different sections?

4-      Te authors have provided some masonry strength capacities, in compression, tension and shear. Those properties are required during the masonry material definition and assignment. Generally speaking, in all the present literature, a similar verification approach is not prescribed. The authors should have an insight into the literature related to this topic. The authors should provide in their revised version strength capacity checks, based on an equivalent frame model, or for more advanced simulations in the nonlinear phase, I suggest implementing more advanced approaches. Find below the most advanced literature that have properly implemented masonry structures/ materials using SAP2000.

5-      The authors have paid very little attention on the seismic hazard. They do refer that the most dangerous case is the vertical component. At present, it is not very clear and should be further elaborated.

6-      Regarding the modal analysis, 300 modes mean that the model is very complex and could have many flaws. This model could lead to wrong estimation of the seismic loads. The authors should review their model, and implement Ritz frequency analysis, limiting the number of modes by maintaining the same level of accumulated mass.

7-      The authors should provide a confrontation with limit deformations related to the deformation results.

8-      The literature is very poor. It results in two aspects: 1- some relevant research articles are not mentioned; 2- the research structure, approach and obtained results are far from a common approach consolidated in the past decades. For these two aspects, I recommend:

10.1016/j.istruc.2018.06.004

10.1016/j.conbuildmat.2017.04.075

10.1016/j.engstruct.2014.01.031

10.1016/j.jobe.2017.03.004

10.1007/s10518-019-00603-6

10.1016/j.compstruc.2016.07.005

10.1016/j.conbuildmat.2011.08.046

10.1080/15583058.2020.1805045

10.1007/s11831-019-09351-x

10.1193/022512EQS053M

 

Author Response

With the present we would like to thank the reviewers for their fruitful comments on the present article. All questions/comments/suggestions were carefully studied and taken into account by the authors. The corresponding answers are located underneath each reviewer’s comment and all the changes are highlighted in the body text, including the references.

However, since the majority of the comments referred to the finite element modeling and its application to the structural assessment of the building, the authors should have clarified some corresponding issues. Therefore, the following paragraph(s), which is included in the body, clarifies a major misunderstanding and substantiates some of the most important assumptions of the study.

The primary steps of any structural assessment studies refer to the investigation and documentation of the existing structure in extent and in depth as well, in order to ensure the reliability of the data on which any further analysis will be based. Therefore, the following tasks must be accomplished: (i) detailed architectural drawings; (ii) description of the building’s history and possible previous interventions; (iii) investigation of interconnections between walls; (iv) detailed description of the structural bearing system; (v) description of the present state including pathology issues; (vi) conduction of in situ and laboratory experiments in order to determine type/strength of materials, etc.; (vii) investigation of foundation and subsoil type. Referring to the present study, taking into account the limited financial and technical means available at the present state, the structural assessment is restricted in the detection of the most vulnerable areas of the masonry building under persistent and seismic loading conditions. In addition to the aforementioned, KADET 2022-draft (see reference below) recommends a preliminary structural analysis in order to: (i) detect the most vulnerable zones; and (ii) define the possible failure modes. The results will enable the design of a targeted program of investigational surveys.

Furthermore, the very good present state of the masonry buildings, which is documented by the absence of cracks in the masonry body, enables the assumption of a linear analysis.

Therefore, the structural assessment is fulfilled in terms of exceedance of masonry strength at certain points/nodes, corresponding to the vulnerable areas of the structure.

KADET 2022, Draft – “Regulation for valuation and structural interventions of masonry”, Greek Organization of Earthquake Design and Protection (OASP).

Reviewer #2

The submitted manuscript presents a multidisciplinary study, considering architectural aspects, state of conservation material and construction investigation, and numerical analysis.

Generally speaking, the case study could be interesting however the organization of the text and the research is not adequate. The most notable is the lack of an adequate terminology, particularly related to the structural analysis aspects. The scientific soundness is very poor.

The authors would like to thank Reviewer #2, for the review of the manuscript, as well as all suggestions aiming at its improvement. All comments were taken into account and relevant revision was made, highlighted with red color in the text.

 

1-      Regarding the material properties, the provided information should be more accurate. Normally, either is referred to the literature or normative recommendations of the mechanical properties, or an advanced set of tests is performed. Schmidt hammer rebound testing results is for homogeneous like material, and in my knowledge, is not prescribed for masonry material as a recommended test.

The results from the Schmidt hammer test were documented in a clearer way in lines 331-345, while Table 2 with the corresponding values was added.

2-      The soil-structure interaction is not very clear. There are some aspects that the provided information leads to a wrong model.

A detailed paragraph concerning soil-structure interaction, accompanied by the corresponding references, has been inserted in Section 3.2.3.

For modal analysis, it is recommended to have fixed restraints.

The present case refers to plates resting on soil surface. Furthermore, the plate acts also as a foundation. However, the foundation is not buried in soil and therefore, it cannot be considered as fixed. All the other structural elements, such as walls and pillars have been considered as fixed. In conclusion, the modal analysis was conducted by taking into account, two boundary conditions: (i) flexible based plates; and (ii) fixed base vertical structural elements.

Spring-like interaction is recommended for full nonlinear dynamic analysis, in this case, it is also mimicked the lack of tensile strength of the soil.

The reviewer is correct. Full nonlinear static or dynamic analysis should take into account nonlinear masonry material behavior and nonlinear behavior of spring-like interaction. Especially, for the second case, a proper way to consider the nonlinearity is to restrict the development of tensile stresses. The authors are familiar with the aforementioned modeling, since it has been applied in a far more elaborated finite element model of previous studies [Terzi 2022, Terzi and Ignatakis 2022]. However, in the present case, the very good preservation state of the masonry building (no wall cracks, no foundation’s settlements), allows the assumption of linear behavior.

Terzi V. Investigation of the pathology causes of Xana, Greece by the use of nonlinear finite element analyses. I. Vayas and F. M. Mazzolani (Eds.): PROHITECH 2021, LNCE 209 2022, 369–388. https://doi.org/10.1007/978-3-030-90788-4_31

Terzi G.V.; Ignatakis E.G. Nonlinear finite element analyses for the restoration study of Xana, Greece. Engineering Structures 2018, 167, 96-107. https://doi.org/10.1016/j.engstruct.2018.04.034.

3-      The description of the model is not very clear. The images should be more clear and should be accompanied with legends. What does the colors express, different materials or different sections?

Figure 9 was elaborated and a new detailed version is provided in the body text, including coloring description and specific heights of structure.

4-      The authors have provided some masonry strength capacities, in compression, tension and shear. Those properties are required during the masonry material definition and assignment. Generally speaking, in all the present literature, a similar verification approach is not prescribed. The authors should have an insight into the literature related to this topic. The authors should provide in their revised version strength capacity checks, based on an equivalent frame model, or for more advanced simulations in the nonlinear phase, I suggest implementing more advanced approaches. Find below the most advanced literature that have properly implemented masonry structures/ materials using SAP2000.

The reviewer is correct regarding the structural assessment approach that should be applied in masonry buildings. However, the detection of the most vulnerable zones can be achieved in a preliminary stage by comparing the developed stresses to corresponding strength values. Furthemore, the assumption of elastic linear material has been explained in detail in the revised manuscript.

5-      The authors have paid very little attention on the seismic hazard. They do refer that the most dangerous case is the vertical component. At present, it is not very clear and should be further elaborated.

An additional paragraph can be found in the revised manuscript version, which is dedicated to the research studies, numerical and experimental, that refer to the vertical ground component.

6-      Regarding the modal analysis, 300 modes mean that the model is very complex and could have many flaws. This model could lead to wrong estimation of the seismic loads. The authors should review their model, and implement Ritz frequency analysis, limiting the number of modes by maintaining the same level of accumulated mass.

The reviewer is correct. Modal analysis in SAP2000 can be conducted by two dinstict methods: (i) Eigenvector analysis; and (ii) Ritz-vector analysis. The first one determines the undamped free-vibration mode shapes and the corresponding frequencies whether the second seeks to detect modes that are excited by a particular loading. Furthermore, Ritz-vector analysis offers the following important advantages: (i) provides a better than Eigenvectors basis for response-spectrum analysis; and (ii) is most suitable for analyses involving vertical ground acceleration; (iii) converges much faster than Eigenvectors do.

Therefore, the authors have conducted a Ritz-vector analysis, without any changes in the finite element model. Both types of analysis produced the same results not only in terms of modal analyses results but also in terms or stresses in response spectrum analyses. The following figures depicts the accumulative modal participating mass ratios for the two types of modal analyses.

In addition, one basic comment is that no time reduction was observed during solution phase. Both analyses yielded results in almost the same, relatively fast, time interval.

Furthermore, the large number of modes does not necessarily means a complex or a model with flaws. The aforementioned is attributed to the total number of shell elements ( 7,617) and corresponding nodes (8,548), at which the inertial degrees of freedom are activated.

7-      The authors should provide a confrontation with limit deformations related to the deformation results.

The reviewer is correct. Limit deformations related to deformation results must be studied during structural assesment. However, as mentioned, the main scope of the present study was the detection of the most vulnerable zones of the building. Furthermore, the resultant displacement of 1.728 mm as depicted in Fig.14 corresponds to a small value.

8-      The literature is very poor. It results in two aspects: 1- some relevant research articles are not mentioned; 2- the research structure, approach and obtained results are far from a common approach consolidated in the past decades. For these two aspects, I recommend:

10.1016/j.istruc.2018.06.004

10.1016/j.conbuildmat.2017.04.075

10.1016/j.engstruct.2014.01.031

10.1016/j.jobe.2017.03.004

10.1007/s10518-019-00603-6

10.1016/j.compstruc.2016.07.005

10.1016/j.conbuildmat.2011.08.046

10.1080/15583058.2020.1805045

10.1007/s11831-019-09351-x

10.1193/022512EQS053M

The reviewer is correct. All the aforementioned references regard structural assesment studies by the means of elaborated finite element models and nonlinear materials. The reviewer’s recommendation was carefully taken into account and therefore, all the proposed references were included except of reference 10.1016/j.conbuildmat.2011.08.046, which regards studies on adobe wall masonry not compatible with the stone masorny of the case study.

Reviewer 3 Report

This paper reports general historic, architectural and constructional aspects of historic school buildings of the Municipality of Agia (Greece), in addition to a detailed case study of a school building of Megalovrysso.  Although geographical, historic, architectural and constructional aspects were carefully presented, the authors failed to provide many details of the methodology used for materials characterization and structural analyses. In addition, many structural analyses results were not provided. Serious technical issues were also detected in the discussions of the structural analyses. The following problems need to be corrected for future recommendation for publication:

1.          Section 1: in line 56, the authors could briefly provide some examples of improper repair materials and techniques that could cause the secondary problems mentioned in this statement.

2.          Section 1: in line 91, it is necessary to provide a justification for the selection of the school building of Megalovrysso for the case study.

3.          Section 1: at the end of this section, the authors must cite the research gap that justified the development of the present research. After that, the authors should highlight the novelty of this paper. The architectural, constructional and structural analyses of the school building of Megalovrysso could be presented as original contributions for the literature.

4.          Section 2: standard test methods and equipment used in the experimental investigation mentioned in lines 118-121 (e.g., Schmidt hammer rebound testing, profometer measurements) should be reported in this section.

5.          Section 2: modelling approach and software used in the structural analyses should be reported in this methodology section.

6.          Section 3: There are two “Figure 1” in this manuscript. The Google maps provided in Section 3 should be Figure 2, rather than Figure 1.

7.          Section 3: What is the difference between the yellow, red, blue and green marks presented in Figure 1c provided in Section 3?

8.          Section 3: The authors could check if all school buildings were constructed in a single year, as presented in Table 1. For example, this table indicates that the Megalovryso school was constructed in 1931. In contrast, line 238 of the paper mentioned that the building was constructed in 1931-1933…

9.          Section 3: In Section 3.1, the authors could describe the interventions that have been made during the life time of the school buildings listed in Table 1 and Figure 2.

10.      Section 3: At the end of Section 3.1, the authors could present a justification for the selection of the school building of Megalovrysso for the case study, considering the information provided in comment #9 of this reviewer.

11.      Section 3: The authors should clarify if Figure 5 shows the studied building in its current state. The date of the photography could be added to the caption of the figure.

12.      Section 3: It is impossible to read the texts of Figure 1 and Figure 6 presented in this section.

13.      Section 3: how did you conclude that lime-based mortars (line 313) were used?

14.      Section 3: did you check if lintels (e.g, stone, concrete, or brick lintels) were constructed at the openings (windows and doors) of the masonry walls? This information is not mentioned in the manuscript.

15.      Section 3: all results of Schmidt hammer rebound testing could be listed in a table.

16.      Section 3: basic assumptions of the structural analyses should be moved to the methodology section (Section 2).

17.      Section 3: the authors must provide a justification for the assumption (i) material elasticity, considering the damage level of the structure, the level of the loading that is acting in the structural members, and the estimated strength of the materials. If a reliable justification is not provided (based on ALL these factors), the model will not represent the actual mechanical behavior of the structure.

18.      Section 3: the type and size of the finite elements must be reported, in addition to the mesh refinement studies.

19.      Section 3: what is the estimated relative strength between stone units and lime mortar? It must be considered to define the most appropriate stress-strain relationship for the masonry elements.

20.      Section 3: the authors did not mention the connection types considered between slabs and masonry, stone pillars and masonry, stone pillars and wooden beams, wooden beams and slabs, etc.

21.      Section 3: the meaning of some colors of Figure 9 was not provided in the caption of the figure.

22.      Section 3: what was the stiffness of the vertical springs that represent the soil-structure interaction?

23.      Section 3: how did you estimate the elastic modulus and density of masonry, concrete and wood? The authors must clearly explain the experimental procedures. If previous reference was used, the authors must justify why the data provided in the corresponding reference can be applied for the materials investigated in the present paper.

24.      Section 3: the authors must clarify the methods used to estimate the masonry compressive strength, shear strength and tensile strength. Input values and all standard formulation used in this prediction must be carefully provided. Where did you obtain the 1/20 factor mentioned in line 369?

25.      Section 3: the authors could indicate how they obtained the maximum compressive stress, shear stress and tensile stress from the model. The location where these stresses were observed must be provided.

26.      Section 3: unit of the scale bars presented in Figure 11 was not presented.

27.      Section 3: the authors should clarify if the stresses presented in Figure 11 and displacements presented in Figure 12 were associated with the static or dynamic analyses.

28.      Section 3: caption of Figure 12 was not provided.

29.      Section 3: unit of the scale bar presented in Figure 12 was not presented.

30.      Section 5: previous comments must be considered to correct the conclusions provided in Section 5, especially those related to the structural analyses.

31.      Section 5: limitations of the present paper and recommendations for future studies in the field must be provided at the end of the paper.

32.      Quality of all images of this manuscript is very poor. The authors should provide high-quality photography and high-quality vector drawings in all figures of the paper.

33.      Consistency is a frequent issue on this paper. Sometimes space was added between numbers and units (e.g., "40cm"; "400m²"; “4m”). Sometimes, space was not added between numbers and units (e.g., "60 cm", "50 cm"; “91.94 kPa”).

Author Response

With the present we would like to thank the reviewers for their fruitful comments on the present article. All questions/comments/suggestions were carefully studied and taken into account by the authors. The corresponding answers are located underneath each reviewer’s comment and all the changes are highlighted in the body text, including the references.

However, since the majority of the comments referred to the finite element modeling and its application to the structural assessment of the building, the authors should have clarified some corresponding issues. Therefore, the following paragraph(s), which is included in the body, clarifies a major misunderstanding and substantiates some of the most important assumptions of the study.

The primary steps of any structural assessment studies refer to the investigation and documentation of the existing structure in extent and in depth as well, in order to ensure the reliability of the data on which any further analysis will be based. Therefore, the following tasks must be accomplished: (i) detailed architectural drawings; (ii) description of the building’s history and possible previous interventions; (iii) investigation of interconnections between walls; (iv) detailed description of the structural bearing system; (v) description of the present state including pathology issues; (vi) conduction of in situ and laboratory experiments in order to determine type/strength of materials, etc.; (vii) investigation of foundation and subsoil type. Referring to the present study, taking into account the limited financial and technical means available at the present state, the structural assessment is restricted in the detection of the most vulnerable areas of the masonry building under persistent and seismic loading conditions. In addition to the aforementioned, KADET 2022-draft (see reference below) recommends a preliminary structural analysis in order to: (i) detect the most vulnerable zones; and (ii) define the possible failure modes. The results will enable the design of a targeted program of investigational surveys.

Furthermore, the very good present state of the masonry buildings, which is documented by the absence of cracks in the masonry body, enables the assumption of a linear analysis.

Therefore, the structural assessment is fulfilled in terms of exceedance of masonry strength at certain points/nodes, corresponding to the vulnerable areas of the structure.

KADET 2022, Draft – “Regulation for valuation and structural interventions of masonry”, Greek Organization of Earthquake Design and Protection (OASP).

Reviewer 3

This paper reports general historic, architectural and constructional aspects of historic school buildings of the Municipality of Agia (Greece), in addition to a detailed case study of a school building of Megalovrysso.  Although geographical, historic, architectural and constructional aspects were carefully presented, the authors failed to provide many details of the methodology used for materials characterization and structural analyses. In addition, many structural analyses results were not provided. Serious technical issues were also detected in the discussions of the structural analyses.

The authors would like to thank Reviewer #3, for the review of the manuscript, as well as all suggestions aiming at its improvement. All comments were taken into account and relevant revision was made, highlighted with red color in the text.

 

The following problems need to be corrected for future recommendation for publication:

1. Section 1: in line 56, the authors could briefly provide some examples of improper repair materials and techniques that could cause the secondary problems mentioned in this statement.

Revision was accordingly made and the following text was added: ‘The extensive use of cement-based materials during past repair works, especially in the cases where the historic physiognomy of the buildings was not taken into consideration, aggravated their present state of preservation, inducing damages (exfoliation of plas-ters-renders, humidity accumulation, degradation of stone elements and structural mortars etc).’

2. Section 1: in line 91, it is necessary to provide a justification for the selection of the school building of Megalovrysso for the case study.

The following text was added in lines 96-105: ‘The case study was selected due to multiple reasons, concerning the following: i) Date of construction (1931). According to literature, during the period 1928–1932 more than 3.000 schools were constructed in Greece [1,21], corresponding to one of the most productive eras of national school buildings’ erection. ii) Preservation state. The building undertook limited repair works during its life span. Up to now even the old equipment and furniture have been maintained. iii) Accessibility. The school has been decharacterized (not func-tioning as an educational unit), rendering its access feasible for the long-lasting on site inspection. iv) Future perspectives. Due to its decharacterization its multiscale analysis was rendered as necessary, in order to avoid future improper alterations and repair works.’

3. Section 1: at the end of this section, the authors must cite the research gap that justified the development of the present research. After that, the authors should highlight the novelty of this paper. The architectural, constructional and structural analyses of the school building of Megalovrysso could be presented as original contributions for the literature.

The folllowing text was added at the end of section 1: ‘It emerged from the gap shown in relevant literature [1,4,6,10-12,14-15], mainly focusing on the structural and energy integration of this significant part of common European built heritage that still maintains its initial functional role as educational centers. Due to the in-tense nowadays need for structural the integrity and energy performance of the running historic schools, it is considered as a mayor task to highlight the diachronic principles governing their construction in order to avoid improper repair works. This is also im-portant in cases of schools’ decharacterization and abandonment, so as to preserve them for future generations. The innovation of the study is based on its multi-disciplinary ap-proach, assessing valuable data from the historic, geographical, architectural, construc-tional and structural characteristics of this category of heritage structures.’

4. Section 2: standard test methods and equipment used in the experimental investigation mentioned in lines 118-121 (e.g., Schmidt hammer rebound testing, profometer measurements) should be reported in this section.

The folllowing text was added in section 2: ‘ACI 228.1R-03 [39], was taken into account for assessing the Schmidt rebound testing values.’

5. Section 2: modelling approach and software used in the structural analyses should be reported in this methodology section.

The modelling approach and the software used has been reported in the methodology section, as well.

6. Section 3: There are two “Figure 1” in this manuscript. The Google maps provided in Section 3 should be Figure 2, rather than Figure 1.

Revision was made and the first Figure was renaimed after ‘Chart 1’.

7. Section 3: What is the difference between the yellow, red, blue and green marks presented in Figure 1c provided in Section 3?

Revision was made in the Figure

8. Section 3: The authors could check if all school buildings were constructed in a single year, as presented in Table 1. For example, this table indicates that the Megalovryso school was constructed in 1931. In contrast, line 238 of the paper mentioned that the building was constructed in 1931-1933…

Revision was made. The construction year of the school is 1931. As added in section 1 ‘According to literature, during the period 1928–1932 more than 3.000 schools were con-structed in Greece [1,21], corresponding to one of the most productive eras of national school buildings’ erection.’

9. Section 3: In Section 3.1, the authors could describe the interventions that have been made during the life time of the school buildings listed in Table 1 and Figure 2.

Unfortunately this type of information is not availlable. However all relevant data is reported for the case study.

10. Section 3: At the end of Section 3.1, the authors could present a justification for the selection of the school building of Megalovrysso for the case study, considering the information provided in comment #9 of this reviewer.

The releavant text was inserted at the end of section 1, according to the comments of all reviewers, as following: ‘The case study was selected due to multiple reasons, concerning the following: i) Date of construction (1931). According to literature, during the period 1928–1932 more than 3.000 schools were constructed in Greece [1,21], corresponding to one of the most productive eras of national school buildings’ erection. ii) Preservation state. The building undertook limited repair works during its life span. Up to now even the old equipment and furniture have been maintained. iii) Accessibility. The school has been decharacterized (not func-tioning as an educational unit), rendering its access feasible for the long-lasting on site inspection. iv) Future perspectives. Due to its decharacterization, its multiscale analysis was rendered as necessary, in order to avoid future improper alterations and repair works.’

11. Section 3: The authors should clarify if Figure 5 shows the studied building in its current state. The date of the photography could be added to the caption of the figure.

The current year was added in Figure 5.

12. Section 3: It is impossible to read the texts of Figure 1 and Figure 6 presented in this section.

Figures 1 and 6 were revised. However the information provided is unnessecary to be presented.

13. Section 3: how did you conclude that lime-based mortars (line 313) were used?

The relevant text was revised as following: ‘probably lime-based mortars, usually confronted in structures of this era [1,6,17,22].’

14. Section 3: did you check if lintels (e.g, stone, concrete, or brick lintels) were constructed at the openings (windows and doors) of the masonry walls? This information is not mentioned in the manuscript.

The followng text was added: ‘From areas of plaster detachments above the openings, wooden lintels were recorded.’

15. Section 3: all results of Schmidt hammer rebound testing could be listed in a table.

The discussion regarding to Schmidt hammer rebound testing was revised, whle Table 2 was added.

16. Section 3: basic assumptions of the structural analyses should be moved to the methodology section (Section 2).
17. Section 3: the authors must provide a justification for the assumption (i) material elasticity, considering the damage level of the structure, the level of the loading that is acting in the structural members, and the estimated strength of the materials. If a reliable justification is not provided (based on ALL these factors), the model will not represent the actual mechanical behavior of the structure.

The assumption of material elasticity is justified by the very good preservation state of the building, since no masonry cracks or foundation’s settlements have been detected. A corresponding phrase has been added in the basic assumptions sections of paragraph 3.2.3.

Regarding the estimated strength, the corresponding paragraph was enriched with more details.

Furthermore, regarding the loading, a corresponding paragraph, table and figures were added to the body text.

18. Section 3: the type and size of the finite elements must be reported, in addition to the mesh refinement studies.

The type of area finite elements is mentioned in the body text and corrspond to four-node shell elements. Their size corresponds to 0.40 m and is based on refinement studies of a coarser mesh of 0.50 m. However, in a future more advanced model, which takes into account nonlinearities the size of the shell elements must be reduced.

19. Section 3: what is the estimated relative strength between stone units and lime mortar? It must be considered to define the most appropriate stress-strain relationship for the masonry elements.

A detailed paragrapg has been added to the body text, that describes the estimation of masonry strength according to limestone and mortart. In particular, the compressive strength of limestone equals to 30 MPa and of mortart equals to 2 MPa. However, since elastic analyses are carried out no specific stress-strain relationship has been defined for the masonry elements, except of the classical linear based on modulus of elasticity which equals to 6.657 GPa.

20. Section 3: the authors did not mention the connection types considered between slabs and masonry, stone pillars and masonry, stone pillars and wooden beams, wooden beams and slabs, etc.

In the frame of the preliminary analysis, full connection between all the structural elements is assumed. However, in a more advanced model, the connections should be studied in detail. For example, the wooden floor can be modeled by the use of frame instead of shell elements, taking into account their actual geometry and distribution and assuming releases at their connections with the walls for linear analyses or even better, contact elements for nonlinear analyses.

The assumption of full connection has been added in the body text.

21. Section 3: the meaning of some colors of Figure 9 was not provided in the caption of the figure.

Figure 9 was elaborated and a new detailed version is provided in the body text, including coloring description and specific heights of structure.

22. Section 3: what was the stiffness of the vertical springs that represent the soil-structure interaction?

An additional paragraph has been included in Section 3,which describes in detail the Winkler model adopted in the modeling of soil-structure interaction.

23. Section 3: how did you estimate the elastic modulus and density of masonry, concrete and wood? The authors must clearly explain the experimental procedures. If previous reference was used, the authors must justify why the data provided in the corresponding reference can be applied for the materials investigated in the present paper.

The estimation of elastic modulus and density of the masonry are explained in detail in the revised manuscript.

The elastic modulus of the concrete has been estimated according to Schmidt Ηammer tests.

The elastic modulus and density of the wood has been estimated through bibliographical reference and are in accordance with the wood properties used in construction in the area.

24. Section 3: the authors must clarify the methods used to estimate the masonry compressive strength, shear strength and tensile strength. Input values and all standard formulation used in this prediction must be carefully provided. Where did you obtain the 1/20 factor mentioned in line 369?

Regarding the estimated compressive and shear strength, the corresponding paragraph was enriched with more details.

Regarding the estimation of tensile strength, the following references have been added in the body text. The ratio between tensile and compressive strength of masonry receives the following values: (i) Reference Tarque et al. 2014 = 0.089; (ii) Reference Silva et al. 2018=0.013; and (iii)  Reference Aşıkoğlu et al. 2019=0.038. Therefore, the authors estimated a ratio of 1/20=0.05.

Tarque N.; Camata G.; Spacone E.; Varum H.; Blondet M. Nonlinear dynamic analysis of a full-scale unreinforce adobe model. Earthquake Spectra 2014, 30(4), 1643-1661. https://doi.org/10.1193/022512EQS053M

Silva C. L.; Mendes N.; Lourenço P.B.; Ingham J. Seismic Structural Assessment of the Christchurch Catholic Basilica, New Zealand. Structures 2018, 15, 115-130. https://doi.org/10.1016/j.istruc.2018.06.004.

Aşıkoğlu, A.; Avşar, Ö.; Lourenço, P.B.; Silva C. L.  Effectiveness of seismic retrofitting of a historical masonry structure: Kütahya Kurşunlu Mosque, Turkey. Bull Earthquake Eng 2019, 17, 3365–3395. https://doi.org/10.1007/s10518-019-00603-6

25. Section 3: the authors could indicate how they obtained the maximum compressive stress, shear stress and tensile stress from the model. The location where these stresses were observed must be provided.

The following phrase has been attached to the body text: “The main criterion in order to detect possible zones of failure is the exceedance of the developed stresses in comparison to the corresponding strengths. SAP2000 provides the stresses to the top and bottom faces of the shell element. Therefore, an additional calculation procedure was implemented in order to estimate the stresses in the middle area of each masonry wall.”

The locations of the maximum stresses that exceed the corresponding strengths are depicted in the Fig.13.

26. Section 3: unit of the scale bars presented in Figure 11 was not presented.

The unit of scale bars has been provided in the revised manuscript.

27. Section 3: the authors should clarify if the stresses presented in Figure 11 and displacements presented in Figure 12 were associated with the static or dynamic analyses.

All the Figures depicting stresses and displacements are associated with the response spectrum analyses, as mentioned in the paragraph wich precedes the figures.

28. Section 3: caption of Figure 12 was not provided.

Caption of corresponding figure has been provided in the revised manuscript.

29. Section 3: unit of the scale bar presented in Figure 12 was not presented.

The unit of scale bars has been provided in the revised manuscript.

30. Section 5: previous comments must be considered to correct the conclusions provided in Section 5, especially those related to the structural analyses.

Conclusions were revised.

31. Section 5: limitations of the present paper and recommendations for future studies in the field must be provided at the end of the paper.

Relevant information was added in the new subsection 3.3

32. Quality of all images of this manuscript is very poor. The authors should provide high-quality photography and high-quality vector drawings in all figures of the paper.

All Figures were revised according to the existing data

33. Consistency is a frequent issue on this paper. Sometimes space was added between numbers and units (e.g., "40cm"; "400m²"; “4m”). Sometimes, space was not added between numbers and units (e.g., "60 cm", "50 cm"; “91.94 kPa”).

Relevant revision was made throughout the whole text.

Round 2

Reviewer 1 Report

The paper has been revised according to the comments provided. Therefore, Reviewer suggests of considering the paper for the publication.

Author Response

The authors would like to thank Reviewer #1 once again for the fruitful and to the point comments/suggestions for improving the manuscript.

Reviewer 2 Report

The comments have been addressed. The manuscript is acceptable for publication.

* Regarding the number of modes, SAP2000, offer the option to limit the number of modes by imposing the maximum modes for each direction, during a Ritz Modal Analysis. For simple, or regular structures it is very easy  to achieve a high total active mass. For some complicated structures, even Ritz modal analysis requires more modes. 

Author Response

The authors would like to thank Reviewer #2 once again for the fruitful and to the point comments/suggestions for improving the manuscript.

Reviewer 3 Report

The authors successfully corrected most of the problems identified by this reviewer. Excellent solutions were provided for many issues associated with geographical, historic, architectural and constructional aspects. However, remaining technical mistakes (mainly related to the structural analyses) were not solved in the first review round. The following problems need to be corrected before recommendation for publication:

1.       It seems that the authors failed to provide an appropriate modelling of the regions with critical stresses presented in Figure 13. In the response to comment #14, the authors mentioned that wooden lintels were located above the openings. However, these elements were not observed in Figure 13. Since the structural analysis of this work aimed to detect the most vulnerable areas of the building, the positive contributions of the lintel of the openings cannot be neglected.

2.       Response to comment #18 was not appropriate because the manuscript did not report the size of the finite elements and the conclusions of the mesh refinement studies.

3.       In the response to comment #19, the authors estimated that the ratio between the strength of mortar and the strength of the masonry units was only (2 MPa)/(30 MPa) = 6.7%. In this situation (mortar softer than units), a strong nonlinear behavior is observed since the beginning of the stress-strain curves of the masonry elements, according to previous literature (e.g., Mohamad et al. - 10.1590/s1983-4195201800020004, Nalon et al. - 10.1016/j.conbuildmat.2021.126181, and Ravula et al. - 10.1617/s11527-016-0926-1), due to propagation of microcracks in the joints associated with localized mortar crushing. This nonlinear behavior was not discussed in the manuscript and the masonry was considered as an elastic linear material, which is not technically correct.

4.       The revision mentioned in comment #7 of this reviewer was not evident in Figure 1c. What is the difference between the yellow, red, blue and green marks of this figure?

5.       In the response to comment #23, the authors estimated the masonry strength using K = 0.5. However, the Eurocode recommends K = 0.45 when stone units are used in the masonry walls. The authors should clarify the reasons for selecting K = 0.50.

Author Response

All answers to comments are presented in detail in the attached file.

Author Response File: Author Response.pdf