Strength Performance of the Connection between Brick and SPF Lumber

Round 1

Reviewer 1 Report

The paper addresses an important topic - enhancing the resilience of unreinforced masonry systems. The authors have focused specifically on the failure of such systems under exposure from lateral loads imposed during an earthquake. In the introduction there is a brief statement (two lines) indicating that this is an active area of research. There is a need for this to be expanded further to identify the knowledge gap and key research questions motivating the authors to do the research. The discussion of findings and also recommendations for further work at the very end should tie back to these two items. The authors must include a state of the art review as part of the discourse.

Author Response

Review response to Dear REVIEWER – 1

First of all, thank you very much for reviewing our research. We respect your comments and suggestions. We explained our response to each comment.

Comment 1:

In the introduction, there is a brief statement (two lines) indicating that this is an active area of research. There is a need for this to be expanded further to identify the knowledge gap and key research questions motivating the authors to do the research. The discussion of findings and also recommendations for further work at the very end should tie back to these two items.

Authors response 1:

Thank you very much for your comments and suggestions on how to improve our research. All comments and suggestions included in the revised manuscript. The research limitations and key research questions are important concepts. The mechanical properties of the bolts connection are an important parameter for strengthening the unreinforced masonry wall by using timber material. In the limitation of this study, the substrate material is only brick, and the bolt depth is shallow. However, determining the pull-out and shear strength and the failure mechanism is necessary to determine further studies' complexity. A composite specimen (brick-to-lumber) was prepared and tested to determine the shear load on the bolt. This specimen is used in the calculation of timber structures, and it is predicted that a composite model is suitable for extending the limited structural calculations in masonry.

Comment 2:

The authors must include a state-of-the-art review as part of the discourse.

Authors response 2:

Thank you for your comment. In recent years, the number of strengthening methods using timber material for the unreinforced masonry structure has increased. The number of research materials is insufficient to compare concrete materials. The state-of-the-art reviews were added to the introduction in the revised manuscript. In the introduction for the revised manuscript, the state-of-the-art review included two types of content: the study of the tensile strength and shear strength of bolt or screw attached to masonry walls and a description of the fastener type and how to connect the masonry wall and timber material.

Author Response File: Author Response.pdf

Reviewer 2 Report

Article “Strength performance of the connection between brick and SPF 
lumber” investigated the strengths (pull-out and 18 shear) of the bolt connection with chemical adhesive for red clay brick and SPF lumber. 
The authors are suggested to incorporate following items.

Quantitative results in Abstract.

Introduction is too short and there is a need to improve the introduction with some latest literature to enhance the importance of this study.

 Please include information related to the bricks, composition and manufacturing details.

 For N10 and A10 361 specimens, the experimental load-displacement diagram presents different results. It displays brittle and ductile behavior. Please include proper reasons for this difference.

Conclusions must be concise and to the point.

 

 

Author Response

Review response to Dear REVIEWER – 2

First of all, thank you very much for reviewing our research. We respect your comments and suggestions. We explained our response to each comment.

Comment 1:

Quantitative results in Abstract.
Authors response 1:

Thank you for your comment. Following your comments, the abstract in the revised manuscript included the number of tests, and the pull-out load and the shear load of the M12 bolts, which were considered the most effective in this study.

Comment 2:

Introduction is too short and there is a need to improve the introduction with some latest literature to enhance the importance of this study.

Authors response 2:

Thank you for your comment. It is true that the introduction is too short. Our study aims to study the shear strength of the unreinforced brick wall with timber material under lateral load. As the first step of our study, it is necessary to investigate the strength performance of the connection between masonry wall and timber material. Based on the first step, the state-of-the-art review included two types of content in the revised manuscript: the study of the tensile strength and shear strength of bolt or screw attached to masonry walls and a description of the fastener type and how to connect it between the masonry wall and timber material.

Comment 3:

 Please include information related to the bricks, composition, and manufacturing details.

Authors response 3:

Thank you for your comment. The bricks used in the experiment were purchased from a building materials store in Japan. Information on the composition of the bricks and the manufacturing details is currently lacking. Instead of composition and manufacturing details for brick, the brick size, density, and water absorption values were added in the revised manuscript.

Table 1. The result is related to the mean value of 10 bricks (ASTM C76/C67M-20)

	Brick size (mm)			Density (g/cm3)	Absorption
	Length	width	depth		%
Mean [CV, %]	210.3 [0.9]	97.4 [1.3]	61.8 [1.7]	1.9 [2.5]	0.3 [14.8]

Comment 4:

For N10 and A10 361 specimens, the experimental load-displacement diagram presents different results. It displays brittle and ductile behavior. Please include proper reasons for this difference.

Authors response 4:

Thank you for your comment. All comments and suggestions included in the revised manuscript. The differences in the results of shear tests were firstly checked by the dimensions of the brick holes in Table 2. The diameter of the hole and the dimensions of the bolt installation depth are very close to the expected values. In that case, the vertical deviation was not checked in the hole. Figure 1 shows the hole position and measurement of brick for the shear test. It is concluded the preparation of brick hole is good.

Table 2. The hole diameter and depth in the brick

A side of brick hole (mm)				B side of brick hole (mm)				Number of specimens
Diameter		Depth		Diameter		Depth
expected	actual	expected	actual	expected	actual	expected	actual
10	9.8 [5.9]	50	51.8 [3.6]	10	9.9 [3.5]	50	52.2 [3.1]	3
12	11.7 [1.8]	50	51.6 [1.4]	12	12.0 [0.7]	50	52.4 [2.9]	3
14	14.2 [1.3]	50	50.7 [2.4]	14	14.1 [0.2]	50	50.9 [1.1]	3

The value in the bracket is the coefficient of variation.

B side	A side

Figure 1. The photo of brick

Figure 2 and Figure 3 illustrate the photo failure and the load-displacement diagram of each N10 specimens. When observing the in failure photo N10-1, a crack started to form between the top and bottom bolt in brick material. It is predicted due to excessive tightening of the bolts. During the test specimen preparation, the tightening strength of the bolt was not predetermined and measured. It is assumed a constant tightening force gives the specimen. Based on the excessive tightening on the bolt, the result of the N10-1 specimen may show a low load. As seen from the failure photo in N10-2 and N10-3, the starting point of the crack is close to the top bolt on the brick. We have decided to remove the sentence “It displays brittle and ductile behavior”. It prefers to explain the reason of the difference diagram.

N10-1	N10-2	N10-3
A10-1	A10-2	A10-3

Figure 2. Failure of N10 specimens

N10-1	N10-2	N10-3
A10-1	A10-2	A10-3

Figure 3. The load-displacement diagram of N10 specimens

Comment 5:

Conclusions must be concise and to the point.

Authors response 5:

Thank you for your comment.  The conclusions included briefly and clearly in the revised manuscript based on your comment.

 

 

 

 

 

 

 

 

 

 

 

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

Thank you very much for the interesting research. The topic is indeed interesting and needs research. The topic of the manuscript is in accordance with the Journal requirements.

The manuscript deals with the performance of strengthened masonry buildings when subjected to horizontal loads and retrofitted with timber elements. A short introduction in the STAR documentation is given and experimental analyses are obtained. The focus was set on pull-out strength of steel dowels from the masonry bricks. The topic of the paper is interesting for a broad audience. Presented solutions are not a novelty but are still very good examples of how timber can be a better retrofit solution/strategy than concrete. Nevertheless, a lot of additional work is needed to accept the manuscript in the Journal. I have a lot of remarks but I will emphasize the crucial ones.

• Language: Not appropriate. The article needs heavy improvements because some parts are hard to read and are not written in proper English. I’m not pointing out them here because there are rok many mistakes. Please consider that the native speaker reads your paper.
• Title: My opinion is that the focus is set on pull-out strength, not on strength performance.

• Abstract: Tol many strange formulations. Spf is not explained.

Specific comments:

• STAR is not very well described and must be improved. In the beginning of the article, the authors are talking about Mongolia and earthquakes in Mongolia. Europe, where masonry also prevails is not mentioned. More recent interesting new manuscripts are published on the behaviour of masonry/stone buildings after the earthquakes in Greece, Albania, and Croatia. Some examples

Doi: 10.1016/j.engfailanal.2020.104803, Doi: 10.1016/j.ijdrr.2021.102140, doi: 10.1016/j.engfailanal.2021.105824

I think you should at least mention Europe where the majority of research on the topic is coming from. Also, you have r references on Mongolian earthquakes but I think all of them are not needed. My concern is that the products like CLT and SPF are not widely accepted in Mongolia.

• You are mentioning magnitude, what magnitudes? ML, Mw?
• What is the dowel bearing test?
• How many bricks were tested? Are these dimensions of bricks common? In Europe, they are not.
• Lines 121 and 122, why did you choose 50mm?
• What was the loading protocol in line 136?
• Reference 17 is from 2002, why? I hope there is a newer standard
• N-type and A-type specimens should be explained better
• Edge distances for wood are not respected
• Embedment in wood is not clarified
• Major concern – brick failure is almost always shown and failure modes presented in figure 2 are not present. Maybe just a pure pull-out.
• Figure 10 – average value is not a good assumption because of huge deviations
• Figure 13 – better quality photos are needed.
• Line 404&405 – please clarify!
• Line 409 – not true. The preparation of the experiment was weak so the results are like they are.
• Figure 15- steel failure mode. Of course that if you have a large diameter of a rod, then steel fails later. The whole idea is to calculate minimum values of all of the possible failure modes.

 In the end, the work is promising and very interesting but lacks a critical overview, experiments are not very well prepared and STAR documentation needs to be improved. The paper is based on timber failure modes, but the embedment of timber is not very well presented. English needs serious improvements. I hope that the above-mentioned suggestions can improve the quality of the manuscript.

Author Response

Review response to Dear REVIEWER – 3

First of all, thank you very much for reviewing our research. We respect your comments and suggestions. We explained our response to each comment.

Comment 1:

Language: Not appropriate. The article needs heavy improvements because some parts are hard to read and are not written in proper English. I’m not pointing out them here because there are rok many mistakes. Please consider that the native speaker reads your paper.

Authors response 1:

Thank you very much for your advice on how to improve our research. We focused on improving English in the revised manuscript.

Comment 2:

Title: My opinion is that the focus is set on pull-out strength, not on strength performance.

Authors response 2:

Thank you for your comment. We respect your suggestions. The introduction does not explain about our research completely, which means it does not fully understand our research. The purpose of our study is the first step in the study of the strengthening method of the unreinforced masonry walls using wood material. In the case of lateral loads, it is possible to fail the masonry wall in in-plane and out-of-plane directions. Similarly, it is assumed that pull-out and shear forces can be applied to the bolt connection. Therefore, we named the article “Strength performance”.

Comment 3:

Abstract: Tol many strange formulations. Spf is not explained.

Authors response 3:

Thank you for your comment. In rewriting the abstract of the revised manuscript, we focused more on clarifying unknown contents. For example, SPF is the abbreviation of spruce, pine, and fir.

Specific comment 4:

STAR is not very well described and must be improved. In the beginning of the article, the authors are talking about Mongolia and earthquakes in Mongolia. Europe, where masonry also prevails is not mentioned. More recent interesting new manuscripts are published on the behaviour of masonry/stone buildings after the earthquakes in Greece, Albania, and Croatia. Some examples: Doi: 10.1016/j.engfailanal.2020.104803, Doi: 10.1016/j.ijdrr.2021.102140, doi: 10.1016/j.engfailanal.2021.105824

I think you should at least mention Europe where the majority of research on the topic is coming from. Also, you have r references on Mongolian earthquakes but I think all of them are not needed. My concern is that the products like CLT and SPF are not widely accepted in Mongolia.

Authors response 4:

Thank you for your comment. It is agreed that information about Mongolia is not required in the introduction of the revised manuscript. The research materials you have presented show the damage caused by the recent earthquake to the unreinforced masonry. These research materials are a fact for researchers, and it is possible to predict the damage to the existing unreinforced masonry buildings. It is also proposed to write in the introduction that unreinforced masonry buildings in seismic zones are not only a problem for developing countries but also a potential risk for developed countries. Another issue that your concern is that CLT and SPF are not currently used in Mongolia. We hope Mongolia will use the CLT and SPF in the future.

Comment 5:

You are mentioning magnitude, what magnitudes? ML, Mw?

Authors response 5:

Thank you for your comment. Magnitude is moment magnitudes. Based on the notion that the introduction should be as concise as possible, some of the terms and conditions were not written, making it difficult to read. We considered carefully about it in the revised manuscript.

Comment 6:

What is the dowel bearing test?

Authors response 6:

Thank you for your comment. The test which determines the dowel bearing strength for wood is called the dowel bearing test (ASTM D5764 standard). The reference value of dowel bearing strength of wood, metal, aluminum and concrete is shown in Table A1 of Technical report 12 (NDS standard). For the reference value of concrete is three times compressive strength. But the experimental result showed 1.4 times compressive strength of brick in our experiment.

Comment 7:

How many bricks were tested? Are these dimensions of bricks common? In Europe, they are not.

Authors response 7:

Thank you for your comment. The brick dimensions used in Japan are 210 x 100 x 60 mm. There were 10 bricks for the flexural test, 6 bricks for the compressive test, 9 bricks for the pull-out test, 9 bricks for the dowel bearing test, 18 bricks for the shear test. A total of 52 bricks were used in the study.

Comment 8:

Lines 121 and 122, why did you choose 50mm?

Authors response 8:

Thank you for your comment. The manual for chemical adhesives is based on concrete materials. It is mentioned the bolt depth shall be at least 60 mm. The brick size is 210 x 100 x 60 mm. When installing the bolts in the brick, it is planned to place on the 100 mm side of the brick. Based on the symmetry condition, the depth was selected by 50 mm.

Comment 9:

What was the loading protocol in line 136?

Authors response 9:

Thank you for your comment. Monotonic loading was during the test.

Comment 10:

Reference 17 is from 2002, why? I hope there is a newer standard

Authors response 10:

Thank you for your comment. The standard is still used in the design of timber structure.

Comment 11:

N-type and A-type specimens should be explained better

Authors response 11:

Thank you for your comment. We agree with you. When rewriting, the revised manuscript described the test specimen in more detail. The dowel fasteners are often bonded to the masonry wall with chemical adhesive. Also, chemical adhesive was used to improve the adhesion of bolts and wood materials. Our study carried out the difference between chemical adhesive is used (A-type) OR not (N-type) for the wood-to-bolt section when the chemical anchor is utilized in the masonry wall. The test results showed that shear load and the slip modulus are different for A-type and N-type.

Comment 12:

Edge distances for wood are not respected

Authors response 12:

Thanks for the comment. For timber structures, the edge distance from bolt depends on the diameter of the bolts. The edge distance will prevent the wood material from cracking before loading. In our study, the relevant information was included in the experimental specimen. For example, it is mentioned in lines 197 and 198 of the first manuscript. Figure 5b shows the location of the bolts on the timber. For lumber, the edges distance from bolt, the length of lumber (line 198 in the first manuscript) is calculated relying on the diameter of the bolt. The revised manuscript contained more detailed information.

Comment 13:

Embedment in wood is not clarified.

Authors response 13:

Thank you for your comment. We agree with your comments. This type of information is not included in the first manuscript. The bolts are prepared to penetrate the width of the lumber. The diameter of the hole is described in line 194 of the previous manuscript. We assumed the more information is not necessary.

Comment 14:

Major concern – brick failure is almost always shown and failure modes presented in figure 2 are not present. Maybe just a pure pull-out.

Authors response 14:

Thank you for your comment. Figure 2 you wrote does not show the condition of the failure modes. Figure 2 shows the bolt's position in the brick, the diameter of the holes, and the diameter of the bolts. You may have mistyped the photo number. We think it has to do with Figure 7. Figure 7 illustrates the predictive states which may show such failure mode. The test results show that, as you say, only the bricks are in any way broken. No damage was shown by the bolt or between chemical adhesive and bolt or between adhesive and surface. It was considered appropriate to add this state to the conclusion in the revised manuscript.

Comment 15:

Figure 10 – average value is not a good assumption because of huge deviations.

Authors response 15:

Thank you for your comment. We agree with what you said. Because of the high deviation, taking the predicted pull-out load as an average value is not appropriate. This may be due to the need to increase the number of tests or better test specimen preparation. However, the least number of experiments is 3, which is considered sufficient. The word “average” was changed to the word “mean” in the revised manuscript.

Comment 16:

Figure 13 – better quality photos are needed.

Authors response 16:

Thank you for your comment. We focused on improving photo quality.

Comment 17:

Line 404&405 – please clarify!

Authors response 17:

Thank you for your comment. Considering your comment, it is appropriate to write in more detail in the revised manuscript. The formula for predicting cone failure is that the anchor distance from concrete edge is at least equal to the installation depth of the bolt. In our case, the anchor distance from the brick edge is less than the bolt installation depth.

Comment 18:

Line 409 – not true. The preparation of the experiment was weak so the results are like they are.

Authors response 18:

Thank you for your comment. The meaning of the sentence on line 409 is incorrect that we wrote in the previous manuscript. We corrected the meaning of sentence in the revised manuscript. Bonding failure mentioning in the study of Rosana Munoz, occurs between the adhesive and surface or between adhesive and fastener. The adhesion between bolt and epoxy, and between epoxy and surface material was illustrated good result for our experiment. There was no failure between their connection. Failure only occurred in the brick material.

Comment 19:

Figure 15- steel failure mode. Of course that if you have a large diameter of a rod, then steel fails later. The whole idea is to calculate minimum values of all of the possible failure modes.

Authors response 19:

Thank you for your comment. The larger the bolt diameter, the predictable strength is high. In our case, the steel failure is less likely to occur due to the shallowness of the bolt installation. We agree to consider the minimum load value. However, the predicted combined cone failure and the splitting failure values show similar values. We assume that the two types of damage occurred simultaneously.

Comment 20:

In the end, the work is promising and very interesting but lacks a critical overview, experiments are not very well prepared and STAR documentation needs to be improved. The paper is based on timber failure modes, but the embedment of timber is not very well presented. English needs serious improvements. I hope that the above-mentioned suggestions can improve the quality of the manuscript.

Authors response 20:

Thank you for your comment. We hope the authors have corrected the revised manuscript on your comment and suggestions.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The feedback from the first round of reviews have been addressed.

Author Response

Review response to Dear REVIEWER – 1

(Round 2)

Comments and Suggestions for Authors:

The feedback from the first round of reviews have been addressed.

Authors response 1:

Thank you very much.

Author Response File: Author Response.pdf

Reviewer 3 Report

Please upload the following manuscript: Strength performance of the connection between brick and SPF lumber.   The wrong document is uploaded: A P-I diagram approach for predicting dynamic response and damage assessment of Reactive Power Concrete columns subjected to blast loading

Author Response

Review response to Dear REVIEWER – 3

(Round 2)

Comment 1:

Please upload the following manuscript: Strength performance of the connection between brick and SPF lumber. The wrong document is uploaded: A P-I diagram approach for predicting dynamic response and damage assessment of Reactive Power Concrete columns subjected to blast loading

Authors response 1:

Thank you very much for your comment. We uploaded our revised manuscript, “Strength performance of the connection between brick and SPF lumber,” on the website on the 27^th of March. Assigned editor said that it was a mistake during their work process.

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Dear authors,

the article seems better now. I still have some problems with accepting it because the failure occurred in bricks and not in steel rods. It is still valuable to the field. You can find my comments in the pdf file.

Comments for author File: Comments.pdf

Author Response

Review response to Dear REVIEWER – 3

(Round 3)

Thank you so much for reviewing the revised manuscript (Round 1).

Comment 1.1:

Track-changes are not included so it was hard for me to see the new parts.

Authors response 1.1:

Thank you very much for your comment. We sincerely apologize to you not using Track-changes in the previous manuscript. In this revised manuscript, we used the track-changes.

Comment 14.1:

Failure modes shown in Figure 7 are completely different than the ones shown in Figure 9. Always the brick failed completely, and you don’t have this kind of infographic in Figure 7. Please comment it critically. Probably the diameter of rod is too thick.

Authors response 14.1:

Thank you for your comment. From the four failure mode assumptions shown in Figure 7, it is assumed that the combined cone-bond failure and splitting failure occurred due to the experimental failure shown in Figure 9. The load-displacement diagram shows that the load increases sharply to reach its maximum load and gradually decreases. Failure mode shows the state of the combined cone-bond failure mode until the pull-out load reaches its maximum value. The brick is split into two parts from starting to downward cracks on the upper part of the brick when the maximum load decreases. It is suggested that it is possible to determine the failure mode as predicted. It also indicates the minimum failure load value for combined cone-bond failure and splitting failure. The minimum load value and the test failure show that the combined cone-bond failure occurred up to the maximum load and was followed by splitting failure. As the pull-out test results, the predicted failure modes and loads are considered reasonable.

A thick threaded rod has a high stiffness and strength. Therefore, thick threaded rod is necessary for our study related to the strengthening method.

Comment 15.1:

Please include also percentile values in the graphs.

Authors response 15:

Thank you for your comment. According to your comment percentile values in the graphs. In Figure 10, the percentile 5^th was included.

Comment 18.1:

This is the critical part of your experiment. Please explain in a detail why rod failed. Experiment should be designed differently. The failure of the brick is not preferable. Ductility should be in a steel rod.

Authors response 18.1:

Thank you for your comment. No case was the damage of threaded rod during the pull-out test. Failure occurs in the weak resistance surface with the high-stress concentration. Our pull-out experimental result showed that the brick surface has the low resistance than the connections between brick to epoxy and epoxy to bolt, showing the brick material's damage. The chemical anchor in the brick wall can show sliding failure. To attach the timber to the existing brick wall, the main role of timber is related to reducing the movement of brick and chemical anchor in a parallel direction to the load. The load acting on the out-of-plane wall concentrates the tensile force on the chemical anchor. In the case of only brick failure, it is necessary to withstand the tensile load for a thick threaded rod having high stiffness and strength. Therefore, the strengthened brick walls with wood are important to reduce the out-of-plane damage.

Comment 20.1:

Reference number 7 – the names of the authors are wrongly written

Authors response 20.1:

Thank you for your comment. In this revised manuscript, we hope the names of the authors were correctly written.

Author Response File: Author Response.pdf

Round 4

Reviewer 3 Report

Thank you for the comments. The article can be published.