Effect of a Novel Dowel and Cramp on the In-Plane Behavior of Multi-Leaf Stone Masonry Walls Proposed for Modern Masonry Buildings

Round 1

Reviewer 1 Report

Consideration of the following comments and suggestions will improve the comprehension of the presented material.

Review comments

1.     The authors mention in the Introduction section, that they propose a wall that will be durable against earthquakes (lines 73-75). How do they make this statement since they do not test their wall against earthquake loads and for out of plane motion? I believe these sentence needs to be modified. In addition, they mention that “This wall is meant to  be used in constructing new modern masonry buildings with majestic architecture thereby providing all the comforts of a modern building along with durability.” What is the majestic about?

2.     The proposed muti-leaf wall takes a lot of space of the plan under earthquake loads. What is the purpose of having the cavity in between?

3.     Can this wall sustain out of plane motions without decomposed? Can these connectors keep the two stone layers?

4.     What is the benefit of having this wall compared to the other types of walls?

5.     Figure 16 shows the compressive strength of micro-sized and micro-sized wall. The difference is close to 90%, as the authors mention. How the slenderness ratio affects the strength? Can the authors add a figure showing the compressive strength with respect to the slenderness ratio?

I beleive that the English language can be improved.

Author Response

Comments from Reviewer 1

Comments and Suggestions for Authors: Consideration of the following comments and suggestions will improve the comprehension of the presented material.

Response: We appreciate the positive feedback from the reviewer.

Comment 1: The authors mention in the Introduction section, that they propose a wall that will be durable against earthquakes (lines 73-75). How do they make this statement since they do not test their wall against earthquake loads and for out of plane motion? I believe these sentence needs to be modified. In addition, they mention that “This wall is meant to be used in constructing new modern masonry buildings with majestic architecture thereby providing all the comforts of a modern building along with durability.” What is the majestic about?

 Response: Thank you for pointing this out. The statement in the manuscript about the wall being durable against earthquakes is that it is our design principle. As the reviewer pointed out, although the out-of-plane behavior of walls was not investigated in this study, we believe that the proposed wall is more durable than traditional multi-leaf stone walls due to the use of metal connectors. When the experimental results were examined, it was observed that the parameters, such as the shear strength and energy absorption capacity of the wall, significantly increased due to the use of metal connectors. The improvement of these parameters means the improvement of the strength and durability  of the wall, especially against lateral loads such as earthquakes. Considering the constructive feedback of the reviewer, the sentence between lines 74-77 has been changed as follows for better understanding.

‘The design principle of the proposed wall is based on meeting the needs of a modern building without vitiating the appearance of the stone wall while being more durable against earthquakes due to the metal connectors used in the wall.’

The word majestic is used because the proposed wall consists of two layers and a cavity between them. Thereby, concealing all the necessary installments in the cavity will flourish the appearance of the stone wall inside and outside. If the reviewer deems it appropriate, we changed the sentence (lines 92-94) as follows. This wall is meant to be used in constructing new modern masonry buildings with modern architecture, thereby providing all the comforts of a modern building along with durability.

Comment 2: The proposed muti-leaf wall takes a lot of space of the plan under earthquake loads. What is the purpose of having the cavity in between?

 Response: Yes, we agree that the wall takes up a lot of space in the plan, but when the historical masonry buildings that survived many destructive earthquakes are examined, it is seen that the width of the walls is very large. The reason for this is the low shear strength of the wall due to the poor mechanical properties of the individual elements used in masonry walls and the mortars connecting these elements. The simplest way to solve this problem and increase the shear strength of the wall was to increase the width of the wall in ancient masonry buildings. Considering this issue, the shear strength of the proposed wall has been improved by metal connectors. The width of the proposed wall is relatively small compared to the historical masonry walls. The main reason for leaving a cavity between two layers is to provide comforts such as heat and sound insulation and conceal all installments in the building.

Comment 3: Can this wall sustain out of plane motions without decomposed? Can these connectors keep the two stone layers?

Response: You have raised an important point here. It would have been interesting to explore this aspect. However, in the case of our study, it seems slightly out of scope because out-of-plane studies need a thorough experimental campaign, as we mentioned in section 2.3.1. (lines 222-228). We are working on determining the proposed walls' out-of-plane behavior and will present the results in upcoming articles. 

Comment 4: What is the benefit of having this wall compared to the other types of walls?

 Response: Thank you for pointing this out. We concluded a short summary about the benefits of this wall and added it at the end of section 5 (lines 746-754).

The following can be summed up in light of the experimental campaign conducted in this study, allowing the proposed wall to be favored. The cavity between the two layers makes the proposed wall lighter than typical multi-layer walls. This decreases the weight of the wall and the building, which lessens the force of an earthquake acting on the structure. The cavity between the wall's layers also contributes to an increase in the wall's in-plane moment of inertia. The exquisite craftsmanship of the stone is shown on both the inside and outside of the wall, and issues like heat and sound insulation, which are crucial in modern structures, are resolved inside the wall.

Comment 5: Figure 16 shows the compressive strength of micro-sized and micro-sized wall. The difference is close to 90%, as the authors mention. How the slenderness ratio affects the strength? Can the authors add a figure showing the compressive strength with respect to the slenderness ratio?

 Response: Thank you for your contribution. A figure depicting the compressive strength with respect to the slenderness ratio is added in Figure 16. c. 

Reviewer 2 Report

In this paper, the in-plane mechanical behavior of a multi-leaf stone masonry wall with metal connectors is investigated experimentally. This is a well written, interesting, and useful contribution. The reviewer recommends the authors address the following comments and revise the manuscript for a resubmission.

1. Lines 573-576 in Section 4.1: The reviewer failed to understand the mechanism of the decrease in compression strength and modulus of elasticity. For example, the shear strength of concrete members is affected by the size effects associated with the size of aggregates used in the concrete. In this study, cut stones that appears to be of homogeneous material are used as a component of walls. Can you provide more explanation why the compression strength and modulus of elasticity decrease due to the size effects?

2. Lines 603-610 in Section 4.1: Why did the direct application of the cramps caused the increase in the compression strength in the tests of macro-sized specimens?

3. Considering the proposed connections with cramps and dowels, bending test is important to investigate the seismic capacity of the proposed walls. The proposed connections seem to unable to resist tensile forces under seismic loading. Can you provide some comments on the seismic capacity of the proposed walls in the manuscript?

4. Figure 11 (a) and (d): The drawings of cross-section in Figure 11 (a) and (d) should be replaced.

Author Response

Comments from Reviewer 2

Comments and Suggestions for Authors: In this paper, the in-plane mechanical behavior of a multi-leaf stone masonry wall with metal connectors is investigated experimentally. This is a well written, interesting, and useful contribution. The reviewer recommends the authors address the following comments and revise the manuscript for a resubmission.

Response: We appreciate the positive feedback from the reviewer.

Comment 1: Lines 573-576 in Section 4.1: The reviewer failed to understand the mechanism of the decrease in compression strength and modulus of elasticity. For example, the shear strength of concrete members is affected by the size effects associated with the size of aggregates used in the concrete. In this study, cut stones that appears to be of homogeneous material are used as a component of walls. Can you provide more explanation why the compression strength and modulus of elasticity decrease due to the size effects?

 Response: You have raised an important point here. To make the topic of the size effect clearer to the readers we have added an explanation and a Figure showing the compressive strength with respect to the slenderness ratio in Section 4.1 (lines 574-587). The added paragraph is as follows.

Two different specimen sizes were used to determine the compressive strength of the proposed multi-leaf wall. This is to investigate the slenderness ratio (hef/tef), which is the ratio of effective height to effective width. As stated in [65], the slenderness ratio of the masonry wall should not be greater than 27. Considering the results, a decrease of around 90% is observed in the compressive strength of the wall due to the size effect (Figure 16. c). This decrease in compressive strength and modulus of elasticity can be explained as stated in [1]. Regardless of the material used in the wall, the total load that a wall could safely transmit would be determined by multiplying the cross-sectional area of a wall—whose height is relatively low compared to its thickness—by the masonry's design strength. However, as the height of a wall of a given cross-section increases, its load-bearing capacity decreases due to additional bending stresses. Additionally, if the load is applied away from the section's central axis, lateral deflections and bending stresses rapidly rise, reducing the structure's ability to support loads [1]. 

Comment 2: Lines 603-610 in Section 4.1: Why did the direct application of the cramps caused the increase in the compression strength in the tests of macro-sized specimens?

 Response: This result was unexpected. Therefore, if the reviewer finds it suitable, we added an explanation as follows (lines 620-626).

This outcome was unexpected. The compressive strength of the micro-sized specimens was calculated by averaging the data from the three specimens. The compressive strength of the macro-sized specimen, on the other hand, is the outcome of a single specimen. This makes the results of macro-sized specimens' compressive tests potentially unreliable. Since the individual stone in the wall is not homogenous, testing at least three wall specimens and averaging the results before evaluating them is recommended.

Comment 3: Considering the proposed connections with cramps and dowels, bending test is important to investigate the seismic capacity of the proposed walls. The proposed connections seem to unable to resist tensile forces under seismic loading. Can you provide some comments on the seismic capacity of the proposed walls in the manuscript?

 Response: Thank you for this suggestion. It would have been interesting to explore this aspect. As stated in Eurocode 6 Section 3.6.3. ‘The characteristic flexural strength of masonry may be determined by tests in accordance with EN 1052-2, or it may be established from an evaluation of test data based on the flexural strengths of masonry obtained from appropriate combinations of units and mortar’. Since this subject is out of the scope of our study, the bending strength of the proposed wall has not been determined. However, we are planning to carry out an extensive experimental assessment of the out-of-plane behavior of the proposed wall. Then, we would like to explore the aspect you suggested. Thank you for your contribution.

Comment 4: Figure 11 (a) and (d): The drawings of cross-section in Figure 11 (a) and (d) should be replaced.

 Response: As suggested by the reviewer, Figures 11 (a) and (d) has been corrected.

Reviewer 3 Report

The paper presents and discusses the experimental assessment of the in-plane mechanical behavior of a multi-leaf stone masonry wall built from cut stone and reinforced with metal connectors (cramps and dowels). The walls are connected with cramps and dowels at certain intervals so that it works as a single section against horizontal and vertical loads. To characterize the in-plane behavior of the proposed wall, compressive, triplet, and diagonal compression tests were conducted to investigate the compressive strength, shear strength, modulus of elasticity, stiffness, ductility, and energy absorption of the wall.

The paper is well written and organized. The topic is of interest and timely. The wide experimental campaign supports the scope of the paper and the conclusions.

The reviewer has only few minor comments.

Equation 1 (page 11) and Equation 2 (page 12) The brackets are missing after the division slash.

Page 15. The compressive strength of the specimens with cramps on the stone surface without carving a channel is much lower than that of the only stone. It is possible to avoid this effect by increasing a little the mortar thickness?

Author Response

Comments from Reviewer 3

Comments and Suggestions for Authors: The paper presents and discusses the experimental assessment of the in-plane mechanical behavior of a multi-leaf stone masonry wall built from cut stone and reinforced with metal connectors (cramps and dowels). The walls are connected with cramps and dowels at certain intervals so that it works as a single section against horizontal and vertical loads. To characterize the in-plane behavior of the proposed wall, compressive, triplet, and diagonal compression tests were conducted to investigate the compressive strength, shear strength, modulus of elasticity, stiffness, ductility, and energy absorption of the wall.

The paper is well written and organized. The topic is of interest and timely. The wide experimental campaign supports the scope of the paper and the conclusions.

Response: Thank you for taking the time to review our article. 

Comment 1: Equation 1 (page 11) and Equation 2 (page 12) The brackets are missing after the division slash.

 Response: As suggested by the reviewer, Equation 1 and Equation 2 have been corrected.

Comment 2: Page 15. The compressive strength of the specimens with cramps on the stone surface without carving a channel is much lower than that of the only stone. It is possible to avoid this effect by increasing a little the mortar thickness?

 Response: Thank you for this suggestion. It would have been interesting to explore this aspect. We are planning to carry out an extensive experimental assessment of the out-of-plane behavior of the proposed wall. Then, we would like to explore the aspect you suggested. Thank you for your contribution.