Experimental Study on Dynamics of Wooden House Wall Panels with Different Thermal Isolation
Round 1
Reviewer 1 Report
This paper presents an interesting study on the seismic performance of wooden house wall panels with thermal isolation that is made of mineral wool and polyurethane foam. Experiments were conducted to evaluate the seismic performance of the wall panels. The research topic is important. However, the manuscript must be improved. Following are some detailed comments and suggestions that might be useful for further improvement.
The authors briefly introduced some recent advances in improving the seismic resistance of structures, including using fibers as reinforcement. This is good. However, the introduction must be improved. Please clarify the novelty of this study, and why this study is important. Also, please be aware of some of the most recent progress, for instance: Li, X., Wang, J., Bao, Y., Chen, G. (2017) “Cyclic behavior of damaged reinforced concrete columns repaired with high-performance fiber-reinforced cementitious composite.” Engineering Structures, 136, 26–35. The experiment of the wall panels is important for this study. However, a lot of information is missing, and the figures are unclear. It is unclear how the specimens were designed and fabricated. Also, it is unclear how the specimens were instrumented and tested. I do not know how to read the figures. Extra figures are included. Please consider removing the unnecessary figures, such as Figures 11 and 12. Those figures are not informative. Please improve the figures that you need to include. The font size is too small to read in Figures 7-10. Please modify. What was your loading protocol? Please clarify. Please elaborate the measurement accuracy of the used sensors. The load-displacement curves in Figures 14 and 16 are not smooth, which is unusual. Please explain. How did you determine the stiffness and damping ratio in Tables 4 and 5? What do you mean by the arrows in Figure 15? There is a lack of in-depth analysis. What did you learn from this study? What key findings did you obtain? The language is readable but should be further improved.
Author Response
Dear Editor and Reviewer,
We highly appreciate the detailed valuable comments of the Reviewer concerning our manuscript. The suggestions were very helpful for us and we incorporated them in the revised version of the paper.As below, we would like to clarify some of the points raised by the Reviewer, and we hope the Reviewer and the Editor will be satisfied with our responses to the comments and the revisions to the original manuscript. Also, the modifications have been highlighted (using yellow colour) in the body of the revised version of the paper.
Itemized Responses:
Review 1
This paper presents an interesting study on the seismic performance of wooden house wall panels with thermal isolation that is made of mineral wool and polyurethane foam. Experiments were conducted to evaluate the seismic performance of the wall panels. The research topic is important. However, the manuscript must be improved. Following are some detailed comments and suggestions that might be useful for further improvement.
The authors briefly introduced some recent advances in improving the seismic resistance of structures, including using fibers as reinforcement. This is good. However, the introduction must be improved. Please clarify the novelty of this study, and why this study is important.
Response: Considering the suggestion of the Reviewer, the following fragment of the manuscript (Introduction) has been improved (page 2):
Unlike other elements of a wooden frame building, the results of research focused on thermal insulation are relatively limited. One of a few examples concerns the study on the seismic efficiency of structural insulated panels [27]. The behaviour of wood-composite laminated frames under the dynamic loads has also been investigated [28].
There are some numerical analyses available, which indicate that thermal insulation of the wooden frame building can substantially affect the dynamic resistance of the whole structure (see [29,30] for example). The results of these analyses show that using the polyurethane foam instead of mineral wool for the in-wall insulation of a wood-frame building leads to the increase in the rigidity of the whole structure. This effect is obtained mainly due to full connection between the polyurethane foamand the surrounding wooden elements and a lack of such connection in the case of mineral wool. It has been found that the increase in the rigidity of the building insulated with the polyurethane foam leads to the substantial reduction in the structural response under different seismic excitations [30]. It should be added that, in construction, polyurethane foam is known only as an insulation material. It turns out that this insulation material can also effectively stiffen the whole structure and improve its dynamic resistance substantially. However, the results of the numerical analyses described in [29,30] have to be verified experimentally.
Therefore, the aim of the present study is to show the results of experimental tests focused on dynamic response of wall panels of the wooden frame building with thermal isolation made of traditional mineral wool and polyurethane foam. Firstly, the static and the Dynamic Mechanical Analysis (DMA) tests have been conducted so as to determine the basic thermomechanical properties of the analyzed isolation materials. Then, the elements of exterior walls with two types of thermal insulation have been tested under harmonic excitation for different amplitudes of displacement.
Moreover, the following papers have been added in the list of references:
Donovan T., Memari M. Feasibility study of determination of seismic performance factors for structural insulated panels. Journal of Architectural Engineering 2015, 21, 1-9.
Kasal B., Heiduschke A., Haller P. Analysis of wood-composite laminated frames under dynamic loads – analytical models and model validation. Part I: Connection Model. Progress in Structural Engineering and Materials2006, 8, 103-110.
Also, please be aware of some of the most recent progress, for instance: Li, X., Wang, J., Bao, Y., Chen, G. (2017) “Cyclic behavior of damaged reinforced concrete columns repaired with high-performance fiber-reinforced cementitious composite.” Engineering Structures, 136, 26–35.
Response: According to the Reviewer's suggestion, new literature items, including the suggested one,have been added:
Li X., Wang J., Bao Y., Chen G. Cyclic behavior of damaged reinforced concrete columns repaired with high-performance fiber-reinforced cementitious composite. Engineering Structures2017, 136, 26–35.
Teng J.G.; Yu T.; Fernando D. Strengthening of steel structures with fiber-reinforced polymer composites. Journal of Construction Steel Research2012, 78, 131-143. Linghoff D.; Haghani R.; Al-Emrani M. Carbon-fibre composites for strengthening steel structures. Thin-Walled Structures2009, 47, 1048-1058. Kim D.H.; Moon D. Y.; Kim M.K.; Zi G.; Roh H. Experimental test and seismic performance of partial precast concrete segmental bridge column with cast-in-place base. Engineering Structures 2015, 100, 178-188. Shrive N. G. The use of fibre reinforced polymers to improve seismic resistance of masonry. Construction and Building Materials2006, 20, 269-277.
The above references have been cited in the following sentences:
page 1:
Methods of strengthening these structures, mainly constructed of reinforced concrete or steel frame, for example using the fiber-reinforced cementitious composite [4], are subjected to many tests, including the experimental and numerical ones [5-9].
The experiment of the wall panels is important for this study. However, a lot of information is missing, and the figures are unclear. It is unclear how the specimens were designed and fabricated. Also, it is unclear how the specimens were instrumented and tested.
Response: Considering the Reviewer's suggestion, the following information has been added:
page 2:
Polyurethane foam static compression tests were carried out on a number of cylindrical samples with a cross-section area of 18 mm2 and a height of 20 mm (Figure 1). Material samples were taken directly from the wall panels of the wooden frame building, which were previously tested experimentally (see section 4).
Page3:
Polyurethane foam static tension tests were carried out on a number of samples with a cross-section of 10 mm2 and a height of 80 mm (Figure 3). Material samples were taken directly from the wall panels of the wooden frame building, which were previously tested experimentally (see section 4).
pages 10-11:
For the purpose of this study, a typical wooden frame house wall panels were prepared (see Figure 17). Using a modulus of 60 cm for the frame elements, each of the panel was constructed with C24 wood and it was filled either with mineral wool or polyurethane foam and covered on both sides by OSB3 sheaths. The dimensions of each panel were equal to: length - 129 cm and width - 60 cm. Wooden skeleton elements (posts and cap) were connected to each other using standard screws. Screws were also applied to connect the OSB3 sheaths and the skeleton itself. In this case, the connectors were used at the corners and along the length of the board at intervals of 10 cm. Since the skeleton was covered by the single OSB3 boards on both sides (see Figure 17), there was no need to apply any connectors in the middle of the element.
page 11:
During experimental tests, both models were subjected to harmonic excitations. The tests were carried out for the frequency of 2 Hz for different values of displacement amplitude.The exerted force was recorded by a force sensor KMM40, working in the range of up to 50 kN and the accuracy class of 0.5 (according to the producer’s specification). The resulting displacement was measured by a laser displacement sensor optoNCDT 1302, working in the range of ±100 mmwith the micrometre accuracy (according to the producer’s specification). The force sensor was mounted at the end of the actuator’s moveable rod, while the displacement sensor was installed at the actuator's shaft (see Figure 17).
I do not know how to read the figures. Extra figures are included. Please consider removing the unnecessary figures, such as Figures 11 and 12. Those figures are not informative. Please improve the figures that you need to include. The fontsize is too small to read in Figures 7-10. Please modify.
Response: Considering the Reviewer's suggestion, Figures 11 and 12 have been deleted,Figures 7 and 8have been divided into eight figures, enlarged and improved, Figures 9 and 10 (Figures 15 and 16 in the revised version of the paper) have been enlarged:
page 6,7,8,9:
Figure 7. Results of DMA tests for mineral wool for frequency 1 Hz.
Figure 8. Results of DMA tests for mineral wool for frequency 10 Hz.
Figure 9. Results of DMA tests for mineral wool for frequency 20 Hz.
Figure 10. Results of DMA tests for mineral wool - comparison for all frequencies analyzed.
Figure 11. Results of DMA tests for polyurethane foam for frequency 1 Hz.
Figure 12. Results of DMA tests for polyurethane foam for frequency 10 Hz.
Figure 13. Results of DMA tests for polyurethane foam for frequency 20 Hz.
Figure 14. Results of DMA tests for polyurethane foam - comparison for all frequencies analyzed.
page 10:
Figure 15. Sketch of experimental setup (side view of the main frame).
Figure 16. Sketch of experimental setup (top view of the main frame).
Moreover, the following comments have been added by extending the manuscript with the additional paragraph:
page 5:
The results of DMA tests (see Figures 7-14) clearly show that the values of storage and loss moduli are substantially larger for the polyurethane foam, as compared to the mineral wool. In particular, it can be seen from Table 2 and Table 3 that, for the case of the temperature of 20° C, the storage modulus of the polyurethane foam is larger by as much as 91.7%, 76.8% and 77.4% for the frequency of 1 Hz, 10 Hz and 20 Hz, respectively. In turn, the loss modulus of the polyurethane foam is bigger than the corresponding value for the mineral wool by as much as 61.4%, 74.5% and 88.3% for the frequency of 1 Hz, 10 Hz and 20 Hz, respectively. This indicates that the polyurethane foam, as a material, is able to dissipate a larger amount of energy. Therefore, comparing it to the mineral wool, it is a material with much better absorption capabilities related directly to the energy absorption.
What was your loading protocol? Please clarify. Please elaborate the measurement accuracy of the used sensors.
Response: According to the Reviewer's suggestion,information about the loading protocol and accuracy of the sensors has been added:
page 4:
Loading protocol was taken according to standards ASTM D4092 and DIN 53440.
page 11:
The exerted force was recorded by a force sensor KMM40, working in the range of up to 50 kN and the accuracy class of 0.5 (according to the producer’s specification). The resulting displacement was measured by a laser displacement sensor optoNCDT 1302, working in the range of ±100 mmwith the micrometre accuracy (according to the producer’s specification).
The load-displacement curves in Figures 14 and 16 are not smooth, which is unusual. Please explain.
Response: Well, we would like to apologize for the situation and explain that the load-displacement curves in Figures 14 and 16 (Figures 19 and 21 in the revised version of the paper) are unfortunately not smooth because of the differences in the sampling frequencies of sensors and measuring equipment. We believe that applying any numerical smoothing procedure would not be appropriate here, since it could somehow influence the results. Therefore we think that it is better to leave the figures untouched. We strongly believe that our explanation can be accepted by the Reviewer.
How did you determine the stiffness and damping ratio in Tables 4 and 5?
Response: Considering the Reviewer's remark, the following explanation has been added:
page 11:
On this basis, the stiffness,,and damping ratio, , have been calculated using the following formulas (see also Figure 19) [32]:
(1)
(2)
Figure 19. Hysteresis loop.
What do you mean by the arrows in Figure 15?
Response: Following the remark,the explanation has been added in the figure caption:
page 13:
Figure 20. Panel filled with mineral wool after the tests (red arrows indicate the places of the largest destruction)
There is a lack of in-depth analysis. What did you learn from this study? What key findings did you obtain?
Response: According to the Reviewer's remark, the following paragraph has been added at the end of Conclusions:
page 16:
Taking into account the above arguments, it is recommended to apply the polyurethane foam not only as the isolation material but also to increase the dynamic resistance of skeletal wooden structures. It can be used for newly constructed houses. It can also be applied in the case of existing wood-frame buildings since replacing the mineral wool with the polyurethane foam is relatively easy. The results of the investigation shown in this paper indicate that such an approach would be a very effective method of increasing the dynamic resistance of existing structures. Moreover, the polyurethane foam is a material widely available and increasingly used in civil engineering. It is also a relatively inexpensive and durable material compared to other insulation materials, which also makes it very attractive.
The language is readable but should be further improved.
Response: According to the Reviewer's suggestion, the language has been improved.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this paper, the dynamic properties of wooden wall panels with PU foam insulation are evaluated. Similar findings have already been published in difference papers already (details in the appended comments). The research significance is low as the paper lacks novelty. Experimental and results sections are also very weak missing out important information on the testing parameters.
Details are appended below:
Abstract is almost 300 words and as such unnecessarily long. This makes a potential reader bored. The aim of the Abstract I to attract the readers. It must be condensed. Please remove redundant details. Be precise and brief. Strain is a unitless quantity. Why the negative sign is mentioned in Figure 2 and Figure 4? The number of samples and related statistical information is not given and hence the confidence level of the test results cannot be ascertained. Much of the data is similar in other papers published by the same Authors (please see the attached files). New information presented in this paper is very little, and as such the justification for its publishing as a journal article is very weak. Line 44; what kind of “numerical tests” are there to which the strengthened RCC or steel frames are subjected? The paper needs thorough language editing and reviewing. There are many instances where the reader is unable to comprehend the intended meaning. E.g. Line 44-47; “On the other hand, in the field of seismic resistance of masonry structures, one of the main roles is played by the accepted design criteria, their experimental and theoretical foundations, as well as their consequences in practice [6]”, Line 122 “The exemplary results”, etc. are unclear. Please rephrase all such issues. Rather, I would highly suggest to get the paper proofread by a native English language speaker expert in this field.. Line 47; it is advisable to use the term “retrofitting” instead of “repairing damages”. Line 64-65; “Thermal insulation affects the lifespan of the building, its durability and defines the energy class.”. Please cite relevant reference here justifying the aforementioned statement. In the Introduction, the Authors claim that “The influence of wall insulation has not been thoroughly experimentally studied from the point of view of seismic/dynamic resistance and strength”, whereas it’s not true. The aforementioned studies have already been conducted and published in: Wojciech Migda, Marcin Szczepański, Robert Jankowski. "Increasing the Seismic Resistance of Wood-frame Buildings by Applying PU Foam as Thermal Insulation", Periodica Polytechnica Civil Engineering, 2019 Marcin Szczepanski, Wojciech Migda, Robert Jankowski. "CONSTRUCTION TECHNOLOGY OF TIMBER-FRAME HOUSES RESISTANT TO DYNAMIC LOADS – STUDY ON MODELS OF EXTERIOR WALLS", Advances in Science and Technology Research Journal, 2015 Marcin Szczepański, Wojciech Migda. "Timber frame houses resistant to dynamic loads - seismic analysis", MATEC Web of Conferences, 2018 Testing methodologies are not well explained in the manuscript. please improve this section. The quality of Figure 7 and Figure 8 is inadequate. Please revise. The terms loss modulus and storage modulus must be defined before these results are reported in the paper.
Comments for author File: Comments.pdf
Author Response
Dear Editor and Reviewer,
We highly appreciate the detailed valuable comments of the Reviewer concerning our manuscript. The suggestions were very helpful for us and we incorporated them in the revised version of the paper. As below, we would like to clarify some of the points raised by the Reviewer, and we hope the Reviewer and the Editor will be satisfied with our responses to the comments and the revisions to the original manuscript. Also, the modifications have been highlighted (using yellow colour) in the body of the revised version of the paper.
Itemized Responses:
Review 2
In this paper, the dynamic properties of wooden wall panels with PU foam insulation are evaluated. Similar findings have already been published in difference papers already (details in the appended comments). The research significance is low as the paper lacks novelty. Experimental and resultssectionsarealsoveryweak missing out importantinformation on the testingparameters. Details are appended below:
Abstract is almost 300 words and as such unnecessarily long. This makes a potential reader bored. The aim of the Abstract I to attract the readers. It must be condensed. Please remove redundant details. Be precise and brief.
Response: Considering the suggestion of the Reviewer, the following fragment of the manuscript (Abstract) has been shortened (page 1):
Abstract: Wood frame buildings are very popular in regions that are exposed to different dynamic excitations including earthquakes. Therefore, the seismic resistance of them is really important in order to prevent structural damages and human losses. The aim of the present paper is to show the results of experimental tests focused on dynamic response of wall panels of the wooden frame building with thermal isolation made of mineral wool and polyurethane foam. Firstly, the static and the DynamicMechanical Analysis (DMA) tests have been conducted so as to determine the basic thermomechanical properties of the analyzed isolation materials. Then, the elements of exterior walls with two types of thermal insulation have been tested under harmonic excitation for different amplitudes of displacement. The results of the static material tests indicate that the polyurethane foam behaves in a highly non-linear way both during compression and tension. Moreover, the results of the DMA tests show that the storage and loss moduli of the polyurethane foam are significantly larger in relation to the values obtained for the mineral wool. The results of the dynamic tests on wall panels show that the use of polyurethane foam as thermal isolation leads to the substantial increase in stiffness and damping properties, as compared to the case when the mineral wood is used.
Strainis a unitless quantity. Why the negative signis mentioned in Figure 2 and Figure 4?
Response: Well, our intension to use the term ‘[-]’ after the word ‘Strain’ describing the horizontal axis was to indicate that strain is a unitless quantity (it does not have any units). We believe that it could be a kind of misunderstanding and could be interpreted as a negative sign of strain, which is not the case. Therefore, considering the Reviewer's remark, the term ‘[-]’ has been deleted from Figure 2 and Figure 4.
page 3:
Figure 2. Relation between stress and strain for polyurethane foam subjected to static compression.
page 4:
Figure 4. Relation between stress and strain for polyurethane foam subjected to static tension.
The number of samples and related statistical information is not given and hence the confidence level of the test results cannot be ascertained.
Response: Considering the remark of the Reviewer, the following improvements have been introduced in the manuscript:
page 2-3:
Polyurethane foam static compression tests were carried out on a number of cylindrical samples with a cross-section area of 18 mm2 and a height of 20 mm (Figure 1). Material samples were taken directly from the wall panels of the wooden frame building, which were previously tested experimentally (see section 4). The representative results of the static compression tests, in the form of relation between stress and strain, are shown in Figure 2. It should be added that nearly identical curves were obtained for all of the tested samples and the scatter of the results was negligibly small.
page 3:
Polyurethane foam static tension tests were carried out on a number of samples with a cross-section of 10 mm2 and a height of 80 mm (Figure 3). Material samples were taken directly from the wall panels of the wooden frame building, which were previously tested experimentally (see section 4). The representative results of the static tension tests, in the form of relation between stress and strain, are shown in Figure 4. It should be added that nearly identical curves were obtained for all of the tested samples and the scatter of the results was negligibly small.
Much of the data is similar in other papers published by the same Authors (please see the attached files). New information presented in this paper is very little, and as such the justification for its publishing as a journal article is very weak.
Response: Considering the Reviewer's suggestion, the following fragment of manuscript (Introduction) has been improved:
page 2:
Unlike other elements of a wooden frame building, the results of research focused on thermal insulation are relatively limited. One of a few examples concerns the study on the seismic efficiency of structural insulated panels [27]. The behaviour of wood-composite laminated frames under the dynamic loads has also been investigated [28].
There are some numerical analyses available, which indicate that thermal insulation of the wooden frame building can substantially affect the dynamic resistance of the whole structure (see [29,30] for example). The results of these analyses show that using the polyurethane foam instead of mineral wool for the in-wall insulation of a wood-frame building leads to the increase in the rigidity of the whole structure. This effect is obtained mainly due to full connection between the polyurethane foamand the surrounding wooden elements and a lack of such connection in the case of mineral wool. It has been found that the increase in the rigidity of the building insulated with the polyurethane foam leads to the substantial reduction in the structural response under different seismic excitations [30]. It should be added that, in construction, polyurethane foam is known only as an insulation material. It turns out that this insulation material can also effectively stiffen the whole structure and improve its dynamic resistance substantially. However, the results of the numerical analyses described in [29,30] have to be verified experimentally.
Therefore, the aim of the present study is to show the results of experimental tests focused on dynamic response of wall panels of the wooden frame building with thermal isolation made of traditional mineral wool and polyurethane foam. Firstly, the static and the Dynamic Mechanical Analysis (DMA) tests have been conducted so as to determine the basic thermomechanical properties of the analyzed isolation materials. Then, the elements of exterior walls with two types of thermal insulation have been tested under harmonic excitation for different amplitudes of displacement.
Moreover, the following papers have been added in the list of references:
Donovan T., Memari M. Feasibility study of determination of seismic performance factors for structural insulated panels. Journal of Architectural Engineering 2015, 21, 1-9.
Kasal B., Heiduschke A., Haller P. Analysis of wood-composite laminated frames under dynamic loads – analytical models and model validation. Part I: Connection Model. Progress in Structural Engineering and Materials2006, 8, 103-110.
Line 44; what kind of “numerical tests” are there to which the strengthened RCC or steel framesare subjected?
Response: Considering the Reviewer's remark, the following fragment of manuscript has been improved:
page 1:
Methods of strengthening these structures, mainly constructed of reinforced concrete or steel frame, for example using the fiber-reinforced cementitious composite [4], are subjected to many tests, including the experimental and numerical ones [5-9].
Moreover, the following papers have been added to the list of references:
Li X., Wang J., Bao Y., Chen G. Cyclic behavior of damaged reinforced concrete columns repaired with high-performance fiber-reinforced cementitious composite. Engineering Structures2017, 136, 26–35. Teng J.G.; Yu T.; Fernando D. Strengthening of steel structures with fiber-reinforced polymer composites. Journal of Construction Steel Research2012, 78, 131-143. Linghoff D.; Haghani R.; Al-Emrani M. Carbon-fibre composites for strengthening steel structures. Thin-Walled Structures2009, 47, 1048-1058. Kim D.H.; Moon D. Y.; Kim M.K.; Zi G.; Roh H. Experimental test and seismic performance of partial precast concrete segmental bridge column with cast-in-place base. Engineering Structures 2015, 100, 178-188. Shrive N. G. The use of fibre reinforced polymers to improve seismic resistance of masonry. Construction and Building Materials2006, 20, 269-277.
The paper needs thorough language editing and reviewing. There are many instances where the reader is unable to comprehend the intended meaning. E.g. Line 44-47; “On the other hand, in the field of seismic resistance of masonry structures, one of the main roles is played by the accepted design criteria, their experimental and theoretical foundations, as well as their consequences in practice [6]”, Line 122 “The exemplary results”, etc. are unclear. Please rephraseall such issues. Rather, I would highly suggest to get the paper proof read by a native English language speaker expert in this field.. Line 47; it is advisable to use the term “retrofitting” instead of “repairingdamages”. Line 64-65;
Response: Following the Reviewer's suggestion, a number of sentences have been improved, other have been deleted or exchanged, i.e.:
page 1:
Methods of strengthening these structures, mainly constructed of reinforced concrete or steel frame, for example using the fiber-reinforced cementitious composite [4], are subjected to many tests, including the experimental and numerical ones [5-9].On the other hand, in the field of seismic resistance of masonry structures, one of the main roles is played by the accepted design criteria, their experimental and theoretical foundations, as well as their consequences in practice [8,9]. There are many methods of retrofitting of masonry structures, including for example, methods for strengthening cracked walls using high-strength composite materials and a rigid adhesive with low deformability [10-12].
page 5:
The results of DMA tests (compression tests) are presented in Figures 7-14 and are summarized in Tables 2,3.
page 11:
The results, in the form of representative hysteresis loops showing the relation between force and displacement, are presented in Figure 14.
page 14:
The results, in the form of representative hysteresis loops, are presented in Figure 21
“Thermal insulation affects the lifespan of the building, its durability and defines the energyclass. ”Please cite relevant reference here justifying the aforementionedstatement.
Response: Following to the Reviewer's suggestion,the relevant publication has been cited:
Nitka W.My Wooden House. National Forest Information Centre, Warsaw 2010.
page 2:
Thermal insulation affects the lifespan of the building, its durability and defines the energy class [26].
In the Introduction, the Authors claim that “The influence of wall insulation has not been thoroughly experimentally studied from the point of view of seismic/dynamic resistance and strength”, whereas it’s not true. The aforementionedstudieshave already been conducted and published in: Wojciech Migda, Marcin Szczepański, Robert Jankowski. "Increasing the SeismicResistance of Wood-frame Buildings by Applying PU Foam as Thermal Insulation", Periodica Polytechnica Civil Engineering, 2019 Marcin Szczepanski, Wojciech Migda, Robert Jankowski. "CONSTRUCTION TECHNOLOGY OF TIMBER-FRAME HOUSES RESISTANT TO DYNAMIC LOADS – STUDY ON MODELS OF EXTERIOR WALLS", Advances in Science and Technology ResearchJournal, 2015 Marcin Szczepański, Wojciech Migda. "Timberframehousesresistant to dynamicloads – seismicanalysis", MATEC Web of Conferences, 2018
Response: Considering the Reviewer's suggestion, the following fragment of manuscript (Introduction) has been improved (see also our response to point 4 of this document):
page 2:
There are some numerical analyses available, which indicate that thermal insulation of the wooden frame building can substantially affect the dynamic resistance of the whole structure (see [29,30] for example). The results of these analyses show that using the polyurethane foam instead of mineral wool for the in-wall insulation of a wood-frame building leads to the increase in the rigidity of the whole structure. This effect is obtained mainly due to full connection between the polyurethane foamand the surrounding wooden elements and a lack of such connection in the case of mineral wool. It has been found that the increase in the rigidity of the building insulated with the polyurethane foam leads to the substantial reduction in the structural response under different seismic excitations [30]. It should be added that, in construction, polyurethane foam is known only as an insulation material. It turns out that this insulation material can also effectively stiffen the whole structure and improve its dynamic resistance substantially. However, the results of the numerical analyses described in [29,30] have to be verified experimentally.
Therefore, the aim of the present study is to show the results of experimental tests focused on dynamic response of wall panels of the wooden frame building with thermal isolation made of traditional mineral wool and polyurethane foam. Firstly, the static and the Dynamic Mechanical Analysis (DMA) tests have been conducted so as to determine the basic thermomechanical properties of the analyzed isolation materials. Then, the elements of exterior walls with two types of thermal insulation have been tested under harmonic excitation for different amplitudes of displacement.
Testingmethodologiesare not wellexplained in the manuscript. please improve this section.
Response: Considering the remark of the Reviewer, the following explanations have been added in the manuscript:
page 4:
In the second stage of investigation, dynamicmechanicalspectroscopytests were performed using the DMA Q800 Instruments apparatus (Figures 5,6). The parameters of tests are presented in Table 1. It should be underlined that the range of temperatures and frequencies corresponded to real conditions. The loadingprotocol was takenaccording to standards ASTM D4092 and DIN 53440.
page 11:
During experimental tests, both models were subjected to harmonic excitations. The tests were carried out for the frequency of 2 Hz for different values of displacement amplitude.The exerted force was recorded by a force sensor KMM40, working in the range of up to 50 kN and the accuracy class of 0.5 (according to the producer’s specification). The resulting displacement was measured by a laser displacement sensor optoNCDT 1302, working in the range of ±100 mmwith the micrometre accuracy (according to the producer’s specification). The force sensor was mounted at the end of the actuator’s moveable rod, while the displacement sensor was installed at the actuator's shaft (see Figure 17).
The quality of Figure 7 and Figure 8 is inadequate. Please revise.
Response: Considering the Reviewer's suggestion, Figure 7 and Figure 8 have been divided into eight figures, enlarged and improved:
page 6,7,8,9:
Figure 7. Results of DMA tests for mineral wool for frequency 1 Hz.
Figure 8. Results of DMA tests for mineral wool for frequency 10 Hz.
Figure 9. Results of DMA tests for mineral wool for frequency 20 Hz.
Figure 10. Results of DMA tests for mineral wool - comparison for all frequencies analyzed.
Figure 11. Results of DMA tests for polyurethane foam for frequency 1 Hz.
Figure 12. Results of DMA tests for polyurethane foam for frequency 10 Hz.
Figure 13. Results of DMA tests for polyurethane foam for frequency 20 Hz.
Figure 14. Results of DMA tests for polyurethane foam - comparison for all frequencies analyzed.
Moreover, the following comments concerning the results shown in the above figures have been added by extending the manuscript with the additional paragraph:
page 5:
The results of DMA tests (see Figures 7-14) clearly show that the values of storage and loss moduli are substantially larger for the polyurethane foam, as compared to the mineral wool. In particular, it can be seen from Table 2 and Table 3 that, for the case of the temperature of 20° C, the storage modulus of the polyurethane foam is larger by as much as 91.7%, 76.8% and 77.4% for the frequency of 1 Hz, 10 Hz and 20 Hz, respectively. In turn, the loss modulus of the polyurethane foam is bigger than the corresponding value for the mineral wool by as much as 61.4%, 74.5% and 88.3% for the frequency of 1 Hz, 10 Hz and 20 Hz, respectively. This indicates that the polyurethane foam, as a material, is able to dissipate a larger amount of energy. Therefore, comparing it to the mineral wool, it is a material with much better absorption capabilities related directly to the energy absorption.
The terms loss modulus and storage modulus must be defined before these results are reported in the paper.
Response: Following to the Reviewer's suggestion, the storage modulus and loss modulus have been defined:
page 5:
The results show the change of storage modulus, loss modulus and loss factor (tan delta) as the temperature increases. It should be mentioned that the storage modulus measures the stored energy in the material due to the applied strain and it represents the elastic portion of energy [31]. On the other hand, the loss modulus measures the energy dissipated through molecular motion and it represents the viscous portion of energy. The ratio of the loss modulus to storage modulus, which can be calculated as the tangent of the phase angle, is termed as the loss factor[31].
Moreover, the following paper has also been added to the list of references:
Kumar, A.; Gupta, R.K. Fundamentals of Polymer Engineering. Marcel Dekker, New York, USA 2003.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper presents experimental results of the role thermal isolation layer on the shear behaviour timber framed shear wall. The topic is of interest for design of seismic resistant timber building. However, the paper cannot be accepted for publication if the following comment are not addressed.
In the introduction the authors should cite more recent works on the seismic behaviour of light timber walls. Several papers dealing with the role of connections, with the lateral deformation of the walls and with q-factor may be added (Materials & Structures vol. 42, 2009 - JSE-ASCE vol. 136 n 3, 2010 - JSE-ASCE vol. 136 n 10, 2010, Construction and Building Materials vol.80, 2015; Engineering Structures vol. 100, 2015). When the material properties of the polyurethane are evaluated the authors have to add information on the number of specimens tested, test results of each specimens, mean value and scatter of test results. Which standards were used to perform the tests? The meaning of storage modulus and loss modulus have to be defined. Figure 7 and Figure 8 are not clear. The results of these figures have to be commented. Details on the connections between the wooden panel and the studs of the wall have to be added, as well as the material properties of the wooden elements. Material properties are missing (screw, OSB, timber stud)
Kind Regards
Author Response
Dear Editor and Reviewer,
We highly appreciate the detailed valuable comments of the Reviewer concerning our manuscript. The suggestions were very helpful for us and we incorporated all of them in the revised version of the paper. As below, we would like to clarify some of the points raised by the Reviewer, and we hope the Reviewer and the Editor will be satisfied with our responses to the comments and the revisions to the original manuscript. Also, the modifications have been highlighted (using yellow colour) in the body of the revised version of the paper.
Itemized Responses:
Review 3
The paper presents experimental results of the role thermal isolation layer on the shear behaviour timber framed shear wall. The topicis of interest for design of seismic resistant timber building. However, the papercannot be accepted for publicationif the following commentare not addressed.
In the introduction the authors should cite more recent works on the seismic behaviour of light timber walls. Several papers dealing with the role of connections, with the lateral deformation of the walls and with q-factormay be added. (Materials &Structures vol. 42, 2009 - JSE-ASCE vol. 136 n 3, 2010 - JSE-ASCE vol. 136 n 10, 2010, Construction and Building Materials vol.80, 2015; Engineering Structures vol. 100, 2015).
Response: Followingthe Reviewer's suggestion, six papers have been added to the list of references:
Filiatrault A.; Christovasilis I.P.; Wanitkorkul A.; Wan de Lindt J.W. Experimental seismic response of a full-scale light-frame wood building. Journal of Structural Engineering2010, 136 (3), 246-254. González Fueyo, J.L.; Dominguez, M.; Cabezas, J.A.; Rubio, M.P. Design of connections with metal dowel-type fasteners in double shear. Materials and Structures 2009, 42(3), 385-397.
Echavarría, C.; Salenikovich, A. Analytical model for predicting brittle failures of bolted timber joints. Materials and Structures 2009, 42(7), 867-875.
Miller, J.F.; Schmidt, R.J.; Bulleit, W.M. New yield model for wood dowel connections. Journal of Structural Engineering 2010, 136(10), 1255-1261.
Germano, F.; Metelli, G.; Giuriani, E. Experimental results on the role of sheathing-to-frame and base connections of a European timber framed shear wall. Construction and Building Materials 2015, 80, 315-328.
Gattesco, N.; Boem, I. Seismic performances and behavior factor of post-and-beam timber buildings braced with nailed shear walls. Engineering Structures 2015, 100, 674-685.
The above papers have been cited in the following fragment of manuscript (Introduction):
page 2:
The research work includes both experimental investigations, including the shaking table tests (see [16,17], as well as numerical analyses. A number of studies have been focused on structural connectors, anchor connections and special flat bars and angles, the use of which results in stiffening of the whole structure and increasing its seismic resistance [18-20]. The role of connections, with the lateral deformation of the light walls and with q-factor, has also been investigated (see [21-25] for example).
When the material properties of the polyurethane are evaluated the authors have to add information on the number of specimens tested, test results of each specimens, meanvalue and scatter of test results.
Response: Considering the remark of the Reviewer, the following information has been added in the manuscript:
page 2-3:
Polyurethane foam static compression tests were carried out on a number of cylindrical samples with a cross-section area of 18 mm2 and a height of 20 mm (Figure 1). Material samples were taken directly from the wall panels of the wooden frame building, which were previously tested experimentally (see section 4). The representative results of the static compression tests, in the form of relation between stress and strain, are shown in Figure 2. It should be added that nearly identical curves were obtained for all of the tested samples and the scatter of the results was negligibly small.
page 3:
Polyurethane foam static tension tests were carried out on a number of samples with a cross-section of 10 mm2 and a height of 80 mm (Figure 3). Material samples were taken directly from the wall panels of the wooden frame building, which were previously tested experimentally (see section 4). The representative results of the static tension tests, in the form of relation between stress and strain, are shown in Figure 4. It should be added that nearly identical curves were obtained for all of the tested samples and the scatter of the results was negligibly small.
Which standards were used to perform the tests?
Response: Considering the remark of the Reviewer, the following information has been added in the manuscript:
page 4:
The loading protocol was taken according to standards ASTM D4092 and DIN 53440.
The meaning of storage modulus and loss modulus have to be defined.
Response: Following to the Reviewer's suggestion, the storage modulus and loss modulus have been defined:
page 5:
The results show the change of storage modulus, loss modulus and loss factor (tan delta) as the temperature increases. It should be mentioned that the storage modulus measures the stored energy in the material due to the applied strain and it represents the elastic portion of energy [31]. On the other hand, the loss modulus measures the energy dissipated through molecular motion and it represents the viscous portion of energy. The ratio of the loss modulus to storage modulus, which can be calculated as the tangent of the phase angle, is termed as the loss factor[31].
Moreover, the following paper has also been added to the list of references:
Kumar, A.; Gupta, R.K. Fundamentals of Polymer Engineering. Marcel Dekker, New York, USA 2003.
Figure 7 and Figure 8 are not clear. The results of these figures have to be commented.
Response:Considering the Reviewer's suggestion, Figure 7 and Figure 8 have beendivided into eight figures, enlarged and improved:page 6,7,8,9:
Figure 7. Results of DMA tests for mineral wool for frequency 1 Hz.
Figure 8. Results of DMA tests for mineral wool for frequency 10 Hz.
Figure 9. Results of DMA tests for mineral wool for frequency 20 Hz.
Figure 10. Results of DMA tests for mineral wool - comparison for all frequencies analyzed.
Figure 11. Results of DMA tests for polyurethane foam for frequency 1 Hz.
Figure 12. Results of DMA tests for polyurethane foam for frequency 10 Hz.
Figure 13. Results of DMA tests for polyurethane foam for frequency 20 Hz.
Figure 14. Results of DMA tests for polyurethane foam - comparison for all frequencies analyzed.
Moreover, the following comments concerning the results shown in the above figures have been added by extending the manuscript with the additional paragraph:
page 5:
The results of DMA tests (see Figures 7-14) clearly show that the values of storage and loss moduli are substantially larger for the polyurethane foam, as compared to the mineral wool. In particular, it can be seen from Table 2 and Table 3 that, for the case of the temperature of 20° C, the storage modulus of the polyurethane foam is larger by as much as 91.7%, 76.8% and 77.4% for the frequency of 1 Hz, 10 Hz and 20 Hz, respectively. In turn, the loss modulus of the polyurethane foam is bigger than the corresponding value for the mineral wool by as much as 61.4%, 74.5% and 88.3% for the frequency of 1 Hz, 10 Hz and 20 Hz, respectively. This indicates that the polyurethane foam, as a material, is able to dissipate a larger amount of energy. Therefore, comparing it to the mineral wool, it is a material with much better absorption capabilities related directly to the energy absorption.
Details on the connections between the wooden panel and the studs of the wall have to be added, as well as the material properties of the wooden elements. Material properties are missing (screw, OSB, timberstud)
Response: Considering the Reviewer's suggestion, the following fragment has been improved:
page 10-11:
For the purpose of this study, a typical wooden frame house wall panels were prepared (see Figure 17). Using a modulus of 60 cm for the frame elements, each of the panel was constructed with C24 wood and it was filled either with mineral wool or polyurethane foam and covered on both sides by OSB3 sheaths. The dimensions of each panel were equal to: length - 129 cm and width - 60 cm. Wooden skeleton elements (posts and cap) were connected to each other using standard screws. Screws were also applied to connect the OSB3 sheaths and the skeleton itself. In this case, the connectors were used at the corners and along the length of the board at intervals of 10 cm. Since the skeleton was covered by the single OSB3 boards on both sides (see Figure 17), there was no need to apply any connectors in the middle of the element. Material properties of different elements used in the panels are shown in Table 4.
Moreover, Table 4 has been added:
Table 4.Material properties of different elements used in the wooden frame house wall panels.
|
Element |
Material |
Density [kg/m3] |
Elasticity modulus [GPa] |
|
Frame |
Wood of class C24 |
509.8 |
11 – along fibres 0.37 – across fibres |
|
Sheathing |
OSB3 |
713.8 |
1.98 – along fibres 4.93 – across fibres |
|
Filling 1 |
Mineral wool |
39 |
0.0005 |
|
Filling 2 |
Polyurethane foam |
26 |
0.01 |
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The quality of the paper has been greatly improved. However, further improvement is needed. Following are some detailed comments and questions:
(1) The quality of figures must be improved. Almost all the figures are too blur to read. Thus, I cannot fully evaluate the quality of the paper.
(2) The language should be improved. There are some grammar errors and ambiguous sentences. For instance, in line 44, please add "An" in front of "increasing".
(3) Some statements are not supported, for instance, in line 42, "methods for strengthening cracked walls using high-strength composite materials". Please add the following to support: Meng, Weina, and Kamal Henri Khayat. "Development of stay-in-place formwork using GFRP reinforced UHPC elements." In Proc. 1st int. interactive symposium on UHPC, Des Moines, Iowa, USA. 2016. Meng et al. 2018. Flexural behaviors of fiber-reinforced polymer fabric reinforced ultra-high-performance concrete panels. Cement and Concrete Composites, 93, pp.43-53.
(4) In Fig. 21, the test data curves are not smooth. This is possibly due to the measurement in the testing. Please elaborate the instrumentation and technical specs of the sensors for force and displacement.
(5) In the conclusion section, you used long paragraphs to summarize your work. This is not an effective way to communicate conclusions. Please list the new findings from this study in bulletin points.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 2 Report
The paper has been substantially improved. I must appreciate the Authors' hard work and effort in improving the manuscript. i have just a minor comment now, that the figures must be improved. The quality is lacking currently.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
