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ISSN 2542-1468, Лесной вестник /Forestry Bulletin, 2017. Т. 21. № 4. С. 89-94. © МГТУ им. Н.Э. Баумана, 2017
Using poplar elements in light frame... Новые материалы и технологии...
УДК 678.01 DOI: 10.18698/2542-1468-2017-4-89-94
USING POPLAR STUD ELEMENTS IN LIGHT FRAME WALL STRUCTURE INSTEAD OF CONIFEROUS
Zoltan Pastori1, Imre Czupy2, G.A. Gorbacheva3
1 Innovation Center at the University of Sopron, 4. Bajcsy Zs. Sopron, Hungary 9400
2 Institute of Forest and Environmental Techniques at the University of Sopron, 4. Bajcsy Zs. Sopron, Hungary 9400
3 BMSTU (Mytishchi branch), 1 st. Institutskaya, 141005, Mytischi, Moscow reg., Russia
The overall objective of the investigation is to change coniferous wood element to poplar in the wall construction of light frame wood residential buildings therefore important properties were compared. Although not all coniferous element of wood wall is worth to be changed, but there are elements such as studs what are not bearing big forces and have lower exposure. It was investigated some of the most important influencing factors determining the utilization of poplar elements in light frame wall constructions. The element chosen to be changed in the wall construction was examined in the following aspects: mechanical properties; thermo-dynamical properties; screw holding strength. Nowadays one of the most important questions is the thermal resistance of the structure. Originally the studs are heat bridges among the thermal insulation materials being between studs. The poplar studs have a lower thermal conductivity than that of the coniferous consequently the thermal bridge effect is lower compared to the coniferous. The other main part of the study is to investigate the properties of the whole construction. According to our investigations the poplar seems to be an appropriate row material of light frame constructions with the condition the bulk density is higher than 400 kg/m3.
Keywords: Light frame wood structure, poplar PopulusEuramericana, thermal conductivity, screw holding strength
Suggested citation: Pastori Z., Czupy I., Gorbacheva G.A. Using poplar stud elements in light frame wall structure instead of coniferous // Lesnoy vestnik / Forestry Bulletin, 2017, vol. 21, no. 4, pp. 89-94. DOI: 10.18698/2542-1468-2017-4-89-94
Introduction
In the northern hemisphere the most widespread raw material used in light frame wood construction is coniferous mostly scots pine and spruce. There are wood species which is used mostly for industrial purposes like poplars and the secondary utilization for higher value added products is desirable. Many countries have great population of different hardwood species e.g. the fast growing poplar. In descending order Canada, the Russian Federation, the United States, China and Germany have the biggest reported natural poplar stands out of the International Poplar Commission (IPC) member countries. China, India, France, Turkey and Italy have the biggest reported planted poplar areas, also in ascending order of IPC members [3, 15]. Some of these countries have high quality poplar plantations that can produce materials with dimensions appropriate for building frame elements.
The possibility of using poplar in exterior structures was already examined [4]. According other researchers' opinions the most promising utilization of poplar among others is structural panel industries [1, 2, 9]. Fraanje [7] examined the possibilities of using poplar wood as purlin.
There have already been numerous experiments to use Hungarian broad leaved wood species raw materials but these attempts have been suppressed by the existing coniferous-based construction techniques.
In the 1970's the Forestry Research Institute in Hungary (FPI) already looked into the possible applications of broad leaved wood materials in glue laminated frame structures [6, 14]. The two applicable species mentioned in their work are poplar and black locust. From a strength point of view, black locust is the most desirable; however, hybrid poplars are more favorable in terms of figure and dimensional properties. The raw material of the first building of this sort, using layered-cemented three-point arc framed was hybrid poplar. In addition, even presently, there are family houses at the Hungarian Great Plane with poplar-based roof structure, what reason is the availability of poplar raw material at the region.
Apart from these, numerous European and North American examples exist for using different wood species than coniferous. There have been a number of experimental attempts on using broad leaved wooden materials for structural purposes. Hernandez et al. [8] reported the construction of a vehicular bridge with a glue laminated structure of tulip tree. Another example is presented by the collaboration of the Swiss architecture company, Bernath and Widmer with other experts (Hermann Blumer, Michael Koller, Bergauer Holzbau GmbH, Heiri Buhrer), who constructed a three-story youth hostel of oak logs in Schaffhausen province near Buttenhardt. In summation, experts are constantly examining the possible usage of stratum raw materials, which could open new horizons in wood construction, beyond the conventional coniferous-based methods.
To create safe poplar structures, thorough examination of basic stress factors, like tensile compressive and bending strength followed by the different analysis of the full-sized specimen including the thermo-technical attributes. In the case of full structures where the overall performance depends on the interaction of the adjacent materials and their features, these thermo-technical and strength tests and durability comprise the basis of the examination.
This article focuses on introducing only on some of the important examined attributes, such as strength and thermodynamic differences between poplar and spruce. The authors are aware that deeper analysis of more features is necessary for the applicability but the article does not touch upon these due to space limitations.
MATERIAL AND METHODS
In Hungary, poplar cover 1,5 million ha, accounting for the 9,6 %-a of the full forest area. Every year 1,3...1,5 million m3 poplar raw materials are processed which comprises 23...25 % of all wood cutting. To ensure good quality, poplar plantations have to be branch cut up to 6 meter height what can be called pruning [11].
The coniferous wood species ratio is very low in Hungarian forest contrast to the Siberian forests, and also to the west — and north European forests. Because of this fact high amount of the construction wood is imported in building market. However, Hungary has valuable broadleaved wood species such as poplar (Populus Euramericana cv. Pannonia).
From the 1980's more and more hybrid poplar species have been genetically improved, cutting back the share of then-popular I 214 Italian poplar. Examining the plantation data of the poplar species in the 90's, the Populus Euramericana proves to have had the biggest share (almost 50 %) on the market [13].
Fundamental differences can be observed among certain poplar clones in density, strength, and figure and also in durability. In the table 1 below the attributes of the most common poplar clones and the control variables are highlighted.
Among the mechanical properties density and strength have crucial importance. Bending strength plays a crucial role among strength features. Populus Euramericana (Pannonia) was selected due to its excellence in these two defining parameters along with its figural properties, durability and quantity. Its Hungarian ratio is remarkably high; it is the most important poplar species of the plantation-type poplar growing [13].
Due to the lower mechanical properties of poplar the dimensions of the cross section could expectedly be changed as the distance of studs from each other.
Mechanically the wall should not be significantly weaker than the original construction build with coniferous studs and top and bottom elements.
MECHANICAL PROPERTIES
The utilization of the different wood species depends on their physical and mechanical properties. In general, the strength of poplar wood falls below that of coniferous, but for certain species the differences is not substantial. Examinations by the Witmann and Pluzsik [14] provided strong correlation between the mechanical properties of poplar and their volume mass. According to their findings, the poplar species whose absolute dry volume mass reaches or exceeds 400 kg/m3 can effectively replace coniferous in strength-stressed structures and in structural units. Taking into account the literature and our test results, these apply to the Populus Eu-ramericana. The comparison investigation results also reveal that the density of wood highly depends on the soil of planting location and the volume of precipitation.
We conducted our tests on 50 Populus Euram-ericana specimens prepared in accordance with the standards based on the following strength groups:
- tensile strength
- compressive strength
- shear strength
- bending strength
- impact strength
SCREW HOLDING STRENGTH
There is only few literature with exact information about the nail and screw holding strength of the Populus Euramericana but there is indication that their nail holding strength is 5...10 % lower than that of pines [5]. Due to the number of species, the screw holding strength of the hybrid poplar should be measured experimentally, in parallel with pine test units. The last valid standard (MSZ EN 1382) gives an exact description of the examination that can be conducted with arbitrary nail and screw properties so that specific values can be assigned to the joints the most likely to be used.
Thermal conductivity
Our research also examined the conventional thermal conductivity of Populus Euramericana compared that of the spruce, the most widely used wood species in light frame wood construction. Minimizing the thermal bridges is essential when designing the wall structure. There is a huge difference between the thermal conductivity of the wall frame and the insulation materials.
The frame in the wall structure are located every 62,5 cm. This wall structure relates back to the 125 cm table division. The usual 40...50 (45) mm thick studs create a substantial thermal bridge in the wall. 16,5 % of the full wall surface comprises wood compared to insulation material [12]. The bigger the
Table 1
Mechanical properties of polar species (Toth, 2006; Molnar, 1999) [10, 13]
Механические свойства полярных видов (Toth, 2006; Molnar, 1999) [10, 13]
Name Density [kg/m3] Mechanical properties Elastic modulus [MPa] Hardness
[MPa] [MPa, Brinell]
shear compressive bending tensile butt side
I-214 330 6,4 22,5 52 44,3 5330 21,9 8,3
Villafranca 350 6,9 32 64 46,2 5600 19,3 9,9
Triplo 360 - 26,6 57 64,1 - 22,8 7,7
BL-Costanzo 375 7,5 36,9 75,1 59,6 6160 25,4 11,3
Koltay 390 - - 56 - - - -
Kopecky 390 7,4 33 70,7 56,1 5620 20,6 12,5
Parvifol 400 - 32,9 66,3 75 7830 24,8 9.8
Agathe-F 405 6,9 29,6 58 44,5 5200 20,7 11,7
I-273 410 8,1 32,8 72,2 - 5690 28 13,9
Pannonia 410 8,3 32,6 67,4 56,2 6510 20,6 10,8
Robusta 419 8,1 30,2 66,9 74,4 7500 22,8 7,7
Unal 420 - - - - - - -
White poplar 450 7,8 38,3 67,5 82,3 8250 27 -
Black poplar 450 6 35 65 77 8800 30,5 -
Trembling poplar 450 6.8 32,5 56 75 7800 23 -
Spruce 470 6,7 50 78 90 11000 32 -
Scotch pine 520 10 56 80 104 12000 40 19
difference in thermal conductivity the bigger the thermal bridge effect in the structure. The thermal conductivity of the insulation material is 0,04 W/mK compared to 0,12 W/mK of the spruce studs according to the literature. In accordance, on one sixth of the surface the coniferous material determines the thermal conductivity while the rest of the surface is dominated by the properties of the insulation material in terms of thermal behavior.
If the spruce material is replaced by poplar, the thermal bridge effect changes by the difference between the spruce and poplar thermal conductivity.
In the frame of another project, we also aimed for constructing a test building that makes identifying every step of the necessary technological processes possible. Manufacturing the building blocks requires industrial usage of the new material, and assembling and joining the structures also differs from the spruce technology. Testing and measuring the real stress results become possible on the full-size structure, especially regarding the thermal behavior of the building. Determining the value of low energy need is also possible.
RESULTS
MECHANICAL PROPERTIES
The test results have a strong correlation with density. In numerous cases, the density of Populus Euramericana reaches or even exceeds 400 kg/m3. Using this material for studs in structural applications is also possible, thus it can replace spruce in certain structural units. Our test results are summarized in
table 2. In structural materials bending strength is the most important property. According to our tests, the Populus Euramericana should be further examined as raw material for light frame wall construction as its key strength properties approach those of the spruce. It is important to examine which spruce parts can be replaced in the wall structure system, as well as how the dimension of these parts would change.
The strength test results of Populus Euramericana show favorable values; in addition it is available in high quantities. It is reasonably priced and it is a raw material relatively easy to work with. Due to its low natural resistance, the Populus Euramericana needs proper protection as well.
Screw holding strength
Our screw holding strength analysis was conducted in accordance with the latest corresponding standards. Table 3 shows the test results of the Populus
Table 2
Comparison of mechanical properties
Сравнение механических свойств
Name Poplar Spruce
ah — u12 % (N/mm2) ah — u12 % (N/mm2)
Tensile strength 52,49 90
Compressive strength 38,51 50
Shear strength 5,24 6,7
Bending strength 57,04 78
Impact strength 3,65 4,6
Table 3
Result of screw holding strength tests of Populus Euramericana
Прочность на сжатие винта Populus Euramericana
Name Butt [N/mm] Serial 1 [N/mm] Serial 2 [N/mm] Serial 3 [N/mm] Serial 4 [N/mm]
Minimum 20,00 47,50 47,50 40,00 50,00
Maximum 62,50 92,50 90,00 95,00 102,50
Average 45,70 63,80 63,60 65,40 66,26
Scatter 8,84 12,31 11,92 11,52 9,86
Variance 78,07 151,59 142,13 132,74 97,25
Euramericana test pieces — measurements included 1 from butt direction, 2-2 screw tests from radial and tangential direction.
THERMAL CONDUCTIVITY
During the tests we prepared 20 test specimens per wood species whose corresponding thermal conductivity are shown in table 4. The specimens had been air conditioned in a climate chamber on normal climate (20 °C and 65 % relative humidity). To be able to compare them, the specimens were stored and measured the same way with the same methods.
The data clearly indicates that the thermal conductivity values of the poplar are more favorable. Comparing our test results with the literature we arrive to an even more desirable conclusion: according
Table 4
Thermal conductivity of poplar and spruce specimens
Теплопроводность образцов тополя и ели
Specimen id. Thermal conductivity [W/mK] Density [g/cm3] Specimen id. Thermal conductivity [W/mK] Density [g/cm3]
Poplar 1 0,099 0,319 Spruce 1 0,087 0,397
Poplar 2 0,105 0,335 Spruce 2 0,091 0,409
Poplar 3 0,106 0,343 Spruce 3 0,090 0,417
Poplar 4 0,105 0,357 Spruce 4 0,092 0,401
Poplar 5 0,101 0,346 Spruce 5 0,095 0,428
Poplar 6 0,100 0,340 Spruce 6 0,092 0,405
Poplar 7 0,112 0,414 Spruce 7 0,091 0,406
Poplar 8 0,098 0,410 Spruce 8 0,110 0,491
Poplar 9 0,117 0,406 Spruce 9 0,128 0,515
Poplar 10 0,113 0,420 Spruce 10 0,126 0,516
Poplar 11 0,099 0,405 Spruce 11 n.a. 0,517
Poplar 12 0,108 0,406 Spruce 12 0,124 0,503
Poplar 13 0,106 0,407 Spruce 13 0,124 0,519
Poplar 14 0,105 0,409 Spruce 14 0,128 0,529
Poplar 15 n.a. 0,410 Spruce 15 0,125 0,532
Poplar 16 0,096 0,421 Spruce 16 0,122 0,519
Poplar 17 0,099 0,422 Spruce 17 0,117 0,514
Poplar 18 0,098 0,412 Spruce 18 0,119 0,511
Poplar 19 0,097 0,419 Spruce 19 0,117 0,505
Poplar 20 0,103 0,416 Spruce 20 0,114 0,497
Average 0,104 0,391 Average 0,110 0,477
to our measurements the difference between the two wood species in terms of thermal coefficient is nearly 6 %. During the design process when using spruce the usual values vary between 0,13...0,15 W/mK, in contrast our measurement showed only 0,110 W/mK.
The need for technological change compared to spruce techniques is going to be an important topic to examine during the research, as well as finding out whether the extra technology input is proportional to the benefits derived from using poplar instead of spruce.
CONCLUSION
MECHANICAL PROPERTIES
All of the mechanical properties of poplar showing weaker results than coniferous can be compensate
with higher dimensions or higher processing technologies. The poplar material used for construction materiel have to have higher density than 400 kg/m3.
SCREW HOLDING STRENGTH
According to the preliminary test results, the screw holding strength of the poplar raw material approximates that of the spruce. Special attention should be taken to the number, size and location of the joints in the important corner units. The point of view this aspect the Populus Euramericana could be substitute the spruce.
Thermal conductivity
Examination of the thermal coefficients revealed that the Populus Euramericana shows better properties leading to decreased thermal bridge effect in wall structures constructed of poplar rib frame. In the wall construction the poplar causes lower heat bridge effect thus the heat loss of the whole structure is lower. In case of a successful project the poplar could be the rival of the widely used coniferous row material of wood residential buildings/
ACKNOWLEDGEMENT
This study was supported by the EFOP-3.6.2-16-2017-00010 project sponsored by the EU and the European Social Foundation.
References
[1] Balatinecz J., Kretschmann D.E. Properties and utilization of poplar wood/ Donald I. Dickmann et al. Poplar Culture in North America. NRC Research Press, Ottawa, 2001, pp. 277-291.
[2] Balatinecz J., Kretschmann D.E., LeclercqA. Achievements in the utilization of poplar wood-guideposts for the future. The forestry chronicle, 2001, no. 77 (2), pp. 265-269.
[3] Ball J., Carle J., Lungo A.D. Contribution of poplars and willows to sustainable forestry and rural development. Un-asylva, 2005, 56 (2), pp. 3-9.
[4] Cassens D.L., Hunt M.O., Barnes H.M., Thompson W.S. Yellow-poplar lumber for exterior architectural applications in new construction and for historical restoration. Finishing and Restoring Wood and Structures, 2008, FNR-410-W, 6 p.
[5] Csizmadia P. A cser, akac es nyarfelek ipari feldolgo-zasanak jelenlegi helyzete es tovabbi lehetosegei. (Present situation and opportunities of industrial utilization of Turkish oak acacia and poplars) Faipari Kutatasok, Budapest, Faipari Kutato Intezet, 1969, v. 1, pp. 67-74.
[6] Erdelyi Gy., Wittmann Gy. A hazai termesztesu nemesnyarak ipari hasznosithatosaga. (Industrial usage of domestic hybrid poplars) Wood Researches Bulletin, Budapest, Wood Research Institute in Hungary, 1973, pp.109-124.
[7] Fraanje P.J. Poplar wood for purlins; an evaluation of options and environmental aspects. Holz als Roh- und Werkstoff, 1998, v. 56, pp. 163-169.
DOI: 10.1007/s001070050291
[8] Hernandez R., Ritter M.A., Moody R.C., Hilbrich Lee P.D. Yellow poplar glued-laminated timber: Product development and use in timber bridge construction. Conference book: National Conference on Wood Transportation Structures, Madison, Wisconsin, 1996, pp. 411-417.
[9] Kurt R. Suitability of three hybrid poplar clones for laminated veneer lumber manufacturing using melamine urea formaldehyde adhesive. Bioresources, 2010, no. 5(3), pp. 1868-1878.
[10] Molnar S. Faanyagismerettan. (Wood Science). Budapest, Mezogazdasagi Szaktudas Kiado, 1999.
[11] Molnar S., Banska M. Magyarorszag ipari fai. (Industrial woods of Hungary). Budapest, Szaktudas Kiado Haz Rt., 2002.
[12] Pasztory Z., Peralta P., Molnar S., Peszlen I. Modeling the Hygrothermal Performance of Selected North American and Comparable European Wood-Frame House Walls. Energy & Buildings, 2012, v. 49 (1), pp. 142-147.
[13] Toth, B. Nemesnyar-fajtak ismertetoje. (Description of hybrid poplars). Budapest, Agroinform Kiado es Nyomda Kft., 2006.
[14] Wittmann Gy., Pluzsik A. A faanyagu retegelt-ragasztott tartoszerkezetek hazai alkalmazasanak uj eredmenyei. (Novel application of glue laminated wood constructions) Wood Researches Bulletin, Budapest, Wood Research Institute in Hungary, 1975, pp. 61-70.
[15] Improving lives with poplars and willows — Synthesis of Country Progress Reports — Activities Related to Poplar and Willow Cultivation and Utilization. 2008 through 2011. Working Paper IPC 2008-2011, 2012.
Author's information
Pastori Zoltan — Ph. D, Director of Innovation Center, University of Sopron, Sopron, Hungary, [email protected]
Czupy Imre — Ph. D, Director of Institute of Forest and Environmental Techniques at the University of Sopron, Sopron, Hungary, [email protected]
Gorbacheva Galina Aleksandrovna — Cand. Sci. (Tech.), Associate Professor of Department of Wood Science and Technology, BMSTU (Mytishchi branch), [email protected]
Received 14.07.2017
ПРИМЕНЕНИЕ ДРЕВЕСИНЫ ТОПОЛЯ ДЛЯ ИЗГОТОВЛЕНИЯ СТОЕК В КАРКАСНЫХ КОНСТРУКЦИЯХ ВМЕСТО ДРЕВЕСИНЫ ХВОЙНЫХ ПОРОД
З. Пастори1, И. Цзупи2, Г.А. Горбачева3
1 Шопронский университет, Инновационный центр, Hungary, 9400 Sopron, Bajcsy-Zsilinszky utca 4.
2 Шопронский университет, Институт леса и природопользования, Hungary, 9400 Sopron, Bajcsy-Zsilinszky utca 4.
3 МГТУ им. Н.Э. Баумана (Мытищинский филиал), 141005, Московская область, г. Мытищи, ул. 1-я Институтская, д. 1
Цель работы заключалась в исследовании возможности замены элементов каркасных конструкций жилых домов из древесины хвойных пород на элементы из древесины тополя, а также в сравнении их основных свойств. Далеко не все элементы из древесины хвойных пород можно заменить, однако имеются стойки каркаса, которые скрыты внутри общей конструкции и не подвергаются большим нагрузкам. Проведены исследования некоторых наиболее важных факторов, определяющих использование тополя в легких каркасных конструкциях стеновых панелей. Элемент, выбранный для замены в конструкции стены, был рассмотрен в следующих аспектах: механические свойства, термодинамические свойства, прочность крепления шурупами. В настоящее время одие из важнейших вопросов — тепловое сопротивление конструкции. Стойки каркаса являются тепловыми мостами между теплоизоляционными материалами внутри каркаса. Стойки каркаса из древесины тополя имеют более низкую теплопроводность по сравнению с древесиной хвойных пород, следовательно, эффект теплового моста проявляется в меньшей мере. В результате исследования всей конструкции. установлено, что тополь является подходящим материалом для каркасных конструкций при плотности выше 400 кг/м3.
Ключевые слова: каркасные конструкции из древесины, тополь Populus Euramericana, теплопроводность, прочность крепления шурупами
Ссылка для цитирования: Пастори З., Цзупи И., Горбачева Г.А. Применение древесины тополя для изготовления стоек в каркасных конструкциях вместо древесины хвойных пород // Лесной вестник / Forestry Bulletin, 2017. Т. 21. № 4. С. 89-94. DOI: 10.18698/2542-1468-2017-4-89-94
Список литературы
[1] Balatinecz J., Kretschmann D.E. Properties and utilization of poplar wood/ Donald I. Dickmann et al. Poplar Culture in NorthAmerica. NRC Research Press, Ottawa, 2001, pp. 277-291.
[2] Balatinecz J., Kretschmann D.E., Leclercq A. Achievements in the utilization of poplar wood-guideposts for the future. The forestry chronicle, 2001, no. 77 (2), pp. 265-269.
[3] Ball J., Carle J., Lungo A.D. Contribution of poplars and willows to sustainable forestry and rural development. Unasylva, 2005, 56 (2), pp. 3-9.
[4] Cassens D.L., Hunt M.O., Barnes H.M., Thompson W.S. Yellow-poplar lumber for exterior architectural applications in new construction and for historical restoration. Finishing and Restoring Wood and Structures, 2008, FNR-410-W, 6 p.
[5] Csizmadia P. A cser, akác és nyárfélék ipari feldolgozásának jelenlegi helyzete és további lehetoségei. (Present situation and opportunities of industrial utilization of Turkish oak acacia and poplars) Faipari Kutatások, Budapest, Faipari Kutató Intézet, 1969, 1, pp. 67-74.
[6] Erdélyi Gy., Wittmann Gy. A hazai termesztésü nemesnyárak ipari hasznosíthatósága. (Industrial usage of domestic hybrid poplars) Wood Researches Bulletin, Budapest, Wood Research Institute in Hungary, 1973, pp.109-124.
[7] Fraanje P.J. Poplar wood for purlins; an evaluation of options and environmental aspects. Holz als Roh- und Werkstoff, 1998, v. 56, pp. 163-169. DOI: 10.1007/s001070050291
[8] Hernandez R., Ritter M.A., Moody R.C., Hilbrich Lee P.D. Yellow poplar glued-laminated timber: Product development and use in timber bridge construction. Conference book: National Conference on Wood Transportation Structures, Madison, Wisconsin, 1996, pp. 411-417.
[9] Kurt R. Suitability of three hybrid poplar clones for laminated veneer lumber manufacturing using melamine urea formaldehyde adhesive. Bioresources, 2010, no. 5 (3), pp. 1868-1878.
[10] Molnár S. Faanyagismerettan. (Wood Science). Budapest, Mezogazdasági Szaktudás Kiadó, 1999.
[11] Molnár S., Bariska M. Magyarország ipari fái. (Industrial woods of Hungary). Budapest, Szaktudás Kiadó Ház Rt., 2002.
[12] Pásztory Z., Peralta P., Molnar S., Peszlen I. Modeling the Hygrothermal Performance of Selected North American and Comparable European Wood-Frame House Walls. Energy & Buildings, 2012, v. 49 (1), pp. 142-147.
[13] Tóth, B. Nemesnyár-fajták ismertetoje. (Description of hybrid poplars). Budapest, Agroinform Kiadó és Nyomda Kft., 2006.
[14] Wittmann Gy., Pluzsik A. A faanyagú rétegelt-ragasztott tartószerkezetek hazai alkalmazásának új eredményei. (Novel application of glue laminated wood constructions) Wood Researches Bulletin, Budapest, Wood Research Institute in Hungary, 1975, pp. 61-70.
[15] Improving lives with poplars and willows — Synthesis of Country Progress Reports — Activities Related to Poplar and Willow Cultivation and Utilization. 2008 through 2011. Working Paper IPC 2008-2011, 2012.
Сведения об авторах
Пастори Золтан — директор Инновационного центра, Шопронский университет, [email protected]
Цзупи Имре — директор Института леса и природопользования, Шопронский университет, г. Шопрон, Венгрия, [email protected]
Горбачева Галина Александровна — канд. техн. наук, доцент кафедры древесиноведения и технологии деревообработки, МГТУ им. Н.Э. Баумана (Мытищинский филиал), [email protected]
Статья поступила в редакцию 14.07.2017 г.
