Articles

WOOD RESEARCH Volume 61, Number 5, 2016
Josef Cafourek, Milan Gaff, Miroslav Gašparík, Martin Slávik, and Jan Macků

Properties and use of biomass from reclaimed land in the North Bohemian Basin

Spoil heaps are negative urban landscape features resulting from intense human activities to acquire mineral resources. One very positive method for reclaiming spoil heaps is afforestation. This paper analyzes the quality of Black locust wood acquired from the reclaimed area of Varvažov, North Bohemian Basin, Czech Republic. The following characteristics were used as indicators of the quality of wood obtained from the given area: chip dimensions; ash content; bulk density; bark content; contents of C, H, N, and O; and contents of S, P, Ca, Mg, K, Fe, Zn, and Mn. Black locust biomass is suitable for energy purpose, although it contains an increased proportion of inorganic elements. The other properties, such content of C, H, N, and O, ash content as well as heating value, are in compliance with the standardized values. The Black locust chips can be categorized as Coarse-grained energetic wood chips with minimal dust particle content according to particle-size distribution analysis.

WOOD RESEARCH Volume 61, Number 5, 2016
Regita Bendikiene and Gintaras Keturakis

The effect of tool wear and planning parameters on birch wood surface roughness

In this study, the surface quality of birch wood (Betula) test pieces planned with experimental planning tools (ET1, ET2) and influence of tool wear of quality of surface were examined. These tools were made by surfacing using a submerged arc welding (SAW) technique and a mixture of alloying elements (cromium, tungsten, fero-manganese, silicon carbide) spread on the surface under industrial flux. Surface roughness was measured along and across wood fibre. According to the results of experiments it is obviously that average roughness parameters along fibre is lower than across. Planning tool wear results revealed that 3200 m of cutting length is not significant for tools ET1 and ET2 wear. The same can be said about tool nose width change: For ET1 from 2.8 to 2.9 μm, and for ET2 from 2 to 3.4 μm – effect of negligible changes of tool edge geometry on planned surface quality is low. Feed of planning tool played more significant role – twice higher feed per insert (ET1 – 1.00 mm, ET2 – 0.5 mm) showed lower surface quality after planning. To reach necessary wood surface quality, lower feed rate and suggested experimental planning tool ET2 with higher wear resistance than commercial tool is preferable for planning of birch wood.

WOOD RESEARCH Volume 61, Number 5, 2016
Yuxia Chen, Shiliu Zhu, Yong Guo, Shengquan Liu, Daowu Tu, and Hui Fan

Investigation on withdrawal resistance of screws in reconstituted bamboo lumber

The objective of this study was to evaluate the effects of screw diameter, pilot hole diameter, screw type and loading rate on the withdrawal resistance of some screws in reconstituted bamboo lumber (RBL) and comparison of screw withdrawal resistance in RBL with MDF and Particleboard. Results indicate that there were no significant differences among withdrawal resistance with screw diameter, screw type and loading rate. Significant differences were found between withdrawal resistance with pilot hole diameter. Screw withdrawal resistance decreased with increasing pilot hole diameter. Suggested size of pilot hole is 60-85 % of the nominal screw diameter. The withdrawal resistances in the face and edge of RBL are greater than the end direction. This reveled RBL is anisotropic. Face and edge withdrawal resistances of screws in RBL were higher as compared with those of MDF and particleboard. This indicates that withdrawal resistance of RBL meets the requirements of furniture structure design.

WOOD RESEARCH Volume 61, Number 5, 2016
Bartosz Pałubicki and Tomasz Rogoziński

Efficiency of chips removal during CNC machining of particleboard

The results of testing of chips extraction system efficiency during CNC milling of particleboards were presented in this paper. Experimental machining was performed using the 3-axis CNC router Weeke Venture 108M and a standard diamond tipped, newly sharpened shank-type router bit. As a material the market size (2200×1250×18 mm) laminated particleboards with density of 649 kg.m-3 were used. The efficiency of chips extracion system of the CNC machine depends on the mode of milling. For pocketing nearly 100 % of chips were removed succesfullywhile for through-milling it was only 87 %. The extraction system worked with very high effieiency regarding chips smaller than 0.1 mm. The chips extraction efficiency decreases for larger and havier chips.

WOOD RESEARCH Volume 61, Number 5, 2016
Antonín Lokaj, Kristýna Klajmonová, David Mikolášek, and Kristýna Vavrušová

Behavior of round timber bolted joints under tension load

In the current European standards for the design of timber structures, the issue of timberto-timber joint type is addressed only to squared timber, which makes the pinpointing of the round timber bolted joints carrying capacity near-unfeasible due to the insufficient support in the current standards. There have been made series of tests of round timber joints in different inclinations tensile load to the grainand also the reference tests of squared timber joints to compare the behaviour of this type of joints. Mechanical behaviour of round and squared timber bolted joints were tested in the laboratory of the Faculty of Civil Engineering in Ostrava.This paper presents results of static tests in tension at an angle of 0, 90 and 60° to the grain of squared and round timber bolted joints. Carrying capacity was determined according to the applicable standards and theories of fracture mechanics. Round timber joints were also numerically simulated. The test results of numerical models were then compared with the results of laboratory tests and theoretical calculations.

WOOD RESEARCH Volume 61, Number 5, 2016
Sha Sha Song, Qian Wan, and Ge Ge Wang

Eye movement evaluation of different wood interior decoration space

In order to improve people’s living quality and ameliorate their living environment, making the full use of the environmental characteristics of wood materials in the building and interior decoration become more and more important. In this paper, the development and application of eye tracking technology is summarized, and the development trend of eye movement research in the field of wood environment is reviewed. Through an eye tracking experiment research on indoor wood decoration space to explore if different specialty, the sex, the wooden interior proportion factor have significant effect on people’s judgment on the picture preference or not. Make exploration of people for different wood interior decoration environment preference and visual cognitive style, providing new ideas and methods for room decoration design. On the other side, through the study of the eye movement to explore the wood interior decoration environment has an objective and effective and scientific significance.

WOOD RESEARCH Volume 61, Number 5, 2016
Adam Krajewski, Paweł Kozakiewicz, and Piotr Witomski

Shear strength of Scots pine (Pinus sylvestris L.) from the historical buildings

Comparative research was conducted on shear strength parallel to grain of heartwood of Scots pine (Pinus sylvestris L.) from the 16-18th century from Central Poland and of modern wood. Tests were performed on 150 samples of aged wood from 13 construction elements of 4 historic buildings and on 100 samples from 10 modern constructional elements. Aged wood revealed a better technical quality. The difference of average shear strength parallel to grain values equaled 0.09 MPa and the translation of correlation line was about 0.35 MPa in favour of aged wood.

WOOD RESEARCH Volume 61, Number 4, 2016
Vlastimil Borůvka, Aleš Zeidler, and Stanislav Doubek

Impact of silicon-based chemicals on selected physical and mechanical properties of wood

This study deals with the impact of silicon-based chemicals on selected physical and mechanical properties of wood. Wood of European beech and Scots pine was the testing material used for impregnation using water glass and commercial product Lukofob EVO 50. The impact of the treatment on dimensional stability, bending strength and modulus of elasticity was tested. Wood density was also evaluated. Although the modification using silicon-based staffs resulted in a statistically significant decrease in swelling for both of the tested species, the positive effect of the treatment was accompanied by a decrease in the strength and stiffness of wood. Water glass had a stronger effect on the tested properties from the chemicals we used in our research.

WOOD RESEARCH Volume 61, Number 4, 2016
Vilém Podrázský, Jiří Remeš, Roman Sloup, Karel Pulkrab, and Stanislav Novotný

Douglas-fir – partial substitution for declining conifer timber supply – Review of Czech data

The decrease is supposed of the coniferous assortments supply due to running changes of tree species composition in the Czech forests as well as due to the environmental changes in the next decades. The Norway spruce (Picea abies /L./ Karst.) is the most endangered species. The year timber supply decrease of this species is supposed in an extent of 0.9 mil.m3 in the next two decades (2013 – 2032) and more than 1 mil. m3 for all conifers. Cultivation of Douglas-fir (Pseudotsuga menziesii /Mirb./ Franco) can substitute N. spruce on specific sites and so eliminate partially the timber supply decline in the future. The cultivation of Douglas-fir could lead to increase of the plantation area from 5,800 ha (today) to the extent of 49,616 – 163,713 ha respecting legislative restrictions and recommendations of general management plans. This can represent increased timber increment of 300,000 – 650,000 m3 per year and substantially mitigate the coniferous timber supply fall in the next decades.

WOOD RESEARCH Volume 61, Number 4, 2016
Klára Kroftová and Markéta Šmidtová

The current state of knowledge in the field of the use of selected nanosystems in heritage preservation – nanotextiles as biocidal protection of historic wood

The awareness of the need to protect wooden members dates back to the Middle Ages when the most common material for the protection of wood was oxblood. At present, there is a huge variety of biocidal chemical agents for wood protection available (such as Lignofix, Bochemit). Nanotextiles represent a novel method of enhanced biocidal protection of historic wood which has been intensively verified at the Faculty of Civil Engineering, CTU in Prague within the NAKI DG16P02M055 research. The paper will present partial results of experimental research into the effects of selected nanotextiles on the surface of historic wood applied for the purpose of biocidal protection. The research included the verification of the efficiency of nanotextiles without dopants and with dopants of Ag and TiO2 nanoparticles. Surprisingly, a higher biocidal efficiency of nanotextiles without dopants was reached than in the case of nanotextiles with dopants.

WOOD RESEARCH Volume 61, Number 4, 2016
Eliška Oberhofnerová and Miloš Pánek

Surface wetting of selected wood species by water during initial stages of weathering

Currently, the trend of using untreated wood elements in the exterior is becoming more progressive. The rainwater nevertheless needs to be recognized as an important factor increasing photo-degradation of wood and causing other damages as splits, cracks and deformations. The aim of this work is to determine the influence of initial stages of weathering on wetting properties of wood surfaces evaluated by the contact angle measurements using goniometer Krüss DSA 30E. Nine wood species were tested during 12 months of weathering: spruce, larch, pine, Douglas fir, oak, black locust, maple, alder and poplar. The lower decrease of the contact angle of water drop was observed on maple, alder and black locust surfaces, which predicts higher durability and slower degradation during weathering. On the contrary, the higher decrease of contact angle and higher hydrophilicity of wood surfaces was observed on all softwoods and oak and poplar as well.

WOOD RESEARCH Volume 61, Number 4, 2016
Miloš Lavický, Jan Pěnčík, Jakub Dohnal, David Bečkovský, and Tereza Bečkovská

Static numeric and experimental analysis of prefabricated winder wooden staircase with central stringer made from Scots pine (Pinus sylvestris L.)

The article describes behaviour of the structure of a prefabricated winder wooden staircase with central stringer on the material basis of Scots pine (Pinus sylvestris L.). It focuses on static behaviour of this structure. An analysis was performed with the use of 3D numerical modelling with the finite element method using ANSYS calculation system. The numerical analysis with an orthotropic material model and Hoffman and Tsai-Wu interactive failure criteria showed critical points of this type of analysed staircase. Subsequently, selected critical points were experimentally tested for static loading on models of wooden fragments of the staircase in the scale of 1:1. Experimental tests and numerical analyses pointed out the importanceof a suitable choice of a material model of wood and the necessity to pay particular attention to designing of these points. The results and conclusions could be helpful for designing of a prefabricated winder wooden staircase with the central stringer.

WOOD RESEARCH Volume 61, Number 4, 2016
Vladimír Duchoň, TOMÁŠ KLAS, Orsolya Katona, JÁN BRODNIANSKY, Ľuboš Balcierák, Jaroslav Sandanus, and Kristian Sógel

Experimental tests of timber connections with glued-in rods in bending

The article deals with research of joints with glued-in threaded rods. The introduction provides a brief presentation of the issue. The first part focuses on axially loaded glued-in threaded rods. The second part explains the behaviour of joints with glued-in rods loaded by bending moment. Theoretical analysis was performed on models based on the finite element method. Verification of theoretical results was realized by practical experiments. Tensile tests were carried out on timber blocks with glued-in bars to verify the depth of affixing. Furthermore, the resistance in bending was confirmed on actual beams with glued-in bars in the middle of the span. Results and the follow-up work are summarized in the conclusion.

WOOD RESEARCH Volume 61, Number 4, 2016
Kristýna Vavrušová, Antonín Lokaj, David Mikolášek, Roman Fojtík, and Libor Žídek

Longitudinal glued joints of timber beams and the inf luence of quality manufacturing onto their carrying capacity

The content of this article is to analyse destructive testing results of longitudinal solid wood joints of structural size beams with internal and external glued wood-based panels (plywood) stressed in bending, which was mostly focused on simulating the effect of the glued line thickness (1 and 3 mm) and the influence of contact surfaces of longitudinally connected elements when bending loads. The aim of this article is to compare the carrying capacity and the joint real behaviour under load with values obtained using numerical modelling and calculation according to valid standards.

WOOD RESEARCH Volume 61, Number 4, 2016
Petr Čech, Daniela Tesařová, Jana Hadačová, and Eva Jeřábková

The quality of indoor air in wooden based buildings and the factors with impact of them

The primary aim of the paper is to characterize the emissions of volatile organic compounds (VOC) in the indoor air of wood-based buildings in the Krkonoše Mts. region in relation to season, age of the building, air moisture content and engineering composition of building materials. It aims to identify the impact of important factors on the amount and content of VOC emitted into indoor air. The experimental part focuses on the assessment of influence of applied wood-based materials in the wood-based buildings on the quantity and quality of VOC emissions in indoor air. The second aim is to determine the impact of age of a building and the time of VOC measuring on the amount and content of emitted VOC, particularly on the amount of emitted terpenes and aldehydes. VOC emissions were analysed by gas chromatograph Agilent GC 6890 N with a mass spectrometer with cryofocusation, thermal desorption and library of spectra NIS 05.

WOOD RESEARCH Volume 61, Number 4, 2016
Jaromír Srba, Martin Böhm, Jitka Beránková, Kamil Trgala, Regina Orálková, and Guillermo Velarde

Estimation of air leakage rate of wood-based residential buildings constructed in the Czech republic in the years 2006-2014 using blower door test

The article analyses the air leakage rate in 203 newly constructed low-energy and passive wood-based residential buildings in the Czech Republic. The most frequent air leakage points were analysed in the buildings measured, and the development of the air leakage rate in the period monitored (2006-2014) was evaluated. A significant decrease in air leakage rate values was found out in low-energy buildings, while the results for passive buildings were more or less steady within the period in question. Further, airtightness of envelopes of low-energy buildings not equipped with a mechanical ventilation system with heat recovery reached, in some cases, values indicating that recommended values of the overall air leakage required by hygienic regulations are not ensured.

WOOD RESEARCH Volume 61, Number 4, 2016
Martin Sviták, Karel Krontorád, and Jan Tomek

Defining of thermal bridges of wood building and their elimination

The thesis focuses on the matter of thermal bridges in case of wooden panel structures, both in case of low-energy and passive structure-standard. Thermography was used for localization of critical areas of structures – details of corner joints of external walls and ceiling connections. The values subject to comparison are the linear coefficient of heat penetration from the exterior and the lowest interior surface temperature. This results in the overall comparison of both the structures as well as elimination of the excessive heat flow, whereas the difference in detail of corner joints of external walls is 0.03 W.(m.K)-1 for both, and the difference in detail of the ceiling connections equals 0.07 and 0.08 W.(m.K)-1 respectively. The difference in the lowest interior surface temperature in detail of corner joints of external walls for both structures equals 1.34 and 2.99°C respectively, and in the detail of the ceiling connections the difference is 2.45°C.

WOOD RESEARCH Volume 61, Number 4, 2016
Pavla Kotásková, Zdeňka Havířová, Milan Šmak, and Bohumil Straka

Log buildings from the perspective of the current requirements

This contribution focuses on the verification of temperature and moisture content conditions inside perimeter walls of timber buildings as regards the temperature and humidity requirements in buildings intended for permanent residence. We assessed: a simple perimeter wall of solid timber, a wall of glued BSH profiles, a wall of an existing log building with additional thermal insulation in two options, and a sandwich log wall with a layer of embedded insulation. This study contrasts theoretical calculations with the values measured in a real buildings. The effect of the humidity changes on the strength and stability of dowelled joints is analysed.

WOOD RESEARCH Volume 61, Number 4, 2016
David Bečkovský, Lucie Vacková, Tereza Bečkovská, Jindřich Sobotka, Jan Pěnčík, and Miloš Lavický

Analysis of the diffusional properties of peripheral walls of wooden houses during EMW radiation exposure

The article discusses the changes in diffusion properties of wood and wood-based materials. These changes are caused by excessive moisture content within the materials and the consequent possible attack by wood-destroying pests. Wood-destroying pests in this case are represented by microscopic filamentous fungi (i.e. mould), which slightly changes and deteriorates both, the characteristics of wood and wood-based materials, and the environment humans live in. This paper discusses the theory and application of microwave radiation and the experimental optimization of radiation to sterilize these biotic factors. Furthermore, the article describes the experiments conducted at the Faculty of Civil Engineering, demonstrating the results of sterilization process with regards microscopic fungi that occur in building materials. By analysing the results of the research, the optimum intensity of microwave emitters and necessary lengths of irradiation times were determined.

WOOD RESEARCH Volume 61, Number 4, 2016
Kamil Staněk, Jan Tywoniak, Jan Richter, Michal Bureš, Pavel Kopecký, and Martin Volf

Studies on hygrothermal performance of wood elements in building constructions–remarks on methodology

In general, building constructions containing wood elements are moisture sensitive. To increase the knowledge about their hygrothermal performance accompanied with assessments of risk of mold growth and other degradation mechanisms a set of analytical methods is typically used: standard calculation or more advanced mathematical models, laboratory measurements and field observations. Nevertheless, in some cases such approach seems not to be sufficient. Full size testing under controlled and long-time stable boundary conditions is needed in order to get more complex picture about the real performance and risks. In the first part, the paper informs about hygrothermal problems and mold growth modelling. The key part of the paper deals with methodology and technique available at University Centre for Energy Efficient Buildings: Full size façade openings for placing different assemblies of building envelopes with wood elements and facility with crawl-space type foundations. Furthermore, laboratory experiments and measurements together with in-situ monitoring as example are presented. The paper discusses combinations of advanced modelling used for design of experiments on one hand with expected results from full size controlled testing on the other hand. Classification of mold growth risk can represent an efficient way of expression of overall quality in this respect. First results are presented here for illustration. Paper concludes that coordinated combination of different research techniques can bring new knowledge in understanding the processes leading to deterioration of wood elements in building construction.