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•A custom-built device was used to measure fluorescence from Scots pine heartwood.•Heartwood fluorescence intensity and stilbene content had a quantitative association.•Fluorescence ...measurements could be performed on green and dried heartwood.•Stilbene content is a promising variable for predicting heartwood decay resistance.•The method has potential to be utilized in timber grading and tree breeding programs.
Decay resistance is an important property of heartwood timber. The decay resistance of Scots pine heartwood correlates with its stilbene content, but the determination of both requires laborious and destructive analyses. To aid in the determination of these important properties, we investigated the feasibility of an optical method based on the intensity of UV-excited fluorescence for the non-destructive measurement of heartwood stilbene content and decay resistance. Fluorescence measurements carried out on samples from 58 trees showed a high correlation (r = 0.79, p < 0.000) between fluorescence intensity and stilbene content. The intensities measured from green and dried samples were highly correlated. The correlation between the fluorescence intensity and mass loss due to the brown rot fungus Coniophora puteana (r = -0.64, p < 0.000) was lower than the correlation between the stilbene content and mass loss (r = -0.78, p < 0.000). Nonetheless, the method showed promise in separating the low and high mass loss samples from the average heartwood material. The fluorescence-based method may be utilized in timber grading and tree breeding, and due to the strong correlation between green and dry measurements, it may be applied at any stage of the processing chain.
This study investigated possibilities to predict the presence of internal checks in thermally modified Norway spruce timber after 2.5 years of weathering based on the initial properties of the ...boards. Machine-learning classification enabled sorting the input parameters based on their relative importance for accurate predictions. The parameters of thermally modified timber with the highest relative importance were annual ring width followed by initial moisture content, density and dynamic stiffness. Whereas after kiln drying these were, density, annual ring width, initial moisture content and acoustic velocity. The results showed that predictions are possible, and an accuracy of 67% was achieved by using annual ring width combined with density and initial moisture content, or acoustic velocity that can be determined after either kiln drying or thermal treatment.
•Surface checking and mechanical properties of weathered Thermally modified timber (TMT) were predicted.•Board’s dynamic stiffness is the most crucial predictor variable.•Initial moisture content is ...an important predictor of TMT’s bending strength.•Models failed to accurately predict the degree of surface checking in weathered TMT.•Decision tree and ANFIS outperform regression models when predicting TMT’s bending properties.
Machine learning (ML)-based models, decision tree and ANFIS, were used to predict the degree of surface checking and bending properties of 30-month weathered thermally modified timber. The results showed that the investigated initial board properties did not allow accurate predictions of surface checks. ML regression and clustering analysis confirmed important variables for accurate predictions of bending properties were dynamic stiffness, acoustic velocity, density and lowest local bending modulus. ML models performed better than conventional regression models used for timber grading, and a prediction accuracy of 80–90% for bending stiffness and 50–70% for bending strength could be achieved.
•Currently, Populus spp. timber is not included in Spanish visual grading standard.•Qualifying efficiency of UNE-56544:1997 applied in this timber is not appropriate.•ME-1 visual grade does not ...comply to the minimum values established in EN-338.•Supervised Machine Learning algorithms use improves this qualifying process.•Visual defects, sawing systems and non-destructive variables were better predictors than UNE-56544.
The efficiency of visual grading standards applied to structural timber is often inappropriate, and timber properties are either under or over-graded. Although not included in the current UNE 56544 visual grading standard, machine learning algorithms represent a promising alternative to grade structural timber. The general aim of this research was to compare the performance of machine learning algorithms based on visual defects, non-destructive techniques and sawing systems (“cut type”) with UNE 56544:1997 visual grading in order to predict the qualifying efficiency of Populus x euramericana I-214 structural timber. Visual evaluation, ultrasound and vibrational non-destructive testing, and sawing systems register (radial, tangential and mixed) were applied to characterize 945 beams. In addition, in order to retrieve actual physical-mechanical values, density and static bending destructive testing (EN-408:2011 + A1:2012) was also carried out. Several machine learning algorithms were then used to grade the beams, and their predictive accuracy was compared with that of visual grading. To do so, three scenarios were considered: a first scenario in which only visual variables were used; a second scenario in which “cut type” variables were also included; and a third scenario in which additional non-destructive variables were considered. Results showed a poor level of performance of UNE 56544:1997, with an apparent mismatch between the strength values assigned for each visual grade (established by the EN 338 standard) and the actual values. On the opposite, all algorithms performed better than visual grading and may thus be deemed as promising timber strength grading tools.
Key message
The potential of European National Forest Inventories to harmonise stem quality estimation in European forests was identified despite considerable differences in existing national ...approaches.
Context
Knowledge on stem quality and assortments structure in European forests is highly important for policy makers and the timber industry and also for carbon life cycle analysis due to the fact that different timber products have different end use and thus store carbon for different time periods.
Aims
The study aim was to evaluate the potential of European National Forest Inventories (NFI) to objectively report on the stem quality in European forests in a harmonised manner.
Methods
A comprehensive questionnaire was conducted as the first important step to evaluate the current status of stem quality assessment and assess the existing level of harmonisation.
Results
Direct stem quality assessment or classification is used in 19 out of 28 European NFIs. Only eight countries provide timber assortment estimates from their NFIs. In addition, different sampling strategies for stem quality assessment are used among NFIs. Tree parameters relevant for stem quality assessment on standing trees were identified for the purpose of harmonisation. Several methods towards harmonisation between European NFIs for the purpose of reporting on stem quality of European forests were suggested.
Conclusion
Current European NFIs are not capable of reporting the stem quality of European forests in a harmonised manner at this stage and considerable efforts will need to be taken before the harmonised stem quality estimation can be prepared. However, the inquiry also revealed that there is a potential to develop the harmonised estimations in future.
Strength grading is essential for the efficient use of structural timber. Although international standards exist for machine strength grading, visual grading is still regulated based on national ...rules, which are expected to allow safe and economic grading results. Although there are large differences in the graded output because the species, the cross section, and the origin of the timber influence the results, some of these standards are considered to be applicable universally. The present article demonstrates how the chosen standards influence the grading results. Depending on the parameters, the yields or the mechanical properties are low compared with the declared values. The results also show the efficiency and applicability of different national standards for strength grading of timber from various origins. Furthermore, it is recommended to reconsider the existing limits for source areas and cross sections given in the standard EN 1912.
This book contains papers presented at the 1st International Conference on Timber Structures, which was held in collaboration with the Technical Centre of Wood Industry in Belgium. It explores the ...latest developments in wood products and their application as structural components. The focus of the included works is to draw attention to new research and real applications from both researchers and practitioners, and to present new and innovative ideas in this significant field.Rapid advances have recently been made in the development and processing of innovative ecologically friendly wood products. A variation of new structural shapes can now be fabricated and used to construct buildings and bridges that have minimal impact on the environment. Wood is particularly appealing since it is renewable and has no carbon footprint when it is harvested in a sustainable way. Timber structures are ecologically sound and comparatively low cost. The material lends itself to ground-breaking designs and new types of composites offer reliable, robust and safe materials.The content of this book comprises a range of topics: Material properties of wood; Durability aspects, service life modelling; Fire safety of timber structures; Protection against decay; Non-destructive inspection and monitoring; Glued, laminated structures, Xlam and CLT; Timber joints and connections; Vernacular wood and heritage timber structures; Timber housing and eco-architecture; Timber bridges; Large span timber roof structures; Shell structures in timber; Mixed, composite and hybrid structures; Computational analysis and experimental methods; Structural engineering and design; Seismic behaviour of timber structures; Protection of timber; Repaired timber structures; Rapidly assembled and transferable timber structures; Guidelines, codes and regulations; Structural failures; Art and craftsmanship.
Wood stabilization and functionalization is a hot topic towards increasing the use of wood in buildings. Building construction and materials account for around 11% of the global CO2 emissions, thus ...there is increasing interest in using wood to replace concrete, steel, and aluminium. However, the perceived quality of wood in service decreases quickly in comparison with non-biodegradable alternatives, so aging must be delayed as much as possible through stabilization and functionalization. The question addressed in this paper is how to measure the perceived quality of wood products in service. The concept of wood quality is difficult to define, as it depends on a combination of factors such as customer satisfaction, wood fibre characteristics, products, applications, and so on. This paper proposes a definition of timber quality based on market price. By knowing the market value of a potential range of wood products, the proposed method calculates the loss of value due to developing defects caused by aging. Overall, the proposed methodology allows converting the subjective concept of aging into an objective $ value. A numeric example is presented based on the New Zealand timber grading rules. The results showed that 5.1 m by 150 mm by 50 mm softwood timber can lose up to 61% of its value as appearance grade if a single aging defect develops beyond the maximum allowed size.
The paper presents the results of experimental tests and the process by which a batch of spruce timber elements is sorted in a strength class with reliability.
Grading tests were performed on 338 poplar wood samples (
I-214) with dimensions of 150×50 mm
, 150×80 mm
, and 200×100 mm
prepared for structural utilization. The non-destructive testing methods ...included ultrasound (Sylvatest) and induced vibrations (Portable Lumber Grader) combined with visual grading criteria. Additionally, screw withdrawal resistance was tested by the instrument Fakopp. These results were compared with those obtained by a four-point bending test according to the EN 408 (2004) standard. Ultrasound and induced vibrations overestimated the quality of this type of wood. Correlation equations are proposed to determine the true characteristics for each testing method. It can be concluded that poplar timber from clone I-214 has acceptable flexural strength, but a comparatively low elastic modulus, whereby it is not graded within a high strength class according to the EN 338 (2009) standard.
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