Classification of timber for various commercial purposes is essential for its proper application in order to ensure the reliability and economic use. Visual grading of structural timber is commonly ...used in a number of EU countries, with different grading national standards optimized for locally available wood. Countries in the ex-YU region are traditional partners in wood trade and had the same standards for visual grading, but in most of the regions these standards are not completely compliant with EN requirements. Consequently, that leads to the fact that the most of regionally available structural timber is not assigned into strength classes, which is the starting point for the limit-state concept in design of timber structures. The aim of this paper is to emphasize the lack of strength classification of structural timber in the ex-YU region, which is a prerequisite for the design of timber structures made by civil engineers. Based on an overview of visual classification types with regional experience in grading, relevant EN standards, and differences in design concepts with possible consequences of grading approach, it can be concluded that "quality" grades and "strength" classes are not easily comparable.
Klasifikacija drvne građe za različite komercijalne namjene ključna je za njezinu pravilnu upotrebu kako bi se zajamčila sigurna i ekonomična uporaba. Vizualno ocjenjivanje konstrukcijskog drva obično se provodi u mnogim zemljama EU-a uz pomoć različitih nacionalnih standarda ocjenjivanja optimiziranih za lokalno dostupno drvo. Zemlje bivše Jugoslavije tradicionalni su partneri u međusobnoj trgovini drvom i imale su zajedničke standarde za vizualno ocjenjivanje drvne građe, ali u većini njih ti standardi nisu u potpunosti usklađeni s EN zahtjevima. To posljedično rezultira činjenicom da većina regionalno dostupnoga konstrukcijskog drva nije razvrstana u klase čvrstoće, što je polazište za koncept graničnog stanja u projektiranju drvnih konstrukcija. Cilj rada jest upozoriti na nepostojanje klasifikacije čvrstoće konstrukcijskog drva na području bivše Jugoslavije, a to je preduvjet za projektiranje drvnih konstrukcija, što je posao građevinskih inženjera. Na temelju tipova vizualne klasifikacije i regionalnih iskustava u ocjenjivanju, relevantnih EN normi te razlika u konceptima projektiranja s mogućim posljedicama pristupa ocjenjivanju, zaključeno je da ocjene razreda kvalitete i klase čvrstoće u promatranim zemljama jednostavno nisu međusobno usporedive.
The paper demonstrates improved structural low-frequency vibroacoustic performance of cross-laminated timber (CLT) floor panels by informed selection of the wood material. The use of wood species and ...strength classes that are not traditionally assigned to CLT panels was investigated in order to study their influence on dynamic characteristics and vibroacoustic response metrics. The potential of each of the orthotropic material properties to alternate the vibration response was examined to determine the governing parameters of the low-frequency vibroacoustic performance. The effects on transfer mobility response functions, and eigenfrequencies and mode shapes were used for a rigorous performance study of the panels. It was found that using laminations with stiffness properties typical for hardwoods ash, beech, and birch can significantly improve the performance of a CLT floor panel, and they outperform laminations of typical softwood strength classes.
Background and Objectives: The aim of this study was to determine the effects of different stand densities on wood density (WD), global modulus of elasticity (MOE), and bending strength (MOR) in ...35-year-old Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst) stands, representing the hemiboreal forest zone. Materials and Methods: Scots pine and Norway spruce sites, representing different stand densities of 3000–3100; 2000–2100 and 1000–1100 trees per hectare, were chosen. Visually healthy model pine and spruce trees were selected, and diameter at breast height (DBH) was measured for model trees; the competition index was calculated; the MOE and MOR were evaluated by the Standards EN 408:2006 and EN 384:2016, at 12% moisture content; WD and the knot diameter were measured; and the strength class of wood was determined by the Standard EN 338:2009. To predict wood quality characteristics based on stand and tree characteristics, linear regression models were developed. Results and Conclusions: Higher stand density led to a significant change in the main wood properties of both conifer species. The highest mean WD, MOE, and MOR were obtained at the sites with the highest stand density. The MOE and MOR were highly correlated, but relatively weak correlations were found between MOE and MOR with tree DBH and WD. Despite the lower quality of Scots pine wood, the Norway spruce wood from more dense sites corresponded to the strength class of C16, according the strength grading of softwoods. The linear regression models did not perform well in describing the relationship of wood properties with stand and tree characteristics. The models for MOR accounted for the highest variation of 62–65% for both Scots pine and Norway spruce. These relationships can be expected to change with increased stand age or with the inclusion of specific crown parameters.
Artificial intelligence and its diverse applications are examples of emerging new technologies that have so far been shown to be successful in merging scientific applications. Generally, intelligent ...systems outperform their traditional counterparts in solving non-linear tasks. Artificial neural network (ANN) models are usually designed and used to arbitrate these non-linear problems; as they mimic the structure and function of a biological brain. In this paper, an intelligent classification system is proposed to decide the result of a routine and laborious civil engineering quality control process. The ANN model is specifically designed, implemented and tested in order to classify the compressive strength grade of different concrete mixes as low, normal or high strength. Concrete elements of varying compressive strength classes and qualities, are required to be used for different purposes and under different environmental conditions. The grade of the concrete’s strength is highly dependent on many non-linear factors and it is often conventionally determined by using civil engineering methods involving the destruction of concrete samples. Our aim is to classify the concrete strength without destructing any samples. Experimental results in this work show high efficiency in correctly classifying the compressive strength.
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.
RESUMO Como consequência dos fatores edafoclimáticos, as propriedades da madeira podem ser influenciadas de acordo com a região de desenvolvimento da árvore. O objetivo do presente trabalho consistiu ...em verificar a influência da região de extração de lotes da madeira de Tatajuba (Bagassa guianensis), provenientes de duas diferentes regiões do Brasil (Alta Floresta e Bonfim do Sul, municípios dos estados de Mato Grosso e Roraima, respectivamente), ao teor de umidade de 12%, em algumas de suas propriedades físicas e mecânicas. Para cada um dos lotes foram determinadas duas propriedades físicas e cinco propriedades mecânicas, de acordo com a norma ABNT NBR 7190:1997. Para avaliar a influência da região de extração nas propriedades, foi realizada a análise de variância de Kruskal-Wallis, considerando resultados significativos (valores não equivalentes) aqueles que atendiam à condição P-valor < 0,05. De acordo com os resultados da análise estatística, os diferentes lotes da mesma espécie de madeira apresentaram valores médios das propriedades estudadas equivalentes em relação ao conjunto composto por todas as madeiras, porém, os valores médios da resistência na compressão paralela (fc0) e da densidade aparente não foram significativos entre as duas regiões. Os valores característicos da fc0 foram diferentes para os lotes das duas regiões, ao teor de umidade de 12%, implicando em classes de resistência diferentes (D50 – Alta Floresta e D60 – Bonfim do Sul).
En las últimas décadas en Europa se ha promovido la promulgación de Códigos de Práctica, Directivas y Normas Armonizadas de obligado cumplimiento para los países miembros, que afectan a la madera en ...la construcción y que son imprescindibles para favorecer al material en su uso estructural. Debido al carácter dinámico intrínseco a las normas, y necesario para su funcionalidad, éstas sufren modificaciones en el tiempo por lo que es necesario confrontarlas con el material realmente existente. En este trabajo se realizó un muestreo representativo en el País Vasco sobre una de las especies de madera más habituales en la construcción en España como es el pino radiata (Pinus radiata D.Don), buscando la veracidad de lo disponible en el mercado tanto en calidades como en dimensiones, y se aplicó la metodología normalizada y estipulada para su caracterización. Además, en cada una de las piezas se aplicaron los criterios de clasificación visual establecidos en la norma española UNE 56.544 para la estimación de calidades. En los resultados se presentan las conclusiones obtenidas tras la aplicación de las últimas variaciones de la normativa para la determinación de las propiedades mecánicas, las cuales están implicadas en los análisis de la caracterización estructural de la madera y condicionan la asignación resistente final. Abstract In the last decades in Europe the promulgation of Practice Codes, Directives and Harmonised Standards of obliged fulfilment for the member countries was promoted. They affect to wood in construction and are essential to improve the material in the structural use. Due to the dynamic character proper of standards, and necessary for their functionality, these suffer modifications in the time that are necessary to check in the really existing material. In this work, a representative sampling on one of the usual species of wood in the construction in Spain, as it is the radiata pine, was carried out, looking for the veracity of the available material in the market both in qualities and sections. The standard methodology stipulated for the characterization was applied. Additionally, in each piece, the visual classification criteria established in the Spanish standard UNE 56.544 for the estimation of the strength grades, was applied. The results set forth the conclusions obtained after the application of the last changes of the regulation for the determination of mechanical properties, which are involved in the analyses of the structural characterization of timber and determine the final strength assignation.
Canary Island pine (Pinus canariensis C.Sm. ex DC) is a species endemic to the Canary Islands (Spain) that was for centuries overexploited for its wood and resin. Due to the state of the pine forest, ...more than 10,000 hectares were reforested in the middle of the 20th century. Now, under the silvicultural management plan, thinning operations have allowed Canary Island pine wood to be mechanically characterised for the first time using large test pieces. In total, 1529 pieces measuring 2600 × 120 × 35 mm and visually graded according to Spanish standard UNE 56544 (Visual grading of large structural coniferous sawn timber) were assessed, resulting in 872 pieces in grades ME-1 and ME-2 and 657 rejects. After the characteristic values of density (479–453 kg∙m−3), modulus of elasticity (MOE) (14,023–11,276 N∙mm−2) and bending strength (MOR) (26–14 N∙mm−2) were determined for both grades (ME-1 and ME-2), strength class C24 was assigned to grade ME-1, with similar values to Pinus radiata D.Don and Pinus pinaster Aiton, and C14 was assigned to grade ME-2. Density, number of growth rings, growth ring width, and presence/absence of resinous wood have a significant influence on MOE and MOR, for a confidence level of 95%. Reforestation of Canary Island pine not only allows restoration of the forest cover, but also provides an opportunity, through thinning, to obtain quality wood, helping to create employment and associated industry. This local example with an endemic species can be extrapolated to other parts of the world.
Despite the variability and particularities that the timber reveals, the strength class grading system has been developed to meet the need to correlate structural design standards with quality ...standards for timber products. The paper presents the standardised approaches for determining the characteristic values of properties for timber products, with the purpose of classifying the material according to the strength classes system presented in European standards.
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