Mechanical characterization of visually graded boards from turkish fir and black pine by nondestructive and destructive tests


  • Fatih Kurul Istanbul University - Cerrahpaşa. Faculty of Forestry. Department of Wood Mechanics and Technology. İstanbul, Turkey.
  • Ömer Asım Şişman Gebze Technical University. Civil Engineering Faculty. Kocaeli, Turkey.
  • Türker Dündar Istanbul University - Cerrahpaşa. Faculty of Forestry. Department of Wood Mechanics and Technology. İstanbul, Turkey.



Board, flatwise bending, finite element method, mechanical properties, stress wave, visual grading


For the mechanical characterization of Turkish fir and black pine, 400 board specimens with 22 mm×   50 mm × 420 mm were visually graded according to TS 1265 standard. Nondestructive tests were here upon performed using the stress wave method. After specimens were intentionally tested under flatwise bending  to research the applicability as an alternative to tension and edgewise bending tests in European strength grading system. According to analyses of variance, the mean values of MOR and MOE differed in four groups at a p<0,05 significance level for visually graded boards. High correlations were found between MOR-MOE (R2=0,837) for fir and MOR-MOE (R2=0,776) for black pine. In addition, correlations of MOR-Knot rate for fir and black pine were respectively R2=0,669 and R2=0,660 showing the effectiveness of flatwise bending tests with the visual grading standard. For nondestructive tests, the mean values of the dynamic modulus of elastici- ty were very close in between fir and black pine grades while the usage of defect-free density performed better than the density of the whole specimen. Higher strength classes were found for black pine boards (Class 1= C40, Class 2= C27 and Class 3= C22) compared to fir boards (Class 1= C24, Class 2= C22 and Class 3= C18), respectively. Moreover, a simplified nonlinear material model was proposed for numerical modelling, and the results were found in good agreement in terms of the bending stiffness, strength, and deformation capacity of boards especially for class 1 and class 2 in both softwood species.


Download data is not yet available.


ASTM. 2018. Standard practice for establishing allowable properties for structural glued laminated timber (Glulam). D3737. American Society for Testing and Methods, West Conshohosken.

Arriaga, F.; Osuna-Sequera, C.; Bobadilla, I.; Esteban, M. 2022. Prediction of the mechanical proper- ties of timber members in existing structures using the dynamic modulus of elasticity and visual grading param- eters. Construction and Building Materials 322: e126512.

Barriola, M.; Aira, J.; Villanueva, J. 2021. Analytical models of the mechanical properties of Japanese larch (Larix kaempferi (Lamb.) Carr.) based on non-destructive testing and visual grading parameters. Wood Material Science & Engineering 16(2): 94-101.

Barriola, M.J.; Aira, J.R.; Lafuente, E. 2020.Visual grading criteria for Japanese larch (Larix kaemp- feri) structural timber from Spain. Journal of Forestry Research 31(6): 2605-2614. s11676-019-01025-5

Berg, S.; Turesson, J.; Ekevad, M.; Huber, J.A.2019. Finite element analysis of bending stiffness for cross-laminated timber with varying board width. Wood Material Science & Engineering 14(6): 392-403.

BS. 2017. Visual strength grading of softwood. Specification. BS. 4978. 2007+A2. 2017. London.

Bucur, V. 2006. Acoustics of Wood. Springer Science & Business Media.

Burawska-Kupniewska, I.; Krzosek, S.; Mańkowski, P.; Grześkiewicz, M. 2020. Quality and Bending Properties of Scots Pine (Pinus sylvestris L.) Sawn Timber. Forests 11(11): e1200. f11111200

CSI. 2000. SAP 2000. Integrated finite element analysis and design of structures. Ver. 21. Berkeley, CA.

Crovella, P.; Smith, W.; Bartczak, J. 2019. Experimental verification of shear analogy approach to pre- dict bending stiffness for softwood and hardwood cross-laminated timber panels. Construction and Building Materials 229: e116895.

DIN. 2012. Strength grading of wood – Part 1: Coniferous sawn timber DIN 4074-1. Berlin.

Divós, F.; Kiss, F.S. 2010. Strength Grading of Structural Lumber by Portable Lumber Grading - effect of knots. The Future of Quality Control for Wood & Wood Products. 4-7th May 2010. Edinburgh, The Final Conference of COST Action (Volume 53).

Esteban, L.G.; Fernández, F.G.; de Palacios, P. 2009. MOE prediction in Abies pinsapo Boiss. timber: Application of an artificial neural network using non-destructive testing. Computers & Structures 87(21-22): 1360-1365.

ECS. 2002. Moisture content of a piece of sawn timber - Part 1: Determination by oven dry method. EN 13183-1:2002. CEN: Brussels, Belgium.

ECS. 2012a. Timber structures - Structural timber and glued laminated timber - Determination of some physical and mechanical properties. EN 408:2010+A1:2012. CEN Brussels, Belgium.

ECS. 2012b. Structural timber - Strenght classes - Assignment of visual grades and species. EN 1912:2012. CEN: Brussels, Belgium.

ECS. 2013. Timber structures - Glued laminated timber and glued solid timber - Requirements. EN 14080:2013. CEN: Brussels, Belgium.

ECS. 2015. Timber structures - Cross laminated timber – Requirements. EN 16351:2015. CEN: Brussels, Belgium.

ECS. 2016a. Timber structures - Calculation and verification of characteristic values. EN 14358:2016. CEN: Brussels, Belgium.

ECS. 2016b. Structural Timber - Strength classes. EN 338:2016. CEN: Brussels, Belgium.

ECS. 2018a. Structural timber - Determination of characteristic values of mechanical properties and density. EN 384:2016+A1:2018. CEN: Brussels, Belgium. CEN:110:0::::FSP_PROJECT,FSP_ORG_ID:68122,6106&cs=112A171326697217D743EBDC1D81E1A0D

ECS. 2018b. Round and sawn timber - method and measurement. Part 3: Features and biological degrada- tions. EN 1309-3:2018. CEN: Brussels, Belgium.

ECS. 2019. Round and Sawn Timber. Terminology. EN 884.2019. CEN: Brussels, Belgium.

Frese, M.; Enders-Comberg, M.; Blaß, H.J.; Glos, P. 2012. Compressive strength of spruce glulam. European Journal of Wood and Wood Products 70(6): 801-809.

Görgün, H.V.; Dündar, T. 2018. Strength grading of turkish black pine structural timber by visual eval- uation and nondestructive testing. Maderas. Ciencia y Tecnología 20(1): 57-66.

Guntekin, E.; Bulbul, Z. 2014. Determination of bending properties for Black pine (Pinus nigra A.) lumber using stress wave method. Düzce Üniversitesi Orman Fakültesi Ormancılık Dergisi 10(2): 11-17. http://

Guntekin, E.; Emiroglu, Z.G.; Yilmaz, T. 2013. Prediction of bending properties for turkish red Pine (Pinus brutia Ten.) lumber using stress wave method. BioResources 8(1): 231-237. https://bioresources. sing-stress-wave-method/

Kandler, G.; Lukacevic, M.; Füssl, J. 2018. Experimental study on glued laminated timber beams with well-known knot morphology. European Journal of Wood and Wood Products 76(5): 1435-1452.

Kohler, J.; Brandner, R.; Thiel, A.B.; Schickhofer, G. 2013. Probabilistic characterisation of the length effect for parallel to the grain tensile strength of Central European spruce. Engineering Structures 56: 691-697.

Köhler, J.; Sørensen, J.D.; Faber, M.H. 2007. Probabilistic modeling of timber structures. Structural Safety 29(4): 255-267.

Mitsuhashi, K.; Poussa, M.; Puttonen, J. 2008. Method for predicting tension capacity of sawn timber considering slope of grain around knots. Journal of Wood Science 54(3): 189-195. s10086-007-0941-5

Mvolo, C.S.; Stewart, J.D.; Koubaa, A. 2021. Comparison between static modulus of elasticity, non-de- structive testing moduli of elasticity and stress-wave speed in white spruce and lodgepole pine wood. Wood Material Science & Engineering 17(5): 345-355.

Navaratnam, S.; Christopher, P.B.; Ngo, T.; Le, T.V. 2020. Bending and shear performance of Australian Radiata pine cross-laminated timber. Construction and Building Materials 232: e117215.

Nwokoye, D. 1972. Investigation into an ultimate beam theory for rectangular timber beams-solid and laminated. Timber Res Develop Ass Res Rep E/rr 34

OGM. 2021. T.C. Tarım ve Orman Bakanlığı Orman Genel Müdürlüğü.

Olsson, A.; Oscarsson, J.; Serrano, E.; Källsner, B.; Johansson, M.; Enquist, B. 2013. Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation. European Journal of Wood and Wood Products 71(3): 319-333. 013-0684-5

Pang, S.J.; Shim, K.B.; Kim, K.H. 2021. Effects of knot area ratio on the bending properties of cross-lam- inated timber made from Korean pine. Wood Science and Technology 55: 489-503. s00226-020-01255-5

Ross, R.J. 2015. Nondestructive evaluation of wood. General Technical Report. USDA Forest Service, Forest Products Laboratory. General Technical Report, FPL-GTR-238. 176 p.

Rais, A.; Bacher, M.; Khaloian-Sarnaghi, A.; Zeilhofer, M.; Kovryga, A.; Fontanini, F.; Hilmers, T.; Westermayr, M.; Jacobs, M.; Pretzsch H.; van de Kuilen, J. W. 2021. Local 3D fibre orientation for tensile strength prediction of European beech timber. Construction and Building Materials 279: e122527.

Sanabria, S.J.; Furrer, R.; Neuenschwander, J.; Niemz, P.; Sennhauser, U. 2011. Air-coupled ultra- sound inspection of glued laminated timber. Holzforschung 65(3): 377-387.

Stapel, P.; van de Kuilen, J.W. 2014. Influence of cross-section and knot assessment on the strength of visually graded Norway spruce. European Journal of Wood and Wood Products 72(2): 213-227.

TS. 2012. Sawn timber (Coniferous) - For building construction. TSE 1265. Ankara, Turkey.

UNI. 2010. Structural timber - Visual strength grading for structural timbers - Part 1: Terminology and measurements of features. UNI 11035-1. Milano, Italy.

UNE. 2011.Visual grading for structural sawn timber. Coniferous timber. UNE. 56544. Madrid, Spain.

Van Duong, D.; Matsumura, J. 2018. Within-stem variations in mechanical properties of Melia azeda- rach planted in northern Vietnam. Journal of Wood Science 64(4): 329-337. 018-1725-9

Van Duong, D.; Ridley-Ellis, D. 2021. Estimating mechanical properties of clear wood from ten‐year‐old Melia azedarach trees using the stress wave method. European Journal of Wood and Wood Products 79(4): 941-949.

Vega, A.; González, L.; Fernández, I.; González, P. 2019. Grading and mechanical characterization of small-diameter round chestnut (Castanea sativa Mill.) timber from thinning operations. Wood Material Science & Engineering 14(2): 81-87.




How to Cite

Kurul, F. ., Şişman, Ömer A. ., & Dündar, T. . (2023). Mechanical characterization of visually graded boards from turkish fir and black pine by nondestructive and destructive tests. Maderas-Cienc Tecnol, 26, 1–18.