Effect of knots on the flatwise bending stiffness of lumber members

Samson, M. V.; Blanchet, Louis-Émile

doi:10.1007/bf02663256

Cited by 8 publications

(3 citation statements)

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“…Knots had an average KAR of 0.51 (0.5 median) and were significantly different to the clear samples for bending MOE (p < 0.001) and strength (p < 0.001) with averages of 22.5% (23.1% median) and 41.6% (39.4% median) less, respectively (Figure 9 and Table 2). This is similar to reductions for KAR of 0.5 on-flat bending seen in Samson and Blanchet [50] but less than that seen for on-edge bending [51,52] which is reasonable given others have found knots to have less impact in on-flat bending [50,53]. Figure 10 shows that there is a decreasing trend for MOE and strength with increasing KAR but KAR alone was not a strong indicator with low R 2 values.…”

Section: Effect Of Knotssupporting

confidence: 75%

“…Figure 10 shows that there is a decreasing trend for MOE and strength with increasing KAR but KAR alone was not a strong indicator with low R 2 values. The rate of change in MOE and strength with increasing KAR is low at around 45% and 20% less, respectively, than others in the literature [50][51][52]. This can be expected given these other studies looked at higherlongitudinal-stiffness timber which has a greater difference between longitudinal and transverse properties.…”

Section: Effect Of Knotsmentioning

confidence: 64%

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Mechanical Properties of Low-Stiffness Out-of-Grade Hybrid Pine—Effects of Knots, Resin and Pith

Cherry

Karunasena

Manalo

2022

Forests

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Out-of-grade pine timber is an abundant material resource that is underutilised because its mechanical properties are not well understood. Increasing trends toward shorter rotation times and fast-grown plantation pines around the world such as Pinus elliottii x P. caribaea var. hondurensis hybrid (PEExPCH) mean low-stiffness corewood is becoming a larger portion of this out-of-grade population. This study characterised the modulus and strength properties in bending, compression parallel to grain (CParG) and compression perpendicular to grain (CPerpG), shear and tension strength of low-stiffness out-of-grade PEExPCH. The effect of resin, knots and pith on these properties were also investigated. The results show that in clear wood, the MOE in bending, CParG, CPerpG and shear modulus are 6.9 GPa, 5.78 GPa, 0.27 GPa and 0.59 GPa, respectively, while strengths are 45.8 MPa, 29.4 MPa, 6.7 MPa, 5.7 MPa, respectively. The tensile strength is 32.4 MPa. Resin significantly increased density 45% higher than clear, but performed similar with the exception of CPerpG MOE and strength which were significantly different. Resin area ratio (RAR) has a moderate correlation with density with an R2 of 0.659 but low to no correlation for mechanical properties. Knots were significantly different to clear for all test types and within a range of 48% to 196%. Knots were high in CPerpG MOE and strength but lower for all other properties and had the largest negative impact on tensile strength. Knot area ratio (KAR) had low to moderate correlation with tension strength and CPerpG MOE with R2 of 0.48 and 0.35, respectively. Pith was within the range of 76% to 121% of non-pith samples for structural performance, some of which were significantly different, and pith samples were higher in density than non-pith. This new information is crucial for the effective establishment of grading rules, design optimisation and utilisation of low-stiffness out-of-grade PEExPCH as a new material resource in civil engineering applications.

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Section: Effect Of Knotssupporting

confidence: 75%

Section: Effect Of Knotsmentioning

confidence: 64%

Mechanical Properties of Low-Stiffness Out-of-Grade Hybrid Pine—Effects of Knots, Resin and Pith

Cherry

Karunasena

Manalo

2022

Forests

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“…the knot cluster with the highest tKAR-value) is assumed as the load-bearing capacity of the entire timber board. The interrelation between the stiffness properties and knot indicators are analysed in Samson and Blanchet (1992) and . In all studies described above, no knot-indicator could be found for an efficient prediction of the strength and stiffness properties of structural timber without considering additional indicators, such as the density.…”

Section: Introductionmentioning

confidence: 99%

Model for the prediction of the tensile strength and tensile stiffness of knot clusters within structural timber

Fink

Köhler²

2014

Eur. J. Wood Prod.

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In the present paper, a model for the prediction of the local strength and stiffness properties is developed. Compared to existing models, here the local material properties are described according to their morphological characteristics; i.e. the timber boards are subdivided into sections containing knots (knot sections) and sections without knots (clear wood sections). The strains of the corresponding sections are measured during non-destructive tensile tests using an optical camera device. Based on these measurements the tensile stiffness of each particular section is estimated. For the estimation of the tensile strength, destructive tensile tests are performed. Herewith, the tensile strength of the entire timber board is measured. The strength of the other knot clusters are estimated using censored regression analysis. Taking into account the results of the experimental investigation, material models are developed to predict the tensile strength and the tensile stiffness of knot clusters.

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Study of the relationship between flatwise and edgewise modull of elasticity of sawn timber as a means to improve mechanical strength grading technology

Steffen

Johansson

Wormuth³

1997

Holz als Roh-und Werkstoff

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Effect of knots on the flatwise bending stiffness of lumber members

Cited by 8 publications

References 1 publication

Mechanical Properties of Low-Stiffness Out-of-Grade Hybrid Pine—Effects of Knots, Resin and Pith

Mechanical Properties of Low-Stiffness Out-of-Grade Hybrid Pine—Effects of Knots, Resin and Pith

Model for the prediction of the tensile strength and tensile stiffness of knot clusters within structural timber

Study of the relationship between flatwise and edgewise modull of elasticity of sawn timber as a means to improve mechanical strength grading technology

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