Bending strength adjustments for moisture content for structural lumber

Barrett, J. D.; Lau, W.

doi:10.1007/bf00225236

Cited by 8 publications

(6 citation statements)

References 4 publications

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“…Several publications provide mechanical properties of pine, agathis, meranti, and mahogany wood at air-dry conditions similar to this study's results (Table 5). Similar to many reports [18,[72][73][74], this study also finds that the mechanical properties of wet wood are consistently weaker than those of dry ones (Table 6). A similar phenomenon is valid for modulus of rupture (σ b ), shear strength parallel-to-grain (τ), tensile strength parallelto-grain (σ t ), maximum crushing strength (σ c ), compression stress perpendicular-to-grain at the proportional limit (σ c⊥pl ), compression stress perpendicular-to-grain at the 0.04" deformation (σ c⊥0.04 ), and modulus of elasticity (E) (Figure 4).…”

Section: The Mechanical Properties Difference Between Wet and Dry Woodsupporting

confidence: 90%

Comparing the Building Code Sawn Lumber’s Wet Service Factors (CM) with Four Commercial Wood Species Laboratory Tests

Bahtiar

Denih

Priadi

et al. 2022

Forests

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Indonesian Wooden Building Code (SNI 7973-2013) has adopted the National Design Specification (NDS) for Wood Construction since 2013. A periodic harmonization of the building-code-designated values (i.e., reference design values and adjustment factors) with the experimental data of commercial wood species is necessary. This study aimed to compare the building code’s wet service factors (CM) with the laboratory test of some commercial wood species. Since wood is weaker when its moisture content is high, the wet service factor (CM) must adjust the sawn lumber reference design values if the building serves in wet or aquatic environments. Four commercial wood species, namely pine (Pinus merkusii), agathis (Agathis dammara), red meranti (Shorea leprosula), and mahogany (Swietenia mahagoni), were subjected to mechanical property tests. To calculate the empirical CM values, the mechanical properties tests were conducted on air-dry and wet wood. Instead of testing the full-sized timber, which contains the growth characteristics and defects, this study chose clear-wood specimens to resemble the boundary condition of the ceteris paribus (other things being equal). The wet (water-saturated) specimens were immersed in water for 65 days, and the test was carried out when the specimen was still immersed. The test arrangement imitated the submerged wood as the worst-case scenario of the wet environment where the construction serves, rather than green or partially immersed timber. As many as 40 specimens were tested to compare each mechanical property’s wet service factor; thus, this study reported 200 specimens’ laboratory test results. The empirical CM values to adjust the modulus of elasticity, modulus of rupture, shear strength parallel-to-grain, tensile strength parallel-to-grain, and maximum crushing strength (CM = 0.59, 0.76, 0.65, 0.73, and 0.67, respectively) were significantly lower than SNI 7973-2013 designated values (CM = 0.9, 0.85, 0.97, 1, and 0.8, respectively). The empirical CM for the compression stress perpendicular-to-grain at the proportional limit and that at the 0.04″ deformation (CM = 0.66) were slightly lower than the designated values (CM = 0.67), although they were not significantly different. This study resulted in lower empirical CM values than the designated ones, which found that the building code lacked conservativeness. The lacked conservativeness is mainly attributed to the building code’s recent choices, e.g., (1) the wet service environment basis is the green timber rather than the fully water-saturated one, and (2) the ratio of near minimum (5% lower) distribution value is chosen as the CM value rather than the average of wet timber’s mechanical property divided by the air-dry one. This study proposes changing both recent choices to alternative ones to develop more safe and reliable designated CM values.

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Section: The Mechanical Properties Difference Between Wet and Dry Woodsupporting

confidence: 90%

Comparing the Building Code Sawn Lumber’s Wet Service Factors (CM) with Four Commercial Wood Species Laboratory Tests

Bahtiar

Denih

Priadi

et al. 2022

Forests

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“…It is well known that the moisture content of structural wood materials will directly affect its test strength value, and will also affect the subsequent determination of compressive design value [21]. Therefore, to unify the test strength value and compressive design value, each country often specifies a moisture content point as the reference point.…”

Section: Static Testing Methodsmentioning

confidence: 99%

A determination method of compressive design value of dimensional lumber

Zhong

Ren

et al. 2018

J Wood Sci

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The objective of this study was to develop a determination method of compressive design value of dimensional lumber for its safety design and rational application as a green building material. A total of 1049 full-size 2 × 4 samples of Chinese larch (Larix gmelinii) dimensional lumber, including visual grades Ic, IIc, IIIc, and IVc, were tested by static compressive tests. Compression strength parallel to grain (UCS) of different grades were summarized. By the least square method, the fitted parameters and results for UCS were obtained under different probability distribution models (normal, lognormal and 2-P-Weibull) and test data points (100, 75, 50, 25, and 15%). Based on reliability analysis method, relationships between the reliability index and partial factor were investigated under different probability distribution models, fitting data points, load combinations and load ratios. Finally, this study suggested that the lognormal distribution, 25% data points, load combination of dead load plus residential live load, and load ratio of 1.0 be selected for the determination of compressive design value of Chinese larch dimensional lumber. For Chinese larch dimensional lumber, the compressive design values of grade Ic, IIc, IIIc and IVc were 22.9, 18.3, 14.6 and 13.8 MPa, respectively.

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“…High strains often indicate where damage will occur. 24 When the stress distribution in the xx direction was evaluated, the LVL samples showed similar stress distribution characteristics at half the load (F max /2). At the same time, it was observed that the stress in the support regions and the loading head area increased.…”

Section: Digital Image Correlation Resultsmentioning

confidence: 95%

“…The total reduction in edgewise loading was determined as 39%. Barrett and Lau, 24 in their study determining the moisture modeling of Douglas fir (Pseudotsuga menziesi) and southern pine (Pinus taeda L.) structural lumber, reported that increased moisture reduced bending strength (modulus of rupture -MOR). In Figure 7, the LVL modulus of elasticity values are given for 0-25% MC.…”

Section: Mechanical Test Resultsmentioning

confidence: 99%

The effects of the moisture content of laminated veneer lumber on bending strength and deformation determination via two-dimensional digital image correlation

Sözen

Kayahan

Bardak

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part C:

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This study determined the bending strength values of laminated veneer lumber (LVL) made with beech ( Fagus orientalis L.) veneer obtained by the peeling process and having four different moisture content values (0%/oven dry, 12%, 18%, and 25%). Bending tests were carried out in two different ways, i.e., for the flatwise and edgewise aspects of the LVL. Strain maps were created using two-dimensional digital image correlation (2 D DIC) and the samples having different moisture contents were compared. At the same time, the amount of displacement of the samples during the bending test was determined via conventional and DIC methods. Results of the study determined that the moisture content was effective in bending strength and tension zones. It was observed that increasing moisture content created homogeneous distribution of deformation. It was also observed that the data obtained by the 2 D DIC method were compatible with those obtained by the conventional method.

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Bending strength adjustments for moisture content for structural lumber

Cited by 8 publications

References 4 publications

Comparing the Building Code Sawn Lumber’s Wet Service Factors (CM) with Four Commercial Wood Species Laboratory Tests

Comparing the Building Code Sawn Lumber’s Wet Service Factors (CM) with Four Commercial Wood Species Laboratory Tests

A determination method of compressive design value of dimensional lumber

The effects of the moisture content of laminated veneer lumber on bending strength and deformation determination via two-dimensional digital image correlation

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