Creep Behavior Model for Structural Lumber

Fridley, Kenneth J.; Tang, R. C.; Soltis, Lawrence A.

doi:10.1061/(asce)0733-9445(1992)118:8(2261)

Cited by 61 publications

(21 citation statements)

References 4 publications

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“…Parameters which can influence the creep deflection are the level of applied stress, temperature, loading time, the moisture content MC and its variation (Lopes 2013, Fridley et al 1992, Norimoto et al 1992, Bengtsson and Kliger 2003, Lagana et al 2008. However, the most important for the mechano-sorptive effect MSE in structures of wood can be defined by the combined effect of the main factors (loading time and variation of MC), which is the fastest (just a couple of weeks of duration) and detrimental way to conduct creep experiments at laboratory (Mårtensson 2003).…”

Section: ( )mentioning

confidence: 99%

Scaling and modeling the creep of Eucalyptus globulus

Lopes¹,

Matos²

2019

Maderas, Cienc. tecnol.

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Eucalyptus, with the commercial name of Blue gum, is a viscoelastic material strongly influenced when under constant load (creep), being this phenomenon -in the context of displacements -exacerbated with transient relative humidity (variations of the water content in the wood material).The evaluation of bending creep was done in indoor / constant and transient humidity conditions. In the latter, mechano-sorptive effect, the creep bending tests were done for a period of 60 days with cycles of wetting-and-drying. Each cycle has 7 days of duration. Defect free specimens with dimensions of 20 x 20 x 400 mm 3 (approximately to the scale 1:10) of Eucalyptus globulus wood species were used.To fit the creep behaviour and extrapolate results for different periods (1, 10 and 50 years) a survey of different numerical models was done. Rational, parabolic and polynomial functions were chosen.In bending, Blue gum wood species presented a behaviour without a creep limit, therefore labile. Through the models used for extrapolations a significant variability was found for different periods. Values of the main standard of wood design (Eurocode 5) were exceeded. The most consistent mathematical model was the rational model because it is the one that has led to closer and stable results.

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Section: ( )mentioning

confidence: 99%

Scaling and modeling the creep of Eucalyptus globulus

Lopes¹,

Matos²

2019

Maderas, Cienc. tecnol.

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“…There is a continued interest in providing experimental and theoretical understanding of the MS phenomena for wood and woodbased products (Montero et al 2012;Ozyhar et al 2013;Gril 2015;Jin et al 2016;Pérez-Pena et al 2016). The MS deformation of composite lumber, plywood, and OSB has been investigated (Szabo and Ifju 1970;Leicester 1971;Schaffer 1972;Yeh 1990;Fridley et al 1992;Fridley and Tang 1992;Tang et al 1997;Lee 1999). It is a complex phenomenon involving several factors, such as moisture, hygroscopic swelling, mechanical stress, and the variation of the viscoelastic response of the specimen as a function of time.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the stress level varies even under a constant load, due to sample dimensional change under varying relative humidity (RH) conditions. Most MS deformation studies of structural lumber did not reflect the thickness swelling (TS) of specimens in their analysis (Ranta-Maunus 1975;Mukudai and Yata 1988;Hunt 1989;Fridley et al 1992;Shen and Gupta 1997) due to small TS values. However, it was shown that the TS values of the MS deformation specimens in flatwise bending were not negligible compared with the values of actual MS deflection .…”

Section: Introductionmentioning

confidence: 99%

Mechano-sorptive Deformation of Borate Modified Strand Board for Structural Uses

Li¹,

Sun

Lee

et al. 2017

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Structural performance of chemically modified oriented strand board (OSB) has drawn great attention from builders, home insurance companies, and panel manufacturers. This study was conducted to provide time-dependent creep and moisture change-induced mechano-sorptive (MS) effect data from borate-treated and randomly formed strand board. The strand boards were lab-fabricated with flakes from southern yellow pine and mixed hardwoods. Commercial liquid phenol-formaldehyde resin was used as the binder. The treatments involved in the study were one level of zinc borate, one level of calcium borate, and two species groups that included separate controls. The load level, equivalent to 25% of the static bending modulus of rupture, was selected as a long-term constant load. Creep at 65% constant relative humidity (RH) developed in a normal time-dependent fashion and the Burger body creep model with four spring-dashpot elements was found appropriate to predict the creep response of borate modified strand board. Noticeable influence of borate modification on the fractional deflection was demonstrated under changing RH for both the absorption and desorption cycles. The measured fractional deflection due to the MS effect followed a linear relationship with moisture content change. The established material constants for various strand boards provided a way to predict the structural performance of treated strand board under varying RH conditions.

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“…Designers, manufacturers, and consumers should be informed of performance requirements for borate treated OSB with the guideline for service life and defl ection limits under long-term mechanical and changing environmental loading conditions. Extensive research has been conducted to investigate creep behavior of structural wood composite panels including plywood, waferboard, and OSB (e.g., Leichti and Tang 1987;Fridley et al 1992;and Laufenberg et al 1994). Information on creep behavior of the panel products was summarized by Bach (1993), Palka (1993), andCheng et al (1994).…”

Section: Introductionmentioning

confidence: 99%

“…Information on creep behavior of the panel products was summarized by Bach (1993), Palka (1993), andCheng et al (1994). For OSB, some studies emphasized the effects of wood species and climatic conditions on its creep performance (Leichti 1986, Yeh 1990, Fridley et al 1992, while others focused on the effect of resin type and press parameters on the creep (Lee 1999). The results of these studies have provided wood structural designers and technologists with information regarding to the long-term mechanical performance of structural composite panels.…”

Section: Introductionmentioning

confidence: 99%

Creep Behavior of Borate-Treated Strandboard: Effect of Zinc Borate Retention, Wood Species, and Load Level

Lee

Cai

et al. 2009

Maderas, Cienc. tecnol.

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Creep performance of zinc borate-treated strandboard from southern pine (Pinus taeda L.) and red oak (Quercus falcata) was investigated at 25°C temperature and 65% relative humidity. It was shown that the borate treatment had some signifi cant effect on creep defl ection of the test panels, and the effect varied with wood species. There was no signifi cant effect of creep loading on residual bending properties of treated strandboard under the stress levels used. The four element spring-dashpot creep model fi tted the creep data well. The predicted creep defl ection for a 10-year loading duration under both 15% and 40% stress levels met the National Design Specifi cation for Wood Construction despite of the noticeable borate treatment effect on creep. Future work is needed to study the creep behavior under combined mechanical and moisture loadings for treated structural panels.

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Creep Behavior Model for Structural Lumber

Cited by 61 publications

References 4 publications

Scaling and modeling the creep of Eucalyptus globulus

Scaling and modeling the creep of Eucalyptus globulus

Mechano-sorptive Deformation of Borate Modified Strand Board for Structural Uses

Creep Behavior of Borate-Treated Strandboard: Effect of Zinc Borate Retention, Wood Species, and Load Level

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