Progress 12/15/01 to 12/31/04
Outputs
The data and models developed under this grant will satisfy a portion of the information intensive requirements of service life prediction models and will be used for continued development of these models. The research investigated the single-shear mechanical properties of three nailed connection geometries of biodeteriorated oriented strand board sheathing and Douglas-fir framing members. Mechanical properties of the nailed connections including ultimate and yield strength, stiffness, and energy dissipation were evaluated at increasing levels of deterioration caused by a brown rot fungus using monotonic and fully reversed cyclic-loading. The oriented strand board sheathing specific gravity was the strongest explanatory variable for the mechanical properties and controlled the behaviour of the connection at increasing levels of fungal damage. The data showed that nailed connections in lateral force resisting systems can sustain moderate amounts of fungal damage before
a significant loss in connection capacity. Nominal design capacity and yield mode of the nailed sheathing to framing member connections with fungal damage can be estimated by using the existing yield model equations for dowel-type connections if the dowel bearing capacity of the decay-damaged wood materials is known. Near infrared spectroscopy in combination with multivariate statistical methods was used to develop predictive models for weight loss, shear strength, dowel bearing capacity and solubility. The near infrared spectroscopy methods showed considerable promise as a condition inspection tool. Graduate Student = 1.
Impacts
Designing for durability requires the quantification of changes in building materials and the performance of the structures. If wood is to become a truly engineered material and compete with other framing materials and systems, durability issues must be addressed and appropriately accounted for in design. This research quantified the effects of in-service deterioration due to microbial and hygroscopic mechanisms on the performance of contemporary wood-frame construction.
Publications
- Kent, S.M., R.J. Leichti, J.J. Morrell, D.V. Rosowsky and S.S. Kelly. 2005. Analytical tools to predict changes in properties of oriented strandboard exposed to Postia placenta. Holzforschung. (In press).
- Kent, S.M., R.J. Leichti, D.V. Rosowsky and J.J. Morrell. 2005. Effects of decay on the cyclic properties of nailed connections. Journal of Materials in Civil Engineering. (In press).
- Kent, S.M., R.J. Leichti, J.J. Morrell and D.V. Rosowsky. 2004. Effects of wood decay by Postia placenta on the lateral capacity of nailed oriented strand board sheathing and Douglas-fir framing members. Wood and Fiber Science 36(4):560-572.
- Kent, S.M., R.J. Leichti, D.V. Rosowsky and J.J. Morrell. 2004. Biodeterioration effects of nailed connections. p. 583-588 In: Proc., 8th World Conference on Timber Engineering, Vol 2, June 14-17, Lahti, Finland. Finnish Association of Civil Engineers, Helsinki, Finland.
- Leichti, R.J., J.J Morrell and D.V. Rosowsky. 2004. Effect of decay on wall system behavior. Proc., Woodframe Housing Durability and Disaster Issues, October 4-6, Las Vegas, NV. Forest Products Society, Madison, WI. (In press).
- Leichti, R.J., S.M. Kent, J.J. Morrell and D.V. Rosowsky. 2004. Nailed connections subjected to microbial deterioration. p. 29 In: Biographies & Abstracts, session 12. Forest Products Society 58th Annual Meeting, June 27-30, Grand Rapids, MI. Forest Products Society, Madison, WI.
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Progress 01/01/03 to 12/31/03
Outputs
A review of the literature on the resistance of wood composites was written. Wood composites that develop a network of internal voids when exposed to high moisture levels, such as oriented strand board, laminated strand lumber, particleboard, and fiberboards, tend to be more susceptible to fungal deterioration than solid wood of the same species. Composites such as plywood, laminated veneer lumber tend to be more durable than solid wood of the same species due to inhibitory compounds in the adhesives and low permeability across gluelines. There is little data relating weight loss and mechanical property reduction for wood composites suggesting the need for further testing to more clearly determine the effects of fungal attack on engineering properties of wood composites. The effect of decay on the fully-reversed cyclic load performance of nailed oriented strand board sheathing to Douglas-fir framing member connections was investigated. The connection geometry
evaluated in this study is representative of the lateral force resisting systems of light-framed wood structures including shearwalls and diaphragms. Maximum loads, slip at maximum loads, yield loads, initial stiffness, and cumulative energy dissipation of nailed connections exposed for increasing time intervals to the brown rot fungus, Postia placenta, were characterized in the tensile and compressive directions using a fully-reversed cyclic loading. The OSB sheathing specific gravity was the best descriptive variable for the mechanical properties measured in this study. Cumulative energy dissipation was the connection property most affected by decay damage.
Impacts
Designing for durability requires the quantification of the changes in the building materials and the performance of the structure. If wood is to become a truly engineered material and compete with other framing materials and systems, durability issues must be addresses and appropriately accounted for in design. This research will quantify the effects of in-service deterioration due to microbial and hygroscopic mechanisms on the performance of conventional woodframe construction.
Publications
- Kent, S.M., R.J. Leichti, D.V. Rosowsky and J.J. Morrell. 2003. Effects of wood decay by Postia placenta on the lateral capacity of nailed oriented strand board sheathing and Douglas-fir framing members. Wood and Fiber Science. (In press).
- Kent, S.M. 2004. The effect of biological deterioration on the performance of nailed oriented strand board sheathing to Douglas-fir framing member connections. Ph.D. Dissertation. Oregon State Univ., Corvallis. 189 pp.
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Progress 01/01/02 to 12/31/02
Outputs
The project was initiated and a graduate student was awarded a research assistantship to work in support of this grant. A preliminary study was conducted to refine the terms of the planned experiment. Issues related to methods of specimen assembly, sterilization, fungal efficacy, and duration of exposure were investigated. Fixtures required for the tests were designed and fabricated, test protocols were written, and methods of data analysis were defined. The preliminary study took approximately 25 weeks. In the second half of the year, the planned experiment was initiated. The test specimens were fabricated, inoculated, and then placed in the growth environment. At the end of the year, the control specimens (no treatment) had been tested and the first set of specimens (treated and water/sterilization only) were harvested after five weeks of exposure in the hot (30 degrees C)/wet (85 percent rh) environment. The dependent treatment variables were static lateral nail
resistance test and energy dissipation as determined by using a quasi-static fully-reversed cyclic test method. Preliminary statistical results show that there is no effect due to fungi after the five-week period of exposure. This year, the experiment will continue with specimens being harvested at five week intervals until the 20 week limit, which was shown by the preliminary experiment to be a reasonable termination point. Testing for lateral nail and quasi-static properties will be conudcted after each harvest period.
Impacts
(N/A)
Publications
- Leichti, R.J., S.M. Kent, R. Staehle, C. Freitag, J.J. Morrell and D.V. Rosowsky. 2002. Durability in light-frame wall assemblies. p. 23 In: Biographies and Abstracts. Forest Products Society Annual Meeting, Madison, WI. Forest Products Society, Madison, WI.
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