Natural Decay Resistance of Glued-Laminated Beams

by Stephen L. Quarles, Univ of California Forest Products, Lab, Richmond, United States,
Kevin A. Flynn, Univ of California Forest Products, Lab, Richmond, United States,
William A. Dost, Univ of California Forest Products, Lab, Richmond, United States,
Mark G. Dietz, Univ of California Forest Products, Lab, Richmond, United States,



Document Type: Proceeding Paper

Part of: Structures Congress XII

Abstract:

The natural decay resistance of untreated Douglas-fir heartwood specimens sampled from glued-laminated beams was evaluated using a modified agar plate test modeled after the European Standard Method EN-113 (1982). One set of samples was obtained from beams that had been in service in an outdoor (exposed) environment for approximately 23 years, and another set from beams that had been in service in the same location for approximately nine years. The specimens were exposed to brown-rot decay fungi (Gloeophyllum trabeum and Postia placenta) for approximately seven weeks. Selected physical properties and anatomical characteristics, such as relative density, growth rate, and proportion of sapwood in each lamination, were measured. Results of the physical property tests and anatomical measurements were used to systematically allocate specimen material to the agar plate tests. Results of the physical property and anatomical characterization evaluation, and the agar plate tests are discussed. Between the sample sets, no significant differences were found in sapwood content, mass loss, and consequently natural decay resistance. Differences in relative density and growth rate were evident. Poor detailing was likely that cause of the rapid decay observed.



Subject Headings: Plates | Decomposition | Load and resistance factor design | Laminated materials | Beams | Wood beams | Material tests | Microbes

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