Wood and Fiber Science (E-Journal)
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Technical Note: Lateral Connections and Withdrawal Capacity of Western Juniper
Full text linkThe goal of this project is to increase the amount of available information about western juniper wood to encourage its use in structural applications. This project evaluated the performance of connections involving western juniper wood and other common wood-based building materials. The tests for this project included edge lateral nail connection tests (ASTM 2007a), dowel bearing strength tests (ASTM 2007c), and withdrawal tests (ASTM 2007b). The performance of juniper and juniper-oriented strand board (OSB) connections were characterized. The results were also evaluated against predictive design equations found in the National Design Specification (NDS). The data obtained in this study suggest that NDS equations conservatively predict the load-carrying capacity of a juniper-OSB connection but consistently predict the failure mode.
APPARATUS FOR GRAVIMETRIC MEASUREMENT OF MOISTURE SORPTION ISOTHERMS FOR 1-100 g SAMPLES IN PARALLEL
Full text linkThis article presents a new apparatus for collecting water vapor sorption isotherms in parallel with example data from acetylated and thermally modified loblolly pine. The experimental setup consists of an enclosure that is continuously flushed with a carrier gas of known RH supplied by an RH generator and a balance with precision of 0.1 mg. All samples are placed on the balance and the mass is monitored as a function of time. At a given RH, the measurements are stopped when the change in the total mass of all samples are less than or equal to a change in MC of 0.1 mg g1 min1 (0.000 01%) per minute over a 24 h window. The sorption isotherms effectively differentiated the wood modifications; isotherm models fit the data extremely well (R2 0.95 for all treatments). A comparison of the data with measurements on the same specimens conditioned over saturated salt solutions shows that the method is comparable with isotherms acquired over saturated salts. When compared with the saturated salt solution method for collecting isotherms, this method requires less labor. Furthermore, unlike traditional dynamic vapor sorption methods, this apparatus easily allows multiple macroscopic samples to be run in parallel.
DEFECT DETECTION AND QUALITY ASSESSMENT OF HARDWOOD LOGS:PART 2—COMBINED ACOUSTIC AND LASER SCANNING SYSTEM
Full text linkThe objective of this study was to determine the technical feasibility of combining acoustic wave data with high-resolution laser scanning data to improve the accuracy of defect detection and quality assessment in hardwood logs. Using acoustic impact testing and high-resolution laser scanning techniques, 21 yellow-poplar logs (Liriodendron tulipifera) obtained from the central Appalachian region were evaluated for internal and external defects. These logs were then sawn into boards and the boards were visually graded based on the National Hardwood Lumber Association grading rules. The response signals of the logs from acoustic impact testing were analyzed to extract time-domain and frequency-domain parameters. The laser scan data of each log was processed by a defect detection system. The results indicated that acoustic velocity, time centroid, damping ratio, and the combined time- and frequency-domain parameters are all effective quality predictors of the hardwood logs in terms of internal soundness. High-resolution laser scanning is complementary to acoustic impact testing. Acoustic parameters combined with laser scanning results provide a more complete data picture of the log: size, shape, surface defects, and degree of soundness. Indications of soundness in a particular log allow the internal prediction system to flag suspicious defects as potentially unsound. Thus, a combined system would be able to discriminate much more precisely with respect to log quality and potential board grade yields than would either method independently
EFFECT OF SITE CHARACTERISTICS ON JUVENILE WOOD TRANSITION IN LODGEPOLE PINE IN THE INLAND NORTHWEST
Full text linkJuvenile wood (core wood) in softwood species is typically characterized as being less dimensionally stable and having lowermechanical properties thanmature wood.Determining the age of transition between juvenile wood and mature wood is important when making judgments about utilization options for naturally occurring stands of trees in the intermountain west region of the United States. Lodgepole pine (Pinus contorta Dougl. ex. Loud.) trees were harvested from four different sites in the US Inland Northwest to include site variations that affect growth, such as elevation, precipitation, and length of growing season. Longitudinal shrinkage was measured in each sample as it dried fromgreen to oven-dry conditions. Later, averagemicrofibril angle was determined for the same samples. Although the two methods for estimating the juvenile wood transition period were not in agreement regarding the number of years to mature wood, there was agreement in a ranking of the four sites from shortest transition period to longest transition period. A significant difference in the juvenile wood transition period was found among sites; longer transition periods were attributed to stands in which trees exhibited persistent lower branches rather than to geographic influences. Thiswork illustrates that stand conditions for sources of lodgepole pine can have a substantial influence on physical characteristics of this material when it is used as structural roundwood or solid-sawn products.
Influence of Four Coatings on the Mold-Resistance and Combustion Performance of Decorative Bamboo Curtain
Full text linkDecorative bamboo curtain (DBC) is a kind of bamboo product made of bamboo filaments by weaving or applying adhesive, and is becoming popular as an interior decorative material with a disadvantage of mildew. In this study, four antimold coatings, including wax oil (WO), polyurethane varnish (PV), silicone acrylic emulsion (SE), and SE with 3-iodo-2-propynyl butylcarbamate (SI), were applied to improve the antimildew capability of DBC. The resistance to mold fungi performance was evaluated using the Chinese National Standard GB/T 18261-2013, and combustion performance of DBC was analyzed by cone calorimetry. The results showed that the SI coating group had the best antimildew performance with an efficacy of 100%. SE and PV coatings had the worst performance. The antimildew performance of the WO coating was almost the same as that of the PV coating. External thermal radiation, composition of pyrolysis, and pyrolysis rate of the antimold coatings and DBC were completely different. During the combustion process, all coated groups showed a tendency to increase total heat release (THR). The THR of the WO and PV groups increased 22.22% and 13.33%, respectively; the THR of the SE and SI groups both increased by 4.44%. Total smoke production and specific extinction area values decreased slightly in the SE and SI groups, whereas those in the WO and PV groups showed an increasing trend. The SI group was very suitable to be used as antimold coatings on the surface of DBCs because of its best antimildew performance and smoke suppression
RESEARCH ON CUTTING FORCES AND CUTTING TEMPERATURE IN ORTHOGONAL CUTTING SOFTWOOD AND HARDWOOD PARALLEL TO GRAIN
Full text linkExperimental results showed that the cutting force and cutting zone temperature of soft pine were lower than that of hard oak under the same cutting condition, and the influence degree of chip type on the cutting force of soft pine is lower than that of hard oak. Different chip formation shows little or no effect on cutting temperature in processing both soft pine and hard oak
DURABILITY OF MASS TIMBER STRUCTURES: A REVIEW OF THE BIOLOGICAL RISKS
Full text linkMass timber structures have the potential to change wooden construction on a global scale. Numerous mass timber high-rise buildings are in planning, under development or already built and their performance will alter how architects and engineers view wood as a material. To date, the discussion of material durability and biodegradation in these structures has been limited. While all materials can be degraded by wetting, the potential for biodegradation of wood in a mass timber building requires special consideration. Identifying and eliminating the conditions that might lead to this degradation will be critical for ensuring proper performance of wood in these structures. This article reviews and contrasts potential sources of biodegradation that exist for traditional wood construction with those in mass timber construction and identifies methods for limiting the degradation risk. Finally, future research needs are outlined
FIRE DESIGN OF CLT IN EUROPE
Full text linkThe fire safety design of cross-laminated timber (CLT or X-Lam) in Europe is governed by the Construction Products Regulation and its essential requirements, as for all other building products. These requirements are mandatory, to be used in all European countries. They include classification systems for reaction to fire of building products, fire resistance of building elements, and structural Eurocodes. The reaction-to-fire performance of CLT in accordance with the European classification system is specified. Higher classes can be reached by chemical treatments, but the durability of the reaction-to-fire performance needs to be fulfilled according to a new European system. The fire resistance design of CLT building elements is not included in Eurocode 5, the structural Eurocode for timber, but can be either tested according to European standards or calculated by using design methods being developed recently. This article provides information about both reaction to fire and fire resistance of CLT in Europe
Color Changes, EMC and Biological Resistance of Thermally Modified Yellow Poplar
Full text linkLiriodendron tulipifera L., known as yellow poplar, are fast-growing trees, make up about 17% of commercially available hardwood in North America, and are generally used in furniture, doors, and millwork. The wood is used mostly where it would be hidden or painted. The value of yellow poplar is less than that of other hardwoods with more pronounced grain and color. This study evaluated the effect of various levels of thermal treatment on color and resistance to decay fungus and termites of yellow poplar wood. Boards (28.57 mm thickness150 mm width3.65 m length) were taken from a sawmill and thermally modified at temperatures of 180°C, 200°C, and 220°C. A summary of the findings were that thermal treatment caused: 1) darkening and reddening of yellow poplar wood; 2) a reduction of up to 51.4% in EMC when exposed to 21°C and 65% relative humidity, and 3) a significant increase in wood decay resistance against decay fungus Pycnoporus sanguineus. Treatment at 220°C resulted in a change in American Society of Testing Materialswood decay resistance class from slightly resistant to highly resistant; and no significant changes in resistance against the dry-wood termites Cryptotermes brevis were found