A user-friendly cross-laminated timber (CLT) design tool called SAM-CLT was developed to calculate the minimum design values for custom CLT panels. Custom panels are those made from different species not currently included in APA PRG 320 and include the use of multiple species in a panel. The tool uses the design value of hardwood and softwood lumber published in the national design specification book to design custom CLTs and the standard CLT grade lumber specification values published in PRG 320 standard. SAM-CLT was designed based on the shear analogy model and is intended to assist CLT manufacturers, construction and design companies, and researchers in designing and evaluating CLTs’ deformation when using different lumber types and thicknesses. This project included the calibration and validation of the tool, followed by examples of its use by computing the design value of the softwood, hardwood, and softwood–hardwood hybrid CLTs. The SAM-CLT tool was adjusted to match the published standard design values on PRG 320 and validated by comparing output for standard CLT layups. In the next step, SAM-CLT tool was used to calculate the minimum design value of custom CLTs made from hardwood–yellow poplar lumber and softwood–southern yellow pine lumber. Based on observed validation results of the tool and its application results to determine the design values for various CLT layups, this project concludes that SAM-CLT can be a valuable tool for designing custom CLTs, evaluating CLTs’ strength properties, and promoting heterogeneous lumber types in CLT manufacturing.Abstract
Although the contact probe measurement technique is excellent for wood surface roughness measurement, it is necessary to reevaluate the advantages and future development direction of optical measurement techniques in this field, given the emergence of optical measurement techniques such as laser technology and the increasing academic interest in wood surface roughness. The traditional review method, due to its rather limited research directions, only provides a macroscopic and qualitative description of certain laws and conclusions. The purpose of this review is to use the bibliometrics theory and method to comprehensively sort out the research hot spots in this field and explore them in depth.Abstract
Southern pine is one of the most important softwood resources in the United States, and the majority of southern pine is for lumber production, more specifically for construction. The lumber used for construction is required to meet strength-specifications as a method of ensuring the strength values within different classes. Most of the southern pine lumber is visually graded, which is based on knot, slope of grain, and wane. However, the presence of pith is not included in the visual grading system. The presence of pith indicates presence of juvenile wood, which has a negative effect on mechanical properties. The objective of this study was to evaluate the effect of pith on rings per inch, percentage of latewood, modulus of elasticity (MOE), and modulus of rupture (MOR) in 292 samples of southern pine No. 2 2 by 8 lumber. Lumber without pith had significantly greater MOE (11.1 vs. 10.0 GPa), MOR (39.7 vs. 36.4 MPa), and specific gravity (12% moisture content [MC]; 0.55 vs. 0.52) than did lumber with pith. The results show that the presence of pith is an important factor that can improve lumber grading, and it could be included in the visual grade system.Abstract
While environmental nongovernmental organizations (NGOs) have been active in China in promoting forest certification, Chinese consumers’ perceptions of certified wood products in the marketplace are unclear. A survey focused on consumers’ wood-product consumption patterns was conducted in three cities—Beijing, Guangzhou, and Shanghai—from July to August 2015. This study used data from the survey to assess urban Chinese consumers’ attitudes toward certified wood products and the demographic differences affecting these attitudes. Regression analysis was conducted to test whether consumers’ social-economic characteristics link with their attitudes toward certified wood. We found mixed correlations between these consumers’ attitudes and their demographics and positive correlations between their attitudes and exposure to environmental campaigns and environmental education. The results from this study will improve the understanding of Chinese consumers’ attitudes toward certified wood products and help producers and marketers better understand the market potential for certified products and more efficiently meet consumers’ needs. This study will also help NGOs interested in conservation to develop their future programs in China.Abstract
To expand the use of cross-laminated timber (CLT) to exterior applications, there is a need to protect the panels from biodegrading agents such as fungi and termites. Pressure treatments are effective methods of increasing the durability of wood and wood-based products; however, studies on pressure-treated CLT are limited. In this study, preservative-treated CLT samples from prefabricated CLT panels were prepared and impregnated with Cu-based preservatives through a conventional vacuum-pressure process. The effects of panel layup (3-ply parallel, 3-ply perpendicular, and 5-ply parallel) and preservative treatment (untreated [control], copper azole-type C [CA-C], and micronized copper azole-type [MCA]) on the bonding performance were investigated. Panel layup and preservative treatment had a significant influence on the block shear strength and percentage of wood failure (WFP) of the treated panels. Overall, approximately 60 percent of the block shear specimens had a WFP of >75 percent. However, fewer than 10 percent of the delamination specimens met the ASTM D2559 (2018) limitation of 1 percent for softwood used in outdoor applications. ASTM D2559 counts shallow wood failure as delamination, which could have been a reason for the high delamination rate. The percentage of wood failure and the high rate of delamination could be due to the moisture-induced adhesion failure resulting from the pressure-treatment process. The preservative pressure-treatment of the CLT panels increased the moisture content (MC) from 12–15 percent to approximately 85 percent MC, and the severe swelling of the panels during treatment might have imposed a high stress on the bond line. However, no noticeable delamination of the panels was observed during the actual treating phase of the study. These results show the feasibility of treating prefabricated CLT panels with CA-C and MCA preservatives without compromising the bonding strength.Abstract
The wood of African mahogany (Khaya spp.) is known for its high quality and similarity to the more expensive Brazilian mahogany (Swietenia macrophylla King). Interest in African mahogany has been increasing because of the reduced availability of native Brazilian mahogany, which has become illegal to harvest. Most African mahogany comes from managed plantations, so the increased consumption of this wood helps to alleviate issues related to illegal harvesting by reducing the trade of Brazilian mahogany. African mahogany has also been gaining popularity in the United States, particularly for use in the wood flooring market. However, there is lack of technical information on the properties of African mahogany material available in the US market, therefore, the objective of this work was to describe anatomical features, evaluate physical–mechanical properties and examine natural resistance of African mahogany wood that is commercially available in the US market. The results of this research provides an increase in knowledge on African mahogany wood properties, natural resistance, and provides technical information that is needed by industry.Abstract
The Internet is composed of >50 billion Web pages and grows larger every day. As the number of links and specialty subject areas increases, it becomes ever more difficult to find pertinent information. For some subject areas, special purpose data crawlers continually search the Internet for specific information; examples include real estate, air travel, auto sales, and others. The use of such special purpose data crawlers (i.e., targeted crawlers and knowledge databases), also allows the collection and analysis of agricultural and forestry data. Such single-purpose crawlers can search for hundreds of keywords and use machine learning to determine whether or not what is found is relevant. In this paper, we examine the design and data return of such a specialty knowledge database and crawler system developed to find information related to urban wood utilization—products made from timber harvested in cities and municipalities. Our search engine uses intelligent software to locate and update pertinent references related to urban wood as well as to categorize information with respect to common application and interest areas. At the time of this publication, the urban wood knowledge database has cataloged >700 publications regarding various aspects of urban wood.Abstract
The effect of foam core density on the strength of structural insulated panels (SIPs) was investigated herein as part of a larger study to determine the creep performance of SIPs. Two depths (16.5 cm and 31.1 cm [6.5 in. and 12.25 in.]) of SIPs were tested in 1/3rd-point flexure according to the American Society of Testing and Materials standard ASTM D6815. Parent SIP panels, each approximately 122 cm (48 in.) wide, were manufactured by a SIPA member in accordance with ESR 4698 and sawn into beam, type elements, each approximately 29.8 cm (11.8 in.) wide, for mechanical testing. All specimens had discontinuities in the foam core in a location that was subject to high shear stress, i.e., between the reaction support and the load head, during the bending tests. The foam density in half of the specimens was approximately 0.016 g/cm3 (1.0 lb/ft3) and in the other half of the specimens, it was approximately 0.019 g/cm3 (1.2 lb/ft3). The flexural properties of these specimens based on the maximum load, Pmax and deflection at failure Δymax (two different depths and two different foam densities) were statistically compared by 2-tailed t test. The results showed that foam density affects the bending performance of SIPs. In both depths, beams with heavier foam cores were stronger for the specific test conditions used in this study. It is noted that results may not be applicable to other design situations such as SIPs subjected to uniform loading with randomly placed foam core joints.Abstract
Forest carbon stock changes are routinely reported at the national level. Such accounting usually includes carbon sequestered by live trees and stored in living and dead trees, litter, and soil. The carbon stored in harvested wood products (HWPs), while in use and after disposal, may also be reported. However, wood products may provide a further indirect carbon benefit by providing an alternative to materials that require relatively large inputs of fossil-derived carbon. This “substitution impact” of HWPs is not explicitly considered in national reporting for forest carbon accounts because it is not directly comparable with absolute emissions and removals. However, the substitution impact is avoided fossil emissions, which do affect the net climate impact of wood use. Here, we estimate the total substitution impact for wood products harvested recently from forests in the United States. The total substitution impact is based on reported volumes of national wood production and the substitution factors for individual products. The substitution factors are obtained from comparative life-cycle assessments of specific wood products and their nonwood alternatives. The total substitution impact for wood products in the United States in 2020 was 188 TgCO2 equivalents. Calculation of substitution factors is challenged by assumptions about the use of wood products and their alternatives and by limited availability of current and specific life-cycle assessment data; however, our findings indicate that the substitution impact of forest products are a relatively important component of the carbon benefits of wood-based products.Abstract
Lumber is the main raw material for cross-laminated timber (CLT) production, accounting for up to 80 percent of the cost. The availability, quality, and price of lumber are critical factors that influence the completion of CLT projects in the United States. Although structural-rated CLTs are made from structural-grade lumber available in the commodities market, CLT mills have additional requirements to process the lumber more efficiently. These requirements increase production costs, affecting the supply chain, delaying production schedules, and increasing project completion times. This study aims to identify the differences in the lumber supply-chain practices for CLT manufacturing in the United States and Austria. The authors used the case-study survey with convenience sampling method to describe how CLT mills work with suppliers, their delivery preferences, quality-control practices, and current critical issues in each country. The study shows significant differences in lumber procurement and quality monitoring between CLT mills in the United States and Austria. Although the quality of lumber supplied to Austrian CLT mills does not require additional preparation, the quality of lumber in the United States significantly affects production efficiency and cost. To address the lumber supply-chain problems in the United States for CLT production, the authors recommend sorting lumber from the current market to meet minimum requirements and introducing a new lumber grade specifically for CLT mills. Furthermore, adopting the Austrian practice of mass-producing blank CLTs can provide a continuous supply of lumber from sawmills or distributors and increase collaboration opportunities with suppliers and producers.Abstract
As a material used in building construction, structural insulated panels (SIPs) deflect under flexural loading and creep over time. This work examines the deflection behavior of full-scale SIPs that were tested in bending. Approximately half of the matched specimens were tested after production and the other half were tested after a 90-day creep test. Of primary interest was the deflection behavior of the SIPs under load. After testing, the deflection was apportioned between the bending stiffness of the oriented strand board (OSB) and the shear modulus of the foam. Results indicated that when the known OSB modulus of elasticity values of 664,000 psi and 931,000 psi were considered among the different SIP thickness and treatments (with and without creep testing), the shear-based deflection from the foam ranged from 44 to 73 percent of the overall deflection. The calculated foam modulus of rigidity decreased slightly but significantly after creep testing. Also, the shear-based foam deflection increased slightly but significantly after creep testing.Abstract