Project contacts are Frederico França at Mississippi State University and Robert J. Ross at the Forest Products Laboratory
With the rapid development of CLT manufacturing capacity around the world and the increasing architectural acceptance and adoption, there is a current and pressing need regarding adhesive bond quality assurance in manufacturing. As with other engineered glued composites, adhesive bondline performance is critically important. Bondline assessment requires technology in the form of sensors, ultrasonics, load cells, or other means of reliable machine evaluation.
The objectives of this cooperative study are to develop quality assurance procedures for monitoring the quality of mass timber and CLT during and after manufacturing and to develop assessment techniques for CLT panels in-service.
Project contact is Hongmei Gu at the Forest Products Laboratory
The FPL team is in charge of developing a full comparative LCA study for three multiple-story mass timber buildings and their concrete alternatives in the U.S. Northeast region, with Boston as the point location. Using these three comparative LCAs, this research will determine the GHG emissions reduction potential from mass timber use in the building sector for the U.S. region. This may increase potential for growth in wood utilization, timber harvest, and forest management practices through the market demands.
Opening new markets for the use of CLT that can capitalize on the strength and speed of construction allowed by the technology creates the best opportunity for wood product market growth. One such market is the Department of Defense (DoD), representing an estimated 148 million board feet of additional lumber production. Wood products have been significantly under-represented in the DoD construction market because of their perceived performance in blast conditions. The objectives of this project are to develop a design methodology and to demonstrate performance for exterior bearing CLT walls used in buildings subject to force protection requirements. This methodology should be published by U.S. Army Corp of Engineers – Protective Design Center to be used by engineers for designing CLT elements to withstand blast loads as determined by code requirements and specific project conditions.
Project contacts are Xiping Wang at the Forest Products Laboratory, and Xinfeng Xie at Michigan Technological University
This project is expected to reveal if cross-laminated mixed hardwood and softwood species would have bonding properties similar to softwood CLT using commercial adhesives for timber laminating. The results will provide baseline data on adhesion properties of bonding mixed northern wood species.
Manufacturing of building materials and construction of buildings make up 11% of the global greenhouse gas emission by sector. Mass timber construction has the potential to reduce greenhouse gas emissions by moving wood into buildings with designs that have traditionally been dominated by steel and concrete. The environmental impacts of mass timber buildings were compared against those of functionally equivalent conventional buildings. Three pairs of buildings were designed for the Pacific Northwest, Northeast and Southeast regions in the United States to conform to mass timber building types with 8, 12, or 18 stories. Conventional buildings constructed with concrete and steel were designed for comparisons with the mass timber buildings. Over all regions and building heights, the mass timber buildings exhibited a reduction in the embodied carbon varying between 22% and 50% compared to the concrete buildings. Embodied carbon per unit of area increased with building height as the quantity of concrete, metals, and other nonrenewable materials increased. Total embodied energy to produce, transport, and construct A1–A5 materials was higher in all mass timber buildings compared to equivalent concrete. Further research is needed to predict the long-term carbon emissions and carbon mitigation potential of mass timber buildings to conventional building materials.
Five full-scale fire experiments were conducted to observe the performance of a two-level apartment-style structure constructed of mass timber. Each level consisted of a one bedroom apartment, an L-shaped corridor, and a stairwell connecting the two levels. One of the primary variables considered in this test series was the amount and location of exposed mass timber. The amount of mass timber surface area protected by gypsum wallboard ranged from 100% to no protection. For each experiment, the fuel load was identical and the fire was initiated in a base cabinet in the kitchen. In the first three experiments, the fire reached flashover conditions, and subsequently underwent a cooling phase as the fuel load from combustible contents was consumed. The first three experiments were carried out for a duration of up to 4 h. In the fourth experiment, automatic fire sprinklers were installed. Sprinklers suppressed the fire automatically. In the fifth experiment, the activation of the automatic fire sprinklers was delayed by approximately 20 minutes beyond the sprinkler activation time in the fourth experiment to simulate responding fire service charging a failed sprinkler water system. A variety of instrumentation was used during the experiments, including thermocouples, bidirectional probes, optical density meters, heat flux transducers, directional flame thermometers, gas analyzers, a fire products collector, and residential smoke alarms. In addition, the experiments were documented with digital still photography, video cameras, and a thermal imaging camera. The experiments were conducted in the large burn room of the Bureau of Alcohol, Tobacco, Firearms and Explosives Fire Research Laboratory located in Beltsville, Maryland, USA. This report provides details on how each experiment was set up, how the experiments were conducted, and the instrumentation used to collect the data. A brief summary of the test results is also included. Detailed results and full data for each test are included in separate appendices.
Prior research showed that inward moisture diffusion from absorptive claddings such as brick veneer, stucco, or manufactured stone veneer can be significant in wood-frame walls. The inward migration of moisture is greatest when the cladding is heated by the sun after being wetted by rain. The same phenomenon is likely to occur in CLT walls with these types of claddings (Fig. 1). General guidance on CLT building envelope design was published in chapter 10 of the U.S. CLT Handbook, which cautions that inward diffusion of moisture from absorptive claddings could lead to moisture accumulation in CLT based on initial computer modeling predictions. Experimental measurements are needed to provide a stronger basis for design of CLT exterior walls.
The objectives of the project are to measure moisture conditions in CLT walls with absorptive claddings under exposure to simulated rain and sun and to identify design and construction practices that minimize the risk of moisture accumulation in different U.S. climates.
The goal of this study was to update life-cycle assessment (LCA) data associated with laminated veneer lumber (LVL) production in the Pacific Northwest (PNW) region of the United States from cradle-to-gate mill output. The authors collected primary mill data from LVL production facilities per Consortium on Research for Renewable Industrial Materials (CORRIM) Research Guidelines. Comparative assertions were not a goal of this study.
The goal of the present study was to develop life-cycle impact assessment (LCIA) data associated with gate-to-gate laminated veneer lumber (LVL) production in the southeast (SE) region of the U.S. with the ultimate aim of constructing an updated cradle-to-gate mill output life-cycle assessment (LCA). The authors collected primary (survey) mill data from LVL production facilities per Consortium on Research for Renewable Industrial Materials (CORRIM) Research Guidelines. Comparative assertions were not a goal of the present study.
Contact: C. Elizabeth Stokes, Mississippi State University, Juliet Tang, Forest Products Laboratory
Outcomes anticipated from the results of this project are biodegradation information for CLT products and an improved understanding of biodegradation differences between CLT products and comparable laminated and solid wood products. Results will benefit the emerging CLT industry and provide valuable information for market expansion into areas with high termite pressure.