Project contact is Frank Lam at the University of British Columbia
A continuous CLT floor/roof system that has two way bending action across multiple CLT panels will create open floor space with long spans in both major and minor directions, making mass timber construction more competitive and cost-effective. A design guide on CLT two way floor/roof system, incorporating the results from the two phases of study, will be developed at the end.
This project will document the flammability of Douglas-fir and spruce-pine-fir CLT panel assemblies produced in the United States. Tests are being conducted on wall and floor panel assemblies with standard overlapping connections and produced with two different types of commonly-used adhesives. Sensors placed throughout panels will provide data about how fire affects the interior and exterior of a panel. A thermal imaging camera will provide information on how the structural integrity of panels is affected by fire and fire suppression activities.
Project contact is Rakesh Gupta at Oregon State University
The objective of this project is to determine the fire performance of connections made up of the custom cross-laminate timber (CLT) layups utilizing ponderosa pine from logs harvested in Western U.S. forest restoration programs and produced by regional CLT manufacturers. Tests will be performed using ASTM E119 standard protocol on the CLT Connections, with CLT manufactured by the manufacturer (Vaagen Brothers) located in the Northwestern U.S. Fire testing is required before manufacturers will consider using pine in CLT. The volume of pine in high fire danger areas in the Western U.S. is much greater than that of Douglas-fir and we believe that ponderosa pine lumber can be successfully utilized in CLT panels. This project builds on previous Wood Innovation grants: Muszynski et al., (2017), Gupta et al. (2018) and Riggio et al. (2018), first two aimed at determining the fire performance and the third on demonstration of a modular structure designed for custom cross-laminate timber (CLT) layups utilizing ponderosa pine from logs harvested in Western U.S. forest restoration programs. We estimate that as few as 100 proposed modular units a year will lead to utilization of approximately 33 MMBF of pine lumber, and will allow treatment of about 460 additional acres of threatened forestland. At this rate, the harvest and manufacture of the lumber required will retain or create about 9.2 jobs/MMBF, including 57 jobs created directly for the CLT manufacturing (as estimated by Beck Group).
Project contact is Sylvain Ménard at Université Laval
Designers of large buildings generally want floor systems with large spans (9 m). These floors are often sized by the requirement of vibratory performance and, correlatively, deflection. The composite wood-concrete floors allow large spans with reduced static height. They are a promising alternative to simple concrete slabs. Objective 1 - Determine the evolution of the natural frequency of the CLT-concrete composite floor as a function of the stiffness of the connector, and correlate the experimental results with the model by the finite element method. Objective 2 - Parametric study of the vibration performance of the CLT-concrete composite floor. The impact of several parameters on the dynamic performance of the floor will be determined, especially the characteristics of the constituent materials, connector and the creep of the floor. Objective 3 - Build the metamodels for the study of multi-objective optimization optimization of a wood-concrete composite floor solution in relation to a regional problem in Aquitaine.
Project contact is Luca Sorelli at Université Laval
This project aims to develop a new precast wood / concrete floor system that can push the span limits in multi-storey wood buildings. The multidisciplinary methodology includes a finite element analysis technique using the “DDuctileTCS” software developed at CIRCERB, shear tests on connections, bending tests of the composite beam and an extension of technical standards for the design of composite structures. This project will develop solutions to optimize the composite action and vibration of long-span precast and mixed floors. The methodology consists of: (i) analysis of systems and optimization of shapes by numerical finite element techniques; (ii) connection shear tests; (iii) proof of concept on a prototype beam in the laboratory.
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.
Project contact is Christian Dagenais at Université Laval
The structural elements of a building must provide fire resistance in order to prevent collapse and to provide an escape route for occupants. The basic philosophy is that components that support elements with a degree of fire resistance must also offer the same degree of resistance. It is also assumed that the connections between these elements provide at least the same degree as the supported elements. Traditionally, heavy timber construction used ingenious construction principles and assemblies made of cast iron. With the advent of innovative fasteners (eg self-tapping screws), the principles of assembly have changed greatly and are now similar to a metal frame. So, several studies have been carried out in recent years in order to increase knowledge of the fire behavior of these assemblies (Audebert et al., 2012, Dhima 1999, Frangi et al. 2009, Peng 2010, Ohene 2014, Ali et al. 2014 , Moss et al. 2008). Although a significant amount of information is available in the literature, it often indicates short-term flammability resistance (± 30 min), which is largely insufficient for buildings having to provide a degree of fire resistance of at least 2 hours. The objective is to carry out a literature review in order to fully understand the factors influencing the fire performance of assemblies in wood construction. A model of thermomechanical behavior and a simplified analytical approach would have to be developed.
Project contacts are James Wacker at the Forest Products Laboratory, Justin Dahlberg and Brent Phares at Iowa State University
The use of cross-laminated timber (CLT) has gained popularity over the past decade, with many advances stemming from completed research and construction projects in Europe. Many inherent advantages of CLT (such as, it is prefabricated, relatively lightweight, dimensionally stable, and environmentally sustainable) have been utilized in vertical construction projects. Despite these advances, the use of CLT in bridge structures has been limited, and the adoption of CLT into governing design codes has been slow. However, CLT shows promise as a complementary or alternative construction material in bridge decks, and additional research would help characterize the structural attributes of CLT decks to guide their use in bridge projects.
Project contact is Kuma Sumathipala at the American Wood Council
The United States has a vast supply of forest biomass, which provides an abundant resource suitable for the manufacturing of mass timber products. Recent research has shown that these mass timber products can be safely implemented in tall buildings. In 2018 and 2019, this research led to changes allowing the construction of 18 story buildings with mass timber structures in the 2021 International Building Code (IBC). Although this development has created opportunities, it does not respond to recent architectural trends, as the new regulations do not allow for visible mass timber in buildings exceeding 12 stories in height and only allow for limited areas of visible Cross Laminated Timber (CLT) surface in buildings from 9 to 12 stories in height.
The strict limitation on the area of visible mass timber in 2021 IBC was based partially on fire performance of CLT manufactured to an earlier edition (2012) of ANSI/APA PRG 320. New adhesive qualification requirements in the 2018 standard have significantly improved the fire performance of CLT. This improved fire performance represents an opportunity to justify increases to code-prescribed limits on exposed mass timber areas which would respond to current, and likely future, architectural aesthetic demands, allowing for an expansion of the market for tall mass timber buildings.
In order to justify these increases in allowable exposed mass timber areas, compartment fire tests will be designed and performed to demonstrate that the fire performance of increased exposed mass timber surfaces are consistent with the (newly-recognized) International Building Code safety criterion. In addition, fire safe solutions for the intersections between exposed mass timber members and restoration of fire-damaged exposed mass timber are needed to be developed and tested. Test results and other findings will be used to develop and justify new requirements for U.S. model building codes, thereby enabling more innovative utilization of renewable U.S. forest resources in construction.