Although not yet seen as common practice, building with cross laminated timber (CLT) is gaining momentum in North America. Behind the scenes of the widely publicized project initiatives such as the Wood Innovation Design Centre Building in Canada and the recent U.S. Tall Wood Building Competition, substantial research, engineering, and development has been completed or is underway to enable the adoption of this innovative building system. This paper presents a brief overview of the current status of CLT building development in North America, highlighting some recent U.S. and Canadian research efforts related to CLT system performance, and identifies future CLT research directions based on the needs of the North American market. The majority of the research summarized herein is from a recent CLT research workshop in Madison, Wisconsin, USA, organized by the USDA Forest Products Laboratory. The opportunity and need for coordination in CLT research and development among the global timber engineering community are also highlighted in the conclusions of this paper.
This study surveyed experts on Cross-Laminated Timber (CLT) on their perspectives about research with the most positive impact on the advancement of CLT as building material in North America. Results from this study show that CLT experts in North America believe that architects are relatively well informed about CLT compared with...
Cross-Laminated Timber (CLT) is emerging as a promising building system that could help revitalize a dwindling forest sector. However, little research has been conducted about CLT, particularly in the marketing realm. Our paper helps bridge this gap. Specifically, we aim to identify research areas that are important to successfully advance CLT as a building material in North America. Our findings, based on a survey of experts, suggest that the level of awareness about CLT among building professionals in general is low. However, architects are considered knowledgeable about the product. Experts consider that the most important barriers to the adoption of CLT are(a) misperceptions held by building industry professionals about wood and CLT, (b) compatibility of building codes with CLT, and (c) the availability of technical information about CLT as a construction system. In terms of most pressing research areas for advancing CLT, experts consider that it is important to shed more light on its seismic and fire performance, and also on proper connectors and fasteners used in CLT-based construction.
The report has segmented the market on the basis of application. Some of the key application areas of CLT include residential, educational institutes, government and public buildings, and commercial spaces. On a regional basis, the report has segmented the market into the US and Canada. The report has also analysed the competitive landscape of the market with some of the key players being Structurlam, Nordic Engineered Wood, SmartLam and Sterling Lumber. ...
Cross-laminated timber (CLT) is a prefabricated solid engineered wood product made of at least three orthogonally bonded layers of solid-sawn lumber or structural composite lumber that are laminated by gluing of longitudinal and transverse layers with structural adhesives to form a solid rectangular-shaped, straight, and plane timber intended for roof, floor, or wall applications. While this engineered wood product has been used in Europe for over 15 years, the production of CLT and design of CLT structural systems have just begun in North America. For the acceptance of new construction materials or systems in North America, such as CLT, a consensus-based product standard is essential to the designers and regulatory bodies. This paper describes and documents the background information and some key issues that were considered during the development of the ANSI/APA PRG 320 Standard for Performance-Rated Cross Laminated Timber. This standard was developed based on the consensus standard development process of APA-The Engineered Wood Association as a standards developer accredited by the American National Standards lnstitute (ANSI). The CLT stress classes incorporated in this product standard are also discussed. The ANSI/APA PRG 320 standard has been approved by the Structural Committee of the lnternational Code Council (lCC) for the 20'15 lnternational Building Code (lBC).
As low carbon alternatives to other building materials, mass timber products are poised to revolutionize the landscape of the built environment. They’re also helping to bolster rural economies, because stronger markets for wood products provide an incentive for public and private landowners to invest in the long-term sustainability of North American forests. With tremendous interest in the potential of CLT in particular, prompt attention has been given to its inclusion in building codes and standards, with the awareness that a great deal of research is still underway. In addition to the research described in this paper, the depth and breadth of research on CLT is spreading to embrace other mass timber systems, including the development of mechanically-laminated products such as dowel- and naillaminated timber, and the expanded use of gluelaminated timber.
The design and construction of temporary military structures has changed little since World War II. While these structures are lightweight and rapidly deployable, they require a sizeable workforce to construct and provide minimal ballistic and blast protection for occupants. Cross-laminated timber (CLT) is a relatively new prefabricated engineered wood product that is strong, stiff, quick to build, and has the potential to offer inherent ballistic and blast resistance compared to traditional wood products. The orthotropic nature of CLT coupled with the energy absorbing capacity of the thick wood panels warrant further investigation into the viability of CLT for temporary military structures. To that end, the research presented in this thesis seeks to better understand the ballistic and blast response of CLT panels and to develop evaluation criteria for the use of CLT in temporary military structures. Specific areas of investigation included: 1) experimental testing of the ballistic resistance of CLT panels, conducting in conjunction with U.S. Army laboratories in Aberdeen Proving Grounds, Maryland and Vicksburg, Mississippi; 2) the design, prototyping, and experimental testing of enhanced CLT panels to further improve ballistic performance; 3) a qualitative analysis of CLT panels under ballistic impact resistance mechanisms; 4) the development of a CLT blast analysis tool to predict the elastic response of CLT to blast loadings; and 5) the development of a simplified tool to identify evaluation criteria for temporary military structure material selection, including conventional materials as well as CLT. Specimens in this research consisted of commercially produced Spruce-Pine-Fir CLT as well as Southern Pine CLT specimens fabricated specifically for this research. Ballistic testing of both types of conventional CLT indicate that the material’s inherent penetration resistance is significantly greater than that of dimension lumber and plywood used in current common temporary military structures. The testing shows that current U.S. military design guidelines (UFC 4-023-07), used for determining required wood thickness based on ballistic threat, under predicts the ballistic performance of CLT. From testing and analysis, the thesis develops updated equations for predicting the thickness of CLT required for ballistic protection. A qualitative analysis of ballistic specimens identified local failure modes in the CLT and links the observed damage the anisotropic material properties, grading, and defects in sawn timbers. Enhanced CLT specimens were fabricated using various hardening materials including thin metal plates and gratings, polymer-based armors, and fiber-reinforced epoxy matrix panels. The enhanced CLTs were evaluated based on ease of production, ballistic resistance as compared to conventional CLT, and cost-benefit analysis. The shear analogy method was incorporated into a single-degree-of-freedom blast analysis to predict the response of different types and sizes of CLT panels under blast loads within the elastic regime. The tool was validated using field data from low-level live blast tests and showed good agreement with the field data. Finally, tailored evaluation criteria for comparative assessment of construction materials for use in temporary military structures – considering issues of cost, the logistics of in-theater deployment, energy consumption and force protection were developed and applied through using the AHP decision-making process.
Using the subject of material culture as a lens through which Japanese urban architectural history and political debates are brought into sharper relief, this thesis argues that manufactured engineered wood products like cross laminated timber (CLT) are a part of the larger ongoing discussion on how to solve urban problems and offer the ability to connect sustainable and resilient building design agendas in cities. In addition, if CLT and other wood-based materials are domestically grown and responsibly manufactured on a larger scale than exists presently in Japan, industrial productivity of wood from local forests will recover after long periods of stagnant development, a move heavily invested by the present Prime Minister Shinzo Abe and his administration.
Currently, design of tall wood buildings is generally accomplished in the USA through the so-called alternate means process, with requires extensive testing, engineering analysis, and a stringent peer review process. As it pertains to cross-laminated timber (CLT), it is critical to develop effective performance prediction models, through laboratory testing elaborating on material behaviors (e.g. hygrothermal, vibrational, etc.) as well as monitoring data on the mid- to long-term performance of timber structures in situ. This paper presents the scope and preliminary outcomes of a project aiming to cross reference laboratory research and in-situ monitoring to establish a holistic performance-monitoring protocol for mass timber buildings; this protocol can later serve to define standards for mid- to long-term monitoring as well as to develop guidelines for the design of mass timber structures.