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.
Midply shear wall, which was originally developed by researchers at Forintek Canada Corp. (predecessor of FPInnovations) and the University of British Columbia, is a high-capacity wood-frame shear wall system that is suitable for high wind and seismic loadings. Its superior seismic performance was demonstrated in a full-scale earthquake simulation test of a 6-storey wood-frame building in Japan (Peietal.,2010). Midply shear wall, however, had limited applications due to its low resistance to vertical load and difficulty to accommodate electrical and plumbing services. For broader applications of Midply shearwall, these limitations needed to be addressed.
In collaboration with APA–The Engineered Wood Association and the American Wood Council (AWC), a new framing arrangement was designed to increase the vertical load resistance of Midply shearwalls and make it easier to accommodate electrical and plumbing services. Consequently, structural, fire and acoustic tests have been conducted to evaluate various performance attributes of Midply shear wall with the new framing configuration. This InfoNote provides a summary of the structural, fire and acoustic performance of Midply shearwalls from the tests.
The increasing use of cross laminated timber (CLT) panels in large multi-story buildings has highlighted the structural performance of CLT in fire as a critical issue concerning life safety and serviceability. It is well-known that wood material strength decreases when exposed to elevated temperature for an extended period of time. For CLT panels, another level of complexity lies in the mechanical properties of the glued interface under high temperature. In this study, the tensile strength of typical North American wood species and shear strength of the glued interface of commonly used adhesives in CLT production were evaluated at different levels of elevated temperatures. The researchers systematically tested glue interface and wood samples in a controlled temperature chamber and obtained the load-deformation curves of the specimens until failure was observed. A total of five temperature levels were tested, with three wood species and four wood adhesive types. The glued interface strength was also compared to wood material strength itself under different temperatures. For each test, multiple samples were tested to ensure statistical significance of the results. The ultimate objective of this study is to develop a mechanistic model for CLT panels that can take into account the effect of temperature. In this paper, only the design, execution, and results from the elevated temperature tests are presented.
Tornadoes are some of the most severe and devastating natural events and cause significant damage to structures in the United States. Light-frame wood residential structures have shown vulnerabilities to these events, but they are not explicitly addressed in the design requirements due to their infrequent occurrence, relatively small impact area (compared to hurricanes), and complex wind profile. This paper explores the potential of Cross-Laminated Timber (CLT) to serve as a residential building material, specifically with regards to its performance in tornado events. CLT is an engineered wood product made when orthogonal layers of dimensioned lumber are glued to create panels. To compare the tornado performance of CLT buildings, six archetype residential buildings were each designed using CLT and light-frame wood in accordance to the appropriate US building code provisions and engineering principles. The capacity of each of the structural components was simulated using Monte Carlo Simulation based on the panel spans and connections of the panel boundaries. In addition, the resistance to structure sliding and combined uplift and overturning was simulated using engineering principles based on the load path of a CLT residential structure. Analysis of tornado induced wind loading was performed using recommendations from the 2016 ASCE-7 commentary and applicable literature that attempts to account for the wind-induced pressures caused by tornadoes. Fragility analysis was performed to determine the probability of failure for a given estimated tornado wind-speed. When compared to the wind speeds of the Enhanced Fujita (EF) scale, the CLT residential archetypes showed wind speeds resulting in 10% probability of failure were in the range of EF-4 level events. Factors such as the connection spacing, and roof panel spans had the most significant effect on the simulated performance of the residential archetypes. Thicker panels, more robust connections, or tighter connection spacing could also lead to residential CLT structures that withstand EF-5 level events.
In this paper, we discuss the structural design of one of the tallest timber-based hybrid buildings in the world: the 18 storey, 53 meter tall student residence on the campus of the University of British Columbia in Vancouver. The building is of hybrid construction: 17 storeys of mass wood construction on top of one storey of concrete construction. Two concrete cores containing vertical circulation provide the required lateral resistance. The timber system is comprised of cross-laminated timber panels, which are point supported on glued-laminated timber columns and steel connections between levels. In addition to providing more than 400 beds for students, the building will serve as an academic site to monitor and study its structural performance, specifically horizontal building vibration and vertical shrinkage considerations. We present the challenges relating to the approval process of the building and discuss building code compliance issues.
Project contact is Arijit Sinha at Oregon State University
This project will undertake a comprehensive analysis of the effects of water exposure, in various forms, on mass timber building elements. Water intrusion is mostly commonly seen during construction, but can also occur during failure of roofs or external facades or as a result of internal plumbing failures. The research team will employ CAT-scan imaging, vibrational testing, non-destructive and small-scale physical tests to assess the effects of moisture intrusion and any subsequent biodegradation on the structural performance and aesthetic characteristics of the building elements and connections. This analysis will include investigating the effects of cracking and delamination that may occur as a result of wetting and drying. The project will facilitate development of guidelines on moisture control during construction, help identify suitable methods for protecting mass timber products where required and highlight design features that can be used to mitigate the risk of fungal and insect attack.