Since 2016 the TallWood Design Institute has funded eighteen research projects to enhance understanding of wood in the built environment. We do this through a competitive call for proposals process involving an invited team of reviewers that has included architects, structural engineers, wood products manufacturers, developers, building code officials, economists, environmental specialists and research scientists. Projects are selected based on their ability to deliver actionable results to industry to address current challenges and potential opportunities in the wood construction sector.
Our latest call, held in October 2017, included special emphasis on three areas: (1) durability of mass timber with regard to moisture; (2) technical innovations for mass timber production that address environmental concerns (adhesives, eco-friendly wood protection measures, etc.), and; (3) development of modular “kit of parts” solutions utilizing mass timber and other components for applications such as rapid deployment disaster-relief/military structures, and affordable housing. Our strategic research priorities are revisited each year to reflect changes in technologies, products, market conditions and other factors.
The projects listed below are broken into six categories: (1) Fire Performance of Mass Timber; (2) Seismic and Structural Performance; (3) Building Physics and Health; (3) Environment; (4) Business and Economics; (5) Durability and Adhesives.
Fire Performance of Mass Timber
Fire Resistance of Unprotected CLT Floors & Walls Manufactured in the U.S.
Project Lead: Lech Muszynski
Despite a growing body of empirical evidence generated by European, Japanese and Canadian research on the fire endurance of cross-laminated timber (CLT), a lack of full-scale U.S. testing of structural CLT manufactured within the U.S. is often cited as a major barrier to approval of the new building material for use in tall structures. Past testing in test furnaces suggests that CLT and glue-laminated timber can outperform both light-frame timber assemblies and steel and concrete elements. This is due, in part, to the fact that in thick CLT panels a layer of charred wood forms on the exposed surface that then serves to insulate and protect the wood behind the char layer.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. When this research project was proposed in 2015,no full-scale fire performance testing of U.S.-made, structural CLT had been performed. Watch the video
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Mitigating Fire Performance Concern through Fire Endurance Modeling
Project Lead: Arijit Sinha
The Mitigating Fire Concerns project is in collaboration with the Forest Products Laboratory in Madison, Wisconsin, which has a chamber to test elevated temperatures up to 330 degrees Celsius. In the lab, the project will take the connection systems from the Composite CLT-Concrete Floor Systems for Tall Building Design project and test them over elevated temperatures to evaluate strength properties as well as how the stiffness and strength degrade at different levels of elevated temperatures.
This information will be implemented into fire models and will help to predict things like failure time.
Fire Penetration Testing
Technical Advisors: David Barber, Lech Muszynski
In the U.S., there is limited published information about the performance of through-penetration fire seals in cross-laminated timber floors, where the CLT is unprotected, and exposed to the fire side. TDI has partnered with ARUP and the Framework project, a 12-story mass timber building project in Portland, to investigate and test through-penetrations to the ASTM E814 standard.Penetration seals were designed for five different types of penetrations–three-inch OD PVCpipe, four-inch OD stainless steel pipe, four-inch OD cast iron pipe, two-inch OD aquatherm (PP-R), and a one-and-three-fourths-inch threaded steel rod. The penetration seals were installed in five-ply CLT samples produced in the Pacific Northwest.Initial fire tests were conducted at the Western Fire Center in Kelso, Washington in September 2017 using 3M penetration seals and Hilti penetration seals. Results were promising. The remaining testing will be conducted by Hilti in partnership with TDI during the second quarter of 2018.
Concrete Composite Floors Using Radiant Panel Tests
Project Lead: Erica Fischer
In many mass timber buildings, CLT or nail laminated timber (NLT) floors are designed with a concrete topping to improve acoustic separation, reduce vibration or act as a fire barrier. Little research has examined the fire behavior of these floor systems, but some preliminary tests involving LVL show that they may be able to meet three-hour fire resistance ratings, which could potentially open up the use of mass timber in Type I buildings, representing a large market opportunity.This project will test the behavior of composite floors under fire loading conditions considering the following parameters: shear connector type, mass timber panel types and thicknesses and concrete thicknesses. It will also test and validate an innovative fire research methodology using radiant panels.
Seismic and Structural Performance
Structural Health Monitoring and Post-Occupancy Performance of Mass Timber Buildings
Project Lead: Mariapaola Riggio
A key question about new generation taller wood buildings is how they will perform over time in terms of durability and livability. This project will determine how best to measure these qualities by selecting sensors, determining testing and measurement protocols, and implementing testing assemblies in selected CLT buildings in Oregon. Future research will use the knowledge developed through this project to carry out post-occupancy monitoring, generating valuable new insights into building performance.
Living Lab at Peavy Hall: Structural Health Performance of Mass Timber Buildings
Project Lead: Mariapaola Riggio
Building on the results of an earlier project that established protocols for post-occupancy building monitoring, this project aims to install a system in the new Peavy Hall building at Oregon State University to monitor moisture, relative humidity, vertical and slip movements due to shrinkage & deflection, post-tensioning losses, vibration and seismic activity. The monitoring system will establish a “living” laboratory that demonstrates in real time how the mass timber components of the building are affected by various internal and external phenomena. The data will be gathered and analyzed over the service life of the building. Watch the video.
Design of the Timber Pile Ground Improvement for Liquefaction Mitigations
Project Lead: Armin Stuedlein
Liquefaction caused damage to 25,000 homes in the 2011 Tohoku earthquake in Japan and $15 billion in losses in Christchurch in 2010-11. This project creates design guidelines for the use of timber piles driven into the ground as a way to protect building foundations from soil liquefaction in seismic events. This approach has application in protecting a broad range of other structures, including port and harbor facilities, bridge approach embankments and foundations.
Seismic Performance of Cross-Laminated Timber and Cross-Laminated Timber-Concrete Composite Floor Diaphragms
Project Lead: Andre Barbosa
This project develops benchmark data needed to generate design guidelines for structural engineers to calculate strength & stiffness of CLT-diaphragms, with and without concrete toppings. The project includes a full-scale test of a two-story mass timber building at the UC San Diego shake table in collaboration with the larger project, “Development and Validation of a Resilience-based Seismic Design Methodology for Tall Wood Buildings” which features collaborators from throughout the western US and is funded by the Natural Hazards Engineering Research Infrastructure (NHERI) program of the National Science Foundation.
Mass Plywood Panel Product Development Testing
Project Lead: Arijit Sinha
In August 2017 the TallWood Design Institute began phase two of testing an innovative engineered wood product- the mass plywood panel (MPP)-for Freres Lumber Company in Lyons, Oregon. The concept for the new product was developed during a 2015 technical tour to mass timber facilities in Austria, led by the OSU College of Forestry.A first round of testing in 2016 focused on helping Freres Lumber Company identify the most appropriate lay-up pattern, and Sinha and his team then tested an optimized layup at different thicknesses that would eventually be taken to market. Phase two includes bending tests to investigate the strength and stiffness of the product. Later, connections, acoustic performance characteristics and a rocking shear wall application of the product will also be tested. MPP, like CLT, can be used as a substitute for traditional building materials, providing much lower embodied energy and greater carbon sequestering properties than concrete and steel. Freres says that some advantages of MPP are that it uses 20-30 percent less wood than CLT. Large-format panels can be manufactured at the production facility in order to minimize waste and labor on job sites. The light weight of the panels can help save on transportation costs and logistics during construction
Composite Concrete-CLT Floor Systems for Tall Building Design
Project Lead: Christopher Higgins
This project will optimize the strength, stiffness, vibration characteristics, acoustic qualities and fire resistance of cross-laminated floor systems utilizing a composite concrete and cross-laminated timber product. This project includes development, testing and optimization of an economical shear connector (to connect the CLT panel to the concrete slab) that will be compared with existing screw and steel plate solutions. The resulting prototype floor system will be tested at full scale.
Behavior of CLT Diaphragm Panel-to-Panel Connections with Self-tapping Screws
Project Lead: Thomas Miller
Understanding how roof and floor systems (commonly called diaphragms by engineers) that are built from Pacific Northwest-sourced cross-laminated timber (CLT) panels perform in earthquake prone areas is a critical area of research. These building components are key to transferring normal and extreme event forces into walls and down to the foundation. The tests performed in this project will provide data on commonly used approaches to connecting CLT panels within a floor or roof space and the performance of associated screw fasteners. Structural engineers will directly benefit through improved modeling tools. A broader benefit may be increased confidence in the construction of taller wood buildings in communities at greater risk for earthquakes.
Cross-Laminated Timber Fasteners Solutions for Tall Wood Buildings
Project Lead: Arijit Sinha
Constructing buildings with CLT requires development of novel panel attachment methods and mechanisms. Architects and engineers need to know the engineering strength properties of connected panels, especially in an earthquake prone area. This project will improve knowledge of three types of wall apnel connections: wall-to-floor, wall-to-wall, and wall-to-foundation. Testing will determine the strength properties of metal connectors applied with diffferent types and sizes of screw fasteners. The data will be used to develop a modeling tool that engineers can use when designing multi-story buildings to be constructed with CLT panels.
Building Physics and Health
Net-Zero Energy TallWood Design
Project Lead: Kevin Van Den Wymelenberg
This project aims to solve one of the biggest barriers to increased market adoption of mass-timber buildings - energy consumption. The project team will explore how to replace the concrete typically needed for night flush cooling of thermal mass. The goal is to provide results that will help mass-timber buildings achieve net-zero energy priorities for a larger range of use types and climate zones while also providing new insight into human perception of thermal comfort in mass-timber buildings.
Tall Wood Buildings and Indoor Air Quality
Project Lead: Kevin Van Den Wymelenberg
New research is showing that wood buildings are more likely to harbor environmental microbes with beneficial health effects. This pilot project will study various surface materials in both the lab setting and occupied mass timber buildings to assess effects on occupants’ health and comfort as well as indoor air quality.
Life Cycle Analysis of Old- and New Peavy Hall
Project Lead: Paul Frederik Laleicke
This project assesses and compares the environmental impacts of forest products used in the old (1999) Peavy Hall teaching building at Oregon State University and the new mass timber building that will be completed in 2018. The findings will be incorporated in updated guidelines for life cycle analyses that fully take into account the role of reclaimable wood building products.
Carbon Impacts of CLT
Project Lead: Alison Kwok
CLT offers the potential to reduce greenhouse gas emissions by using timber, which requires much less energy to produce than steel or concrete and naturally sequesters carbon through its lifetime. However, there is a gap in the literature and a lack of general understanding about how much carbon CLT sequesters compared to the carbon emitted in the manufacturing process and in creating the adhesives used, as well as how the carbon value is calculated. This project will analyze and summarize relevant literature and will create six case studies to illustrate the embodied carbon impacts of various kinds of mass timber buildings. In doing so, it will reduce confusion in the sector and assist designers and developers in making informed decisions regarding future green buildings.
Environmental Assessment of MPP
Project Lead: Arijit Sinha
Mass timber products are often selected for their perceived sustainability advantages, and a lifecycle analysis for an Oregon-based CLT manufacturing facility is being completed. This project will assess the environmental impacts of mass plywood panel manufacturing, a new product that has become available commercially in Oregon in 2018. It will examine material flow, energy type and use, emissions to air and water, solid waste production and water impacts for the MPP manufacturing process on a per unit volume basis using a cradle-to-gate lifecycle assessment process.
The data will be available for stakeholders to use for informational and learning purposes and to assist in determining the sustainability of mass timber building projects.
Business and Economics
The Pulse of the Global CLT Industry: Launching an Annual Survey as a Continuing Learning Tool
Project Lead: Chris Knowles
This project explores the emerging cross-laminated timber industry in other countries to learn the key success factors, challenges, business models and level of government support other countries receive in order to better implement the use of CLT in the U.S. The outcomes will include a database, annual reports on the CLT industry and specific guidelines for facilitating sustainable growth in the modern U.S. forest products industry.
Establishing New Markets for CLT-Lessons Learned
Project Lead: Eric Hansen
This project explored lessons learned from the original cross-laminated timber market in Europe, as well as interest in and use of CLT in North America so far. CLT was developed more than 20 years ago in Austria, and spread thereafter to Germany, Switzerland and northern Italy. The North American market is still young and can tend to ignore European knowledge of the product. Research was conducted through personal interviews with professionals in thearchitecture and construction industries in Europe and North America. The study found that, while much in-depth knowledge exists in the original market, this is largely ignored in North America. Despite many challenges–including a current lack of relevanteducation and training and inflexible planning processes–the potential for CLT in North America is large and growing. Standards development and building code acceptance will be critical to market development.
Cost Comparisons of Mass Timber versus Conventional Construction
Project Lead: Ingrid Arocho
Perhaps the first question that developers and designers ask about mass timber construction is “How much does it cost compared to the way I currently build?” Inresponse, TDI has embarked upon a research project that will study mass timber building
projects around North America and examine in detail the factors responsible for differences in cost. Once all of the data has been collected and analyzed, the team will formulate a set of guidelines and recommendations to help designers maximize the cost efficiency of these types of buildings.
Durability and Adhesives
Durability and Protection of CLT in Parking Structures
Technical Advisor: Lech Muszynski
The City of Springfield, Oregon hired SRG Partnership to design a CLT parking structure slated to be built in a new redevelopment zone on the Willamette River. The concept started as an academic exercise in a University of Oregon architectural design studio course led by Professor Judith Sheine. Mayor Christine Lundberg saw an opportunity to connect Springfield’s historic roots in the timber industry to the burgeoning new mass timber sector, and the project became a reality. Before the structure is built, important technical questions must be addressed concerning how to protect the timber elements against the Pacific Northwest weather and long-term dynamic loading from vehicles. A technical team from OSU’s Department of Wood Science and Engineering and School of Civil and Construction Engineering are narrowing down combinations of materials for testing. Proposed solutions include an asphalt topping on the CLT decking, similar to those often used on timber bridge decks.
Stress tests will be conducted, simulating forces from vehicles turning, starting and stopping and backing up. Simulated weather testing will also be conducted in OSU’s multi-chambermodular environmental conditioning chamber. The Energy Studies in Buildings Laboratory at University of Oregon has conducted wind-driven rain studies to inform SRG’s design of the roof and exterior screening elements.
Development of Isocyanate-Free and Formaldehyde-Free Adhesives for CLT
Project Lead: Kaichang Li
This project aims to develop a commercially-viable wood adhesive for CLT that is free of formaldehyde and isocyanates and possesses good cure speed properties. Li and his team havesuccessfully developed adhesives for plywood manufacturing
using abundant, inexpensive and renewable soy flour. This adhesive mimics the superior bonding properties of mussel additive proteins. Emission of hazardous air pollutants from plywood plants that use this adhesive has dropped 50-90 percent. Development of such an adhesive for CLT would address increasingly stringent air quality regulations in many places such as Oregon and California. The existing chemical formulation for the plywood adhesive will be adapted for use in a cold-pressing process. Specimens will be created at the OSU wood composites labs and first tested to verify conformance with the PRG320 product standard for CLT. Specimens passing the tests will be sent to the Energy Studies in Buildings Laboratory at the University of Oregon, Portland, where they will be conditioned and tested to determine emission characteristics.
Water in Mass Timber
Project Lead: Arijit Sinha
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.
Impact of Moisture on Post-tensioned Rocking Walls
Project Lead: André Barbosa
Resilient structures are buildings designed not only to protect life safety in a seismic event but also to preserve the structural integrity of the major components of the buildings so that they can be reoccupied quickly and at minimal cost. An example is a CLT rocking wall system, utilizing post-tensioned cables and energy dissipating-connectors, which is being used for the first time in North America in OSU’s new Peavy Hall. CLT rocking walls borrow from concepts used in concrete and steel structures that were later adapted to LVL building systems in New Zealand. This project will examine the impacts of wetting at the base of the wall on the structural capacity and cyclic performance of the system. Identical rocking wall systems will undergo structural testing, with one being subjected to simulated moisture intrusion that may occur during construction. The findings will provide important information that can be later implemented in design and construction guidelines.