Expanding Mass Timber & CLT Markets for High Termite Risk Applications


Project Leads: Gerald Presley, OSU College of Forestry, Scott Noble, Kaiser+Path

The primary goal of this project is to enhance the durability of mass timber assemblies in high-moisture, high-termite risk regions. Only a few U.S. jurisdictions allow mass timber use by code adoption. Hawaii requires that all structural wood be treated to resist insects. Current topical or pressure treatments are allowed, but it is unclear how these treatments will perform in mass timber elements. Assembled cross-laminated timber (CLT) panels are too large to fit in pressure vessels. We will test the performance of individually treated wood members (lamella), assembled into CLT panels for compliance to structural requirements as well as resistance to termite attack in field trials. The resulting data will identify the most effective treatment options to protect CLT and other mass timber assemblies for use in Hawaii and similar regions with high termite exposure. The research implications will contribute to educating architects, engineers, builders and developers on modern timber construction in new regions.

Impact of Moisture on the Cyclic Performance of a Two-Story Post-Tensioned CLT Rocking Wall with External Hysteretic Energy Dissipators

2018 - 2020
Project Lead: André Barbosa
Abstract: 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.

Design, Construction, and Maintenance of Mass Timber Post-Tensioned Shear Walls

2019 - 2021
Project Lead: Mariapaola Riggio
Abstract: Earthquake engineers are focusing on performance-based design solutions that minimize damage, downtime, and dollars spent on repairs by designing buildings that have no residual drift or “leaning” after an event. The development of timber post-tensioned (PT), self-centering rocking shear walls addresses this high-performance demand. The system works by inserting unbonded steel rods or tendons into timber elements that are prestressed to provide a compressive force on the timber, which will pull the structure back into place after a strong horizontal action. But, because these systems are less than fifteen years old with just four real-world applications, little information is known regarding best practices and optimal methods for engineering design, construction and/or tensioning procedures, and long-term maintenance considerations. This project intends to contribute knowledge by testing both cross-laminated timber (CLT) and mass plywood panel (MPP) walls through testing of anchorage detailing, investigating tensioning procedures for construction, determining the contributions of creep on prestress loss over time, and comparing all laboratory test data to monitoring data from three of the four buildings in which this technology has been implemented, one of which is George W. Peavy Hall at Oregon State University. This will be accomplished by testing small- and full-scale specimens in the A.A. “Red” Emmerson Advanced Wood Products Laboratory, and small-scale specimens in an environmental chamber.

Development of Isocyanate-Free and Formaldehyde-Free Adhesives for CLT

2018 - 2020
Project Lead: Kaichang Li
Abstract: 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 have successfully 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.

Durability and Protection of CLT in Parking Structures

2018 - 2020
Technical Advisor: Lech Muszynski
Abstract: 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. 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.

Water and Mass Timber

2018 - 2022
Project Lead: Arijit Sinha
Abstract: 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.