This report contains test results for the fire-retardant-treatment (FRT) and hygrothermal effects on structural glued laminated timber (glulam). This is the second part of the collaborative research project between ABA - The Engineered Wood Association, Tacoma, WA, and USDA Forest Products Laboratory (FPL), Madison, WI. The first part of this project is related to FRT laminated veneer lumber (LVL) and the results are provided in a separate research report.
Selected mechanical properties, including tension, bending, and shear of the FRT glulam treated with the American Wood Protection ASsociation (AWPA) P49 and P50 fire retardants were evaluated in this study. These results are used to support the development of an ASTM standard for FRT glulam.
Solutions for Mid-Rise Wood Construction: Full-Scale Standard Fire Test for Exterior Wall Assembly Using a Simulated Cross-Laminated Timber Wall Assembly with Interior Fire-Retardant-Treated Plywood Sheathing
One of the tasks in the project, Wood and Wood-Hybrid Midrise Buildings, was to develop further information and data for use in developing generic exterior wall systems for use in mid-rise buildings using either lightweight wood frame or cross-laminated timber as the structural elements. This report describes a standard full-scale exterior wall fire test conducted on October 30, 2012 on a simulated cross-laminated timber (CLT) wall assembly with an attached insulated lightweight wood frame assembly protected using interior fire-retardant-treated (FRT) plywood sheathing. The test was conducted in accordance with CAN/ULC-S134 .
One of the tasks in the project, Wood and Wood-Hybrid Midrise Buildings, was to develop further information and data for use in developing generic exterior wall systems for use in mid-rise buildings using either lightweight wood frame or cross-laminated timber as the structural elements. This report describes a standard full-scale exterior wall fire test conducted on April 9, 2013 on an insulated lightweight wood frame wall assembly protected using interior fire-retardant-treated (FRT) plywood sheathing. The test was conducted in accordance with CAN/ULC-S134-13 .
For the past decade, mountain pine beetle infestation in British Columbia, Canada, has substantially changed wood characteristics of vast amounts of the lodgepole pine (Pinus contorta) resource. Resin impregnation is one method that could improve the properties of the beetle-affected wood. The key objective of this study was to examine the impact of resin impregnation on dynamic MOE of lodgepole pine veneers and properties of laminated veneer lumber (LVL) made with these treated veneers. A new phenol formaldehyde resin was formulated to treat these veneers using dipping and vacuum-pressure methods. Five-ply LVL billets were made with treated and untreated veneers. Their color, dimensional stability, surface hardness, flatwise bending modulus and strength, and shear strength were evaluated. Good correlation existed between veneer MOE enhancement and resin solids uptake. With the same treatment, stained veneers had higher resin retention and in turn greater MOE enhancement than nonstained (clear) veneers. A 5-min dipping was sufficient for veneers to achieve approximately 7 and 10% resin solids uptake and in turn 5 and 8% enhancement in veneer MOE for nonstained and stained veneers, respectively. LVL made with treated veneers had a harder surface with no discoloration concerns compared with the control. Also, evidence suggested that use of resin impregnation can improve dimensional stability, shear strength, and flatwise bending MOE of LVL.
One component PUR adhesive is widely used in engineered wood products applications, such as cross-laminated timber (CLT). However, the dramatic deterioration of PUR adhesive bond strength at elevated temperature can out tremendously threat for tall wood building, especially under fire. In this project, we are aiming to improving the bond strength of the PUR adhesive at high temperature by incorporating chemically modified halloysite to improve the poor interface between inorganic fillers and the polymer matrices. To improve the interaction with PUR (Loctite UR20 by Henkel®), the halloysite was chemically grafted with polymeric diphenylmethane diisocyanate (pMDI) (pMDI-H). The effect of adding pMDI modified halloysite to the PUR adhesives was investigated in terms of nanofiller dispersibility, thermal and mechanical properties of the pMDI-halloysite-PUR composite film, and the bonding shear strength of the glued Douglas fir and Spruce-Pine-Fir (SPF) shear blocks under different temperature.
Significant improvement of the bond shear strength can be observed with the addition of 5 and 10% of pMDI-modified PUR adhesive, and the key research findings are summarized as below,
a. pMDI can be successfully grafted onto hydroxylated halloysites to improve its dispersibility in one-component PUR adhesive;
b. Addition of pMDI-H into PUR adhesive can lead to improved glass transition temperature and storage modulus. In contrast, no significant enhancement was observed in h-H added PUR films due to the poor dispersibility;
c. Addition of up to 10% h-H and pMDI-H did not show significant change of the shear strength at 20 °C for both Douglas Fir and SPF;
d. Significant enhancement of shear strength at elevated temperature (60-100 °C) can be observed for 5% and 10% pMDI-H modified PUR adhesive, showing 17% improvement for Douglas Fir and 27-37% for SPF.
Effective preservative treatments for Canadian glulam products are needed to maintain markets for mass timber on building facades, access markets with significant termite hazards, and expand markets for wood bridges. For all three applications, borate-treatment of lamina before gluing would be preferred as it would lead to maximum preservative penetration. However, the need to plane after treatment and prior to gluing removes the best-treated part of the wood, and creates a disposal issue for treated planer shavings. The present research evaluates the block shear resistance of glulam prepared from untreated and borate-treated lamina with a polyurethane adhesive. Borate treatment was associated with a small but statistically significant loss in median shear strength when evaluated dry; however, there was no difference between the performance of untreated and borate-treated samples when exposed to the vacuum-pressure soak/dry or the boil-dry-freeze/dry procedures. Further work is needed to modify the composition or application of the resin to improve shear strength for glulam applications and ensure consistent performance. However, overall, these data indicate that samples prepared from borate-treated lamina perform similarly in terms of block shear resistance to those prepared from untreated lamina.
This research investigates the fire behaviour of laminated veneer lumber elements
and cross-laminated timber panels. The study focused on some research questions
regarding the fire resistance of unprotected and protected timber structural elements,
the possibility to predict accurately the fire behaviour of timber elements through numerical modelling, and the accuracy of analytical estimations of fire resistance using simplified design methods. Experimental tests of small and large specimens exposed to fire on one or more sides and subjected to different types and levels of load were performed. The results highlight the good performance of timber structural elements in fire conditions. The collected data were used to validate two- and three-dimensional models implemented in the general purpose finite element code Abaqus. Thermal and mechanical analyses were carried out to estimate the temperature distribution within unprotected and protected cross-sections
of different sizes, the fire resistance and the displacement of timber elements loaded inplane and out-of-plane