Test results for three representative adhesives were obtained for use in the development of a proposed standard for limited moisture exposure (CSA O112.10). The adhesives tested were an emulsion polymer isocyanate (EPI), a polyurethane (PUR) and a melamine-urea formaldehyde with 40% melamine resin content (MUF40). Currently, EPI and PUR are used for I-joists and fingerjoined lumber. MUF40 was included in the study as a non-conforming adhesive. The range of performance of these adhesives, along with that of melamine formaldehyde (MF) and polyvinyl acetate (PVA) evaluated in a previous study, is baseline information used in defining acceptable performance levels for adhesives undergoing block shear tests required in the proposed standard.
Specimens in this study were evaluated under five test conditions: dry, vacuum-pressure wet or re-dried, and three-cycle boil-dry-freeze wet or re-dried. Dry and re-dried test conditions are the proposed test protocols for the draft CSA O112.10 standard.
In terms of shear strength and percentage of wood failure, EPI and MUF40 met the requirements of CSA O112.9 for the dry test condition, and PUR did not.
The following block shear test requirements are recommended for CSA O112.10, based on the 95% lower confidence limit of the EPI test results, and structured to be analogous to the requirements of CSA O112.9:
Median dry shear strength = 10 MPa (1450 psi) (adopted from CSA O112.9);
Vacuum-pressure re-dried median shear strength = 7.4 MPa (1070 psi);
Median percentage wood failure = 85% for all the proposed tests (adopted from CSA O112.9); and
Lower quartile percentage wood failure = 75% for all the proposed tests (adopted from CSA O112.9).
The above requirements will be discussed in the CSA Task Group, which will eventually make recommendations to the CSA Standards Committee.
Fibre-reinforced wood systems are light, strong, stiff composites that can efficiently replace larger wood members and can be relied on to provide consistent mechanical properties.
This report is an introduction to fibre-reinforced wood systems for members of the Canadian wood products industry. It provides the motivation for reinforcing wood with synthetic fibres, and surveys the choice of materials and their uses. Numerous examples of current applications are discussed to demonstrate the strong and weak points of various approaches and examine the durability and management of fibre-reinforced wood products, as well as to indicate opportunities that exist for the Canadian wood products industry.
This report is intended to be a useful reference for the Canadian wood products industry, and assist future developments in structural and non-structural applications of fibre-reinforced wood products.
In recent years, significant attention has been paid to the engineering performance of wood structural systems, and a new generation of more reliable engineered wood components for building construction has evolved.
The latest trend is towards advanced products that combine wood and synthetics. This increases performance and structural reliability of engineered wood products, and leads to new markets and expanded opportunities. It is anticipated that cost of fibre reinforcement decreases over time and advances developed on reinforcing techniques and methods of evaluation would provide wood producers with more options to better position their products in the marketplace.
A new reinforcing technique has been developed and applied to manufacture a hybrid wood product for structural applications. The technique involves a layering analogy using layers of synthetic reinforcement sandwiched between layers of wood composite. The products manufactured in the laboratory used regular OSB laminations and alternating layers of E-glass fabrics and resin. Three- and four-ply billets were manufactured with various layouts and then tests were conducted to characterize mechanical properties of the hybrid products. Overall, the test specimens performed well relative to the controls. Shear failures were observed as a result of the limited performance of OSB in shear, and consequently the next tests will be conducted with plywood laminations instead of OSB.
Selected issues related to code acceptance of structural FRP-reinforced wood products are discussed in the appendix. Future work is suggested to completely characterize and understand the properties and behaviour of the FRP-reinforced wood products, including fire performance, long term durability, maintenance and cost, in order to establish an environment in which to work comfortably with such materials. Overcoming these issues is vital for product acceptance in building codes.
This report describes work to provide research information suitable for implementing design procedures for diaphragms with thick sheathing in the Canadian Standard for Engineering Design in Wood (CAN/CSA O86.1) and to make the information available to other markets by publishing the results and recommended procedures in a journal article.
With recent pressures to extract more value from the Alberta wood resource, efforts are being made to find higher value products that can be marketed along with SPF lumber traditionally used in the construction industry. Products such as reinforced glulam, edge glued and face glued lumber, or overlaid laminated veneer lumber provide additional opportunities for the medium-size Alberta lumber producers who are challenged by fierce competition in a commodity-focused market.
Given the steady increase in the utilization of glued products in structural applications, there is a strong potential for further expansion of these markets. A recently developed standard that allows products to be manufactured from face- and edge-gluing of components paves the way for the development of a wide range of products specifically designed for the construction market.
A situational analysis of the current state of the Alberta forest industry is presented here. It includes resources, markets, codes and standards, technical and market challenges, and prospects for developing higher value structural wood products by gluing wood together or reinforcing wood with other materials.
AFRI-817G-06, 5063 pertaining to Composite products - Markets; Alberta - Economic conditions
The objectives of this project are to provide research information suitable for implementing design procedures for diaphragms with thick sheathing in the Canadian Standard for Engineering Design in Wood (CAN/CSA O86.1) and to make the information available to other markets by publishing the results and recommended procedures in a journal article.
Forintek has completed a two-year investigation of the NLGA SPS 6 Standard, Special Products Standard for Structural Face-Glued Lumber. The NLGA SPS 6 Standard prescribes product specifications and qualification and quality control requirements for structural products created by edge-gluing and/or fingerjoining lumber segments. Under the NLGA SPS 6 Standard, the design values assigned are based on the visual grade and the stress level achieved in qualification tests on the glue joints.
The project assessed the effect of the following three factors on strength of the NLGA SPS 6 product:
1. Tension proof-loading;
2. Relative location of fingerjoints in adjacent members when fingerjoined material is edge-glued;
3. Strength of the material used to make the NLGA SPS 6 product.
Results showed a positive effect of proof-loading, a minor effect of staggering of fingerjoints, and a highly significant effect of density of raw material on tensile stress of edge-glued specimens. It was confirmed that SPS6 products of greater commercial value can be obtained from lower grade lumber. However, visual grading of SPS 6 products proved to be more difficult than visual grading of lumber, because grade-determining wood characteristics were sometimes hidden in the bond line, and could not be properly identified.
The findings of this project can be used to fine tune the NLGA SPS 6 standard and the other NLGA fingerjoint and face-glued lumber product standards. The project will help the wood industry maximize the utilization of their raw material resource, resulting in increased profitability.
Wood design standards in Canada and the United States provide design values for floor and roof diaphragms with sheathing thickness ranging from 9.5 mm (3/8 in) up to 18.5 mm (3/4 in), that are supported by joists spaced less than 610 mm (24 in) on centre. This range of sheathing thicknesses is adequate for housing and small buildings, but for large non-residential structures, diaphragms with thicker sheathing and wider joist spacing may be more appropriate.
This paper includes the findings of a study aimed at providing research information suitable for implementing design values for diaphragms with thick sheathing in the North American wood design standards. Results from quasi-static monotonic tests on fifteen full-scale 7.3 m (24 ft) long by 2.4 m (8 ft) wide diaphragms framed with 38x191 mm or 38x235 mm (nominal 2x8 and 2x10, respectively) solid sawn lumber or laminated strand lumber and sheathed with plywood or oriented strand board are discussed.
A numerical model was developed using the finite element method. The basic properties of the sheathing, framing members and nailed connections were implemented in the model to replicate the structural behaviour of the diaphragms with thick panels. The numerical model was successfully validated against the experimental data. The shear resistance values for the diaphragms with thick panels tested in this study were calculated. The model may be used to interpolate between various diaphragm configurations and calculate shear resistance values for other configurations of diaphragms with thick sheathing.
In the long run, it is hoped that the use of thicker sheathing will enable the use of structural systems that are cost effective for wider joist or beam spacing than systems made with dimension lumber and traditional sheathing thickness. The experimental data and the model developed in this project will be used to develop proposals for implementation of wood floor and roof diaphragms with thick panels in the Canadian and United States wood design standards.
The objective of the project is to develop/improve practical, reliable and internationally recognized methods for assessing/pre-screening the long-term structural performance of engineered wood products used in residential and non-residential applications.
Tension proof loading has been shown to be effective in eliminating low-strength fingerjoints, and a proof load stress level of 1.3 times the allowable stress value was found to be optimum. This confirms the tension proof loading stress requirement of the Canadian National Lumber Grades Authority (NLGA) for fingerjoined lumber.
Proof loading stress levels were chosen at 1.0, 1.3 and 1.6 times the allowable stress, and loading rates were selected so that target stress was attained in 0.2, 6.0 or 60 seconds. The only effect of loading rate was a small increase in strength values for weaker specimens when tested at faster loading rates, along with increased variability; therefore, it is strongly recommended that very fast loading rates be avoided, and a loading rate be chosen so the desired stress level is attained in about one second.
FPInnovations – Forintek performed this two-year study to provide a sound basis for evaluation of the tension proof-loading of fingerjoined lumber. The findings will be useful to the fingerjoined-lumber industry in refining the process and promoting its benefits to end users and regulators.
