United States Department of Agriculture Fire Resistance of Forest Service Structural Composite Forest Products Laboratory Lumber Products Research Paper FPL–RP–633 Robert H. White Abstract Acknowledgments Use of structural composite lumber products is increasing. This study was suggested by Rodney McPhee of the Cana- In applications requiring a fire resistance rating, calcula- dian Wood Council (CWC). Funds for this study were pro- tion procedures are used to obtain the fire resistance rating vided by the CWC. The following manufacturers provided of exposed structural wood products. A critical factor in the structural composite lumber (SCL) test materials: Boise the calculation procedures is char rate for ASTM E 119 fire Cascade, Georgia–Pacific, Louisiana–Pacific, Trus Joist exposure. In this study, we tested 14 structural composite MacMillan (now Trus Joist, a Weyerhaeuser Business), and lumber products to determine char rate when subjected to Willamette Industries (now part of Weyerhaeuser Compa- the fire exposure of the standard fire resistance test. Char ny). Advice and suggestions were provided by the members rate tests on 10 of the composite lumber products were also of the CWC/FPL SCL Charring Rate Study task group of conducted in an intermediate-scale horizontal furnace. The the Wood I-Joist Manufacturers Association. This task group National Design Specification/Technical Report 10 design was chaired by Bruce Craig. Comazel Caldwell of the FPL procedure for calculating fire resistance ratings of exposed fire research work unit made the specimens and conducted wood members can be used to predict failure times for the tests. The author greatly appreciates the support, assis- members loaded in tension. Thirteen tests were conducted in tance, and patience from the parties involved. which composite lumber products were loaded in tension as they were subjected to the standard fire exposure of ASTM Contents E 119. Charring rates, observed failure times in tension tests, and deviations from predicted failure times of the Page structural composite lumber products were within expected Introduction ...........................................................................1 range of results for sawn lumber and glued laminated Background ...........................................................................1 timbers. Fire Resistance Calculations .............................................1 Keywords: structural composite lumber, LVL, fire resis- Char Rate of Wood ............................................................2 tance, char rate National Design Specification Technical Report 10 Procedure .........................................................3 Char Rate Experiments .........................................................3 Materials ...........................................................................3 Small Vertical-Furnace Tests.............................................4 Test method ...................................................................4 Test results .....................................................................5 Horizontal-Furnace Tests ................................................10 April 2006 Test methods ...............................................................10 White, Robert H. 2006. Fire resistance of structural composite lumber Test results ...................................................................12 products. Research Paper FPL-RP-633. Madison, WI: U.S. Department of Discussion .......................................................................13 Agriculture, Forest Service, Forest Products Laboratory. 28 p. A limited number of free copies of this publication are available to the Tension Tests .......................................................................15 public from the Forest Products Laboratory, One Gifford Pinchot Drive, Methods and Materials ....................................................18 Madison, WI 53726–2398. This publication is also available online at www.fpl.fs.fed.us. Laboratory publications are sent to hundreds of libraries Failure Times ..................................................................20 in the United States and elsewhere. National Design Specification Model Predictions ..........20 The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. Conclusions .........................................................................26 The use of trade or firm names in this publication is for reader information Literature Cited ..................................................................26 and does not imply endorsement by the United States Department of Agriculture (USDA) of any product or service. Appendix—Individual Test Results for Each Small The USDA prohibits discrimination in all its programs and activities on the Vertical-Furnace Test ..........................................................28 basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orienta- tion, genetic information, political beliefs, reprisal, or because all or a part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program informa- tion (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720–2600 (voice and TDD). To file a complaint of discrimi- nation, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250–9410, or call (800) 795–3272 (voice) or (202) 720–6382 (TDD). USDA is an equal opportunity provider and employer. Fire Resistance of Structural Composite Lumber Products Robert H. White, Research Wood Scientist Forest Products Laboratory, Madison, Wisconsin Introduction Production and use of structural composite lumber (SCL) products are increasing (McKeever 1997, Schuler and oth- ers 2001). Such products include laminated veneer lumber (LVL), parallel strand lumber (PSL), laminated strand lumber (LSL), and oriented strand lumber (OSL) (Green and Hernandez 1998, Moody and others 1999, ASTM Inter- national 2005) (Fig. 1). Introduction of composite lumber products started in the 1970s with LVL and continued with introduction of PSL in the 1980s and LSL in the 1990s (Yeh 2003). Oriented strand lumber is the latest of these products. For each of these products, adhesives are uti- lized to manufacture the composite product from veneers or strands of wood. Questions are sometimes raised about the performance of the adhesive when exposed to elevated temperature. The code and market acceptance of products depends on documentation of acceptable performance. Code acceptance of calculation procedures for determining Figure 1. Examples of types of composite lumber prod- fire resistance ratings of exposed wood beams and columns ucts tested in this study: (left to right) laminated veneer permitted their use in applications requiring structural mem- lumber, parallel strand lumber, and laminated strand bers to have specified fire resistance ratings. As a result, the lumber. potential market for such wood products increased. This re- port provides test data on the charring rate of three types of Background composite lumber products (LVL, LSL, and PSL) and their Fire Resistance Calculations performance when loaded in tension and subjected to the fire exposure specified in the standard fire resistance test. Fire resistance ratings of structural members are normally Several species of composite lumber products were included determined by conducting the full-scale test described in in testing. In the first two phases of this project, we docu- specifications of ASTM E 119 or similar standards. Calcu- mented charring rates of composite lumber products. Fire lation procedures for determining fire resistance rating of tests conducted in the first two phases of this project did not wood members have code acceptance (White 2002). Lie include any load being applied to the member. Results of (1977) developed the first procedure to gain code accep- Phase One were initially published in a conference proceed- tance in the United States and Canada for wood beams and ings article, “Charring Rate of Composite Timber Products” columns (American Institute of Timber Construction 1984, (White 2000). These one-dimensional charring experiments Canadian Wood Council 1997, American Forest & Paper were conducted in the small vertical-furnace at the USDA Association 2000, 2003). A more recent calculation proce- Forest Products Laboratory (FPL), Madison, Wisconsin. In dure, the National Design Specification (NDS) method, was the second phase, we measured temperatures in the interior developed by the American Wood Council (AWC) of the of a non-loaded beam subjected to the ASTM E 119 (ASTM American Forest & Paper Association. It was included in the International 2000) fire exposure in an intermediate-scale NDS (American Forest & Paper Association 2001) starting horizontal furnace. Charring rates determined in the two with the 2001 edition. This new, more explicit procedure is furnaces were compared. In the third and final phase of applicable to other structural members besides beams and the study, a series of SCL test specimens were subjected to columns. Per NDS, the fire design procedure is applicable to ASTM E 119 fire exposure while loaded in tension. all wood structural members and connections covered