Apa D510 Panel Design Specification; 2008

Transcript

Panel Design Specification Engineered wood products are a good choice for the environment. They are manufactured for years of trouble-free, dependable use. They help reduce waste by decreasing disposal costs and product damage. Wood is a renewable, recyclable, biodegradable resource that is easily manufactured into a variety of viable products. A few facts about wood. ■ We’re growing more wood every day. Forests fully cover one-third of the United States’ and one-half of Canada’s land mass. American landowners plant more than two billion trees every year. In addition, millions of trees seed naturally. The forest products industry, which comprises about 15 percent of forestland ownership, is responsible for 41 percent of replanted forest acreage. That works out to more than one billion trees a year, or about three million trees planted every day. This high rate of replanting accounts for the fact that each year, 27 percent more timber is grown than is harvested. Canada’s replanting record shows a fourfold increase in the number of trees planted between 1975 and 1990. ■ Life Cycle Assessment shows wood is the greenest building product. A 2004 Consortium for Research on Renewable Industrial Materials (CORRIM) study gave scientific validation to the strength of wood as a green building product. In examining building products’ life cycles – from extraction of the raw material to demolition of the building at the end of its long lifespan – CORRIM found that wood was better for the environment than steel or concrete in terms of embodied energy, global warming potential, air emissions, water emissions and solid waste production. For the complete details of the report, visit www.CORRIM.org. ■ Manufacturing wood is energy efficient. Wood products made up 47 percent of all industrial raw materials manufactured in the United States, yet consumed only 4 percent of the energy needed to manufacture all industrial raw materials, according to a 1987 study. ■ Good news for a healthy planet. For every ton of wood grown, a young forest produces 1.07 tons of oxygen and absorbs 1.47 tons of carbon dioxide. Wood: It’s the natural choice for the environment, for design and for strong, lasting construction. WOOD The Natural Choice Percent of Percent of Material Production Energy Use Wood 47 4 Steel 23 48 Aluminum 2 8 NOTICE: The recommendations in this panel design specification apply only to products that bear the APA trademark. Only products bearing the APA trademark are subject to the Association’s quality auditing program. RATED SHEATHING EXPOSURE 1 SIZED FOR SPACING 32/16 15/32 INCH 000 PS 1-07 C-D PRP-108 © 2 0 0 8 A P A – T H E E N G I N E E R E D W O O D A S S O C I A T I O N • A L L R I G H T S R E S E R V E D . • A N Y C O P Y I N G , M O D I F I C A T I O N , D I S T R I B U T I O N O R O T H E R U S E O F T H I S P U B L I C A T I O N O T H E R T H A N A S E X P R E S S L Y A U T H O R I Z E D B Y A P A I S P R O H I B I T E D B Y T H E U . S . C O P Y R I G H T L A W S . CONTENTS Designer Flowchar t . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . 5 1.1. Plywood . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Oriented strand board . . . . . . . . . . . 5 1.3. Composite panels . . . . . . . . . . . . . . 6 2. Sel ecting panel s . . . . . . . . . . . . . . . 6 2.1. Standards. . . . . . . . . . . . . . . . . . . . . 6 2.1.1. Voluntary Product Standard PS 1 . . . . . . . . . . . . . . . . . . . 6 2.1.2. Voluntary Product Standard PS 2 . . . . . . . . . . . . . . . . . . . 7 2.1.3. Proprietary standards . . . . . . . . . 7 2.2. Veneer . . . . . . . . . . . . . . . . . . . . . . . 7 2.2.1. Species groups . . . . . . . . . . . . . . 7 2.2.2. Grades . . . . . . . . . . . . . . . . . . . 8 2.3. Panel grades . . . . . . . . . . . . . . . . . . 8 2.3.1. Unsanded . . . . . . . . . . . . . . . . . 8 2.3.2. Touch sanded . . . . . . . . . . . . . . 8 2.3.3. Sanded . . . . . . . . . . . . . . . . . . . 8 2.3.4. Overlaid . . . . . . . . . . . . . . . . . 10 2.4. Bond classifications . . . . . . . . . . . . 10 2.4.1. Exterior. . . . . . . . . . . . . . . . . . . 10 2.4.2. Exposure 1 . . . . . . . . . . . . . . . . 10 2.4.3. Other classifications . . . . . . . . . 10 2.5. Span ratings . . . . . . . . . . . . . . . . . 10 2.5.1. Sheathing . . . . . . . . . . . . . . . . . 10 2.5.2. Single floor . . . . . . . . . . . . . . . 11 3. Code provisions . . . . . . . . . . . . . . 11 4. Mechanical proper ties . . . . . . . . . 11 4.1. Strength axis . . . . . . . . . . . . . . . . . 11 4.2. Panel construction . . . . . . . . . . . . . 11 4.3. Properties and stresses . . . . . . . . . 13 4.4. Capacities . . . . . . . . . . . . . . . . . . . 13 4.4.1. Panel flexure (flat panel bending) . . . . . . . . . . . . . . 14 4.4.2. Panel axial strength . . . . . . . . . 14 4.4.3. Panel axial stiffness (EA) . . . . . . 14 4.4.4. Shear in the plane of the panel (F s [lb/Q]) . . . . . . . . . . . . . . . . . 14 4.4.5. Panel shear through the thickness . . . . . . . . . . . . . . . . . . . . . . 14 4.4.6. Panel allowable bearing stress (F c⊥ ) . . . . . . . . . . . . . . . . . . . . . 15 4.4.7. Dowel bearing strength . . . . . . 16 4.5. Adjustments . . . . . . . . . . . . . . . . . . 16 4.5.1. Duration of load (DOL) . . . . . . 16 4.5.2. Service moisture conditions . . . 16 4.5.3. Elevated temperatures . . . . . . . 21 4.5.4. Pressure treatment . . . . . . . . . . 21 4.5.5. Panel size . . . . . . . . . . . . . . . . . 22 4.6. Section properties . . . . . . . . . . . . . 22 4.7. Uniform load computations . . . . . . 24 4.7.1. Uniform loads based on bending strength . . . . . . . . . . . . . . . . 24 4.7.2. Uniform loads based on shear strength . . . . . . . . . . . . . . . . . . 24 4.7.3. Uniform loads based on deflection requirements . . . . . . . . . . . 24 4.7.4. Uniform load . . . . . . . . . . . . . . 25 4.8. Design examples showing use of capacity tables . . . . . . . . . . . . . . . . . 25 4.8.1. Example 1 – Conventional roof . 25 4.8.2. Example 2 – Panelized roof . . . 25 4.8.3. Example 3 – Floor . . . . . . . . . . 26 5. References . . . . . . . . . . . . . . . . . . . 27 his Specification presents recommended design capacities and design methods for wood structural panels when used in build- ing construction and related structures. Design information on other wood structural panel applications such as concrete forming, trench shor- ing, pallets, bins, tanks, shelving and agricultural structures can be found in other APA publications. The information stems from extensive and continu- ing test programs conducted by APA – The Engineered Wood Association, by other wood associations, and by the United States Forest Products Laboratory, and is supported by years of satisfactory experience. Information in this Specification applies to untreated (except as noted) wood structural panels made in accordance with Voluntary Product Standard PS 1-07 or PS 2-92, promulgated by the United States Department of Commerce, and/or with APA manufacturing standards and specifications. The technical data in this Specification are presented as the basis for competent engineering design. For such design to result in satisfactory service, adequate materials and fabrication are also required. All wood structural panels should bear the trademark of APA – The Engineered Wood Association. The information contained herein is based on APA – The Engineered Wood Association’s continuing programs of laboratory testing, product research and comprehensive field experience. Neither APA, nor its members make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions or recommendations included in this publication. Consult your local jurisdiction or design professional to assure compliance with code, construction and performance requirements. Because APA has no control over quality of workmanship or the conditions under which engineered wood prod- ucts are used, it cannot accept responsibility for prod- uct performance or designs as actually constructed. Technical Services Division APA – The Engineered Wood Association T 4 Accept The Panel Load-Span Criteria Satisfied? Use Load-Span Tables (APA Technical Note, Form Q225) Select A Trial Panel Panel Design Specification Determine Required Allowable Capacities Adjusted Allowable Capacities Applied Capacities? Calculated Deflections Deflection Criteria? End-Use Conditions Consistent With Reference Conditions? No No No No No No Yes Yes Yes Yes DESIGNER FLOWCHART © 2008 APA - The Engineered Wood Association 5 PANEL DESI GN SPECI FI CATI ON 1. I NTRODUCTI ON Wood structural panels available today respond to changes in wood resources, manufacturing, and construction trends, meeting designer needs for excellent strength and light weight while using the only renewable build- ing material. A wood structural panel, also referred to as a structural-use panel, is a panel product composed pri- marily of wood, which, in its end use, is essentially dependent upon certain structural and/or physical properties for successful performance in service. Such a product is manufactured to stan- dards that clearly identify its intended end use. Today, wood structural pan- els include plywood and mat-formed panels such as oriented strand board (OSB). Composite panels containing a combination of veneer and wood-based material have also been produced. In the early days of plywood manu- facture, every mill worked with sev- eral species only and nearly identical technology. Manufacturing techniques didn’t vary much from mill to mill. To produce panels under prescriptive standards, a mill used wood of a cer- tain species, peeled it to veneer of a prescribed thickness, then glued the veneers together in a prescribed man- ner using approved adhesives. As technology changed, mills started using a broader range of species and different manufacturing techniques. With the development of U.S. Product St andard PS 1- 66 for Sof t wood Plywood – Construction & Industrial 1 , three existing plywood standards were combined into one. And, for the first time, span ratings for construction uses were incorporated into the standard. The span rating concept would later be used as a basis for the development of performance standards. At the same time, there was a growing need to increase efficient use of forest resources. Working in cooperation with the U.S. Forest Service, the American Plywood Association (APA) (now APA – The Engineered Wood Association) tested panels manufactured with a core of compressed wood strands and tradi- tional wood veneer on the face and back for use in structural applications. By using cores composed of wood strands, manufacturers were able to make more efficient use of the wood resource and use a broader range of species. These panels are called composite panels. In the course of the research on com- posite panels, performance standards were developed that led to a system of performance rated panels. Soon, man- ufacturers were making wood struc- tural panels composed entirely of wood strands. Most current production of these panels, intended for use in struc- tural applications, is referred to as ori- ented strand board, or OSB. 1.1. Plywood Plywood is the original wood structural panel. It is composed of thin sheets of veneer, or plies, arranged in layers to form a panel. Plywood always has an odd number of layers, each one consist- ing of one or more plies, or veneers. In plywood manufacture, a log is turned on a lathe and a long knife blade peels the veneer. The veneers are clipped to a suitable width, dried, graded, and repaired if necessary. Next the veneers are laid up in cross-laminated layers. Sometimes a layer will consist of two or more plies with the grain running in the same direction, but there will always be an odd number of layers, with the face layers typically having the grain oriented parallel to the long dimension of the panel. Moisture-resistant adhesive is applied to the veneers that are to be laid up. Laid- up veneers are then put in a hot press where they are bonded to form panels. Wood is strongest along its grain, and shrinks and swells most across the grain. By alternating grain direction between adjacent layers, strength and stiffness in both directions are maxi- mized, and shrinking and swelling are minimized in each direction. 1.2. Oriented strand board Panels manufactured of compressed wood wafers or strands have been mar- keted with such names as waferboard and oriented strand board. Today, vir- tually all mat-formed wood structural panels are manufactured with ori- ented strands or oriented wafers, and are commonly called oriented strand board (OSB). OSB is composed of compressed strands arranged in layers (usually three to five) oriented at right angles to one another, and bonded under heat and pressure with a moisture-resistant adhesive. The orientation of strands into directional layers achieves the same advantages of cross-laminated veneers in plywood. Since wood is stronger along the grain, the cross-lamination distributes wood’s natural strength in both directions of the panel. Whether a panel is com- posed of strands or wafers, most manu- facturers orient the material to achieve maximum performance. © 2008 APA - The Engineered Wood Association 6 Most OSB sheathing panels have a non- skid surface on one side for safety on the construction site, particularly when used as sheathing on pitched roofs. 1.3. Composite panels COM-PLY ® is an APA product name for composite panels that are manufac- tured by bonding layers of wood fibers between wood veneer. By combining reconstituted wood fibers with conven- tional veneer, COM-PLY panels allow for more efficient resource use while retaining the wood grain appearance on the panel face and back. COM-PLY panels are manufactured in a three- or five-layer arrangement. A three-layer panel has a wood fiber core and veneer for face and back. The five- layer panel has a wood veneer crossband in the center and veneer on the face and back. When manufactured in a one-step pressing operation, voids in the veneers are filled automatically by the reconsti- tuted wood particles or strands as the panel is pressed in the bonding process. At the present time COM-PLY panels as described above are not being produced and therefore should not be specified. 2 . SELECTI NG PANELS Wood structural panels are selected according to a number of key attri- butes. These attributes are identified in the APA trademark found on the panel. Examples are seen in Figure 1, and further explained in the paragraphs that follow. 2.1. Standards Manufacturing standards for wood structural panels are primarily of two types: prescriptive or performance based. In the past, plywood standards have been primarily of the prescriptive type. The prescriptive standard approach provides a recipe for panel layup, speci- fying the species of veneer and the num- ber, thickness and orientation of plies that are required to achieve panels of the desired nominal thickness and strength. A more recent development for wood structural panels is that of performance- based standards. Such standards specify performance levels required for com- mon end uses rather than manufactur- ing aspects of construction. Performance standards permit oriented strand board and plywood to be rated similarly for uses in the construction market. Another distinction between standards is whether they are consensus-based or proprietary. Consensus-based stan- dards are developed following a pre- scribed set of rules that provide for input and/or review by people of vary- ing interests following one of several recognized procedures. Other stan- dards are of a proprietary nature and may be developed by a single company or industry group. Sometimes proprie- tary standards become the forerunners of consensus standards. This was the case with APA’s proprietary standard PRP-108, Performance Standards and Qualification Policy for Structural-Use Panels 3 , which became the foundation for the consensus-based Voluntary Product Standard PS 2, which was developed to achieve broader recogni- tion of performance standards for wood structural panels. 2.1.1. Voluntary Product Standard PS 1 Voluntary Product Standard PS 1, Construction and Industrial Plywood 1 , is a consensus standard that originated in 1966 when it combined several pre- ceding U.S. Commercial Standards, each covering a different species of ply- wood. While originating as a prescrip- tive standard, the 1983 version added performance-based provisions as an alternative method of qualifying sheath- ing and single-floor grades of plywood RATED STURD-I-FLOOR EXPOSURE 1 24 oc 23/32 INCH 000 PS 1-07 UNDERLAYMENT PRP-108 SIZED FOR SPACING T&G NET WIDTH 47-1/2 1 2 3 4 5 6 7 8 RATED SHEATHING EXPOSURE 1 18mm CSA 0325 SIZED FOR SPACING 48/24 23/32 INCH CONSTRUCTION SHEATHING 2R48/2F24 000 PS 2-04 SHEATHING PRP-108 HUD-UM-40 STRENGTH AXIS THIS DIRECTION 1 2 4 5 6 7 11 12 8 13 14 15 2 4 5 1 7 9 8 6 10 11 RATED SIDING 303-18-S/W EXTERIOR 000 PS 1-07 PRP-108 HUD-UM-40 11/32 INCH GROUP 1 16 oc SIZED FOR SPACING 1 Panel grade 2 Span Rating 3 Tongue-and-groove 4 Bond classification 5 Product Standard 6 Thickness 7 Mill number 8 APA’s performance rated panel standard 9 Siding face grade 10 Species group number 11 HUD recognition 12 Panel grade, Canadian standard 13 Panel mark – Rating and end-use designation per the Canadian standard 14 Canadian performance rated panel standard 15 Panel face orientation indicator FIGURE 1 TYPICAL TRADEMARKS © 2008 APA - The Engineered Wood Association 7 for span ratings. PS 1 continues to offer only prescriptive provisions for other panel grades such as a variety of sanded plywood grades. 2.1.2. Voluntary Product Standard PS 2 Voluntary Product Standard PS 2 2 , Performance Standard for Wood-Based Structural-Use Panels, was promulgated in 1992 as the first consensus-based performance standard for wood struc- tural panels. The standard was based on APA’s PRP-108. PS 2 is not limited to plywood, but applies to all wood-based structural panels in general, regardless of composi- tion. It covers sheathing and single-floor grades only, and includes performance criteria, qualification requirements and test methods. Wood structural panels manufactured in conformance with PS 1 and PS 2 are recogni zed in all model building codes and most local codes in the United States. Also developed in concert with PS 2, with virtually identical provisions, was CSA- O325 12 , Con struc tion Sheathing, which is recognized in the National Building Code of Canada. 2.1.3. Proprietary standards The prototype proprietary perfor- mance standard for wood structural panels is APA PRP-108, Performance Standards and Qualification Policy for Structural-Use Panels. The APA stan- dard includes performance provisions for sheathing and single-floor grades, but also includes provisions for sid- ing. Although PRP-108, promulgated in 1980, is quite mature, it remains TABLE 1 CLASSIFICATION OF SPECIES (a) Each of these names represents a trade group of woods consisting of a number of closely related species. (b) Species from the genus Dipterocarpus marketed collectively: Apitong if originating in the Philippines, Keruing if originating in Malaysia or Indonesia. (c) Douglas-fir from trees grown in the states of Washington, Oregon, California, Idaho, Montana, Wyoming, and the Canadian Provinces of Alberta and British Columbia shall be classed as Douglas-fir No. 1. Douglas-fir from trees grown in the states of Nevada, Utah, Colorado, Arizona and New Mexico shall be classed as Douglas-fir No. 2. (d) Red Meranti shall be limited to species having a specific gravity of 0.41 or more based on green volume and oven dry weight. in effect to take advantage of techni- cal developments more expeditiously than would be possible with the rather time-consuming consensus process required by PS 2. 2.2. Veneer Wood veneer is at the heart of a ply- wood panel. The veneer used is clas- sified according to species group and grade requirements of PS 1. 2.2.1. Species groups While plywood can be manufactured from nearly any wood species, under PS 1 over 70 species of wood are rated for use based on strength and stiff- ness. This grouping into five Groups is presented in Table 1. Strongest species are in Group 1; the next strongest in Group 2, and so on. The Group number Group 3 Alder, Red Birch, Paper Cedar, Alaska Fir, Subalpine Hemlock, Eastern Maple, Bigleaf Pine Jack Lodgepole Ponderosa Spruce Redwood Spruce Engelmann White Group 4 Aspen Bigtooth Quaking Cativo Cedar Incense Western Red Cottonwood Eastern Black (Western Poplar) Pine Eastern White Sugar Group 5 Basswood Poplar, Balsam Cedar, Port Orford Cypress Douglas-fir 2 (c) Fir Balsam California Red Grand Noble Pacific Silver White Hemlock, Western Lauan Almon Bagtikan Mayapis Red Lauan Tangile White Lauan Maple, Black Mengkulang (a) Meranti, Red (a)(d) Mersawa (a) Pine Pond Red Virginia Western White Spruce Black Red Sitka Sweetgum Tamarack Yellow Poplar Group 2 Group 1 Apitong (a)(b) Beech, American Birch Sweet Yellow Douglas-fir 1 (c) Kapur (a) Keruing (a)(b) Larch, Western Maple, Sugar Pine Caribbean Ocote Pine, Southern Loblolly Longleaf Shortleaf Slash Tanoak © 2008 APA - The Engineered Wood Association 8 that appears in the trademark on most non-span-rated panels – primarily sanded grades – is based on the species used for face and back veneers. Where face and back veneers are not from the same species Group, the higher Group number (the lower strength species) is used, except for sanded panels 3/8 inch [9.5 mm] thick or less and Decorative panels of any thickness. These latter pan- els are identified by face species because they are chosen primarily for appear- ance and used in applications where structural integrity is not critical. Sanded panels greater than 3/8 inch [9.5 mm] are identified by face species if C or D grade backs are at least 1/8 inch [3 mm] and are no more than one species group number higher. Some species are used widely in plywood manufacture; others rarely. The specifier should check local availability if a particular species is desired. 2.2.2. Grades Veneer grades define veneer appear- ance in terms of natural unrepaired growth characteristics and allowable number and size of repairs that may be made during manufacture. See Table 2. The highest quality commonly available veneer grade is A. The minimum grade of veneer permitted in Exterior plywood is C-grade. D-grade veneer is used in panels intended for interior use or applications protected from long-term exposure to weather. 2.3. Panel grades Wood structural panel grades are gen- erally identified in terms of the veneer grade used on the face and back of the panel (e.g., A-B, B-C, etc.), or by a name suggesting the panel’s intended end use (e.g., APA Rated Sheathing, APA Rated Sturd-I-Floor, etc.). See Table 3. Unsanded and touch-sanded panels, and panels with B-grade or better veneer on one side only, usu- ally carry the trademark of a qualified inspection and testing agency (such as APA) on the panel back. Panels with both sides of B-grade or better veneer, or with special overlaid sur- faces (such as High Density Overlay) usually carry the trademark on the panel edge. 2.3.1. Unsanded Sheathing panels are unsanded since a smooth surface is not a requirement of their intended end use for subfloor, roof and wall applications. Sheathing panels are classified by span ratings, which identify the maximum recommended support spacings for specific end uses. Design capacities provided in 4.4 are on the basis of span ratings. Structural I sheathing panels meet the requirements of sheathing grades as well as enhanced requirements associ- ated with use in panelized roof sys- tems, diaphragms, and shear walls (e.g., increased cross-panel strength and stiffness, and increased racking shear resistance). 2.3.2. Touch-sanded Underlayment, Single Floor, C-D Plugged, and C-C Plugged grades require only touch sanding for “sizing” to make the panel thickness more uniform. Panels rated for single floor (combination subfloor-underlayment) applications are usually manufactured with tongue-and-groove (T&G) edge profiles, and are classified by span rat- ings. Panel span ratings identify the maximum recommended support spac- ings for floors. Design capacities pro- vided in 4.4 are on the basis of span ratings. Other thinner panels intended for separate underlayment applications (Underlayment or C-C Plugged) are identified with a species Group number but no span rating. 2.3.3. Sanded Plywood panels with B-grade or better veneer faces are always sanded smooth in manufacture to fulfill the require- ments of their intended end use – applications such as cabinets, shelving, furniture, built-ins, etc. Sanded grades are classed according to nominal TABLE 2 VENEER GRADES A Smooth, paintable. Not more than 18 neatly made repairs, boat, sled, or router type, and parallel to grain, permitted. Wood or synthetic repairs permitted. May be used for natural finish in less demanding applications. B Solid surface. Shims, sled or router repairs, and tight knots to 1 inch across grain permitted. Wood or synthetic repairs permitted. Some minor splits permitted. C Improved C veneer with splits limited to 1/8-inch width and knotholes or other open defects limited to 1/4 x 1/2 inch. Wood or synthetic repairs permitted. Admits some broken grain. Plugged C Tight knots to 1-1/2 inch. Knotholes to 1 inch across grain and some to 1-1/2 inch if total width of knots and knotholes is within specified limits. Synthetic or wood repairs. Discoloration and sanding defects that do not impair strength permitted. Limited splits allowed. Stitching permitted. D Knots and knotholes to 2-1/2 inch width across grain and 1/2 inch larger within specified limits. Limited splits are permitted. Stitching permitted. Limited to Exposure 1 or Interior panels. Note: 1 inch = 25.4 mm. © 2008 APA - The Engineered Wood Association 9 TABLE 3 GUIDE TO PANEL USE Panel Constructi on Common Nomi nal Panel Grade Descri pti on & Use Thi ckness OSB Pl ywood APA RATED Unsanded sheathing grade for wall, roof, subflooring, 5/16, Yes Yes SHEATHING and industrial applications such as pallets and for 3/8, 7/16*, EXP 1 engineering design with proper capacities. 15/32, 1/2, 19/32, 5/8 23/32, 3/4 APA Panel grades to use where shear and cross-panel 3/8, 7/16*, Yes Yes STRUCTURAL I strength properties are of maximum importance. 15/32, 1/2, RATED 19/32, 5/8, SHEATHING 23/32, 3/4 EXP 1 APA RATED Combination subfloor-underlayment. Provides smooth 19/32, 5/8 Yes Yes STURD-I-FLOOR surface for application of carpet and pad. Possesses 23/32, 3/4 EXP 1 high concentrated and impact load resistance during 7/8, 1 construction and occupancy. Touch-sanded. 1-3/32, 1-1/8 Available with tongue-and-groove edges. APA For underlayment under carpet and pad. Touch-sanded. 1/4 No Yes UNDERLAYMENT Available with tongue-and-groove edges. 11/32, 3/8 EXP 1 15/32, 1/2 19/32, 5/8 23/32, 3/4 APA For underlayment, refrigerated or controlled atmosphere 1/2 No Yes C- C Plugged storage rooms, open soffits and other similar applications 19/32, 5/8 EXT where continuous or severe moisture may be present. 23/32, 3/4 Touch-sanded. Available with tongue-and-groove edges. APA Generally applied where a high quality surface is required. 1/4, No Yes Sanded Includes APA A-A, A-B, A-C, A-D, B-B, B-C and B-D grades. 11/32, 3/8 Grades 15/32, 1/2 EXP 1 or EXT 19/32, 5/8 23/32, 3/4 APA Superior Exterior plywood made only with Douglas-fir or 1/4, No Yes MARINE Western Larch. Special solid-core construction. Available 11/32, 3/8 EXT with MDO or HDO face. Ideal for boat hull construction. 15/32, 1/2 19/32, 5/8 23/32, 3/4 *7/16 available in OSB only. Note: 1 inch = 25.4 mm. © 2008 APA - The Engineered Wood Association 10 thickness and the species group of the faces, and design capacities provided in 4.4 are on that basis and assume Group 1 faces. 2.3.4. Overlaid High Density Overlay (HDO) and Medium Density Overlay (MDO) ply- wood may or may not have sanded faces, depending on whether the over- lay is applied at the same time the panel is pressed (one-step) or after the panel is pressed (two-step). For purposes of assigning design capacities provided in 4.4, HDO and MDO panels are assumed to be sanded (two-step), which is conservative, with Group 1 faces. 2.4. Bond classifications Wood structural panels may be pro- duced in three bond classifications – Exterior, Exposure 1, and Interior. The bond classification relates to adhesive bond, and thus to structural integrity of the panel. By far the predominant bond classifications are Exposure 1 and Exterior. Therefore, design capacities provided herein are on that basis. Bond classification relates to moisture resistance of the glue bond and does not relate to fungal decay resistance of the panel. Fungal decay of wood prod- ucts may occur when the moisture con- tent exceeds approximately 20 percent for an extended period. Prevention of fungal decay is a function of proper design to prevent prolonged exposure to moisture, of material specification, of construction and of maintenance of the structure, or may be accomplished by pressure preservative treatment. See APA literature regarding decay and moisture exposure. Aesthetic (nonstructural) attributes of panels may be compromised to some degree by exposure to weather. Panel surfaces may become uneven and irregular under prolonged moisture exposure. Panels should be allowed to dry, and panel joints and surfaces may need to be sanded before applying some finish materials. 2.4.1. Exterior A bond classification for plywood suit- able for repeated wetting and redrying or long-term exposure to weather or other conditions of similar severity. 2.4.2. Exposure 1 A bond classification for panels suit- able for uses not permanently exposed to the weather. Panels classified as Exposure 1 are intended to resist the effects of moisture due to construction delays, or other conditions of similar severity. Exposure 1 panels are made with the same types of adhesives used in Exterior panels. However, because other compositional factors may affect bond performance, only Exterior pan- els should be used for long-term expo- sure to the weather. Exposure 1 panels may, however, be used where expo- sure to the outdoors is on the under- side only, such as at roof overhangs. Appearance characteristics of the panel grade should also be considered. C-D Exposure 1 plywood, sometimes called “CDX” in the trade, is occasionally mistaken as an Exterior panel and erro- neously used in applications for which it does not possess the required resistance to weather. “CDX” should only be used for applications as outlined above. 2.4.3. Other classifications Panels identified as Interior and that lack further glueline information in their trademarks are manufactured with inte- rior glue and are intended for interior applications only. Panels classed Interior were commonplace prior to the 1970s, but are not commonly produced today. 2.5 Span ratings Sheathing and Single Floor grades carry numbers in their trademarks called span ratings. These denote the maximum recommended center-to-center spacing of supports, in inches, over which the panels should be placed in construction applications. The span rating applies when the long panel dimension or strength axis is across supports, unless the strength axis is otherwise identified. 2.5.1. Sheathing The span rating on Sheathing grade panels appears as two numbers sepa- rated by a slash, such as 32/16, 48/24, etc. The left-hand number denotes the maximum recommended spacing of supports when the panel is used for roof sheathing with the long dimen- sion or strength axis of the panel across three or more supports (two or more spans). The right-hand number indi- cates the maximum recommended spacing of supports when the panel is used for subflooring with the long dimension or strength axis of the panel across three or more supports. A panel marked 32/16, for example, may be used for roof sheathing over supports up to 32 inches [800 mm] on center or for subflooring over supports up to 16 inches [400 mm] on center. Certain of the roof sheathing maxi- mum spans are dependent upon panel edge support as recommended in APA literature. Sheathing panels rated for use only as wall sheathing are usually identified as either Wall-24 or Wall-16. The numeri- cal index (24 or 16) corresponds to the maximum wall stud spacing in inches. Wall sheathing panels are performance tested with the secondary axis (usually the short dimension of panel) span- ning across supports, or studs. For this © 2008 APA - The Engineered Wood Association 11 reason, wall sheathing panels may be applied with either the strength axis or secondary axis across supports. 2.5.2. Single floor The span rating on Single Floor grade panels appears as a single number. Single Floor panels are designed spe- cifically for single-floor (combined sub- floor-underlayment) applications under carpet and pad and are manufactured with span ratings of 16, 20, 24, 32 and 48 oc. The span ratings for Single Floor panels, like those for Sheathing grade, are based on application of the panel with the long dimension or strength axis across three or more supports. 3 . CODE PROVI SI ONS Recommendations given in APA litera- ture for construction applications are generally consistent with provisions given in the model building codes in the United States. However, most of the information herein has been expanded compared to the code provisions, to be more useful to designers. The general APA recommendations apply primarily to conventional or non-engineered construction, but can also be considered conservative for engineered construction. On the other hand, for engineered construction, codes contain provisions for accep- tance of engineering calculations, and design capacities given herein may be used. In many cases, calculations using values in this document will lead to higher allowable design loads for sheathing. This is because the general APA and code recommendations are based on minimum structural require- ments or criteria of the performance standards, while the design capacities are based on actual characteristics of panels qualified under the performance standards. Since it would be difficult to manufacture a truly “minimum” panel with regard to all properties, most panel characteristics actually exceed requirements of the standards. Regardless of any increase in allow- able load based on calculations, always observe the maximum recommended span (e.g., span rating). Maximum span is established by test and is often controlled by concentrated load considerations. 4 . MECHANI CAL PROPERTI ES Wood structural panels can typically be incorporated into construction proj- ects without the need for engineering design of the panels themselves. They lend themselves to tabular and descrip- tive presentation of design recommen- dations and provisions. Occasionally, however, there is a need to engineer panel applications that call for panel properties or capacities; or it may be necessary to evaluate specific panel constructions that yield superior mechanical properties compared to those that are the basis for general use recommendations. 4.1. Strength axis A feature of most wood structural panel types, primarily plywood and OSB, is that there is a strength axis associated with their manufacture. The layered construction of both products, in which layers are oriented 90 degrees from one another, creates dissimilar properties in the two principal direc- tions. This is illustrated in Figure 2. The orientation of the face and back layer determines the direction of the strength axis. The panel strength axis is typically in the long panel direction; that is, the panel is typically stronger and stiffer along the panel length than across the panel width. Specification of panel ori- entation, then, can be stated as “strength axis is perpendicular (or parallel) to sup- ports” or, sometimes, “stress is parallel (or perpendicular) to the strength axis.” In the case of plywood or composite panels, the strength axis is sometimes referred to as the face grain direction. 4.2. Panel construction Plywood mills may use different layups for the same panel thickness and span rating to make optimum use of their raw material resources. Design cal- culations must take into account the direction in which the stresses will be imposed in the panel. If stresses can be expected in both directions, then both the parallel and perpendicular directions should be checked. For this reason, tabulated capacities are given for both directions. Capacities parallel to the face grain of plywood are based on a panel construc- tion that gives minimum values in that direction. (See Figure 3.) Capacities perpendicular to the face grain are usu- ally based on a different panel con- struction that gives minimum values in that direction. Both values, therefore, are conservative. Capacities given for the two directions are not necessarily for the same panel construction. Similar layers occur also in OSB manu- facture. However, the layers are not defined and therefore cannot be speci- fied. For this reason, ply-layer options are not tabulated for OSB. © 2008 APA - The Engineered Wood Association Strength Axis Direction Direction of Principal Stress A B 1' 4' 8' 1' 8' 4' FIGURE 2 TYPICAL WOOD STRUCTURAL PANEL WITH STRENGTH AXIS DIRECTION PERPENDICULAR TO OR ACROSS SUPPORTS (A) AND PARALLEL TO SUPPORTS (B). NOTE THE STANDARD 4' x 8' SIZE, STRENGTH AXIS DIRECTION, AND REPRESENTATIVE PORTION OF PANEL USED IN CALCULATION OF CAPACITIES FOR STRESS PARALLEL (A) OR PERPENDICULAR (B) TO THE STRENGTH AXIS. 12 © 2008 APA - The Engineered Wood Association Grain Direction of Veneers 3-layer (3-ply) 3-layer (4-ply) 5-layer (5-ply) 5-layer (6-ply) FIGURE 3 TYPICAL THREE- AND FIVE-LAYER PLYWOOD CONSTRUCTION WITH PARALLEL-LAMINATED CROSS BANDS IN THE 4- AND 6-PLY PANELS 13 4.3. Properties and stresses Plywood properties have traditionally been separately tabulated as section properties and design stresses. These are, of course, multiplied together to obtain a capacity. In many cases the resulting capacity will be quite conser- vative. Design stresses are conserva- tively developed, taking into account grade factors and manufacturing fac- tors, and then the data is statistically analyzed such that it represents the “low end” of possible values. The stress is then further adjusted by a load factor or, as some call it, a factor of safety. At the same time, section properties are developed for virtually all possible layup combinations of veneer thickness and species. The lowest property value for a given panel thickness or span rat- ing is then chosen for tabulation. The resulting capacity combines two already conservative values. In the 1990s, this procedure was largely replaced by direct publication of panel capacities. However, the section property and design stress technique is still used occasionally to analyze individual ply- wood layup variations. 4.4. Capacities Panel design capacities l i sted i n Tables 4A and 4B are minimum for grade and span rating or thickness. For Structural I panels, the tabulated capacities shall be permitted to be mul- tiplied by the “Structural I Multiplier” factors given in the bottom of each property table. Since Table 4B gives © 2008 APA - The Engineered Wood Association 14 capacities for sanded panels marked as species Group 1, Table 4C provides multipliers for sanded panel capacities that are identified as species Group 2, 3 or 4. The tabulated capacities are based on data from tests of panels bearing the APA trademark. To take advantage of these capacities and adjustments, the specifier must insure that the correct panel is used in the final construction. 4.4.1. Panel flexure (flat panel bending) Panel design capacities reported in Tables 4A and 4B are based on f lat panel bending as measured by testing according to the principles of ASTM D 3043 4 Method C (large panel testing). See Figure 4. Stiffness (EI) Panel bending stiffness is the capacity to resist deflection and is represented in bending equations as EI. The E is the modulus of elasticity of the material and the I is the moment of inertia of the cross section. Units of EI are lb-in. 2 per foot of panel width. Strength (F b S) Allowable bending strength capacity is the design maximum moment, rep- resented in bending equations as F b S. Terms are the allowable extreme fiber stress of the material (F b ) and the sec- tion modulus (S). Units of F b S are lb-in. per foot of panel width. 4.4.2. Panel axial strength Tension (F t A) Al lowable tension capacities are reported in Tables 4A and 4B based on testing according to the principles of ASTM D 3500 5 Method B. Tension capacity is given as F t A, where F t is the allowable axial tension stress of the material and A is the area of the cross section. Units of F t A are lb per foot of panel width. Compression (F c A) Allowable compression capacities are reported in Tables 4A and 4B based on testing according to the principles of ASTM D 3501 6 Method B. Compres sion capacity is given as F c A, where F c is the allowable axial compression stress of the material, and A is the area of the cross section. Units of F c A are lb per foot of panel width. Axial compression strength is illustrated in Figure 5. 4.4.3. Panel axial stiffness (EA) Panel axial stiffness is reported in Tables 4A and 4B based on testing according to the principles of ASTM D 3501 6 Method B. Axial stiffness is the capacity to resist axial strain and is rep- resented by EA. The E is the axial mod- ulus of elasticity of the material and A is the area of the cross section. Units of EA are lb per foot of panel width. 4.4.4. Shear in the plane of the panel (F s [lb/Q]) Allowable shear in the plane of the panel (or interlaminar shear, some- times called rolling shear in plywood) is reported in Tables 4A and 4B based on testing according to the principles of ASTM D 2718 7 . Shear strength in the plane of the panel is the capac- ity to resist horizontal shear breaking loads when loads are applied or devel- oped on opposite faces of the panel, as they are during flat panel bending. See Figure 6. The term F s is the allowable material stress, while lb/Q is the panel cross sectional shear constant. Units of F s (lb/Q) are lb per foot of panel width. 4.4.5. Panel shear through the thickness Panel shear-through-the-thickness capacities are reported based on testing according to the principles of ASTM D 2719 8 . See Figure 6. Panel shear strength through the thickness (F v t v ) Allowable shear through the thickness is the capacity to resist horizontal shear breaking loads when loads are applied or developed on opposite edges of the panel, such as they are in an I-beam, and is reported in Tables 4A and 4B. See Figure 6. Where additional support is not provided to prevent buckling, design capacities in Tables 4A and 4B are limited to sections 2 ft or less in depth. Deeper sections may require additional reductions. The term F v is the allowable stress of the material, while t v is the effective panel thickness for shear. Units of F v t v are lb per inch of shear-resisting panel length. FIGURE 4 STRUCTURAL PANEL IN BENDING – (A) STRESS PARALLEL TO STRENGTH AXIS AND (B) STRESS PERPENDICULAR TO STRENGTH AXIS A B © 2008 APA - The Engineered Wood Association 15 Panel rigidity through the thickness (G v t v ) Panel rigidity is reported in Tables 4A and 4B and is the capacity to resist defor mat ion when under shear- through-the-thickness stress. Rigidity is represented by G v t v , where G v is the modulus of rigidity and t v is the effec- tive panel thickness for shear. The units of G v t v are lb per inch of panel depth (for vertical applications). Multiplication of G v t v by panel depth gives GA, used by designers for some applications. 4.4.6. Panel allowable bearing stress (F c⊥ ) Bearing stress is the compression stress perpendicular to the plane of the plies or to the surface of the panel. As com- pression load is applied to panels (such as by columns or by reactions at sup- ports), bearing stress is induced through the bearing area. The allowable bearing stress of APA structural-use panels is derived based on the load at a 0.04-in. [1.0 mm] deformation limit. A design bearing stress of 360 psi [2.5 N/mm 2 ] shall be used for structural-use panels under dry-use conditions where mois- ture content is less than 16 percent. Multiplying the allowable bearing stress by the bearing area gives the bearing capacity, F c⊥ A, in pounds. A reduced design bearing stress may be appropriate where bearing deformation could affect load distribution or where total deformation of members must be FIGURE 6 TWO TYPES OF PANEL SHEAR: SHEAR THROUGH THE THICKNESS AND SHEAR IN THE PLANE OF THE PANEL Shear through the thickness Shear in the plane Shear area FIGURE 5 STRUCTURAL PANEL WITH AXIAL COMPRESSION LOAD IN THE PLANE OF THE PANEL © 2008 APA - The Engineered Wood Association 16 closely controlled. A conservative design value for 0.02-in. [0.5 mm] deforma- tion can be chosen as 50 percent of the allowable bearing stress at 0.04-in. [1.0 mm] deformation. If necessary, use the following regression equation to derive the design value for 0.02-in. [0.5 mm] deformation: F c⊥0.02" = 0.51F c⊥0.04" + 28 4.4.7 Dowel bearing strength Dowel bearing strength is a component in fastener yield equations, as found in the National Design Specification (NDS) for Wood Construction 13 . The yield equations are also sometimes referred to as the European Yield Model (EYM). Dowel bearing strength is mea- sured by testing according to the prin- ciples of ASTM D 5764 14 . Plywood trademarked Structural I or Marine grade can be taken as having a specific gravity of 0.50, based on the species limitations prescribed in PS 1. Plywood not identified as Structural I or Marine grade can be taken as hav- ing a specific gravity of 0.42, unless the species of plies is known, in which case the specific gravity listed for the actual species may be used. Dowel bearing strength of OSB listed below is conser- vative based on limited testing. The table below summarizes dowel bearing strength of wood structural panels using terminology contained in the NDS. 4.5. Adjustments Panel design capacities may be adjusted as required under the fol lowi ng provisions. 4.5.1. Duration of load (DOL) Design capacities listed are based on “normal duration of load” as tradition- ally used for solid wood in accordance with U.S. Forest Products Laboratory Report R-1916 9 , and successfully used for plywood for approximately 40 years. Adjust ment factors for strength capacities (C D ) are: allowance should be made for creep. Limited data indicates that under such conditions, creep may be taken into account in deflection calculations by applying the applicable following adjust- ment factor (C C ) to panel stiffness, EI: Dowel Beari ng Strength, F e Wood Structural Panel Speci fi c Gravi ty, G For Nai l ed Connecti ons Plywood Structural I, Marine 0.50 4,650 psi [32 MPa] Other grades (a) 0.42 3,350 psi [23 MPa] Oriented Strand Board All grades 0.50 4,650 psi [32 MPa] (a) Use G = 0.42 when species of the plies is not known. When species of the plies is known, specific gravity listed for the actual species and the corresponding dowel bearing strength may be used, or the weighted average may be used for mixed species. DOL Adj ustment Ti me Under Load Factor * (C D ) Permanent 0.90 Normal 1.00 Two Months 1.15 Seven Days 1.25 Wind or Earthquake 1.60** *Adjustment for impact load does not apply to structural-use panels. **Check local building code. Creep Adj ustment Factor (C c ) for Permanent Loads Moi sture Condi ti on Pl ywood OSB Dry 1/2 1/2 16% m.c. or greater 1/2 1/6 Moi sture Content Adj ustment Capaci ty Factor (C m ) Strength (F b S, F t A, F c A, F s [lb/Q], F v t v ) 0.75 Stiffness (EI, EA, G v t v ) 0.85 Bearing (F c⊥ A) Plywood 0.50 OSB 0.20 Creep Wood-based panels under constant load will creep (deflection will increase) over time. For typical construction applica- tions, panels are not normally under constant load and, accordingly, creep need not be considered in design. When panels will sustain permanent loads that will stress the product to one-half or more of its design strength capacity, See 4.5.2 for additional adjustments related to service moisture conditions, which for EI is cumulative with the adjustment for creep. 4.5.2. Service moisture conditions Design capacities apply to panels under moisture conditions that are contin- uously dry in service; that is, where equilibrium moisture content is less than 16 percent. Adjustment factors for conditions where the panel moisture content in service is expected to be 16 percent or greater (C m ) are as follows: © 2008 APA - The Engineered Wood Association 17 TABLE 4A RATED PANELS DESIGN CAPACITIES Stress Paral l el to Strength Axi s Stress Perpendi cul ar to Strength Axi s Span Pl ywood Pl ywood Rati ng 3- pl y 4- pl y 5- pl y OSB 3- pl y 4- pl y 5- pl y OSB PANEL BENDING STIFFNESS, EI (lb-in. 2 / ft of panel width) 24/0 66,000 66,000 66,000 60,000 3,600 7,900 11,000 11,000 24/16 86,000 86,000 86,000 78,000 5,200 11,500 16,000 16,000 32/16 125,000 125,000 125,000 115,000 8,100 18,000 25,000 25,000 40/20 250,000 250,000 250,000 225,000 18,000 39,500 56,000 56,000 48/24 440,000 440,000 440,000 400,000 29,500 65,000 91,500 91,500 16 oc 165,000 165,000 165,000 150,000 11,000 24,000 34,000 34,000 20 oc 230,000 230,000 230,000 210,000 13,000 28,500 40,500 40,500 24 oc 330,000 330,000 330,000 300,000 26,000 57,000 80,500 80,500 32 oc 715,000 715,000 715,000 650,000 75,000 165,000 235,000 235,000 48 oc 1,265,000 1,265,000 1,265,000 1,150,000 160,000 350,000 495,000 495,000 Structural I Multiplier 1.0 1.0 1.0 1.0 1.5 1.5 1.6 1.6 PANEL BENDING STRENGTH, F b S (lb-in./ ft of panel width) 24/0 250 275 300 300 54 65 97 97 24/16 320 350 385 385 64 77 115 115 32/16 370 405 445 445 92 110 165 165 40/20 625 690 750 750 150 180 270 270 48/24 845 930 1,000 1,000 225 270 405 405 16 oc 415 455 500 500 100 120 180 180 20 oc 480 530 575 575 140 170 250 250 24 oc 640 705 770 770 215 260 385 385 32 oc 870 955 1,050 1,050 380 455 685 685 48 oc 1,600 1,750 1,900 1,900 680 815 1,200 1,200 Structural I Multiplier 1.0 1.0 1.0 1.0 1.3 1.4 1.5 1.5 PANEL AXIAL TENSION, F t A (lb/ ft of panel width) 24/0 2,300 2,300 3,000 2,300 600 600 780 780 24/16 2,600 2,600 3,400 2,600 990 990 1,300 1,300 32/16 2,800 2,800 3,650 2,800 1,250 1,250 1,650 1,650 40/20 2,900 2,900 3,750 2,900 1,600 1,600 2,100 2,100 48/24 4,000 4,000 5,200 4,000 1,950 1,950 2,550 2,550 16 oc 2,600 2,600 3,400 2,600 1,450 1,450 1,900 1,900 20 oc 2,900 2,900 3,750 2,900 1,600 1,600 2,100 2,100 24 oc 3,350 3,350 4,350 3,350 1,950 1,950 2,550 2,550 32 oc 4,000 4,000 5,200 4,000 2,500 2,500 3,250 3,250 48 oc 5,600 5,600 7,300 5,600 3,650 3,650 4,750 4,750 Structural I Multiplier 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 PANEL AXIAL COMPRESSION, F c A (lb/ ft of panel width) 24/0 2,850 4,300 4,300 2,850 2,500 3,750 3,750 2,500 24/16 3,250 4,900 4,900 3,250 2,500 3,750 3,750 2,500 32/16 3,550 5,350 5,350 3,550 3,100 4,650 4,650 3,100 40/20 4,200 6,300 6,300 4,200 4,000 6,000 6,000 4,000 48/24 5,000 7,500 7,500 5,000 4,800 7,200 7,200 4,300 16 oc 4,000 6,000 6,000 4,000 3,600 5,400 5,400 3,600 20 oc 4,200 6,300 6,300 4,200 4,000 6,000 6,000 4,000 24 oc 5,000 7,500 7,500 5,000 4,800 7,200 7,200 4,300 32 oc 6,300 9,450 9,450 6,300 6,200 9,300 9,300 6,200 48 oc 8,100 12,150 12,150 8,100 6,750 10,800 10,800 6,750 Structural I Multiplier 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 © 2008 APA - The Engineered Wood Association 18 TABLE 4A (Continued) RATED PANELS DESIGN CAPACITIES Stress Paral l el to Strength Axi s Stress Perpendi cul ar to Strength Axi s Span Pl ywood Pl ywood Rati ng 3- pl y 4- pl y 5- pl y OSB 3- pl y 4- pl y 5- pl y OSB PANEL AXIAL STIFFNESS, EA (lb/ ft of panel width) 24/0 3,350,000 3,350,000 3,350,000 3,350,000 2,900,000 2,900,000 2,900,000 2,500,000 24/16 3,800,000 3,800,000 3,800,000 3,800,000 2,900,000 2,900,000 2,900,000 2,700,000 32/16 4,150,000 4,150,000 4,150,000 4,150,000 3,600,000 3,600,000 3,600,000 2,700,000 40/20 5,000,000 5,000,000 5,000,000 5,000,000 4,500,000 4,500,000 4,500,000 2,900,000 48/24 5,850,000 5,850,000 5,850,000 5,850,000 5,000,000 5,000,000 5,000,000 3,300,000 16 oc 4,500,000 4,500,000 4,500,000 4,500,000 4,200,000 4,200,000 4,200,000 2,700,000 20 oc 5,000,000 5,000,000 5,000,000 5,000,000 4,500,000 4,500,000 4,500,000 2,900,000 24 oc 5,850,000 5,850,000 5,850,000 5,850,000 5,000,000 5,000,000 5,000,000 3,300,000 32 oc 7,500,000 7,500,000 7,500,000 7,500,000 7,300,000 7,300,000 7,300,000 4,200,000 48 oc 8,200,000 8,200,000 8,200,000 8,200,000 7,300,000 7,300,000 7,300,000 4,600,000 Structural I Multiplier 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 PANEL SHEAR IN THE PLANE, F s (lb/ Q) (lb/ ft of panel width) 24/0 155 155 170 130 275 375 130 130 24/16 180 180 195 150 315 435 150 150 32/16 200 200 215 165 345 480 165 165 40/20 245 245 265 205 430 595 205 205 48/24 300 300 325 250 525 725 250 250 16 oc 245 245 265 205 430 595 205 205 20 oc 245 245 265 205 430 595 205 205 24 oc 300 300 325 250 525 725 250 250 32 oc 360 360 390 300 630 870 300 300 48 oc 460 460 500 385 810 1,100 385 385 Structural I Multiplier 1.4 1.4 1.4 1.0 1.4 1.4 1.0 1.0 PANEL RIGIDITY THROUGH THE THICKNESS, G v t v (lb/ in. of panel depth) 24/0 25,000 32,500 37,500 77,500 25,000 32,500 37,500 77,500 24/16 27,000 35,000 40,500 83,500 27,000 35,000 40,500 83,500 32/16 27,000 35,000 40,500 83,500 27,000 35,000 40,500 83,500 40/20 28,500 37,000 43,000 88,500 28,500 37,000 43,000 88,500 48/24 31,000 40,500 46,500 96,000 31,000 40,500 46,500 96,000 16 oc 27,000 35,000 40,500 83,500 27,000 35,000 40,500 83,500 20 oc 28,000 36,500 42,000 87,000 28,000 36,500 42,000 87,000 24 oc 30,000 39,000 45,000 93,000 30,000 39,000 45,000 93,000 32 oc 36,000 47,000 54,000 110,000 36,000 47,000 54,000 110,000 48 oc 50,500 65,500 76,000 155,000 50,500 65,500 76,000 155,000 Structural I Multiplier 1.3 1.3 1.1 1.0 1.3 1.3 1.1 1.0 PANEL SHEAR THROUGH THE THICKNESS, F v t v (lb/ in. of shear-resisting panel length) 24/0 53 69 80 155 53 69 80 155 24/16 57 74 86 165 57 74 86 165 32/16 62 81 93 180 62 81 93 180 40/20 68 88 100 195 68 88 100 195 48/24 75 98 115 220 75 98 115 220 16 oc 58 75 87 170 58 75 87 170 20 oc 67 87 100 195 67 87 100 195 24 oc 74 96 110 215 74 96 110 215 32 oc 80 105 120 230 80 105 120 230 48 oc 105 135 160 305 105 135 160 305 Structural I Multiplier 1.3 1.3 1.1 1.0 1.3 1.3 1.1 1.0 © 2008 APA - The Engineered Wood Association 19 TABLE 4B SANDED GROUP 1 (a) PLYWOOD DESIGN CAPACITIES Nomi nal Thi ckness Stress Paral l el to Strength Axi s Stress Perpendi cul ar to Strength Axi s (i n.) A- A, A- C Mari ne Other A- A, A- C Mari ne Other PANEL BENDING STIFFNESS, EI (lb-in. 2 / ft of panel width) 1/4 15,000 15,000 15,000 700 980 700 11/32 34,000 34,000 34,000 1,750 2,450 1,750 3/8 49,000 49,000 49,000 2,750 3,850 2,750 15/32 120,000 120,000 120,000 11,000 15,500 11,000 1/2 140,000 140,000 140,000 15,500 21,500 15,500 19/32 205,000 205,000 205,000 37,500 52,500 37,500 5/8 230,000 230,000 230,000 48,500 68,000 48,500 23/32 320,000 320,000 320,000 90,500 125,000 90,500 3/4 355,000 355,000 355,000 115,000 160,000 115,000 7/8 500,000 500,000 500,000 185,000 260,000 185,000 1 760,000 760,000 760,000 330,000 460,000 330,000 1-1/8 985,000 985,000 985,000 490,000 685,000 490,000 Structural I Multiplier 1.0 1.0 1.0 1.4 1.0 1.4 PANEL BENDING STRENGTH, F b S (lb-in./ ft of panel width) 1/4 115 105 95 17 20 14 11/32 185 170 155 31 36 26 3/8 245 225 205 44 52 37 15/32 425 390 355 130 150 110 1/2 470 430 390 175 205 145 19/32 625 570 520 270 315 225 5/8 670 615 560 325 380 270 23/32 775 710 645 455 530 380 3/4 815 750 680 565 660 470 7/8 1,000 935 850 780 910 650 1 1,300 1,200 1,100 1,150 1,350 975 1-1/8 1,600 1,500 1,350 1,500 1,750 1,250 Structural I Multiplier 1.0 1.0 1.1 1.4 1.0 1.4 PANEL AXIAL TENSION, F t A (lb/ ft of panel width) 1/4 1,800 1,650 1,650 660 990 550 11/32 1,800 1,650 1,650 840 1,250 700 3/8 2,350 2,150 2,150 1,250 1,900 1,050 15/32 3,500 3,200 3,200 2,400 3,600 2,000 1/2 3,500 3,200 3,200 2,450 3,700 2,050 19/32 4,400 4,000 4,000 2,750 4,150 2,300 5/8 4,500 4,100 4,100 3,000 4,500 2,500 23/32 5,100 4,650 4,650 3,400 5,150 2,850 3/4 5,250 4,750 4,750 4,150 6,200 3,450 7/8 5,350 4,850 4,850 5,200 7,850 4,350 1 6,750 6,150 6,150 6,250 9,350 5,200 1-1/8 7,000 6,350 6,350 6,300 9,450 5,250 Structural I Multiplier 1.0 1.0 1.0 1.7 1.0 1.8 (a) See Table 4C for multipliers for other species Groups. © 2008 APA - The Engineered Wood Association 20 TABLE 4B (Continued) SANDED GROUP 1 (a) PLYWOOD DESIGN CAPACITIES Nomi nal Thi ckness Stress Paral l el to Strength Axi s Stress Perpendi cul ar to Strength Axi s (i n.) A- A, A- C Mari ne Other A- A, A- C Mari ne Other PANEL AXIAL COMPRESSION F c A (lb/ ft of panel width) 1/4 1,710 1,550 1,550 605 990 550 11/32 1,710 1,550 1,550 715 1,150 650 3/8 2,200 2,000 2,000 1,050 1,700 950 15/32 3,300 3,000 3,000 2,050 3,350 1,850 1/2 3,300 3,000 3,000 2,100 3,400 1,900 19/32 4,150 3,750 3,750 2,350 3,850 2,150 5/8 4,200 3,800 3,800 2,600 4,250 2,350 23/32 4,800 4,350 4,350 2,900 4,750 2,650 3/4 4,900 4,450 4,450 3,500 5,750 3,200 7/8 5,000 4,550 4,550 4,500 7,400 4,100 1 6,350 5,750 5,750 5,350 8,750 4,850 1-1/8 6,550 5,950 5,950 5,400 8,800 4,900 Structural I Multiplier 1.0 1.0 1.0 1.8 1.0 1.8 PANEL AXIAL STIFFNESS, EA (lb/ ft of panel width) 1/4 1,800,000 1,800,000 1,800,000 625,000 1,150,000 625,000 11/32 1,800,000 1,800,000 1,800,000 750,000 1,350,000 750,000 3/8 2,350,000 2,350,000 2,350,000 1,150,000 2,050,000 1,150,000 15/32 3,500,000 3,500,000 3,500,000 2,150,000 3,850,000 2,150,000 1/2 3,500,000 3,500,000 3,500,000 2,250,000 4,050,000 2,250,000 19/32 4,350,000 4,350,000 4,350,000 2,500,000 4,500,000 2,500,000 5/8 4,450,000 4,450,000 4,450,000 2,750,000 4,950,000 2,750,000 23/32 5,100,000 5,100,000 5,100,000 3,150,000 5,650,000 3,150,000 3/4 5,200,000 5,200,000 5,200,000 3,750,000 6,750,000 3,750,000 7/8 5,300,000 5,300,000 5,300,000 4,750,000 8,550,000 4,750,000 1 6,700,000 6,700,000 6,700,000 5,700,000 10,500,000 5,700,000 1-1/8 6,950,000 6,950,000 6,950,000 5,700,000 10,500,000 5,700,000 Structural I Multiplier 1.0 1.0 1.0 1.8 1.0 1.8 PANEL SHEAR IN THE PLANE, F s (lb/ Q) (lb/ ft of panel width) 1/4 105 135 105 105 135 105 11/32 145 190 145 145 190 145 3/8 165 215 165 165 215 165 15/32 220 285 220 220 285 220 1/2 235 305 235 235 305 235 19/32 290 375 290 290 375 290 5/8 310 405 310 310 405 310 23/32 350 455 350 350 455 350 3/4 360 470 360 360 470 360 7/8 425 555 425 425 555 425 1 470 610 470 470 610 470 1-1/8 525 685 525 525 685 525 Structural I Multiplier 1.3 1.0 1.3 1.4 1.0 1.4 (a) See Table 4C for multipliers for other species Groups. © 2008 APA - The Engineered Wood Association 21 TABLE 4B (Continued) SANDED GROUP 1 (a) PLYWOOD DESIGN CAPACITIES Nomi nal Thi ckness Stress Paral l el to Strength Axi s Stress Perpendi cul ar to Strength Axi s (i n.) A- A, A- C Mari ne Other A- A, A- C Mari ne Other PANEL RIGIDITY THROUGH THE THICKNESS G v t v (lb/ in. of panel depth) 1/4 24,000 31,000 24,000 24,000 31,000 24,000 11/32 25,500 33,000 25,500 25,500 33,000 25,500 3/8 26,000 34,000 26,000 26,000 34,000 26,000 15/32 38,000 49,500 38,000 38,000 49,500 38,000 1/2 38,500 50,000 38,500 38,500 50,000 38,500 19/32 49,000 63,500 49,000 49,000 63,500 49,000 5/8 49,500 64,500 49,500 49,500 64,500 49,500 23/32 50,500 65,500 50,500 50,500 65,500 50,500 3/4 51,000 66,500 51,000 51,000 66,500 51,000 7/8 52,500 68,500 52,500 52,500 68,500 52,500 1 73,500 95,500 73,500 73,500 95,500 73,500 1-1/8 75,000 97,500 75,000 75,000 97,500 75,000 Structural I Multiplier 1.3 1.0 1.3 1.3 1.0 1.3 PANEL SHEAR THROUGH THE THICKNESS, F v t v (lb/ in. of shear-resisting panel length) 1/4 51 66 51 51 66 51 11/32 54 70 54 54 70 54 3/8 55 72 55 55 72 55 15/32 80 105 80 80 105 80 1/2 81 105 81 81 105 81 19/32 105 135 105 105 135 105 5/8 105 135 105 105 135 105 23/32 105 135 105 105 135 105 3/4 110 145 110 110 145 110 7/8 110 145 110 110 145 110 1 155 200 155 155 200 155 1-1/8 160 210 160 160 210 160 Structural I Multiplier 1.3 1.0 1.3 1.3 1.0 1.3 (a) See Table 4C for multipliers for other species Groups. 4.5.3. Elevated temperature Capacities in Tables 4A and 4B apply at temperatures of 70° F [21° C] and lower. Wood structural panel parts of buildings should not be exposed to temperatures above 200° F [93° C] for more than very brief periods. However, between 70° F [21° C] and 200° F [93° C] adjustments to capacity generally do not need to be made, because the need for adjustment of dry capacities depends upon whether moisture con- tent will remain in the 12 to 15 per- cent range or whether the panel will dry to lower moisture contents as a result of the increase in temperature. If drying occurs, as is usually the case, the increase in strength due to dry- ing can offset the loss in strength due to elevated temperature. For instance, temperatures of up to 150° F [66° C] or higher do occur under roof cover- ings of buildings on hot days, but they are accompanied by moisture content reductions which offset the strength loss so that high temperatures are not considered in the design of roof struc- tures. To maintain a moisture content of 12 percent at 150° F [66° C], sus- tained relative humidity of around 80% would be required. The designer needs to exercise judgment in determining whether high temperature and mois- ture content occur simultaneously, and the corresponding need for temperature adjustment of capacities. 4.5.4. Pressure treatment Preservative treatment Capacities given in this document apply, without adjustment, to plywood pressure-impregnated with preserva- tive chemicals and redried in accor- dance with American Wood Preservers Association (AWPA) Standard C-9 10 . © 2008 APA - The Engineered Wood Association 22 Due to the absence of applicable treating industry standards, OSB panels are not currently recommended for applications requiring pressure-preservative treating. Fire-retardant treatment Discussion in this document does not apply to fire-retardant-treated struc- tural panels. However, some general information on fire-retardant treated plywood roof sheathing is available in a bulletin 11 from APA – The Engineered Wood Association. For fire-retardant- treated plywood, all capacities and end- use conditions shall be in accordance with the recommendations and/or model code evaluation reports of the company providing the treating and redrying service. 4.5.5. Panel size Strength capacity in bending and tension are appropriate for panels 24 inches [600 mm] or greater in width. For panels less than 24 inches [600 mm] in width used in applications where failure could endanger human life, the following adjustment shall be made to capacity (x is the width, or dimension perpendicular to the applied stress): When x is 24 inches [600 mm] or greater, then C s = 1.00 When x is a minimum of 8 inches [200 mm] to a maximum of 24 inches [600 mm], then C s = 0.25 + 0.0313x When x is less than or equal to 8 inches [200 mm], then C s = 0.50 Single strips less than 8 inches [200 mm] wide used in stressed applications shall be chosen such that they are rela- tively free of surface defects. TABLE 4C MULTIPLIERS FOR SANDED GROUP 2, 3 AND 4 PLYWOOD DESIGN CAPACITIES Speci es Group A- A, A- C Mari ne Other PANEL BENDING STIFFNESS, EI (lb-in. 2 / ft of panel width) 2 0.83 NA 0.83 3 0.67 NA 0.67 4 0.56 NA 0.56 PANEL BENDING STRENGTH, F b S (lb-in./ ft of panel width) 2 0.70 NA 0.73 3 0.70 NA 0.73 4 0.67 NA 0.67 PANEL AXIAL TENSION, F t A (lb/ ft of panel width) 2 0.70 NA 0.73 3 0.70 NA 0.73 4 0.67 NA 0.67 PANEL AXIAL COMPRESSION, F c A (lb/ ft of panel width) 2 0.73 NA 0.71 3 0.65 NA 0.64 4 0.61 NA 0.62 PANEL AXIAL STIFFNESS, EA (lb/ ft of panel width) 2 0.83 NA 0.83 3 0.67 NA 0.67 4 0.56 NA 0.56 PANEL SHEAR IN THE PLANE, F s (lb/ Q) (lb/ ft of panel width) 2 1.00 NA 1.00 3 1.00 NA 1.00 4 1.00 NA 1.00 PANEL RIGIDITY THROUGH THE THICKNESS, G v t v (lb/ in. of panel depth) 2 0.83 NA 0.83 3 0.67 NA 0.67 4 0.56 NA 0.56 PANEL SHEAR THROUGH THE THICKNESS, F v t v (lb/ in. of shear-resisting panel length) 2 0.74 NA 0.74 3 0.74 NA 0.74 4 0.68 NA 0.68 Also, additional panel edge support is recommended in applications subject to walking loads, such as floor or roof sheathing. 4.6. Section properties Where required, geometric cross- sectional properties may be calculated by assuming a uniform rectangular cross section in conjunction with nomi- nal panel thickness given in Table 5. Computed rectangular (geometric) properties on a per-foot-of-panel-width basis are provided in Table 6. Similarly, where design stress i s required, design capacity may be divided by the applicable rectangular section property in Table 6. © 2008 APA - The Engineered Wood Association 23 TABLE 5 NOMINAL THICKNESS BY SPAN RATING (The nominal thickness is given. The predominant thickness for each span rating is highlighted in bol d type.) Span Nomi nal Thi ckness (i n.) Rati ng 3/ 8 7/ 16 15/ 32 1/ 2 19/ 32 5/ 8 23/ 32 3/ 4 7/ 8 1 1-1/ 8 APA Rated Sheathing 24/0 .375 .437 .469 .500 24/16 .437 .469 .500 32/16 .469 .500 .594 .625 40/20 .594 .625 .719 .750 48/24 .719 .750 .875 APA Rated Sturd-I-Floor 16 oc .594 .625 20 oc .594 .625 24 oc .719 .750 32 oc .875 1.000 48 oc 1.125 Note: 1 inch = 25.4 mm. TABLE 6 PANEL SECTION PROPERTIES (a) Nomi nal Nomi nal Moment of Secti on Stati cal Shear Panel Approxi mate Thi ckness Area Iner ti a Modul us Moment Constant Thi ckness Wei ght (b) t A I S Q l b/ Q (i n.) (psf ) (i n.) (i n. 2 / f t) (i n. 4 / f t) (i n. 3 / f t) (i n. 3 / f t) (i n. 2 / f t) 3/8 1.1 .375 4.500 .053 .281 .211 3.000 7/16 1.3 .437 5.250 .084 .383 .287 3.500 15/32 1.4 .469 5.625 .103 .440 .330 3.750 1/2 1.5 .500 6.000 .125 .500 .375 4.000 19/32 1.8 .594 7.125 .209 .705 .529 4.750 5/8 1.9 .625 7.500 .244 .781 .586 5.000 23/32 2.2 .719 8.625 .371 1.033 .775 5.750 3/4 2.3 .750 9.000 .422 1.125 .844 6.000 7/8 2.6 .875 10.500 .670 1.531 1.148 7.000 1 3.0 1.000 12.000 1.000 2.000 1.500 8.000 1-1/8 3.3 1.125 13.500 1.424 2.531 1.898 9.000 Note: 1 inch = 25.4 mm; 1 psf = 4.88 kg/m 2 ; 1 in. 2 /ft width = 2116.67 mm 2 /m width; 1 in. 3 /ft width = 53763 mm 3 /m width; 1 in. 4 /ft width = 1.3656x10 6 mm 4 /m width. (a) Properties based on rectangular cross section of 1-ft width. (b) Approximate plywood weight for calculating actual dead loads. For OSB panels, increase tabulated weights by 10%. © 2008 APA - The Engineered Wood Association 24 4.7. Uniform load computations Computation of uniform-load capacity of wood structural panels shall be as out- lined in this section for such applications as roofs, floors and walls. The design capacities are subject to adjustment as specified earlier in this document. Three basic span conditions are pre- sented for computing uniform-load capacities of wood structural panels. For normal framing practice and a standard panel size (4 x 8 ft [1200 x 2400 mm]), APA has used the follow- ing assumptions in computing recom- mendations for load-span tables. When the panel strength axis is across (per- pendicular to) the supports, the three- span condition is assumed for support spacing up to and including 32 inches [800 mm]. The two-span condition is assumed for support spacing greater than 32 inches [800 mm]. When the panel strength axis is placed parallel to the supports, the three- span condition is assumed for support spacing up to and including 16 inches [400 mm], the two-span condition is assumed when the support spacing is greater than 16 inches [400 mm] up to 24 inches [600 mm], and a single span is assumed for spans greater than 24 inches [600 mm]. To include the effects of support width in deflection and shear strength cal- culations, two-inch-nominal [38 mm] lumber framing is assumed for sup- port spacings less than 48 inches [1200 mm]. Four-inch-nominal [89 mm] lumber framing is assumed for sup- port spacing of 48 inches [1200 mm] or greater. The equations presented in this section are standard beam formulas altered to accept the mixed units noted. These formulas are provided for computing uniform loads on wood structural pan- els over conventional lumber framing. Because it is assumed that no blocking is used, the formulas are for one-way “beam” action, rather than two-way “plate” action. The resulting loads are assumed to be applied to full-sized pan- els in standard sheathing-type applica- tions. Loads are for the panels only, and in no way account for the design of the framing supports. Further consider- ation should be given to concentrated loads, in compliance with local build- ing codes and with maximum span rec- ommendations of APA – The Engineered Wood Association. 4.7.1. Uniform loads based on bending strength The following formulas shall be used for computing loads based on design bending strength capacity (F b S). For a single span: w b = 96 F b S l 1 2 For a two-span condition: w b = 96 F b S l 1 2 For a three-span condition: w b = 120 F b S l 1 2 Where: w b = uniform load based on bending strength (psf) F b S = design bending strength capacity (lb-in./ft) l 1 = span (in., center-to-center of supports) 4.7.2. Uniform loads based on shear strength The following formulas shall be used for computing loads based on design shear strength capacity (F s [lb/Q]). For a single span: w s = 24 F s (lb/Q) l 2 For a two-span condition: w s = 19.2 F s (lb/Q) l 2 For a three-span condition: w s = 20 F s (lb/Q) l 2 Where: w s = uniform load based on shear strength (psf) F s (lb/Q) = design shear strength capacity (lb/ft) l 2 = clear span (in., center-to-center of supports minus support width) 4.7.3. Uniform loads based on deflec- tion requirements The following formulas shall be used for computing deflection under uni- form load, or allowable loads based on deflection requirements. For a single span: wl 3 4 Δ = 921.6 EI For a two-span condition: wl 3 4 Δ = 2220 EI For a three-span condition: wl 3 4 Δ = 1743 EI Where: Δ = deflection (in.) w = uniform load (psf) EI = design bending stiffness capacity (lb-in. 2 /ft) l 3 = clear span + SW (in.) SW = support-width factor, equal to 0.25 inch [6.5 mm] for two-inch- nominal [38 mm] lumber framing and 0.625 inch [16 mm] for four-inch-nomi- nal [89 mm] lumber framing. © 2008 APA - The Engineered Wood Association 25 4.7.4. Uniform load For uniform load based on a deflection requirement, compute bending deflec- tion with a uniform load (w) equal to one psf. The allowable uniform load based on the allowable deflection is then computed as: w d = Δ all. Δ Where: w d = uniform load based on deflection (psf) Δ all. = allowable deflection (in.) 4.8. Design examples showing use of capacity tables Note: In these examples, panel type and construction are selected for illustrative purposes. Normally specification is by grade and span rating without regard to panel type, and calculations should assume the lowest capacities applicable to available types and constructions as given in Table 7 for the specified span rating. 4.8.1. Example 1 – Conventional roof A 4-ply plywood panel trademarked APA Rated Sturd-I-Floor 24 oc with tongue-and-groove edges was inadver- tently installed over 4-in.-nominal [89 mm] roof supports 48 in. [1200 mm] on center. The long dimension (strength axis) of the panel was placed perpendic- ular to supports. The local building code requires that the panel support a 25-psf [1200 N/m 2 ] snow load. Bending Strength From Table 4A, a 4-ply plywood Rated Sturd-I-Floor 24 oc panel with stress applied parallel to the strength axis (long panel dimension perpendicular to sup- ports) has a bending strength capacity (F b S) of 705 lb-in./ft [261 N•m/m]. This capacity is adjusted by a duration-of-load factor (C D ) of 1.15 (see 4.5.1). From 4.7, a two-span condition is assumed. w b = 96 F b S l 1 2 = 96 x (705 x 1.15) 48 2 = 34 psf [1628 N/m 2 ] Shear Strength in the Plane From Table 4A, a 4-ply plywood Rated Sturd-I-Floor 24 oc panel with stress applied parallel to the strength axis has shear strength in the plane (F s [lb/Q]) of 300 lb/ft [4378 N/m]. This capacity is adjusted by a duration-of-load factor (C D ) of 1.15 (see 4.5.1). w s = 19.2 F s (lb/Q) l 2 = 19.2 (300 x 1.15) (48 – 3.5) = 149 psf [7134 N/m 2 ] Bending Stiffness From Table 4A, a Rated Sturd-I-Floor 24 oc panel with stress applied parallel to the strength axis has a dry stiffness capacity (EI) of 330,000 lb-in. 2 /ft [3107 N•m 2 /m]. The deflection limit for live load is l/240. wl 3 4 Δ = 2,220 EI = 1.0 (48 – 3.5 + .625) 4 2,220 x 330,000 = 5.66 x 10 -3 in. w d = Δ all. = 48/240 Δ 5.66 x 10 -3 = 35 psf [1676 N/m 2 ] Bending strength controls (provides the lowest capacity) for this application. The bending strength capacity of 34 psf [1628 N/m 2 ] represents total load, from which dead load is subtracted to arrive at live load capacity. The bend- ing stiffness capacity of 35 psf [1676 N/m 2 ] represents live load only. Here, if dead load (panel weight plus roofing) is no more than 9 psf [431 N/m 2 ], the 25 psf [1200 N/m 2 ] snow load capacity is achieved. The tongue-and-groove edges provide required edge supports. 4.8.2. Example 2 – Panelized roof An oriented strand board (OSB) panel trademarked APA Structural I Rated Sheathing 32/16 is to be used in a pan- elized roof system over 2-in.-nominal [38 mm] framing members 24 in. [600 mm] on center. The long panel dimen- sion (strength axis) of the panel will be placed parallel to supports. Bending Strength From Table 4A, an OSB Rated Sheathing 32/16 panel with stress applied perpendicular to strength axis (long panel dimension parallel to sup- ports) has a bending strength capacity (F b S) equal to 165 lb-in./ft [61.2 N•m/ m]. This capacity is adjusted by a mul- tiplier of 1.5 for OSB Structural I, and by a duration-of-load factor (C D ) of 1.15 (see 4.5.1). This duration-of-load factor is normally associated with snow loads for roof structures. From 4.7, a two- span condition is assumed. w b = 96 F b S l 1 2 = 96 (165 x 1.5 x 1.15) 24 2 = 47 psf [2250 N/m 2 ] Shear Strength in the Plane From Table 4A, an OSB Rated Sheathing 32/16 panel with stress applied perpendicular to strength axis has shear strength in the plane (F s [lb/ Q]) of 165 lb/ft [2408 N/m]. This capac- ity is adjusted by a multiplier of 1.0 for OSB Structural I, and by a duration-of- load factor (C D ) of 1.15 (see 4.5.1). w s = 19.2 F s (lb/Q) l 2 = 19.2 (165 x 1.0 x 1.15) (24 – 1.5) = 162 psf [7757 N/m 2 ] © 2008 APA - The Engineered Wood Association 26 Bending Stiffness From Table 4A, an OSB Rated Sheathing 32/16 panel with stress applied perpen- dicular to strength axis has a dry stiff- ness capacity (EI) of 25,000 lb-in. 2 /ft [235 N•m 2 /m]. This capacity is adjusted by a multiplier of 1.6 for OSB Structural I. The deflection limit for live load is l/240. wl 3 4 Δ = 2,220 EI 1.0 (24 – 1.5 + .25) 4 = 2,220 x (25,000 x 1.6) = 3.017 x 10 -3 in. w d = Δ all. = 24/240 Δ 3.017 x 10 -3 = 33 psf [1580 N/m 2 ] 4.8.3. Example 3 – Floor A 5-ply plywood panel marked APA Rated Sturd-I-Floor 24 oc is to be used in a floor system over supports 24 in. [600 mm] on center. The panels will be placed with the long panel dimension (strength axis) perpendicular to sup- ports. Supports are 2-in.-nominal [38 mm] framing members. The capacity of the panel will be computed based on bending strength, shear strength in the plane and bending stiffness. Bending Strength From Table 4A, a 5-ply plywood Rated Sturd-I-Floor 24 oc panel with stress applied parallel to the strength axis (long panel dimension perpendicular to supports) has a bending strength capacity (F b S) of 770 lb-in./ft [285 N•m/m]. From 4.7, a three-span condi- tion is assumed. w b = 120 F b S = 120 x 770 l 1 2 24 2 = 160 psf [7661 N/m 2 ] Shear Strength in the Plane From Table 4A, a 5-ply plywood Rated Sturd-I-Floor 24 oc panel with stress applied parallel to the strength axis has shear strength in the plane (F s [lb/Q]) equal to 325 lb/ft [4743 N/m]. w s = 20 F s (lb/Q) l 2 = 20 x 325 (24 – 1.5) = 289 psf [13837 N/m 2 ] Bending Stiffness From Table 4A, a 5-ply plywood Rated Sturd-I-Floor 24 oc panel with stress applied parallel to the strength axis has a dry stiffness capacity (EI) of 330,000 lb-in. 2 /ft [3107 N•m 2 /m]. The deflec- tion limit for live load is l/360. wl 3 4 Δ = 1,743 EI 1.0 (24 – 1.5 + .25) 4 = 1,743 x (330,000 x 1.1) = 4.657 x 10 4 in. w d = Δ all. = 24/360 Δ 4.657 x 10 -4 = 143 psf [6847 N/m 2 ] While the above calculations would indicate that this Sturd-I-Floor con- struction has a live load capacity of 143 psf [6847 N/m 2 ] (limited by bend- ing stiffness), it is important to note that some structural panel applications are not controlled by uniform load. Residential floors, commonly designed for 40-psf [1900 N/m 2 ] live load, are a good example. The calculated allowable load is greatly in excess of the typi- cal design load. This excess does not mean that floor spans for Sturd-I-Floor can be increased, but only that there is considerable reserve strength and stiff- ness for uniform loads. Recommended maximum spans for wood structural panel floors are based on deflection under concentrated loads, how the floor “feels” to passing foot traffic, and other subjective factors which relate to user acceptance. Always check the maxi- mum floor and roof spans for wood structural panels before making a final selection for these applications. To assist in ascertaining the availability of a specific panel type, the following table has been developed by APA. TABLE 7 TYPICAL APA PANEL CONSTRUCTIONS (a) Span Pl ywood Rati ng 3- pl y 4- pl y 5- pl y (b) OSB APA Rated Sheathing 24/0 X X 24/16 X 32/16 X X X X 40/20 X X X X 48/24 X X X APA Rated Sturd-I-Floor 16 oc 20 oc X X X 24 oc X X X 32 oc X X 48 oc X X (a) Constructions listed may not be available in every area. Check with suppliers concerning avail- ability. (b) Applies to plywood with 5 or more layers. © 2008 APA - The Engineered Wood Association 27 5 . REFERENCES 1. Construction and Industrial Plywood, Voluntary Product Standard PS 1, U. S. Depart ment of Commerce, Washington, DC. 2. Performance Standard for Wood-Based Structural-Use Panels, Voluntary Product Standard PS 2, U.S. Department of Commerce, Washington, DC. 3. Performance Standards and Qualification Policy for Structural-Use Panels, PRP-108, APA – The Engineered Wood Association, Tacoma, WA. 4. Methods of Testing Structural Panels in Flexure, ASTM D 3043, American Society for Testing and Materials, Philadelphia, PA. 5. Test Method for Structural Panels in Tension, ASTM D 3500, American Society for Testing and Materials, Philadelphia, PA. 6. Test Method for Testing Structural Panels in Compression, ASTM D 3501, American Society for Testing and Materials, Philadelphia, PA. 7. Test Method for Structural Panels in Planar Shear (Rolling Shear), ASTM D 2718, American Society for Testing and Materials, Philadelphia, PA. 8. Test Method for Structural Panels in Shear Through-the-Thickness, ASTM D 2719, American Society for Testing and Materials, Philadelphia, PA. 9. Relation of Strength of Wood to Duration of Load, Report FPL R-1916, USDA Forest Products Laboratory, Madison, WI. 10. Plywood – Preservative Treatment by Pressure Process, AWPA Standard C9, Amer ican Wood-Preser vers’ Association, Granbury, TX. 11. Fire-Retardant-Treated Plywood, Technical Bulletin TB-201, APA – The Engineered Wood Association, Tacoma, WA. 12. Construction Sheathing, CAN/ CSA-O325.0, Canadian Standards Association, Toronto, ON, Canada. 13. National Design Specification for Wood Construction, American Forest & Paper Association, Washington, DC. 14. Standard Method for Evaluating Dowel Bearing Strength of Wood and Wood-Base Products, ASTM D 5764, American Society for Testing and Materials, Philadelphia, PA. © 2008 APA - The Engineered Wood Association We have field representatives in many major U.S. cities and in Canada who can help answer questions involving APA trademarked products. For additional assistance in specif ying engineered wood products, contact us: APA – THE ENGINEERED WOOD ASSOCIATION HEADQUARTERS 7011 So. 19th St. ■ Tacoma, Washington 98466 ■ (253) 565-6600 ■ Fax: (253) 565-7265 PRODUCT SUPPORT HELP DESK (253) 620-7400 ■ E-mail Address: [email protected] Form No. D510C/Revised February 2008/0300