APA Engineered Wodd Handbooks Episode 8 ppt

6.1 CHAPTER SIX STRUCTURAL COMPOSITE LUMBER Zhaozhen Bao, PhD Associate Scientist, TSD 6.1 INTRODUCTION Structural composite lumber (SCL) is a generic engineered wood structural lumber product family that includes laminated veneer lumber (LVL), parallel strand lumber (PSL), laminated strand lumber (LSL), oriented strand lumber (OSL), and other wood composite lumber products with similar engineering and configuration features. LVL was first produced in the early 1970s and since then has been commercially available in the United States. PSL was introduced to market in the 1980s. SCL products are used in the same structural applications as sawn lumber and timber. 6.1.1 Laminated Veneer Lumber Laminated veneer lumber (LVL) was the earliest type of SCL product commercially manufactured for the marketplace. It is now the most widely used structural composite lumber product in the residential housing market. LVL is produced by bonding layers of wood veneers in a large billet under proper temperature and pressure. Typically, LVL is produced in 4 ft wide billets with different lengths, and the billet is then sawn to different dimensions to meet the needs of the final applications. There are no limitations on wood species for LVL. Basically, any species that are used in manufacturing plywood can be used to produce LVL. The most common species for LVL are Douglas fir, southern pine, and SPF (spruce-pine-fir). Generally, LVL is used as headers and beams, chords for trusses, ridge beams in mobile homes, flanges in prefabricated I-joists, and scaffold planks. It is also used as columns, shear wall framing studs, and even structural members in upholstered furniture frames. Description and General Features. LVL is a glued engineered wood composite lumber product manufactured by laminating wood veneers using exterior type adhesives (Fig. 6.1). Generally, the grain directions of wood veneers in LVL are all 6.2 CHAPTER SIX FIGURE 6.1 Laminated veneer lumber of different depths; picture (photo) showing a shot of LVL. parallel to the length direction of the billet, although LVL products with cross lamination are sometimes seen for meeting specific structural needs. Similar to the lay-up strategy in glued-laminated timber (glulam), veneers with higher grades are placed on the faces while lower-grade veneers are in the core. This specific lay-up configuration of the wood veneers effectively utilizes materials’ strength and im- proves the strength and stiffness of the manufactured products in a desired way. Natural defects of wood such as knots, knotholes, and splits can be closely controlled, and their individual effects are virtually eliminated in LVL. Desired width, depth, and length can be technically achieved by various manufacturing techniques, including side jointing and end jointing (butt, scarf, and finger jointing). Since the grade and quality of each individual layer of veneers can be closely controlled, the variations in product properties are lowered as compared to sawn lumber products, and therefore the properties and performance of final LVL products can be more confidently predicted than sawn lumber. LVL has improved mechanical properties and dimensional stability. It can offer a broader range in product width, depth, and length than lumber. Various wood species, even those considered low-grade or previously underutilized species, can be used to manufacture LVL. Briefs on Manufacturing Process Veneer. Veneers for manufacturing LVL are made in the same way as veneers for plywood manufacturing. The commonly used veneer thicknesses are 1 ⁄ 10 – 1 ⁄ 8 in. Typically veneer thicknesses in LVL manufacturing do not exceed 1 ⁄ 4 in. Similar to plywood manufacturing, fresh-peeled veneers are mechanically dried. Veneers are then trimmed, repaired, and sorted according to the number and sizes of defects such as knots, knotholes, and splits. In order to ensure the desired engineering STRUCTURAL COMPOSITE LUMBER 6.3 properties of the finished LVL product, individual veneer is passed though a veneer grade tester for measuring moisture content, density, and E values. Stress wave propagation time, also called ultrasonic propagation time (UPT), is also used to sort veneers. UPT outputs correspond to veneer grades in accordance to plant man- uals. According to the output UPT values, veneers are graded and sorted for LVL lay-ups. Other alternative grading systems may also be used at the manufacturers option. Lay-up. Scarf and finger jointing techniques are used to end-joint pieces of veneer sheets to a desired length. End joints between layers are staggered along the length to minimize strength-reducing effects end jointing may have. In some manufacturing processes, the ends of veneer sheets are overlapped in lieu of end- jointing. Exterior-type adhesives, such as phenol-formaldehyde (PF) resorcinol base adhesives, are used in bonding the veneers together. Adhesives are spread onto the veneer surfaces and mats are laid according to the predetermined lay-up pattern. The mat sheets are then ready to be pressed in a hot press. Pressing. The LVL mat sheets are sent into either a stationary or staging hot press or a continuous hot press. During hot pressing, the thermoset type adhesive is cured under heat and pressure, permanently bonding the plies of veneers together to form billets. The LVL billets are then ripped to specific widths (depths) and cut to given lengths. Figure 6.2 shows a typical LVL manufacturing operation. 6.1.2 Parallel Strand Lumber Parallel strand lumber (PSL) is manufactured by glue-bonding wood strands to form a condensed billet in such a way that the wood fiber (grain) direction of the strands is primarily oriented parallel to the length of the member. The thickness (least dimension) of the strands usually is less than 0.25 in., and the average length of strands is about 150 times the thickness of the strands. One source of strands used in PSL can be clipped veneers from the process wastes in plywood or LVL plants, or full-size veneer sheets such as used in plywood and LVL manufacturing can be used. Presently, PSL is made primarily from Douglas fir, western hemlock, southern pine, and yellow poplar, although there are no restrictions on species. PSL is commonly used in structures as headers and beams, as well as columns and studs. Description and General Features. PSL has greater strength properties than sawn lumber. Its strength is enhanced by increasing the amount of densification of the pressed billet rather than obtained through the optimized use of veneer species and grades in lay-up processing, as for LVL. Usually, a PSL billet is made in a cross section of 11 ϫ 19 inches. Its larger cross section allows the use of PSL as a direct substitution for structural timber products without secondary gluing. Due to its high degree of strand alignments and increased densification, PSL possesses excellent strength and stiffness in the primary axis. On the minus side, however, PSL is heavier than the same-sized sawn or glue-laminated timber (glulam). Also, its adhesive is more abrasive to saws and drills. Briefs on Manufacturing Process. The dimensions of veneers (strands) used in PSL are about 1 ⁄ 8 in. thick by 3 ⁄ 4 in. wide by 24 in. long. The strands are coated with exterior type adhesive, commonly phenol-resorcinol formaldehyde resin. The strands are all oriented parallel to the length of the billet. Heat used for curing the adhesive is generated by microwave in the hot press. This makes it possible to cure the adhesive from the inside out. The cross section of PSL billet, therefore, can be 6.4 CHAPTER SIX LVL Veneer Dryer Ultrosonic grading Adhesive Trimming Cutting Grading Shipping Hot pressing FIGURE 6.2 Typical manufacturing process of LVL using ultrasonic grading. made up to 11 ϫ 19 in., which is greater than that for LVL, where heat is typically transferred from the outside to the inside of the billet during the hot pressing. The continuous pressing operation allows a higher degree of densification to be achieved. Although there is no length limitation in the continuous pressing, typical lengths of PSL billets are up to 60 ft and are actually limited by handling restrictions. Billets are then resized to desired dimensions. If needed, larger cross-section dimensions can be achieved by secondary operations. 6.1.3 Laminated Strand Lumber and Oriented Strand Lumber Laminated strand lumber (LSL) is an extension of the technology used to manufacture oriented strand board (OSB). Wood strands used in LSL are about 12 in. long, which is longer than the strands normally used in OSB (which are about 3– 4 in. long). Among those SCL products, LSL perhaps is the most efficient in util- izing wood resources. It has no restrictions on raw materials. Small logs and crooked logs of many species, including aspen, yellow poplar, and other underutilized, fast-growing species, can be used in manufacturing LSL. 1 A higher degree of strand orientation in LSL is required than in OSB, and greater pressing pressures are needed in order to obtain increased densification. Oriented strand lumber (OSL) is another type of laminated strand lumber (LSL) product and has a similar manufacturing process to that for LSL. The primary difference between them is that the length of strand used in OSL is shorter (up to STRUCTURAL COMPOSITE LUMBER 6.5 6 in.) than that used in LSL (approximately 12 in.). OSL has somewhat lower strength and stiffness values than LSL. Description and General Features. Generally LSL has somewhat lower strength and stiffness properties than LVL and PSL. The lay-up operation in LSL mat forming processing resembles OSB mat forming, improving transverse strength and lim- iting cupping potential. Waterproof adhesives are used in LSL manufacturing. The unique steam injection pressing process achieves curing of the sprayed adhesive on strands and densification of the LSL mat, thus resulting in enhanced strength properties of the final product. LSL demonstrates excellent fastener-holding strength and mechanical connector performance. LSL in general is less dimensionally stable than LVL and PSL due to its greater densification. Since more wood substances are compacted to form the relatively dense LSL, it exhibits more thickness swell as compared to LVL and PSL as its moisture content changes. Briefs on Manufacturing Process. Wood strands are first produced by a strander, and then the strands are screened out to eliminate unwanted sizes. The green strands are driven through a drum-type dryer. Exterior-type adhesives, wax, and other ad- ditives are blended in a blender and the liquid mixture is sprayed onto the strand surfaces as they tumble through the inside of a rotating drum. Strands are oriented through a forming machine with multiple forming heads. The mats are sent into a hot press. Curing of the resins and densification of the mat are achieved under proper temperature and pressures during hot pressing. Billets are then trimmed to the required sizes. With this technology, billets 8 ft wide and up to 5 in. thick and 48 ft long can be poduced. Billets are finally cut and ripped to desired dimensions for different end uses. Figure 6.3a and b shows a typical manufacturing process of PSL and LSL respectively. 6.2 GROWTH OF INDUSTRY It was reported in the 1940s that an LVL-type product was developed for high strength parts for aircraft structures using Sitka spruce veneer. 2 This was probably the earliest example of LVL. In the late 1960s, the U.S. and Canadian governments searched for methods to increase the raw material efficiency of lumber manufacturing since the sawn lumber industry conventionally renders half or more of logs into sawdust, wood slabs, and other types of residues. Technology of parallel lamination of rotary-peeled veneers was developed and the so-produced laminated veneer lumber product was termed LVL. LVL has improved strength properties, allows more economical and efficient material utilization, and utilizes affordable phenol- formaldehyde resins, and all of these factors combined to encourage manufacturers to enter into this industry. Laminated veneer lumber (LVL) was introduced to the building industry by Trus Joist Corporation in 1970 3 and has been available since 1971. 4 Parallel strand lumber (PSL) was developed and patented by MacMillan Bloedel Ltd. around 1978 and became commercially available in the early 1990s. 3 Structural composite lumber is a growing segment of the engineered wood industry and is used extensively as a replacement for sawn lumber products. More production lines of LVL have been added to meet the increasing demand on LVL as headers, beams, and partic- 6.6 CHAPTER SIX Veneer Dryer Clipper Adhesive application Assembly Pressing & Curing Sanding Trimming & Sizing Ripping Finished product PSL Defect removal FIGURE 6.3a PSL manufacturing process. ularly the flange materials of I-joists. According to APA—The Engineered Wood Association, the LVL production estimates (United States and Canada) for the year of 2003 will be 84.0 ϫ 10 6 ft 3 , as compared to a total production of 31.5 ϫ 10 6 ft 3 in 1996. Table 6.1 lists the LVL production estimates for United States and Canada from 1996–2003. One of the newest members of the SCL family is LSL which was introduced into the marketplace by the Trus Joist Corporation in the 1990s. 6.3 STANDARDS 6.3.1 Standards ASTM D5456, Standard Specification for Evaluation of Structural Composite Lum- ber Products, 5 provides guidelines for the evaluation of mechanical properties, physical properties, and quality of structural composite lumber products. Since ASTM D5456 is not a product standard for the SCL industry, individual manufacturers of SCL generally have their own proprietary manufacturing product standards that govern the everyday production practice for their products. The common grades and their design stresses for SCL, particularly for LVL, are dictated by the market, and the major LVL products have similar or comparable design values. STRUCTURAL COMPOSITE LUMBER 6.7 LSL Logs Metal detector Strander Debarker Dryers Cutting Sander Bundle cutter Shipped Forming Wax Press Resin Blenders Dry bins Short strand eliminator Short strand eliminator Green bins Finished product FIGURE 6.3b LSL manufacturing process. TABLE 6.1 LVL Production Estimates—United States and Canada LVL production estimates—U.S. and Canada (million cubic feet) 1996 1997 1998 1999 2000 2001 2002 2003 United States 41.0 46.2 50.5 61.5 68.3 75.1 Canada a 1.7 3.8 7.5 8.5 8.7 8.9 Total North America 31.5 a 37.7 a 42.7 50.0 58.0 70.0 77.0 84.0 a 1996–1997 only combined statistics available. 6.8 CHAPTER SIX 6.3.2 Code Recognition Under the current building code jurisdictions, SCL manufacturers are required to gain code recognition through an evaluation process provided by code agencies such as ICBO (International Conference of Building Officials) Evaluation Service or the National Evaluation Service (NES). ICBO Evaluation Services AC47, 6 Ac- ceptance Criteria for Structural Composite Lumber, provides guidelines on imple- menting performance features of the Uniform Building Code (UBC). Although ASTM D5456 and ICBO AC47 provide guidance for developing proprietary design values, no standard performance levels or grades are defined in the documents. 6.3.3 Industry LVL Performance Standard Several LVL manufacturers felt that a performance standard covering major LVL products was needed to provide a common ground for performance requirements and acceptance criteria of existing products. Such a standard was also deemed important to provide an industry-wide uniform quality control and quality assurance system for the products. In order to meet the needs for such an industry-wide LVL standard, APA and its members have developed an LVL standard—APA PRL-501, Performance Standard for APA EWS Laminated Veneer Lumber. 7 The standard ad- dresses grading, materials, tolerances, performance criteria, quality assurance requirements, and trademarking for LVL products. This standard has been approved by each of the three model code agencies and is intended to serve as an industry- wide LVL product standard and provide a direct avenue for the code approval and recognition for LVL products manufactured under this standard. The adoption of this standard is also intended to simplify the design and specification of LVL products. 6.3.4 Grades and Grading System As with the machine stress-rated (MSR) grading system used by the lumber industry, SCL products are identified according to their assigned stress classes. Stress classes indicate the allowable designated modulus of elasticity, E, and design bending stress, F b . The most commonly used LVL grades range from 1.5E (an allowable design E ϭ 1.5 ϫ 10 6 psi) to 2.1E (an allowable design E ϭ 2.1 ϫ 10 6 psi). In general, a stress class consists of two parts separated by a hyphen (‘‘-’’). To the left of the hyphen is the designated E value while to the right is the design bending stress (F b ), both of which are in the units of pounds per square inch (psi). For instance, a grade of 1.5E-2250F signifies LVL with an allowable E of 1.5 ϫ 10 6 psi and F b of 2250 psi. Table 6.2 is excerpted from APA PRL-501. It lists the major design properties for APA EWS performance rated LVL. Other grades of LVL products can be manufactured as special orders to meet special needs. 6.4 PHYSICAL PROPERTIES 6.4.1 Specific Gravity and Moisture Content Specific gravity of SCL products is an important indicator of various physical and mechanical properties. As a wood-based laminated layered material, SCL’s density STRUCTURAL COMPOSITE LUMBER 6.9 TABLE 6.2 Design Properties for APA EWS Performance Rated LVL a APA EWS E b F b c F t d F c ࿣ e F v f F c Ќ g LVL stress 10 6 psi psi psi psi Edgewise Edgewise classes psi psi 1.5E-2250F 1.5 2250 1500 1950 220 575 1.8E-2600F 1.8 2600 1700 2400 285 700 1.9E-2600F 1.9 2600 1700 2550 285 700 2.0E-2900F 2.0 2900 1900 2750 285 750 2.1E-3100F 2.1 3100 2200 3000 285 850 a The tabulated values are design values for normal duration of load. All values, except E and F c Ќ , are permitted to be adjusted for other load durations as permitted by the code. The design stresses are limited to conditions in which the maximum moisture content is less than 16 percent. b Bending modulus of elasticity (E), which is applicable in either edgewise or flatwise applications, includes shear deflections. For calculating uniform load and center-point load deflections of the LVL in a simple-span application, use Eqs. (1) and (2). 4 5 ␻ ᐉ Uniform load: ␦ ϭ (1) 384EI 3 Pᐉ Center-point load: ␦ ϭ (2) 48EI where ␦ ϭ calculated deflection (in.) ␻ ϭ uniform load (lbf/in.) P ϭ concentrated load (lbf) ᐉ ϭ design span (in.) I ϭ moment of inertia of the LVL (in. 4 ) c Allowable bending stress (F b ) is applicable in either edgewise or flatwise applications. For depths of 3 1 ⁄ 2 in. or deeper when loaded edgewise, the tabulated F b value shall be modified by (12 / d ) 1/8 , where d is the actual depth (in.). For depths less than 3 1 ⁄ 2 in. when loaded edgewise, use the adjusted F b for 3 1 ⁄ 2 in. No adjustment on F b is required for flatwise applications. d Axial tension (F t ) of the LVL is based on a gage length of 4 ft. For specimens longer than 4 ft, the tabulated F t value shall be adjusted by (4/L) 1/8 , where L is the actual length (ft). e Compression parallel to grain (F c ࿣ ) of the LVL. f Allowable shear stress (F v ) of the LVL when loaded edgewise. g Allowable compressive stress perpendicular to grain (F c Ќ ) of the LVL when loaded edgewise. is affected greatly by the wood species from which it is made. However, due to the variables of species being used, the significant amounts of adhesives being added, and the densification achieved under the heat and pressure during hot pressing, the density of SCL products may be different from that of the original wood species. Since virtually all kinds of available wood species can be used to manufacture SCL products, their density falls in a wide range of 20–42 lb/ft 3 (approximately 0.33– 0.68 specific gravity, respectively). The equivalent specific gravity of an SCL product must be established during the development of mechanical properties because this will also affect fastener performance (see below under Equivalent Specific Gravity). The moisture content (MC) of SCL at time of production will be around 8– 10%. Moisture content of SCL starts changing as the conditions of the ambient air change. As the changes in moisture content in wood change the weight and the volume of the member, they can change the specific gravity of the member. In general, the change is not noticeable since the moisture changes of SCL are generally small under a protected environment. 6.10 CHAPTER SIX 6.4.2 Dimensional Stability Wood is a hygroscopic material, as are SCL products, since they inevitably inherit this feature from the original wood. However, the dimensional changes in SCL are usually less than the original wood from which it is produced. This is attributed to the drying of individual veneers/strands and the subsequent hot pressing and drying, plus the addition of the exterior-type adhesives. Since SCL products are recommended for use in a protected dry end-use con- dition where moisture content is below 16%, little change in moisture content will occur in such protected service conditions. The linear expansion and shrinkage of SCL under the typical in-service moisture changes will be minimal and generally not noticeable. 6.4.3 Durability Like any wood-based product, SCL products may be subjected to wood degradation or deterioration during use associated with attacks of fungi and insect, temperature and UV, and, most commonly, water. However, since SCL products are recommended for dry-use conditions they are relatively unaffected by those attacks. Also, it is generally recognized that SCL products have better durability than untreated wood members due to the relatively thorough drying process of wood elements, addition of the exterior-type adhesives, and hot pressing. Thus, SCL products can be expected to have a prolonged service life without significant or noticeable degradation in strength when properly installed and maintained. 6.5 MECHANICAL PROPERTIES SCL products are primarily loaded in either of the two major directions: joist (edgewise) or plank (flatwise) orientation. Load applied to members can be from any of the three directions: (1) parallel to grain, (2) perpendicular to grain and parallel to glue-plane, or (3) perpendicular to grain and perpendicular to glue-plane. In order to define the three axes that determine the dimensions of SCL, a drawing is provided in Fig. 6.4. The three axes will be referenced throughout the following text. 6.5.1 Bending Properties Bending probably is the most common loading situation for most SCL members. Examples of structural members used as bending members are joists, headers, beams, and floor girders. Bending properties of modulus of rupture (MOR) and modulus of elasticity (MOE) are the two most frequently used properties in as- sessing the strength and stiffness of a material. Edgewise and Flatwise Bending. SCL members can be used as headers and beams, which are conventionally loaded on edge. They are also used as scaffold planks and deck boards, which are primarily loaded flatwise. It is typically observed that flatwise SCL bending specimens yield higher bending strength (MOR) and stiffness (MOE) values than the specimens tested on edge. The explanation is the so-called I-beam effect. Here, the two outer surface layers (surface layers usually consist of several individual plies of veneer) of SCL are of [...]... 1 388 189 1 2430 10 18 1549 2046 2 485 1 089 1633 2046 2 485 5 .8 7.9 10.1 4.2 6.4 8. 5 10.3 4.5 6 .8 8.5 10.3 504 3.2 309 415 2.9 237 3 48 2.7 186 296 2.4 1 48 199 1 .8 120 161 1.5 766 4.9 1045 1343 6.6 8. 5 88 6 4.6 12 08 1552 6.3 8. 1 582 3.0 88 6 4.6 12 08 1552 6.3 8. 1 632 4.4 86 2 6.0 11 08 7.7 731 4.2 997 5.7 1 281 7.3 997 5.7 1 281 7.3 723 5.5 930 7.1 613 3 .8 836 5.2 1075 6.7 613 3 .8 836 5.2 1075 6.7 451 3.7 292 388 ... 9.0 83 9 3.5 1277 1740 2236 5.3 7.2 9.3 83 9 3.5 1277 1740 2236 5.3 7.2 9.3 937 3.9 1425 188 3 2 286 1002 1503 188 3 2 286 5.9 7 .8 9.5 4.2 6.2 7 .8 9.5 463 2.9 309 382 2.7 237 320 2.4 186 272 2.2 1 48 199 1 .8 120 161 1.5 705 4.5 961 6.1 1235 7 .8 815 4.2 1111 14 28 5 .8 7.4 536 2 .8 815 4.2 1111 14 28 5 .8 7.4 1240 1594 6.4 8. 3 793 5.5 1020 7.1 673 3 .8 917 5.2 1179 6.7 673 3 .8 917 5.2 1179 6.7 751 4.3 1024 1316 5 .8. .. 744 285 491 669 86 0 301 491 669 86 0 3 18 5 48 747 960 334 586 799 1027 1 .8 3.2 4.4 5.7 1 .8 3.1 4.2 5.4 1.9 3.1 4.2 5.4 2.0 3.4 4.7 6.0 2.1 3.7 5.0 6.4 123 242 399 5 98 1 48 291 480 7 18 156 3 08 507 165 324 534 799 173 341 561 83 9 186 361 492 633 224 417 569 732 236 417 569 732 249 466 636 81 7 262 499 680 87 4 1.5 3.0 4.1 5.2 1.5 2 .8 3 .8 4.9 1.6 2 .8 3 .8 4.9 1.7 3.1 4.3 5.5 1 .8 3.4 4.6 5.9 98 193 319 4 78 117... 8 14 1.8E-2600F 16 1 9 ⁄2 7 11 8 14 1.9E-2600F 16 1 9 ⁄2 7 11 8 14 2.0E-2900F 16 1 9 ⁄2 7 11 8 14 2.1E-3100F 16 1 9 ⁄2 117 8 14 16 1376 188 9 2443 3072 1626 2449 3166 3 981 1626 2449 3166 3 981 1 783 2449 3166 3 981 1 783 2449 3166 3 981 5.2 7.2 9.3 11.7 5.1 7.6 9.9 12.4 5.1 7.6 9.9 12.4 5.6 7.6 9.9 12.4 5.6 7.6 9.9 12.4 789 4.0 1201 15 78 1917 6.1 8. 0 9.7 912 3 .8 1 388 189 1 2430 5 .8 7.9 10.1 912 3 .8 1 388 ... 1959 2533 3 185 1301 1959 2533 3 185 1426 1959 2533 3 185 1426 1959 2533 3 185 4.2 5 .8 7.4 9.4 4.1 6.1 7.9 9.9 4.1 6.1 7.9 9.9 4.4 6.1 7.9 9.9 4.4 6.1 7.9 9.9 539 647 683 720 756 632 961 1263 1534 730 1110 1513 1944 730 1110 1513 1944 81 5 1239 1637 1 988 87 1 1307 1637 1 988 3.2 4.9 6.4 7 .8 3.0 4.6 6.3 8. 1 3.0 4.6 6.3 8. 1 3.4 5.1 6 .8 8.3 3.6 5.4 6 .8 8.3 274 5 38 329 646 3 48 682 366 719 385 755 403 613 83 6 1074... 989 5.1 13 48 1732 7.0 81 6 4.7 1113 1430 6.4 8. 2 685 4.3 934 5 .8 1200 7.5 583 3.9 390 501 3.6 317 436 3.4 794 5.4 1021 6.9 684 5.0 88 0 6.4 595 4.6 765 6.0 695 3.6 434 574 3.3 334 481 3.0 262 409 2 .8 209 279 2.0 169 226 1 .8 10 58 1441 180 5 5.5 7.5 9.4 87 3 5.0 1190 1529 6 .8 8.7 733 4.6 999 6.2 1 284 8. 0 623 4.2 410 536 3.9 333 467 3.6 85 0 5.7 1093 7.4 732 5.3 941 6 .8 636 5.0 81 8 6.4 6.32 TABLE 6 .8 Allowable... 4.6 5.9 98 193 319 4 78 117 232 383 574 124 245 405 606 131 259 426 6 38 1 38 272 4 48 670 1 48 292 424 545 1 78 351 490 630 188 359 490 630 1 98 390 547 704 209 410 585 753 1.5 2.6 3 .8 4 .8 1.5 2.6 3.6 4.6 1.5 2.6 3.6 4.6 1.5 2 .8 4.0 5.1 1.5 3.0 4.3 5.5 79 156 2 58 387 95 188 310 465 100 199 3 28 491 106 209 345 5 18 111 220 363 544 120 237 3 68 474 144 284 426 5 48 152 300 426 5 48 161 317 476 612 169 333 509 655... 711 4 .8 915 6.2 522 3.5 711 4 .8 915 6.2 530 4.7 681 6.1 612 4.5 788 5.7 788 5.7 592 5.6 533 4.1 685 5.3 449 3.3 300 390 3.0 612 4.5 460 4.4 522 3.5 351 449 3.3 284 390 3.0 480 2.7 301 403 2.5 236 342 2.3 188 295 2.1 152 205 1.6 731 4.2 530 4.0 582 3.0 372 480 2.7 285 403 2.5 224 342 2.3 1 78 295 2.1 144 194 1.5 533 4.1 685 5.3 650 3.4 413 536 3.1 3 18 450 2 .8 249 383 2.6 1 98 329 2.4 161 215 1.7 989 5.1... 11 8 1 28 194 2.0 106 161 1.7 88 135 1.5 75 114 1.5 63 97 1.5 46 72 1.5 35 54 1.5 26 42 1.5 1.8E-2600F 14 16 212 320 3.3 176 266 2.9 147 223 2.6 124 189 2.3 106 161 2.0 78 120 1.7 59 91 1.5 45 70 1.5 27 44 1.5 3 18 416 4.2 264 3 68 4.0 221 327 3.7 187 284 3.4 160 243 3.1 1 18 181 2.5 90 1 38 2.1 69 107 1 .8 43 68 1.5 1 9 ⁄2 77 1 18 1.5 64 98 1.5 53 82 1.5 45 69 1.5 38 58 1.5 27 43 1.5 20 32 1.5 7 11 8 154... 1.5 24 34 1.5 7 11 8 233 315 2.6 194 2 78 2.5 162 2 48 2.3 137 185 1 .8 117 1 58 1.6 87 117 1.5 66 89 1.5 51 69 1.5 31 43 1.5 1.9E-2600F 14 16 430 3.6 320 380 3.4 269 3 38 3.2 227 303 3.0 194 273 2 .8 144 194 2.2 110 1 48 1.9 85 115 1.6 53 73 1.5 553 4.6 489 4.3 435 4.1 390 3 .8 292 351 3.6 2 18 289 3.3 166 241 3.0 129 174 2.4 82 111 1.7 1 9 ⁄2 125 1 68 1.5 103 139 1.5 86 117 1.5 73 99 1.5 62 84 1.5 46 62 1.5 . feet) 1996 1997 19 98 1999 2000 2001 2002 2003 United States 41.0 46.2 50.5 61.5 68. 3 75.1 Canada a 1.7 3 .8 7.5 8. 5 8. 7 8. 9 Total North America 31.5 a 37.7 a 42.7 50.0 58. 0 70.0 77.0 84 .0 a 1996–1997. 1500 1950 220 575 1.8E-2600F 1 .8 2600 1700 2400 285 700 1.9E-2600F 1.9 2600 1700 2550 285 700 2.0E-2900F 2.0 2900 1900 2750 285 750 2.1E-3100F 2.1 3100 2200 3000 285 85 0 a The tabulated values are. meet the needs for such an industry-wide LVL standard, APA and its members have developed an LVL standard APA PRL-501, Performance Standard for APA EWS Laminated Veneer Lumber. 7 The standard ad- dresses

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