The listed reference design values are for visually graded dimension lumber 2-4 inches thick

Transcription

1 The listed reference design values are for visually graded dimension lumber 2-4 inches thick Species/ grade Bending Tension parallel Design values in pounds per square inch (psi) Shear Compression Compression parallel perpendicular parallel to grain Modulus of Elasticity Specific Gravity F b F T F V F C F C E E min G Douglas Fir-Larch 1,500 1, ,700 1,900, ,000 No. 1 & Btr 1, ,550 1,800, ,000 No ,500 1,700, ,000 No ,350 1,600, ,000 No ,400, , Stud ,400, ,000 1, ,650 1,500,00 550,000 Standard 2-4 wide ,400 1,400,00 510,000 Utility ,300, ,000 Douglas Fir-Larch (North) 1, ,900 1,900, ,000 No. 1 & Btr 1, ,800 1,800, ,000 No. 1 / No ,400 1,600, ,000 No ,400, ,000 Stud ,400, , ,800 1,500, ,000 Standard 2-4 wide ,400, ,000 Utility ,300, ,000 Douglas Fir-Larch (South) 1, ,600 1,400, ,000 No ,450 1,300, ,000 No ,350 1,200, ,000 No ,100, ,000 Stud ,100, , ,650 1,200, ,000 Standard 2-4 wide ,400 1,100, ,000 Utility ,000, ,000 Hem-Fir 1, ,500 1,600, ,000 No. 1 & Btr 1, ,350 1,500, ,000 No ,350 1,500, ,000 No ,300 1,300, ,000 No ,200, , Stud ,200, , ,550 1,300, ,000 Standard 2-4 wide ,300 1,200, ,000 Utility ,100, ,000 Hem-Fir (North) F b F T F V F C F C E E min G 1, ,700 1,700, ,000 No. 1 & Btr 1, ,550 1,700, ,000 No. 1 / No. 2 1, ,450 1,600, ,000 No ,400, ,000 Stud ,400, , , ,750 1,500, ,000 Standard 2-4 wide ,500 1,400, ,000 Utility ,300, ,000 See also NDS Supplement and/or Western Wood Product Use Manual or CWC US Span Book for Major Lumber Species TTT 1 Section 05 ver Truss Materials Design Values 1

2 The listed reference design values are for visually graded dimension lumber 2-4 inches thick Species/ grade Bending Tension parallel Design values in pounds per square inch (psi) Shear Compression Compression parallel perpendicular parallel to grain Modulus of Elasticity Specific Gravity F b F T F V F C F C E E min G Spruce-Pine-Fir 1, ,400 1,500, ,000 No. 1 / No ,150 1,400, ,000 No ,200, ,000 Stud ,200, ,000 1, ,400 1,300, ,000 Standard 2-4 wide ,150 1,200, ,000 Utility ,100, ,000 Spruce-Pine-Fir (South) 1, ,200 1,300, ,000 No ,050 1,200, ,000 No ,000 1,100, ,000 No ,000, ,000 Stud ,000, , ,200 1,000, ,000 Standard 2-4 wide , , ,000 Utility , ,000 See also NDS Supplement and/or Western Wood Product Use Manual or CWC US Span Book for Major Lumber Species Adjustment Factors (AWC National Design Standard (NDS) Table 4A for most US & Canadian species except SYP): Duration of Load C D Tablulated design values are for normal load duration. Repetitive Member C r Bending design values (F b) for dimension lumber 2 to 4 thick shall be multiplied by the repetitive member factor, C r = 1.15, when such members are used as joists, truss chords, rafters, studs, planks, decking, or similar members which are in contact or spaced not more than 24 on center, are not less than 3 in number and are joined by floor, roof, or other load distributing elements adequate to support the design load Wet Service C M The design values in the tables above are for dimension lumber is used where moisture content will exceed 19% (dry service conditions). When dimension lumber is used where moisture content will exceed 19% for an extended time period, design values shall be multiplied by the appropriate wet service factors F b F t F v F C F C E & E min when (F b)(c V) 1,150 psi, C M = when (F C) 750 psi, C M = 1.0 C F Tabulated bending, tension, and compression parallel design values for dimension lumber 2 to 4 thick shall be multiplied by the following size factors: Grades Select Structural No. 1 & Btr No. 1 & No. 2 No F b F t F C Width (depth) Thickness (breadth) 2, 3, & & wider Flat Use C fu Bending design values adjusted by size factors are based on edgewise use (load applied to narrow face). When dimension lumber is used flatwise (load applied to wide face), the bending design value (F b) shall be multiplied by the following flat use factors Width (depth) Thickness (breadth) 2 & & & wider TTT 1 Section 05 ver Truss Materials Design Values 2

3 The listed reference design values are for visually graded dimension lumber 2-4 inches thick Species/ grade Bending Tension parallel Design values in pounds per square inch (psi) Shear Compression Compression parallel perpendicular parallel to grain Modulus of Elasticity Specific Gravity F b F T F V F C F C E E min G Southern Pine 2,700 1, ,050 1,900, ,000 2,350 1, ,900 1,800, ,000 Non- 2,050 1, ,800 1,600, ,000 No. 1 Dense 1,650 1, ,750 1,800, ,000 No. 1 1,500 1, ,650 1,600, , wide No. 1 Non-Dense 1, ,550 1,400, ,000 No. 2 Dense 1, ,500 1,600, ,000 No. 2 1, ,450 1,400, ,000 No. 2 Non-Dense 1, ,450 1,300, ,000 No. 3 &Stud ,300, , ,600 1,400, ,000 Standard 4 wide ,300 1,200, ,000 Utility ,200, ,000 2,400 1, ,900 1,900, ,000 2,100 1, ,800 1,800, ,000 Non- 1,850 1, ,700 1,600, ,000 No. 1 Dense 1,500 1, ,650 1,800, ,000 No. 1 1, ,550 1,600, , wide No. 1 Non-Dense 1, ,450 1,400, ,000 No. 2 Dense 1, ,450 1,600, ,000 No. 2 1, ,400 1,400, ,000 No. 2 Non-Dense ,350 1,300, ,000 No. 3 &Stud ,300, ,000 2,200 1, ,850 1,900, ,000 1,950 1, ,700 1,800, ,000 Non- 1,700 1, ,650 1,600, ,000 No. 1 Dense 1, ,600 1,800, ,000 No. 1 1, ,500 1,600, ,000 8 wide No. 1 Non-Dense 1, ,400 1,400, ,000 No. 2 Dense ,400 1,600, ,000 No ,350 1,400, ,000 No. 2 Non-Dense ,300 1,300, ,000 No. 3 &Stud ,300, ,000 1,950 1, ,800 1,900, ,000 1,700 1, ,650 1,800, ,000 Non- 1,500 1, ,600 1,600, ,000 No. 1 Dense 1, ,550 1,800, ,000 No. 1 1, ,450 1,600, , wide No. 1 Non-Dense ,400 1,400, ,000 No. 2 Dense ,350 1,600, ,000 No ,300 1,400, ,000 No. 2 Non-Dense ,250 1,300, ,000 No. 3 &Stud ,300, ,000 1,800 1, ,750 1,900, ,000 1,600 1, ,650 1,800, ,000 Non- 1, ,550 1,600, ,000 No. 1 Dense 1, ,500 1,800, ,000 No. 1 1, ,400 1,600, , wide No. 1 Non-Dense ,350 1,400, ,000 No. 2 Dense ,300 1,600, ,000 No ,250 1,400, ,000 No. 2 Non-Dense ,250 1,300, ,000 No. 3 &Stud ,300, ,000 See also NDS Supplement and/or Southern Pine Use Guide. The values above reflect adjusted SYP values effective June 1, TTT 1 Section 05 ver Truss Materials Design Values 3

4 Adjustment Factors (AWC National Design Standard (NDS) Table 4B for US SYP): Duration of Load C D Tablulated design values are for normal load duration. Repetitive Member C r Bending design values (F b) for dimension lumber 2 to 4 thick shall be multiplied by the repetitive member factor, C r = 1.15, when such members are used as joists, truss chords, rafters, studs, planks, decking, or similar members which are in contact or spaced not more than 24 on center, are not less than 3 in number and are joined by floor, roof, or other load distributing elements adequate to support the design load Wet Service C M The design values in the tables above are for dimension lumber is used where moisture content will exceed 19% (dry service conditions).when dimension lumber is used where moisture content will exceed 19% for an extended time period, design values shall be multiplied by the appropriate wet service factors F b F t F v F C F C E & E min when (F b)(c V) 1,150 psi, C M = when (F C) 750 psi, C M = 1.0 C F Appropriate size adjustment factors have already been incorporated in the design values for most thickness of Southern Pine. See NDS Table 4B for additional details. Flat Use C fu Bending design values adjusted by size factors are based on edgewise use (load applied to narrow face). When dimension lumber is used flatwise (load applied to wide face), the bending design value (F b) shall be multiplied by the following flat use factors Width (depth) Thickness (breadth) 2 & & & wider TTT 1 Section 05 ver Truss Materials Design Values 4

5 The listed reference design values are for mechanically graded dimension Lumber Grade Bending Tension parallel Compression parallel Modulus of elasticity F b F t F c E E min MSR 1650f-1.5E 1,650 1,020 1,700 1,500, , f-1.6E 1,800 1,175 1,750 1,600, , f-1.8E 2,100 1,575 1,875 1,800, ,000 2 and less in 2400f-2.0E 2,400 1,925 1,975 2,000,000 1,020,000 thickness MEL M12 1, ,675 1,600, ,000 M14 1,800 1,000 1,750 1,700, ,000 M29 1, ,650 1,700, ,000 See also NDS Supplement and/or Southern Pine Use Guide or Western Lumber Product Use Manual or CWC US Span Book for Major Lumber Species Values for Shear parallel (F v) and compression perpendicular (F C ) are based upon species. See NDS Table 4C footnotes. SPF values for Shear parallel (F v) and compression perpendicular (F C ): Species Modulus of Elasticity Specific Gravity Design Values in pounds per square inch (psi) E (x10 6 ) psi G F V F C 1.2 & higher Spruce-Pine-Fir 1.8 to & higher Dimensional Stability WWPA - Western Lumber Product Use Manual (2005) provides the following information on the dimensional stability of Western species: Wood shrinks as it seasons (dries) from the fiber saturation point (of 28% to 30% MC) to the moisture level of surrounding atmospheric conditions. Within most structures, this moisture content level is between 8% and 12%. In one- and two-story structures, the cumulative effect of shrinkage can be accommodated on the job site, even when unseasoned lumber is specified. However, for three story and higher buildings, designs should allow for shrinkage in the horizontal members, e.g., wall plates and joists. The shrinkage of Western species (except Western Cedars) is approximately 6% as it dries from 30% to 0% MC, i.e., 0.2% shrinkage for every 1% change in moisture content. The shrinkage factor assumes a growth-ring angle of 45 and is an average for multiple species. Example: To calculate the amount of shrinkage in a 2x10 lumber floor joist, manufactured at 19% (S-SRY) with an equilibrium moisture content of 8%: 9.25 inches times times 11 = 0.20 inches Width (of dry 2x10) shrinkage factor (.2% = 0.002) % change in moisture content ( ) Vertical members exhibit less dimensional change because wood s longitudinal shrinkage is quite small (approximately.003% to.006% for every 1% change in MC). [For additional information on the dimensional stability of lumber see the Forest Products Laboratory, Wood Handbook, Chapter 13 Drying and Control of Moisture Content and Dimensional Changes ( See also PS Section in downloads.] TTT 1 Section 05 ver Truss Materials Design Values 5

6 Application of Adjustment Factors for Sawn Lumber The following table is from NDS 2012 The information in this document is provided only for use by individuals during Truss Technician Training (TTT) Level I. For solutions for real-world problems design values and adjustment factors should be used from the appropriate sources, i.e., AWC - NDS, WWPA - Western Lumber Product Use Guide, SFPA -Southern Pine Use Guide or CWA - U.S. Span Book for Major Lumber Species. TTT 1 Section 05 ver Truss Materials Design Values 6