1、Designation: D 3737 08Standard Practice forEstablishing Allowable Properties for Structural GluedLaminated Timber (Glulam)1This standard is issued under the fixed designation D 3737; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the procedures for establishingallowable properties for structural glued laminated ti
3、mber.Included are the allowable stresses for bending, tension andcompression parallel to the grain, horizontal shear, compres-sion perpendicular to the grain, and radial tension and com-pression in curved members. Also included are modulus ofelasticity and modulus of rigidity.1.2 This practice is li
4、mited to the calculation of allowableproperties subject to the given procedures for the selection andarrangement of grades of lumber of the species considered.1.3 Requirements for production, inspection and certifica-tion are not included, but in order to justify the allowableproperties developed us
5、ing procedures in this practice, manu-facturers must conform to recognized manufacturing standards.Refer to ANSI/AITC A190.1 and CSA 0122.1.4 The values stated in inch-pound units are to be regardedas standard.1.5 This standard does not purport to address all of thesafety concerns, if any, associate
6、d with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-uctsD 198
7、Test Methods of Static Tests of Lumber in StructuralSizesD 245 Practice for Establishing Structural Grades and Re-lated Allowable Properties for Visually Graded LumberD 2395 Test Methods for Specific Gravity of Wood andWood-Based MaterialsD 2555 Practice for Establishing Clear Wood Strength Val-uesD
8、 2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD 4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialD 5456 Specification for Evaluation of Structural Compos-ite Lumber ProductsD 6570 Practice for Assigning Allowable Properties forM
9、echanically Graded LumberE 105 Practice for Probability Sampling Of Materials2.2 Other Standards:ANSI/AITC A190.1 Structural Glued Laminated Timber3ANSI/AF or solid-sawn lumber that is producedaccording to Practice D 6570 and the grading rules of theapplicable grading or inspection agency.3.1.2 E-ra
10、ted lumberlumber graded for use in manufac-turing structural glued laminated timber by nondestructivemeasurement of a modulus of elasticity (E) and by visualinspection in accordance with the grading rules of the appli-cable grading or inspection agency.3.1.3 glulama term used to denote structural gl
11、ued lami-nated timber, which is a product made from suitably selectedand prepared pieces of wood bonded together with an adhesiveeither in a straight or curved form with the grain of all piecesessentially parallel to the longitudinal axis of the member.1This practice is under the jurisdiction of AST
12、M Committee D07 on Wood andis the direct responsibility of Subcommittee D07.02 on Lumber and EngineeredWood Products.Current edition approved April 15, 2008. Published June 2008. Originallyapproved in 1978. Last previous edition approved in 2007 as D 3737 07.2For referenced ASTM standards, visit the
13、 ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from the American Institute of Timber Construction, 7012 S. RevereParkway, Suite 140, Cente
14、nnial, CO 80112, https:/www.aitc-glulam.org.4Available from American Forest and Paper Association (AF graindeviations (with or without knots) are measured to the lateralextremes of the zone within which the local slope of grainexceeds the allowable slope of grain for the grade. Eq 8-11which follow y
15、ield the maximum allowable knot and graindeviation ratios in the outer 10 % of depth. It is suggested theseratios be adjusted downward to the nearest 0.05 or to the nextnearest convenient fraction (such as13).4.3.2.3 Beams Greater than 15 in. (0.38 m) in Depth:(1) Outer 5 %Grain deviation shall be l
16、imited in accor-dance with Eq 1 and 2.GDS#1.551SRtl! (1)GDS#1.821SRtl! (2)(a) Eq 1 shall be used when GDE, with or without GDC,is used to determine GDS (Fig. 1). Eq 2 shall apply when GDEis not used to determine GDS. In addition, general slope ofgrain shall not exceed 1:16 if the required strength r
17、atio of thetension lamination is 0.60 or greater. If SRtlis less than 0.60,the general slope of grain shall not exceed 1:12.(2) Next Inner 5 %Knots are restricted in accordancewith Eq 3 and 4.KE 5 0.66 0.45 SRtl(3)KC 5 1.20 0.93 SRtl(4)(a) General slope of grain shall be limited in accordancewith th
18、e strength requirements of the individual laminations.4.3.2.4 Beams 12 in. (0.30 m) to 15 in. (0.38 m) in Depth:(1) Outer 5 %The requirements of 4.3.2.3 (1) applyexcept that SRtlshall be multiplied by 0.90 in Eq 1 and 2. Thevalue of 0.9 SRtlshall not be taken as less than 0.50.(2) Next Inner 5 %Gene
19、ral slope of grain shall be limitedin accordance with the strength requirements of the individuallaminations.(a) (b)GDC = y/b GDC = y/bGDE = z/b GDE = z/bGDS = x/b where x=y+z GDS= x/b where x15in.A4.1.12 The required strength ratio of the tension lamina-tion (SRTL) shall be calculated using EqA4.15
20、, and the tensionlamination grading requirements of 4.3 shall be determined, ifa tension lamination factor of 1.0 is used in Equation EqA4.14.SRTL5FbxS2dTLDDSETLETDSIgITDBSITL(A4.15)where:dTL= distance from neutral axis to outer edge of tensionlamination,ETL= long-span modulus of elasticity of the l
21、umber inthe outermost tension zone, andBSITL= bending stress index of the lumber in the outer-most tension zone.A4.2 ExampleGiven the 20-lamination beam shown inFig. A4.1 and the lumber grade data in Table A4.1, determinethe allowable bending stress and tension lamination gradingrequirements for fle
22、xure with compression at the top of thesection.A4.2.1 The neutral axis is located relative to the bottom ofthe beam using Eq A4.1. For convenience, distances aremeasured in number of laminations.y 5S2.12D22! 1S1.82D7222! 1S1.12D15272!1S1.82D192152! 1S2.12D202192!2.12! 1 1.872! 1 1.1157! 1 1.81915! 1
23、 2.12019!FIG. A4.1 Example of a 20-Lamination BeamD37370814y 5 9.740 laminations from the bottomA4.2.1.1 The core zone is split by the neutral axis into twozones for the analysis and the zones are numbered from thebottom of the beam. The distance from the neutral axis to theedges of each zone (Fig.
24、A4.1) are determined using Eq A4.2and A4.3.N05 09.740! 5 9.740N15 29.740! 5 7.740N25 79.740! 5 2.740N35 9.740 9.740! 5 0N45 15 9.740! 5 5.260N55 19 9.740! 5 9.260N65 20 9.740! 5 10.260A4.2.1.2 Negative results indicate that the zone boundariesrepresented by N0, N1, and N2are below the neutral axis.P
25、ositive results indicate that the zone boundaries representedby N4, N5, and N6are above the neutral axis.A4.2.2 The transformed moment of inertia for each zoneabout the neutral axis is calculated using Eq A4.4. Forconvenience, the width of the untransformed section, b, will beset equal to unity.I65S
26、2.12.1D10.263 9.2603!35 95.34I55S1.82.1D9.2603 5.2603!35 185.3I45S1.12.1D5.260303!35 25.41I35S1.12.1D03 2.740!3!35 3.592I25S1.82.1D2.740!3 7.740!3!35 126.6I15S2.12.1D7.740!3 9.740!3!35 153.4A4.2.2.1 The moment of inertia of the transformed sectionis calculated using Eq A4.5.IT5 I11 I21 I31 I41 I51 I
27、65 153.4 1 126.6 1 3.592 1 25.41 1 185.3 1 95.345 589.6A4.2.3 The moment of inertia of the untransformed (gross)section is calculated using Eq A4.6.Ig5203125 666.7A4.2.4 Weighting factors, Ojand Pjare calculated for eachzone using Eq A4.7 and A4.8.O65 210.263 9.2603! 5 572.0P6525910.26!5510.26!31 10
28、.26! 99.260!51 59.260!3 9.260!5 163.6103!O55 29.2603 5.2603! 5 1297P552599.260!559.260!31 9.260! 95.260!51 55.260!3 5.260!5 229.3103!O45 25.260303! 5 291.1P452595.260!555.260!31 5.260! 90!51 50!3 0!5 14.21103!O35 203 2.740!3! 5 41.14P352590!550!31 0! 92.740!51 52.740!3 2.740!5 515.9O25 22.740!3 7.74
29、0!3! 5 443.1P252592.740!552.740!31 2.740! 97.740!51 57.740!3 7.740!5 98.56103!O15 27.740!3 9.740!3! 5 920.7P152597.740!557.740!31 7.740! 99.740!51 59.740!3 9.740!5 214.6103!A4.2.5 An Ik/Igratio is calculated for each zone using EqA4.9.SIkIgD650.069!S2.12.1D572.0! 1 0.109!S1.82.1D1297! 1 0.230!S1.12.
30、1D291.1!210.26!31!0.353!2S2.12.1D2163.3103! 1 0.440!2S1.82.1D2229.3103!1 0.558!2S1.12.1D214.21103!210.26!3TABLE A4.1 Lumber Data for Analysis of Glulam Beam Bending Stress (see Ref (13)Grade and SpeciesAModulus of ElasticityBBending Stress IndexCKnot DataDSRbx minEx 99.5 Percentile hpsi MPa psi MPa
31、% % %L1 Douglas fir 2 100 000 14 500 3500 24.1 6.9 42.2 35.3 0.75L2 Douglas fir 1 800 000 12 400 3000 20.7 10.9 54.9 44.0 0.67L3 Lodgepole pine 1 100 000 7 600 1933 13.3 23.0 78.8 55.8 0.5AGraded in accordance with WWPA and WCLIB rules under the American Lumber Standard (5 and 6). L3 lodgepole pine
32、graded under rules for L3 Douglas fir.BBased on 6.1.4 for Douglas fir and 6.1.4 and 7.5 for lodgepole pine.CBased on 6.1.1.1 for Douglas fir and 6.1.1 for lodgepole pine.DBased on knot surveys and analysis in accordance with Annex A3 and Annex A6.EAs determined by formula X1.2 of Practice D 245, in
33、accordance with 7.2.1.1 (1).D37370815SIkIgD65 0.198SIkIgD550.109!S1.81.8D1297! 1 0.230!S1.11.8D291.1!29.260!310.440!2S1.81.8D2229.3103! 1 0.558!2S1.11.8D214.21103!29.260!3SIkIgD55 0.2499SIkIgD450.230!S1.11.1D291.1! 10.558!2S1.11.1D214.21103!25.260!3SIkIgD45 0.4585SIkIgD350.230!S1.11.1D41.14! 10.558!
34、2S1.11.1D2515.9!22.740!3SIkIgD35 0.5381SIkIgD250.109!S1.81.8D443.1! 1 0.230!S1.11.8D41.14!27.740!310.440!2S1.81.8D298.56103! 1 0.558!2S1.11.8D2515.9!27.740!3SIkIgD25 0.2075SIkIgD150.069!S2.12.1D920.7! 1 0.109!S1.82.1D443.1! 1 0.230!S1.12.1D41.14!29.740!31!0.353!2S2.12.1D2214.6103! 1 0.440!2S1.82.1D2
35、98.56103!1 0.558!2S1.12.1D2515.9!29.740!3SIkIgD15 0.1688A4.2.6 The stress modification factor for knots is calculatedfor each zone using EqA4.10, subject to the minimum strengthratio from 7.2.1.1 (1) (Table A4.1).SMFbx knots 65 1 1 30.1980!10.1980!3S1S0.19802DD$ 0.75SMFbx knots 65 0.741 $ 0.75SMFbx
36、knots 65 0.75SMFbx knots 55 1 1 30.2499!10.2499!3S1S0.24992DD$ 0.67SMFbx knots 55 0.646 $ 0.67SMFbx knots 55 0.67SMFbx knots 45 1 1 30.4585!10.4585!3S1S0.45852DD$ 0.50SMFbx knots 45 0.291 $ 0.50SMFbx knots 45 0.50SMFbx knots 35 1 1 30.5381!10.5381!3S1S0.53812DD$ 0.50SMFbx knots 35 0.211 $ 0.50SMFbx
37、knots 35 0.50SMFbx knots 25 1 1 30.2075!10.2075!3S1S0.20752DD$ 0.67SMFbx knots 25 0.724 $ 0.67SMFbx knots 25 0.724SMFbx knots 15 1 1 30.1688!10.1688!3S1S0.16882DD$ 0.75SMFbx knots 15 0.792 $ 0.75SMFbx knots 15 0.792A4.2.7 The stress modification factor for slope of grain isdetermined for each zone f
38、rom Table 4, using the factors forcompression for the zones above the neutral axis and thefactors for tension for the zones below the neutral axis.SMFbx SOG 6= 0.87SMFbx SOG 5= 0.82SMFbx SOG 4= 0.66SMFbx SOG 3= 0.53SMFbx SOG 2= 0.69SMFbx SOG 1= 0.74A4.2.8 The stress modification factor for each zone
39、 isdetermined using Eq A4.11.SMFbx 6= min0.75, 0.87 = 0.75SMFbx 5= min0.67, 0.82 = 0.67SMFbx 4= min0.5, 0.66 = 0.5SMFbx 3= min0.5, 0.53 = 0.5SMFbx 2= min0.724, 0.69 = 0.69SMFbx 1= min0.792, 0.74 = 0.74A4.2.9 The maximum stress permitted on each zone iscalculated using Eq A4.12.Fmax,6= 1.4 (3500 psi)
40、 (0.75) = 3675 psiFmax,5= 1.4 (3000 psi) (0.67) = 2814 psiFmax,4= 1.4 (1930 psi) (0.50) = 1351 psiFmax,3= 1.0 (1930 psi) (0.50) = 965 psiFmax,2= 1.0 (3000 psi) (0.69) = 2070 psiFmax,1= 1.0 (3500 psi) (0.74) = 2590 psiA4.2.10 The apparent outer fiber stress on the beamcorresponding to Fmax, jfor each
41、 zone is calculated using EqA4.13.sapparent,65 3675 psiS1010.26DS2.12.1DS589.6666.7D 5 3168 psisapparent,55 2814 psiS109.26DS2.11.8DS589.6666.7D 5 3135 psisapparent,45 1351 psiS105.26DS2.11.1DS589.6666.7D 5 4336 psisapparent,35 965 psiS102.74DS2.11.1DS589.6666.7D 5 5946 psisapparent,25 2070 psiS107.
42、74DS2.11.8DS589.6666.7D 5 2759 psisapparent,15 2590 psiS109.74DS2.12.1DS589.6666.7D 5 2352 psiA4.2.11 The allowable flexural design stress (Fbx) is deter-mined using Eq A4.14 and rounded according to the rulesgiven in 5.2.Fbx5 min$3168, 3135, 4336, 5946, 2759, 2352% psi!1.0! 5 2352 psi(1) Rounding i
43、n accordance with 5.2 gives:Fbx5 2400 psiD37370816A4.2.12 The required strength ratio of the tension lamina-tion (SRTL) is calculated using Eq A4.15.SRTL52400 psiS29.74!20DS2.12.1DS666.7589.6D3500 psi5 0.755(1) The maximum permitted grain deviations in the tensionlaminations for the outermost 5 % of
44、 the depth on the bottomof the beam are determined as follows:GDSC5 1.821 0.755! 5 0.446GDSE5 1.551 0.755! 5 0.380(2) Because the required strength ratio of the tensionlamination is greater than 0.60, the general slope of grain mustnot exceed 1:16.SOG#1:16(3) The maximum size knots (expressed as fra
45、ction oflamination width) in the next inner 5 % of the depth on thebottom of the beam are determined as follows:KE 5 0.66 0.450.755! 5 0.320KC 5 1.20 0.930.755! 5 0.498A5. PROCEDURE FOR DETERMINING DESIGN STRESSES IN COMPRESSION PARALLEL TO GRAINA5.1 Procedural StepsA5.1.1 The transformed area facto
46、r, Ta, shall be determinedas follows:Ta5(k51nEkAkE1 (k51nAk(A5.1)where:n = total number of laminations,Ek= long-span modulus of elasticity of kth lamination,Ak= actual (untransformed) cross-sectional area occupiedby kth lamination, andE1= long-span modulus of elasticity of outermost lamina-tion on t
47、he bottom face.A5.1.2 Using values of the average (mk) and the standarddeviation (sk) knot size determined in accordance with 5.3 forthe respective laminations, values for composite average knotsize (mc) and composite standard deviation knot size (sc) shallbe calculated for the combination as follow
48、s:mc5(k51nEkAkmk!E1 (k51nAk(A5.2)sc5H(k51nSEk2Ak2sk2DJ1/2E1 (k51nAk(A5.3)A5.1.2.1 For glulam members made with single-grade lami-nations, Eq A5.3 can be reduced to:sc5sn1/2(A5.4)where:n = total number of laminations, ands = standard deviation knot size for the laminations inaccordance with 5.3 (s = s1= s2= . = sk).A5.1.3 The composite knot size at the 99.5 percentile, Y1,shall be computed as follows:Y15 m 1 2.576s (A5.5)where m, s, and Y1are expressed in decimal fractions of thewidth of the dressed size of lumber used for a lamination.A5.1.4
