1、Designation: D3737 09Standard Practice forEstablishing Allowable Properties for Structural GluedLaminated Timber (Glulam)1This standard is issued under the fixed designation D3737; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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 timb
3、er.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 limi
4、ted 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 usin
5、g procedures in this practice, manu-facturers must conform to recognized manufacturing standards.Refer to ANSI/AITC A190.1 and CSA O122.1.4 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided f
6、or information onlyand are not considered standard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated 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
7、regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-uctsD143 Test Methods for Small Clear Specimens of TimberD198 Test Methods of Static Tests of Lumber in StructuralSizesD245 Practice for Establishing Structural Grades a
8、nd Re-lated Allowable Properties for Visually Graded LumberD2395 Test Methods for Specific Gravity of Wood andWood-Based MaterialsD2555 Practice for Establishing Clear Wood Strength Val-uesD2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD4761 Test Methods for Mechani
9、cal Properties of Lumberand Wood-Base Structural MaterialD5456 Specification for Evaluation of Structural CompositeLumber ProductsD6570 Practice for Assigning Allowable Properties forMechanically Graded LumberE105 Practice for Probability Sampling Of Materials2.2 AITC Standards:3AITC 117-71 Standard
10、 Specifications for Structural GluedLaminated Timber of Softwood Species, 1971AITC 117-74 Standard Specifications for Structural GluedLaminated Timber of Softwood Species, 1974AITC 117-79 Standard Specifications for Structural GluedLaminated Timber of Softwood Species, 1979AITC “Brown Book” Determin
11、ation of Design Values forStructural Glued Laminated, 1979AITC Standard 407 Standard for Alternate Lumber Gradesfor Use in Structural Glued Laminated Timber, 2005AITC Standard 500 Determination of Design Values forStructural Glued Laminated Timber in Accordance withASTM D3737-89a, 1991AITC Technical
12、 Note 21 Volume Factor for StructuralGlued Laminated Timber, 2005ANSI/AITC A190.1 Structural Glued Laminated Timber,20072.3 Other Standards:ANSI/AF or solid-sawn lumber that is producedaccording to Practice D6570 and the grading rules of theapplicable grading or inspection agency.3.1.2 E-rated lumbe
13、rlumber 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 glued lami-
14、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.3.1.4 horizontally laminated timbera member designed tor
15、esist bending loads applied perpendicularly to the wide facesof the laminations (referred to as bending about the x-x axis).3.1.5 laminationa layer of lumber within the glued lami-nated timber.3.1.6 modulus of elasticity (E)for laminating, E is desig-nated in two categories to distinguish mode of me
16、asurementand application.3.1.6.1 Long-Span E (LSE)the modulus of elasticity cal-culated from deflection measured in a flat-wise static bendingtest of lumber with a center point loading and a span-to-depthratio (1d) of approximately 100 or the E obtained from TestMethods D2555 and multiplying by the
17、appropriate factorsfrom Table 1 and Table 6.3.1.6.2 Member E (Eaxial, Ex,Ey)the allowable modulus ofelasticity values of the structural glued laminated member asdefined in this practice.3.1.7 vertically laminated timbera member designed toresist bending loads applied parallel to the wide faces of th
18、elaminations (referred to as bending about the y-y axis).3.1.8 visually graded lumberlumber graded by visualinspection in accordance with the grading rules of the appli-cable grading or inspection agency.3.1.9 GDCthe ratio of the cross-sectional area of the localgrain deviation (which may or may not
19、 be associated with aknot) away from the edge of the lumber to the cross sectionalarea of the lumber (see Fig. 1).3.1.10 GDEthe ratio of the cross-sectional area of thelocal grain deviation (which may or may not be associated witha knot) at the edge of the lumber to the cross sectional area ofthe lu
20、mber (see Fig. 1).3.1.11 GDSthe projected sum of all GDE and GDCvalues within a one-foot length of lumber as defined in Fig. 1.3.1.12 KCthe ratio of the cross-sectional area of a knotlocated away from the edge of the lumber to the cross-sectionalarea of lumber. When a knot at the edge of the wide fa
21、ce anda knot located away from the edge are in the same cross-section, the combination of the two shall be used in determin-ing KC (see Fig. 2).3.1.13 KEthe ratio of cross-sectional area of a knot at theedge of wide face of lumber to the cross-sectional area of thelumber (see Fig. 2).3.1.14 SRtlthe
22、required strength ratio of the tension lami-nation at the outermost fiber.4. Materials Requirements4.1 Requirements for Laminations:4.1.1 Laminations of structural glued laminated timber shallbe of lumber with net thickness of 2 in. (0.05 m) or less.4.1.2 Lumber is permitted to be joined end to end
23、withstructural end joints to form long length laminations. End jointsshall be qualified and quality controlled with a recognizedmanufacturing standard.4.1.3 Lumber is permitted to be placed or joined side to sideto form wide laminations.4.1.4 Dimension lumber used to form laminations shall bevisuall
24、y graded or E-rated according to established gradingrules.4.1.5 Alternate lumber material is permitted by demonstrat-ing equivalence to a dimension lumber grade in accordancewith Annex A1.4.1.6 For the analysis of a structural glued laminated timberlayup, all laminations in a single cross section sh
25、all be of equalthickness.4.1.7 The analytical procedures of this standard practice arebased on specific lamination characteristics.4.1.7.1 Lumber properties including knot size and fre-quency, physical properties such as specific gravity, andmechanical properties such as modulus of elasticity shall
26、bebased on measurements of 2 3 6 lumber for definition of gradecharacteristics.4.1.7.2 The effect of decay or compression failures uponstrength cannot be readily determined, thus these defects shallbe prohibited from laminating grades insofar as existinginspection and grading technology permit. Firm
27、 white speck orlight white pocket is permissible in grades of lumber thatpermit knots to occupy up to one third or more of the crosssection provided their extent in combination with knots doesnot exceed that of the largest edge knot permitted. Theexception is that firm white speck and light white po
28、cket shallbe excluded from end joints in tension members and the outer10 % of the total depth on the tension side of bendingmembers.4.1.7.3 Compression wood (as defined in Terminology D9)in readily identifiable and damaging form shall be limited inaccordance with 4.1.7.3 (1) and 4.1.7.3 (2).(1) For
29、dry service conditions, grades permitting knots upto one half of the cross section may contain streaks ofTABLE 1 Adjustment Factors for Clear Wood Stresses(Test Methods D2555)PropertyMultipliers for Average or5th PercentileSeasoningFactor for a 12 %AverageMoistureContentSoftwoods HardwoodsBending 0.
30、476 0.435 1.35Compression parallel to grain 0.526 0.476 1.75Modulus of elasticity 1.095 1.095 1.20Horizontal shear 0.244 0.222 1.13D3737 092compression wood occupying as much as 20 % of the crosssection. Streaks of compression wood up to one eighth of thecross section may be permitted in other grade
31、s.(2) For wet service conditions, or for pressure-treatedmembers, the conditions of 4.1.7.3 (1) apply except thatcompression wood is limited to 5 % of the cross section of thelaminations in tension members and in the outer 10 % of thetotal depth on the tension side of bending members.4.1.7.4 Lumber
32、shall be free of shakes and splits that makean angle of less than 45 with the wide face of the piece. Pitchpockets shall be limited in size to the area of the largest knotpermitted, and pitch streaks shall be limited to one sixth of thewidth of the lumber.4.1.7.5 The range of moisture content of lum
33、ber for assem-bly into a single member shall not exceed five percentagepoints, except when all the lumber is 12 % or lower. Themaximum moisture content of individual laminations is 16 %,unless the in-service conditions are wet service and in this casethe maximum is 20 %.4.2 Requirements for Adhesive
34、s:4.2.1 Adhesives for use in structural glued laminated timbershall be rigid (non-elastomeric) to ensure composite action ofthe laminations and shall be sufficiently strong to transferstresses required by the intended use of the member.4.2.2 Adhesives shall be sufficiently durable to providebond for
35、 the life of the glued laminated member in its expectedservice environment.4.3 Tension Laminationsfor horizontally laminated bend-ing members shall meet the requirements herein.4.3.1 The results of full-size beam tests reported in Refs(1-3)6have yielded an empirical relationship between the sizeof k
36、nots in the tension zone and bending strength. Thisrelationship dictates that special grading considerations be6The boldface numbers in parentheses refer to a list of references at the end ofthis practice.TABLE 2 Bending Stress Index Based on Large Beam Tests and Modulus of Elasticity Values for Vis
37、ually Graded LumberNOTE 1Appendix X1 provides one method of developing new data.Species Growth ClassificationABending Stress IndexBModulus of Elasticitypsi MPa million psi MPaDouglas Fir-Larch medium grain 3000 20.7 1.9 13 100close grain 3250 22.4 2.0 13 800dense 3500 24.1 2.1 14 500Southern Pine co
38、arse grainC2000 13.8 1.5 10 300medium grain 3000 20.7 1.8 12 400dense 3500 24.1 2.0 13 800Hem-Fir medium grain 2560 17.7 1.7 11 700denseD3000 20.7 1.8 12 400AClassification for “dense” wood shall follow Practice D245.BValues shown are based on full-size beam tests. As a result, these values incorpor
39、ate the effects of some features such as grain deviations in lumber along withinfluences of end and face bonding influences. Beams designed using these values and tested in accordance with Test Methods D198 will yield strength values such thatthe lower 5th percentile will exceed the design bending s
40、tress by a factor of 2.1 with 75 % confidence. Analysis of test data assumed a log normal distribution. Forunsymmetric combinations, tests have shown that values up to 40 % higher than those listed may be applied to the compression side of bending members.CAlso applicable to minor species of souther
41、n pine regardless of growth rate.DSpecific gravity, based on oven-dry weight and volume at 12 % moisture content, must equal or exceed 0.39.TABLE 3 Bending Stress Indexes and Compression Stress IndexParallel to Grain for E-Rated Lumber Used in LaminatingALong Span,E, psiBending StressIndexACompressi
42、on StressIndex Parallelto GrainB,Cpsi MPa psi MPa1 600 000 2560 17.7 1900 13.11 900 000 3000 20.7 2400 16.52 100 000 3500 24.1 2800 19.32 300 000 4000 27.6 3100 21.4AValues shall be not higher than obtained by interpolation for intermediate Evalues.BValues are for 12-in. deep members at 12 % moistur
43、e content (dry).CValues are for members at 12 % moisture content (dry) values.TABLE 4 Parallel to Grain Stress Modification FactorsAssociated with Slope of Grain for DesigningGlulam CombinationsSlope of GrainStress Modification FactorTension Compression1:4 0.27 0.461:6 0.40 0.561:8 0.53 0.661:10 0.6
44、1 0.741:12 0.69 0.821:14 0.74 0.871:15 0.76 1.001:16 0.80 1.001:18 0.85 1.001:20 1.00 1.00TABLE 5 Constant Used to Adjust Vertically Laminated BendingStrength RatioStrength Ratio (SR1) C10.45 or greater 1.2380.40 1.2920.35 1.3460.30 1.4000.26 or less 1.444TABLE 6 Grade Adjustment Factors for Modulus
45、 of ElasticityBending Strength RatioAAdjustment Factor0.55 or greater 1.000.45 to 0.54 0.900.44 or less 0.80ADetermined in accordance with Practice D245.D3737 093applied to the laminations used in the outer 10 % of the beamdepth on the tension side.This tension side may exist on the topor bottom of
46、the beam, or both, depending upon loading andsupport conditions. If horizontally laminated timbers are manu-factured without applying these special tension laminationgrading considerations, the allowable bending stress shall bereduced by multiplying the allowable stress calculated in7.2.1.1 by 0.85
47、if the depth is 15 in. (0.38 m) or less or by 0.75if the depth exceeds 15 in. (0.38 m).4.3.2 Visually Graded Lumber:4.3.2.1 Definitions of terms required for calculation of knotand grain deviation restrictions are listed in 3.1.9-3.1.14.4.3.2.2 Knots and local grain deviations are expressed as arati
48、o of the cross-sectional area they occupy to the cross-sectional area of the lumber based on the dressed width of thelumber. They are measured using the displacement technique.Knots are measured to the lateral extremes of the knot; graindeviations (with or without knots) are measured to the laterale
49、xtremes of the zone within which the local slope of grainexceeds the allowable slope of grain for the grade. Eq 8-11which follow yield 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 limited 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
