1、Designation: D 6570 04e1Standard Practice forAssigning Allowable Properties for Mechanically GradedLumber1This standard is issued under the fixed designation D 6570; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEUpdated Reference 1 in March 20071. Scope1.1 This practice covers the methodology of grade qualifi-cation, assignment of design
3、properties, and requirements forthe quality control of mechanically graded solid sawn lumber.1.2 This practice acknowledges alternative methods for theassignment of specific properties. These methods are assign-ment by test, relationship to other properties, and by proce-dures in other appropriate s
4、tandards.2. Referenced Documents2.1 ASTM Standards:2D9 Terminology Relating to WoodD 143 Test Methods for Small Clear Specimens of TimberD 198 Test Methods of Static Tests of Lumber in StructuralSizesD 245 Practice for Establishing Structural Grades and Re-lated Allowable Properties for Visually Gra
5、ded LumberD 1165 Nomenclature of Domestic Hardwoods and Soft-woodsD 1990 Practice for Establishing Allowable Properties forVisually Graded Dimension Lumber from In-Grade Testsof Full-Size SpecimensD 2395 Test Methods for Specific Gravity of Wood andWood-Based MaterialsD 2555 Test Methods for Establi
6、shing Clear Wood StrengthValuesD 2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD 3737 Practice for Establishing Allowable Properties forStructural Glued Laminated Timber (Glulam)D 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Based Mate
7、rialsD 4444 Test Methods for Use and Calibration of Hand-HeldMoisture MetersD 4761 Test Methods for Mechanical Properties of Lumberand Wood-Based Structural Material2.2 ANSI Standards:3ANSI/AITC A190.1 American National Standard for WoodProductsStructural Glued Laminated TimberANSI/AFand shall not b
8、e owned, operated, or controlled by any suchcompany.3.2.3.2 DiscussionThe agency shall conform with theprovisions for agency accreditation under the appropriateconsensus standard.3.2.4 visual evaluation, nidentification and appraisal oflumber growth and manufacturing characteristics by visualmeans a
9、s part of the lumber segregation process.NOTE 1In the United States and Canada, criteria for agency accredi-tation are contained in PS-20, ANSI/AITC A190, and CSA O141.4. Significance and Use4.1 The procedures described in this practice are intended tobe used to establish appropriate allowable unit
10、stresses, moduliof elasticity, and specific gravity for mechanically graded solidsawn lumber. An on-going quality control program to monitorcompliance with the assigned grade properties is required.5. System Requirements5.1 Mechanical Device RequirementsA mechanical de-vice used as part of the gradi
11、ng process shall demonstrate theability to measure the mechanical or physical wood propertyused to segregate the lumber.5.2 Visual Requirements:5.2.1 Characteristics to be limited by visual evaluation, shallbe documented as part of the qualification and quality controlprocedures. Such limitations sh
12、all be part of the grade require-ments.5.2.2 Personnel conducting visual evaluations shall bequalified by the agency.6. Criteria for Grade Qualification6.1 General Requirements:6.1.1 A minimum of one assigned property of a grade shallbe qualified by test. The grade assignment for propertiesqualified
13、 by test is given in 7.2.6.1.1.1 If the modulus of elasticity (MOE) is the onlyproperty assigned to a grade, it shall be evaluated by test.6.1.1.2 If both strength and MOE properties are assigned toa grade, a minimum of one strength property and one MOEproperty shall be evaluated by test. If only on
14、e strengthproperty is tested, that property shall be either the modulus ofrupture (MOR) or ultimate tensile stress (UTS).6.1.2 Each grade shall be qualified at each size and for eachspecies/species group.6.1.3 Sampling, evaluation, and presentation of data shall bein accordance with Practice D 2915.
15、6.2 Qualification Samples:6.2.1 The criteria for selecting qualification samples shall bedocumented and shall be in accordance with 6.1.3.6.2.2 All qualification samples shall meet the visual require-ments established for the grade.6.2.3 The minimum sample size for estimation of strengthproperties,
16、and MOE shall be 53 specimens.6.2.4 The minimum sample size for estimation of mean ormedian property values, other than MOE, shall be 30 speci-mens.6.2.5 When the allowable shear stress parallel to grain (Fv)or the allowable compressive stress perpendicular to grain(Fc) are determined in accordance
17、with 7.3.4 and 7.3.5,respectively, the specific gravity of a minimum of 30 qualifi-cation test specimens shall be measured and recorded.6.3 Qualification Test Methods:6.3.1 When mechanical and physical properties in Section 7are determined by tests, the appropriate ASTM standards shallbe used.6.3.2
18、Mechanical test methods shall be in accordance withTest Methods D 143, D 198,orD 4761.6.3.2.1 The determination of the MOE and MOR by edge-wise bending shall employ third-point in accordance with TestMethods D 4761.6.3.2.2 The determination of the MOE by flat-wise bendingshall be in accordance with
19、Test Methods D 4761.6.3.2.3 The UTS of a sample shall be determined accordingto Test Methods D 4761. Whenever possible, a minimum gagelength of not less than 96 in. (2.44 m) shall be used. Whendetermination of the tension parallel to the grain MOE isdesired, testing shall be conducted according to t
20、he provisionsof Test Methods D 198.6.3.2.4 The determination of the ultimate shear strengthparallel to grain values shall be in accordance with TestMethods D 143.6.3.2.5 The determination of the compression perpendicularto grain values shall be in accordance with Test MethodsD 143.6.3.3 Specific gra
21、vity shall be based on weight and dimen-sions when oven dry as specified in Test Methods D 2395.Measurements shall either be taken on oven-dried specimens,or at some other moisture content and the values adjusted to theoven-dry condition.6.3.4 Determination of the moisture content of the lumbersampl
22、e shall be in accordance with Test Methods D 4442 orD 4444.7. Procedures for Assignment of Allowable MechanicalProperties and Specific Gravity7.1 Allowable mechanical properties and specific gravityshall be assigned using the qualification test procedures of 7.2,the property correlation procedures o
23、f 7.3, or the procedures of7.4. These alternative procedures of 7.2-7.4 define the maxi-mum property values, which are permitted to be assigned to agrade of mechanically graded lumber.7.1.1 Selection of the procedures specified in 7.1 to estab-lish a value for any particular property assigned to a g
24、rade isthe prerogative of the grade specification author.7.1.2 The factors used in 7.2 and 7.3 apply to softwoodlumber.7.1.3 If the Fb is to be an assigned property, it shall bedetermined by the test procedures of 7.2.7.1.4 Hardwood lumber species shall be reduced by theapplicable factors in Practic
25、e D 245, Table 8.7.1.4.1 Species containing interlocked grain shall have Fb,Ft, and Fc evaluated by test procedures of 7.2. Sample sizeD657004e12selection shall consider the evidence of interlocked grain andits representation in the sample.7.2 Assignment of Allowable Properties by QualificationTests
26、:7.2.1 Assignment of allowable properties by test shallfollow the procedures of this section. Test results shall beevaluated according to Practice D 2915.7.2.1.1 Qualification tests are used to either establish allow-able mechanical property values for new grades or to qualifyfor published grade cat
27、egories.7.2.2 Extreme Fiber Stress in Bending (Fb)The fifthpercentile tolerance limit (75 % confidence) for the MOR of thequalification sample shall equal or exceed 2.1 times theassigned Fb value.7.2.3 Fiber Stress in Tension Parallel to Grain (Ft)Thefifth percentile tolerance limit (75 % confidence
28、) for the UTSof the qualification sample shall equal or exceed 2.1 times theassigned Ft value.7.2.4 Fiber Stress in Compression Parallel to Grain (Fc)The fifth percentile tolerance limit (75 % confidence) forultimate compressive strength parallel to grain (UCS)ofthequalification sample shall equal o
29、r exceed 1.9 times theassigned Fc value.7.2.5 Shear Stress Parallel to Grain (Fv)The fifth percen-tile tolerance limit (75 % confidence) Fv for the qualificationsample shall equal or exceed 2.1 times the assigned Fv value.7.2.6 Modulus of ElasticityThe upper 95 % confidenceinterval of the qualificat
30、ion sample mean MOE shall equal orexceed the assigned grade MOE.7.2.6.1 The upper bound of the 95 % confidence interval ofthe qualification sample mean MOE shall meet or exceed theassigned grade MOE.7.2.6.2 For grades that include a near-minimum MOE speci-fication, the sample parametric or non-param
31、etric point esti-mate as determined in accordance with Practice D 2915 shallequal or exceed the near-minimum MOE for the grade.7.2.7 Specific Gravity (SG)The upper bound of the 95 %confidence interval of the qualification sample mean specificgravity shall meet or exceed the assigned specific gravity
32、value.7.2.8 Fiber Stress in Compression Perpendicular to Grain(Fc)The Fc shall be determined by test in accordancewith Test Methods D 143, and adjusted by the procedures ofPractice D 245.7.3 Assignment of Allowable Properties Based on Relation-ships:7.3.1 The methods of 7.3 permit assignment of cert
33、ainallowable properties based on recognized relationships be-tween the assigned properties. This assignment shall be inaccordance with the following procedures.7.3.2 Fiber Stress in Tension Parallel to Grain:7.3.2.1 The maximum allowable Ft shall be assigned inaccordance with an established grade as
34、signment model basedon the assigned Fb, which has been published by the agency.7.3.2.2 In the absence of corroborative data, a maximumFt/Fb ratio of 0.45 shall be used.7.3.3 Fiber Stress in Compression Parallel to Grain:7.3.3.1 The maximum allowable Fc shall be calculated fromthe following equation:
35、Fc 50.7098Fb12060.7!/1.9 (1)where:Fb = the assigned Fb for the grade.7.3.4 Shear Parallel to GrainThe Fv determined by aspecific gravity-based model (see Appendix X1) is permittedwhen the specific gravity is assigned in accordance with 7.2.7or 7.3.6.7.3.5 Fiber Stress in Compression Perpendicular to
36、 Grain(Fc)The Fc determined by a specific gravity-basedmodel (see Appendix X1) is permitted when specific gravity isassigned in accordance with 7.2.7 or 7.3.6.7.3.6 Specific GravityIt is permitted to assign specificgravity in accordance with a model that relates gradingmachine measurement to specifi
37、c gravity. When such a modelis used, the agency shall develop corroborative data to supportthe appropriateness of the assigned specific gravity.7.4 Assignment of Allowable Properties by Other Standards:7.4.1 The methods of 7.4 permit assignment of certainallowable properties based on procedures in t
38、he appropriateASTM and ANSI standards.7.4.2 Shear Parallel to Grain StressThe Fv shall beassigned in accordance with the procedures of Practice D 245for visually graded solid sawn lumber of the same species orspecies group.7.4.3 Fiber Stress in Compression Perpendicular toGrainThe Fc shall be assign
39、ed in accordance with theprocedures of Practice D 245 for visually graded solid sawnlumber of the same species or species group.7.4.4 Specific GravityThe specific gravity shall be as-signed as reported in ANSI/AF mechanically graded lumber; solid sawn lum-ber; woodAPPENDIXES(Nonmandatory Information
40、)X1. FORMULAS FOR DETERMINING THE SHEAR STRESS PARALLEL TO GRAIN AND FIBER STRESS INCOMPRESSION PERPENDICULAR TO GRAINX1.1 Shear Stress Parallel to GrainX1.1.1 When qualified by measurement of the specificgravity (SG), the allowable stress in shear stress parallel to thegrain (Fv) shall be calculate
41、d by a relationship between SG(based on oven dry weight/oven dry volume basis) and Fv:X1.1.2 For Douglas Fir, Douglas Fir-Larch, Douglas Fir-South, Hem-Fir, Southern Pine, Spruce-Pine-Fir (South), West-ern Woods, and Western Cedars:Fv 5 266 3 SG! 1 40 (X1.1)X1.1.3 For Douglas Fir-Larch (N), Hem-Fir
42、(N), andSpruce-Pine-Fir:Fv 5 284.8 3 SG! 1 26.6 (X1.2)where:SG = specific gravity (oven-dry weight/oven-dry volumebasis)X1.2 Compression Perpendicular to the Grain (Fc)(0.04-in. deformation limit)X1.2.1 When qualified by measurement of the SG, theallowable stress shall be calculated by a relationshi
43、p betweenSG (based on oven dry weight/oven dry volume) and Fc:X1.2.1.1 For Douglas Fir, Douglas Fir-Larch, Douglas Fir-South, Hem-Fir, Southern Pine, Spruce-Pine-Fir (South), West-ern Woods, and Western Cedars:Fc 5 2252.4 3 SG! 480 (X1.3)X1.2.1.2 For Douglas Fir-Larch (N), Hem-Fir (N), andSpruce-Pin
44、e-Fir:Fc 5 2243.8 3 SG! 473.8 (X1.4)X1.3 Compression Perpendicular to the Grain (Fc)(0.02-in. deformation limit)X1.3.1 Refer to the appropriate agency grading rules forequations to adjust the Fc from a 0.04-in. deformation limitto a 0.02-in. deformation limit.X2. EXPLANATION OF SOLID SAWN LUMBER PRO
45、DUCTS CURRENTLY PRODUCED IN THE UNITED STATES ANDCANADA BY NONDESTRUCTIVE EVALUATIONX2.1 Mechanically Graded LumberX2.1.1 GeneralThe process where each piece of lumberis nondestructively evaluated by a machine to determine thevalue of the sorting parameter or grading algorithm. Mechani-cally graded
46、lumber also is required to meet certain visualrequirements. The process assigns strength and MOE valuesbased on a model that combines information from the nonde-structive parameter and visual characteristics. One exception isE-rated lumber; strength values are not assigned to E-ratedlumber.D657004e1
47、4X2.2 Machine Stress-Rated LumberX2.2.1 Lumber sorted by machine and graded based on thefollowing criteria, established under the ALSC PS-20:X2.2.1.1 Average edge MOE equal to or greater than theassigned average edge MOE.X2.2.1.2 At least 95 % of pieces have an edge MOE greaterthan 82 % of the assig
48、ned edge MOE.X2.2.1.3 At least 95 % of the pieces have a MOR greaterthan 2.1 times the assigned Fb.X2.3 Machine Evaluated LumberX2.3.1 Machine evaluated lumber is sorted by machine andgraded based on the following criteria, established under theALSC PS-20:X2.3.1.1 Average edge MOE equal to or greate
49、r than theassigned average edge MOE.X2.3.1.2 At least 95 % of pieces have an edge MOE greaterthan 75 % of the assigned edge MOE.X2.3.1.3 At least 95 % of the pieces have a MOR greaterthan 2.1 times the assigned Fb.X2.3.1.4 At least 95 % of the pieces have a UTS greater than2.1 times the assigned Ft.X2.4 E-Rated LumberX2.4.1 E-rated lumber is graded by mechanical grading intospecific MOE categories. The process assigns a long-spanflat-wise MOE value and requires adherence to a fifth percen-tile MOE value. Practice D 3737, Annex A2, specifies therelat
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