ASTM D7341-2008 430 Standard Practice for Establishing Characteristic Values for Flexural Properties of Structural Glued Laminated Timber by Full-Scale Testing.pdf

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1、Designation: D 7341 08Standard Practice forEstablishing Characteristic Values for Flexural Properties ofStructural Glued Laminated Timber by Full-Scale Testing1This standard is issued under the fixed designation D 7341; the number immediately following the designation indicates the year oforiginal a

2、doption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes procedures for full scale testingof structur

3、al glued laminated timber (glulam) to determine orverify characteristic values used to calculate flexural designproperties. Guidelines are given for: (1) testing individualstructural glued laminated timber lay-ups (with no modeling),(2) testing individual glulam combinations (with limited mod-eling)

4、, and (3) validating models used to predict characteristicvalues.1.2 This practice is limited to procedures for establishingflexural properties (MOR and MOE). Some of the principlesfor sampling and analysis presented may be applicable to otherproperties. However, other properties may require additio

5、naltesting considerations that are beyond the scope of thispractice.1.3 This practice is not intended to supersede the provisionsof Practice D 3737, but provides an alternative method forestablishing characteristic values. Lay-up combinations devel-oped in accordance with Practice D 3737 are not req

6、uired to begoverned by this standard.NOTE 1The models described by Practice D 3737 have been devel-oped and modified based on more than 50 years of experience and manytest programs. In some cases, however, it may be desirable to develop anew model based on other input properties or using lumber mate

7、rials orgrades not covered by that standard.1.4 Details of production, inspection, and certification arebeyond the scope of this document. However, for test results tobe representative of production, quality control systems shallbe in place to ensure consistent quality. Manufacturing shallconform to

8、 recognized manufacturing standards such as ANSI/AITC A190.1 or CSA O122.1.5 Adjustments to characteristic values to determine refer-ence values for design shall be in accordance with PracticeD 2915 for allowable stress design (ASD) or SpecificationD 5457 for load and resistance factor design (LRFD)

9、.1.6 Adjustments to ASD reference values for end-use con-ditions intended for design purposes shall be performed inaccordance with Practice D 3737. The same adjustment factorsshall apply to LRFD reference values, except that the ASD“load duration” factor shall be replaced by an appropriateLRFD “time

10、 effect” factor as determined in accordance withrecognized industry practice.1.7 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 determ

11、ine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 198 Test Methods of Static Tests of Lumber in StructuralSizesD 245 Practice for Establishing Structural Grades and Re-lated Allowable Properties for Visually Graded LumberD 2915 Practice for Ev

12、aluating Allowable Properties forGrades of Structural LumberD 3737 Practice for Establishing Allowable Properties forStructural Glued Laminated Timber (Glulam)D 4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialD 5456 Specification for Evaluation of Structural Com

13、pos-ite Lumber ProductsD 5457 Specification for Computing Reference Resistanceof Wood-Based Materials and Structural Connections forLoad and Resistance Factor DesignD 6815 Specification for Evaluation of Duration of Loadand Creep Effects of Wood and Wood-Based Products2.2 Other Standards:ANSI/AITC A

14、190.1 American National Standard for WoodProducts Structural Glued Laminated Timber3AITC Test T119 Full Size End Joint Tension Test31This practice is under the jurisdiction of ASTM Committee D07 on Wood andis the direct responsibility of Subcommittee D07.02 on Lumber and EngineeredWood Products.Curr

15、ent edition approved Feb. 1, 2008. Published February 2008.2For referenced ASTM standards, visit the 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.3A

16、vailable from the American Institute of Timber Construction (AITC), 7012 S.Revere Parkway Suite 140, Centennial, CO 80112, infoaitc-glulam.org1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.CSA O122 Structural Glued Laminated Timber4

17、PS-20 Voluntary Product Standard, ALS53. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 apparent properties, nMechanical properties as re-lated to the actual cross-sectional dimensions of the structuralglued laminated timber.3.1.2 characteristic value, nA test statistic from whi

18、chdesign values can be derived by the application of appropriateadjustment factors. For strength properties of structural gluedlaminated timber, this value is typically a fifth percentileestimate with 75 % confidence. For deformation-based prop-erties, such as modulus of elasticity, this value is re

19、presentedby the average value. Other statistics are permitted to be usedas characteristic values for input properties of laminationsdepending on the model. Characteristic values for structuralglued laminated timber are typically based on apparent prop-erties.3.1.3 combination, nA series of lay-ups h

20、aving similarlamination properties (grades, species, and end joint strengths),similar percentages of grade placement in the areas of criticalstresses, and similar predicted properties, that are groupedtogether for design purposes.NOTE 2An example of a lay-up combination based on PracticeD 3737 would

21、 be a 24F-V4 Douglas fir combination.3.1.4 lay-up, nThe specific arrangement of well-definedlamination grades for a single structural glued laminated timberdepth.3.1.5 model, nA mathematical method for predicting acharacteristic value for full-scale laminated timber based on theinput properties of t

22、he individual laminations.3.1.6 reference value, nThe characteristic value of amaterial that has been adjusted by the procedures in PracticeD 2915 or Specification D 5457 for use in design equations,but has not been adjusted for end-use conditions.3.1.7 structural glued laminated timber, nAproduct m

23、adefrom suitably selected and prepared pieces of componentlaminations, hereafter referred to as “lumber” in this practicebut including sawn lumber, manufactured lumber, or structuralcomposite lumber, bonded together with an adhesive, with thegrain of all pieces essentially parallel to the longitudin

24、al axis ofthe member.3.1.8 well-defined grade, nA lumber grade with specificlimits on acceptable characteristics, such as knots, slope ofgrain, density, modulus of elasticity, tensile strength, etc., toensure reproducibility in production.4. Modeling Requirements4.1 General:4.1.1 Purpose for Modelin

25、gFor test results to be appli-cable to structural glued laminated timber sizes that are nottested, it is necessary to relate the properties of the componentlaminations to the beam properties through the use of ananalytical model.4.1.2 Predictive ModelsModels that will be used to de-velop new combina

26、tions, predict characteristic values, andassign design values shall be able to predict accurately thesevalues for a broad range of combinations. These results must bevalidated by full-scale tests according to appropriate testmethods for the property of interest.4.1.3 Single CombinationFor comparing

27、different lay-upsand identifying critical sizes for testing within a single com-bination, transformed section analysis is sufficient to predictthe stresses on each grade in the lay-up relative to the stressesin the tested lay-up. No further modeling shall be required.4.1.4 Single Lay-UpAll modeling

28、requirements shall bewaived if the test results are limited to a single, well-definedlay-up (i.e., the number of laminations is fixed, the grades oflaminations are well defined, and the size (depth) tested isrepresentative of the size intended for production).4.2 Minimum Model Inputs:4.2.1 GeneralAt

29、 a minimum, a suitable model shall bebased on defined lamination properties representative of thematerial used for each lamination and shall account for theplacement of different qualities of laminations throughout thecross section.4.2.2 Lamination PropertiesThe model shall account forboth lumber an

30、d end joint properties.4.2.2.1 Lumber GradeThe species and grades of lumberused in structural glued laminated timber shall be well definedto ensure consistent performance between the grades used intest members and future production members. Strength andstiffness properties for the laminations shall

31、be assignedaccording to the lumber grade. For deterministic models, theproperties assigned to the grade shall be a representativecharacteristic value for the grade. For probabilistic models, aparametric distribution of values shall be determined to repre-sent the grade.(1) SpeciesThe species or grou

32、ps of species permitted bythe grade shall be well defined and shall be represented in thetested members.(2) Modulus of ElasticityFor each grade of lumber used,the modulus of elasticity shall be determined in accordancewith Test Methods D 198 or D 4761 or by the procedures ofSpecification D 5456 or P

33、ractice D 245.(3) StrengthStrength values shall be assigned to eachgrade of lumber used in the laminated timber. Values shall bedetermined by testing in accordance with Test Methods D 198or D 4761 or by the procedures of Specification D 5456 orPractice D 245. Strength values are also permitted to be

34、assigned to a grade zone based on its interaction with the beamas a whole. (For example, the IK/IGmodel used in PracticeD 3737 assigns strength values in this way.)(4) CreepStructural composite lumber for use in struc-tural glued laminated timber shall demonstrate creep perfor-mance similar to solid

35、 wood as demonstrated by SpecificationD 6815.4.2.2.2 End Joint StrengthThe model shall include theeffect of end joints (if used) stressed in tension. Appropriate4Available from Canadian Standards Association (CSA), 5060 Spectrum Way,Mississauga, ON L4W 5N6, Canada, http:/www.csa.ca.5Available from N

36、ational Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.D7341082end joint tensile strengths shall be determined by full-scaletension testing in accordance with AITC Test T119 and main-tained through in-plant quality control proc

37、edures.4.2.3 Arrangement of Grades (Lay-Up)The arrangementof laminations of varying quality throughout a laminatedtimber can significantly alter the stress distribution and perfor-mance of the member. The model shall account for these effectsif more than one grade of laminations is to be used. Thepl

38、acement of grades shall be well defined to ensure propermodeling and reproducibility in production.4.3 Minimum Model Analyses:4.3.1 Transformed-Section AnalysisThe stresses at thelocation of each change of grade in a cross section shall bedetermined using transformed section analysis. For determin-i

39、stic analyses, the average modulus of elasticity of each lumbergrade shall be used. The use of probabilistic models withsimulated values of modulus of elasticity is also acceptable.4.3.2 Prediction of PropertiesThe model shall predictcharacteristic values for the laminated timbers apparent prop-erti

40、es, based on the input lamination properties. Additionally,for strength properties, the model shall account for the possi-bility of any grade of lamination in the member controlling thestrength of the timber. The model shall identify the critical orcontrolling grade zone.5. Testing Requirements5.1 G

41、eneralFull-scale member testing can be used to (1)establish the properties of a single lay-up, (2) determine theproperties of a combination, or (3) validate a model intendedfor use in the prediction and assignment of characteristicvalues. Increased testing shall be required for validation of amodel,

42、 as compared to verifying the properties of a singlecombination or lay-up. Standard production procedures shallbe followed for the manufacture of all test specimens. Matchedend joint specimens shall be manufactured and tested inconjunction with tests of structural glued laminated timberutilizing end

43、 joints subject to tension.5.2 Test CertificationTesting shall be witnessed by aqualified third-party agency or conducted by an accreditedlaboratory that shall certify the test methods and results.5.3 Test MethodTests for flexural strength and modulus ofelasticity shall be conducted in accordance wi

44、th Test MethodsD 198 or D 4761. If Test Method D 4761 is used, the load rateshall be modified to be in accordance with Test Method D 198.Specimens shall be tested under dry-service conditions(MC 16 %) and adjusted to the standard moisture content of12 % in accordance with Practice D 2915. The temper

45、ature ofthe test specimens shall not be less than 50F nor more than90F at the time of the tests.5.4 Sampling Requirements for a Single Lay-Up:5.4.1 Grading and Lay-UpLamination quality (grades,species, and end joint strength) and grade placement shall bewell defined and verified prior to testing.5.4

46、.2 Specimen Size(s)Specimens for testing shall be thespecific size (depth) of a single, well-defined lay-up in accor-dance with 4.1.4. Width of the specimens shall be representa-tive of the size intended for production. For horizontallylaminated beams, a single width is permitted to be consideredrep

47、resentative of members with widths not more than 2 in.wider nor 2 in. narrower than the tested width, provided thatthe selection (grading) criteria relative to the cross-sectionalsize is the same for each width. For vertically laminated beams,the depth of test specimens shall be representative of in

48、tendedproduction sizes, and the width shall be based on the number oflaminations and shall be equal to the number of laminationsintended for use in production.5.4.3 Sample SizeA minimum of 30 specimens shall berequired for each lay-up.5.4.4 FacilitiesIf the lay-up is intended to be produced inmultip

49、le facilities, samples shall be obtained from enoughplants to represent all major processing variables includinglumber characteristics and end joint strength.5.5 Sampling Requirements for a Single Combination:5.5.1 Lay-Ups and Sample SizeFor horizontally lami-nated beams, a minimum of two critical depths based on atransformed section analysis shall be selected for testing. Thelay-ups at the critical depths shall be representative of a groupof similar lay-ups within the combination. A minimum of 15members per critical depth shall be tested with 30