1、Designation: D7341 14Standard Practice forEstablishing Characteristic Values for Flexural Properties ofStructural Glued Laminated Timber by Full-Scale Testing1This standard is issued under the fixed designation D7341; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in the case of revision, 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 describes procedures for full scale testingof structural
3、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 limitedmodeling), and
4、 (3) validating models used to predict charac-teristic values.1.2 This practice is limited to procedures for establishingflexural properties (Modulus of Rupture, MOR, and Modulusof Elasticity, MOE). Some of the principles for sampling andanalysis presented may be applicable to other properties.Howev
5、er, other properties may require additional testing con-siderations that are beyond the scope of this practice.1.3 This practice is not intended to supersede the provisionsof Practice D3737, but provides an alternative method forestablishing characteristic values. Lay-up combinations devel-oped in a
6、ccordance with Practice D3737 are not required to begoverned by this standard.NOTE 1The models described by Practice D3737 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 oth
7、er input properties or using lumber materials 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 consisten
8、t quality. Manufacturing shallconform to recognized manufacturing standards such as ANSIA190.1 or CSA O122.1.5 Adjustments to characteristic values to determine refer-ence values for design shall be in accordance with PracticeD2915 for allowable stress design (ASD) or SpecificationD5457 for load and
9、 resistance factor design (LRFD).1.6 Adjustments to ASD reference values for end-use con-ditions intended for design purposes shall be performed inaccordance with Practice D3737. The same adjustment factorsshall apply to LRFD reference values, except that the ASDload duration factor shall be replace
10、d by an appropriate LRFDtime effect factor as determined in accordance with recognizedindustry practice.1.7 The values stated in inch-pound units are to be regardedas standard. No other units of measurement are included in thisstandard.1.8 This standard does not purport to address all of thesafety c
11、oncerns, 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D198 Test Methods of Static Tests of
12、 Lumber in StructuralSizesD245 Practice for Establishing Structural Grades and Re-lated Allowable Properties for Visually Graded LumberD2915 Practice for Sampling and Data-Analysis for Struc-tural Wood and Wood-Based ProductsD3737 Practice for Establishing Allowable Properties forStructural Glued La
13、minated Timber (Glulam)D4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialD5456 Specification for Evaluation of Structural CompositeLumber ProductsD5457 Specification for Computing Reference Resistance ofWood-Based Materials and Structural Connections forLoad and
14、Resistance Factor DesignD6815 Specification for Evaluation of Duration of Load andCreep Effects of Wood and Wood-Based Products1This practice is under the jurisdiction of ASTM Committee D07 on Wood andis the direct responsibility of Subcommittee D07.02 on Lumber and EngineeredWood Products.Current e
15、dition approved Feb. 1, 2014. Published March 2014. Originallyapproved in 2008. Last previous edition approved in 2009 as D7341 09. DOI:10.1520/D7341-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMSt
16、andards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 Other Standards:AITC Test T119 Full Size End Joint Tension Test3ANSI A190.1 American Natio
17、nal Standard for Wood Prod-ucts Structural Glued Laminated Timber4CSA O122 Structural Glued Laminated Timber5PS-20 Voluntary Product Standard, ALS63. Terminology3.1 DefinitionsFor definitions of terms related to wood,refer to Terminology D9.3.2 Definitions of Terms Specific to This Standard:3.2.1 ap
18、parent properties, nMechanical properties as re-lated to the actual cross-sectional dimensions of the structuralglued laminated timber.3.2.2 characteristic value, nA test statistic from whichdesign values can be derived by the application of appropriateadjustment factors.3.2.2.1 DiscussionFor streng
19、th properties of structuralglued laminated timber, this value is typically a fifth percentileestimate with 75 % confidence. For deformation-basedproperties, such as modulus of elasticity, this value is repre-sented by the average value. Other statistics are permitted to beused as characteristic valu
20、es for input properties of laminationsdepending on the model. Characteristic values for structuralglued laminated timber are typically based on apparent prop-erties.3.2.3 combination, nA series of lay-ups having similarlamination properties (grades, species, and end joint strengths),similar percenta
21、ges 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 Practice D3737would be a 24F-V4 Douglas fir combination.3.2.4 lay-up, nThe specific arrangement of well-definedlam
22、ination grades for a single structural glued laminated timberdepth.3.2.5 model, nAmathematical method for predicting char-acteristic values for full-scale laminated timber based on theinput properties of the individual laminations.3.2.6 reference value, nThe characteristic value of amaterial that ha
23、s been adjusted by the procedures in PracticeD2915 or Specification D5457 for use in design equations, buthas not been adjusted for end-use conditions.3.2.7 structural-glued-laminated timber, nAn engineered,stress-rated product of a timber laminating plant comprisingassemblies of specially selected
24、and prepared wood lamina-tions securely bonded together with adhesives, with the fol-lowing characteristics: (1) the grain of all laminations isapproximately parallel longitudinally; and (2) the laminationsmay be comprised of pieces end-joined to form any length, ofpieces placed or glued edge-to-edg
25、e to make wider ones orpieces bent to curved form during gluing.3.2.8 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 Requir
26、ements4.1 General:4.1.1 Purpose for ModelingFor 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 ModelsModel
27、s that will be used to de-velop new combinations, 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 inte
28、rest.4.1.3 Single CombinationFor comparing different lay-upsand identifying critical sizes for testing within a singlecombination, transformed section analysis is sufficient topredict the stresses on each grade in the lay-up relative to thestresses in the tested lay-up. No further modeling shall ber
29、equired.4.1.4 Single Lay-UpAll modeling requirements shall bewaived if the test results are limited to a single, well-definedlay-up (that is, the number of laminations is fixed, thelamination properties are well defined, and the size (depth)tested is representative of the size intended for productio
30、n).4.2 Minimum Model Inputs:4.2.1 GeneralAt 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 Properti
31、esThe model shall account forboth lumber and 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 andstif
32、fness properties for the laminations shall 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-se
33、nt the grade.(1) SpeciesThe species or groups 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 D198 or D4761 or by t
34、he procedures ofSpecification D5456 or Practice D245.3Available from the West Coast Lumber Inspection Bureau (WCLIB), 6980 S.W. Varns, Tigard, OR 97223, http:/www.wclib.org.4Available from APAThe Engineered Wood Association, 7011 South 19thStreet, Tacoma, WA 98466, http:/www.apawood.org.5Available f
35、rom Canadian Standards Association (CSA), 5060 Spectrum Way,Mississauga, ON L4W 5N6, Canada, http:/www.csa.ca.6Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.D7341 142(3) StrengthStrength values shall be
36、 assigned to eachgrade of lumber used in the laminated timber. Values shall bedetermined by testing in accordance with Test Methods D198or D4761 or by the procedures of Specification D5456 orPractice D245. Strength values are also permitted to beassigned to a grade zone based on its interaction with
37、 the beamas a whole. (For example, the IK/IGmodel used in PracticeD3737 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 wood as demonstrated by SpecificationD6815.4.2.2.2 End
38、 Joint StrengthThe model shall include theeffect of end joints (if used) stressed in tension. Appropriateend joint tensile strengths shall be determined by full-scaletension testing in accordance with AITC Test T119 and main-tained through in-plant quality control procedures.4.2.3 Arrangement of Gra
39、des (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. Theplacement of grades shall be well
40、 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-istic analyses, the average modu
41、lus 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 apparentproperties, based on the input lamination
42、 properties.Additionally, for strength properties, the model shall accountfor the possibility of any grade of lamination in the membercontrolling the strength of the timber. The model shall identifythe critical or controlling grade zone.5. Testing Requirements5.1 GeneralFull-scale member testing can
43、 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, as compared to verifying the prope
44、rties 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 joints subject to tension.5.2 Test
45、 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 with Test MethodsD198 or D4761. If Te
46、st Method D4761 is used, the load rateshall be modified to be in accordance with Test Method D198.Specimens shall be tested under dry-service conditions (mois-ture content 16 %) and adjusted to the standard moisturecontent of 12 % in accordance with Practice D2915. Thetemperature of the test specime
47、ns shall not be less than 50Fnor more than 90F 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.5.4.2 Specimen Size(s)Speci
48、mens 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 consideredrepresentative of members w
49、ith 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 intendedproduction 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 i
