1、Designation: D198 15Standard Test Methods ofStatic Tests of Lumber in Structural Sizes1This standard is issued under the fixed designation D198; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONNumerous evaluations of structural members of sawn lumber have been conducted in accordancewith Test Methods D198. While the importance of conti
3、nued use of a satisfactory standard should notbe underestimated, the original standard (1927) was designed primarily for sawn lumber material, suchas bridge stringers and joists.With the advent of structural glued laminated (glulam) timbers, structuralcomposite lumber, prefabricated wood I-joists, a
4、nd even reinforced and prestressed timbers, aprocedure adaptable to a wider variety of wood structural members was required and Test MethodsD198 has been continuously updated to reflect modern usage.The present standard provides a means to evaluate the flexure, compression, tension, and torsionstren
5、gth and stiffness of lumber and wood-based products in structural sizes.Aflexural test to evaluatethe shear stiffness is also provided. In general, the goal of the D198 test methods is to provide areliable and repeatable means to conduct laboratory tests to evaluate the mechanical performance ofwood
6、-based products. While many of the properties tested using these methods may also be evaluatedusing the field procedures of Test Methods D4761, the more detailed D198 test methods are intendedto establish practices that permit correlation of results from different sources through the use of moreunif
7、orm procedures. The D198 test methods are intended for use in scientific studies, development ofdesign values, quality assurance, or other investigations where a more accurate test method is desired.Provision is made for varying the procedure to account for special problems.1. Scope1.1 These test me
8、thods cover the evaluation of lumber andwood-based products in structural sizes by various testingprocedures.1.2 The test methods appear in the following order:SectionsFlexure 411Compression (Short Specimen) 1320Compression (Long Specimen) 2128Tension 2936Torsion 3744Shear Modulus 45521.3 Notations
9、and symbols relating to the various testingprocedures are given in Appendix X1.1.4 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 for information onlyand are not considered standard.1.5 Th
10、is 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 regulatory limitations prior to use.2. Referenced Documen
11、ts2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-uctsD1165 Nomenclature of Commercial Hardwoods and Soft-woodsD2395 Test Methods for Density and Specific Gravity (Rela-tive Density) of Wood and Wood-Based MaterialsD2915 Practice for Sampling and Data-Analysis for Struc-tural
12、 Wood and Wood-Based ProductsD3737 Practice for Establishing Allowable Properties forStructural Glued Laminated Timber (Glulam)D4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Based Materials1These test methods are under the jurisdiction of ASTM Committee D07 onWood and a
13、re the direct responsibility of Subcommittee D07.01 on FundamentalTest Methods and Properties.Current edition approved Sept. 1, 2015. Published December 2015. Originallyapproved in 1924. Last previous edition approved in 2014 as D198141. DOI:10.1520/D0198-15.2For referenced ASTM standards, visit the
14、 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Un
15、ited States1D4761 Test Methods for Mechanical Properties of Lumberand Wood-Base Structural MaterialD7438 Practice for Field Calibration and Application ofHand-Held Moisture MetersE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE83 Practi
16、ce for Verification and Classification of Exten-someter SystemsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE2309 Practices for Verification of Displacement MeasuringSystems an
17、d Devices Used in Material Testing Machines3. Terminology3.1 DefinitionsSee Terminology E6, Terminology D9, andNomenclature D1165.3.2 Definitions:Definitions of Terms Specific to This Stan-dard:3.2.1 composite wood membera laminar constructioncomprising a combination of wood and other simple orcompl
18、ex materials assembled and intimately fixed in relation toeach other so as to use the properties of each to attain specificstructural advantage for the whole assembly.3.2.2 depth (d)the dimension of the flexure specimen orshear modulus specimen that is perpendicular to the span andparallel to the di
19、rection in which the load is applied (Fig. 1).3.2.3 shear spantwo times the distance between a reactionand the nearest load point for a symmetrically loaded flexurespecimen (Fig. 1).3.2.4 shear span-depth ratiothe numerical ratio of shearspan divided by depth of a flexure specimen.3.2.5 span ()the t
20、otal distance between reactions onwhich a flexure specimen or shear modulus specimen issupported to accommodate a transverse load (Fig. 1).3.2.6 span-depth ratio (/d)the numerical ratio of totalspan divided by depth of a flexure specimen or shear modulusspecimen.3.2.7 structural membersawn lumber, g
21、lulam, structuralcomposite lumber, prefabricated wood I-joists, or other similarproduct for which strength or stiffness, or both, are primarycriteria for the intended application and which usually are usedin full length and in cross-sectional sizes greater than nominal2 by 2 in. (38 by 38 mm).FLEXUR
22、E4. Scope4.1 This test method covers the determination of the flexuralproperties of structural members. This test method is intendedprimarily for members with rectangular cross sections but isalso applicable to members with round and irregular shapes,such as round posts, pre-fabricated wood I-joists
23、, or otherspecial sections.5. Summary of Test Method5.1 The flexure specimen is subjected to a bending momentby supporting it near its ends, at locations called reactions, andapplying transverse loads symmetrically imposed betweenthese reactions. The specimen is deflected at a prescribed rate,and co
24、ordinated observations of loads and deflections are madeuntil rupture occurs.6. Significance and Use6.1 The flexural properties established by this test methodprovide:6.1.1 Data for use in development of grading rules andspecifications;6.1.2 Data for use in development of design values forstructural
25、 members;6.1.3 Data on the influence of imperfections on mechanicalproperties of structural members;6.1.4 Data on strength properties of different species orgrades in various structural sizes;6.1.5 Data for use in checking existing equations or hypoth-eses relating to the structural behavior;6.1.6 D
26、ata on the effects of chemical or environmentalconditions on mechanical properties;6.1.7 Data on effects of fabrication variables such as depth,taper, notches, or type of end joint in laminations; and6.1.8 Data on relationships between mechanical and physi-cal properties.FIG. 1 Flexure Test MethodEx
27、ample of Two-Point LoadingD198 1526.2 Procedures are described here in sufficient detail topermit duplication in different laboratories so that comparisonsof results from different sources will be valid. Where specialcircumstances require deviation from some details of theseprocedures, these deviati
28、ons shall be carefully described in thereport (see Section 11).7. Apparatus7.1 Testing MachineA device that provides (1) a rigidframe to support the specimen yet permit its deflection withoutrestraint, (2) a loading head through which the force is appliedwithout high-stress concentrations in the spe
29、cimen, and (3)aforce-measuring device that is calibrated to ensure accuracy inaccordance with Practices E4.7.2 Support ApparatusDevices that provide support of thespecimen at the specified span.7.2.1 Reaction Bearing PlatesThe specimen shall be sup-ported by metal bearing plates to prevent damage to
30、 thespecimen at the point of contact with the reaction support (Fig.1). The plates shall be of sufficient length, thickness, and widthto provide a firm bearing surface and ensure a uniform bearingstress across the width of the specimen.7.2.2 Reaction SupportsThe bearing plates shall be sup-ported by
31、 devices that provide unrestricted longitudinal defor-mation and rotation of the specimen at the reactions due toloading. Provisions shall be made to restrict horizontal trans-lation of the specimen (see 7.3.1 and Appendix X5).7.2.3 Reaction Bearing AlignmentProvisions shall bemade at the reaction s
32、upports to allow for initial twist in thelength of the specimen. If the bearing surfaces of the specimenat its reactions are not parallel, then the specimen shall beshimmed or the individual bearing plates shall be rotated aboutan axis parallel to the span to provide full bearing across thewidth of
33、the specimen. Supports with lateral self-alignment arenormally used (Fig. 2).7.2.4 Lateral SupportSpecimens that have a depth-to-width ratio (d/b) of three or greater are subject to out-of-planelateral instability during loading and require lateral support.Lateral support shall be provided at points
34、 located abouthalfway between a reaction and a load point. Additionalsupports shall be permitted as required to prevent lateral-torsional buckling. Each support shall allow vertical movementwithout frictional restraint but shall restrict lateral displace-ment (Fig. 3).7.3 Load ApparatusDevices that
35、transfer load from thetesting machine at designated points on the specimen. Provi-sions shall be made to prevent eccentric loading of the loadmeasuring device (see Appendix X5).7.3.1 Load Bearing BlocksThe load shall be appliedthrough bearing blocks (Fig. 1), which are of sufficient thick-ness and e
36、xtending entirely across the specimen width toeliminate high-stress concentrations at places of contact be-tween the specimen and bearing blocks. Load shall be appliedto the blocks in such a manner that the blocks shall bepermitted to rotate about an axis perpendicular to the span (Fig.4). To preven
37、t specimen deflection without restraint in case oftwo-point loading, metal bearing plates and rollers shall beused in conjunction with one or both load-bearing blocks,depending on the reaction support conditions (see AppendixX5). Provisions such as rotatable bearings or shims shall bemade to ensure
38、full contact between the specimen and theloading blocks. The size and shape of these loading blocks,plates, and rollers may vary with the size and shape of thespecimen, as well as for the reaction bearing plates andsupports. For rectangular structural products, the loadingsurface of the blocks shall
39、 have a radius of curvature equal totwo to four times the specimen depth. Specimens havingcircular or irregular cross-sections shall have bearing blocksthat distribute the load uniformly to the bearing surface andpermit unrestrained deflections.7.3.2 Load PointsLocation of load points relative to th
40、ereactions depends on the purpose of testing and shall berecorded (see Appendix X5).7.3.2.1 Two-Point LoadingThe total load on the specimenshall be applied equally at two points equidistant from thereactions. The two load points will normally be at a distancefrom their reaction equal to one third of
41、 the span (/3)(third-point loading), but other distances shall be permitted forspecial purposes.7.3.2.2 Center-Point LoadingA single load shall be ap-plied at mid-span.7.3.2.3 For evaluation of shear properties, center-point load-ing or two-point loading shall be used (see Appendix X5).7.4 Deflectio
42、n-Measuring Apparatus:7.4.1 GeneralFor modulus of elasticity calculations, de-vices shall be provided by which the deflection of the neutralaxis of the specimen at the center of the span is measured withrespect to a straight line joining two reference points equidis-tant from the reactions and on th
43、e neutral axis of the specimen.FIG. 2 Example of Bearing Plate (A), Rollers (B), and Reaction-Alignment-Rocker (C), for Small Flexure SpecimensD198 1537.4.1.1 The apparent modulus of elasticity (Eapp) shall becalculated using the full-span deflection (). The referencepoints for the full-span deflect
44、ion measurements shall bepositioned such that a line perpendicular to the neutral axis atthe location of the reference point, passes through the supportscenter of rotation.7.4.1.2 The true or shear-free modulus of elasticity (Esf)shall be calculated using the shear-free deflection. The refer-ence po
45、ints for the shear-free deflection measurements shall bepositioned at cross-sections free of shear and stress concentra-tions (see Appendix X5).NOTE 1The apparent modulus of elasticity (Eapp) may be converted tothe shear-free modulus of elasticity (Esf) by calculation, assuming that theshear modulus
46、 (G) is known. See Appendix X2.7.4.2 Wire DeflectometerA wire stretched taut betweentwo nails, smooth dowels, or other rounded fixtures attached tothe neutral axis of the specimen directly above the reactionsand extending across a scale attached at the neutral axis of thespecimen at mid-span shall b
47、e permitted to read deflectionswith a telescope or reading glass to magnify the area where thewire crosses the scale. When a reading glass is used, areflective surface placed adjacent to the scale will help to avoidparallax.7.4.3 Yoke DeflectometerA satisfactory device commonlyused to measure deflec
48、tion of the center of the specimen withrespect to any point along the neutral axis consists of alightweight U-shaped yoke suspended between nails, smoothdowels, or other rounded fixtures attached to the specimen atits neutral axis. An electronic displacement gauge, dialmicrometer, or other suitable
49、measurement device attached tothe center of the yoke shall be used to measure verticaldisplacement at mid-span relative to the specimens neutralaxis (Fig. 4).7.4.4 Alternative DeflectometersDeflectometers that donot conform to the general requirements of 7.4.1 shall bepermitted provided the mean deflection measurements are notsignificantly different from those devices conforming to 7.4.1.The equivalency of such devices to deflectometers, such asthose described in 7.4.2 or 7.4.3, shall be documented anddemonstrated by comparison testing.NOTE 2W
