1、Designation: D 198 08Standard Test Methods ofStatic Tests of Lumber in Structural Sizes1This standard is issued under the fixed designation D 198; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、in 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 solid sawn lumber have been conducted inaccordance with Test Methods D 198 27. While the importa
3、nce of continued use of a satisfactorystandard should not be underestimated, the original standard (1927) was designed primarily for sawnmaterial, such as solid wood bridge stringers and joists. With the advent of laminated timbers,wood-plywood composite members, and even reinforced and prestressed
4、timbers, a procedureadaptable to a wider variety of wood structural members is required.The present standard expands the original standard to permit its application to wood members of alltypes. It provides methods of evaluation under loadings other than flexure in recognition of theincreasing need f
5、or improved knowledge of properties under such loadings as tension to reflect theincreasing use of dimensions lumber in the lower chords of trusses. The standard establishes practicesthat will permit correlation of results from different sources through the use of a uniform procedure.Provision is ma
6、de for varying the procedure to take account of special problems.1. Scope1.1 These test methods cover the evaluation of lumber instructural size by various testing procedures.1.2 The test methods appear in the following order:SectionsFlexure 4-11Compression (Short Column) 13-20Compression (Long Memb
7、er) 21-28Tension 29-36Torsion 37-44Shear Modulus 45-521.3 Notations 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
8、 provided for 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
9、-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D9 Terminology Relating to Wood and Wood-Based Prod-uctsD 1165 Nomenclature of Commercial Hardwoods and Soft-woodsD 2395 Test Methods for Specific Gravity of Wood andWood-Based MaterialsD 2915 Practice for Eval
10、uating 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-Base MaterialsE4 Practices for Force Verification of Testing Mach
11、inesE6 Terminology Relating to Methods of Mechanical Test-ingE83 Practice for Verification and Classification of Exten-someter SystemsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study to1These test methods are under the j
12、urisdiction of ASTM Committee D07 onWood and are the direct responsibility of Subcommittee D07.01 on FundamentalTest Methods and Properties.Current edition approved Oct. 1, 2008. Published November 2008. Originallyapproved in 1924. Last previous edition approved in 2005 as D 198 05a.2For referenced
13、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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
14、ohocken, PA 19428-2959, United States.Determine the Precision of a Test Method3. Terminology3.1 DefinitionsSee Terminology E6, Terminology D9,and Nomenclature D 1165. A few related terms not covered inthese standards are as follows:3.1.1 composite wood beama laminar construction com-prising a combin
15、ation of wood and other simple or complexmaterials assembled and intimately fixed in relation to eachother so as to use the properties of each to attain specificstructural advantage for the whole assembly.3.1.2 depth of beamthat dimension of the beam that isperpendicular to the span and parallel to
16、the direction in whichthe load is applied (Fig. 1).3.1.3 shear spantwo times the distance between a reac-tion and the nearest load point for a symmetrically loaded beam(Fig. 1).3.1.4 shear span-depth ratiothe numerical ratio of shearspan divided by beam depth.3.1.5 spanthe total distance between rea
17、ctions on which abeam is supported to accommodate a transverse load (Fig. 1).3.1.6 span-depth ratiothe numerical ratio of total spandivided by beam depth.3.1.7 structural wood beamsolid wood, laminated wood,or composite structural members for which strength or stiff-ness, or both are primary criteri
18、a for the intended applicationand which usually are used in full length and in cross-sectionalsizes greater than nominal 2 by 2 in. (38 by 38 mm).FLEXURE4. Scope4.1 This test method covers the determination of the flexuralproperties of structural beams made of solid or laminatedwood, or of composite
19、 constructions. This test method isintended primarily for beams of rectangular cross section but isalso applicable to beams of round and irregular shapes, such asround posts, I-beams, or other special sections.5. Summary of Test Method5.1 The structural member, usually a straight or a slightlycamber
20、ed beam of rectangular cross section, is subjected to abending moment by supporting it near its ends, at locationscalled reactions, and applying transverse loads symmetricallyimposed between these reactions. The beam is deflected at aprescribed rate, and coordinate observations of loads anddeflectio
21、ns are made until 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 working stresses forstructural members;6.1.3 Data on the influence of i
22、mperfections 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 of beams;6.1.6 Data on the effects of chemical o
23、r 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.6.2 Procedures are described here in sufficient detail toper
24、mit duplication in different laboratories so that comparisonsof results from different sources will be valid. Special circum-stances may require deviation from some details of theseFIG. 1 Flexure Test MethodExample of Two-Point LoadingD198082procedures. Any variations shall be carefully described in
25、 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 beam, and (3)aforce-measuring device t
26、hat 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 beam shall be sup-ported by metal bearing plates to prevent damage to the beamat the point of contact between be
27、am and 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 beam.7.2.2 Reaction SupportsThe bearing plates shall be sup-ported by devices that provide unrestricted longitud
28、inal defor-mation and rotation of the beam at the reactions due to loading.Provisions shall be made to restrict horizontal translation of thebeam (see 7.3.1 and Appendix X5).7.2.3 Reaction Bearing AlignmentProvisions shall bemade at the reaction supports to allow for initial twist in thelength of th
29、e beam. If the bearing surfaces of the beam at itsreactions are not parallel, the beam shall be shimmed or theindividual bearing plates shall be rotated about an axis parallelto the span to provide full bearing across the width of thespecimen. Supports with lateral self-alignment are normallyused (F
30、ig. 2).7.2.4 Lateral SupportSpecimens that have a depth-to-width ratio of three or greater are subject to lateral instabilityduring loading, thus requiring lateral support. Support shall beprovided at least at points located about halfway between areaction and a load point. Additional supports may b
31、e used asrequired. Each support shall allow vertical movement withoutfrictional restraint but shall restrict lateral displacement (Fig.3).7.3 Load ApparatusDevices that transfer load from thetesting machine at designated points on the specimen. Provi-sions shall be made to prevent eccentric loading
32、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 extending entirely across the beam width to eliminatehigh-stress concentrations at places of contact between beamand bearing blocks.
33、 Load shall be applied to the blocks in sucha manner that the blocks may rotate about an axis perpendicu-lar to the span (Fig. 4). To prevent beam deflection withoutrestraint in case of two-point loading, metal bearing plates androllers shall be used in conjunction with one or both load-bearing bloc
34、ks, depending on the reaction support conditions(see Appendix X5). Provisions such as rotatable bearings orshims shall be made to ensure full contact between the beamand the loading blocks. The size and shape of these loadingblocks, plates, and rollers may vary with the size and shape ofthe beam, as
35、 well as for the reaction bearing plates andsupports. For rectangular beams, the loading surface of theblocks shall have a radius of curvature equal to two to fourtimes the beam depth. Beams having circular or irregularcross-sections shall have bearing blocks that distribute the loaduniformly to the
36、 bearing surface and permit unrestraineddeflections.7.3.2 Load PointsLocation of load points relative to thereactions depends on the purpose of testing (seeAppendix X5).7.3.2.1 Two-Point LoadingThe total load on the beamshall be applied equally at two points equidistant from thereactions. The two lo
37、ad points will normally be at a distancefrom their reaction equal to one third of the span (third-pointloading), but for special purposes other distances may bespecified.7.3.2.2 Center-Point LoadingIf required, a single loadcan be applied at mid-span.7.3.2.3 For evaluation of shear properties, cente
38、r-point load-ing or two-point loading shall be used (see Appendix X5).7.4 Deflection-Measuring Apparatus:7.4.1 GeneralFor modulus of elasticity calculations, de-vices shall be provided by which the deflection of the neutralaxis of the beam at the center of the span is measured withrespect to a strai
39、ght line joining two reference points equidis-tant from the reactions and on the neutral axis of the beam.7.4.1.1 The apparent modulus of elasticity shall be calcu-lated using the full-span deflection. The reference points for thefull-span deflection measurements shall be positioned such thata line
40、perpendicular to the neutral axis at the location of thereference point, passes through the supports center of rotation.FIG. 2 Example of Bearing Plate (A), Rollers (B), and Reaction-Alignment-Rocker (C), for Small BeamsD1980837.4.1.2 The true or shear-free modulus of elasticity shall becalculated u
41、sing the shear-free deflection. The reference pointsfor the shear-free deflection measurements shall be positionedat cross-sections free of shear and stress concentrations (seeAppendix X5).NOTE 1The apparent modulus of elasticity may be corrected forshear-corrected MOE calculations, assuming that th
42、e shear modulus isknown. See Appendix X5.7.4.2 Wire DeflectometerDeflection may be read directlyby means of a wire stretched taut between two nails driven intothe neutral axis of the beam directly above the reactions andextending across a scale attached at the neutral axis of the beamat midspan. Def
43、lections may be read with a telescope orreading glass to magnify the area where the wire crosses thescale. When a reading glass is used, a reflective surface placedadjacent to the scale will help to avoid parallax.7.4.3 Yoke DeflectometerA satisfactory device commonlyused for short, small beams or t
44、o measure deflection of thecenter of the beam with respect to any point along the neutralaxis consists of a lightweight U-shaped yoke suspendedbetween nails driven into the beam at its neutral axis and a dialmicrometer attached to the center of the yoke with its stemattached to a nail driven into th
45、e beam at midspan at the neutralaxis. Further modification of this device may be attained byreplacing the dial micrometer with a deflection transducer forautomatic recording (Fig. 4).7.4.4 Alternative DeflectometersDeflectometers that donot conform to the general requirements of 7.4.1 are permittedp
46、rovided the mean deflection measurements are not signifi-cantly different from those devices conforming to 7.4.1. Theequivalency of such devices to deflectometers, such as thosedescribed in 7.4.2 or 7.4.3, shall be documented and demon-strated by comparison testing.NOTE 2Where possible, equivalency
47、testing should be undertaken inthe same type of product and stiffness range for which the device will beused. Issues that should be considered in the equivalency testing includethe effect of crushing at and in the vicinity of the load and reaction points,twist in the specimen, and natural variation
48、in properties within aspecimen.7.4.5 AccuracyThe devices and recording system shall besuch as to permit measuring changes in deflection to threesignificant figures. Since gauge lengths vary over a wide range,the measuring instruments should conform to their appropriateclass in accordance with Practi
49、ce E83.NOTE 3A more accurate device may be required if the methodselected for computing the slope of the linear portion of the load-deflection response curve does not permit three or more significant figuresto be maintained in the calculations.8. Test Specimen8.1 MaterialThe test specimen shall consist of a structuralmember, which may be solid wood, laminated wood, or aFIG. 3 Example of Lateral Support for Long, Deep BeamsFIG. 4 Example of Curved Loading Block (A), Load-AlignmentRocker (B), Roller-Curved Loading Block (C), Load Evener (D),and Deflecti
