ASTM D198-2005a Standard Test Methods of Static Tests of Lumber in Structural Sizes《结构尺寸木料静力学试验的标准试验方法》.pdf

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1、Designation: D 198 05aStandard 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 (e) 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 impor

3、tance 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 prestresse

4、d 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

5、 for 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

6、made 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) 12-19Compression (Long Me

7、mber) 20-27Tension 28-35Torsion 36-43Shear Modulus 44-511.3 Notations and symbols relating to the various testingprocedures are given in Appendix X1.1.4 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 s

8、tandard 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:2D9 Terminology Relating to WoodD 1165 Nomenclature of Domestic Hardwoods and Soft-woodsD 2395 Test Methods for Specific Gra

9、vity of Wood andWood-Based MaterialsD 2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods

10、of Mechanical Test-ingE83 Practice for Verification and Classification of Exten-someter System3. 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-

11、prising a combination 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

12、and parallel to 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).1These test methods are under the jurisdiction of ASTM Committee D07 onWood and are the direct responsibili

13、ty of Subcommittee D07.01 on FundamentalTest Methods and Properties.Current edition approved Oct. 1, 2005. Published October 2005. Originallyapproved in 1924. Last previous edition approved in 2005 as D 198 05.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custo

14、mer 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 Conshohocken, PA 19428-2959, United States.3.1.4 shear span-depth ratiothe nume

15、rical ratio of shearspan divided by beam depth.3.1.5 spanthe total distance between reactions 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 com

16、posite structural members for which strength or stiff-ness, or both are primary criteria 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

17、 flexuralproperties of structural beams made of solid or laminatedwood, or of composite 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.

18、Summary of Test Method5.1 The structural member, usually a straight or a slightlycambered 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 b

19、eam is deflected at aprescribed rate, and coordinate observations of loads anddeflections 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

20、 development of working stresses forstructural 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-es

21、es relating to the structural behavior of beams,6.1.6 Data 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 mechanica

22、l and physi-cal properties.6.2 Procedures are described here in sufficient detail topermit duplication in different laboratories so that comparisonsof results from different sources will be valid. Special circum-stances may require deviation from some details of theseprocedures. Any variations shall

23、 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 beam, and (3

24、)aforce-measuring device that is calibrated to ensure accuracy inaccordance with Practices E 4.7.2 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

25、point of contact between beam 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.FIG. 1 Flexure Method. Example of Two-Point LoadingD 198 05a27.2.2 Reaction Supp

26、ortsThe bearing plates shall be sup-ported by devices that provide unrestricted longitudinal 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 AlignmentProvis

27、ions shall bemade at the reaction supports to allow for initial twist in thelength of the 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 a

28、cross the width of thespecimen. Supports with lateral self-alignment are normallyused (Fig. 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 po

29、ints located about halfway between areaction and a load point. Additional supports may be 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 de

30、signated 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 extending entirely across the beam width to

31、eliminatehigh-stress concentrations at places of contact between beamand bearing blocks. 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 b

32、earing plates androllers shall be used in conjunction with one or both load-bearing blocks, 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

33、these loadingblocks, plates, and rollers may vary with the size and shape ofthe beam, as 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 ir

34、regularcross-sections shall have bearing blocks that distribute the loaduniformly to the 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

35、the beamshall 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 the span (third-pointloading), but for special purposes other distances may bespecified.7.3.2.2 Center-Point LoadingIf required, a

36、 single loadcan be applied 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 Deflection-Measuring Apparatus:7.4.1 GeneralFor modulus of elasticity calculations, de-vices shall be provided by which the deflection of

37、the neutralaxis of the beam at the center of the span is measured withrespect to a straight 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 refere

38、nce points for thefull-span deflection measurements shall be positioned such thata line perpendicular to the neutral axis at the location of thereference point, passes through the supports center of rotation.7.4.1.2 The true or shear-free modulus of elasticity shall becalculated using the shear-free

39、 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 the shear modulus isk

40、nown. 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. Deflections may be rea

41、d 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 to measure deflectio

42、n 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 dialFIG. 2 Example of Bearing Plate (A), Rollers (B), and Reaction-Alignment-Rocker (C), for Small BeamsD 198 05a3m

43、icrometer attached to the center of the yoke with its stemattached to a nail driven into the 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 Deflecto

44、metersDeflectometers that donot conform to the general requirements of 7.4.1 are permittedprovided 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, sha

45、ll be documented and demon-strated by comparison testing.NOTE 2Where possible, equivalency 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

46、 the vicinity of the load and reaction points,twist in the specimen, and natural variation 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,t

47、he measuring instruments should conform to their appropriateclass in accordance with Practice 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

48、 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 acomposite construction of wood or of wood combined withplastics or metals in sizes that are usually used in structuralapplications.8.2 Id

49、entificationMaterial or materials of the test speci-men shall be identified as fully as possible by including theorigin or source of supply, species, and history of drying andconditioning, chemical treatment, fabrication, and other perti-nent physical or mechanical details that may affect the strength.Details of this information shall depend on the material ormaterials in the beam. For example, the solid wooden beamswould be identified by the character of the wood, that is,species, source, and so forth, whereas composite woodenbeams would be identifi