1、Designation: D 2719 89 (Reapproved 2007)Standard Test Methods forStructural Panels in Shear Through-the-Thickness1This standard is issued under the fixed designation D 2719; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、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 These test methods determine the shear through-the-thickness properties of structural panels associated with shear
3、distortion of the major axis. Structural panels in use includeplywood, wafer board, oriented strand board, and compositesof veneer and of wood based layers. Three test methods areincluded which differ somewhat in their application:Test Method SectionA. Small Panel Shear Test 5B. Large Panel Shear Te
4、st 6C. Two Rail Shear Test 7The choice of test method will be determined in part by thepurpose of the tests, characteristics of test material, andequipment availability. In general, Test Method B or C for largespecimens is preferred when equipment, amount of test mate-rial, and experimental plan per
5、mit.1.1.1 Test Method A: Small Panel Shear TestThis testmethod is suitable for testing small samples of uniformmaterial including investigations of the effects of grain direc-tion or orientation and of many raw materials and manufactur-ing process variables which influence shear properties uni-forml
6、y throughout the specimen. The test method is unsuitedfor determining effects of grade and manufacturing featuressuch as density variations, knots, and core gaps within thespecimen.1.1.2 Test Method B: Large Panel Shear TestThis testmethod is regarded as giving the most accurate modulus ofrigidity a
7、nd is therefore recommended for elastic tests ofmaterials to be used in stress analysis studies of test structures.This test method also yields excellent shear strength values forclear material. However, in spite of the large size of thespecimen, failures generally occur only in narrow zones at thep
8、erimeter of the test area. This characteristic, a result of theheavy perimeter framing, causes this test method to be gener-ally unsuited for determining grade and manufacturing effectssuch as density variations, core gaps, and knots that are notuniformly distributed throughout the panel. Generally,
9、 only incases where effects of these factors under conditions of heavyperimeter framing are desired, should the test method beapplied.1.1.3 Test Method C: Two-Rail Shear TestThis testmethod is applicable to a wide variety of materials andproblems. The specimen fabrication and test procedures aresome
10、what simpler than in Test MethodsAand B. The specimenis free to shear parallel to its 24-in.(610-mm) length dimensionanywhere within the 8-in. (203-mm) width between rails. Thus,the test method is well suited for determining grade andmanufacturing effects such as core gaps and knots occupyingand aff
11、ecting small areas. The test method is not so ideallysuited for determination of modulus of rigidity, but whenadjusted for strain distribution effects, values approximatingthose obtained by Test Method B result. The test methodsimulates effects of heavy framing when expected planes ofweakness are or
12、iented perpendicular to rails and no framing atall when parallel to rails.1.2 Significant differences, moderate to small in magnitude,among the three test methods have been found to exist whenthese test methods are applied to plywood of clear straight-grained veneers. Therefore, when comparisons are
13、 madeamong test results, it is recommended that the same testmethod be used throughout.1.3 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
14、and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 2395 Test Methods for Specific Gravity of Wood andWood-Based MaterialsD 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base Materials3. Significance and U
15、se3.1 The strength and modulus of rigidity of structural panelsin shear through-the-thickness obtained by these test methodsare required for the rigorous design of many lumber-panelstructural components such as trusses with panel gussets, box1These test methods are under the jurisdiction of ASTM Com
16、mittee D07 onWood and are the direct responsibility of Subcommittee D07.03 on Panel Products.Current edition approved April 1, 2007. Published April 2007. Originallyapproved in 1969. Last previous edition approved in 2001 as D 2719 89 (2001).2For referenced ASTM standards, visit the ASTM website, ww
17、w.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 Conshohocken, PA 19428-2959, United States.beam
18、s, folded plate roofs, and space plane structures, as well asfloor and roof diaphragms, and shear walls. These propertiesare of secondary importance in typical roof deck and sheathingapplications, and in crates and shipping containers.3.2 Veneer produced by slicing or rotary peeling maycontain fine
19、checks or separations parallel to the grain on theknife side of the veneer that are produced as the knife is forcedthrough the wood. These checks are termed “knife checks” todistinguish them from occasional checks that may be formedon the opposite side of the veneer by forces at the compressionbar,
20、and from checks caused by drying. Average depth of knifechecks has been found to strongly influence shear properties inplywood panels and may be of significance in veneer incorpo-rated in composite panels. Measurement of depth of knifechecks is recommended in these test methods.3.3 To control or def
21、ine other variables influencing shearproperties, these test methods require determination of mois-ture content and elapsed time to failure. The conditioning oftest material in controlled atmosphere and determination ofspecific gravity are recommended.4. Control of Moisture Content4.1 Structural pane
22、l samples to be tested at a specifictemperature/relative humidity shall be conditioned to approxi-mate constant weight in controlled atmospheric conditionsbefore gluing wood rails. Conditioning of fabricated specimensat the same temperature and relative humidity shall be contin-ued until the adhesiv
23、e has cured sufficiently to ensure adequatebond strength. For approximating moisture conditions of struc-tural panels used under dry conditions, a relative humidity of65 6 2 % at a temperature of 68 6 6F (20 6 3C) isrecommended.5. Test Method ASmall Panel Shear Test5.1 SummaryA specimen having a squ
24、are shear areabounded on each side by solid wood blocks glued to both sidesof the specimen is loaded in compression along one diagonal ina conventional testing machine. Forces are applied to theglued-on blocks through a roller bracket assembly whichcauses the resultant forces to act collinearly with
25、 the edge ofthe shear test area. This loading method most nearly producesuniform pure shear. Shear strength is determined from maxi-mum load, and modulus of rigidity may be calculated frommeasurements of compression strain along the compressiondiagonal of the specimen.5.2 Test SpecimenDimensions sho
26、wn in Fig. 1 of thepanel specimen and reinforcing blocks depend upon panelthickness. Distance between blocks, L, shall not exceed 20times specimen thickness, and block width and thickness shallnot be less than 5 and 2.5 times specimen thickness, respec-tively. Reinforcing blocks shall be of birch, m
27、aple, or otherwood of similar strength and rigidity. The average of specimenthickness at two diagonally opposite corners and the dimen-sions of the shear area inside the reinforcing blocks shall bedetermined and recorded to the nearest 0.3 % or 0.001 in.(0.025 mm), whichever is larger.5.3 LoadingApp
28、ly the load by special steel loadingblocks which articulate with the rollers and pins attached to thetest specimen. The angle between faces of the loading blockshall be 90 and between each face and the base the angle shallbe 45. A spherical bearing block, preferably of the suspended,self-aligning ty
29、pe, shall be employed in the loading system.Apply the load continuously throughout the test with a uniformmotion of the movable head of the testing machine equal to0.0025 in./in. of test area diagonal length/min (0.0025 mm/mm/min) corresponding to a shear strain rate of 0.005 in./in./min (0.005 mm/m
30、m/min) within a permissible variation of625 %.5.3.1 Load each of the eight reinforcing blocks throughroller brackets clamped to the reinforcing block across itswidth or attached by other means and applying a compressiveforce to the end of the reinforcing block through a surfacecontact area of at lea
31、st 0.75 in.2(484 mm2). These bearingsurfaces shall be firmly seated against the ends of theirrespective reinforcing blocks during assembly. Rollers shall becentered at the inner edge of the reinforcing block and 1.25 in.(31.8 mm) from the loaded end of the reinforcing block.Moderate clamping pressur
32、e holding brackets to the reinforc-ing blocks applied perpendicular to the plane of the panel ispermitted but shall not be excessive.5.3.1.1 Fig. 2 illustrates detail of suitable roller brackets andtheir method of attachment to the reinforcing blocks with smallwood wedges. Fig. 3 shows a specimen lo
33、aded by means ofroller brackets, and Fig. 4 gives working drawings for thesebrackets. Brackets are clamped across the width of the rein-forcing blocks by driving small wedges between a projectionon the bracket and the reinforcing block. The clamping bolt isused to apply moderate clamping pressure pe
34、rpendicular to theplane of the specimen. Other bracket devices conforming to therequirements of 5.3.1 are permitted but shall be described indetail in the report of test results.5.3.1.2 Measure the elapsed time from initiation of loadingto the maximum load and record to the nearest12 min.5.4 Measure
35、ment of DeformationWhen deformation dataare desired for calculation of elastic properties, strain-measuring devices having minimum gage length of 1 in. (25mm) shall be attached to both sides of the specimen and shallmeasure compression strain of the vertical (or compression)diagonal, the gages being
36、 centered at its midpoint on each side.A larger gage length is preferred but shall not exceed one halfthe length of the diagonal. Instruments and the accuracy oftheir recording shall be to the nearest 0.0001 in. (0.0025 mm)Metric Equivalentsin.mm1161.61212.7FIG. 1 Small Panel Shear Specimen and Dime
37、nsionsD 2719 89 (2007)2or 2 % of expected ultimate strain, whichever is smaller. Strainreadings of the two gages shall be averaged for computation ofelastic properties.5.5 Calculation:5.5.1 Calculate the maximum shear stress or shear stress atthe proportional limit as follows:T 5 0.707 P/Lt! (1)wher
38、e:T = shear stress, psi (N/m2),P = load (force), lbf (N),L = length of side of shear area, in. (m), (Fig. 1), andt = thickness of shear specimen, in. (m).5.5.2 Calculate modulus of rigidity from deformation dataas follows:G 5 0.3536 P/D!L1/L t! (2)where:G = modulus of rigidity, psi (N/m2),P/D = slop
39、e of force/deformation curve, lbf/in. (N/m),L1= gage length, in. (m), andt = thickness of shear specimen, in. (m).6. Test Method BLarge Panel Shear Test6.1 SummaryA specimen having a square shear area isloaded through heavy lumber rails glued to both sides of thespecimen at all four edges of the she
40、ar area. Loading by asystem of pins and yokes applies forces to the rails having aresultant acting at the inside edge of the shear area. Maximumshear strength is determined from maximum load and modulusof rigidity from elongation of the tension diagonal and corre-sponding loads.6.2 Test SpecimensFig
41、. 5 gives detail of the specimen aswell as a suitable loading method. Shear area of the specimenshall not be less than 24 in. (610 mm) on a side, and shall notexceed 48 times total specimen thickness. When structuralpanels less than12 in. (12.7 mm) thick or less than148 the sideof the shear area is
42、to be tested for shear strength, two or morethicknesses of structural panels may be glued together (majoraxis parallel) to form a test panel of the required thickness.Specimens to be tested for modulus of rigidity only may be oflesser thickness provided sufficient data can be obtained beforethe test
43、 is halted due to initiation of buckling. Lumber railshaving a length equal to the side of the shear area, thickness notless than125 and width not less than16 the length of one sideof the shear area shall be glued to the structural panels with arigid adhesive. Wider rails may be necessary to prevent
44、 rollingshear failures between thick or high-strength panels and therails. Corners of the structural panels specimen shall benotched with the inside corner of the notch provided with afillet of12-in. (12.7-mm) radius as shown in Fig. 5. Ends of theFIG. 2 Small Panel Shear Specimen with Roller Bracke
45、tsD 2719 89 (2007)3rails to which loads are applied shall form a flat planeperpendicular to the plane of the specimen. Use of a jig toposition rails accurately at the time of assembly or a light sawcut across the end of both rails after assembly may be helpful.Depending upon the method of deformatio
46、n measurement,holes for gage pins may be needed as illustrated in Fig. 5.Average specimen thickness shall be determined from mea-surements at each corner of the shear area to an accuracy of0.001 in. (0.025 mm). Width and length of the shear area shallbe measured to an accuracy of 0.01 in. (0.25 mm).
47、6.3 LoadingLoad the specimen loading jig assembly intension. The resultant of forces applied to a pair of rails shallbe a single force acting at, and parallel to, the edge of the sheararea. If the ends of rails are compression loaded, the jigs shallrestrain any tendency for the rails to deflect late
48、rally from theplane of the specimen. Fig. 6 shows the loading forces, theirresultants, and their components. Any lateral forces applied tothe rails parallel to the plane of the specimen or any lateralcomponent parallel to the plane of the specimen of a forceapplied to the rails shall not exceed18 of
49、 the axial forcecomponent.6.3.1 Suitable loading equipment is illustrated in Fig. 5 andFig. 7. Major compression forces are applied by yokes to theends of the rails at a slight angle to the rail axis through bearingplates. At its other end, a pin having a notched end centers thepin and yoke over the inside edge of the rail. Forces acting at,and parallel to, the inner edge of the rail are applied to thesepins by short links. At its other end, the link connects to a pincentered at the corner of the shear area to which the linkloading the adjacent rail i
