ASTM D2555-2006 Standard Practice for Establishing Clear Wood Strength Values《建立无结疤木材强度值的标准规范》.pdf
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1、Designation: D 2555 06Standard Practice forEstablishing Clear Wood Strength Values1This standard is issued under the fixed designation D 2555; 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 p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe development of safe and efficient working stresses for lumber, laminated timber, plywood,round timbers, and other solid wood products, each w
3、ith its own special requirements has, as acommon starting point, the need for an authoritative compilation of clear wood strength values for thecommercially important species.Also required are procedures for establishing, from these data, valuesapplicable to groups of species or to regional grouping
4、s within a species where necessitated bymarketing conditions. This standard has been developed to meet these needs and to provide, inaddition, information on factors for consideration in the adjustment of the clear wood strength valuesto the level of working stresses for design. Since factors such a
5、s species preference, species groupings,marketing practices, design techniques, and safety factors vary with each type of product and end use,it is contemplated that this standard will be supplemented where necessary by other appropriatestandards relating to specific work stresses for each such prod
6、uct. Practice D 245 is an example of sucha standard applicable to the interpretation of the clear wood strength values in terms of workingstresses for structural lumber.A primary feature of this practice is the establishment of tables presenting the most reliable basicinformation developed on the st
7、rength of clear wood and its variability through many years of testingand experience. The testing techniques employed are those presented in Test Methods D 143. Amongthe recognized limitations of such strength data are those resulting from the problems of samplingmaterial from forests extending over
8、 large regions, and the uneconomical feasibility of completelytesting an intensive sample. A practical approach to the improvement of strength data is through theapplication of the results of density surveys in which the specific gravity of the entire forest stand foreach species is determined on a
9、sound statistical basis. Through regression equations derived frompresently available strength data, revised strength values are established from the specific gravity-strength relationship for clear wood. This procedure greatly extends current capabilities to developnew estimates of strength and to
10、improve or verify estimates made in the past.1. Scope1.1 This practice covers the determination of strength valuesfor clear wood of different species in the unseasoned condition,unadjusted for end use, applicable to the establishment ofworking stresses for different solid wood products such aslumber
11、, laminated wood, plywood, and round timbers. Pre-sented are:1.1.1 Procedures by which test values obtained on smallclear specimens may be combined with density data fromextensive forest surveys to make them more representative,1.1.2 Guidelines for the interpretation of the data in terms ofassigned
12、values for combinations of species or regional divi-sions within a species to meet special marketing needs, and1.1.3 Information basic to the translation of the clear woodvalues into working stresses for different solid wood productsfor different end uses.1.1.4 For species where density survey data
13、are not as yetavailable for the re-evaluation of average strength properties,the presently available data from tests made under the samplingmethods and procedures of Test Methods D 143 or PracticeE 105 are provided with appropriate provision for their appli-cation and use. Because of the comprehensi
14、ve manner in whichthe density survey is undertaken, it follows that the re-evaluated strength data are intended to be representative of theforest stand, or rather large forest subdivisions.1This practice is under the jurisdiction of ASTM Committee D07 on Wood andare the direct responsibility of Subc
15、ommittee D07.01 on Fundamental Test Methodsand Properties.Current edition approved March 1, 2006. Published March 2006. Originallyapproved in 1966. Last previous edition approved in 2005 as D 2555 05a.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959
16、, United States.1.1.5 Some useful mechanical properties (tensile strengthsparallel and perpendicular to grain and modulus of rigidity fora longitudinal-transverse plane) have not been extensivelyevaluated. Methods are described for estimating these proper-ties by their relation to other properties.1
17、.2 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-bility of regulatory limitations prior to use.2. Referenced Do
18、cuments2.1 ASTM Standards:2D 143 Test Methods for Small Clear Specimens of TimberD 245 Practice for Establishing Structural Grades and Re-lated Allowable Properties for Visually Graded LumberD 2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberE 105 Practice for Probabil
19、ity Sampling Of Materials3. Summary of Methods3.1 Two methods are presented for establishing tables ofclear wood strength properties for different species and re-gional subdivisions thereof in the unseasoned condition andunadjusted for end use. These are designated Method A andMethod B.3.1.1 MethodA
20、provides for the use of the results of surveysof wood density involving extensive sampling of forest trees,in combination with the data obtained from standard strengthtests made in accordance with Test Methods D 143. Theaverage strength properties are obtained from wood densitysurvey data through li
21、near regression equations establishing therelation of specific gravity to the several strength properties.NOTE 1Density surveys have been completed for only a limitednumber of species. Data are thus not currently available for the use ofMethod A on all commercial species. As such data become availab
22、le theywill be incorporated in revisions of this practice.3.1.2 Method B provides for the establishment of tables ofstrength values based on standard tests of small clear speci-mens in the unseasoned condition for use when data fromdensity surveys are not available. Separate tables are employedto pr
23、esent the data on woods grown in the United States and onwoods grown in Canada.4. Procedure for Establishing Clear Wood StrengthValues4.1 Method ASix steps are involved in establishingstrength values by the wood density survey procedure. Theseare: conducting the wood density survey, development of u
24、nitareas, determination of average specific gravity for a unit area,determination of strength-specific gravity relations, estimationof average strength properties for a unit area, and combiningvalues for unit areas into basic groups and establishing averagestrength properties and estimates of varian
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