1、Designation:D255517aStandard Practice forEstablishing Clear Wood Strength Values1This standard is issued under the fixed designation D2555;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 parenthe
2、ses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe development of safe and efficient design values for lumber,laminated timber,plywood,roundtimbers,and other solid wood products,each with its own special
3、 requirements has,as a commonstarting 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 groupings within a species wher
4、e necessitated bymarketing conditions.This practice 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 design values for engineering.Since factors such as species preference,species groupings
5、,marketing practices,design techniques,and safety factors vary with each type of product and end use,it is contemplated that this practice will be supplemented where necessary by other appropriatestandards relating to specific design values for each such product.Practice D245 is an example of sucha
6、standard applicable to the interpretation of the clear wood strength values in terms of allowableproperties for visually graded lumber.A primary feature of this practice is the establishment of tables presenting the most reliable basicinformation developed on the strength of clear wood and its varia
7、bility through many years of testingand experience.The testing techniques employed are those presented in Test Methods D143.Amongthe recognized limitations of such strength data are those resulting from the problems of samplingmaterial from forests extending over large regions,and the uneconomical f
8、easibility 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 sound statistical basis.Through regress
9、ion 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 improve or verify estimates made in the pa
10、st.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 ofdesign values for different solid wood products such as lumber,laminated wood,plywood,and round timbers.Pres
11、ented 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 values for combinations of species or regional divi
12、-sions within a species to meet special marketing needs,and1.1.3 Information basic to the translation of the clear woodvalues into design values for different solid wood products fordifferent end uses.1.1.4 For species where density survey data are not as yetavailable for the re-evaluation of averag
13、e strength properties,the presently available data from tests made under the samplingmethods and procedures of Test Methods D143 or PracticeE105 are provided with appropriate provision for their appli-cation and use.Because of the comprehensive manner in whichthe density survey is undertaken,it foll
14、ows that the re-evaluated strength data are intended to be representative of theforest stand,or rather large forest subdivisions.1.1.5 Some useful mechanical properties(tensile strengthsparallel and perpendicular to grain,modulus of rigidity for a1This practice is under the jurisdiction of ASTM Comm
15、ittee D07 on Wood andare the direct responsibility of Subcommittee D07.02 on Lumber and EngineeredWood Products.Current edition approved Aug.1,2017.Published October 2017.Originallyapproved in 1966.Last previous edition approved in 2017 as D2555 17.DOI:10.1520/D2555-17A.Copyright ASTM International,
16、100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 longitudinal-transverse plane,and transverse modulus of elas-ticity)have not been extensively evaluated.M
