1、Designation:D255515Standard 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 parenthes
2、es indicates the year of last reapproval.Asuperscript epsilon()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 with its own spec
3、ial 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 groupings within a species w
4、here 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 as species preference,spe
5、cies 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 product.Practice D245 is an exa
6、mple 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 strength of clear wood and its
7、variability 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 uneconomi
8、cal 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 sound statistical basis.Through re
9、gression 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 t
10、he 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,laminated wood,plywood,and round timbe
11、rs.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 values for combinations of species or regio
12、nal 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 are not as yetavailable for the re-evaluatio
13、n of average 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 underta
14、ken,it follows 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 o
15、f ASTM Committee D07 on Wood andare the direct responsibility of Subcommittee D07.01 on Fundamental Test Methodsand Properties.Current edition approved Sept.1,2015.Published December 2015.Originallyapproved in 1966.Last previous edition approved in 2011 as D2555 06(2011).DOI:10.1520/D2555-15.Copyrig
16、ht ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 longitudinal-transverse plane,and transverse modulus of elas-ticity)have not been extensively evaluated.Methods aredescribed for estimating these properties by their relation toother properties.1.2 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 pra
