1、BS EN 338:2009ICS 79.040NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDStructural timber Strength classesCopyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license
2、 from IHS-,-,-This British Standardwas published under theauthority of the StandardsPolicy and StrategyCommittee on 31 March2010 BSI 2010ISBN 978 0 580 58144 1Amendments/corrigenda issued since publicationDate CommentsBS EN 338:2009National forewordThis British Standard is the UK implementation of E
3、N 338:2009. Itsupersedes BS EN 338:2003 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee B/518, Structural timber.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to includ
4、e all the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or netwo
5、rking permitted without license from IHS-,-,-BS EN 338:2009EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 338 October 2009 ICS 79.040 Supersedes EN 338:2003English Version Structural timber - Strength classes Bois de structure - Classes de rsistance Bauholz fr tragende Zwecke - Festigkeitsklas
6、sen This European Standard was approved by CEN on 29 September 2009. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographic
7、al references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN
8、 member into its own language and notified to the CEN Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, It
9、aly, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-10
10、00 Brussels 2009 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 338:2009: ECopyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without licens
11、e from IHS-,-,-BS EN 338:2009EN 338:2009 (E) 2 Content page Foreword 3Introduction . 41 Scope 52 Normative references 53 Terms and definitions . 54 Symbols and abbreviations 55 Classification of structural timber . 66 Allocation of a timber population to a strength class 86.1 Grading . 86.1.1 Visual
12、ly graded timber 86.1.2 Machine graded timber . 86.2 Classification 86.2.1 Characteristic values . 86.2.2 Allocation to a strength class . 8Annex A (informative) Determination of values in addition to bending strength, stiffness and density . 9Bibliography 10Copyright European Committee for Standard
13、ization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN 338:2009EN 338:2009 (E) 3 Foreword This document (EN 338:2009) has been prepared by Technical Committee CEN/TC 124 “Timber structures”, the secretariat of which is h
14、eld by SFS. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by April 2010, and conflicting national standards shall be withdrawn at the latest by April 2010. Attention is drawn to the possibility tha
15、t some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 338:2003. According to the CEN/CENELEC Internal Regulations, the national standards organizations o
16、f the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slo
17、vakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN 338:2009EN 338:2009 (E) 4 Introduction This European Sta
18、ndard has additional strength classes which are more suitable to the characteristic values of temperate hardwoods. It also has modified characteristic values for the softwood classes for shear strength and tension strength perpendicular to grain. The equations given for these two properties in Annex
19、 A have been modified accordingly. Due to variations in the type and quality of timber available, the variety of end uses and the size of production output of the local timber industry, many different combinations of species and strength grade exist with different strength properties, which therefor
20、e complicate the design and specification of timber structures. A strength class system groups together grades and species with similar strength properties thus making them interchangeable. This then permits an engineer to specify a chosen strength class and use the characteristic strength values of
21、 that class in design calculations. Advantages of the strength class system are: a) Additional species/grades can be incorporated into the system at any time without affecting existing specifications for structural timber. b) At the time of carrying out design calculations, an engineer need not be a
22、ware of the costs and availability of alternative species and grades. He can simply design using the strength, stiffness and density values of a particular class and then specify that class; he can then use the tenders to select the most suitable and economic species/grade on offer. Note that, where
23、 a particular species is not acceptable (e.g. for reasons of durability) for a project, the specification needs to make this clear. c) Suppliers can offer their material to meet more specifications than would be possible if species and grades were specified. Copyright European Committee for Standard
24、ization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN 338:2009EN 338:2009 (E) 5 1 Scope This European Standard establishes a system of strength classes for general use in structural codes. It gives characteristic streng
25、th and stiffness properties and density values for each class and the rules for the allocation of timber populations (i.e. combinations of species, source and grade) to the classes. This standard is applicable to all softwood and hardwood timber for structural use. 2 Normative references The followi
26、ng referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 384, Structural timber Determination of characteristic va
27、lues of mechanical properties and density EN 14081 (all parts), Timber structures Strength graded structural timber with rectangular cross section 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 timber population timber for which the characte
28、ristic values are relevant NOTE The timber population is defined by parameters such as species or species grouping (combination of species), source and strength grade. 4 Symbols and abbreviations E0,meanmean characteristic value of modulus of elasticity parallel to grain (in kN/mm2) E0,055-percentil
29、e characteristic value of modulus of elasticity parallel to grain (in kN/mm2) E90,meanmean characteristic value of modulus of elasticity perpendicular to grain (in kN/mm2) fc,0,kcharacteristic value of compressive strength parallel to grain (in N/mm2) fc,90,kcharacteristic value of compressive stren
30、gth perpendicular to grain (in N/mm2) fm,kcharacteristic value of bending strength (in N/mm2) ft,0,kcharacteristic value of tensile strength parallel to grain (in N/mm2) f t,90,kcharacteristic value of tensile strength perpendicular to grain (in N/mm2) fv,kcharacteristic value of shear strength (in
31、N/mm2) Gmeanmean characteristic value of shear modulus (in kN/mm2) kcharacteristic value of density (in kg/m3) meanmean value of density (in kg/m3) Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without lic
32、ense from IHS-,-,-BS EN 338:2009EN 338:2009 (E) 6 5 Classification of structural timber This standard provides for a number of strength classes, each designated by a number indicating the value of bending strength in N/mm. The characteristic values of strength, stiffness and density for the strength
33、 classes are given in Table 1. Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN 338:2009EN 338:2009 (E) 7 Table 1 Strength classes - Characteristic values Softwood species H
34、ardwood species C14 C16 C18 C20 C22 C24 C27 C30 C35 C40 C45 C50 D18 D24 D30 D35 D40 D50 D60 D70 Strength properties (in N/mm2) Bending m,k14 16 18 20 22 24 27 30 35 40 45 50 18 24 30 35 40 50 60 70 Tension parallel t,0,k8 10 11 12 13 14 16 18 21 24 27 30 11 14 18 21 24 30 36 42 Tension perpendicular
35、 t,90,k0,4 0,4 0,4 0,4 0,4 0,4 0,4 0,4 0,4 0,4 0,4 0,4 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 Compression parallel c,0,k16 17 18 19 20 21 22 23 25 26 27 29 18 21 23 25 26 29 32 34 Compression perpendicular c,90,k2,0 2,2 2,2 2,3 2,4 2,5 2,6 2,7 2,8 2,9 3,1 3,2 7,5 7,8 8,0 8,1 8,3 9,3 10,5 13,5 Shear v,k3,0
36、3,2 3,4 3,6 3,8 4,0 4,0 4,0 4,0 4,0 4,0 4,0 3,4 4,0 4,0 4,0 4,0 4,0 4,5 5,0 Stiffness properties (in kN/mm2) Mean modulus E0,mean7 8 9 9,5 10 11 11,5 12 13 14 15 16 9,5 10 11 12 13 14 17 20 of elasticity parallel 5 % modulus of E0,054,7 5,4 6,0 6,4 6,7 7,4 7,7 8,0 8,7 9,4 10,0 10,7 8 8,5 9,2 10,1 10
37、,9 11,8 14,3 16,8 elasticity parallel Mean modulus E90,mean0,23 0,27 0,30 0,32 0,33 0,37 0,38 0,40 0,43 0,47 0,50 0,53 0,63 0,67 0,73 0,80 0,86 0,93 1,13 1,33 of elasticity perpendicular Mean shear modulus Gmean0,44 0,5 0,56 0,59 0,63 0,69 0,72 0,75 0,81 0,88 0,94 1,00 0,59 0,62 0,69 0,75 0,81 0,88
38、1,06 1,25 Density (in kg/m3)Density k290 310 320 330 340 350 370 380 400 420 440 460 475 485 530 540 550 620 700 900 Mean density mean350 370 380 390 410 420 450 460 480 500 520 550 570 580 640 650 660 750 840 1080 NOTE 1 Values given above for tension strength, compression strength, shear strength,
39、 5 % modulus of elasticity, mean modulus of elasticity perpendicular to grain and mean shear modulus, have been calculated using the equations given in Annex A. NOTE 2 The tabulated properties are compatible with timber at a moisture content consistent with a temperature of 20 C and a relative humid
40、ity of 65 %. NOTE 3 Timber conforming to classes C45 and C50 may not be readily available. NOTE 4 Characteristic values for shear strength are given for timber without fissures, according to EN 408. The effect of fissures should be covered in design codes. Copyright European Committee for Standardiz
41、ation Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN 338:2009EN 338:2009 (E) 8 6 Allocation of a timber population to a strength class 6.1 Grading 6.1.1 Visually graded timber Visually graded timber shall be to a grading
42、 standard that meets the requirements of EN 14081-1. NOTE EN 1912 lists a number of visual grades and species that are allocated to the strength classes of this standard. 6.1.2 Machine graded timber Machine graded timber shall meet the requirements of EN 14081 (all parts). 6.2 Classification 6.2.1 C
43、haracteristic values The characteristic values of bending strength, modulus of elasticity in bending (mean) and density for the timber population concerned shall be determined in accordance with EN 384. NOTE Other strength and stiffness properties, as well as mean density values, are determined acco
44、rding to Annex A. 6.2.2 Allocation to a strength class A timber population may be assigned to a strength class if its characteristic values of bending strength and density equal or exceed the values for that strength class given in Table 1, and its characteristic mean modulus of elasticity in bendin
45、g equals or exceeds 95 % of the value for that strength class given in Table 1. NOTE Provided the settings are available in EN 14081-4, a grading machine may be set to grade directly to the strength class strength, stiffness and density values. Timber graded in this way should be referred to by the
46、strength class number and marked according to EN 14081-1, EN 14081-2 and EN 14081-3. Copyright European Committee for Standardization Provided by IHS under license with CENNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS EN 338:2009EN 338:2009 (E) 9 Annex A (info
47、rmative) Determination of values in addition to bending strength, stiffness and density The following equations were used to determine the characteristic values in Table 1 for properties other than bending strength, mean modulus of elasticity in bending and density. Tensile strength parallel to grai
48、n km,kt,0,6,0 ff = Compression strength parallel to grain ()45,0km,kc,0,5 ff = Shear strength v,kshall be taken from Table 1 Tensile strength perpendicular to grain t,90,k= 0,4 N/mm for softwoods t,90,k= 0,6 N/mm for hardwoodsCompressive strength perpendicular to grain kkc,90,007,0 =ffor softwoods kkc,90,015,0 =ffor hardwoods Modulus of elasticity parallel to grain mean,005,067,0 EE = for softwoods mean,005,084,0 EE =for hardwoods Mean modulus of elasticity perpendicular to grain 30/mean,0mean,90EE = for
