1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN 14272:2011Plywood Calculation methodfor some mechanical propertiesBS EN 14272:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN 142
2、72:2011. Itsupersedes DDENV14272:2002 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee B/541, Wood based panels.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include
3、all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012ISBN 978 0 580 69385 4ICS 79.060.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authorit
4、y of theStandards Policy and Strategy Committee on 31 January 2012.Amendments issued since publicationDate Text affectedBS EN 14272:2011EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 14272 December 2011 ICS 79.060.10 Supersedes ENV 14272:2002English Version Plywood - Calculation method for som
5、e mechanical properties Contreplaqu - Mthode de calcul pour certaines caractristiques mcaniques Sperrholz - Rechenverfahren fr einige mechanische Eigenschaften This European Standard was approved by CEN on 1 October 2011. CEN members are bound to comply with the CEN/CENELEC Internal Regulations whic
6、h stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member. This Eur
7、opean Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members a
8、re the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Swed
9、en, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members.
10、Ref. No. EN 14272:2011: EBS EN 14272:2011EN 14272:2011 (E) 2 Contents Page Foreword 41 Scope 52 Normative references 53 Principle 54 Terms and definitions .65 Symbols 65.1 Main symbols .65.2 Subscripts 76 Calculation method86.1 General 86.2 Properties relevant to the calculation methods .86.3 Wood s
11、pecies .86.4 Factors for plywood composition 87 Characteristic values for strength and stiffness in bending, tension and compression 117.1 General . 117.2 Bending 117.2.1 General . 117.2.2 Modulus of elasticity 117.2.3 Strength . 117.3 Tension and compression . 127.3.1 Stiffness and capacity of the
12、layers in the cross section 127.3.2 Stiffness and capacity of the panel. 137.3.3 Property of the panel (as if homogenized) . 137.4 Property values for layers 137.4.1 General . 137.4.2 Modulus of elasticity (, ; . 147.4.3 Resistance . 148 Shear properties . 158.1 Panel shear 158.1.1 Panel shear rigid
13、ity (Gv) . 158.1.2 Panel shear strength (fv) 168.2 Planar shear 168.2.1 General . 168.2.2 Planar shear rigidity (Gr) 168.2.3 Planar shear strength (fr) . 179 Ratio of strength upon modulus . 1710 Density . 1711 Conversion from strength and modulus of elasticity to capacity and stiffness 18Annex A (n
14、ormative) Derivation for the veneer values (or basic values) . 19A.1 Scope . 19A.2 Principle . 19A.2.1 Option 1: Using plywood test results . 19A.2.2 Option 2: Using solid timber properties . 19A.3 Procedure for derivation of properties from testing plywood . 19A.3.1 General . 19A.3.2 Sampling 20BS
15、EN 14272:2011EN 14272:2011 (E) 3 A.3.3 Test pieces . 20A.3.4 Testing 20A.3.5 Exploitation of the results 21A.4 Derivation of estimated values for veneers 25A.4.1 General . 25A.4.2 Values obtained by testing . 25A.4.3 Imposed values 25A.5 Report . 25Annex B (normative) Practical spreadsheets to deriv
16、e the properties 27B.1 General . 27B.2 Bending 28B.2.1 General . 28B.2.2 Main tables . 28B.2.3 Tables for strength values 31B.3 Tension and compression 33B.4 Panel shear 39B.5 Planar shear . 40B.5.1 General . 40B.5.2 Available veneer values 40B.5.3 Veneer values not available . 42Annex C (informativ
17、e) Example of bending strength 43C.1 Determination of the stress in the layers 43C.2 Determination of the panel strength 45Bibliography 47BS EN 14272:2011EN 14272:2011 (E) 4 Foreword This document (EN 14272:2011) has been prepared by Technical Committee CEN/TC 112 “Wood-based panels”, the secretaria
18、t of which is held by DIN. 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 June 2012, and conflicting national standards shall be withdrawn at the latest by June 2012. Attention is drawn to the po
19、ssibility that 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 ENV 14272:2002. Annex A and Annex B are normative. Compared to ENV 14272:2002, the follow
20、ing modifications have been made: a) calculation applies to panels of any composition, symmetrical or not; b) values resulting for the panels can be used for calculation as characteristics values as required by EN 1995-1-1; c) new Annex A (normative) provides the derivation for the veneer values (ba
21、sic values); d) new Annex B (normative) provides practical spreadsheets to derive the properties; e) new Annex C (informative) gives an example of bending strength. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to impleme
22、nt this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switz
23、erland and the United Kingdom. BS EN 14272:2011EN 14272:2011 (E) 5 1 Scope This European Standard specifies, for plywood panels of any composition, symmetrical or not, a calculation method to derive some mechanical properties (strength and stiffness in bending, tension, compression, panel and planar
24、 shear) as well as density from the wood compounding the layers. NOTE Usually, the lay-up of the panels is symmetrical but, very often, the surface appearance of the face and the surface appearance of the back face differ, hence a difference between the mechanical properties of the respective veneer
25、s. Therefore, in this case, the composition is not mechanically symmetrical and a symmetry independent calculation method is needed. Provided that structural characteristic values are taken for the layers, the resulting values for the panels can be used as characteristic values as required by EN 199
26、5-1-1. Conversely, Annex A defines the procedures to derive the veneer properties, in bending, tension and compression, either from testing panels according to EN 789 and EN 1058 or from timber testing according to EN 408 or from imposed values defined in EN 338. Annex B provides practical spreadshe
27、ets, which are applications of the equations in the main part of this standard. Annex C provide an example for the calculation of bending strength, in accordance with Annex B. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated
28、references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 325, Wood-based panels Determination of dimensions of test pieces EN 338:2009, Structural timber Strength classes EN 384, Structural timber Determi
29、nation of characteristic values of mechanical properties and density EN 408, Timber structures Structural timber and glued laminated timber Determination of some physical and mechanical properties EN 789, Timber structures Test methods Determination of mechanical properties of wood based panels EN 1
30、058, Wood-based panels Determination of characteristic 5-percentile values and characteristic mean values EN 12369-2, Wood-based panels Characteristic values for structural design Part 2 Plywood EN 14358, Timber structures Calculation of characteristic 5-percentile values and acceptance criteria for
31、 a sample 3 Principle Using the mechanical properties of the wood species, which compound the layers (in this standard referred to as veneer or basic values), it consists in deriving, by calculation, the mechanical properties of a panel. For bending, tension and compression, each layer property valu
32、e, along and across the length of the panel, is weighted by a geometrical factor related to its weight in the panel cross section. BS EN 14272:2011EN 14272:2011 (E) 6 In this standard, where a value for a given property of the veneers is derived with a specified test method (including exploitation o
33、f the results), the models in this standard will provide a panel value for that property as if derived with the specified test method. EXAMPLE For instance, if, in a panel composition, a specified percentile of a bending property of veneers is determined with EN 789 and EN 1058, the calculated value
34、 of the bending property of the panel will be its specified percentile as if determined by using EN 789 and EN 1058. 4 Terms and definitions For the purposes of this document, the following terms and definitions apply. 4.1 characteristic strength population fifth percentile value relating to a tempe
35、rature of 20 C and a relative humidity of 65 % 4.2 characteristic stiffness either the population fifth percentile or the mean value relating to a temperature of 20 C and a relative humidity of 65 % 4.3 characteristic density population fifth percentile value with mass and volume corresponding to eq
36、uilibrium at a temperature of 20 C and a relative humidity of 65 % either of the wood species or of the panels, single species or mixed species NOTE The density values found from calculation refer to the minimum acceptable density of veneers used in the lay-up of plywood. In the case of single speci
37、es plywood these values are taken as the characteristic values for the plywood. In the case of mixed species plywood the characteristic value of density of the panel is calculated from the characteristic densities of the individual veneers according to the proportion of each species 4.4 veneer value
38、 or basic value characteristic value of a property to be used for each layer in the equations of the calculation method NOTE Characteristic values of the wood species, along and across the grain, are fifth percentile values for strength but either mean values or fifth percentile values for stiffness
39、 (modulus of elasticity). 4.5 reference panel value value of a given mechanical property of a panel composition NOTE It is to be used to derive the veneer value (or basic value) of the property. 5 Symbols 5.1 Main symbols A area (b tnom), in square millimetres f strength, in Newtons per square milli
40、metre E modulus of elasticity, in Newton per square millimetre Fs shear forces in a bending panel, in Newtons BS EN 14272:2011EN 14272:2011 (E) 7 G modulus of rigidity, in Newtons per square millimetre b width of panel (equal to 1 in the equations), in millimetres t, thickness of layers, in millimet
41、res T thickness of panels, in millimetres W section modulus, equal to ( )6/.2nomtb , in cubic millimetres I second moment of area, equal to ()12/.3nomtb , in millimetres to the fourth power density, in kilograms per cubic metre kamodification factor, appearance class grade z distance of the axis of
42、a layer to the neutral axis of the panel, in millimetres distance of the neutral axis from either face of the panel, in millimetres Ecc eccentricity factor, no dimension L/L relative elongation of the layers (bending, tension and compression) P property V strength or modulus, in Newton per square mi
43、llimetre Rw in the set of layers, the weaker ratio of strength upon modulus for the properties of the wood species involved in the composition of a panel Up stiffness of the panel s standard deviation 5.2 Subscripts m bending t tension c compression v panel shear r planar shear w applies to the lowe
44、r ratio strength/modulus (f/E) of a property of a layer in a multi-species panel nom, mean nominal value and mean value respectively n number of layers of the panel (from top face to bottom face) i rank of layers from top face ax stands for neutral axis in bending density 0 parallel to length of the
45、 plywood (direction of the grain of the face layers) 90 perpendicular to the length BS EN 14272:2011EN 14272:2011 (E) 8 05 5 percentile characteristic value 6 Calculation method 6.1 General The mechanical properties of plywood, in bending, tension, compression panel shear and planar shear can be der
46、ived by calculation. The calculation method described in this standard can be applied to plywood panels of any composition, symmetrical or not. For the classification according to appearance classes of plywood, see EN 635-2 and EN 635-3. 6.2 Properties relevant to the calculation methods For calcula
47、tion of characteristic values of mechanical properties for different plywood compositions, the values of the properties of the veneers compounding the layers shall be derived in accordance with Annex A. The relevant properties are as listed in Table 1. 6.3 Wood species For calculating the characteri
48、stic values of panel mechanical properties, test values shall be used where available for each wood species in the plywood panel composition; where not, imposed values from EN 338 shall be used. NOTE EN 338 values, related to the density of the wood species, are quite conservative and therefore shou
49、ld be used as a last resort option. 6.4 Factors for plywood composition The characterization of plywood composition is shown in Table 2. For the purposes of calculation, if two or more plies are glued together in the same grain direction, they can be considered as one single layer provided that they belong to the same wood species; otherwise they shall be considered as independent
