SIST EN 14081-2:2011
(Main)Timber structures - Strength graded structural timber with rectangular cross section - Part 2: Machine grading; additional requirements for initial type testing
Timber structures - Strength graded structural timber with rectangular cross section - Part 2: Machine grading; additional requirements for initial type testing
This European Standard specifies requirements, additional to those in EN 14081-1, for initial type testing of machine graded structural timber with rectangular cross sections shaped by sawing, planing or other methods, and having deviations from the target sizes corresponding to EN 336. This includes requirements for strength grading machines and test equipment for proof loading graded material.
Holzbauwerke - Nach Festigkeit sortiertes Bauholz für tragende Zwecke mit rechteckigem Querschnitt - Teil 2: Maschinelle Sortierung; zusätzliche Anforderungen an die Erstprüfung
Dieses Dokument legt Anforderungen, neben den in EN 14081-1 angegebenen, an die Erstprüfung für maschinell sortiertes Bauholz für tragende Zwecke mit rechteckigem Querschnitt fest, welches durch Sägen, Hobeln oder andere Produktionsverfahren hergestellt wurde und die zulässigen Maßabweichungen nach EN 336 einhält. Anforderungen an Maschinen, die nach Festigkeit sortieren, und an Prüfeinrichtungen für die Prüfung von Bauholz, das durch Prüfbelastung sortiert wurde ebenfalls enthalten.
Structures en bois - Bois de structure à section rectangulaire classé selon la résistance - Partie 2: Classement mécanique - Exigences supplémentaires concernant les essais de type initiaux
La présente Norme européenne spécifie les exigences, en complément des exigences établies dans l'EN 14081-1, concernant les essais de type initiaux du bois de structure de sections rectangulaires classé par machine et profilé par sciage, rabotage ou d'autres méthodes, et dont les dimensions s'écartent des dimensions cibles correspondant à l'EN 336. Ceci comprend les exigences concernant les machines de classement de la résistance et le matériel d'essai pour les matériaux classés en fonction de leur charge d'épreuve, ainsi que les exigences facultatives concernant les planches de contrôle destinées à vérifier la performance dynamique des machines de classement.
Lesene konstrukcije - Razvrščanje konstrukcijskega lesa pravokotnega prečnega prereza po trdnosti - 2. del: Strojno razvrščanje; dodatne zahteve za začetni preskus proizvodnje
Poleg zahtev v EN 14081-1 ta evropski standard določa dodatne zahteve za začetni preskus proizvodnje strojnega konstrukcijskega lesa pravokotnega prečnega prereza, ki se oblikuje z žaganjem, glajenjem ali drugimi metodami in odstopa od tarčne velikosti v skladu z EN 336. To vključuje zahteve za stroje za razvrščanje po trdnosti in preskusno opremo za razvrščanje materiala s poskusno obremenitvijo.
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Holzbauwerke - Nach Festigkeit sortiertes Bauholz für tragende Zwecke mit rechteckigem Querschnitt - Teil 2: Maschinelle Sortierung; zusätzliche Anforderungen an die ErstprüfungStructures en bois - Bois de structure à section rectangulaire classé selon la résistance - Partie 2: Classement mécanique - Exigences supplémentaires concernant les essais de type initiauxTimber structures - Strength graded structural timber with rectangular cross section - Part 2: Machine grading; additional requirements for initial type testing91.080.20Lesene konstrukcijeTimber structures79.040Les, hlodovina in žagan lesWood, sawlogs and sawn timberICS:Ta slovenski standard je istoveten z:EN 14081-2:2010SIST EN 14081-2:2011en,fr,de01-april-2011SIST EN 14081-2:2011SLOVENSKI
STANDARDSIST EN 14081-2:20061DGRPHãþD
SIST EN 14081-2:2011
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 14081-2
June 2010 ICS 79.040 Supersedes EN 14081-2:2005English Version
Timber structures - Strength graded structural timber with rectangular cross section - Part 2: Machine grading; additional requirements for initial type testing
Structures en bois - Bois de structure à section rectangulaire classé selon la résistance - Partie 2: Classement mécanique - Exigences supplémentaires concernant les essais de type initiaux
Holzbauwerke - Nach Festigkeit sortiertes Bauholz für tragende Zwecke mit rechteckigem Querschnitt - Teil 2: Maschinelle Sortierung - Zusätzliche Anforderungen an die Erstprüfung This European Standard was approved by CEN on 5 May 2010.
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 bibliographical 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 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, 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, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14081-2:2010: ESIST EN 14081-2:2011
EN 14081-2:2010 (E) 2 Contents Page Foreword .3Introduction .41Scope .52Normative references .53Terms and definitions .54Symbols .65Requirements for strength grading machines .76Additional requirements for initial type testing for machine controlled systems .86.1General .86.2Requirements for the derivation and verification of machine settings.86.3Machine installation check . 147Additional requirements for initial type testing for output controlled systems . 157.1General . 157.2Requirements for the assessment of initial settings . 15Annex A (normative)
Calculation of elementary cost matrix values for 6.2.4.8 . 17A.1General . 17A.2Factors for wrongly upgraded pieces. 17A.3Factors for wrongly downgraded pieces . 17Annex B (informative)
Guidance on the procedure of initial type testing for machine controlled systems . 19B.1 Introduction . 19B.2 Guidance . 19Bibliography . 21 SIST EN 14081-2:2011
EN 14081-2:2010 (E) 3 Foreword This document (EN 14081-2:2010) has been prepared by Technical Committee CEN/TC 124 “Timber structures”, the secretariat of which is held 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 December 2010, and conflicting national standards shall be withdrawn at the latest by December 2010. Attention is drawn to the possibility 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 EN 14081-2:2005. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). Other parts of the EN 14081 series are: EN 14081-1, Timber structures Strength graded structural timber with rectangular cross section Part 1: General requirements; EN 14081-3, Timber structures Strength graded structural timber with rectangular cross section Part 3: Machine grading; additional requirements for factory production control EN 14081-4, Timber structures Strength graded structural timber with rectangular cross section Part 4: Machine grading Grading machine settings for machine controlled systems According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement 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, Switzerland and the United Kingdom.
SIST EN 14081-2:2011
EN 14081-2:2010 (E) 4 Introduction Machine grading is in common use in a number of countries. The countries use two basic systems, referred to as "output controlled" and "machine controlled". Both systems require a visual override inspection to cater for strength-reducing characteristics that are not automatically sensed by the machine. The output-controlled system is suitable for use where the grading machines are situated in sawmills grading limited sizes, species and grades in repeated production runs of around one working shift or more. This enables the system to be controlled by testing timber specimens from the daily output. These tests together with statistical procedures are used to monitor and adjust the machine settings to maintain the required strength properties for each strength class. With this system it is permissible for machine approval requirements to be less demanding and for machines of the same type to have non-identical performance. The machine controlled system was developed in Europe. Because of the large number of sizes, species and grades used it was not possible to carry out quality control tests on timber specimens drawn from production. The system relies therefore on the machines being strictly assessed and controlled, and on considerable research effort to derive the machines settings, which remain constant for all machines of the same type. The acceptability of grading machines and the derivation of settings rely on statistical procedures and the results will therefore depend on the method used. For this reason this document gives appropriate statistical procedures. The requirements in this European Standard are based on machines in current use and on future types of machines as far as these can be foreseen. It is recognised that additional clauses or standards may be required if unforeseen developments take place. SIST EN 14081-2:2011
EN 14081-2:2010 (E) 5 1 Scope This European Standard specifies requirements, additional to those in EN 14081-1, for initial type testing of machine graded structural timber with rectangular cross sections shaped by sawing, planing or other methods, and having deviations from the target sizes corresponding to EN 336. This includes requirements for strength grading machines and test equipment for proof loading graded material. 2 Normative references The following referenced documents are indispensable for the application of this European Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 338, Structural timber — Strength classes EN 384, Structural timber — Determination of characteristic values of mechanical properties and density EN 408:2003, Timber structures — Structural timber and glued laminated timber — Determination of some physical and mechanical properties EN 14081-1:2005, Timber structures — Strength graded structural timber with rectangular cross section — Part 1: General requirements EN 14081-3, Timber structures — Strength graded structural timber with rectangular cross section — Part 3: Machine grading; additional requirements for factory production control EN 14081-4, Timber structures Strength graded structural timber with rectangular cross section Part 4: Machine grading Grading machine settings for machine controlled systems 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 14081-1:2005 and the following apply. 3.1 characteristic strength population 5-percentile value obtained from the results of tests with a duration of (300 ± 120) s using test pieces at an equilibrium moisture content resulting from a temperature of 20 °C and a relative humidity of
65 % 3.2 characteristic stiffness population mean value obtained under the same test conditions as defined in 3.1 3.3 critical feed speed speed within the intended usable range at which the grading machine is least accurate in measuring its indicating property 3.4 depth dimension perpendicular to the longitudinal axis of a timber beam, in the plane of the bending forces SIST EN 14081-2:2011
EN 14081-2:2010 (E) 6 3.5 grade determining property mechanical or physical property for which a particular value of that property should be achieved for the material to be assigned to that grade, e.g. bending strength, mean modulus of elasticity and density for the strength classes of EN 338 3.6 indicating property
IP measurement or combination of measurements made by the grading machine, which are closely related to one or more of the grade determining properties NOTE For grading machines which compute and predict values of the grade determining properties directly from numerous measuring devices, the indicating property may be a predicted value of a grade determining property. 3.7 optimum grade highest grade, of those for which settings are required, to which a piece of timber can be assigned, such that the grade determining properties of the graded sample will meet the values required for the grade 3.8 settings values of the parameters used to set the machine to grade timber, which are mathematically related to the indicating property 3.9 sub-sample number of specimens of timber of one species or species combination, from one growth area or source of production 3.10 thickness lesser dimension perpendicular to the longitudinal axis of a piece of timber 4 Symbols b width of cross section (in millimetres)
E theoretical modulus of elasticity (in newtons per square millimetre)
Ep actual modulus of elasticity measured in a proof load test (in newtons per square millimetre)
Eassigned mean modulus of elasticity for assigned grade (in newtons per square millimetre) Eoptimum mean modulus of elasticity for optimum grade (in newtons per square millimetre) E0,mean characteristic mean modulus of elasticity parallel to grain (in newtons per square millimetre)
F applied force (in newtons)
Fp proof load (in newtons)
fm,k characteristic bending strength (in newtons per square millimetre)
fp proof stress (in newtons per square millimetre)
h depth of cross section (in millimetres) SIST EN 14081-2:2011
EN 14081-2:2010 (E) 7 kh size factor l span (in millimetres) t thickness (in millimetres)
w deflection or deformation (in millimetres)
βach achieved safety index βtar target safety index δ deflection (in millimetres) µ mean value of bending strength for the optimum or assigned strength classes (in newtons per square millimetre) 5 Requirements for strength grading machines 5.1 The machine shall be of a type that meets the requirements given in Clauses 5 and 6 if it is part of a machine-controlled system, or Clauses 5 and 7 if it is part of an output controlled system. It shall be installed and set up according to the manufacturer's specification and to any additional requirements resulting from the tests given here. In addition, except when a grading machine operates by measuring the bending stiffness of timber, the installation and calibration shall be checked by the use of control planks, using the procedures given in EN 14081-3 under requirements for the use of control planks. 5.2 The following information shall be provided in the manufacturer's specification for the machine: a) specification and description of the mechanical and electrical operation of the machine, and the software (this includes information on data processing such as smoothing of the output signals) used by the machine to grade timber; b) range of environmental conditions under which the machine will operate; c) installation, maintenance and operating instructions; d) method, extent and frequency of calibration procedures, including the use of control planks if applicable; e) species populations, sizes, tolerances, surface finish, moisture content, grades, environmental operating temperature range, throughput speed, and limits of warp of the timber to be graded; f) manufacturing tolerances of the machine; g) checking and adjustment procedures for all components that may affect the machine’s grading accuracy. 5.3 Manufacturing tolerances and transducer accuracy tolerances shall ensure that production machines meet the requirements of this European Standard, and are compatible with grade settings derived for the machine type. 5.4 The grading machine shall not damage the timber during the grading operation to an extent that it affects the intended use of the timber. NOTE For example, in bending type machines, damage should not be caused by large compression perpendicular to grain stresses and/or large bending stresses. SIST EN 14081-2:2011
EN 14081-2:2010 (E) 8 5.5 Grading machines whose indicating property does not take account of the material properties along the whole length of each piece of timber, but whose indicating property measurements are influenced by strength reducing characteristics away from the measuring position (as in bending type machines), shall measure the indicating property to within 800 mm of each end of the piece of timber. Where the indicating property is influenced only by strength reducing characteristics at the measuring position (as in radiation type machines), the measurements shall be made to within 150 mm of each end. 5.6 The grading machine shall be capable of comparing each indicating property measurement with pre-set boundary settings, which correspond to individual grades, and of marking each piece of timber according to the lowest grade sensed within the length of that piece. 5.7 The infeed and outfeed equipment shall provide the correct height and angle of entry/exit for the timber to/from the grading machine and shall not interfere significantly with the sensing of the indicating property, even when the timber is distorted within the limits given in item 5.2, e). If the infeed and outfeed equipment is not part of the grading machine then this requirement shall appear in the manual for the machine. 5.8 The grading machine shall be fitted with the means to enable the accuracy of each measuring device to be checked individually, to ensure correct operation of the machine. 6 Additional requirements for initial type testing for machine controlled systems 6.1 General For machine controlled systems the acceptance of machine graded timber to meet the requirements of this European Standard predominantly depends on the grading machine and the settings used. 6.2 Requirements for the derivation and verification of machine settings 6.2.1 When a new species is required to be graded by a machine that has already been shown to meet the requirements of this European Standard, those requirements that are not likely to be affected by species differences may be disregarded for the new species. NOTE Annex B gives background information and guidance on the procedure required here to derive grading machine settings. 6.2.2 The requirements for selecting the total test sample are given below. Note that the numbers of sub-samples and specimens given are minimums and the reason for the number actually used shall be given in the report (see 6.2.6). The overriding requirement which determines the number of sub-samples and the number of specimens to be tested is that the test sample shall be representative of the timber source from which the production timber is taken.
To derive settings for a new machine type and/or a new species (or species combination) or growth area, the total test sample shall be selected as a minimum number of four sub-samples (see 3.9), to represent the range of timber for which the settings are applicable (see EN 14081-1 under the requirements for machine grading). The minimum number of pieces in a sub-sample shall be 100. The minimum number of pieces in the total test sample shall be 900 for the derivation of settings for the full range of grades and sizes of a grading machine. To derive settings for new species for a machine that has previously met the requirements of this European Standard with different species, a minimum of 450 pieces shall be required. To test whether existing settings in EN 14081-4 are acceptable for use with a new growth area of the same species, the new growth area shall supply a minimum of two sub-samples (see first paragraph of this clause) each containing a minimum of 100 pieces. Each piece shall be graded by the machine using the existing settings and then tested to determine the grade determining properties as given in EN 384 using the kv (bending strength only) factor on strength and the 0,95 factor on E0,mean , but in addition, the use of ks also for E0,mean . The grade determining properties shall equal or exceed those required for the grade. SIST EN 14081-2:2011
EN 14081-2:2010 (E) 9 The number of pieces in the total sample shall ensure that there are a minimum number of 20 pieces in each assigned grade for which settings are required. If more than two grades are to be graded in one pass then it may be necessary to increase the number of pieces up to 40 pieces per grade. The timber shall represent the timber source (see EN 14081-1 under the requirements for machine grading), range of sizes, and quality to be graded in production (with the exception of 6.2.3, c) below), with the most demanding surface finish, and grading shall be carried out at the critical feed speed. The range of permitted sizes for which settings shall be used in production shall not be extrapolated more than 10 % from the maximum and minimum sizes tested. It is acceptable for machines not to measure density, but if density is a grade determining property it shall be checked in accordance with 6.2.4. If density is not a grade determining property the characteristic value for the assigned grade (see 6.2.4.6) shall be determined in accordance with EN 384 and given in the report (see 6.2.6). NOTE The grade determining properties for meeting the requirements of EN 338 are bending strength, MOE and density. For other grades the grade determining properties may be different. If a grading machine does not detect certain strength reducing characteristics in timber, and those characteristics are not detected by visual override inspection or other procedures, care shall be taken to ensure that those characteristics are present in the test sample in the same proportions as will exist in production. Mention of such characteristics shall also be made in the report on the approval tests to ensure that they are taken into account when settings are required for other species. 6.2.3 In addition to the requirements given in 6.2.2 the number of pieces shall be influenced by the following: NOTE 1 Justification for the number of sub-samples tested should be made in the report (see 6.2.6).
a) number of grades and sizes to be graded. At least three sizes shall be tested; b) level of the grades; NOTE 2 Grades with very high critical properties, e.g. above strength class C30, should require more test data because errors in the model are more significant. c) strength and/or stiffness requirement for the strength class to be graded compared to the grade determining property range within the sample. Where the characteristic properties of almost all the timber sample meet the requirements for the grade being tested, the grades assigned by the grading machine have little chance of being in error. Where possible, a greater quantity of weaker material of the same species shall be included in the sample to ensure that the grading machine is making valid decisions when assigning timber to grades (see 6.2.4); d) number of sensing devices used by the machine and the complexity of the model; NOTE 3 A simple regression model based on one independent variable is likely to require less data than a complex neural network model involving a number of sensing devices. e) similarity of the species being considered to other species already graded by that type of grading machine. 6.2.4
6.2.4.1 For each species, the effect of the variables given in 6.2.2 (where relevant) on the indicating property shall be established (interpolation is permitted), and used to develop the mathematical model relating the machine's indicating property to the grade determining properties. For this purpose sub-samples may be taken from the sample required for 6.2.2. The effect of variables which are not dependent on the particular SIST EN 14081-2:2011
EN 14081-2:2010 (E) 10 population of timber may, after establishing the effect on one species, be used for other species. The model may include variables such as size and moisture content, or the model may be determined from the data after adjusting the properties for such variables. Settings shall be derived to grade one or more grades in one pass. 6.2.4.2 The parameters of the model and resulting settings shall be verified for all species and grade combinations, using the procedure below. Having verified the settings for particular sizes, species (or species combinations) and grade combinations, settings for other sizes shall be derived directly from the model, where the model contains such adjustments. 6.2.4.3 All sub-samples of timber referred to in 6.2.2 shall be passed through the machine to record the indicating property values for each piece and then tested to obtain values of the grade determining properties in accordance with EN 384 and EN 408. 6.2.4.4 The grade determining property values shall be adjusted to the same timber size (see factors kh and kl in EN 384) and moisture content and rounded to three significant figures.
NOTE If the grade is for glulam laminations the factors given in EN 14080 should be used instead of those above. 6.2.4.5 All the pieces shall be sorted on the basis of the grade determining properties into the highest possible grades that are graded together and for which settings are required, such that they meet the required values for the grade. If there are less than twenty pieces in a grade then the pieces shall be downgraded to achieve twenty or zero pieces in that grade. The grade so determined for each piece is its optimum grade. The required characteristic values shall be taken from EN 338 and applying factor kv from EN 384 and the 95 % factor on E0,mean from EN 338 where applicable.
NOTE 1 If the grade is for glulam laminations the factors given in EN 14080 should be used instead of those above. NOTE 2 The procedure with the following steps has been shown to give accurate values when determining the optimum grade: 1)
Rank the data set for a grade determining property, then determine and identify the maximum number of pieces that meet the required value for that property for the highest grade. 2)
Repeat 1) for all other grade determining properties. 3)
Label the grade determining properties named as e,g. (a), (b) and (c) with (a) having the largest number of pieces identified in 1) and 2) above, and (c) the least. 4)
Using only the pieces identified for property (a), rank them primarily for property (b) with secondary rankings for properties (c) and (a), and determine the maximum number of pieces that meet the required value for property (b). Using only these pieces rank them primarily for property (c) with secondary rankings for properties (b) and (a). Determine and identify the maximum number of pieces that meet the required value for property (c). Check that these pieces meet the other required properties and if so identify them as that grade. Otherwise adjust as appropriate. 5)
Remove the pieces assigned to that grade and repeat 1) to 5) for all grades beginning with the next highest grade. 6.2.4.6 Using the model derived in 6.2.4 from the total sample, settings shall be determined for each grade to be graded together such that the required grade determining properties are achieved for the total sample less one sub-sample in turn.
NOTE For example, if there are four sub-samples then a setting is determined from a sample comprising sub-samples 2, 3 and 4, then from a sample comprising sub-samples 1, 3 and 4, then from a sample comprising sub-samples 1, 2 and 4, and then finally from a sample comprising sub-samples 1, 2 and 3. SIST EN 14081-2:2011
EN 14081-2:2010 (E) 11 The production setting shall be calculated as the mean value of all the above settings for each grade. If this is more than 15 % different from the most conservative setting, then the production setting shall be that setting adjusted by 15 % towards the mean value. The production settings shall then be used to grade each piece according to its indicating property value. If there are less than twenty pieces in a grade then the setting shall be adjusted to achieve at least twenty pieces in that grade. These grades are known as assigned grades. It is acceptable when determining the assigned grades to change the setting value of the higher grade to increase the number of pieces in the lower grade.
6.2.4.7 A size matrix giving the numbers of pieces in each of the optimum and assigned grades shall be determined for the total sample. NOTE Table 1 is an example of where a machine is required to grade C35, C27 and C22 in one pass. Table 1
Example: Size matrix
Optimum grade Assigned grade C35 C27 C22 Reject C35 207 32 16 2 C27 10 168 12 1 C22 4 13 84 2 Reject 0 2 2 24
6.2.4.8 A global cost matrix shall be determined with the value in each cell equal to the number of pieces in each cell in the size matrix multiplied by the value in the equivalent cell of Table 2 divided by the total number of pieces in the assigned grade. Where settings are required for grades that are not part of the strength class system in EN 338, elementary cost matrix values shall be calculated from the equations given in Annex A. Elementary cost matrix values for reject shall be calculated from the equations given in Annex A using
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