SIST EN 14081-3:2006

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 3: Maschinelle Sortierung; zusätzliche Anforderungen an die werkseigene ProduktionskontrolleStructures en bois - Bois de structure de section rectangulaire classé selon la résistance - Partie 3 : Classement mécanique - Exigences complémentaires relatives au contrôle de la production en usineTimber structures - Strength graded structural timber with rectangular cross section - Part 3: Machine grading; additional requirements for factory production control91.080.20Lesene konstrukcijeTimber structures79.040Les, hlodovina in žagan lesWood, sawlogs and sawn timberICS:Ta slovenski standard je istoveten z:EN 14081-3:2005SIST EN 14081-3:2006en01-maj-2006SIST EN 14081-3:2006SLOVENSKI
STANDARDSIST EN 519:1996SIST EN 518:19961DGRPHãþD



SIST EN 14081-3:2006



EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 14081-3November 2005ICS 79.040Supersedes EN 518:1995, EN 519:1995
English VersionTimber structures - Strength graded structural timber withrectangular cross section - Part 3: Machine grading; additionalrequirements for factory production controlStructures en bois - Bois de structure à sectionrectangulaire classé pour sa résistance - Partie 3:Classement mécanique; exigences supplémentaires enconcernant le contrôle de la production en usineHolzbauwerke - Nach Festigkeit sortiertes Bauholz fürtragende Zwecke mit rechteckigem Querschnitt - Teil 3:Maschinelle Sortierung; zusätzliche Anforderungen diewerkseigene ProduktionskontrolleThis European Standard was approved by CEN on 26 August 2005.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2005 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 14081-3:2005: ESIST EN 14081-3:2006



EN 14081-3:2005 (E) 2 Contents Page Foreword.3 Introduction.4 1 Scope.5 2 Normative references.5 3 Terms and definitions.5 4 Symbols.6 5 Requirements for the operation, calibration and maintenance of a grading machine.6 6 Additional factory production control requirements for machine controlled systems.7 6.1 General.7 6.2 Requirements for strength grades with a characteristic bending strength above 30 N/mm2.7 7 Additional factory production control requirements for output controlled systems.7 7.1 General.7 7.2 Production control.7 Annex A (normative)
Example of cusum control charts.11 Annex B (normative)
Requirements for using control planks.15 B.1 General.15 B.2 Production control.15 B.3 The procedure for the use of a control plank.16 B.4 The non-continuous indicating property.16 B.5 Recorded usage of a control plank.17 B.6 Care of a control plank when not in use.17 B.7 Discarded control planks.17
SIST EN 14081-3:2006



EN 14081-3:2005 (E) 3 Foreword This European Standard (EN 14081-3:2005) 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 May 2006, and conflicting national standards shall be withdrawn at the latest by August 2007. This European Standard 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). This European Standard supersedes EN 518:1995 and EN 519:1995. Other parts of this European Standard are: EN 14081-1 Timber structures - Strength graded structural timber with rectangular cross section – Part 1: General requirements, EN 14081-2 Timber structures - Strength graded structural timber with rectangular cross section – Part 2: Machine grading; additional requirements for initial type testing, 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, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. SIST EN 14081-3:2006



EN 14081-3:2005 (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 European Standard 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 14081-3:2006



EN 14081-3:2005 (E) 5 1 Scope This European Standard specifies requirements additional to those given in EN 14081-1 for factory production control 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. 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 336, Structural timber — Sizes, permissible deviations EN 338, Structural timber — Strength classes EN 408, 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 14081-2:2005, Timber structures — Strength graded structural timber with rectangular cross section — Part 2: Machine grading; additional requirements for initial type testing 3 Terms and definitions For the purpose of this European Standard, the terms and definitions given in EN 14081-1:2005 and the following apply. 3.1 depth dimension perpendicular to the longitudinal axis of a timber beam, in the plane of the bending forces 3.2 grade determining property mechanical or physical property for which a particular value of that property has to 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 3.3 master machine particular grading machine used for deriving the production settings during initial type testing 3.4 sample number of specimens of timber of one size and representative of one species population SIST EN 14081-3:2006



EN 14081-3:2005 (E) 6 4 Symbols A
cusum control parameter
B
cusum control parameter
Ba
cusum parameter associated with acceptable quality level
Br
cusum parameter associated with rejectable quality level Ep
actual modulus of elasticity measured in a proof load test (in N/mm2)
E0,mean
characteristic mean modulus of elasticity parallel to grain (in N/mm2)
Fp
proof load (in N)
K
cusum control parameter
La
run length in acceptable region for cusum control
Lr
run length in rejectable region for cusum control
N
cusum control parameter
Y
cusum control parameter
Z
cusum control parameter 5 Requirements for the operation, calibration and maintenance of a grading machine 5.1 No modifications shall be made to the machine that are in conflict with the machine manufacturer’s specification. 5.2 Access to all machine adjustments shall be limited to personnel authorised to operate or set up the machine. 5.3 The strength grading machine shall be regularly calibrated in accordance with the manufacturer's specification (see 5.2 in EN 14081-2:2005). 5.4 A strength grading machine shall only be fitted with spare parts equivalent to, or improving upon, the performance of those fitted at the time the machine was assessed by initial type testing. If spare parts are fitted that are not identical to those fitted at the time the machine was assessed by initial type testing, they shall be reassessed to establish their effect on grading accuracy. 5.5 The results of routine service and maintenance to the strength-grading machine and ancillary equipment shall be recorded together with the results of calibration checks. SIST EN 14081-3:2006



EN 14081-3:2005 (E) 7 6 Additional factory production control requirements for machine controlled systems 6.1 General When grading structural timber in a machine controlled system, grading accuracy shall be monitored. A grading machine’s dynamic performance may be controlled by the use of control planks. Where control planks are used the additional procedures given in Annex B shall be followed 6.2 Requirements for strength grades with a characteristic bending strength above 30 N/mm2 During each working shift, two pieces of timber from each grade produced shall be randomly selected and tested for edgewise bending strength as given in EN 408 with the tension edge selected at random and the estimated weakest cross section positioned where possible within the centre third of the span. The fifth percentile value, determined by ranking, of the 100 bending strength values from 50 consecutive shifts shall meet the required bending strength (as given in 6.2.4.3 b) in EN 14081-2:2005). A strength property other than edgewise bending strength may be used for quality control as an alternative, provided the relation between the two properties is verified from test data. 7 Additional factory production control requirements for output controlled systems 7.1 General When grading structural timber in an output controlled system, grading accuracy shall be monitored by testing samples drawn from production and analysing the results using the cusum procedure described as follows. 7.2 Production control 7.2.1 Five specimens of the strength class to be tested shall be counted, then the sixth specimen shall be selected for the test sample. This procedure shall be repeated ten times to select two five-specimen samples from each class produced during each working shift. This process shall take place at approximately equal intervals during the shift period. For the first three working shifts the sampling rate shall be doubled using newly assessed settings. 7.2.2 Each sample selected from production shall be tested as follows, using the apparatus described in 7.2.1 a) of EN 14081-2:2005. a) Proof load to Fp (as specified in 7.2.2 of EN 14081-2:2005) each specimen edgewise over a span of
18 times the piece depth and using third-point loading with the tension edge selected at random and the estimated weakest cross section positioned where possible within the centre third of the span. b) Determine the actual modulus of elasticity Ep in accordance with 7.2.1 c) of EN 14081-2:2005. The rate of applied stress shall be 110 N/mm2/min. The number of specimens that fail below the proof load and the values of Ep shall be recorded on the cusum control charts. NOTE For an example see Annex A. SIST EN 14081-3:2006



EN 14081-3:2005 (E) 8 7.2.3 Calculate the three cusum control constants K, Y and Z and enter them on the cusum control charts. These are determined as follows: control of bending strength: K = 1, Y = 1, Z = 6; control of characteristic mean modulus of elasticity parallel to grain: K = 0,95 E0,mean – 345
(1) where
E0,mean
is the equal to the mean modulus of elasticity for the strength class. A constant ‘A’ shall be calculated from the equation A = 7 381/E0,mean and used in Figure 1 to determine two values of B expressed as Ba when La = 150 and Br when Lr = 5. The remaining control constants Y and Z are then calculated from: Y = 0,046 7E0, mean Ba
(2) N = 0,046 7E0, mean Br
(3) Z = Y + N
(4) 7.2.4 All results from the tests on quality-control specimens from production shall be entered on the control
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