1、September 2016 English price group 12No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 79.040!%Zo“2555876www.din.deDI
2、N EN 16737Structural timber Visual strength grading of tropical hardwood;English version EN 16737:2016,English translation of DIN EN 16737:2016-09Bauholz fr tragende Zwecke Visuelle Sortierung von Tropenholz nach der Festigkeit;Englische Fassung EN 16737:2016,Englische bersetzung von DIN EN 16737:20
3、16-09Bois de structure Classement visuel des bois feuillus tropicaux de structure;Version anglaise EN 16737:2016,Traduction anglaise de DIN EN 16737:2016-09www.beuth.deDocument comprises 23 pagesDTranslation by DIN-Sprachendienst.In case of doubt, the German-language original shall be considered aut
4、horitative.08.16 DIN EN 16737:2016-09 2 A comma is used as the decimal marker. National foreword This document (EN 16737:2016) has been prepared by Technical Committee CEN/TC 124 “Timber structures” (Secretariat: AFNOR, France). The responsible German body involved in its preparation was DIN-Normena
5、usschuss Bauwesen (Building and Civil Engineering Standards Committee), Working Committee NA 005-04-01 AA Holzbau (SpA zu CEN/TC 124, CEN/TC 250/SC 5, ISO/TC 165). EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 16737 May 2016 ICS 79.040 English Version Structural timber - Visual strength gradi
6、ng of tropical hardwood Bois de structure - Classement visuel des bois feuillus tropicaux de structure Bauholz fr tragende Zwecke - Visuelle Sortierung von Tropenholz nach der Festigkeit This European Standard was approved by CEN on 19 March 2016. CEN members are bound to comply with the CEN/CENELEC
7、 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-CENELEC Management Centre or t
8、o 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-CENELEC Management Centre has the same status as the offici
9、al versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, N
10、orway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2016 CEN All rights of ex
11、ploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 16737:2016 EEN 16737:2016 (E) 2 Contents Page European foreword . 3 1 Scope 4 2 Normative references 4 3 Terms and definitions . 4 4 Strength graded timber. 6 4.1 Supervision of strength grading operatio
12、ns 6 4.2 Sizes 6 4.3 Processing of visually graded timber. 6 4.4 Moisture content . 6 5 Measurement of strength-reducing characteristics . 7 5.1 Knots 7 5.1.1 General 7 5.1.2 Knot size: requisite comparisons 7 5.1.3 Pin knots 10 5.2 Slope of grain . 10 5.3 Density . 11 5.4 Fissures 11 5.5 Wane . 11
13、5.6 Distortion 11 5.6.1 Bow and spring . 11 5.6.2 Twist . 11 5.7 Biological characteristics 11 5.7.1 Fungal biodegradation . 11 5.7.2 Insect attack . 12 5.7.3 Marine borers 12 5.8 Other defects and characteristics . 12 6 Limiting values of characteristics for STH grade 13 7 Marking 13 Annex A (infor
14、mative) Tropical hardwood species and their densities . 14 DIN EN 16737:2016-09 EN 16737:2016 (E) 3 European foreword This document (EN 16737:2016) has been prepared by Technical Committee CEN/TC 124 “Timber structures”, the secretariat of which is held by AFNOR. This European Standard shall be give
15、n the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2016 and conflicting national standards shall be withdrawn at the latest by November 2016. Attention is drawn to the possibility that some of the elements of this document may
16、 be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This standard gives grading methods, definitions and criteria as required in EN 14081-1 for a visual strength grading standard. According to the CEN-CENELEC Internal Regu
17、lations, 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, I
18、taly, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. DIN EN 16737:2016-09 EN 16737:2016 (E) 4 1 Scope This European Standard specifies a method of strength grading tropical hardwood
19、visually for structural use. The permissible limits of characteristics for a single visual strength grade of timber are specified, designated “Structural Tropical Hardwood” (STH) grade. The method is only suitable for pieces of timber with a rectangular cross-section that is constant along their len
20、gths. Characteristics related to durability are not covered in this standard. For some end uses, additional requirements may be specified at the time of grading, e.g. sapwood exclusion. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document a
21、nd are indispensable for its application. 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, permitted deviations EN 338, Structural timber - Strength class
22、es EN 350-2, Durability of wood and wood-based products - Natural durability of solid wood - Part 2: Guide to natural durability and treatability of selected wood species of importance in Europe EN 384, Structural timber - Determination of characteristic values of mechanical properties and density E
23、N 844-3, Round and sawn timber - Terminology - Part 3: General terms relating to sawn timber EN 844-9, Round and sawn timber - Terminology - Part 9: Terms relating to features of sawn timber EN 844-10, Round and sawn timber - Terminology - Part 10: Terms relating to stain and fungal attack EN 844-12
24、, Round and sawn timber - Terminology - Part 12: Additional terms and general index EN 1310:1997, Round and sawn timber - Method of measurement of features EN 1912, Structural Timber - Strength classes - Assignment of visual grades and species EN 13556, Round and sawn timber - Nomenclature of timber
25、s used in Europe EN 14081-1, Timber structures - Strength graded structural timber with rectangular cross section - Part 1: General requirements 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 336, EN 844-3, EN 844-9, EN 844-10, EN 844-12 and EN 14081
26、-1 and the nomenclature in EN 13556 and the following apply. 3.1 bark pocket bark that is partly or wholly enclosed in the wood DIN EN 16737:2016-09 EN 16737:2016 (E) 5 3.2 bore hole hole or tunnel in timber caused by insects 3.3 boxed heart pith that is present and not visible on any face or edge 3
27、.4 brittleheart wood characterized by abnormal brittleness, mostly located in the heart 3.5 compression creases buckling of fibres across the grain as a consequence of excessive internal growth stresses or external forces 3.6 interlocked grain grain in which cells in succeeding growth periods inclin
28、e alternately in opposite directions that are different from that of the axis of the tree 3.7 fissure longitudinal separation of the fibres 3.8 pinhole bore hole usually not more than 2 mm in diameter 3.9 pin knot round or oval knot, sound, intergrown or partially intergrown, with a maximum size of
29、5 mm 3.10 resin pocket lens-shaped cavity in timber containing, or that has contained, resin 3.11 resin canal longitudinal separation of the fibres containing resin appearing on a face or edge of the piece of timber 3.12 slope of grain divergence of the direction of the fibres from the longitudinal
30、axis of the piece of timber 3.13 thickness lesser dimension perpendicular to the longitudinal axis of the piece of timber Note 1 to entry: This is the size of the edge. DIN EN 16737:2016-09 EN 16737:2016 (E) 6 3.14 tropical hardwood wood of angiosperm trees of the botanical group dicotyledons whose
31、natural distribution lies substantially South of the Tropic of Cancer and north of the Tropic of Capricorn Note 1 to entry: Unlike temperate hardwood, tropical hardwood is typically free of gross anatomical features that indicate the rate of growth, such as annual growth increments. 3.15 width great
32、er dimension perpendicular to the longitudinal axis of the piece of timber Note 1 to entry: This is the size of the face. 4 Strength graded timber 4.1 Supervision of strength grading operations As specified in EN 14081-1, visual strength grading operations shall be carried out by a competent person,
33、 or people working within a company under the close supervision of competent persons. 4.2 Sizes Timber graded to this standard shall conform to EN 336 with respect to its permissible deviations with the following exceptions: the minimum thickness at the time of grading shall be 22 mm; the minimum cr
34、oss-sectional area at the time of grading shall be 2 200 mm2. 4.3 Processing of visually graded timber Visually graded timber shall no longer conform to this standard if its cross-section is reduced in size through subsequent processing by more than: a) 5 mm for dimensions 22 to 100 mm, or; b) 10 mm
35、 for dimensions 100 mm. Where graded timber is reduced in cross section beyond the above limits, it shall be re-graded if it is to conform to this standard. Where graded timber is reduced in length, or a piece of graded timber is cross-cut into two or more pieces, each resulting piece may be assumed
36、 to conform to the permissible limits of characteristics in Table 1 of this standard. 4.4 Moisture content Dry graded timber shall have at the time it is graded for fissures and distortion a mean moisture content of 20 % or less with no individual measurement exceeding 24 %. NOTE The end use determi
37、nes whether timber needs to be dry graded or not. If timber is not dry graded, it may be needed to check fissures and distortion also at the time of end use. DIN EN 16737:2016-09 EN 16737:2016 (E) 7 5 Measurement of strength-reducing characteristics 5.1 Knots 5.1.1 General The size of the knot shall
38、 be related to the width or thickness on the basis of linear values. Methods of measurements of knots are given in EN 1310. The “alternative method” shall be used, whereby the size of the knot is measured in a direction perpendicular to the longitudinal axis of the piece of timber (Figure 1). Knots
39、are accumulative if longitudinal separation between the edges of the knots is either less than twice the width or 300mm (whichever is the lesser), or when the grain has not fully recovered. 1 a) b) c) 2 d) e) f) Figure 1 Measuring knot sizes 1 on faces and 2 on edges 5.1.2 Knot size: requisite compa
40、risons For knots that are contained entirely within a single face or edge, the size of the knot shall be compared to the full size of the face or edge in which it appears (Figure 2). DIN EN 16737:2016-09 EN 16737:2016 (E) 8 X is related to the thickness t and Y is compared to the width w. Figure 2 M
41、easuring knot sizes For arris knots that are not elongated, the size of the knot on both the face and the edge shall be measured. The larger of the two sizes shall be compared to the thickness of the piece (Figure 3). The greater of X and Y is compared to the thickness. Figure 3 Measuring knot sizes
42、 For arris knots that appear on both faces and occupy the full size of an edge, or are elongated across at least 75 % of an edge, the size of the knot on both faces shall be measured. The larger of the two sizes shall be compared to the width of the piece (Figure 4). DIN EN 16737:2016-09 EN 16737:20
43、16 (E) 9 Y is measured on both faces and the larger value is compared to the width. Figure 4 Measuring knot sizes For splay knots or branch knots that are elongated across a face, the size of the knot shall be measured on the edge and compared to the thickness of the piece (Figure 5). X is compared
44、to the thickness. Figure 5 Measuring knot sizes For knot clusters, where no grain recovery is evident between adjacent knots, the knot size shall be measured on the surface on which the cluster is transversely cut. The size of the knot shall be the overall width of the knot cluster d, or the sum of
45、the individual knot widths d1 d2 d3dn, whichever is the lesser (Figure 6). DIN EN 16737:2016-09 EN 16737:2016 (E) 10 a) b) The size of the knot shall be lesser of d and d1+d2+d3.dn.Figure 6 Measuring the size of a knot cluster 5.1.3 Pin knots Single pin knots may be ignored. Tightly grouped pin knot
46、s shall be treated as a single knot. 5.2 Slope of grain The method of measurement of slope of grain by use of a cranked scribe is given in EN 1310:1997, 4.4.1. The slope of grain shall be expressed as the number of units of length over which unit deviation occurs. The slope of grain shall be measure
47、d over a distance sufficiently great to determine the general slope, disregarding local deviations. It shall be measured on both faces and edges to determine the steepest slope. The slope of interlocked grain shall be assessed separately from the general slope of grain. The grader shall examine the
48、piece to determine if the slope of grain reverses at least once through the thickness or width. If this is the case, the rule for interlocked grain may be applied to the steepest slope of interlocked grain. However, in doubtful cases, where, in the graders judgment, interlocked grain occurs to an un
49、desirable extent in relation to the cross-sectional dimension of the piece, the piece shall be rejected. Interlocked grain is a normal feature of certain tropical hardwoods and care should be taken to avoid confusing it with sloping grain. Localized steep slope of grain at the edge of a piece shall be assessed by determining the size of the affected area, perpendicular to the longitudinal axis of the timber. The associated geometrical limitations for arris knots shall apply. D
