1、BS EN 16737:2016Structural timber Visualstrength grading of tropicalhardwoodBSI Standards PublicationBS EN 16737:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN 16737:2016. It partially supersedes BS 5756:2007+A1:2011.BS EN 16737:2016 partially supersedes B
2、S 5756:2007+A1:2011, specifically clause 5 covering the requirements for structural hardwood species and the corresponding Table 1. BS 5756 will be revised at a future date as a result of the publication of this standard.The UK committee notes that there are many published strength class assignments
3、 for named species and sources of tropical hardwood timber that rely on the HS grade of BS 5756. The minor nature of the differences between the STH grade in this standard and the HS grade means that these assignments can adopt the STH grading rules as published here.The UK participation in its prep
4、aration was entrusted to Technical Committee B/518, Structural timber.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct appli
5、cation. The British Standards Institution 2016. Published by BSI Standards Limited 2016ISBN 978 0 580 86021 8ICS 79.040Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committ
6、ee on 31 July 2016.Amendments/corrigenda issued since publicationDate Text affectedg3g3g3g8g24g21g18g19g8g4g17g3g22g23g4g17g7g4g21g7g3g17g18g21g16g8g3g8g24g21g18g19g50g8g17g17g8g3g8g24g21g18g19g34g12g22g6g11g8g3g17g18g21g16g3EN 16737 g3 g3g3 g16g131g155g3g884g882g883g888g3g12g6g22g3g889g891g484g882g
7、886g882g3g8g144g137g142g139g149g138g3g25g135g148g149g139g145g144g3g3g22g150g148g151g133g150g151g148g131g142g3g150g139g143g132g135g148g3g486g3g25g139g149g151g131g142g3g149g150g148g135g144g137g150g138g3g137g148g131g134g139g144g137g3g145g136g3g150g148g145g146g139g133g131g142g3g138g131g148g134g153g145g1
8、45g134g3g5g145g139g149g3g134g135g3g149g150g148g151g133g150g151g148g135g3g486g3g6g142g131g149g149g135g143g135g144g150g3g152g139g149g151g135g142g3g134g135g149g3g132g145g139g149g3g136g135g151g139g142g142g151g149g3g150g148g145g146g139g133g131g151g154g3g134g135g3g149g150g148g151g133g150g151g148g135g3g3 g
9、5g131g151g138g145g142g156g3g136g242g148g3g150g148g131g137g135g144g134g135g3g29g153g135g133g141g135g3g486g3g25g139g149g151g135g142g142g135g3g22g145g148g150g139g135g148g151g144g137g3g152g145g144g3g23g148g145g146g135g144g138g145g142g156g3g144g131g133g138g3g134g135g148g3g9g135g149g150g139g137g141g135g13
10、9g150g3g23g138g139g149g3g8g151g148g145g146g135g131g144g3g22g150g131g144g134g131g148g134g3g153g131g149g3g131g146g146g148g145g152g135g134g3g132g155g3g6g8g17g3g145g144g3g883g891g3g16g131g148g133g138g3g884g882g883g888g484g3g3g3g6g8g17g3g143g135g143g132g135g148g149g3g131g148g135g3g132g145g151g144g134g3g1
11、50g145g3g133g145g143g146g142g155g3g153g139g150g138g3g150g138g135g3g6g8g17g512g6g8g17g8g15g8g6g3g12g144g150g135g148g144g131g142g3g21g135g137g151g142g131g150g139g145g144g149g3g153g138g139g133g138g3g149g150g139g146g151g142g131g150g135g3g150g138g135g3g133g145g144g134g139g150g139g145g144g149g3g136g145g14
12、8g3g137g139g152g139g144g137g3g150g138g139g149g3g8g151g148g145g146g135g131g144g3g22g150g131g144g134g131g148g134g3g150g138g135g3g149g150g131g150g151g149g3g145g136g3g131g3g144g131g150g139g145g144g131g142g3g149g150g131g144g134g131g148g134g3g153g139g150g138g145g151g150g3g131g144g155g3g131g142g150g135g148
13、g131g150g139g145g144g484g3g24g146g486g150g145g486g134g131g150g135g3g142g139g149g150g149g3g131g144g134g3g132g139g132g142g139g145g137g148g131g146g138g139g133g131g142g3g148g135g136g135g148g135g144g133g135g149g3g133g145g144g133g135g148g144g139g144g137g3g149g151g133g138g3g144g131g150g139g145g144g131g142g
14、3g149g150g131g144g134g131g148g134g149g3g143g131g155g3g132g135g3g145g132g150g131g139g144g135g134g3g145g144g3g131g146g146g142g139g133g131g150g139g145g144g3g150g145g3g150g138g135g3g6g8g17g486g6g8g17g8g15g8g6g3g16g131g144g131g137g135g143g135g144g150g3g6g135g144g150g148g135g3g145g148g3g150g145g3g131g144g
15、155g3g6g8g17g3g143g135g143g132g135g148g484g3g3g23g138g139g149g3g8g151g148g145g146g135g131g144g3g22g150g131g144g134g131g148g134g3g135g154g139g149g150g149g3g139g144g3g150g138g148g135g135g3g145g136g136g139g133g139g131g142g3g152g135g148g149g139g145g144g149g3g523g8g144g137g142g139g149g138g481g3g9g148g135
16、g144g133g138g481g3g10g135g148g143g131g144g524g484g3g4g3g152g135g148g149g139g145g144g3g139g144g3g131g144g155g3g145g150g138g135g148g3g142g131g144g137g151g131g137g135g3g143g131g134g135g3g132g155g3g150g148g131g144g149g142g131g150g139g145g144g3g151g144g134g135g148g3g150g138g135g3g148g135g149g146g145g144g
17、149g139g132g139g142g139g150g155g3g145g136g3g131g3g6g8g17g3g143g135g143g132g135g148g3g139g144g150g145g3g139g150g149g3g145g153g144g3g142g131g144g137g151g131g137g135g3g131g144g134g3g144g145g150g139g136g139g135g134g3g150g145g3g150g138g135g3g6g8g17g486g6g8g17g8g15g8g6g3g16g131g144g131g137g135g143g135g144
18、g150g3g6g135g144g150g148g135g3g138g131g149g3g150g138g135g3g149g131g143g135g3g149g150g131g150g151g149g3g131g149g3g150g138g135g3g145g136g136g139g133g139g131g142g3g152g135g148g149g139g145g144g149g484g3g3g6g8g17g3g143g135g143g132g135g148g149g3g131g148g135g3g150g138g135g3g144g131g150g139g145g144g131g142g
19、3g149g150g131g144g134g131g148g134g149g3g132g145g134g139g135g149g3g145g136g3g4g151g149g150g148g139g131g481g3g5g135g142g137g139g151g143g481g3g5g151g142g137g131g148g139g131g481g3g6g148g145g131g150g139g131g481g3g6g155g146g148g151g149g481g3g6g156g135g133g138g3g21g135g146g151g132g142g139g133g481g3g7g135g1
20、44g143g131g148g141g481g3g8g149g150g145g144g139g131g481g3g9g139g144g142g131g144g134g481g3g9g145g148g143g135g148g3g28g151g137g145g149g142g131g152g3g21g135g146g151g132g142g139g133g3g145g136g3g16g131g133g135g134g145g144g139g131g481g3g9g148g131g144g133g135g481g3g10g135g148g143g131g144g155g481g3g10g148g13
21、5g135g133g135g481g3g11g151g144g137g131g148g155g481g3g12g133g135g142g131g144g134g481g3g12g148g135g142g131g144g134g481g3g12g150g131g142g155g481g3g15g131g150g152g139g131g481g3g15g139g150g138g151g131g144g139g131g481g3g15g151g154g135g143g132g145g151g148g137g481g3g16g131g142g150g131g481g3g17g135g150g138g1
22、35g148g142g131g144g134g149g481g3g17g145g148g153g131g155g481g3g19g145g142g131g144g134g481g3g19g145g148g150g151g137g131g142g481g3g21g145g143g131g144g139g131g481g3g22g142g145g152g131g141g139g131g481g3g22g142g145g152g135g144g139g131g481g3g22g146g131g139g144g481g3g22g153g135g134g135g144g481g3g22g153g139g
23、150g156g135g148g142g131g144g134g481g3g23g151g148g141g135g155g3g131g144g134g3g24g144g139g150g135g134g3g14g139g144g137g134g145g143g484g3g3g3g3g3g8g24g21g18g19g8g4g17g3g6g18g16g16g12g23g23g8g8g3g9g18g21g3g22g23g4g17g7g4g21g7g12g29g4g23g12g18g17g3g6g18g16g12g23g50g3g8g24g21g18g19g50g8g17g3g7g8g3g17g18g2
24、1g16g4g15g12g22g4g23g12g18g17g3g8g24g21g18g19g34g12g22g6g11g8g22g3g14g18g16g12g23g8g8g3g9g111g21g3g17g18g21g16g24g17g10g3g3g3g3CEN-CENELECg3Management Centre: Avenue Marnix 17, B-1000 Brussels g825g3g884g882g883g888g3g6g8g17g3 g4g142g142g3g148g139g137g138g150g149g3g145g136g3g135g154g146g142g145g139g
25、150g131g150g139g145g144g3g139g144g3g131g144g155g3g136g145g148g143g3g131g144g134g3g132g155g3g131g144g155g3g143g135g131g144g149g3g148g135g149g135g148g152g135g134g3g153g145g148g142g134g153g139g134g135g3g136g145g148g3g6g8g17g3g144g131g150g139g145g144g131g142g3g16g135g143g132g135g148g149g484g3g21g135g136
26、g484g3g17g145g484g3g8g17g3g883g888g889g885g889g483g884g882g883g888g3g8BS EN 16737:2016EN 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 operations 6 4.2 Sizes 6 4.3 Pr
27、ocessing 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 5.6 Distortion 11 5.6.1
28、 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 (informative) Tropical hardwo
29、od species and their densities . 14 BS EN 16737:2016EN 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 given the status of a national s
30、tandard, 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 be the subject of patent ri
31、ghts. 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 Regulations, the national standa
32、rds 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, Italy, Latvia, Lithuania, Lux
33、embourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 16737:2016EN 16737:2016 (E) 4 1 Scope This European Standard specifies a method of strength grading tropical hardwood visually for structural use. The
34、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 lengths. Characteristics related to
35、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 and are indispensable for its appl
36、ication. 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 classes EN 350-2, Durability of wood a
37、nd 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 EN 844-3, Round and sawn timber -
38、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, Round and sawn timber - Termino
39、logy - 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 timbers used in Europe EN 14081-1, Timb
40、er 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 14081-1 and the nomenclature in EN 135
41、56 and the following apply. 3.1 bark pocket bark that is partly or wholly enclosed in the wood BS EN 16737:2016EN 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 3.4 brittleheart wood characterized by
42、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 incline alternately in opposite directions t
43、hat 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 5 mm 3.10 resin pocket lens-shaped cav
44、ity 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 axis of the piece of timber 3.13 thick
45、ness lesser dimension perpendicular to the longitudinal axis of the piece of timber Note 1 to entry: This is the size of the edge. BS EN 16737:2016EN 16737:2016 (E) 6 3.14 tropical hardwood wood of angiosperm trees of the botanical group dicotyledons whose natural distribution lies substantially Sou
46、th 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 greater dimension perpendicular to the longitudi
47、nal 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, or people working within a company under t
48、he 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 cross-sectional area at the time of grading s
49、hall 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 g950 to 100 mm, or; b) 10 mm 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 to conform to the permissibl
