1、BS EN 16784:2016Timber structures Testmethods Determination ofthe long term behaviour ofcoated and uncoated dowel-type fastenersBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS EN 16784:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implement
2、ation of EN 16784:2016.The UK participation in its preparation was entrusted to TechnicalCommittee B/518, Structural timber.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a c
3、ontract. Users are responsible for its correctapplication. The British Standards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 87197 9ICS 91.080.20Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the au
4、thority of theStandards Policy and Strategy Committee on 31 July 2016.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS EN 16784:2016EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 16784 June 2016 ICS 91.080.20 English Version Timber structures - Test methods - Determ
5、ination of the long term behaviour of coated and uncoated dowel-type fasteners Structures en bois - Mthodes dessai - Dtermination du comportement long terme des lments de fixation de type tige, revtus ou non Holzbauwerke - Prfverfahren - Bestimmung des Langzeitverhaltens beschichteter und unbeschich
6、teter stiftfrmiger Verbindungsmittel This European Standard was approved by CEN on 8 April 2016. 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-
7、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 European Standard exists in three official versions (English, French, German). A version in any other language made by translati
8、on 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 are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, F
9、ormer Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COM
10、IT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2016 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 16784:2016 EBS EN 16784:2016EN 16784:2016 (E) 2 Conten
11、ts Page European foreword . 3 1 Scope 4 2 Normative references 4 3 Terms and definitions . 4 4 Symbols and abbreviations . 4 5 Sampling . 5 5.1 Timber . 5 5.2 Fasteners 5 6 Test method 6 6.1 General 6 6.2 Conditioning 6 6.3 Fabrication of the specimens 6 6.3.1 Fastener axis perpendicular to the grai
12、n . 6 6.3.2 Fastener axis parallel to the grain 6 6.4 Test procedure . 7 6.5 Testing for duration of withdrawal load 8 7 Expression of the results 8 7.1 Load duration factor for withdrawal . 8 7.2 Test report . 9 Bibliography . 11 BS EN 16784:2016EN 16784:2016 (E) 3 European foreword This document (
13、EN 16784:2016) 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 standard, either by publication of an identical text or by endorsement, at the latest by December 2016, an
14、d conflicting national standards shall be withdrawn at the latest by December 2016. 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. Ac
15、cording 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, Former Yugoslav Republic of Macedonia, France, Germa
16、ny, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 16784:2016EN 16784:2016 (E) 4 1 Scope This European Standard specifies a test metho
17、d for the determination of the long duration withdrawal strength of coated and uncoated dowel-type fasteners in structural timber and timber products and wood based products for structural application. The method applies to all types of nails, screws and staples. 2 Normative references The following
18、 documents, in whole or in part, are normatively referenced in this document and 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 1382, Timber Stru
19、ctures Test methods Withdrawal capacity of timber fasteners EN 26891:1991, Timber structures Joints made with mechanical fasteners General principles for the determination of strength and deformation characteristics (ISO 6891:1983) EN ISO 8970, Timber structures Testing of joints made with mechanica
20、l fasteners Requirements for wood density (ISO 8970) ISO 13061-1, Physical and mechanical properties of wood Test methods for small clear wood specimens Part 1: Determination of moisture content for physical and mechanical tests ISO 13061-2, Physical and mechanical properties of wood Test methods fo
21、r small clear wood specimens Part 2: Determination of density for physical and mechanical tests 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 reference withdrawal strength mean (50 % fractile) withdrawal strength of the tests carried out in
22、 accordance with EN 1382 3.2 load level percentage of the reference withdrawal strength 4 Symbols and abbreviations a staple crown width, in millimetres (see Figure 1) d is the outer thread diameter for screws, the diameter of the smooth plain part of a round nail or for staples the diameter of the
23、wire (transformed to a round cross-section) (see EN 14592) Fmaxmaximum withdrawal load, in newtons kd,Tduration of load factor for withdrawal load lpthe effective depth of penetration of fastener, in millimetres. For smooth nails and staples this includes the point. For profiled nails and screws onl
24、y the penetration depth of the profiled part. In the case of partly or completely resin coated fasteners only the depth of penetration of the coated BS EN 16784:2016EN 16784:2016 (E) 5 part. crnangle between the direction of a staple crown and the grain direction or the main direction of the timber
25、or wood based products, respectively, in degrees (see Figure 2) Tfelapsed time to failure in minutes for a certain test specimen T time to failure Figure 1 Staple dimensions Figure 2 Angle between the staple direction and the grain direction 5 Sampling 5.1 Timber The range of density of the test pie
26、ces shall be representative of the density of the mechanical class or range of product to which they belong. The sampling of test pieces shall be done in accordance with EN ISO 8970. 5.2 Fasteners The technical specification of the nails, screws and staples shall be established. BS EN 16784:2016EN 1
27、6784:2016 (E) 6 6 Test method 6.1 General The moisture content and density of the timber at test shall be determined as specified in ISO 13061-1 and ISO 13061-2 as appropriate. 6.2 Conditioning The test pieces shall be manufactured with the timber products at an equilibrium moisture content correspo
28、nding to (20 2) C and (80 5) % relative humidity. The material is conditioned when it attains constant mass. Constant mass is considered to be attained when the results of two successive weightings, carried out at an interval of 6 h, do not differ by more than 0,1 % of the mass of the material. For
29、certain investigations, other moisture conditioning can be appropriate and shall be reported. NOTE The high moisture content reflects the worst design situation where wet timber is installed that dries out in service. 6.3 Fabrication of the specimens 6.3.1 Fastener axis perpendicular to the grain Th
30、e axis of the fastener shall be perpendicular to the timber surface. The insertion of fasteners shall follow normal preparation (e.g. pre-boring) and practice. The position of the fastener is such that no eccentricities occur in transferring the load to the timber. The width and depth of the test pi
31、ece in the direction of insertion of the fastener shall be equal and at least lp + 5d for nails and screws (see Figure 3), and for staples at least 10d. Where the test pieces are of solid timber or glued laminated timber, the fasteners shall be inserted irrespective of the direction of the growth ri
32、ngs. In addition for staples, half of the tests shall be carried out with crn = 0 and the other half with crn = 90. Figure 3 Withdrawal test pieces - load perpendicular to grain 6.3.2 Fastener axis parallel to the grain The test piece shall comply with Figure 4. The fastener shall be driven into the
33、 end grain to a penetration of between 8d and 20d and shall be positioned in the centre line of the timber specimen as to prevent any eccentricities in the load transfer. A depth of penetration of at least 12d is appropriate to fasteners of d less than 2 mm. BS EN 16784:2016EN 16784:2016 (E) 7 NOTE
34、The range of depth penetration is given so that the depth of penetration used in the test can be decided depending on the withdrawal resistance EN 1382 and the tensile capacity of the fastener. The cross-sectional dimensions of the test piece shall be equal and at least 10d (see Figure 4). For stapl
35、es, the dimensions parallel and perpendicular to the crown shall be equal and at least 6a and 4a, respectively (see Figure 4). The test piece dimension parallel to grain shall be at least 2lp + 5d for nails and screws, and for staples at least 2lp + 3a. Figure 4 Withdrawal test pieces - load paralle
36、l to grain 6.4 Test procedure The apparatus used shall be as required in EN 26891:1991, Clause 7. Tests are carried out in an environment corresponding to (20 2) C and (65 5) % relative humidity. If these conditions are not maintained during the test, they shall be reported. Test of thermo plastic a
37、dhesive coatings shall be performed at elevated temperatures. NOTE 1 The design rules in EN 1995-1-1 are valid up to 60 C. Determine the depth of the fastener penetration lp. Place the test specimen in a device ensuring the application of the withdrawal force along the axis of the fastener or the ax
38、es of the staple legs. Any part of the supports that hold the timber test specimen shall be not closer to the axis of the fastener than 3d for nails and screws and a for staple. The loading procedure is in accordance with EN 26891 were the load shall be applied with constant increments until the req
39、uired load level is attained. The required load is held constant until failure or termination of the test. The time to failure or termination of the test shall be recorded. NOTE 2 Usually the test specimens are mounted in strings in a rig and loaded by dead load. To keep the dead load within limits
40、a level arm can be applied. It is important that the lever arm can function with or without negligible friction at the hinges. BS EN 16784:2016EN 16784:2016 (E) 8 6.5 Testing for duration of withdrawal load To determine the load duration withdrawal factor at least 10 test specimens are loaded to at
41、least two of the following load levels: 20 %, 30 %, 40 %, 55 %, 60 %, 65 %, 70 %, or 80 % of the reference withdrawal strength. NOTE Best practice is to choose very different load levels appropriate to the aim of the test. The reference withdrawal strength is the mean (50 % fractile) of the withdraw
42、al strength established by tests in accordance with EN 1382. For the reference withdrawal strength perpendicular to grain the average of the withdrawal strength in radial and tangential direction is taken. If these tests were carried out with the insertion direction at random with respect to the rad
43、ial and tangential direction the resulting mean withdrawal strength can directly be taken as reference withdrawal strength. If test specimens fail during the initial loading, this load level shall be discarded from the investigation. For all tests, record the time to failure in minutes expressed to
44、the nearest 1% of the elapsed time, Tf. The tests shall continue until at least 7 test specimens at each load level have failed. 7 Expression of the results 7.1 Load duration factor for withdrawal The load duration for withdrawal at a given time is defined as the ratio of the load level that results
45、 in failure at that time, to the mean reference withdrawal strength. The load duration factor for withdrawal, kd,Tshall be determined by plotting the load level against log10time (T) to failure. Calculate the mean time to failure at each load level for those test specimens which have failed. Calcula
46、te the linear regression line treating the load level as the independent variable, to provide Formula (1) of the form: = LogT c mLL (1) where c is the intercept on the vertical axis; m is the slope; LL is the load level, in percent; T is the time to failure, in minutes. Formula (1) is then rearrange
47、d algebraically to give the more traditional form: d,TlogLL = e - f T = k (2) where ce=m1f=m(3) BS EN 16784:2016EN 16784:2016 (E) 9 The extrapolated load level for a particular life is then calculated using Formula (2) and expressed to three significant figures. An example for a ten year life (log T
48、= 6,72) is illustrated in Figure 5. Key X is log time Y is the load level Figure 5 Example of a load duration regression curve The symbol, kd,Tshall embrace the time of loading and the service class to which it applies. NOTE An example of a predicted kd,T value at 10 years calculated from the durati
49、on of load testing carried out under service class 1 conditions is as follows: kd,10y,SC1Where separate tests have been performed parallel and perpendicular to grain direction, separate load duration withdrawal factors shall be calculated. 7.2 Test report The test report shall contain the following information: a) a reference to this European Standard; b) sampling and loading procedure and test set-up; c) specification of the timber; d) dimensions, density, moisture content and conditioning for the test; e) diagram showi
