00248652 PDF BRITISH STANDARD BS EN 26891 1991 ISO 6891 1983 Timber structures — Joints made with mechanical fasteners — General principles for the determination of strength and deformation characteri[.]
BRITISH STANDARD Timber structures — Joints made with mechanical fasteners — General principles for the determination of strength and deformation characteristics This European Standard EN 26891:1991 has the status of a British Standard BS EN 26891:1991 ISO 6891:1983 BS EN 26891:1991 Cooperating organizations The European Committee for Standardization, under whose supervision this European Standard was prepared, comprises the national standards organizations of the following Western European countries Austria Belgium Denmark Finland France Germany Greece Iceland Ireland Italy Luxemburg Netherlands Norway Portugal Spain Sweden Switzerland United Kingdom This British Standard was published under the authority of the Standards Board and comes into effect on 31 July 1991 © BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference TIB/51 Draft for comment 82/10367 DC ISBN 580 19856 Oesterreichisches Normungsinstitut Institut belge de normalisation Dansk Standardiseringsraad Suomen Standardisoimisliito, r.y Association franỗaise de normalisation Deutsches Institut für Normung e.V Hellenic Organization for Standardization Technological Institute of Iceland National Standards Authority of Ireland Ente Nazionale Italiano di Unificazione Inspection du Travail et des Mines Nederlands Normalisatie-instituut Norges Standardiseringsforbund Instituto Portugs da Qualidade Asociación Espola de Normalización y Certificación Standardiseringskommissionen i Sverige Association suisse de normalisation British Standards Institution Amendments issued since publication Amd No Date Comments BS EN 26891:1991 Contents Cooperating organizations National foreword Foreword Text of EN 26891 National appendix NA (informative) © BSI 01-2000 Page Inside front cover ii Inside back cover i BS EN 26891:1991 National foreword This British Standard has been prepared under the direction of the Structural Timber Standards Policy Committee It is the English language version of EN 26891:1991 “Timber structures — Joints made with mechanical fasteners — General principles for the determination of strength and deformation characteristics”, published by the European Committee for Standardization (CEN) EN 26891:1991 is identical with ISO 6891:1983 published by the International Organization for Standardization (ISO) Clause of EN 26891:1991 is technically equivalent to clauses 30 and 31 of BS 6948:1989 “Mechanically fastened joints in timber and wood based materials” A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages to 6, an inside back cover and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii © BSI 01-2000 EUROPEAN STANDARD EN 26891 NORME EUROPÉENNE February 1991 EUROPÄISCHE NORM UDC 694.14:624.011.1:624.042/044:621.882 Descriptors: Timber construction, joining, fasteners, characteristics, mechanical strength, deformation, loading English version Timber structures — Joints made with mechanical fasteners — General principles for the determination of strength and deformation characteristics (ISO 6891:1983) Structures en bois — Assemblages réalisés avec des éléments mécaniques de fixation — Principes généraux pour la détermination des caractéristiques de résistance et de déformation (ISO 6891:1983) Holzbauwerke — Verbindungen mit mechanischen Verbindungsmitteln — Allgemeine Grundsätze für die Ermittlung der Tragfähigkeit und des Verformungsverhaltens (ISO 6891:1983) This European Standard was approved by CEN on 17 January 1991 and is identical to the ISO standard as referred to 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 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 translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels © CEN 1991 Copyright reserved to all CEN members Ref No EN 26891:1991 E EN 26891:1991 Foreword Contents Based on the positive result of the Primary Questionnaire procedure, the Technical Board decided by Resolution BT 321/1989 to submit the International Standard ISO 6891:1983 “Timber structures — Joints made with mechanical fasteners — General principles for the determination of strength and deformation characteristics” to the formal vote The result was positive In accordance with the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxemburg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom Foreword Introduction Scope Field of application Reference Symbols Conditioning of test specimens Form and dimensions of test specimens Apparatus Loading procedure Test report Figure — Loading procedure Figure — Idealized load-deformation curve and measurements Page 3 3 3 3 Endorsement notice The text of the International Standard ISO 6891:1983 was approved by CEN as a European Standard without any modification © BSI 01-2000 EN 26891:1991 Introduction Developments in the field of load-bearing timber structures require that joints made with mechanical fasteners be tested to obtain information about their strength and deformation (slip) characteristics This International Standard lays down general principles which should be followed in order to achieve comparability of results from investigations carried out in different laboratories Standard rules for the determination of characteristic strengths for particular types of mechanical fasteners will be given in separate International Standards This International Standard is based on Joint Recommendations from Working commission W18, Timber Structures, of CIB1) and Committee 3TT, Timber Testing, of RILEM2), who will also prepare the basis for the above-mentioned supplementary International Standards Scope This International Standard lays down general principles for the determination of the strength and deformation (slip) characteristics of joints made with mechanical fasteners Field of application This International Standard is applicable to joints made with mechanical fasteners used in statically loaded timber structures Detailed procedures appropriate to joints made with specific fasteners will be given in separate International Standards The principles can also be used for the testing of other joints It is recognized that for some special types of joints not covered by International Standards, modification of the test procedure may be necessary Reference ISO 554, Standard atmospheres for conditioning and/or testing — Specifications Symbols F: applied load, in newtons Fest : estimated maximum load, in newtons Fmax : maximum load, in newtons k: slip modulus, in newtons per millimetre v: joint slip, in millimetres Subscripts for the joint slip, v, relate to load points in Figure and are defined in clause Conditioning of test specimens Attention should be paid to the conditioning of the timber before the manufacture of the joint and also to the conditioning of the joints as a whole before testing The conditioning should be conducted in such a way that the test conditions correspond in a realistic manner to the conditions in joints in structures as regards the influence of the moisture content on the strength properties of the timber and the occurrence of gaps, etc., through shrinkage Detailed requirements for specimens made with specific types of fasteners will be given in separate International Standards.3) Where the purpose of testing is to compare joints under similar conditions, the standard atmosphere 20/65 according to ISO 554 should be used for conditioning Form and dimensions of test specimens The test joints shall be of such realistic form and dimensions that the necessary information about the strength and deformation of joints in service can be obtained Detailed information about the form and dimensions of the test specimens suitable for different types of mechanical fasteners will be given in separate International Standards Apparatus In addition to equipment for measuring the geometry of the test specimens, moisture content, etc., the following shall be available: a) a testing machine able to apply and record load with an accuracy of ± % of Fest or better; 1) International Council for Building Research, Studies and Documentation International Union of Testing and Research Laboratories for Materials and Structures 3) Test methods for joints made with punched metal plate fasteners, nails and staples will form the subject of future International Standards 2) © BSI 01-2000 EN 26891:1991 b) equipment to measure joint slip under load with an accuracy of ± % or better, or for slips of less than mm with an accuracy of ± 0,02 mm The equipment shall ensure that eccentricities, twist, etc have no influence on the measurements.4) Loading procedure 8.1 Estimation of maximum load The estimated maximum load, Fest, for the type of joint to be tested shall be determined on the basis of experience, calculation or preliminary tests, and should be adjusted as required in 8.6 8.2 Application of load The loading procedure shown in Figure should generally be followed The load shall be applied up to 0,4 Fest and maintained for 30 s The load shall then be reduced to 0,1 Fest and maintained for 30 s Thereafter the load shall be increased until the ultimate load or slip of 15 mm is reached.5) Below 0,7 Fest a constant rate of load or slip corresponding to 0,2 Fest per minute ± 25 % shall be used Above 0,7 Fest, a constant rate of slip shall be used; so adjusted that the ultimate load or a slip of 15 mm is reached in to additional testing time (total testing time about 10 to 15 min) The test may be stopped when the ultimate load is reached, or when the slip is 15 mm For particular tests, the preload cycle up to 0,4 Fest may be omitted with a corresponding adjustment to the total testing time 8.3 Measurement of slip The slip measurements v01, v04, v14, v11, v21, v24, v26 and v28 shown in Figure shall be recorded for each test specimen The slip at maximum load, Fmax, shall also be recorded When a load/slip diagram is not available, measurements of slip should be taken at each 0,1 Fest increment of load (see Figure 1) 8.4 Measurement of load The load reached before or at a slip of 15 mm, shall be recorded as the maximum load, Fmax, for each specimen Figure — Loading procedure 4) Equipment that can continuously record load and slip is recommended; exceptionally, slips may be measured at chosen load levels provided the measurements can be made without significantly influencing the continuity of load application A sufficient number of load levels should be chosen to ensure that the calculations (see 8.5) and the adjustments (see 8.6) can be made 5) The requirement that the load be maintained constant for 30 s at 0,4 and 0,1 Fest is to permit adequate time for the loading to be reversed, it is not intended to provide information on creep behaviour © BSI 01-2000 EN 26891:1991 Figure — Idealized load-deformation curve and measurements 8.5 Calculations From the recorded measurements, the following values, if relevant, shall be determined for each test: 1) maximum load Fmax 2) estimated maximum load Fest 3) initial slip vi = v04 4) modified initial slip 5) joint settlementa 6) elastic slip 7) initial slip modulus ki = 0,4 Fest/vi 8) slip modulus ks = 0,4 Fest/vi,mod 9) slip at 0,6 Fmax v0,6 vs = vi – vi,mod 10) modified slip at 0,6 Fmax v0,6, mod = v0,6 – v24 + vi, mod 11) slip at 0,8 Fmax v0,8 12) modified slip at 0,8 Fmax v0,8, mod = v0,8 – v24 + vi, mod If practical, the complete load/slip diagram should also be given NOTE The values calculated for 9) to 12) above relate to the actual value of Fmax for each of the tests If a continuous load/slip diagram is available, these values may be obtained directly at the required load level If only readings of slip at increments of Fest are available, the values should be obtained by interpolation 8.6 Adjustment If, during the execution of the tests, the mean value of the maximum load of the tests already carried out deviates by more than 20 % from the estimated value, Fest, then Fest should be adjusted correspondingly for subsequent tests The values of maximum load already determined may be accepted without adjustment as part of the final results In this case, the values of slip and slip moduli determined in 3) to 8) of 8.5 should be adjusted to correspond to the adjusted values of Fest a It should be noted that many load-slip curves are initially convex upwards so that vs will be negative © BSI 01-2000 EN 26891:1991 Test report The test report shall include the following information: a) species, density and relevant strength properties of the timber; b) quality, strength properties and surface finish of the materials of the fasteners (including anti-corrosive protection); c) dimensions of the joints, size and number of fasteners, details of gaps between members; d) conditioning of timber and test specimens before and after manufacture, moisture content of the timber at manufacture and at test, fissures etc; e) the loading procedure used (by reference to this International Standard) and a statement of any deviations; f) individual test results and any relevant information regarding adjustments, mean values and standard deviations, and descriptions of the modes of failure © BSI 01-2000 BS EN 26891:1991 National appendix NA (informative) The United Kingdom participation in the preparation of this European Standard was entrusted by the Structural Timber Standards Policy Committee to Technical Committee TIB/51 upon which the following bodies were represented: British Timber Merchants’ Association British Woodworking Federation Council for the Forest Industries of British Columbia Department of the Environment (Building Research Establishment) Forestry Commission Institute of Building Control National House-building Council Royal Institute of British Architects Southern Pine Marketing Council Swedish Finnish Timber Council Ltd Timber Research and Development Association Timber Trade Federation Trussed Rafter and Fabricators Association UK Softwood Sawmillers’ Association © BSI 01-2000 BS EN 26891:1991 ISO 6891:1983 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an 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