1、 ISO 2014 Timber structures Determination of characteristic values Part 2: Sawn timber Structures en bois Dtermination des valeurs caractristiques Partie 2: Bois massif INTERNATIONAL STANDARD ISO 12122-2 First edition 2014-03-01 Reference number ISO 12122-2:2014(E) ISO 12122-2:2014(E)ii ISO 2014 All
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4、witzerland ISO 12122-2:2014(E) ISO 2014 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Symbols and abbreviated terms . 1 5 Reference Population 1 6 Sampling 2 6.1 Sampling method 2 6.2 Sample size . 2 7 Sample cond
5、itioning . 2 8 Test data 2 8.1 Test method . 2 8.2 Test data compatible with product description . 2 9 Evaluation of characteristic values for structural properties . 3 9.1 Structural properties . 3 9.2 Characteristic modulus of elasticity . 3 9.3 Characteristic values of strength . 3 10 Report 3 An
6、nex A (informative) Commentary . 4 Bibliography 7 ISO 12122-2:2014(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO techni
7、cal committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely w
8、ith the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria neede
9、d for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent r
10、ights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in
11、this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barrier
12、s to Trade (TBT) see the following URL: Foreword - Supplementary information The committee responsible for this document is ISO/TC 165, Structural Timber. ISO 12122 consists of the following parts, under the general title Timber structures Determination of characteristic values: Part 1: Basic requir
13、ements Part 2: Sawn timberiv ISO 2014 All rights reserved ISO 12122-2:2014(E) Introduction This International Standard sets out a framework for establishing characteristic values from test results on a sample drawn from a clearly defined reference population of sawn timber. The characteristic value
14、is an estimate of the property of the reference population with a consistent level of confidence prescribed in the standard. This part of ISO 12122 is to be used in conjunction with ISO 12122-1. This part of ISO 12122 permits the evaluation of characteristic values on testing on commercial sized spe
15、cimens of sawn timber. This part of ISO 12122 is applicable to structural sawn timber. In some cases, characteristic values determined in accordance with this part of ISO 12122 can be modified to become a design value. This part of ISO 12122 has the following annexes: Annex A presents a commentary o
16、n this part of ISO 12122. ISO 2014 All rights reserved v Timber structures Determination of characteristic values Part 2: Sawn timber 1 Scope This International Standard gives methods for the determination of characteristic values for a defined population of sawn timber products, calculated from tes
17、t values. It presents methods for the determination of a) characteristic value of mean-based properties, and b) characteristic value of 5th percentile-based properties. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensa
18、ble 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. ISO 12122-1, Timber structures Determination of characteristic values Part 1: Basic requirements 3 T erms a nd defi
19、niti ons For the purposes of this document, the terms and definitions given in ISO 12122-1 apply. 4 Symbols and abbreviated terms Symbols defined in the relevant ISO product or test standard shall be used. Other symbols are defined in ISO 12122-1. 5 Reference Population In addition to the requiremen
20、ts for definition of the reference population in ISO 12122-1, the following attributes of sawn timber may be described: a) climate or climate range of growing region; b) altitude or altitude range of growing region; c) specific silvicultural practices used in the growing region; d) soil type or rang
21、e of soil types of growing region; e) sawing patterns (e.g. backsawn or quartersawn, core wood included or excluded); f) seasoning method (if seasoned); g) grading or production method. INTERNATIONAL ST ANDARD ISO 12122-2:2014(E) ISO 2014 All rights reserved 1 ISO 12122-2:2014(E) 6 Sampling 6.1 Samp
22、ling method The sampling method shall comply with the performance objective of sampling defined in ISO 12122-1. Representation of each of the variants in the sample shall approximate the representation of the same variants in the reference population. The sampling method shall be documented in the r
23、eport as detailed in Clause 10 and this documentation shall indicate a response to each of the identified attributes of the reference population listed in compliance with Clause 5 in this part of ISO 12122 and in ISO 12122-1. 6.2 Sample size The sample size shall comply with requirements of ISO 1212
24、2-1 and shall take into account the coefficient of variation (V) expected for the sawn timber in the reference population. NOTE 1 See notes under the relevant clause in ISO 12122-1. Sawn timber properties generally have larger population coefficient of variation (V), and should therefore have a larg
25、er sample size. NOTE 2 ISO 12122-1 gives some guidance on selecting sample size. 7 Sample conditioning The sample storage and testing environment shall reflect conditioning in accordance with the definition of the reference population as indicated in ISO 12122-1. 8 Test data 8.1 Test method The test
26、 data shall be obtained from a) ISO 13910, or b) a standard test method appropriate for the sawn timber reference population provided equivalency factors with ISO 13910 can be established. NOTE 1 See notes under the relevant clause in ISO 12122-1. NOTE 2 Test methods involve many variables that will
27、 affect results including loading configuration and rates, specimen positioning ,and measurement methods. The level of precision of these variables must be appropriate to the objectives of the testing and the adjustments required in 8.2. 8.2 Test data compatible with product description Where the ch
28、aracteristic value is applicable to a standard size or moisture content, adjustments to the raw test data may be required. Any adjustment shall be in accordance with ISO 12122-1 and shall be detailed in the report. NOTE These adjustments include those required to pool data from different test progra
29、ms as outlined in ISO 12122-1.2 ISO 2014 All rights reserved ISO 12122-2:2014(E) 9 Evaluation of characteristic values for structural properties 9.1 Structural properties For sawn timber, material properties shall be evaluated. These shall include modulus of elasticity and characteristic strengths.
30、NOTE These are properties which when multiplied by a geometric parameter give a component capacity or component stiffness. Examples of these properties include characteristic modulus of elasticity and characteristic bending strength. Determination of the characteristic values for structural properti
31、es shall be in accordance with ISO 12122-1. 9.2 Characteristic modulus of elasticity Characteristic modulus of elasticity value for serviceability shall be the average of the test values evaluated in accordance with ISO 12122-1, and in the case of its use in the ultimate limit state it shall be eith
32、er the average or the 5th percentile value. NOTE In some cases, where a reduction of modulus of elasticity is not already factored into the behaviour equation used for design, a 5th percentile value of modulus of elasticity can be required to design for beam or column stability. 9.3 Characteristic v
33、alues of strength 9.3.1 Characteristic bearing strength The characteristic values for bearing strength, both parallel and perpendicular to grain, shall be the mean property obtained from results of tests. 9.3.2 Other characteristic values for strength based on the 5th percentile test value The 75 %
34、lower single-sided confidence limit of the test 5th percentile value shall be evaluated. Suitable methods for evaluating the 5th percentile value of the test data and estimating the 75 % lower single- sided confidence limit are presented in ISO 12122-1. 10 Report The report shall comply with the req
35、uirements of ISO 12122-1. ISO 2014 All rights reserved 3 ISO 12122-2:2014(E) Annex A (informative) Commentary A.1 Commentary on scope This part of ISO 12122 presents methods for determining characteristic values for only sawn structural timber. It is to be read in conjunction with ISO 12122-1. This
36、part of ISO 12122 presents a uniform methodology for the evaluation of characteristic values that are consistent with the characteristic values found for other structural timber products. This part of ISO 12122 does not establish methods for the determination of design values. These can be determine
37、d based on characteristic values from test data, but for sawn timber will also incorporate safety factors to account for any or all of the following factors: Expected changes in product or product properties over a long period. These changes could be due to variations in timber resource quality, pro
38、duction methods, or quality of other raw materials; The complexity of the reference population. For example, where the reference population has a large number of producers who draw their resource over a large area, then the sampling may not effectively reflect all possible combinations of resource q
39、uality and production methods. In this way, the sample may not be truly representative and a safety factor may be applied to allow for that. A.2 Commentary on normative references No commentary. A.3 C ommentary on t erms and definitions No commentary. (See ISO 12122-1). A.4 Commentary on symbols No
40、commentary. (See ISO 12122-1). A.5 Commentary on reference population Characteristic values can be taken to represent the properties of the material from which the sample was taken. The reference population is the definition of the parent population to which the characteristic properties are said to
41、 apply. ISO 12122-1 presents some general requirements for definition of the reference population, but some other features are known to influence the structural properties of sawn timber: The climate or climate range of the growing region is known to affect the density of the wood, branch sizes in t
42、he tree and hence knot sizes in the wood; The altitude of the growing region has been known to affect not only the properties of the sawn wood produced at those altitudes, but also the relationships between the characteristic values of the structural properties. In some cases, the topography can als
43、o influence structural properties;4 ISO 2014 All rights reserved ISO 12122-2:2014(E) Silvicultural practices can affect characteristics in the wood from which the sample was taken. This can include planting density, fertilization practices, pruning or trimming practices, and irrigation. Each of thes
44、e can influence growth rates of the trees and hence wood density branch size and branch configuration. These can affect the properties of the sawn timber that is produced from these logs; Soil type is also influential on growth rates and hence on wood density and growth characteristics. Normally, fo
45、rests have a range of soil types, but some regions can feature a predominance of one soil type (e.g. stony calcareous soils); Sawing patterns affect knot positions and alignment. Where a population has a predominant sawing pattern, this should be declared, as different sawing patterns may deliver pr
46、oducts with significantly different properties. In particular, the nature of the core wood (close to the pith) is different to the properties of the wood away from the pith. Hence, if core wood is excluded from a particular reference population, that should be stated in the definition of the referen
47、ce population; Temperature of seasoning can also have an influence on the structural properties of seasoned sawn timber. Range of seasoning temperatures and method of seasoning which can relate to the speed of moisture removal shall be declared; Many different technologies for stress-grading structu
48、ral product are available. The use of a particular grading technology can affect the properties of the product or the range of properties produced. ISO 12122-1 refers to the period over which the product was manufactured. In some cases, the time of year affects the properties of the production of sa
49、wn timber. This can relate to the temperature or moisture content of the wood at different stages of production, or it can be an effect of accessibility of different types of forest at different times of the year. The lists in both ISO 12122-1 and this part of ISO 12122 are examples, but the intent of this clause is that anything in the manufacture of the product that can affect the structural properties shall be included in the description. A.6 Commentary on sampling In general, sawn timber incorporates a large n
