1、BRITISH STANDARD BS6954-1: 1988 ISO3443/1: 1979 Tolerances for building Part 1: Recommendations for basic principles for evaluation and specification UDC721.013:624+69:69.032+691:001.818+(083.95):621.753.1BS6954-1:1988 This British Standard, having been prepared under the directionof the Basic Data
2、and Performance Criteria for Civil Engineering and Building Structures Standards Committee, was published under the authority of the Board of BSI and comes intoeffect on 29 February 1988 BSI04-1999 The following BSI references relate to the work on this standard: Committee reference BDB/4 Draft for
3、comment77/14091DC ISBN 0 580 16504 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Basic Data and Performance Criteria for Civil Engineering and Building Structures Standards Committee (BDB/-) to Technical Committee BDB/4, upon which t
4、he following bodies were represented: Association of County Councils British Standards Society Building Employers Confederation Chartered Institution of Building Services Engineers Concrete Society Department of Education and Science Department of the Environment (Building Research Establishment) De
5、partment of the Environment (Property Services Agency) Incorporated Association of Architects and Surveyors Institute of Building Control Institute of Clerks of Works of Great Britain Inc. Institution of Civil Engineers Institution of Structural Engineers Institution of Water and Environmental Manag
6、ement (IWEM) National Council of Building Materials Producers Royal Institute of British Architects Royal Institution of Chartered Surveyors Amendments issued since publication Amd. No. Date of issue CommentsBS6954-1:1988 BSI 04-1999 i Contents Page Committees responsible Inside front cover National
7、 foreword ii 1 Scope and field of application 1 2 Reference 1 3 General 1 4 Sources of dimensional variability 2 5 Consequences of dimensional variability 2 6 Choice of tolerance values 2 Publications referred to Inside back coverBS6954-1:1988 ii BSI 04-1999 National foreword This Part of BS6954 has
8、 been prepared under the direction of the Basic Data and Performance Criteria for Civil Engineering and Building Structures Standards Committee. This Part of BS6954 together with Parts2 and3 form a revision of DD22:1972. BS6954-1, BS 6954-2 and BS6954-3 supersede DD22:1972, which is withdrawn. This
9、Part of BS6954 is identical with ISO3443/1-1979 “Tolerances for building Part 1: Basic principles for evaluation and specification”, published by the International Organization for Standardization (ISO). BS6954 comprises three Parts as follows: Part 1: Recommendations for basic principles for evalua
10、tion and specification; Part 2: Recommendations for statistical basis for predicting fit between components having a normal distribution of sizes; Part 3: Recommendations for selecting target size and predicting fit. BS6954 enables the nature of deviations from intended sizes to be taken into accoun
11、t when designing to achieve satisfactory fit. This Part of BS6954 describes the nature of deviations. Terminology and conventions. The text of the international standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions ar
12、e not identical with those used in British Standards; attention is drawn especially to the following. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. Cross-references. The Technical Committee has reviewed the provisions of IS
13、O2444 and ISO2445, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A related standard to ISO2444-1074 is BS1600 “Glossary of building and civil engineering terms” Subsection1.5.2:1987 “Jointing”. A British Standard does not
14、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 fro
15、nt cover, pagesi andii, pages1 and 2, 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.BS6954-1:1988 BSI 04-1999 1 1 Scope and field of applicat
16、ion This International Standard describes the nature of dimensional variability in building and the purposes for which it has to be quantified, and defines the factors to be taken into account in the evaluation, specification and verification of tolerances for the manufacture of building components
17、and for site work. It applies to components and buildings generally, including those designed in accordance with the principles of modular co-ordination. 2 Reference ISO2445, Joints in building Fundamental principles for design. Other standards regarding tolerances for building construction are pres
18、ently being prepared. 3 General The process of building construction presents specific problems in the field of tolerances and fits, which require detailed examination in relation to the technique of assembly, the performance requirements and the costs of the completed building. The creation under s
19、ite conditions of a large-scale geometric form, involving the assembly of dimensionally variable components by means of a sequence of measuring and positioning operations, can result in substantial variations from the designed size and shape (induced deviations). Coupled with this are the inevitable
20、 dimensional variations resulting from movements and changes of size of materials, which arise from extrinsic and intrinsic physico-chemical causes (inherent deviations). The object of international standardization in the field of tolerances and fits is to provide a coherent system by means of which
21、 a) dimensional and positional variabilities may be both analysed and allowed for in design; b) tolerances may be communicated clearly in specification; c) the sizes and shapes of components and buildings may be subjected to any necessary control measures during manufacture and construction. When bu
22、ilding components are located in relation to a continuous reference system (such as a modular grid), so that the structure is subjected to overall dimensional control, deviations of size, shape and position have to be absorbed within the jointing system. The consideration of tolerances for the manuf
23、acture of components and for the construction of buildings is therefore inseparable from the design of joints to provide the required dimensional flexibility (see ISO2445). This does not mean that all joints must necessarily have this capability, but it is necessary for deviations to be accommodated
24、 at some point; this may be achieved at the joints between individual components, or by the provision of special joints at intervals. In addition, tolerances should be considered in relation to the structural, aesthetic, legal and direct functional consequences of dimensional variability in order to
25、 achieve the overall quality required. Analysis of joint width variation is required for the determination of work sizes for components, so that they can be designed for use with jointing techniques of known dimensional flexibility. This applies equally to standard components and to purpose-made com
26、ponents. It may also be necessary to check the suitability of a standard component for use with the same or a different jointing technique in particular situations in building designs. The object in all cases is to ensure that assembly of the components is possible without unpredicted problems of fi
27、t, and that the joints achieve the required performances. If the analysis of induced deviations is based on statistical principles, a limited incidence of “misfit” is accepted in the design, the extent of which has to be decided in relation to the nature of the component and its jointing technique.
28、The specification of tolerances defining the limits of induced deviations that have been allowed for in the design has to be linked to methods of measurement by means of which compliance with the specification can be tested. The specification and verification of tolerances must refer to standard ref
29、erence conditions for measurement, to allow for the effects of inherent deviations on actual sizes. Tolerances may conveniently be specified in grades relating to methods of construction (materials, processes and techniques) and appropriate levels of accuracy. However, it is still necessary to exami
30、ne the dimensional compatibility of components used in particular situations even when their tolerances fall within the same grade, owing to the complex and unique factors governing the distribution of deviations.BS6954-1:1988 2 BSI 04-1999 4 Sources of dimensional variability 4.1 Induced deviations
31、 Any process of measurement, alignment or positioning is subject to some degree of variability due to human error and the limitations of measuring instruments. Such variabilities are termed “induced deviations”, and may be grouped as follows: a) manufacturing deviations: deviations of size and form
32、arising in the manufacture of components; b) setting-out deviations: deviations of size and position arising in the measuring and marking of dimensions on site; c) erection deviations: deviations of position and orientation arising in the positioning of components in relation to setting-out marks, a
33、nd in their horizontal and vertical alignment. The values of induced deviations will, in many cases, follow a normal, statistical distribution around the mean size or position (represented by the Gaussian curve for random errors). They may also exhibit a bias reflecting systematic, rather than rando
34、m, variability, such as progressive variation in size during the course of production, or a fixed deviation due to maladjustment of measuring instruments. Gross deviations due to serious measurement errors are generally disregarded in analysis, since the results will almost certainly be unacceptable
35、. Randomly occurring induced deviations may with advantage be treated according to statistical principles, so that account can be taken of the relative probability of small and large values, and may be expressed in terms of the standard deviation, as a measure of variability. Systematically occurrin
36、g deviations must generally be treated as definite, recurring values that apply to batches or groups of components or measurements. 4.2 Inherent deviations Virtually all materials exhibit dimensional changes due to physical or chemical causes. These are termed “inherent deviations”, and include reve
37、rsible and permanent changes due to variations in temperature, moisture content and stresses and to chemical reactions, etc. Settlement of foundations is also a source of permanent inherent deviations. 5 Consequences of dimensional variability Dimensional and positional deviations must be allowed fo
38、r in the design of buildings, building components and their joints, in respect of their effects on the following aspects: a) Performance of the building Variations in the sizes and shapes of spaces or openings and in the smoothness, flatness, horizontality and verticality of surfaces, including the
39、variations in joint width, 1)may affect directly the performance of the completed building. b) Assembly of components and performance of joints The variation in joint width due to induced and inherent deviations must be reflected in the evaluation of suitable work sizes for components, and in the ch
40、oice of jointing techniques with suitable width capabilities. c) Structural stability Dimensional and positional deviations may produce eccentricities of loading and reduced areas for load bearing; inherent deviations may, of themselves, induce stresses. d) Appearance Deviations of size, form and or
41、ientation of components and spaces, and variations in joint width may need to be controlled or concealed for the sake of appearance. e) Legal sizes Deviations may affect dimensions for which maximum or minimum sizes are laid down in regulations or legislation. 6 Choice of tolerance values Tolerances
42、 define the limits of induced deviations for which allowance has been made in design, and within which actual sizes are acceptable. Thus, they should be specified only for those dimensions or positions which are critical with respect to one or more of the consequences of variability listed in clause
43、5. The choice of values for tolerances reflects the economic balance between the cost of improving accuracy and the cost of accommodating deviations in the design. It is likely that the consideration of assembly and joint performance will be the most critical for assessing this balance, when there m
44、ay be a choice between fine tolerances with simple joints and coarse tolerances with complex joints. 1) The expression “joint width” is used in this International Standard as it is the term currently used. In this case, it should be made clear that it indicates the notion which is expressed in ISO24
45、44 by the less commonly used term “joint clearance” as follows: joint clearance: The distance between the joint faces of two components set side by side, i.e.the distance considered in order to achieve fit.BS6954-1:1988 BSI 04-1999 Publications referred to See national foreword.BS6954-1: 1988 ISO 34
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