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1、INTERNATIONAL smmm INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEX+lJYHAPOflHAR OPl-AHM3AyMR i-l0 CTAHAAPTM3ALjMi-l Tolerances for building - Part 3: Procedures for selecting target size and predicting fit Tol 2) sizes of components and in situ work; 3
2、) joint clearances; 4) probability of fit; and they can be used whether 2),3) or 4) above is the unknown to be calculated. The procedures assume that values for I) above have been established by measurement surveys and relate target sizes to coordinating sizes using the concepts of “extension” and “
3、deduction”. See 4.4 and 4.5. The procedures also enable a target size to be calculated for any standard component, such that the component will have an optimal probability of fit in all its applications. Worked examples are given in annex B. Part 4 of IS0 3343 is structured primarily to meet the nee
4、ds in b) above. It is therefore concerned primarily with the design of buildings in which components (including standard com- ponents) are used, and is aimed primarily at building designers who, as engineers, can be expected to be mathematically and statistically competent. It is to meet these aims
5、that part 4 of IS0 3443 deals with - methods for predicting deviations and specifying tolerances to obtain a particular desired total accuracy in an assembly; - the effect of specified tolerances on expected size variability; - the basis for optimization of tolerances for each par- ticular assembly
6、and its elements. Part 4 of IS0 3443 presupposes calculations only for assemblies with elements of one dimension, such as beams and columns, for the sake of simplicity. However, tables for common cases with elements of two and three dimensions (panels, etc.) are given in the annex to part 4. 1 Scope
7、 This part of IS0 3443 provides a basis for relating joint clearances and target sizes and for the prediction of fit within the context of dimensional coordination, including modular coordination. 1) This part deals with accuracy in terms of target size and limits of size (e.g. upper and lower limit
8、s of component size). Alternatively, accuracy can be defined in terms of permitted deviations in relation to a reference size - usually identical with the target size. See IS0 1803-l. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Techni
9、cal Standards 1/9972545001 Not for Resale, 04/21/2007 09:09:32 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 3443-3 : 1987 (E) 2 Field of application This part of IS0 3443 is for use by component manufacturers when determining target sizes for standard components; it
10、is also for use by building designers when determining target sizes for construction on site, assessing the applicability of standard components or determining target sizes for non- standard components. The applicability of the procedures is further described in 6.1 and 6.2. 3 References IS0 1791, M
11、odular co-ordination - Vocabulary IS0 1603-1, Tolerances for building - Vocabylaty - Part 1: General terms. IS0 1803-2, Tolerances for building - Vocabulary - Part 2: Derived terms. IS0 3443-l I Tolerances for building - Part I: Basic principles for evaluation and specification. IS0 3443-2, Toleranc
12、es for building - Part2: Statistical basis for predicting fit between components having a normal distribution of sizes. IS0 3443-4, Tolerances for building - Part 4: Methods for predicting deviations of assemblies and the allocation of tolerances. 3 Coordinating size A. a 0 4 Definitions For the pur
13、poses of this part of IS0 3443, the definitions given in IS0 1791 and IS0 1803, and as follows, are applicable. 4.1 systematic deviation: Mean deviation of the type of space or componentl) considered (to be found by measure- ment of a representative sample of constructed spaces, or of componentsl),
14、of the type considered). See IS0 3443-2. 4.2 standard deviation: Positive square root of the mean of the squares of the deviations. 4.3 space target size: Intended size of an opening formed between two erected componentsV NOTE - The size is equal to the sum of the coordinating size of the space and
15、its extension. 4.4 extension: Amount by which the target size of a space exceeds its coordinating size (see figure I). 4.5 deduction: Amount by which the target size of a com- ponentl) is less than its coordinating size (see figure 1). Coordinating size Csp -mm- I Target size of component Wcomp I Sp
16、ace target size ( = coordinating size plus extension) Extension = a + a = Deduction for components “A” Coordinating size , a I 7 A a The deduction, for the components “A” forming the space, provides the extension in the space and so produces a target size, for that space, that components “B” are to
17、occupy. Figure 1 - Illustration of extension and deduction 1) In certain cases, in situ work may be considered as ii it were a component. 2 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 0
18、4/21/2007 09:09:32 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 3443-3 :I987 (El 5 Symbols C SP D E E max E min J J max J min j Jmax jmin P komp PSP n Q 4 r acomp QSP W camp W max W min Space coordinating size Deduction Extension Maximum extension Minimum extension J
19、oint clearance (required by a chosen jointing tech- nique) Maximum joint clearance (required by a chosen joint- ing technique) Minimum joint clearance (required by a chosen joint- ing technique) Predicted joint clearance Maximum predicted joint clearance Minimum predicted joint clearance Systematic
20、deviation Systematic deviation of componentl) Systematic deviation of space The number of components occupying a constructed space Multiplier of the standard deviation corresponding to a selected probability of joint clearances being too large Multiplier of the standard deviation corresponding to a
21、selected probability of joint clearances being too small The mean of correlation coefficients between the sizes of all possible pairs of components The standard deviation of the total2) dimensional variability, induced in manufacture of a component, along the axis considered The standard deviation o
22、f the total2) dimensional variability that is characteristic of the type of space, along the axis considered Target size of componentl) Component size - upper target size limit) Component size - lower target size limit11 6 Basis of procedures Induced and inherent deviations3) (see IS0 3443-l 1 poten
23、tially prevent the achievement, on site, of joint clearances that are within the working limits of a jointing technique. The procedures recommended in this part of IS0 3443 enable selection of suitable target sizes .for components and construc- tion so that joints that are within their required clea
24、rance limits can be achieved. The procedures also enable selection of joint- ing techniques that have suitable clearance limits when some or all of the target sizes are predetermined (as when standard components are used). In either application the procedures enable prediction of the probability tha
25、t joints on site will be within their clearance limits. The procedures are designed to predict the chance of misfitting either the minimum or maximum joint clearance of which the chosen jointing technique is capable. 6.1 Assumptions 6.1.1 Deviations Dimensional variability data are for the general c
26、ase of each form of construction or component; that is, it is assumed that tolerances have not yet been applied and that deviations for both components and in situ work therefore follow normal distributions about a mean the value of which is influenced by systematic deviation. The values of mean and
27、 standard deviation which are required as a description of dimensional variability may be estimated from measurement surveys; alter- natively, standard deviation may be estimated from tolerance specifications combined with acceptance criteria, it being then assumed that systematic deviation is zero.
28、 6.1.2 Criteria for fit Two factors, acting in conjunction, determine whether or not fit will be achieved. These factors are as follows: a) the specified upper and lower limits of joint clearance; b) the capability of the selected jointing technique to func- tion satisfactorily within those limits.
29、In order to predict fit, this part of IS0 3443 requires that target sizes are to be derived from coordinating or modular sizes. The calculations make use of extension and deduction as a means of maintaining the relationship. 6.1.3 Assembly It is assumed that those components that are erected first f
30、orm spaces within which the remainder must fit with satisfactory joint clearances. It is recognized that not all building construc- tion follows this sequence in practice but the assumption nonetheless provides a valid basis for calculation purposes. When measurement surveys provide the accuracy dat
31、a for the sizes of such constructed spaces, these data will automatically include the contributions of setting out and erection to the total variability of constructed spaces. 1) In certain cases, in situ work may be considered as if it were a component. 2) i.e., embracing all constituent variables
32、such as bow, twist, etc. 3) Inherent deviations are dealt with in annex A. 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:09:32 MDTNo reproduction or networking permitted w
33、ithout license from IHS -,-,- IS0 3443-3 : 1987 (El It is also assumed that components which are to occupy con- structed spaces can be adjusted in position to achieve joint clearances within their working limits. Alternatively, where physical adjustment of components would not be practical they, and
34、 the constructed space they are to occupy, can be measured prior to their insertion in the space concerned in order to derive an approximate uniform joint clearance to be aimed for in that assembly. It will then be clear prior to assembly whether or not the joint clearance that will be achieved will
35、 lie within the required limits of joint clearance. As an alternative to the assumption that components can be adjusted (or measured to achieve the same end), a modification to deal with placing components in relation to a datum or grid is given in 7.6. If two or more components in an assembly are b
36、utt-jointed, the group may be treated as if it were one component with a Q,., value equal to the square root of the sum of the squares of ccornr, for each component. The variabilities in sizes of constructed spaces and of com- ponents are assumed to follow normal distributions even if there has been
37、 prior implementation of tolerances. Prior implementation of tolerances on constructed space sizes is not possible and their size distribution is thus undisturbed. Surveys demonstrate that constructed spaces are the predominant source of variability in assemblies. It is unlikely that prior implement
38、ation of tolerances on components would affect their size distribution noticeably, for reasons of manufacturing economics. However, the deviations of size within a batch of components may tend to be similar to each other, in which case the procedure in 7.6 should be used. The variability considered
39、along any one axis is the total effect of all its constituent variabilities (for example, bow, twist, sur- face irregularity, etc.). Commonly, the user will wish to examine one axis only but the procedures can be applied to each of the three dimensional axes in turn. 7 Proceduresf) 6.1.4 Common basi
40、s of application Provided the assumptions (in 6.1) apply, the procedures pro- vide a common basis for - selecting target sizes for standard components so that they can have the widest application, and for - selecting, from standard components, those that are suitable for a specific application. Thus
41、 the procedures enable target sizes to be derived from coordinating sizes or modular sizes so as to enable dimensional or modular coordination to be implemented at their practical level. The procedures can also be applied when designing a specific building using non-standard components but where gen
42、eral- ized accuracy data (for example, for “precast concrete units”, or for “timber windows? are available. In this case its basis matches the common design circumstance in which particular sources of components or construction are not yet identified. 6.2 Application limitations The objective is to
43、provide manufacturers, building designers and builders with working procedures for predicting the pro- bability that satisfactory fit can be achieved with the chosen sizes of components, construction and joints. The procedures are not based on a complete and mathematically exact ex- pression of the
44、relationships concerned and the mathematical basis Is further restricted to terms for which data are usually obtainable. 7.1 Selecting a component target size when all components, and all joints, are of the same type 7.1.1 Risk of misfit Decide on acceptable risks of misfit and read the values of Q
45、and q, from figure 2, corresponding to the risk of the joint clearance being too large and too small respectively. In choosing risks of misfit, the consequence of misfit must be considered. For example, if the cost of dealing with a misfit is too great the risk may have to be reduced. 7,1.2 Checking
46、 the jointlng technique Before calculating the minimum and maximum target sizes for components, ensure that the jointing technique can accom- modate the range of variation in actual size of components and spaces. Check that 7.1.3 Component size - lower target size limit Calculate the lower limit of
47、component target size ?imr, as follows: W min = Csp + E + rus, + Qd4omp + 4p n n (n + I) Jmax n - Pcomc 11 Worked examples of application are given in annex ES. 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/99725
48、45001 Not for Resale, 04/21/2007 09:09:32 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 3443-3 : 1957 (El 7.1.4 Component size - upper target size limit Calculate the upper limit of component target size TV, as follows: W csp + E + cc, qGg7-q max .= - n n in + 1) Jmin
49、 - n - Pcomp 7.1.5 Special case In some cases n, is so small compared with crb that the se- Qa cond expression in 7.1.3 becomes approximately equal to sp, n and the second expression in 7.1.4 becomes approximately QT,p n * If Gomp is not known but ncromp can safely be assumed to be small, the same approximation can be made. 7.1.6 Selecting the target size of the component from the range ca