BS PD 6687-2006 Background paper to the UK National Annexes to BS EN 1992-1《BS EN 1992-1标准的英国国家附录的背景文件》.pdf

1、PD 6687:2006Background paper to the UK National Annexes to BS EN 1992-1ICS 91.010.30; 91.080.40NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWPUBLISHED DOCUMENTLicensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSIPublishing and copyright informa

2、tionThe BSI copyright notice displayed in this document indicates when the document was last issued. BSI 2006ISBN 0 580 47942 0The following BSI references relate to the work on this standard:Committee reference B/525/2Publication historyFirst published March 2006Amendments issued since publicationA

3、md. no. Date Text affectedPD 6687:2006Licensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSI BSI 2006 iPD 6687:2006ContentsForeword ii1 Scope 12 BS EN 1992-1-1, Eurocode 2: Design of concrete structures Part 1-1: General rules and rules for buildings 13 BS EN 1992-1-2,

4、 Eurocode 2: Design of concrete structures Part 1-2: General rules Structural fire design 20AnnexesAnnex A (informative) Standards to be used in conjunction with BS EN 1992 21Annex B (informative) Detailing rules for particular situations 22Bibliography 27List of figuresFigure 1 Distribution of yiel

5、d strengths of reinforcement 3Figure 2 Stress-strain relationship for axial compression for different durations of loading 4Figure 3 Average stress in compression zone and location of the centroid of the compressive force 5Figure 4 Comparison of experimental and calculated ultimate moments for over-

6、reinforced beams 6Figure 5 Comparison of experimental and calculated strengths of axially loaded columns Parabolic rectangular diagram for a maximum stress of 0,85fcand a maximum strain of 0,002 7Figure B.1 Frame corner with closing moment Model and reinforcement 23Figure B.2 Frame corner with moder

7、ate opening moment (Asfyd/Acfck) 0,25 24Figure B.3 Frame corner with large opening moment (Asfyd/Acfck) 0,25 24Figure B.4 Corbel strut-and-tie model 25Figure B.5 Corbel detailing 26List of tablesTable 1 Values of restraint factor R for a particular pour configuration 16Summary of pagesThis document

8、comprises a front cover, an inside front cover, pages i and ii, pages 1 to 29 and a back cover.Licensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSIPD 6687:2006ii BSI 2006ForewordPublishing informationThis Published Document was published by BSI and came into effect o

9、n 31 March 2006. It was prepared by Subcommittee B/525/2, Structural use of concrete, under the authority of Technical Committee B/525, Building and civil engineering. A list of organizations represented on this committee can be obtained on request to its secretary.NOTE BS EN 1992-1-1 contains gener

10、al rules applicable to the design of all concrete structures. Therefore, B/525/10, which is responsible for Eurocodes for the design of bridges, was consulted in the drafting of this Published Document.Relationship with other publicationsThis Published Document is a background paper that gives non-c

11、ontradictory complimentary information for use in the UK with the Eurocode for concrete, BS EN 1992-1 and its UK National Annexes.Presentational conventionsThe provisions in this standard are presented in roman (i.e. upright) type. Its recommendations are expressed in sentences in which the principa

12、l auxiliary verb is “should”.Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.The word “should” is used to express recommendations of this standard. The word “may” is used in the text to express permissibility,

13、e.g. as an alternative to the primary recommendation of the clause. The word “can” is used to express possibility, e.g. a consequence of an action or an event.Notes and commentaries are provided throughout the text of this standard. Notes give references and additional information that are important

14、 but do not form part of the recommendations. Commentaries give background information.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.This Published Document is not to be r

15、egarded as a British StandardLicensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSI BSI 2006 1PD 6687:2006IntroductionWhen there is a need for guidance on a subject that is not covered by the Eurocode, a country can choose to publish documents that contain non-contradi

16、ctory complementary information that supports the Eurocode. This Published Document provides just such information and has been cited as a reference in the UK National Annexes to BS EN 1992-1.1 ScopeNOTE During the early stages of implementation of BS EN 1992, all the related European standards and

17、their UK National Annexes might not be available in their final form. Therefore, guidance on the standards that can be used in conjunction with BS EN 1992-1 during the early stages of its implementation is given in Annex A.This Published Document is a background paper that gives non-contradictory co

18、mplementary information for use in the UK with BS EN 1992-1-1 and BS EN 1992-1-2 and their UK National Annexes. This Published Document gives:a) background to the decisions made in the National Annexes for some of the Nationally Determined Paramaters;b) commentary on some specific subclauses from BS

19、 EN 1992-1-1 and BS EN 1992-1-2; andc) reference to the requirements of the UK Building Regulations2000 1 that are not covered in BS EN 1992-1 and its UK National Annexes.2 BS EN 1992-1-1, Eurocode 2: Design of concrete structures Part 1-1: General rules and rules for buildings2.1 Partial factors fo

20、r materials BS EN 1992-1-1:2004, 2.4.2.4The values recommended in BS EN 1992-1-1:2004, 2.4.2.4 have been adopted in the NA to BS EN 1992-1-1. BS EN 1992-1-1 gives a value of 1,15 for the partial factor for reinforcement s, which is also included in the current British Standard for structural use of

21、concrete, BS 8110-1:1997. This value represents a departure from the value of 1,05 that was used in the now withdrawn BS 8110-1:19851). The reason for the change revolves around the characteristic strength, to which the partial factor is applied.For a normal distribution of yield strengths, the char

22、acteristic strength fykis defined as:fyk= fym kywherefymis the mean value of the strength;yis the standard deviation of the yield strength; andk is a factor related to the percentage of test results that are likely to fall below fyk.1)BS 8110-1:1985 has been withdrawn and superseded by BS 8110-1:199

23、7.Licensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSIPD 6687:20062 BSI 2006Traditionally, and in product standards, fykhas been defined as the value below which 5% of the test results are expected to fall. For this percentile the value of k will be 1,64. The statist

24、ics from reinforcement production, however, show that the percentage of test results that are likely to fall below a strength of 460 N/mm2the characteristic value specified in the now withdrawn British Standard for reinforcement BS 4449:19972) is much less than 5% and the value of k is commonly near

25、er 2,5 (see Figure 1). Therefore the mean value of grade 460 reinforcement is approximately (460 + 2,5y).The characteristic value corresponding to the classical 5% value, which is used in the European reinforcement standard BS EN 10080:2005, is much nearer 500 N/mm2. The current British Standard for

26、 reinforcement, BS 4449:2005, which operates in conjunction with BS EN 10080:2005, now also specifies a characteristic strength of 500 N/mm2. Until statistical data for production specified as having this higher characteristic value becomes available, the partial factor of 1,15 should be applied. Th

27、erefore there is very little material change to the design values because 500/1,15 is almost the same as 460/1,05. In summary, there is no change in the material property or in the level of safety. The higher value of the partial factor merely represents the value appropriate to the characteristic v

28、alue of the yield strength, which conforms to the definition in BS EN 10080.NOTE One of the reasons for the high level of safety in the design stress for reinforcement was the difference in the relationship between the characteristic strength of reinforcement relative to the actual distribution of y

29、ield strengths compared with that specified in reinforcement standards such as BS 4449. This needs to be reanalysed when there is more experience of production to new standards. A brief summary of the procedure adopted for fixing the partial factor sis as follows.a) The value of 1,05 specified in BS

30、 8110-1:1985 arose from an extensive study carried out for the Department of the Environment in the early 1990s. The mean value and the coefficient of variation for resistance were calculated for some 3 000 reinforcement bar sections using data from surveys of variations in section dimensions, varia

31、tions in material properties and the model uncertainty in prediction equations.b) The global target reliability index of 3,8 was split into component parts for load effects E and resistances R as recommended in BS EN 1990. This gives 3,04 as the appropriate target reliability index for the resistanc

32、e side of the safety equation R. It was found that a value of 1,15 for sgave a value in excess of 4 for R rather than the generally accepted value of 3,04. It was therefore decided that a reasonable value for swas 1,05, which corresponded to a value of 3,8 for R, still in excess of the target value

33、of 3,04.2)BS 4499:1997 has been withdrawn and superseded by BS 4499:2005.Licensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSI BSI 2006 3PD 6687:2006Figure 1 Distribution of yield strengths of reinforcement3)3)2.2 Elastic deformation properties of concrete BS EN 1992-

34、1-1:2004, 3.1.3BS EN 1992-1 recognizes that elastic deformations of concrete largely depend on its composition (particularly aggregates). Therefore the values given in BS EN 1992-1 for creep, shrinkage and elastic modulus should be treated as indicative. These should prove satisfactory for the major

35、ity of normal structures. However, it is intended that testing should be undertaken to ascertain the properties of concrete composition used in structures that are likely to be sensitive to deformations and this should be properly specified in the contract documents for a project. The inherent varia

36、bility of properties should be taken into account using statistical procedures.2.3 Value of ccBS EN 1992-1-1:2004, 3.1.6 (1)PDesign compressive strength fcdis defined in BS EN 1992-1-1:2004, 3.1.6 (1)P as:fcd= ccfck/cwherefckis the characteristic strength of concrete;cis the partial factor; and ccis

37、 a coefficient;which according to BS EN 1992-1-1 takes into account the long-term effects on the compressive strength and unfavourable effects resulting from the way the load is applied. 3)Data supplied by reinforcement manufacturers.1 8001 6001 4001 2001 0008006004002000450 470 490 510 530 550 5705

38、90 610 630 650Yield strength ( N/mm )2Number of test resultsLicensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSIPD 6687:20064 BSI 2006BS EN 1992-1-1 recommends a value of 1,00 for ccbut the NA to BS EN 1992-1-1 recommends changing this to 0,85, which was the value us

39、ed in DD ENV 1992-1-1.During the development of BS EN 1992-1-1 the following three reasons were given for recommending a value of 1,00 for cc.a) Based on tests by Rsch (1960s) 2 it is stated that the stress at failure under constant load depends on the duration of loading. This approaches 80% of the

40、 short-term capacity as the duration of loading increases and is higher for shorter duration (see Figure 2).b) The strength at 28 days forms the basis for design calculations. However, in practice when structures receive their design loads they will be older than 28 days and there is an increase in

41、strength of the order of 12% for concrete with normal hardening cement. Therefore a considerable part of the sustained loading effect has already been compensated.c) The resistance equations in design codes such as BS EN 1992-1-1 are derived from laboratory tests with a duration of about 90 min, whe

42、n the strength of concrete would have already fallen by about 15% compared to the short-term value. Therefore part of the effects for sustained loading has been already built in the resistance equations.Figure 2 Stress-strain relationship for axial compression for different durations of loading4)4)4

43、)Image originally sourced from Rsch 2.1,00,80,60,40,200123 456783days70daysc%100min20mint= 2mininstantaneous strainfailure under constant loadt=max. strain/ fcLicensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSI BSI 2006 5PD 6687:2006While the UK does not totally rej

44、ect the arguments given in a), b) and c), it considers that the comparison of the predicted and experimental compression zone behaviour has been ignored. shows the results obtained by Imperial College and the Prestressed Concrete Association for the average stress in compression zone as a fraction o

45、f the cube strength of concrete 3. At higher levels of strength, DD ENV 1992-1-1 (which recommended 0,85 for cc) and BS 8110 give something approaching a median prediction and BS EN 1992-1-1 (which recommends 1,0 for cc) is close to the upper characteristic value. Figure 3 Average stress in compress

46、ion zone and location of the centroid of the compressive force5)5)5)Image taken from The design of sections for flexure and axial load according to CP110 by A.W. Beeby 4, obtained from tests carried out at PCA and Imperial College 3.1,00,80,60,4010203040 50 60 70800,90,70,5ENENVAverage stress cube s

47、trengthCube strength ( N/mm )2Upper characteristicLower characteristicBS 81100,50,30,1010203040 50 60 70800,60,40,20Cube strength ( N/mm )2BS 8110EN and ENVLicensed Copy: Wang Bin, na, Thu May 18 01:54:59 BST 2006, Uncontrolled Copy, (c) BSIPD 6687:20066 BSI 2006Figure 4 and Figure 5 reproduce the c

48、omparisons of test and calculated values from the International Federation for Structural Concrete (fib)bulletin, Structural Concrete Text book on behaviour, design and performance 5. The figures are calibrations for the proposals in the CEB/FIP Model Code 90 6. A value of 0,85 for ccis built into t

49、he model code equations. While these figures show that the model code is conservative for low strengths of concrete, the model code provisions give something close to a “best fit” to the experimental results for higher strengths of concrete. If the factor of 0,85 were removed from the provisions the calculations would predict something close to an upper bound to the data. It seems that ccis a necessary calibration factor to permit the BS EN 199