1、BSI Standards Publication PD 6688-1-4:2015 PUBLISHED DOCUMENT Background information to the National Annex to BS EN 199114 and additional guidance PD 668814:2009 This publication is not to be regarded as aB ritish Standard. PD 6688-1-4:2015 PUBLISHED DOCUMENT Publishing and copyright information The
2、 BSI copyright notice displayed in this document indicates when the document was last issued. The British Standards Institution 2015 Published by BSI Standards Limited 2015 ISBN 978 0 580 91197 2 ICS 91.010.30 The following BSI reference relates to the work on this standard: Committee reference B/52
3、5/1 Draft for comment 15/30331817 DC Publication history First published November 2009 Second (present) edition, December 2015 Amendments issued since publication Date Text affected The British Standards Institution 2015 i PD 6688-1-4:2015 PUBLISHED DOCUMENTContents Foreword iii Introduction 1 1 Sco
4、pe 1 2 UK National Annex to BS EN 1991-1-4:2005 1 3 Data that can be used in conjunction with BS EN 1991-1-4:2005 11 Annexes Annex A (informative) Vortex shedding and aeroelastic instabilities 21 Annex B (informative) Along-wind response of lattice towers 52 Bibliography 90 List of figures Figure 1
5、An example of altitude correction factors 2 Figure 2 Hill parameters in undulating terrain 4 Figure 3 Typical examples of buildings with re-entrant corners and recessed bays 12 Figure 4 Examples of flush irregular walls 13 Figure 5 Keys for walls of inset storey 14 Figure 6 Key for inset storey 15 F
6、igure 7 Key to canopies attached to buildings 15 Figure 8 Wind directions for a rectangular plan building 17 Figure 9 Key for vertical walls of buildings 19 Figure 10 Definitions of crosswind breadth and in wind depth 19 Figure A.1 Strouhal number St for rectangular cross-sections with sharp corners
7、 25 Figure A.2 Strouhal number St for bridge decks 25 Figure A.3 Bridge types and reference dimensions 27 Figure A.4 Bridge deck details 28 Figure A.5 Basic value of the lateral force coefficient c lat,0versus Reynolds number Re(v crit,i ) 32 Figure A.6 Examples for application of the correlation le
8、ngth L j( j = 1, 2, 3) 33 Figure A.7 In-line and grouped arrangements of cylinders 37 Figure A.8 Geometric parameters for interference galloping 48 Figure A.9 Rate of change of aerodynamic moment coefficient dc M /d with respect to geometric centre “GC” for rectangular section 49 Figure B.1 Gust pea
9、k factor (Davenports g) 54 Figure B.2 Definition of fetch for two roughness changes 56 Figure B.3 Fictitious square lattice tower with 12 panels 60 Figure B.4 Illustration of parameters for shear patch loading 77 List of tables Table 1 Global vertical force coefficients for canopies attached to tall
10、 buildings 15 Table 2 Internal pressure coefficients c pifor open-sided buildings 16 Table 3 Internal pressure coefficients c pifor open-topped vertical cylinders 16 Table 4 External pressure coefficients C pefor vertical walls of rectangular-plan buildings 19 Table 5 Reduction factors for zone A on
11、 vertical walls of polygonal-plan buildings 20 Table A.1 Strouhal numbers St for different cross-sections 24 Table A.2 Basic value of the lateral force coefficient c lat,0for different cross-sections 31 Table A.3 Lateral force coefficient c latversus critical wind velocity ratio v crit,i /v m,Lj 32i
12、i The British Standards Institution 2015 PD 6688-1-4:2015 PUBLISHED DOCUMENT Table A.4 Effective correlation length L jas a function of vibration amplitude y F (s j ) 34 Table A.5 Correlation length factor K Wand mode shape factor K for some simple structures 35 Table A.6 Constants for determination
13、 of the effect of vortex shedding 39 Table A.7 Assessment of vortex excitation effects 42 Table A.8 Factor of galloping instability a G 44 Table A.9 Data for the estimation of crosswind response of coupled cylinders at in-line and grouped arrangements 45 Table B.1 Length scale z L ufor a single roug
14、hness change from sea to country terrain, for an upwind fetch from site to sea of x(km) 54 Table B.2 Length scale for z L ufor two roughness changes where x1 = 0,1 km for an upwind fetch of x km 56 Table B.3 Length scale for z L ufor two roughness changes where x1 = 0,3 km for an upwind fetch of x k
15、m 57 Table B.4 Length scale for z L ufor two roughness changes where x1 = 1 km for an upwind fetch of x km 57 Table B.5 Length scale for z L ufor two roughness changes where x1 = 3 km for an upwind fetch of x km 58 Table B.6 Length scale for z L ufor two roughness changes where x1 = 10 km for an upw
16、ind fetch of x km 58 Table B.7 Length scale for z L ufor two roughness changes where x1 = 30 km for an upwind fetch of x km 59 Table B.8 Meteorological parameters 61 Table B.9 Non-dimensional coefficients, wind forces and wind moments 62 Table B.10 Values of c(z) c(z) 63 Table B.11 Values of C(z-z)
17、64 Table B.12 Values of c(z) c(z) C(z-z) 64 Table B.13 Non-dimensional coefficients and wind forces 66 Table B.14 Values of c(z) c(z) 67 Table B.15 Values of c(z) c(z) C(z-z) 67 Table B.16 Non-dimensional coefficients, wind forces and moments 68 Table B.17 Values of c(z) c(z) 70 Table B.18 Values of
18、 C(z-z) 71 Table B.19 Values of c(z) c(z) C(z-z) 71 Table B.20 Non-dimensional coefficients and wind forces 73 Table B.21 Values of c(z) c(z) 74 Table B.22 Values of c(z) c(z) C(z-z) 74 Table B.23 Non-dimensional coefficients and wind forces 76 Table B.24 Lever arms, wind loads and moments above z i
19、p 78 Table B.25 Lever arms, wind loads and moments below z ip 78 Table B.26 Values of c(z) c(z) 80 Table B.27 Valuesof C(z-z) 81 Table B.28 Values of c(z) c(z) C(z-z) 81 Table B.29 Meteorological parameters 83 Table B.30 Non-dimensional coefficients, wind forces and wind moments 83 Table B.31 Values
20、 of c(z) c(z) 85 Table B.32 Values of C(z-z) 86 Table B.33 Values of c(z) c(z) C(z-z) 86 Table B.34 Large ancillary wind resistance 88 Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 92, an inside back cover and a back cover. The British Stand
21、ards Institution 2015 iii PD 6688-1-4:2015 PUBLISHED DOCUMENTForeword Publishing information This Published Document is published by BSI and came into effect on 31 December 2015. It has been prepared by Working Group 2 of BSI Subcommittee B/525/1, Actions (loading) and basis of design, under the aut
22、hority of Technical Committee B/525, Building and civil engineering structures. A list of organizations represented on this committee can be obtained on request to its secretary. Supersession This Published Document supersedes PD 6688-1-4:2009, which is withdrawn. Information about this document The
23、 new edition of this Published Document introduces the following principal changes: a) Annex B inserted; and b) further reading updated. Relationship with other publications This Published Document gives non-contradictory complimentary information for use in the UK with BS EN 1991-1-4:2005 and its U
24、K National Annex. NOTE BS EN 1991-1-4 contains guidance applicable to all structures. Therefore, B/525/10, which is responsible for Eurocodes for the design of bridges, was consulted in the drafting of this Published Document. Use of this document This publication is not to be regarded as a British
25、Standard. As a guide, this Published Document takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading. Any user claiming compliance with this Published Document is
26、 expected to be able to justify any course of action that deviates from its recommendations. Presentational conventions The provisions in this Published Document are presented in roman (i.e. upright) type. Its recommendations are expressed in sentences in which the principal auxiliary verb is “shoul
27、d”. 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 Published Document. The word “may” is used in the text to express permissibility, e.g. as an alt
28、ernative 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.iv The British Standards Institution 2015 PD 6688-1-4:2015 PUBLISHED DOCUMENT Notes and commentaries are provided throughout the text of this Published Doc
29、ument. Notes give references and additional information that are important but do not form part of the recommendations. Commentaries give background information. This Published Document uses the decimal comma. Contractual and legal considerations This publication does not purport to include all nece
30、ssary provisions of a contract. Users are responsible for its correct application. This Published Document is not to be regarded as a British Standard The British Standards Institution 2015 1 PD 6688-1-4:2015 PUBLISHED DOCUMENTIntroduction When there is a need for guidance on a subject that is not c
31、overed by the Eurocode, a country can choose to publish documents that contain non-contradictory complimentary information that supports the Eurocode. This Published Document provides just such information and has been cited as a reference in the National Annex to BS EN 1991-1-4:2005.1 Scope This Pu
32、blished Document is a background paper that gives non-contradictory complementary information for use in the UK with BS EN 1991-1-4:2005 and its UK National Annex. This Published Document gives: a) background to the decisions made in the National Annexes for some of the Nationally Determined Paramet
33、ers; b) commentary on some specific subclauses from BS EN 1991-1-4:2005; and c) additional data that can be used in conjunction with BS EN 1991-1-4:2005.2 UK National Annex to BS EN 1991-1-4:20052.1 The fundamental value of the basic wind velocity v b,0 NA to BS EN 1991-1-4:2005, NA.2.4 The fundamen
34、tal value of basic wind velocity v b,0is defined as the 10-minute mean wind velocity with a 0,02 annual risk of being exceeded, irrespective of direction and season, at 10 m above ground level in terrain Category II, which is defined as open country with low vegetation and isolated obstacles with se
35、parations of at least 20 obstacle heights. While the 10-minute averaging period is the meteorological standard for much of continental Europe, some individual countries use 1 hour, including the UK and Germany. Both these countries have adopted a factor of 1,06 to adjust the measured 1-hour average
36、data to the 10-min period, based on empirical calibrations. In the UK the basic wind velocity is obtained from: v b, 0 = v b,map c alt “Map” values, v b,mapmay be found in the UK wind map, which gives values that have been adjusted to sea level and to Category II roughness everywhere. The UK map is
37、similar to the map in BS 6399-2:1997, except that the source data record has been increased from 11 years to 30 years and the original hourly-mean values have been factored up by 1,06 to represent 10-minute mean values. Thus the map in the National Annex is statistically more accurate. Altitude fact
38、or c altand corrections to account for changes of surface roughness are both National Choices. The former reduces the need to assess the effects of hills (orography) in many cases, while the latter allows conservatism to be reduced for sites further downwind of a coast or town boundary. 2 The Britis
39、h Standards Institution 2015 PD 6688-1-4:2015 PUBLISHED DOCUMENT2.2 Procedure for determining the influence of altitude NA to BS EN 1991-1-4:2005, NA.2.5 In the current UK practice, the altitude factor is taken as constant with height above ground and its value depends only on the altitude of the si
40、te. The factor was calibrated empirically against measured data over sites of varying altitude (although generally limited to altitude values below about 200 m). Whilst the simple constant conservative value would be appropriate for structures that are less than 50 m in height and built on sites les
41、s than 100 m altitude, it becomes conservative for, say, a 300 m high guyed mast built on a 250 m high hill. Computational Wind Engineering analyses of several high altitude sites, calibrated against known terrain characteristics, confirm this to be the case. Clearly at large heights the altitude ef
42、fect decreases so that, eventually, at the gradient wind speed height, the factor reduces to zero. Accordingly, two formulae have been introduced in NA to BS EN 1991-1-4:2005. For the majority of building structures, the simple formula, NA to BS EN 1991-1-4:2005, Equation NA.2a) may be used, without
43、 undue conservatism. Figure 1 illustrates the comparison of the two formulae in the NA to BS EN 1991-1-4:2005 for heights up to 300 m above ground level for a site at 250 m above mean sea level. Altitude factor is a simplified substitute for the full orography assessment. The correction that varies
44、with height formula NA.2b) removes a small double counting in BS 6399-2:1997; but makes the orography assessment more critical. Figure 1 An example of altitude correction factors 0 250 200 150 100 50 300 1,00 1,10 1,20 1,30 NA 2a NA 2b Height AGL (m) Altitude Factor, c alt The British Standards Inst
45、itution 2015 3 PD 6688-1-4:2015 PUBLISHED DOCUMENT2.3 Procedure for determining the roughness factor c r (z) NA to BS EN 1991-1-4:2005, NA.2.11 The roughness factor c r (z) accounts for the effect of the rough ground surface on the vertical profile of wind velocity. An approximate logarithmic profil
46、e is used in BS EN 1991-1-4:2005, which states that the expression given is valid when the upstream distance with uniform terrain roughness is sufficient to stabilize the profile sufficiently. It has been established that a “fetch” of over 100 km is required to achieve complete equilibrium. The coas
47、tline in the UK is such that equilibrium conditions do not generally occur in the UK. Therefore NA to BS EN 1991-1-4:2005 provides an alternative procedure to that indicated in BS EN 1991-1-4:2005. It defines the upstream distance as 100 km and provides a method that accounts for all intermediate va
48、lues. The values of the roughness factor c r (z) are presented graphically for ease of use (NA to BS EN 1991-1-4:2005, Figure NA.3 and Figure NA.4). It is recommended that all inland lakes extending more than 1 km in the direction of wind and closer than 1 km upwind of the site should be treated as
49、“Sea” for the purposes of terrain classification.2.4 Procedure for determining the orography factor c 0NA to BS EN 1991-1-4:2005, NA.2.132.4.1 General NA to BS EN 1991-1-4:2005, NA 2.9 specifies that the recommended procedure given in BS EN 1991-1-4:2005, A.3 should be used to determine the orography factor c 0 (z). This procedure provides formulae (and graphs) to determine c 0 (z) for cle
