1、NATIONAL ANNEXNA to BS EN 1991-1-3:2003UK National Annex to Eurocode 1: Actions on structures Part 1-3: General actions Snow loadsICS 91.010.30; 91.080.01g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55
2、g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58Licensed Copy: Wang Bin, na, Tue Mar 07 01:59:40 GMT 2006, Uncontrolled Copy, (c) BSINA to BS EN 1991-1-3:2003This National Annex was published under the authority of the Standards Policy and Strategy Committee on 23 December 2005 BSI 23 December
3、 2005First edition 23 December 2005The following BSI references relate to the work on this National Annex:Committee reference B/525/1Draft for comment 04/30116577ISBN 0 580 47334 1Committees responsible for this National AnnexThe preparation of this National Annex was entrusted by Technical Committe
4、e B/525, Building and civil engineering structures, to Subcommittee B/525/1, Actions (loadings) and basis of design, upon which the following bodies were represented:Association of Consulting EngineersBritish Constructional Steelwork AssociationBritish Masonry SocietyBuilding Research EstablishmentC
5、oncrete SocietyHealth and Safety ExecutiveHighways AgencyInstitution of Civil EngineersInstitution of Structural EngineersNational House Building CouncilOffice of the Deputy Prime MinisterSteel Construction InstituteAmendments issued since publicationAmd. No. Date CommentsLicensed Copy: Wang Bin, na
6、, Tue Mar 07 01:59:40 GMT 2006, Uncontrolled Copy, (c) BSINA to BS EN 1991-1-3:2003 BSI 23 December 2005iContentsPageCommittees responsible Inside front coverIntroduction 1NA.1 Scope 1NA.2 Nationally Determined Parameters 1NA.3 Decisions on the status of informative annexes 7NA.4 References to non-c
7、ontradictory complementary information 7Bibliography 8Figure NA.1 Characteristic ground snow load map 3Figure NA.2 Drifted snow load arrangement for a duo-pitched roof in the UK 4Figure NA.3 Drifted snow load arrangements for a cylindrical roof in the UK 6Table NA.1 Drifted snow load shape coefficie
8、nt for a duo-pitched roof in the UK 4Table NA.2 Drifted snow load shape coefficients for a cylindrical roof in the UK 5Licensed Copy: Wang Bin, na, Tue Mar 07 01:59:40 GMT 2006, Uncontrolled Copy, (c) BSIblank1 Licensed Copy: Wang Bin, na, Tue Mar 07 01:59:40 GMT 2006, Uncontrolled Copy, (c) BSINA t
9、o BS EN 1991-1-3:2003 BSI 23 December 20051National Annex (informative) to BS EN 1991-1-3:2003, Eurocode 1: Actions on structures Part 1-3: General actions Snow loadsIntroduction This National Annex has been prepared by BSI Subcommittee B/525/1, Actions (loadings) and basis of design. In the UK it i
10、s to be used in conjunction with BS EN 1991-1-3:2003.NA.1 ScopeThis National Annex gives:a) the UK decisions for the Nationally Determined Parameters described in the following subclauses of BS EN 1991-1-3:2003: 1.1 (2) 4.2 (1) 5.3.5 (1) 1.1 (3) 4.3 (1) 5.3.5 (3) 1.1 (4) 5.2 (2) 5.3.6 (1) 2 (3) 5.2
11、(5) 5.3.6 (3) 2 (4) 5.2 (6) 6.2 (2) 3.3 (1) 5.2 (7) 6.3 (1) 3.3 (3) 5.2 (8) 6.3 (2) 4.1 (1) 5.3.3 (4) Annex A (1) 4.1 (2) 5.3.4 (3)b) the UK decisions on the status of BS EN 1991-1-3:2003 informative annexes;c) references to non-contradictory complementary information.NA.2 Nationally Determined Para
12、metersNA.2.1 Altitudes greater than 1 500 m BS EN 1991-1-3:2003, 1.1 (2)The scope of BS EN 1991-1-3 does not include sites at altitudes above 1 500 m. For altitudes greater than 1 500 m specialist advice should be sought from the Meteorological Office on the snow loads likely to occur at the site.NA
13、.2.2 Design situations and load arrangements to be used for different locations BS EN 1991-1-3:2003, 1.1 (3)The scope of BS EN 1991-1-3 states that information on design situations and load arrangements to be used for different locations is given in BS EN 1991-1-3:2003, Annex A.The design situations
14、 summarized as case B2 in BS EN 1991-1-3:2003, Table A.1 should be the only exceptional condition to be checked for determining imposed roof snow loads in the UK.NA.2.3 Snow load shape coefficients for exceptional snow drifts BS EN 1991-1-3:2003, 1.1 (4)The scope of BS EN 1991-1-3 states that inform
15、ation on snow load shape coefficients for exceptional snow drifts is given in BS EN 1991-1-3:2003, Annex B.BS EN 1991-1-3:2003, Annex B should be used in the UK in order to determine exceptional snow drift loads.NA.2.4 Exceptional snow load on the ground BS EN 1991-1-3:2003, 2 (3)Exceptional snow lo
16、ad on the ground should be treated as accidental actions.NA.2.5 Load due to exceptional snow drift BS EN 1991-1-3:2003, 2 (4)Drift loads determined using the guidance given in BS EN 1991-1-3:2003, Annex B should be treated as accidental actions.NA.2.6 Locations with exceptional snow load on the grou
17、nd but with no load due to exceptional snow drift BS EN 1991-1-3:2003, 3.3 (1)Locations that experience these conditions are not considered to occur in the UK.Licensed Copy: Wang Bin, na, Tue Mar 07 01:59:40 GMT 2006, Uncontrolled Copy, (c) BSINA to BS EN 1991-1-3:20032 BSI 23 December 2005NA.2.7 Lo
18、cations with exceptional snow load on the ground and with load due to exceptional snow drift BS EN 1991-1-3:2003, 3.3 (3)BS EN 1991-1-3:2003, Annex B should be used in place of BS EN 1991-1-3:2003, 6.2 in order to determine the load case due to drifting in the UK.NA.2.8 Characteristic value of snow
19、load on the ground BS EN 1991-1-3:2003, 4.1 (1)The characteristic ground snow loads skto be used in the UK should be obtained from the map shown in Figure NA.1 and Equation (NA.1).sk015, 01Z,( 005,)A 100+525-+ += (NA.1)wheresk is the characteristic ground snow load (kN/m2);Z is the zone number obtai
20、ned from the map in Figure NA.1;A is the site altitude (m).Unusual local effects may not have been accounted for in the analysis undertaken to produce the ground snow load map given in Figure NA.1. These include local shelter from the wind, which can result in increased local snow loads and local co
21、nfigurations in mountainous areas, which may funnel the snow and give increased local loading. If the designer suspects that there are unusual local conditions that need to be taken into account, then for coastal sites below 100 m the map value should be used without the altitude modification. Alter
22、natively, and in other cases, the Meteorological Office should be consulted.NA.2.9 Refined characteristic value of snow load on the ground BS EN 1991-1-3:2003, 4.1 (2)Where a more refined characteristic ground snow load value skis required, the Meteorological Office should be consulted.NA.2.10 Other
23、 representative values for snow load on the ground BS EN 1991-1-3:2003, 4.2 (1)The UK National Annex to BS EN 1990 gives values that should be used in the UK for the coefficients 0, 1and 2.NA.2.11 Treatment of exceptional snow load on the ground BS EN 1991-1-3:2003, 4.3 (1)The coefficient for except
24、ional snow loads Ceslshould take a value of 2,0 as recommended in BS EN 1991-1-3.NA.2.12 Determining load arrangements for snow loads on roofs BS EN 1991-1-3:2003, 5.2 (2)BS EN 1991-1-3:2003, Annex B should be used to determine the imposed roof loads due to drifted snow for:a) multi-span roofs in pl
25、ace of BS EN 1991-1-3:2003, 5.3.4 (3);b) roofs abutting and close to taller structures in place of BS EN 1991-1-3:2003, 5.3.6 (3);c) drifting at projections and obstructions in place of BS EN 1991-1-3:2003, 6.2 (2).NA.2.13 Load arrangements for artificial removal or redistribution of snow on a roof
26、BS EN 1991-1-3:2003, 5.2 (5)In certain cases, snow may be artificially removed from or redistributed on a roof, e.g. due to excessive heat loss through a small section of roof or manually to maintain access to a service door. This can result in more severe load imbalances occurring than those result
27、ing from BS EN 1991-1-3:2003, 5.3 and Annex B (which have been derived for natural deposition patterns). To provide for these situations, if they are likely to occur and other information is not available, a load case should be considered comprising the minimum imposed uniformly distributed load (BS
28、 EN 1991-1-3:2003, 5.3) on any portion of the roof area and zero load on the remainder of the area.NA.2.14 Load arrangements for situations arising from rainfall on snow on roofs BS EN 1991-1-3:2003, 5.2 (6)The UK National Annex to BS EN 1991-1-1 specifies minimum imposed loads on roofs with access
29、for maintenance only. These values allows for a certain build-up of water but it does not allow for the effect of drains becoming blocked due to debris or ice. Specialist advice should be sought where the consecutive melting and freezing of snow together with possible rainfall is likely to occur and
30、 block roof drainage.Licensed Copy: Wang Bin, na, Tue Mar 07 01:59:40 GMT 2006, Uncontrolled Copy, (c) BSI01Jersey - Zone 3, 0,50 kN/m2at 100m a.m.s.l, Guernsey - Zone 2, 0,40 kN/M2at 100m a.m.s.l2340123455678910111271210 301234 5 67HT HUHYHT HZNDNCNBNANGNFNMNLNENJNH NKNONN NPNTNSNR NUNYNX NZSDSCIBI
31、FIGIMILINIOITISIRIQIV IWIXIHIJICSESJSH SKSOSNSM SPSTSSSRSUSYSXSWSZHTTA TFTLTQTVHTTMTRTWHP123456,50,250,400,500,600,700,85ZonenumbersGround snow load at100m a.m.s.l (kN/m2)Figure NA.1 Characteristic ground snow load mapNA to BS EN 1991-1-3:2003 BSI 23 December 20053Licensed Copy: Wang Bin, na, Tue Ma
32、r 07 01:59:40 GMT 2006, Uncontrolled Copy, (c) BSINA to BS EN 1991-1-3:20034 BSI 23 December 2005NA.2.15 Exposure coefficient used for determining snow load on a roof BS EN 1991-1-3:2003, 5.2 (7)The recommended value for exposure coefficient Cein the UK is 1,0 for all topographies.NA.2.16 Thermal co
33、efficient used to account for the reduction of snow load on roofs with high thermal transmittance BS EN 1991-1-3:2003, 5.2 (8)The recommended value for thermal coefficient Ctin the UK is 1,0 for all roofing materials.NA.2.17 Drifted snow load arrangement for pitched roofs BS EN 1991-1-3:2003, 5.3.3
34、(4)The load arrangement given in Figure NA.2 and Table NA.1 should be used in place of BS EN 1991-1-3:2003, 5.3.3 (4) to determine the drifted snow load on a duo-pitched roof in the UK.D1 D2P1,(D1)P1,(D2)Case (ii)Case (iii)ls1ls2b1b2lsi= biFigure NA.2 Drifted snow load arrangement for a duo-pitched
35、roof in the UKTable NA.1 Drifted snow load shape coefficient for a duo-pitched roof in the UKSnow load shape coefficentAngle of pitch of roof (i, i =1,2)0 k 1k 15 15 60 is the angle between the horizontal and a line drawn from the crown to the point of the roof where the tangent to the surface makes
36、 an angle of 60 with the horizontal.The load arrangements shown in Figure NA.3 need only be considered for roofs where is greater than 15. The value for the snow load shape coefficient for one side of the roof should be zero, while the values for the other side should be obtained from Figure NA.3 an
37、d Table NA.2. The values for the snow load shape coefficients are assumed to be constant in the direction parallel to the eaves.Table NA.2 Drifted snow load shape coefficients for a cylindrical roof in the UKSnow load shape coefficientEquivalent slope for curved roof 0 k k 15 15 k 30 30 60 U 6010 0,
38、4 0,4 020 0,8 + 0,4( 15)/15 1,2(60 )/30 030 2(60 )/30 2(60 )/30 0NA.2.21 Snow load shape coefficient for a roof abutting and close to taller construction works BS EN 1991-1-3:2003, 5.3.6 (1)BS EN 1991-1-3:2003, Annex B should be used to determine the drifted snow load case. This method does not incl
39、ude the snow load shape coefficient w, therefore, no range of values is specified for this coefficient for use in the UK.NA.2.22 Drifted snow load arrangement for a roof abutting and close to taller construction works BS EN 1991-1-3:2003, 5.3.6 (3)BS EN 1991-1-3:2003, Annex B should be used to deter
40、mine the drifted snow load case.NA.2.23 Drifting at projections and obstructions BS EN 1991-1-3:2003, 6.2 (2)BS EN 1991-1-3:2003, Annex B should be used to determine the drifted snow load case.NA.2.24 Altitude at which to consider the effects of snow overhanging the edge of a roof BS EN 1991-1-3:200
41、3, 6.3 (1)BS EN 1991-1-3:2003, 6.3 should be used for sites at altitudes greater than 800 m above sea level.NA.2.25 Calculating the loads caused by snow overhanging the edge of a roof BS EN 1991-1-3:2003, 6.3 (2)When calculating the load caused by snow overhanging the edge of a roof, the coefficient
42、 for the irregular shape of the snow k should be determined in accordance with the Note to BS EN 1991-1-3:2003, 6.3 (2).NA.2.26 Design situations and load arrangements to be used for different locations BS EN 1991-1-3:2003, Annex AThe localized drifts given in BS EN 1991-1-3:2003, Annex B have been
43、classified as exceptional drifts due to the maritime climate of the UK.Load case B2 described in BS EN 1991-1-3:2003, Annex A should be used in place of BS EN 1991-1-3:2003, 6.2 for local drifting at projections and obstructions.Licensed Copy: Wang Bin, na, Tue Mar 07 01:59:40 GMT 2006, Uncontrolled
44、 Copy, (c) BSIGDDbP1P1P2P1P2P2P3G 60b/2bbb/2GGDD_G 30G 60306030TangentTangentTangentTangentTangentTangentFigure NA.3 Drifted snow load arrangements for a cylindrical roof in the UKNA to BS EN 1991-1-3:20036 BSI 23 December 2005Licensed Copy: Wang Bin, na, Tue Mar 07 01:59:40 GMT 2006, Uncontrolled C
45、opy, (c) BSINA to BS EN 1991-1-3:2003 BSI 23 December 20057NA.3 Decisions on the status of informative annexesNA.3.1 European ground snow load maps BS EN 1991-1-3:2003, Annex CBS EN 1991-1-3:2003, Annex C should not be used to determine ground snow loads in the UK. The ground snow load map given in
46、Figure NA.1 should be used.NA.3.2 Adjustment of the ground snow load according to return period BS EN 1991-1-3:2003, Annex DBS EN 1991-1-3:2003, Annex D may only be used in the UK for determining annual probabilities of exceedance smaller than 0,2.NA.3.3 Bulk weight density of snow BS EN 1991-1-3:20
47、03, Annex EBS EN 1991-1-3:2003, Annex E may be used in the UK.NA.4 References to non-contradictory complementary informationNA.4.1 Specialist aspects of snow loading BS EN 1991-1-3:2003, 1.1 (8)NA.4.1.1 Snow loading on bridgesSnow loads should be considered in accordance with local conditions. For t
48、hose local conditions prevailing in the United Kingdom, this loading may generally be ignored. However, there are circumstances, e.g. for opening bridges, covered bridges including roofed footbridges, or where stability due to permanent loads is critical, when snow loading should be taken into accou
49、nt in the design. On ordinary bridges the accumulation of any material quantity of snow will effectively reduce the traffic loads, probably by amounts greater than the snow loads, but certainly to such an extent that the combined mass of snow and traffic loading will not exceed the nominal live load. On opening bridges, however, snow load can b
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