Enquiry period: 13 th April 2010 to 11 th May 2010

Transcription

1 Draft for Public Comment Number dna:2010 to I.S. EN Title Irish National Annex to Eurocode 1 Actions on structures - Part 1-3: General actions Snow loads This National Annex National Amendment outlines the Irish National Determined Parameters for Eurocode EN Enquiry period: 13 th April 2010 to 11 th May 2010 Readers are warned that this draft is subject to ongoing development and change Please send your comments on the comments sheet available on to: Barry.smith@nsai.ie or NSAI 1 Swift Square, Northwood, Santry Dublin 9

2 Contents Page Annex NA (informative) Irish National Annex to Eurocode 1: Actions on structures Part 1-3: General actions Snow loads...2 Introduction...2 NA.1 Scope...2 NA.2 Nationally Determined Parameters...3 NA.2.1 Subclause 1.1(2) General, Scope...3 NA.2.2 Subclauses 1.1(3) General, Scope...3 NA.2.3 Subclause 1.1(4) General, Scope...3 NA.2.4 Subclause 2(3) Classification of actions...3 NA.2.5 Subclause 2(4) Classification of actions...3 NA.2.6 Subclause 3.3(1) Exceptional conditions...3 NA.2.7 Subclause 3.3(3) Exceptional conditions...3 NA.2.8 Subclause 4.1(1) Characteristic values...3 NA.2.9 Subclause 4.1(2) Characteristic values...3 NA.2.10 Subclause 4.2(1) Other representative values...3 NA.2.11 Subclause 4.3(1) Treatment of exceptional snow loads on the ground...3 NA.2.12 Subclause 5.2(2) Load arrangements...4 NA.2.13 Subclause 5.2(5) Load arrangements...4 NA.2.14 Subclause 5.2(6) Load arrangements...4 NA.2.15 Subclause 5.2(7) Load arrangements...4 NA.2.16 Subclause 5.2(8) Load arrangements...4 NA.2.17 Subclause 5.3.3(4) Pitched roofs...4 NA.2.18 Subclause 5.3.4(3) Multi-span roofs...4 NA.2.19 Subclause 5.3.4(4) Multi-span roofs...4 NA.2.20 Subclause 5.3.5(1) Cylindrical roofs...4 NA.2.21 Subclause 5.3.5(3) Cylindrical roofs...4 NA.2.22 Subclause 5.3.6(1) Roof abutting and close to taller construction works...4 NA.2.23 Subclause 5.3.6(3) Roof abutting and close to taller construction works...4 NA.2.24 Subclause 6.2(2) Drifting at projections and obstructions...4 NA.2.25 Subclause 6.3(1) Snow overhanging the edge of a roof...5 NA.2.26 Subclause 6.3(2) Snow overhanging the edge of a roof...5 NA.2.27 Annex A(1) Table A1 Design situations and load arrangements to be used for different locations...5 NA.3 Decisions on the use of Informative Annexes B, C, D & E...5 NA.3.1 Annex B Snow load shape coefficients for exceptional snow drifts...5 NA.3.2 Annex C European ground snow load maps...6 NA.3.3 Annex D Adjustment of the ground snow load according to return period...7 NA.3.4 Annex E Bulk weight density of snow...7 1

3 Annex NA (informative) Irish National Annex to Eurocode 1: Actions on structures Part 1-3: General actions Snow loads Introduction This Irish National Annex has been prepared by the NSAI National Eurocodes Advisory Committee. This National Annex is to be used together with I.S. EN :2003. I.S. EN is intended to be used in conjunction with I.S. EN 1990, the other parts of I.S. EN 1991 and I.S. EN 1992 to I.S. EN 1999 (together with their respective national annexes) for design of structures. The start and finish of text introduced or altered by this National Amendment No. 1 is indicated in the text by tags. NA.1Scope This National Annex gives: a) Irish decisions for the Nationally Determined Parameters (NDP's) described in the following subclauses of I.S. EN (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(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) (A1) (Table A1) 4.1(2) 5.3.4(3) b) Irish decisions on the application of informative annexes C, D and E for buildings and civil engineering works. 2

4 NA.2 Nationally Determined Parameters NA.2.1 Subclause 1.1(2) General, Scope I.S. EN applies to all parts of the Republic of Ireland as no altitudes exceed 1500 metres. NA.2.2 Subclauses 1.1(3) General, Scope The situations outlined in case B2 of Table A.1 are the only exceptional conditions to be checked in the Republic of Ireland in determining roof snow loads i.e. No exceptional falls / Exceptional drift. NA.2.3 Subclause 1.1(4) General, Scope Annex B should be used in the Republic of Ireland to determine exceptional snow drift loads. NA.2.4 Subclause 2(3) Classification of actions Exceptional snow loads on the ground are not deemed to occur in the Republic of Ireland. NA.2.5 Subclause 2(4) Classification of actions Exceptional snow drifts may be deemed to occur in accordance with Annex B and should be treated as accidental actions throughout the Republic of Ireland. NA.2.6 Subclause 3.3(1) Exceptional conditions Exceptional snow falls are not deemed to occur within the Republic of Ireland. NA.2.7 Subclause 3.3(3) Exceptional conditions Exceptional snow falls are not deemed to occur within Republic of Ireland. NA.2.8 Subclause 4.1(1) Characteristic values Annex C should not be used. Refer to NA.3.2 and Figure 1. The minimum value to be used for S K is 0,4 kn/m 2. Generally an altitude factor based on a minimum site height of 100 m (ordnance datum) should be used. NA.2.9 Subclause 4.1(2) Characteristic values The designer may seek further information from sources such as Met Éireann, the Irish Meteorological Service, if more detailed information is required. NA.2.10 Subclause 4.2(1) Other representative values The values of ψ to be used are as Table 4.1 of. I.S. EN NA.2.11 Subclause 4.3(1) Treatment of exceptional snow loads on the ground Exceptional snow loads on the ground are not deemed to occur in the Republic of Ireland. 3

5 NA.2.12 Subclause 5.2(2) Load arrangements Annex B should be used in accordance with subclause 3.3 and subclauses NA 2.3, NA 2.5, NA 2.7. NA.2.13 Subclause 5.2(5) Load arrangements Where anticipated (e.g. adjacent to service door or un-insulated roof sections) the designer should allow for a suitable load arrangement with zero snow load on those areas. NA.2.14 Subclause 5.2(6) Load arrangements Refreezing is not deemed a normal event in the Republic of Ireland. NA.2.15 Subclause 5.2(7) Load arrangements The recommended values in Table 5.1 should be used. NA.2.16 Subclause 5.2(8) Load arrangements The thermal coefficient should be used as specified in subclause 5.2(8). NA.2.17 Subclause 5.3.3(4) Pitched roofs The drift load arrangements specified in this clause should be used. NA.2.18 Subclause 5.3.4(3) Multi-span roofs NA.2.19 Subclause 5.3.4(4) Multi-span roofs NA.2.20 Subclause 5.3.5(1) Cylindrical roofs The recommended upper value for μ 3 of 2,0 should be used. NA.2.21 Subclause 5.3.5(3) Cylindrical roofs The drifted load arrangement specified in Figure 5.6 should be used. NA.2.22 Subclause 5.3.6(1) Roof abutting and close to taller construction works Annex B should be used to determine the due to drifting load case. NA.2.23 Subclause 5.3.6(3) Roof abutting and close to taller construction works NA.2.24 Subclause 6.2(2) Drifting at projections and obstructions 4

6 NA.2.25 Subclause 6.3(1) Snow overhanging the edge of a roof This subclause should be considered as recommended in I.S. EN NA.2.26 Subclause 6.3(2) Snow overhanging the edge of a roof The recommended values should be used. NA.2.27 Annex A(1) Table A1 Design situations and load arrangements to be used for different locations NOTE of Ireland. The localised drifts should be designed as exceptional conditions due to the maritime climate in the Republic NOTE For case B2 situation (3), drifted μ i S K should be used for roof shapes in Annex B. The other cases i.e. case B1 and case B3 are deemed not to occur in the Republic of Ireland. NA.3Decisions on the use of Informative Annexes B, C, D & E NA.3.1 Annex B Snow load shape coefficients for exceptional snow drifts 5

7 NA.3.2Annex C European ground snow load maps Informative Annex C should not be used. The values given in Figure 1 below should be used. The minimum value to be used for S K is 0,4 kn/m 2. Generally an altitude factor based on a minimum site height of 100 m (ordnance datum) should be used.. NOTE 1 The values shown on the map above should be used for all site altitudes 100 m O.D. NOTE 2 For sites with an altitude (A) above 100 m O.D., a correction figure of (A-100) / 500 kn/m 2 should be added to the values shown on the map. Figure 1 Irish Snow loads map 6

8 NA.3.3 Annex D Adjustment of the ground snow load according to return period Informative Annex D may be used. NA.3.4 Annex E Bulk weight density of snow Informative Annex E may be used. 7