ISO INTERNATIONAL STANDARD 12494 Second edition 2017-03 Atmospheric icing of structures Charges sur les structures dues a la glace Reference number IS012494:2017(E) International Organization for Standardization @ IS0 2017 =ZHEJIANG INST OF STANDARDIZATION C1 5956617 vided by IHS under lic Not for Resale, 2017/5/16 00:42:59 itted without license from IHS IS0 12494:2017(E) COPYRIGHTPROTECTEDDOCUMENT IS0 2017, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form written permission. Permission can be requested from either ISO at the address below or ISO's member body in the country of the requester. ISOcopyrightoffice Ch. de Blandonnet 8 . CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org Internatinair PrganizationforStandardization nsee-ZHEJIANG INSTOFSTANDARDIzAoISQ07-All rights reserved Not for Resale, 2017/5/16 00:42:59 etworking permitted without license from IHS IS0 12494:2017(E) Contents Page Foreword ..V Introduction. ..vii 1 Scope. 2 Normative references 3 Terms and definitions 4 Symbols 5 Effects of icing. ..4 5.1 General .4 5.2 Static ice loads 5.3 Windaction on iced structures .4 5.4 Dynamic effects .. 5.5 Damage caused by falling ice. ..5 6 Fundamentals of atmospheric icing .5 6.1 .5 General 6.2 Icing types. .6 6.2.1 General. 6.2.2 Glaze ..8 6.2.3 Wetsnow. .8 6.2.4 Rime ..8 6.2.5 Other types of ice .9 6.3 Topographic influences. ..9 6.4 Variation with height above terrain. .10 7 Icing on structures .11 7.1 General. .11 7.2 Ice classes .11 7.3 Definition of ice class, IC ..12 7.4 Glaze ..12 7.4.1 General. .12 7.4.2 Glaze on lattice structures .12 7.5 Rime ..13 7.5.1 General .13 7.5.2 Rime on single members. .15 7.6 Rime on lattice structures. .18 7.6.1 General. .18 7.6.2 Direction of ice vanes on the structure. ..19 7.6.3 Icing on members inclined to the wind direction ..19 8 Wind actions on iced structures ..20 8.1 General 20 8.2 Single members. .20 8.2.1 General 20 8.2.2 Drag coefficients for glaze .21 8.2.3 Drag coefficients for rime. .23 8.3 Angle of incidence. 27 8.4 Lattice structures 27 Combination of ice loads and wind actions .28 9.1 General .28 9.2 Combined loads 28 10 Unbalanced ice load on guys .29 11 Falling ice considerations .30 iii nsee=ZHEJIANG INST OF STANDARDIZATION C1 5956617 d without license from IHS Not for Resale, 2017/5/16 00:42:59