ISO 12494:2017 pdf free

ISO 12494:2017 pdf free.Atmospheric icing of structures
Different types of structure are more or less sensitive to varying aspects concerning ice action, and some examples on this are as follows.
a) Tensioned steel ropes, cables and guys, etc., are generally very sensitive to ice action, consequently tension forces in such elements can increase considerably in an iced condition.
b) Slender lattice structures, especially guyed masts, are sensitive to the increased axial compression forces from accreted ice on the structure.
c) Antennas and antenna structures can easily be overloaded by accreted ice, if this has not been foreseen. In particular, small fastening details are weak when increased load is added on top of other actions, because the ice may easily double the normal load.
d) “Sagging of ice” on non-structural elements can be harmful. Non-structural elements such as antennas and cables, may be exposed to unexpected ice load because the ice sags downwards and covers or presses on the elements. The ice action on these elements can then be substantially greater than the ice load normally accreted on them.
e) The load of accreted ice can easily deform or damage envelope elements (claddings, etc.), and damage also might occur if the ice has not fallen off before forces have grown too great.
Structures such as masts and towers, together with tensioned steel ropes, cables, mast guys, etc., are sensitive to increased wind drag caused by icing.
Wind action on iced structures may be calculated based on the same principles as the action on the ice-free structure. However, both the dimensions of the structural members and their drag coefficients are subject to changes. Therefore, the main purpose of this document is to specify proper values for
一dimensions and weight of accreted ice,
一shapes of accreted ice, and
一drag coefficients of accreted ice.
A significant factor influencing the dynamic behaviour of a structure is its natural frequencies.
Normally, the natural frequencies of a structure are decreased considerably if the structure is heavily iced. This is important in connection with dynamic investigations because the lower frequencies normally are the critical ones.ISO 12494 pdf download.