Short circuit force on support arms for cable ladder?

[PowerEng90]

In the case of a trefoil cable set cleated to a cable ladder. Is it necessary for the support arms of the cable ladder to be dimensioned for other mechanical forces than the weight of the equipment? The cable cleating is dimensioned to withstand the short circuit force between the cables (F’=0.17*ip^2/S). But I assume that this force are handled by the cable cleats, and not to be a dimensioning load for the support arms?

 

[7anoter4]

In my opinion no parallel conductors conveying opposite directions current may be in a short-circuit phase to ground so no short-circuit force exercising on the cable tray support is expected.
In our calculation we never take more than cable weight into consideration.