any and all EXPOSED metallic structural parts of the building. 411.3.1.2
for example i have known houses have a RSJ run through them which is above the ceiling and beneath the floor boards so it would not be classed as exposed so would not need bonding.
I fear this comes down to professional judgement. Depending on how the cables run in relation to the RSJ, then maybe, but generally, I'd say no. Do the cables pass through it in any way ?
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