one more question on bridge bearing

I agree, it is redundant. You could delete either "relative" or, "of each other":

(Bridge bearing is used)To isolate components or parts of a structure or assembly of parts when their movements must be independent of each other.

(Bridge bearing is used)To isolate components or parts of a structure or assembly of parts when their relative movements must be independent.

I believe that:"(Bridge bearing is used)To isolate components or parts of a structure or assembly of parts when their relative movements must be independent." is correct.

I believe that "relative" is more descriptive/important than, "of each other" in this case.

2.To provide release or sliding surfaces at bearing ends of structural members, thereby accommodating shrinkage or thermal motion of members.

which is what i said

and as the bearing is a sliding bearing with just the weight of the bridge keeping it there if the ground was to fall away as in a seismic event then the bridge would not be dragged with the ground.

in the UK rail bridges just sit on bearings and if hit hard enough by over height lorries trying to get under them the bridge part is sometimes moved