timbers near power cables on a bridge

[magoo2]

A highway bridge over a river with a movable center section has power cables running vertically down the outside of a caisson. On each side of the cables there's a section of timber, approximately 12"x12" cross section and about 10 feet long. These are bolted to the caisson. Since I don't see any other timbers round the caisson, I'm assuming their purpose is to protect the cables from a ship striking near the cables. Is that their intended purpose?

Someone also suggested that they are there to protect ships in case they impact the caisson. If that were the case, wouldn't you expect to see additional timbers?

There's similar construction at the other end of the cables on another caisson.

What does the AASHTO standards/specifications say about the purpose or need for these timbers?

Thanks in advance.

 

[bridgebuster]

They're not going to protect the ship - do you have a photo? - it could be a fender system to guide a vessel along the pier in the event of collision. 12 x 12's on the pier aren't going to protect the bridge either.

AASHTO Standard Specs don't cover vessel collisions; you'd have to go to the AASHTO Guide Specification for Vessel collisions. The LRFD spec has an extensive discussion.