Can we refer to bridge as unit like in this first sentence?

Question

-----------------
There is *one unit* of 30 m Bailey Bridge, which is considered to be incomplete, but can still be modified so that it can be used as a replacement for the bridge that is expected to be collapsed in this rainy season. This bridge can function as a support if placed on the site to replace the collapsed bridge.

Answer 1

No. I don't know exactly what you mean, could it be:

There is one bridge, 30-meter-long (or high?) Bailey Bridge, which is not finished but can still be modified to be used in place of the bridge that will probably collapse in the rainy season.

I took out some of your passive-voice sentences...I assume it's the rain that will collapse the bridge, not that people will do it deliberately.

I didn't change your second sentence, but I don't really understand "function as a support".