Why are Flatbeds arched?

So that when you load them they are flat and not swaybacked.

 

Also when I hauled steel we would have our trailers ordered with a extra high arch or re-arch them if the trailer was worth enough. This high arch served a very good purpose to us with sidekits...it helped hide how heavy we were. We could take a old all steel Transcraft flat and arch the heck out of it with heat and steel strapping. Once this was done we could easily load a 60,000 lbs. single coil on it and still look like the trailer was empty. I would hate to guess how many overweight tickets my Reitinour trailer got me out of.

 

The arch actually lets the trailer flex when fully loaded so that it won't break in half when you put a heavy load in the middle of it and go down a rough road.

 

The other day I was headed home throught MS and at one of the Pilots on
I55 there was a J H Walker flatbed with a coil on it that had broke.

The middle passenger side of the trailer was touching the ground, but the coil
never broke loose.

 

The same reason most bridges are arched- strength