Why do flatbed trailers arch?

so they sit flat when loaded.

 

I might be wrong, someone correct me if I am.
They are designed that way to be able to carry alot of weight while not using as much metal for the framework of the trailer. thus enabling a lighter trailer so they can carry that much more cargo.

 

Its for strength.

 

I think this is right...although Im not sure why, lol.

Basically...the slight arch is there to provide additional strength (the whole concept of the arch is that it provies strength). Plus, think of it as a bow or something...or a spring...when you add weight...it compresses the trailer down flat...giving it even more strength.

 

The arch is to provide strength to the trailer so you can load a lot of weight in a smaller area. For example, you can load a 48,000 pound coil in 5 feet of deck space.

 

Like a bridge or a rafter in a roof.

 

So it doesn't sag when loaded or bounced, which would bang the freight together (pinch the gaps closed at the top) if it was separate pieces?