No idea how this happens

Frameless dryvan's? Somehow I doubt that. The cross member's under the trailer and the skirt are the frame. A "frameless" trailer would be lucky to hold it's own weight not to mention the wind and weight of the tandems pulled and bounced around. If there is such a thing as a frameless dryvan then by all means humor me. No pun intended.

 

I wondered if I'd ever see that again.

Back in 05' I was doing a lot of relief loads to Louisiana after Katrina. The governor lifted all weight restrictions so many were hauling as much as they could get on. I pulled into a small truck stop somewhere down there.

There was a truck parked under the truck stop sign. But it had collapsed in the middle like that and the rear of the trailer had come up and smashed the sign. It was quite a sight. Apparently too much weight, a lot of water.

 

Frankly, the walls and roof are the "frame", just like in modern (post-60's) cars - cut the roof off, car splits on first hard bump.

 

My Wagon Ain't Saggin'!!!
Les2,
I guess if that was your wagon that buckled you couldn't use your signature any more! LOL