jeff m:

Go to any major heavy towing firm, any major trailer leasing company or any major trucking company and they should have numerous pictures of truck trailer failure including roof collapse, sidewall tearing, floor unzipping and other damage. Most of these failures occurred because of what many would consider minor defects.

Most dry van and reefer type trailers in use today in the U.S. and Canada are of a monocoque construction. The trailer is basically a unitized body and the floor is supported similar to a suspension type bridge. There are no support beams running the longitudinal length of these trailers. The only beams are those that attach the suspension (wheel components) to the trailer.

These unitized trailers are prone to catastrophic failure and do require special inspection. The potential hazards to the forklift operator, other employees, as well as the general public should a trailer fail are much greater than OSHA and other safety organizations recognize or are willing to admit.

Google: monocoque trailer technical information bulletin transportation.centennialcollege.ca

Google: OSHA Technical Bulletin Inspection of Suspension-Type Highway Trailers Prior to Loading and Unloading with Powered Industrial Trucks

The information on the above sites should be identical with the exception of the trailer illustration in the Centennial College site.

It should also be noted that the DOT highway underride guard/rear impact guard on these trailers are prone to failure. Do not drive behind these trailers on the road unless you can absolutely, under all circumstances, stop safely. If you cannot stop safely the back end of the trailer could be coming through your windshield.