There is C channel support frame of Mild Steel varying web and flange sizes and thickness corresponding the wight of pay load and also adding some additional strength for the factor of safety.
A semi end dump is a tractor-trailer combination wherein the trailer itself contains the hydraulic hoist. In the US a typical semi end dump has a 3-axle tractor pulling a 2-axle trailer with dual tires, in the EU trailers often have 3 axles and single tires.
A truck and pup are very similar to a transfer dump. It consists of a standard dump truck pulling a dump trailer. The pup trailer, unlike the transfer, has its own hydraulic ram and is capable of self-unloading.