The upper wing surfaces of the straight beam frame rails are all straight. The advantages are that the bottom plate of the trailer bed is flat, the manufacturing process is simple, the ground clearance is generally high, and the longitudinal passability is good. Heavy-duty flatbed flatbed trailers are designed to meet their structural and usage requirements. The frame is mainly composed of main beam, cross beam, support beam and side beam. The load of the whole vehicle is transmitted to the ground through the support beams, suspensions, wheel axles and wheels between the beams. The main beam, support beam and side beam of the frame are welded parts with box-shaped section and have large torsional rigidity. The beam connecting the main beam extends to both sides and is an I-shaped welded structure with variable cross-section, which has high transverse bending strength. The height of the main beam of the frame is relatively large and extends downward, so that the longitudinal bending strength of the frame is improved without increasing the height of the cargo bed. A turntable mechanism for installing a balance suspension is arranged under each support beam to realize all-wheel steering. The goods shipped by heavy-duty flatbed trailers have large quality and large dimensions. Generally speaking, the strength of the frame should be increased, and the height of the frame should be reduced as much as possible to facilitate the loading, unloading and transportation of goods.

The frame of the flatbed trailer includes a straight-through frame, a stepped frame and a concave beam frame according to the structure of the longitudinal beam.