Analysis of the design principle of the structure of the trailer truck girder

The semitrailer beam is the main part of the semitrailer, and there are many longitudinal beams near the girder. The girders and auxiliary girders form the whole freight transport platform for the semi-trailer.
The beam consists of the upper and lower wing plates and the web.
The influence of girder strength is nothing more than the dimension of longitudinal beam section, but the influence degree of each dimension on longitudinal beam strength is different.

Basic dimensions: upper and lower wing width W=146mm, upper and lower wing plate thickness t1=t2=10mm, web t=5mm, girders height H=500mm
The strength of the web has a relatively small influence on the strength of the longitudinal beam. The web of 5mm's web is about 4.4% higher than that of the 4mm, but the normal web will not be too thin, because the high section plate will be flexed under the load and will be waved or side drums.
The strength of the upper wing plate 10mm is about 8% higher than that of 8mm. The cross section height of H has great influence on the strength of the beam. The strength of 500mm is about 14% higher than that of 450mm, and the anti deformation strength is about 27%; 450mm is about 16% higher than that of 400mm, and the anti deformation strength is about 30%; 400mm is about 18% higher than that of 350mm, and the anti deformation strength is about 35% high. We can see that the effect of each 50mm on the strength is increasing as the total height H decreases.
The following is a schematic diagram of the stress distribution of the longitudinal beam. The stress concentration area of the longitudinal beam is the gooseneck part, that is, the low strength and easy deformation position.  Therefore, the location of longitudinal girders and gooseneck is also a common reinforcing part.



It is said that the increase of the thickness of the web has little influence on the strength of the longitudinal beam, but the double web can effectively strengthen the torsion strength. In general, the double web will be used in the dump truck and the low flat gooseneck to increase the torsion resistance of the complex road conditions.
The strengthening of the lower wing plate is more effective to increase the bending strength and deformation resistance, because the lower wing reinforcement increases the thickness of the lower wing plate and increases the total height of the longitudinal beam.
Steel has the characteristics of compression and non tension, so many times the upper wing of the longitudinal beam will be thinner than the lower wing plate.
In addition: if the semi-trailer beam is not used in the manufacture and selection of materials, there will be broken beams and other traffic accidents. The characteristics of the beam are determined by the characteristics of the steel.
Common steel bar for trailer girder
Name
Common trailer beam steel
Name: general steel material manganese steel material high strength steel material special steel material
Model
Q235
Q345
T700
Select material according to the required
Yield strength
235Mpa
345Mpa
700Mpa
elongation
26%
22%
17%
Through comparison, it can be seen that the Q235 has to increase the thickness of steel to ensure the strength of the steel because of its low yield strength. It is mainly used in traditional large trailers and often back and forth transportation vehicles with bad road conditions. The performance of Q345 is comparatively moderate, it is suitable for general general model, the strength is slightly higher, and the weight of a part of the trailer can be reduced. The toughness can also ensure that the trailer can adapt to the general comprehensive road condition, and it is widely used. T700 has high strength and good welding performance, but it is strict in welding process. It can reduce the weight of the trailer to the maximum under the condition of guaranteeing the bearing strength. It is widely used in the lightweight dump truck frame and the girder abdomen.
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