How is wheel load distributed onto the plate elements. Can we consider the dispersion of the wheel loads. 

Answer:

The wheel load is transferred to nearby nodes in proportion to the distance of the load from the nodes and it applied as concentrated load there.  This can be checked quite easily by using the moving load tracer.  Just write the load to file and add this file as static load case to model using MCT command shell.  Kindly note that the model would have to be re-analyzed after doing that. Generally, dispersion is not considered for plate modelling.  If it is required, then the loads would have to be applied manually.

Let's say there is a quadrilateral plate element of the size 350 mm X 350 mm positioned with its center located 600 mm perpendicularly from and one of its edge parallel to the center line of the traffic lane. If the wheel spacing is 1000 mm with 4 wheels per axle, a wheel load will be 100 mm away from the plate center (measured in the direction perpendicular to the center line of the traffic lane).

However, the wheel area can’t be controlled.  The load is considered as a nodal load.  Kindly refer the image below for better understanding.  For simplification, I've considered a square plate mesh structure.

In the image above, W/2 is the wheel load located on any plate.  a, b, c, d, e, f and L are distances.  The wheel load is simply distributed following simple engineering mechanics formulation.  The 'X' mark shows the final load which is applied on the plate nodes representing the two-wheel loads.