Unit loads

Unit loads have meaning only for 3D structures where a motion of a loading vehicle acting in several tracks parallel with the axis of the mobile track can be modelled. For 2D structures, one unit load represented by a force Pz = -1.0 is predefined.

It is possible to set several unit loads for each track. Each impulse consists of unit loads and can be adjusted in away so that it represents a multi-track truck. The unit load can act in the direction of individual axes of the global coordinate system. It is for example possible to model a bridge by a small 2D system, but such a solution makes it impossible to define a system of wheel-pairs (one next to another) of trucks or trains in a way described in national standards.

It is possible to define a unit load that on a 3D structure acts in several tracks parallel to the defined mobile load track (unit load along the width of a bridge). Certain standards use also a distributed load to model the surface contact of wheels with the structure.