Harmonic (vibration) load is a load that changes periodically according to a certain law. Loads of this nature are created by rotational and rotational-translational motion of unbalanced parts of machines and mechanisms (electric motors, turbines, machine tools). Vibration loads are especially dangerous for structures, since the forces and displacements they cause depend not only on the magnitude(amplitude) of the load, but also to a large extend on the frequency of its action.
Impact load (impact at a certain point of the structure) is characterized by the fact that it is applied in a very short period of time with a sharp change the speed of the colliding bodies. It can be stationary and moving, chaotic (ice floe impacts) and periodic (mechanical black smith’s hammer).
Seismic load, which includes simultaneously impacts, shocks, and crustal shifts, is a great danger for engineering structures due to complexity of the dynamic load. A moving load- changing its position on the structure(trains, cars)-usually refers to complex dynamic effects that cause vibrations of the structure.
