Each building is somehow burdened, either by its weight or by what we have burdened it with or otherwise. What yo is a load, how do you define, classify and name it? The simplest way to say it is that the load on the object is the system of forces acting on it.
By definition: “Load is a physical action that causes a change in the state of the structure by creating stresses, deformations or displacements.” 
There are many ways to share the burden; the basic division is:
- static loads, the size of which increases progressively from zero to the maximum size (example: load on the foundation slab through the masonry wall placed on it);
- dynamic loads act suddenly and quickly, and their value is variable in time (load on the overpass by a car passing through it).
In the construction industry, the duration of certain loads is very important.
Therefore a different division was introduced:
- fixed loads, which during the erection and use of the object have a constant value, unchanging direction and places of application. Example: the own weight of elements or soil in its native state;
- Variable loads, whose value, direction and place of application can vary over time. Variable loads act periodically.
We distinguish between them:
a) Technically variable loads – they depend on the function and use of the object, e.g. weight of heating devices;
b) environmental variable loads – depend on the environmental conditions prevailing in the area of the erected object (snowfall, winds);
3) exceptional loads are unlikely, difficult to predict, such as, e.g. impact of a vehicle on the building column, fire or hurricane.
One more distribution of variable loads may be important:
(a) Variable loads that are entirely long-term, such as
– The own weight of those devices that are permanently attached to the building, such as lifting devices or heating boilers;
– the temperature load created by the equipment.
(b) Variable loads in the long term, e.g.:
– weight resulting from storage;
– the weight of equipment and materials, but also the weight of people.
c) Variable loads in the entire short term, e.g.:
All buildings are subject to several types of the load simultaneously. Their analysis should be considered in several variants, taking into account different combinations. The most important for us will be the most unfavourable ones.