A load may be defined as the combined effect of external forces acting on a body. The loads may be classified as:
- Dead loads
- Live or fluctuating loads
- Inertia loads or forces
- Centrifugal loads or forces.
The other way of classification is
- Tensile loads
- Compressive loads
- Torsional or twisting loads
- Bending loads
- Shearing loads
The load may also be a ‘point’ (or concentrated) or distributed.
A point load or concentrated load is one which is considered to act at a point. In actual practice, the load has to be distributed over a small area, because, such small knife-edge contacts are generally neither possible, nor desirable.
A distributed load is one which is distributed or spread in some manner over the length of the beam. If the spread is uniform. (i.e., at the uniform rate, say w kN or N/metre run) it is said to be uniformly distributed load and is abbreviated as u.d.l. If the spread is not at uniform rate, it is said to be non-uniformly distributed load. Triangulary and trapezoidally distributed loads fall under this category.