Structural elements are elements that are used in structural analysis to break a complex structure into simple elements. We cannot decompose the elements into different kinds within the structure.Structure elements may be linear, volumes or surfaces. We can categories linear elements as;

Beam
Rod
Ties or tie rods
Compression member
We can categories volumes as;
Shear and bending loads for 3D and axial.
We can categories surfaces as;
Shell
Membrane
Deck
Concrete slab
Deck
Shear panel
Essentially all structures are made up of small number of different elements :
Beams
Columns
Arches
Plates
Catenaries
Shells

Beams:-Bbeam is an element in which one dimension is much greater than 2D or 3D, normal to the main axis of the element. Beams come under line element and often represented by simple line in structural modeling.

1. Cantilevered:It is a structure which is supported at one end only with a fixed connection.
2. Simply supported:It is a structure supported vertically at all the ends horizontally on only one to withstand friction, so that it will be able to rotate at its supports.
3. Continuous:It is supported by three or more supports.
4. A combination of the above is supported at one end and in the middle.
Beams carry pure bending only. Due to bending one part of beam go into compression and the other part of the beam go into tension.

Columns:-Columns carry only axial force, i.e. either compression or tension or both axial force and bending which is called beam column. The design of the column is necessary to check axial capacity and buckling capacity. Buckling capacity of an element implies propensity to buckle. Buckling capacity depends upon its effective length of column and the geometry.

Arches:-Arches apply forces in compression in one direction only. This is why it is appropriate to build arches. They are designed in such a way that the line of thrust lies within the arch.

Plates:- Plates bends in two directions. Plates are understood by using continuum mechanics but because of complexity in it they are frequently designed using a codified empirical approach. E.g. concrete flat slab.

Catenaries:- Catenaries carry transverse forces in pure tension. Catenaries are always fabric or cable structure.

Shells:-Shell carries forces in compression in two directions. E.g. dome.Shells can be designed by making a hanging-chain model. Shells as a centenary in pure tension and invert the form to achieve pure compression.