The structure are characterized by their support system. There are one dimensional, two dimensional and three dimension support system.

• One dimension support system: It can also be term as line supporting structure. Line supporting structure large in one dimension and small in other dimension.
• Two dimension supporting system- It can also be term as surface structure is large in two dimension and small in third diameter.
• Three dimension supporting system:-Three dimension structure are large in three dimension and these structure may have any shape
• ductility is unique property of steel by virtue of which it is able to deform substantially eighter in tension or compression before failure..

The structure are also be divided into following three categories

1. Skeletal structures.
2. stress skin structures
3. solid structure

The following are the common steel structure is used

1. Roof truss for factories, cinema hall, auditorium etc,
2. Roof truss and column to cover platform in railway stations,
3. Single layer and double layer domes for auditorium
4. Plate girder and truss bridge for railway & road.
5. Transmission towers and microwave and electric power.
6. Water tank

Mechnacial properties of steel structure

The mechnacial properties sheets depending upon the following factors

1. chemical composition
2. Rolling methods
3. Rolling thickness
4. Heat treatment
5. stress history