Centre of area (centroid)
The centroid of a section is important in structural design and is like the centre of gravity of the shape. Most structural shapes have their centroid tabulated by the manufacturer. Many other simple shapes are symmetrical about the x-x and y-y axes and the centroid can easily be seen. Occasionally a structural shape is made up of more than one structural section. In these cases a calculation is needed to work out the position of the centroid so that further structural design and analysis can be carried out.