Civil Engineering Reference
In-Depth Information
For example, the co-ordinates of a point
(x, y)
in a quadrilateral can be
expressed in terms of the co-ordinates at the four nodes and the shape
functions as
(9.22)
in which the
N
s
are the shape functions given in terms of the natural co-
ordinates (ξ, η)) of the corresponding point in the parent square element.
(9.23)
If the same shape functions are used to relate the displacements
(9.24)
the quadrilateral element is called iso-parameteric.
As before, the strains are given by
(9.25)
with
(i=1,2,3,4)
(9.26)
