
Adaptive analysis 265
number of total eld nodes (newly created plus already existing) exceeds
the number of total virtual nodes during the adaptive renement, depend-
ing on the difference between the number of total virtual and eld nodes,
only one or two new eld nodes instead of four are created around only
those eld nodes having the values of absolute local gradient F
i1
more
than a certain cut-off value. This precaution is necessary to ensure that the
total eld nodes are always fewer than or equal to the total virtual nodes to
avoid rank deciency in the nal stiffness matrix.
Instead of uniformly distributing the newly generated eld ...