The theorems of structural variation predict the forces and displaceme
nts throughout a structure without need of fresh analysis when the phy
sical properties of one or more of its elements are altered. It has be
en shown, that by means of these theorems, the elastic, non-linear ela
stic and elastic-plastic analysis of number of related frame structure
s can be obtained from the simple elastic analysis of a parent structu
re. They are later extended to cover the triangular and quadrilateral
finite element structures. In this paper, it is shown that these theor
ems can also be applied to three-dimensional finite element structures
. For this purpose, eight noded solid cubic element structures are con
sidered. The unit loading cases required to study the modification of
a single element are derived. They are later used to obtain the variat
ion factors. These factors are utilized to predict the behavior of a c
ubic element structure when one or more of its element are modified or
totally removed. It is verified that the accuracy of the results is t
he same as the original finite element discritization of the parent st
ructure. (C) 1998 Elsevier Science Ltd and Civil-Comp Ltd. All rights
reserved.