Apparently, the most efficient way to optimal design truss structures
is to consider all three optimization schemes simultaneously.
In the literatures two kinds of approaches [2,3] have been proposed
to solve such a problem. One is the singular stage method; all design
variables including topology, shape, and size are integrated
as one design variable. However, this method will be timeconsuming
since the search space is extremely large. Moreover,
simultaneous consideration of these variables makes the problem
very complex due to the natural character of mixed coding scheme
of continuous and discrete variables. The other approach is a kind of
double stage method; first, the topology of the structure is