An optimal design method combining the system simulation technology and the multi-object decision technology

which can be used for optimum design of piled rafts

is presented. The objective function for the optimization is defined as the volume of materials of piled rafts

while the variables are raft thickness

pile length

pile spacing and pile location. First using orthogonal test to optimize system input scheme

then applying 3DFEM to calculate system output

at last the multi-object decision technology is adopted to evaluate output and acquire optimal solution. The validity and effectiveness of the proposed method is examined by a numerical example.