Abstract: In the reliability estimation of large complex structures, response surface method (REM) has been widely suggested as a way to estimate failure probability of the actual but implicit limit state equation. Nevertheless, the precision of the RSM turns out to be subjected to further studies. The major factors which have significant effects on the precision of the RSM are analyzed, and they are the following four points: 1) Location of the sampling points used to determine the response surface; 2) Degree of the nonlinearity in the vicinity of the design point of the actual implicit limit state equation; 3) Approximate degree of the response surface matching the actual implicit limit state equation; 4) Coefficients of variation in the basic random variables. By taking these major factors into consideration, the paper devotes to research a combination response surfaces method. The main and multiple secondary response surfaces are combined to approximate the region which has great contribution to the failure probability of the large complex structure. Each response surface is corrected by the high order term of actual limit surface for more accurate result. The advantage in the precision of the presented method is verified by the illustrations.

Key words: structural reliability, improved response surface combination, nonlinear limiting state equation, high order term, ten-bar structure